Title of Invention

METHOD AND APPARATUS FOR PRODUCING OPTICAL RECORDING MEDIUM

Abstract Disclosed are a method and apparatus for producing an optical recording medium which comprises an intermediate layer having a good corrugated surface and only few defects at low cost. Specifically, a recording layer is formed on a substrate directly or via another layer, and a resin material layer is formed on the recording layer directly or via another layer. Then a stamper, which has a corrugated pattern for transfer corresponding to the corrugated surface to be formed, is placed on the resin material layer, and a bonded body is obtained by curing the resin material layer. After that, the stamper is separated from the resin material layer while heating the bonded body, thereby forming the resin material layer into an intermediate layer having a transferred corrugated pattern.
Full Text FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
"METHOD AND APPRATUS FOR PRODUCING OPTICAL
RECORDING MEDIUM"
Mitsubishi Kagaku Media Co., Ltd.
a Japanese Corporation, of 31-19, Shiba 5-chome Minato-ku, Tokyo, 108-0014 Japan
The following specification particularly describes the invention and the manner in which it is to be performed.

-SPECIFICATION –
METHOD AND APPARATUS FUR PRODUCING OPTICAL RECORDING MEDIUM
Technical Field [0001]
The present invention relates to a method for producing an optical recording medium. In particular, the present invention relates to technology that can produce an optical recording medium having excellent recording characteristics at low costs.
Background of the Related Art [0002]
In recent years, in order to record and playback a large volume of data including high-quality moving images for a prolonged time, development of optical recording medium that can
store information at a higher recording density than that of conventional optical recording media has been awaited. Such optical recording media that can store information at high density include, for example, multilayer optical recording medium such as dual-layer DVD-ROMs having two recording layers
in a single medium. Such multilayer technologies can be used to increase storage capacity without any change in recording density of each layer.
[0003]
In general, multilayer optical recording medium is prepared
by a photo-polymerization process (hereinafter referred to as 2P process). In the 2P process, for example, a first recording layer, a first reflective layer, an interlayer having an uneven


pattern for recording tracks, a second recording layer, and a second reflective layer are laminated in sequence on a transparent first substrate having an uneven pattern for recording tracks. A second substrate is then bonded onto the second reflective layer to prepare an optical recording medium having a dual-layer structure. [0004]
In the 2P process, the interlayer is usually prepared by the following steps. A photo-curable resin material that can be
cured by light (examples of such light include radiation rays such as UV rays) is applied onto the first reflective layer to form a resin material layer. A stamper having an uneven pattern to be transferred (hereinafter referred to as uneven transfer pattern) is then placed on the resin material layer. After the
photo-curable resin material is cured, the stamper is detached. Through these steps, the uneven pattern of the stamper is transferred on the surface of the photo-curable resin. Hence, the interlayer formed of the cured resin has a transferred uneven pattern.
[0005]
Therefore, in the 2P process, it is desirable to detach the stamper smoothly after the photo-curable resin is cured. During the formation of an interlayer having an uneven pattern for recording tracks by the 2P process, production problems, such as
difficulty in detachment of the stamper from the photo-curable
resin and low uniformity of the surface of the interlayer caused by the detachment, may lead to defects on the interlayer, such


as scratches and flaking. As a result, optical recording medium
cannot properly record and playback optical information.
[0006]
Unfortunately, a stamper composed of a polycarbonate resin or an acrylic resin cannot be readily detached from an
interlayer composed of a UV-curable resin (see Patent Documents 1 and 2). Patent Documents 2 and 3 discloses techniques for smooth separation of stampers, accordingly.
[0007]
Patent Document 2 discloses a method for coating the surface of a stamper composed of an acrylic resin using an inorganic material. Such a method facilitates separation of the stamper. This document also discloses an acrylic stamper having grooves or pits (corresponding to an uneven transfer pattern)
covered by a SiO2 dielectric layer. [0008]
Patent Document 3 discloses a stamper composed entirely of a cyclic polyolefin or polystyrene resin or a stamper having a surface with a mother pattern (corresponding to an uneven
transfer pattern) that is composed of a cyclic polyolefin or a polystyrene resin. This document discloses that such a stamper can be readily detached from an interlayer composed of a radiation-cured resin. This document also discloses that the cyclic polyolefin significantly improves detachment of the
stamper from the interlayer composed of the radiation-cured resin. [0009]

[Patent Document 1] WO 2005/048253 (paragraph [0100]) [Patent Document 2] Japanese Unexamined Patent Application
Publication No. 2002-279707 (paragraphs [0021] and [0028])
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2003-85839 (paragraphs [0006], [0016], and
[0046] to [0055])
Disclosure of the Invention
[Problems to be solved by the Invention]
[0010] As in the method disclosed in Patent Document 2, the following step is required to pre-coat the surface of the stamper used in the 2P process with a transparent inorganic material.
Grooves or information pits formed on the surface of the stamper
are covered by a dielectric layer composed of an inorganic material such as Si02 with a predetermined thickness in a vacuum
sputtering apparatus. However, this step complicates the
production process of optical recording media, resulting in an
increase in production cost.
[0011] While cyclic polyolefins disclosed in Patent Document 3 are industrially excellent materials having excellent detaching
characteristics, these cyclic polyolefins are expensive special
materials, which increase the production cost of stampers.
Since resin stampers are generally disposable, the cost of stampers occupies a significantly large fraction of the total
cost for the production of optical recording media, as it stands.
[0012]


In addition, higher performance and lower cost are now required for multilayer optical recording media.
Under these backgrounds, development of a method for producing optical recording medium using stampers which are made from inexpensive resins such as polycarbonate resins or acrylic resins and can be readily detached is awaited.
The present invention has been accomplished to solve these problems. An object of the present invention is to produce an optical recording medium including an interlayer having an excellent uneven pattern with few defects at low costs. [Means for Solving the Problems]
[0013]
The present inventors have extensively investigated in order to overcome the above-described problems and have discovered a method of detaching a stamper at a heated state from a resin material layer in the 2P production process of an optical recording medium. The inventors have also discovered that this approach can produce an interlayer having an excellent uneven pattern even when the stamper is formed of a polycarbonate resin that was not able to be used in conventional stampers. The inventors have further found that this approach ensures satisfactory detachment of a stamper formed of a cyclic polyolefin that was known as a material having excellent detaching characteristics.
[0014]
An object of the present invention is to provide a method for producing an optical recording medium including a substrate,

a recording layer, and an interlayer having an uneven pattern, the method comprising forming the recording layer on the substrate directly or with an underlying layer; forming a resin material layer on the recording layer directly or with another underlying layer; placing a stamper having an uneven transfer pattern corresponding to the uneven pattern on the resin material layer and curing the resin material layer to form a bonded body including the substrate, the recording layer, the resin material layer, and the stamper; and detaching the stamper
from the bonded body, whereby the uneven transfer pattern is
transferred to the resin material layer to form the interlayer, wherein the stamper is detached from the bonded body in a heated state (Claim 1).
[0015]
The temperature of the bonded body during the detachment of the stamper is preferably 50°C or more (Claim 2).
[0016]
The temperature of the bonded body during the detachment of the stamper is preferably not higher than the glass transition
temperature of the stamper (Claim 3). [0017]
In the case where the resin material layer includes a plurality of resin sublayers and the outermost sublayer among the plurality of resin sublayers is in contact with the stamper,
and the temperature of the bonded body during the detachment of the stamper is preferably not higher than the glass transition


temperature of the stamper and the glass transition temperature
of the cured outermost resin layer (Claim 4).
[0018]
The stamper preferably comprises a polycarbonate resin 5 (Claim 5).
[0019]
The resin material layer preferably comprises a radiation-curable resin (Claim 6).
[0020] The optical recording medium is preferably a multilayer optical recording medium having two or more recording layers (Claim 7).
[0021]
Another object of the present invention is to provide an apparatus for producing an optical recording medium including a substrate, a recording layer, and an interlayer having an uneven pattern, the apparatus including means for forming the recording layer on the substrate directly or with another underlying layer; means for forming a resin material layer on the recording layer directly or with another underlying layer; means for placing a stamper having an uneven transfer pattern corresponding to the uneven pattern on the resin material layer and curing the resin material layer to form a bonded body including the substrate, the recording layer, the resin material layer, and the stamper and means for detaching the stamper from the bonded body, whereby the uneven transfer pattern is transferred to the resin material layer to form the interlayer,


wherein the means for detaching the stamper detaches the stamper
from the bonded body in a heated state (Claim 8).
[0022]
In the present invention, the stamper can be readily detached in a heated state, whereby the interlayer produced has
an excellent uneven pattern. Although the detailed mechanism is
unknown, the following reasons (i) to (iv) are possible.
(i) First, when the bonded body is heated to high temperature,
the elastic modulus of the material decreases in the surface region of the resin material layer on which the stamper is
placed. Since the material in the surface region becomes
softened, the stamper can be readily detached.
[0023]
(ii) Second, when the bonded body is heated to high temperature, the chemical activity of the material decreases in the surface
region of the resin material layer on which the stamper is
placed, whereby the stamper can be readily detached. In general,
it is believed that the resin material layer and the stamper are
intermolecularly bonded at the interface between these components. This intermolecular bonding force is weakened when
the bonded body is heated to high temperature, whereby the
stamper can be readily detached.
[0024]
(iii) Third, when the bonded body is heated to high temperature, the molecular motion is accelerated in the surface regions of
the resin material layer and the stamper. Since the surface


free energy of these components is reduced (that is, the surface tension is decreased), the stamper can be readily detached. [0025]
(iv) In the case where the resin material layer heated after curing, i.e., in the case where the temperature of the bonded body varies after curing of the curable resin layer, the following reason is also attributed to one factor of the improved detachment. Since the rate of thermal shrinkage or expansion of the material of the stamper is different from the
rate of the thermal shrinkage or expansion of the material in the surface region of the resin material layer on which the stamper is placed, the materials shrink or expand at the time of increasing the temperature of the bonded body by heating. This generates stress required for the easy detachment of the stamper
from the resin material layer in the inside of the bonded body, whereby the stamper can be readily detached. Advantages of the Invention
[0026]
According to the method for producing an optical recording
medium and the apparatus for producing the optical recording medium of the present invention, an optical recording medium including an interlayer having an excellent uneven pattern with few defects can be produced at low costs. Brief Description of the Drawings
[0027]
[Fig. 1] Figs. 1(a) to 1(g) are schematic views illustrating a preferred method for producing an optical

recording medium in accordance with a first embodiment of the present invention.
[Fig. 2] Figs. 2(a) and 2(b) are schematic views illustrating a step of forming a resin material layer in a method for producing an optical recording medium in accordance with a second embodiment of the present invention.
[Fig. 3] Fig. 3 is a schematic view illustrating a step of curing the resin material layer in the method for producing the optical recording medium in accordance with the second embodiment of the present invention.
[Fig. 4] Fig. 4 is a block diagram schematically illustrating a production apparatus for the optical recording medium in accordance with the first and the second embodiments of the present invention.
[Description of the Numerals]
[0028]
1 production apparatus
2 first recording layer forming device
3 first reflective layer forming device 4 resin material layer forming device

5 resin material layer curing device
6 stamper detaching device
7 second recording layer forming device
8 second reflective layer forming device 25 9 second substrate forming device
10 carrying means
100 optical recording medium

101 first substrate
102 first recording layer
103 first reflective layer
104 interlayer
104 a resin material layer (UV-curable resin material layer) 104 a first resin layer 104a2 second resin layer (outermost resin layer)
105 second recording layer
106 second reflective layer 107 adhesive layer

108 second substrate
109 laser beam
110 stamper
111 data substrate
112, 112' bonded body
113 optical recording medium laminate Description of the Preferred Embodiments [0029]
Hereinafter, embodiments of the present invention will now be described in detail. However, the present invention should not be limited to the following embodiments, but can also be applied to various modifications of the subject matter of the present invention.
[0030] [I. First Embodiment]
Figs. 1(a) to 1(g) are schematic views illustrating a preferred method for producing an optical recording medium in

accordance with a first embodiment of the present invention. Figs. 1(a) to 1(g) show a method for producing a single-sided dual-layer optical recording medium (single-sided dual-layer DVD-R or single-sided dual-layer recoveradable DVD) having two recording layers containing an organic dye, as an example of a method for producing a multilayer optical recording medium. [0031]
The configuration of an optical recording medium to be produced in this embodiment will be briefly explained. As shown
in Fig. 1(g), a single-sided dual-layer optical recording medium 100 represented by a single-sided dual-layer DVD-R includes a disk-shaped light-transmitting first substrate 101 and has a structure in which a first recording layer 102 containing a dye, a translucent first reflective layer 103, a light-transmitting
interlayer 104 composed of a UV-cured resin, a second recording layer 105 containing a dye, a second reflective layer 106, an adhesive layer 107, and a second substrate 108 which is the outermost layer are laminated in sequence on the first substrate 101.
[0032]
Uneven patterns are formed on the first substrate 101 and the interlayer 104, respectively. These uneven patterns define recording tracks. That is, uneven patterns formed on the surfaces of the first substrate 101 and the interlayer 104 (that
is, the aforementioned uneven patterns) are in the form of recording tracks.


Recording and playback of the optical information on the optical recording medium 100 are performed by irradiating the first recording layer 102 and the second recording layer 105 with a laser beam 109 through the first substrate 101. That is, the first recording layer 102 and the second recording layer 105 record and playback information by irradiation with the laser beam 109.
[0033]
In a method for producing an optical recording medium in
accordance with this embodiment, "optical transparency or
transparence" means optical transparency in the wavelength range of light used for recording and playback of the optical information. Specifically, optical transparency means a transparency of generally 30% or more, preferably 50% or more,
and more preferably 60% or more in the wavelength range of light for recording and playback. The transparency in the wavelength range of light for recording and playback is ideally 100%, but in general 99.9% or less.
[0034]
A method for producing an optical recording medium of this embodiment will now be described.
The method for producing an optical recording medium of this embodiment includes a step of forming a first recording layer; a step of forming a first reflective layer; a step of
forming a resin material layer; a step of curing a resin
material layer; a step of detaching a stamper; a step of forming


a second recording layer; a step of forming a second reflective layer; and a step of forming a second substrate.
[0035]
[1. Preparation of Substrate] A first substrate 101 is prepared. As shown in Fig. 1(a), the first substrate 101 having an uneven pattern including grooves, lands, and pre-pits formed on its surface is prepared. The first substrate 101 can be prepared by injection molding using, for example, a nickel stamper.
[0036]
[2. First Recording Layer Forming Step]
In a subsequent first recording layer forming step, the first recording layer 102 is formed on the first substrate 101. Any method for forming the first recording layer 102 may be used
without limitation, and the following method may be used, for
instance. That is, a coating solution containing an organic dye is applied onto a surface having the uneven pattern of the first substrate 101 by spin coating. Thereafter, heating is performed to remove a solvent contained in the coating solution to form
the first recording layer 102. While this embodiment describes direct formation of the first recording layer 102 on the first substrate 101 as an example, the first recording layer 102 may also be formed on the first substrate 101 together with an underlying layer, depending on the type or the configuration of
the optical recording medium 100.
[0037]
[3. First Reflective Layer Forming Step]

After the first recording layer 102 is formed, the first reflective layer 103 is formed on the first recording layer 102, in the step of forming a first reflective layer. Any method may be employed for forming the first reflective layer 103 without limitation. For example, the first reflective layer 103 may be formed on the first recording layer 102 by sputtering or vapor deposition of an Ag alloy on the first recording layer 102.
As described above, a data substrate 111 is prepared by sequentially laminating the first recording layer 102 and the
first reflective layer 103 on the first substrate 101. In this embodiment, the data substrate 111 is transparent.
[0038] [4. Resin Material Layer Forming Step]
Next, in the step of forming a resin material layer, the
resin material layer is formed on the entire surface of the first reflective layer 103 (that is, the surface of the data substrate 111) as shown in Fig. 1(b). That is, the resin material layer 104a is formed on the first reflective layer 103 on the first recording layer 102.
The resin material layer 104a formed herein functions as an interlayer 104 at the completion of the optical recording medium 100, and is formed of a hardening resin curable by any treatment or its precursor.
[0039]
Any process may be employed for forming the resin material layer 104a without limitation. In general, the resin material layer 104a is formed in the following process.


Any hardening resin that can be used for an optical recording medium can be used. Examples of such hardening resins include radiation-curable resins and thermosetting resins. In the case of the resin material layer 104a formed of a thermoplastic resin or a thermosetting resin, a coating solution in which the thermosetting resin is dissolved in an appropriate solvent is usually applied. The resin material layer 104a is then dried (heated) to form the interlayer 104. In the case of the resin material layer 104a formed of a radiation-curable
resin, in general, the radiation-curable resin is used without dilution or as a coating solution in which the radiation-curable resin is dissolved in an appropriate solvent. The resin material layer 104a is then cured by irradiation with appropriate radiation rays to form the interlayer 104. Among
these preferred are UV-curable resins, which belong to the radiation-curable resins. Throughout the specification, "radiation rays" include electron beams, UV rays, visible light, and infrared light. The hardening resins may be used alone or in combination of two or more in any ratio.
Since the uneven pattern is subsequently formed on the surface of the resin material layer 104a with a stamper 110 (described below), the resin material layer 104a is in an unstable state (in general, in a liquid state with a predetermined viscosity) before the step of curing the resin
material layer. [0040]


Any method may be employed for forming the resin material layer 104a without limitation. Examples of such methods include coating processes such as spin coating and casting. Among these preferred is spin coating. In particular, when a high-viscosity resin is used, it can also be applied by screen printing. When the spin coating method is used, for example, the resin material layer 104a can be formed by applying a precursor of the hardening resin by spin coating.
In this embodiment, the precursor of the UV-curable resin,
which is one of the radiation-curable resins, is applied by spin coating to form the resin material layer 104a (hereinafter referred to as a UV-curable resin material layer for convenience in explanation).
[0041]
While this embodiment describes formation of the UV-curable resin material layer 104a on the first reflective layer 103 on the first recording layer 102 as an example, the UV-curable resin material layer 104a may be formed on the first recording layer 102 directly or together with any underlying layer other
than the first reflective layer 103, depending on the type or the configuration of the optical recording medium 100.
[0042]
[5. Resin Material Layer Forming Step]
In a subsequent resin material layer forming step, the
stamper 110 is placed on the UV-curable resin material layer
104a, and the UV-curable resin material layer 104a is then cured, as shown in Fig. 1(c). In other words, the stamper 110 is

placed on the surface of the UV-curable resin material layer
104a which is disposed opposite to the first recording layer 102.
The stamper 110 is a mold having an uneven pattern (uneven transfer pattern) on its surface corresponding to the uneven pattern on the interlayer 104. The uneven transfer pattern on the stamper 110 is transferred onto the UV-curable resin material layer 104a to form a desired uneven pattern on the interlayer 104. [0043]
In general, resin materials may be used for the stamper 110 in consideration of the production cost of the optical recording medium 100. As described below, the UV-curable resin material layer 104a is preferably cured by UV light through the stamper 110. Therefore, if the stamper 110 is composed of an opaque
material such as metal, UV light cannot pass through the stamper 110. As a result, the resin material layer cannot be sufficiently cured by irradiation with UV light, which may cause adverse effects such as deterioration of each layer. [0044]
As described below, in the present invention, the stamper 110 is detached in a heated environment. This has an advantage in that the range of material selection for the stamper 110 can be significantly expanded. In view of reducing the surface energy of the formed stamper 110, it had been believed that the
preferred resins for forming the stamper 110 would be polyolefin resins and polystyrene resins. Amorphous cyclic polyolefin resins (for example, ZEONEX® and ZEONOR® produced by ZEON

Corporation) have been used. In the present invention, however, general-purpose low-cost resins such as polycarbonate resins and acrylic resins can also be used, in addition to these highly functional resins. Materials for the stamper 110 are preferably polycarbonate resins and acrylic resins from the viewpoint of ensuring such an advantage. More preferred are polycarbonate resins. Materials for the stamper 110 can be used alone or in any combination of two or more in any ratio.
[0045]
In general, the stamper 110 is a disk stamper having a central through hole formed in the center. Also, in this embodiment, the stamper 110 having an uneven transfer pattern on its surface is a disk stamper having a central hole (not shown) in the center.
[0046]
Any method may be employed for producing the stamper 110 without limitation. For example, when the stamper 110 is a resin stamper, the stamper 110 can be produced by injection molding using a metal stamper (for example, a nickel stamper)
having an inversed (negative) uneven pattern of an uneven transfer pattern to be formed on the stamper 110.
[0047]
The stamper 110 used in this embodiment generally has a desirable thickness of 0.3 mm or more to enhance the shape
stability and to facilitate handling of the stamper 110 with the proviso that its thickness is usually mm or less. A stamper 110 having a thickness within the range has a sufficient optical

transparency. As described below, the UV-curable resin can be efficiently cured by irradiation with UV light through the stamper 110, thereby increasing in productivity.
[0048] The outer diameter of the stamper 110 is preferably larger than that of the first substrate 101 (in general, equal to the outer diameter of the optical recording medium 100) . A design such that the outer diameter of the stamper 110 is larger than that of the first substrate 101 facilitates formation of an
uneven transfer pattern at the outer peripheral portion, which lies outside the outer diameter of the first substrate 101, with a sufficient margin in the production of the stamper 110 by injection molding. An excellent uneven transfer pattern can be formed on the entire surface of the stamper 110 as a result.
[0049]
An outer diameter of the stamper 110 larger than that of the first substrate 101 also indicates an outer diameter of the stamper 110 larger than that of the interlayer 104 (and that of the UV-curable resin material layer 104a). This facilitates
formation of the edge of the interlayer 104. In other words, if the outer diameter of the stamper 110 is not larger than that of the first substrate 101, the resin of the UV-curable resin material layer 104a may adhere to the peripheral edge of the stamper 110 after the stamper 110 is placed on the UV-curable
resin material layer 104a. This resin may form burrs during the detaching operation of the stamper 110. The outer diameter of the stamper. 110 is larger than that of the interlayer 104 (UV-


curable resin material layer 104a), thereby the resin, which tends to form burrs and is present at the edge of the UV-curable resin material layer 104a, lies outside the outer diameter of the interlayer 104. Consequently, regardless of formation of burrs, the edge of the interlayer 104 can be satisfactorily formed by removing the burrs.
[0050]
In a preferred embodiment, the outer diameter of the stamper 110 is usually at least 1 mm and preferably at least 2
mm larger than that of the first substrate 101. On the other hand, the outer diameter of the stamper 110 is usually at most 15 mm and preferably at most 10 mm larger than that of the first substrate 101.
[0051]
The stamper 110 is placed such that its surface having an uneven pattern is urged against the UV-curable resin material layer 104a. The urging force of the stamper 110 against the UV-curable resin material layer 104a is adjusted such that the UV-curable resin material layer 104a has a predetermined range of
film thickness. [0052]
After the stamper 110 is placed on the UV-curable resin material layer 104a, the UV-curable resin material layer 104a is cured. In order to cure the UV-curable resin material layer
104a, the UV-curable resin material layer 104a may be irradiated with UV light. Any method may be employed for the irradiation with UV light without limitation. The UV-curable resin material

layer 104a may be irradiated with UV light through the stamper
110, through the side face of the UV-curable resin material
layer 104a, or through the first substrate 101. In the
irradiation with UV light through the stamper 110, the stamper 110 that can transmit UV light (that is optically transparent)
is industrially preferable. In the irradiation with UV light
through the first substrate 101, preferably the first recording
layer 102 should not be damaged by irradiation with UV light.
In view of the radiation efficiency with UV light and less adverse effects of UV light on the material of each layer, the
irradiation with UV light through the stamper 110 is preferred.
[0053]
In the description of this embodiment, the UV-curable resin
material layer 104a is irradiated with UV light through the 15 stamper 110, whereby the UV-curable resin material layer 104a is
cured by polymerization of a precursor of the UV-curable resin. The resin material layer 104a is cured in such a way to
prepare a bonded body 112 including the data substrate 111 (that
is, the first substrate 101, the first recording layer 102, and the first reflective layer 103), the UV-curable resin material
layer 104a, and the stamper 110.
[0054]
[6. Stamper Detaching Step]
In the step of detaching a stamper, as shown in Fig. 1(d), the stamper 110 is detached from the UV-curable resin material
layer 104a (see Fig. 1(c)) (that is, from the bonded body 112).
The uneven transfer pattern on the stamper 110 is transferred to

the UV-curable resin material layer 104a to form the interlayer 104. Throughout the specification, the UV-curable resin material layer 104a means the cured coating layer before the stamper is detached. The interlayer 104 means the layer after the stamper 110 is detached. Hence, the UV-curable resin material layer 104a and the interlayer 104 indicate the same layer that is formed at the same position but in a different state.
[0055]
Actual processes for detaching the stamper 110 are not limited. In a disk optical recording medium, a detaching process is generally as follows: The inner periphery of the optical recording medium is picked up by vacuum. A knife edge is then inserted into the inner periphery of the optical
recording medium. The stamper 110 is detached from the disk (hereinafter referred to as optical recording medium laminate 113) while air is blown into the inner periphery of the optical recording medium.
[0056]
In the method for producing an optical recording medium of the first embodiment of the present invention, the stamper 110 is detached while the bonded body 112 is in a heated state. The heated stamper 110 can be readily detached, resulting in preparation of an excellent uneven pattern on the interlayer 104. [0057]
The reason why detaching of the stamper in a heated state facilitates detachment of the stamper 110 and preparation of the

interlayer 104 having an excellent uneven pattern is yet unknown. As described above, the possible reasons are: (i) a decrease in the elastic modulus of the surface of the UV-curable resin material layer 104a in a heated environment; (ii) a decrease in the chemical activity of the UV-curable resin material layer 104a and the stamper 110 in a heated environment; (iii) a reduction in the surface free energy in a heated environment; and (iv) a difference in the rate of the thermal shrinkage or expansion between the material of the UV-curable resin layer
104a and the material of the stamper 110. It is believed that the above-described advantage may be obtained by these reasons. [0058]
The heating operation can be performed at any time for detaching the stamper 110 within a predetermined heating
temperature range of the bonded body 112. That is, in the
present invention, "heated state" does not always mean a heating operation but means a state to maintain a predetermined position at a higher temperature than room temperature described below. For example, by holding the production line at high temperatures,
the entire steps of the method for producing the optical
recording medium of the present invention may be performed in a heated environment. For example, the heating operation may also be performed in any of the steps before the step of detaching the stamper. Alternatively, the heating operation may be
performed in the step of detaching the stamper after the UV-curable resin material layer 104a is cured. Among these preferred is performing the heating operation in the step of

detaching the stamper. As described above, the utilization of the difference of the rate of the thermal shrinkage or expansion between the UV-curable resin layer 104a and the stamper 110 facilitates the detachment of the stamper 110.
[0059]
The heating operation can be performed once or more. During the heating operation, the temperature can be changed within the scope of the present invention.
[0060]
The temperature of the bonded body 112 (heating
temperature) during the detachment of the stamper 110 is not limited as long as the stamper can be readily detached. In general, the heating temperature is higher than room temperature (generally 25°C ± 5°C in Japan). In particular, the bonded body
112 is detached while the temperature of the bonded body 112 is
usually maintained at 50°C or more and preferably at 70°C or more.
[0061]
The upper limit of the heating temperature is preferably not higher than the glass transition temperature of the cured
interlayer 104, i.e., the cured resin material layer 104a (in
this embodiment, UV-curable resin material layer). When a resin stamper 110 is used, the upper limit of the heating temperature is preferably not higher than the glass transition temperature of the stamper 110. The upper limit of the heating temperature
is preferably not higher than the glass transition temperature of the cured resin material layer 104a and that of the stamper 110, in order to form an excellent uneven pattern on the surface

of the interlayer 104 in consideration of shrinkage or expansion
of the stamper 110 or the resin material layer 104a.
[0062]
When the glass transition temperature of the stamper 110 is different from that of the cured resin material layer 104a, the heating temperature of the bonded body 112 is preferably not higher than the lower glass transition temperature between the glass transition temperature of the stamper 110 and that of the cured resin material layer 104a. The heating temperature is
preferably at least 20°C lower than the lower glass transition temperature between the glass transition temperature of the stamper 110 and that of the cured resin material layer. The heating temperature is more preferably at least 30°C lower than the lower glass transition temperature. Such a heating
temperature facilitates formation of an excellent uneven pattern on the surface of the interlayer 104.
[0063]
Although the method and apparatus of the heating are not limited, uniform heating of the entire surface of the bonded
body 112 is desirable. In this respect, oven-type heating
apparatuses, heating methods using infrared lamps, and heating methods using infrared rays are suitable. A preferred heating method using infrared rays provides instant heating, whereby a sufficient temperature for detaching the stamper 110 can be
attained within several seconds. Any heating time can be
employed as long as the bonded body 112 is in the heated state. [0064]

The temperature of the bonded body 112 can be measured with a non contact thermometer (for example, KEYENCE IT 2-60 non contact thermometer). When the bonded body 112 has a temperature distribution in its thickness direction, the temperature of the bonded body 112 in the present invention refers to the temperature of the resin material layer 104a. When the temperature of the resin material layer 104a on which the stamper 110 is placed cannot be directly measured, the temperature of the bonded body 112 in the present invention
refers to the temperature of the stamper 110 in contact with the resin material layer 104a. [0065]
Through the above-mentioned operation, the uneven transfer pattern (that is, the uneven transfer pattern) of the stamper
110 is transferred to the surface of the UV-curable resin material layer 104a to form the interlayer 104, whereby an optical recording medium laminate 113 including the first substrate 101, the first recording layer 102, the first reflective layer 103, and the interlayer 104 can be obtained
(see Fig. 1(d)). [0066]
In the method for producing the optical recording medium of this embodiment, the stamper 110 can be readily detached from the interlayer 104 without excess load in a heated state.
Consequently, an excellent uneven pattern can be formed on the
interlayer 104. Furthermore, deformation of the first recording layer 102 and the first reflective layer 103 may be suppressed.


The uniform surface of the interlayer 104 stabilizes the signal waveform for recording and playback optical information. As a result, the interlayer 104 having an excellent uneven pattern with few defects can be prepared at low costs. 5
[0067]
In the method for producing the optical recording medium of this embodiment, the stamper 110 can be readily detached from the interlayer 104 without excess load, whereby the residue on the UV-curable resin barely adheres to the stamper 110. This
facilitates the reuse of the stamper 110.
In the method for producing the optical recording medium of this embodiment, another advantage of the readily detachment of the stamper 110 from the interlayer 104 is a significantly expanded range of material selection for the stamper 110.
[0068]
[7. Second Recording Layer Forming Step]
In a subsequent second recording layer forming step, as shown in Fig. 1(e), the second recording layer 105 is formed on the interlayer 104. The method for forming the second recording
layer 105 is not limited. For example, the second recording layer 105 can be formed by the following method. That is, a coating solution containing an organic dye is applied onto the surface of the interlayer 104 by spin coating. The solvent contained in the coating solution is removed by heating to form
the second recording layer 105. By repeating these steps from [4. Resin Material Layer Forming Step] to [7. Second Recording


Layer Forming Step], a multilayer optical recording medium can
be efficiently produced.
[0069]
While this embodiment describes direct formation of the second recording layer 105 on the interlayer 104 as an example, the second recording layer 105 can be formed with an underlying layer (for example, a protective layer or a buffer layer) without limitation, depending on the type or the configuration of the optical recording medium 100.
[0070]
[8. Second Reflective Layer Forming Step]
In a subsequent second reflective layer forming step, as shown in Fig. 1(f), the second reflective layer 106 is formed on the second recording layer 105. The method for forming the
second reflective layer 106 is not limited. For example, the second reflective layer 106 can be formed on the second recording layer 105 by sputtering deposition using an Ag alloy. [0071]
[9. Second Substrate Forming Step]
In a subsequent second substrate forming step, the second substrate 108 is formed on the second reflective layer 106 as shown in Fig. 1(g). Any method may be employed for forming the second substrate 108 without limitation. For example, the second substrate 108 can be adhered on the second reflective
layer 106 on the adhesive layer 107. Any material may be used for the second substrate 108 without limitation. In this


embodiment, a polycarbonate mirror-surface substrate prepared by
injection molding is used as the second substrate 108.
[0072]
The configuration of the adhesive layer 107 is not limited. For example, the adhesive layer 107 may be transparent or opaque. The surface of the adhesive layer 107 may be rough to some extent. A slowly hardening adhesive may also be used without any problem. For example, the slowly hardening adhesive is applied onto the second reflective layer 106 by screen printing, followed by irradiation with UV light. The second substrate 108 is then urged to the adhesive, whereby the adhesive layer 107 is formed. A pressure-sensitive double-coated adhesive tape is disposed between and is pressed by the second reflective layer 106 and the second substrate 108, whereby the adhesive layer 107
can be formed. [0073]
Through these steps, the optical recording medium 100 is completed. According to the method for producing the optical recording medium of this embodiment, the optical recording
medium 100 having the layer configuration shown in Fig. 1(g) can be prepared.
The layer configuration shown in Fig. 1(g) is an example. An optical recording medium having an alternative underlying layer not shown in Fig. 1(g) (for example, disposing an
underlying layer between the first substrate 101 and the first recording layer 102) may also be produced by the method for producing the optical recording medium of this embodiment. Any

other step may also be incorporated before, during, or after
each of the above-described steps.
[0074]
The method for producing the optical recording medium of this embodiment can be achieved, for example, with an apparatus 1 for producing an optical recording medium, as shown in Fig. 4. That is, the apparatus 1 includes a first recording layer forming device 2 for operating the step of forming the first recording layer; a first reflective layer forming device 3 for
operating the step of forming the first reflective layer; a
resin material layer forming device 4 for operating the step of forming the resin material layer; a resin material layer curing device for operating the step of curing the resin material layer; a stamper detaching device 6 for operating the step of
detaching the stamper; a second recording layer forming device 7 for operating the step of forming the second recording layer; a second reflective layer forming device 8 for operating the step of forming the second reflective layer; a second substrate forming device 9 for operating the step of forming the second
substrate; and a carrying device 10 for carrying the optical recording medium 100 and an intermediate in progress between these devices 2 to 9 in the above-described sequence.
[0075]
The production apparatus 1 include means for forming the
first recording layer 102 on the first substrate 101 directly or with an underlying layer (first recording layer forming device 2); means for forming the resin material layer 104a on the first


recording layer 102 directly or with another underlying layer (resin material layer forming device 4); means for placing the stamper 110 having the uneven transfer pattern corresponding to the uneven pattern on the resin material layer 104a and curing 5 the resin material layer 104a to produce the bonded body 107
including the first substrate 101, the first recording layer 102, the resin material layer 104a, and the stamper 110 (resin material layer curing device 5); and means for detaching the stamper 110 from the bonded body 107 and transferring the uneven
transfer pattern to the resin material layer 104a to form the interlayer 104 (stamper detaching device 6), wherein the means for detaching the stamper 110 (stamper detaching device 6) detaches the stamper 110 from the bonded body 107 in a heated state. The production apparatus 1, used for implementation of
the above-described method for producing an optical recording medium, can produce an optical recording medium including an interlayer having an excellent uneven pattern with few defects at low costs and can ensure the above-described advantage. [0076]
The production apparatus 1 described herein is just an example of the production apparatus for implementation of the above-described method for producing an optical recording medium. The production apparatus for producing an optical recording medium of the present invention is not limited to this, and can
be modified for implementation within the scope of the present invention. For example, the devices 2 to 10 can be assembled in any combination. Meanwhile, the production apparatus 1 can be


configured in combination with any other apparatus not described herein. Furthermore, the devices 2 to 10 may also be assembled into a single production apparatus 1, as described in this example. Alternatively, the separate devices 2 to 10 may configure a production apparatus 1 in total.
[0077]
Moreover, a certain device may have the function of any other device in the production apparatus 1. Examples of such devices include the first recording layer forming device 2 and
the second recording layer forming device 7, or the first reflective layer forming device 3 and the second reflective layer forming device 8.
[0078]
[II. Second Embodiment]
In the method for producing an optical recording medium of the present invention, the resin material layer may be formed of a plurality of resin sublayers in consideration of the warpage of the optical recording medium and recording characteristics of the recording layer to be formed on the interlayer. Among the
plurality of resin sublayers of the resin material layer, a
resin sublayer in contact with the stamper for forming an uneven pattern is the outermost resin sublayer.
[0079]
In the case of the resin material layer including a
plurality of resin sublayers, the number of the resin sublayers of the resin material layer is not limited. More specifically, the number of the resin sublayers is usually ten or less,


preferably five or less, and more preferably four or less. However, the number of the resin sublayers should be at least two. From the viewpoint of the production efficiency, the preferred number of the resin sublayers of the resin material layer is in the range of two to five. From the viewpoint of the production efficiency, the particularly preferred number of the resin sublayers of the resin material layer is two or three.
[0080]
Hereinafter, a case of a resin material layer including two
resin layers will now be described with reference to the second embodiment. In the second embodiment described below, the method for forming a resin material layer and the method for placing the stamper are modified from the first embodiment. In the description, the resin for forming the resin material layer
104 is the same UV-curable resin as that in the first embodiment. [0081]
In this embodiment, the substrate preparation step, the first recording layer forming step, and the first reflective layer forming step are performed as in the first embodiment.
Thereafter, the resin material layer forming step is performed.
Figs. 2(a) and 2(b) are schematic views illustrating the step of forming the resin material layer of the method for producing the optical recording medium in accordance with the
second embodiment of the present invention. In Figs. 2(a) and 2(b), the same elements as described in Figs. 1 (a) to Fig. 1(g) are denoted by the same numerals described in Figs. 1(a) to 1(g).


[0082]
In the step of forming the resin material layer of the method of this embodiment, a stamper 110 having a second resin sublayer 104a2, i.e., the outermost resin layer on its surface is placed on a data substrate 111 having a first resin sublayer
104ai on its surface, whereby the UV-curable resin material layer 104a (see Fig. 3) including the first resin sublayer 104a1 and the second resin sublayer 104a2 is formed as shown in Figs. 2(a) and 2(b). In other words, the stamper 110 having the second
resin sublayer 104a2, i.e., the outermost resin layer on its
surface is placed on the first resin sublayer 104a1, whereby the stamper 110 is placed on the UV-curable resin material layer 104a. This will be described below in detail.
[0083]
In order to form the UV-curable resin material layer 104a, the first resin sublayer 104a1 is formed on the data substrate 111 including the first substrate 101, the first recording layer 102, and the first reflective layer 103, as shown in Fig. 2(a). The method for producing the data substrate 111 is the same as
that in the first embodiment. Any method may be employed for forming the first resin sublayer 104a1 without limitation. For example, the first resin sublayer 104a1 can be formed as in the method for forming the UV-curable resin material layer 104a of the first embodiment.
[0084]
On the other hand, the second resin sublayer 104a2 is formed on the stamper 110 having the uneven transfer pattern on

its surface, as shown in Fig. (2b). Materials used for the stamper 110 may be the same as in the first embodiment. In this embodiment, the second resin sublayer 104a2 in contact with the stamper 110 for forming an uneven pattern is the outermost resin layer.
Any method may be employed for forming the second resin sublayer 104a2 without limitation. For example, a precursor of the UV-curable resin can be applied by spin coating on the entire surface of the stamper 110 to form the second resin
sublayer 104a2. [0085]
The stamper 110 having the second resin sublayer 104a2 is placed on the data substrate 111 having the first resin sublayer 104a1 such that the first resin sublayer 104a1 faces the second
resin sublayer 104a2. The UV-curable resin material layer 104a including the first resin sublayer 104a1 and the second resin sublayer 104a2 is formed on the entire surface of the data substrate 111 (that is, on the surface of the first reflective layer 103). That is, the UV-curable resin material layer 104a
is formed on the first reflective layer 103 on the first
recording layer 102. Through the above-described operation, the stamper 110 having an uneven transfer pattern can be placed on the UV-curable resin material layer 104a. In other words, the stamper 110 is placed on the surface of the UV-curable resin
material layer 104a which is disposed opposite to the first recording layer 102.


When the stamper 110 is placed, the urging force of the stamper 110 against the data substrate 111 is adjusted such that the UV-curable resin material layer 104a has a predetermined range of film thickness.
[0086]
In the step of forming a resin material layer, as in the first embodiment, the UV-curable resin layer 104a is cured by irradiation with UV light through the stamper 110, as shown in Fig. 3. Through this step, a bonded body 112' including the
data substrate 111, the UV-curable resin material layer 104a, and the stamper 110 is prepared. Fig. 3 is a schematic view illustrating the step of curing the resin material layer in the method for producing the optical recording medium in accordance with the second embodiment of the present invention. In Fig. 3,
the same elements as described in Figs. 1(a) to 1(g), Figs. 2(a), and 2(b) are denoted by the same numerals described in Figs. 1(a) to Kg), Figs. 2(a), and 2(b).
[0087]
In the step of detaching a stamper, as in the first
embodiment, the stamper 110 is detached from the UV resin
material layer 104a while the bonded body 112' is in a heated state, whereby a satisfactory interlayer 104 can be formed.
In the second embodiment, the upper limit of the temperature (heating temperature) of the bonded body 112' during
the detachment of the stamper 110 is preferably the glass
transition temperature of the stamper 110 and that of the cured second resin sublayer 104a2, i.e., the outermost resin layer.

That is, the temperature is preferably not higher than the glass transition temperature of the stamper 110 and that of the second cured resin sublayer 104a2 (outermost resin layer). Since the uneven pattern formed on the surface of the interlayer 104 is formed in the second resin sublayer 104a2 (outermost resin layer), the excellent uneven pattern on the interlayer 104 can be readily formed by setting the heating temperature in consideration of the glass transition temperature of the second cured resin sublayer 104a2 (outermost resin layer).
[0088]
When the glass transition temperature of the stamper 110 is different from that of the second cured resin material layer 104a2, the heating temperature of the bonded body 112' is preferably not higher than the lower glass transition
temperature between the glass transition temperature of the stamper 110 and that of the second cured resin material layer 104a2. In addition, the heating temperature is preferably at least 20°C lower than the lower glass transition temperature between the glass transition temperature of the stamper 110 and
that of the second cured resin material layer 104a2 (outermost resin layer). The heating temperature is more preferably at least 30°C lower than the lower glass transition temperature. Such a heating temperature facilitates formation of an excellent uneven pattern on the surface of the interlayer 104.
[0089]
In the second embodiment, the step of forming a second recording layer, the step of forming a second reflective layer,

and the step of forming a second substrate are the same as those in the first embodiment.
Through the above-described steps, the optical recording medium 100 (see Fig. 1(g)) including the interlayer 104 having an excellent uneven pattern with few defects can be produced at low costs, as in the first embodiment. The method for producing the optical recording medium of this embodiment ensures the same advantage as that in the first embodiment.
In this embodiment, the UV-curable resin material layer
104a includes a plurality of resin sublayers (first resin sublayer 104ai and second resin sublayer 104a2) to form the interlayer 104. This has the following advantages: Materials that provide excellent recording characteristics of the second recording layer 105 can be used for the outermost resin layer;
materials that exhibit high adhesiveness with the first
reflective layer 103 can be used for the resin layer in contact with the data substrate 111; and materials that prevent warpage of an optical recording medium can be used for the resin layer in contact with the data substrate 111.
According to this embodiment, the first resin sublayer 104a1 may be composed of a resin having a glass transition temperature lower than that of the second cured resin sublayer 104a2. More specifically, the first resin sublayer 104a1 may be composed of a resin having a glass transition temperature which
is at least 20°C, more preferably at least 40°C, or most
preferably at least 80°C lower than that of the second cured resin sublayer 104a2.


[0090]
The method for producing the optical recording medium of this embodiment can be achieved as in the first embodiment, for example, with a production apparatus 1, as shown in Fig. 4. The production apparatus 1 includes the first recording layer forming device 2 for operating the step of forming a first recording layer; the first reflective layer forming device 3 for operating the step of forming a first reflective layer; the resin material layer forming device 4. for operating the step of
forming a resin material layer; the resin material layer curing device 5 for operating the step of curing a resin material layer; the stamper detaching device 6 for operating the step of detaching a stamper; the second recording layer forming device 7 for operating the step of forming a second recording layer; the
second reflective layer forming device 8 for operating the step of forming a second reflective layer; the second substrate forming device 9 for operating the step of forming a second substrate; and the carrying device 10 for carrying the optical recording medium 100 and an intermediate in progress between
these devices 2 to 9 in the above-described sequence.
This embodiment can also be modified without limitation, like the first embodiment.
[0091]
[III. Description of the Optical Recording Medium Applicable to
the Method and Apparatus for Producing the Optical Recording Medium of the Present Invention]


While the first and second embodiments have been described with reference to a single-sided dual-layer DVD-R having two recording layers containing an organic dye, as an example of an optical recording medium to be produced, the method and apparatus for producing the optical recording medium of the
present invention are applicable to any other optical recording medium without limitation. That is, the present invention is applicable to an optical recording medium or an optical recording medium laminate that is produced by the method for
producing an optical recording medium or an optical recording medium laminate having a substrate, a recording layer, and an interlayer having an uneven pattern, the method including forming the resin material layer on the recording layer directly or with an underlying layer; placing the stamper having an
uneven transfer pattern on the resin material layer to cure the resin material layer; and detaching the stamper from the resin material layer, whereby the uneven transfer pattern on the stamper is transferred to the resin material layer to form the interlayer. The advantage of the present invention is
effectively achieved. The method and apparatus for producing the optical recording medium of the present invention are also applicable to, for example, an optical recording medium having a different configuration.
[0092]
The method and apparatus for producing an optical recording medium of the present invention can be applied to, for example, an optical recording medium having a single recording layer.

The method and apparatus for producing an optical recording medium of the present invention can also be applied to, for example, an optical recording medium having three or more recording layers and two or more interlayers. In this case, the method for forming the interlayer, which has been explained in the above-described embodiment, can be applied to formation of two or more interlayers.
While the above-described embodiment has been explained for the method and apparatus for producing a substrate incident
optical recording medium, the method and apparatus for producing an optical recording medium of the present invention can be obviously applied to a method and an apparatus for producing a film incident optical recording medium.
[0093]
Preferred optical recording media, which can be applied to the method and apparatus for producing an optical recording medium of the present invention, are recordable media (write-once media such as CD-Rs and DVD-Rs) that can record data only once and are rewritable media (Rewritable media such as CD-RWs
and DVD-RWs) that can record and erase data repeatedly, but not excluding playback-only media (ROM media such as CD-ROMs and DVD-ROMs). In particular, the method and apparatus for producing an optical recording medium of the present invention can achieve stable recording and playback characteristics, when
applied to record able media, and thus are preferred. [0094]


Next, each layer of a single-sided dual-layer optical recording medium 100 represented by a single-sided dual-layer DVD-R shown in Fig. 1(g) will now be described. [First Substrate] The first substrate 101 desirably has excellent optical characteristics such as optical transparency and low birefringence. Moreover, the first substrate 101 desirably has excellent formability such as ease of injection molding. Furthermore, the first substrate 101 desirably has low
hygroscopicity. In addition, the first substrate 101 desirably has shape stability to impart certain rigidity to the optical recording medium.
[0095]
Materials for the first substrate 101 are not particularly
limited. Examples of such materials include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (amorphous polyolefins, in particular), polyester resins, polystyrene resins, epoxy resins, and glasses. Materials for the first substrate 101 may be used alone or in combination of
two or more in any ratio. [0096]
The thickness of the first substrate 101 is usually 2 mm or less and preferably 1.1 mm or less, because coma aberration tends to decrease as a distance between an objective lens and
the recording layer decreases or as the substrate is thinned. This can easily increase the recording density. It should be noted, however, that the thickness of the first substrate 101 is

usually at least 10 am and preferably at least 30 mm in order to ensure the optical characteristics, hygroscopicity, formability, and shape stability sufficiently.
[0097]
[First Recording Layer]
The first recording layer 102 desirably has sensitivity higher than that of recording layers used for optical recording media such as CD-Rs and single-sided DVD-Rs. For example, when the above-described embodiment is applied, the first reflective
layer 103 of the optical recording medium 100 is usually a
translucent reflective film. Half of the incident laser beams 109 pass through the first reflective layer 103. Consequently, the power of the laser beam 109 incident on the first recording layer 102 is reduced by half. Since recording for the first
recording layer 102 should be performed with about half the
power of an incident laser beam, the first recording layer 102
desirably has particularly high sensitivity.
[0098]
Dyes used for the first recording layer 102 are preferably
dye compounds, which have a maximum absorption wavelength Airiax in the range of visible light to near infrared light of about 350 to 900 nm and are suitable for recording using a blue to near microwave laser. Among them, dyes suitable for recording with a near infrared laser having a wavelength in the range from about
770 to 830 nm normally used for CD-Rs, a red laser having a
wavelength in the range from about 620 to 690 nm normally used

for DVD-Rs, or a so-called blue laser having a wavelength of 410
nm or 515 nm are more preferred dye compounds.
[0099]
Although the dyes used for the first recording layer 102 are not particularly limited, organic dye materials are normally used. Examples of such organic dye materials include macrocyclic aza-annulene dyes (such as phthalocyanine dyes, naphthalocyanine dyes, and porphyrin dyes), pyrromethene dyes, polymethine dyes (such as cyanine dyes, merocyanine dyes, and
squarylium dyes), anthraquinone dyes, azulenium dyes, metal complex azo dyes, and metal complex indoaniline dyes. These dyes may be used alone or in combination of two or more in any ratio.
[0100]
The thickness of the first recording layer 102 is not particularly limited because the suitable thickness varies depending on the recording method. In order to obtain a sufficient modulation, the thickness of the first recording layer 102 is usually 5 nm or more, preferably 10 nm or more, and
more preferably 20 nm or more. However, because of the need of optical transmission, the thickness of the first recording layer
102 is usually 3 p.m or less, preferably 1 }im or less, and more preferably 200 nm or less. [0101]The methods for forming the first recording layer 102 are not particularly limited. Examples of such methods include conventional thin film forming processes such as vacuum

deposition, sputtering, doctor blading, casting, spin coating, and dipping. Wet methods of forming films such as the spin coating are preferred in view of mass productivity and costs. Meanwhile the vacuum deposition is preferred because it facilitates uniform formation of the recording layer.
[0102] [First Reflective Layer]
The first reflective layer 103 desirably has low absorption of recording/reading light, a light transmittance of usually at
least 40%, and moderate optical reflectivity. Examples of the specific configuration of the first reflective layer 103 include layers with moderate light transmittance formed of a thin metal film having highly reflectance. Meanwhile, the first reflective layer 103 desirably has a certain level of corrosion resistance.
Moreover, the first reflective layer 103 desirably has blocking properties to prevent harmful effect on the first recording layer 102 caused by migration of foreign components from the layer (the interlayer 104 in the above-described embodiment) above the first reflective layer 103.
[0103]
Although materials for the first reflective layer 103 are not particularly limited, materials having moderately high reflectivity relative to the wavelength of reading light are preferred. Examples of such materials for the first reflective
layer 103 include metals and semimetals such as Au, Al, Ag, Cu,
Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and rare

earth metals. These metals and semimetals may be used alone or in the form of an alloy. Materials for the first reflective layer 103 may be used alone or in combination of two or more in any ratio.
[0104]
The thickness of the first reflective layer 103 is usually 50 nm or less, preferably 30 nm or less, and more preferably 20 nm or less. This range provides a light transmittance of at least 40%. However, in order to prevent an influence of the
layer above the first reflective layer 103 on the first
recording layer 102, the thickness of the first reflective layer 103 is usually at least 3 nm and preferably at least 5 nm. [0105]
Any method may be employed for forming the first reflective
layer 103 without limitation. Examples of such methods include sputtering, ion plating, chemical deposition, and vacuum deposition.
[0106]
[Interlayer]
The interlayer 104 is composed of a transparent resin that can form an uneven pattern such as grooves and pits, and have a high adhesion to other layers. In order to achieve high shape stability of media, resins having small shrinkage during curing are preferred.
The interlayer 104 may be a single layer structure
described in the first embodiment or a multilayer structure described in the second embodiment.

[0107]
Moreover, the interlayer 104 is usually compatible with the second recording layer 105. In order to reduce the compatibility between the interlayer 104 and the second recording layer 105 and damage to the second recording layer 105, a proper buffer layer is desirably disposed between the interlayer 104 and the second recording layer 105. The buffer layer may also be disposed between the interlayer 104 and the first reflective layer 103.
[0108]
The interlayer 104 is desirably composed of a material that does not damage the second recording layer 105. Examples of such materials of the interlayer 104 include thermoplastic resins, and hardening resins such as thermosetting resins and
radiation-curable resins. Materials for the interlayer 104 may be used alone or in combination of two or more in any ratio.
Among the materials for the interlayer 104 preferred are radiation-curable resins. Among the radiation-curable resins preferred are UV-curable resins. Use of these resins
facilitates transfer of the uneven pattern on the stamper. [0109]
Examples of the UV-curable resins include radical (radical polymerizable) UV-curable resins and cationic (cationic polymerizable) UV-curable resins. Any of these may be used.
The radical UV-curable resin has a composition containing a UV-curable compound (radical UV-curable compound) and a photopolymerization initiator, as essential components. For

example, monofunctional (meth)acrylates and multifunctional (meth)acrylates can be used as polymerizable monomer components for the radical UV-curable compounds. These may be used alone or in combination of two or more in any ratio. Both acrylates 5 and methacrylates are herein referred to as (meth)acrylates.
Any photopolymerization initiator may be used without limitation. For example, preferred photopolymerization initiators are of a molecular cleavage type and a hydrogen abstraction type. In the present invention, the interlayer is preferably formed by curing a precursor of a UV-curable resin mainly composed of a radical polymerizable acrylate ester.
[0110]
Examples of cationic UV-curable resins include epoxy resins containing cationic polymerization photopolymerization initiators. Examples of the epoxy resins include bisphenol A-epichlorohydrin epoxy resins, alicyclic epoxy resins, long chain aliphatic epoxy resins, brominated epoxy resins, glycidyl ester-type epoxy resins, glycidyl ether-type epoxy resins, and heterocyclic epoxy resins. Epoxy resins having low free chlorine and chlorine ion contents are preferred. The chlorine content is preferably 1% by weight or less and more preferably 0.5% by weight or less.
Examples of cationic photopolymerization initiators include sulfonium salts, iodonium salts, and diazonium salts.
[0111]
When a radiation-curable resin is used as a material for the interlayer 104, the radiation-curable resin that is liquid

at temperatures from 20°C to 40°C may be preferably used. Since the radiation-curable resin can be applied without solvent during forming the resin material layer 104a, the productivity improves. The viscosity is preferably adjusted within the range
of 20 to 4000 mPa.s. [0112]
A spiral or concentrical uneven pattern is formed on the interlayer 104. The uneven pattern includes grooves and lands. The second recording layer 105 usually records and playbacks information using these grooves and/or lands as recording tracks. The method and apparatus for producing an optical recording medium of the present invention have an advantage in that the uneven pattern usually used for recording tracks can be satisfactory formed, whereby the optical recording medium 100 including the interlayer 104 having only few defects can be prepared.
[0113]
The width of these grooves is usually about 100 to 500 nm and the depth of the groove is about 10 to 250 nm. When a spiral recording track is formed, the tracking pitch is preferably about 0.1 to 2.0 mm.
Preferably, the thickness of the interlayer 104 should be
accurately controlled and it is usually 5 mm or more and preferably 10 mm or more. However, the thickness of the interlayer 104 is usually 100 mm or less and preferably 70 mm or less.
[0114]


[Second Recording Layer]
As in the first recording layer 102, it is preferred that the second recording layer 105 generally have higher sensitivity than that for a recording layer used for optical recording media such as CD-Rs and single-sided DVD-Rs. Moreover, in order to achieve favorable recording and playback characteristics, preferably the second recording layer 105 should be composed of a dye having low heat generation and a high refractive index. In addition, it is desirable to set the reflection and absorption of light within an appropriate range in a combination of the second recording layer 105 and the second reflective layer 106.
[0115]
Materials for the second recording layer 105 and methods for forming this layer are the same as those of the first
recording layer 102. However, the preferred methods for forming the second recording layer 105 are wet film forming methods. Materials for the first recording layer 102 and the second recording layer 105 may be same or different.
[0116]
Compounds for the second recording layer 105 are not particularly limited. The same compounds as those in the first recording layer 103 are preferably used. When an organic dye material is used for the recording layer, the depth of the guide grooves on the interlayer 104 is generally deeper than that on the recording layer in a phase-change optical recording medium described below. In particular, when the second recording layer

105 contains an organic dye material, it is difficult to form the second recording layer 105 in a state that the deep grooves are maintained on the interlayer 104. However, in the present invention, even when the second recording layer contains an organic dye material, the uneven pattern formed on the
interlayer 104 can be successfully transferred to the recording
layer, as an uneven pattern.
[0117]
The thickness of the second recording layer 105 is not particularly limited because the suitable thickness varies
depending on the recording methods. The thickness of this layer is usually at 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more. In order to achieve a moderate reflectivity, the thickness of the second recording layer 105 is
usually 3 mm or less, preferably 1 urn or less, and more preferably 200 nm or less. [0118] [Second Reflective Layer]
The second reflective layer 106 desirably has high reflectivity and high durability.
[0119]
Materials that have sufficiently high reflectivity at the wavelength of reading light are preferred for the second reflective layer 106. Examples of such materials for the second reflective layer 106 include metals such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd, and alloys thereof. Among them, Au, Al, and Ag having high reflectivity are suitable for materials for


the second reflective layer 106. In addition to these metal elements as the main component, the second reflective layer 106 may contain other components. Examples of the other components include metals and semimetals such as Mg, Se, Hf, V, Nb, Ru, W, 5 Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and rare earth metals. Materials for the second reflective layer 106 may be used alone or in combination of two or more in any ratio.
[0120]
In order to ensure a high reflectivity, the thickness of the second reflective layer 106 is usually 20 nm or more, preferably 30 nm or more, and more preferably 50 nm or more. However, in order to enhance the recording sensitivity, the thickness of this layer is usually 400 nm or less and preferably
300 nm or less.
[0121]
Any method may be employed for forming the second reflective layer 106 without limitation. Examples of such methods include sputtering, ion plating, chemical deposition,
and vacuum deposition.
A known inorganic or organic interlayer and an adhesive layer can also be provided for improving the reflectivity, recording characteristics, and adhesiveness at the front and back surfaces of the second reflective layer 106.
25 [0122]
[Adhesive layer]


Preferably, the adhesive layer 107 exhibits high adhesion force and low shrinkage during curing and adhesion in view of high shape stability of the optical recording medium 100. Preferably, the adhesive layer 107 is composed of a material that does not damage the second reflective layer 106. A
protective layer made of a known inorganic or organic material may be provided between the second reflective layer 106 and the adhesive layer 107 in order to suppress damages.
[0123] The same materials as those used for the interlayer 104 can be used for the adhesive layer 107.
The thickness of the adhesive layer 107 is usually 2 mm or more and preferably 5 mm or more. Nevertheless, in order to minimize the thickness of the optical recording medium 100 as much as possible and to prevent a reduction in productivity due to prolonged curing time, the thickness of the adhesive layer
107 is usually 100 (am or less.
A pressure-sensitive double-coated adhesive tape is also
applicable to the adhesive layer 107. The pressure-sensitive double-coated adhesive tape is disposed between and is pressed
by the second reflective layer 106 and the second substrate 108,
whereby the adhesive layer 107 can be formed.
[0124]
[Second Substrate]
The second substrate 108 desirably has high mechanical
stability and high rigidity. Moreover, the second substrate 108
desirably exhibits high adhesion to the adhesive layer 107.

Materials for the second substrate 108 having such characteristics may be the same as the materials used in the first substrate 101. In addition, Al alloy substrates including Al as the main component such as an Al-Mg alloy, Mg alloy substrates including Mg as the main component such as an Mg-Zn alloy, substrates composed of any one of silicon, titanium, and ceramics, and substrates formed in combination of these substrates are also used. The above-mentioned materials may be used alone or in combination of two or more in any ratio.
[0125]
A preferred material for the second substrate 108 is polycarbonate in view of high productivity such as ready formability, costs, low hygroscopicity, and shape stability. Amorphous polyolefin is also preferred in view of chemical
resistance and low hygroscopicity. A glass substrate is also preferred in view of quick response. However, for optical recording media (so-called film incident type) such as Blu-ray disks in which a light beam is incident from the second substrate 108, the second substrate 108 may be composed of any
hardening resin without limitation. Examples of hardening
resins include radiation-curable resins and thermosetting resins. Among these preferred are UV-curable resins, which belong to the radiation-curable resins. A film of general-purpose low-cost resins such as polycarbonate resins and acrylic resins can also
be used.
In order to ensure sufficient rigidity of the optical recording medium 100, the second substrate 108 preferably has a

certain level of thickness. The thickness of the second substrate 108 is preferably 0.3 mm or more. Nevertheless, the thickness of the second substrate 108 is 3 mm or less and preferably 1.5 mm or less.
[0126]
[Other Layers]
In the optical recording medium 100 having the above-described laminated structure, any other optional layer may also be interposed, if necessary. Alternatively, any other optional
layer may also be disposed on the outermost surface of the
optical recording medium 100. In the optical recording medium 100, a printing receptive layer, which is writable (printable) with any type of printer such as an ink-jet printer or thermal transfer printer or any writing tool, may be disposed, if
necessary, on the surface, which does not function as an
incident surface for recording light or reading light. Moreover, two optical recording media 100 may be bonded together such that the first substrate 101 resides outward. Such bonding of two optical recording media 100 can provide a high-capacity medium
having four recording layers. In the bonding of these two optical recording media 100, two adhesive layers 107 and two second substrates 108 are not absolutely necessary. That is, a single or no adhesive layer 107 or a single or no second substrate 108 is also available.
[0127]
The method and apparatus for producing an optical recording medium of the present invention are also applied to phase-change

rewritable compact disks (CD-RWs, i.e., CD-ReWritables) and phase-change rewritable DVDs. A known layer configuration can be appropriately applied to layers such as a recording layer of a phase-change optical recording medium. The phase-change CD- RWs or rewritable DVDs detect recorded information signals by a change in difference of reflectivity and phase caused by a difference in the refractive index between the amorphous state and the crystalline state of the recording layer composed of a phase-change recording material. Specific examples of the
phase-change recording materials include SbTe, GeTe, GeSbTe,
InSbTe, AgSbTe, AglnSbTe, GeSb, GeSbSn, InGeSbTe, and InGeSbSnTe. Among them, the recording layer preferably has a composition containing Sb as the main component in order to increase the crystallization rate. These materials may be used alone or in
combination of two or more in any ratio. In the phase-change optical recording medium, these above exemplified recording materials may be used for the recording layer instead of dyes. Examples
[0128]
The present invention will now be described in detail below based on Examples. It should be noted that the present invention is not limited to the following Examples, within the scope of the present invention. In the description of the Examples, "Tg" refers to glass transition temperature after
curing.
[0129]
[Examples 1 to 4 and Comparative Examples 1 and 2]

(1) Preparation of Optical Recording Medium
(1-1) Preparation of Stamper
A polycarbonate disk stamper (hereinafter referred to as PC
stamper) having an outer diameter of 120 mm and a thickness of 0.6 mm and a central hole with a diameter of 15 mm was prepared
by injection molding. In the injection molding, a nickel mother
plate including guide grooves with a track pitch of 0.74 urn, a
width of 0.32 10mm, and a depth of 175 nm was used. The accurate
transfer of the guide grooves (uneven pattern) on the nickel mother plate to the PC stamper was confirmed with an atomic
force microscope (AFM).
[0130]
(1-2) Preparation of Data Substrate
A polycarbonate substrate (first substrate) having a diameter of 120 mm and a thickness of 0.57 mm and including
grooves with a pitch of 0.74 mm, a width of 0.33 mm, and a depth of 160 nm was prepared by injection molding using the nickel stamper.
Next, a solution of a metal complex azo dye in
tetrafluoropentanol (concentration: 2% by weight) was prepared, was placed dropwise on the substrate, and was applied by a spinner process. After the coating, a first recording layer was formed by drying at 70°C for 30 minutes. Moreover, a translucent first reflective layer having a thickness of 17 nm was formed on
the first recording layer by a sputtering process using an Ag alloy composed of Ag-Bi (Bi: 1.0 atomic %).
[0131]

(1-3) Formation of Interlayer
Next, a predetermined UV-curable resin [1] for forming a first resin layer was placed dropwise into a round shape on the first reflective layer, and a film (first resin layer) having a thickness of about 25 mm was formed by a spinner process.
Meanwhile, a predetermined UV-curable resin [2] for forming a second resin layer (outermost resin layer) was placed dropwise into a round shape on a surface having the guide grooves of the PC stamper, and a film (second resin layer) having a thickness
of about (am was formed by a spinner process.
[0132]
Next, the first substrate was bonded to the PC stamper such
that the first resin layer faced the second resin layer. The
first resin layer and the second resin layer were irradiated 15 with UV light through the PC stamper for curing and adhesion,
whereby a bonded body was formed.
The UV-curable resin [1] and [2] used was each a radical
UV-curable resin. The detailed description is given below. The
glass transition temperatures of the polycarbonate for the PC 20 stamper and of the UV-cured resin [2] for forming the outermost
resin layer after curing are summarized in Table 1.
[0133]
UV-curable resin [1]: SD6036 (Tg = 60°C) made by DAINIPPON
INK AND CHEMICALS, INCORPORATED UV-curable resin [2]: MPZ388 (Tg = 161°C) made by NIPPON
KAYAKU CO., LTD.
[Table 1]

Glass transition temperature (°C)
Polycarbonate 145
UV-curable resin [2] 161
[0134]
The bonded body was placed into an isothermal bath (oven) maintained at 100°C and left to stand for a predetermined time (the residence time was varied between Examples and Comparative Examples).
The bonded body was then taken out from the isothermal bath. After the surface temperature of the bonded body was measured with a KEYENCE IT 2-60 non contact thermometer, the PC stamper was detached. The time placed in the isothermal bath and the 10 surface temperature of the bonded body immediately before detachment of the PC stamper are summarized in Table 2.
[0135] [Table 2]

Heatingtemperature(°C) Heating time (min) Spontaneouscooling time (min) Temperatureimmediatelybeforedetachment (°C)
Example 1 100 1 Non 62
Example 2 100 3 Non 81
Example 3 100 5 Non 82
Example 4 100 10 Non 85
Comparative Example 1 (not heated) (not heated) Non 25
Comparative Example 2 100 5 5 25
[0136]
The PC stamper was detached from the second resin layer (outermost resin layer) as follows: A knife edge was inserted into the outer periphery of the bonded body. The PC stamper was

detached from the second resin layer (outermost resin layer) by
applied force.
The surface of the PC stamper after the detaching was
visually observed under a fluorescent lamp or with an optical 5 microscope. The detaching characteristics were evaluated based
on the following criteria:
o: easily detachable with no residue of UV-curable resin
observed on the surface of the PC stamper
x: barely detachable, or residue (scratch) of UV-curable 10 resin visually observed on the surface of the PC stamper after
the detaching
The results of the detaching characteristics of Examples 1
to 4 and Comparative Examples 1 and 2, which were evaluated
based on the above criteria, are summarized in Table 3. Through the operation, an interlayer having a thickness of about 50 \im
and including the first resin layer and the second resin layer
was formed.
[0137]
(1-4) Formation of Second Recording Layer 20 The solution of a metal complex azo dye in
tetrafluoropentanol (concentration: 2% by weight) was placed
dropwise on the interlayer, and was applied by a spinner process.
After the coating, the interlayer was dried at 70°C for 30
minutes to form a second recording layer. Moreover, a second reflective layer having a thickness of
120 nm was formed on the second recording layer by a sputtering
process using an Ag alloy composed of Ag-Bi (Bi: 1.0 atomic %).

The UV-curable resin was applied on the second reflective layer by spin coating to form an adhesive layer. A polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was placed on the adhesive layer to form a second substrate. The second substrate was cured and bonded by irradiation with UV light.
Through the above processes, a multilayer optical recording medium having two recording layers was prepared.
[0138]
(2) Evaluation of Recording and Playback Characteristics of Optical Recording Medium
(2-1) Measurement of Push-Pull Signal from Optical Recording Medium
A push-pull signal generated from the second recording
layer of the optical recording medium (optical recording medium prepared in (1) Preparation of Optical Recording Medium) having two recording layers prepared in advance was measured. A larger value represents better recording characteristics. Here, the push-pull signal is defined by the following equation:
[0139]
[Equation 1]


[0140]
In the equation, (I1_I2)pp denotes the peak-to-peak amplitude of an (I1-I2) signal; (I1+I2)max denotes the maximum

value of an (I1+I2) signal, and (I1+I2)min denotes the minimum value of the (I1+I2) signal. Moreover, when the read signal from the optical recording medium is received by a quadrant photodetector including quadrisected detector segments (PDl, PD2, 5 PD3, and PD4), (I1) represents the sum of outputs from PDl and PD2 (I1=PDl+PD2) located on the left side relative to a virtual center of a guide groove. Meanwhile, (I2) represents the sum of outputs from PD3 and PD4 (I2=PD3+PD4) located on the right side relative to the virtual center of the guide groove.
[0141]
Here, the optical recording medium was rotated at 3.8 m/s while a focus servo was applied to the second recording layer and a tracking servo was set to an open-loop state. In general, an optical disk has an eccentricity of several tens of
micrometers. Accordingly, a reading beam crosses the guide
grooves and lands by several tens of times per revolution. The (I1-I2) signal and (I1+I2) signal represent the sinusoidal outputs.
The push-pull signal was measured at three positions (radial position: 25 mm, 40 mm, and 55 mm) on the optical
recording medium. The results of the push-pull signals of the optical recording media of Examples and Comparative Examples are summarized in Table 3.
[0142] (2-2) Measurement of PI Error of Optical Recording Medium
The PI error was measured with an Expert DVDT-SD1 instrument. According to DVD+R 8, 5 Gbytes Basic Format


Specifications version 1.0, PI error values of less than 280 were acceptable. A smaller PI error value is preferred.
The PI error was measured at three positions (radial position: 25 mm, 40 mm, and 55 mm) on the optical recording medium. The results of the measurement of the PI error of
optical recording media of Examples and Comparative Examples are summarized in Table 3.
[0143] [Table 3]

PI error Push-pull signal Detaching characteristics
Radial positionof opticalrecording medium(mm) Radial positionof opticalrecording medium(mm)
25 40 55 25 40 55
Example 1 24 25 25 0.39 0.38 0.37 o
Example 2 16 17 33 0.40 0.40 0.38 o
Example 3 30 34 45 0.40 0.39 0.38 o
Example 4 24 22 30 0.40 0.40 0.39 o
Comparative Example 1 31 31 68 0.37 0.38 0.38 x
Comparative Example 2 22 20 29 0.36 0.38 0.38 X
[0144]
The results shown in Table 3 demonstrate the following facts. In the case of detachment of the PC stampers (Examples 1 to 4) after heating in the detaching step, the PC stampers exhibit excellent detaching characteristics. Moreover, optical 15 recording media exhibit well-balanced recording characteristics (PI error and push-pull signal).
It is believed that heating the bonded body causes a difference in the thermal expansion between the PC stamper and


the second resin layer (outermost resin layer) and reduces the intermolecular bonding force at the interface (adherent surface) between the PC stamper and the second resin layer (outermost resin layer), whereby the stamper can be readily detached. [0145]
In contrast, in the step of detaching the PC stamper, in the case of detachment of the PC stamper without heating (Comparative Examples 1) and in the case of detachment of the PC stamper spontaneously cooled to room temperature after heating
(Comparative Examples 2), optical recording media exhibit well-balanced recording characteristics (PI error and push-pull signal), but the PC stamper cannot be readily detached from the second resin layer (outermost resin layer).
[0146]
Due to poor detaching characteristics in Comparative Examples 1 and 2, scratches (residues) readily observed by visual check on the surface of the PC stamper after detaching. This suggests that defects such as microscratches and flaking may exist on the surface of the interlayer.
[0147]
Optical recording media of Comparative Examples 1 and 2 were excellent in push-pull signal and PI error at radial positions of 25 mm, 40 mm, and 55 mm. In the case of recording on the entire surface of the optical recording medium, the
defects described above may discontinue the recording process.
A possible reason of the poor detaching characteristics in Comparative Examples 1 and 2 is as follows: Polar groups in

polycarbonate are intermolecularly bonded at the interface of
the second resin layer (outermost resin layer). Since this
intermolecular bonding energy is larger than the energy
generated during the delamination at the interface between the 5 PC and the second resin layer (outermost resin layer), the
bonding of the UV-curable resin of the second resin layer
(outermost resin layer) is broken.
In consideration of the stability and quality of industrial
production processes and costs, heating the stamper during detaching is significantly effective.
[0148]
Optical recording media were produced as in Example 3
except that the following UV-curable resins [3] to [5] were used for the second resin layer instead of the UV-curable resin [2]. The push-pull signal, PI error, and detaching characteristics
were measured as in Example 3. Satisfactory results were
obtained as in Example 3.
UV-curable resin [3]: MPZ383A (Tg = 150°C) made by NIPPON
KAYAKU CO., LTD. 20 UV-curable resin [4]: MPZ368 (Tg = 193°C) made by NIPPON
KAYAKU CO., LTD.
UV-curable resin [5]: MPZ383B (Tg = 165°C) made by NIPPON
KAYAKU CO., LTD.
[0149] 25 (3) Basic Experiment for Observing the Surface State of the
Interlayer

The UV-curable resin [1] was placed dropwise into a round shape on a first substrate that was the same type as that used in Example 1, and a film (first resin layer) having a thickness
of about 25 mm was formed by a spinner process. Meanwhile, the UV-curable resin [2] was placed dropwise into a round shape on the surface having the guide grooves of the PC stamper, and a film (second resin layer) having a thickness of about 25 mm was formed by a spinner process.
[0150]
Next, the first substrate was bonded to the PC stamper such that the first resin layer faced the second resin layer. The first resin layer and the second resin layer were irradiated with UV light through the PC stamper for curing and adhesion, whereby a bonded body for the basic experiment was formed.
Thereafter, the PC stamper was detached at room temperature (25°C). The PC stamper was detached from the second resin layer (outermost resin layer) as follows: A knife edge was inserted into the outer periphery of the bonded body for the basic experiment. The PC stamper was detached from the second resin
layer (outermost resin layer) by applied force. [0151]
The detaching characteristics were the same level (evaluation criteria: x) as that of Comparative Examples 1. The surface of the PC stamper and the surface of the interlayer
after detaching were observed by visual check and with a microscope. Scratches on the surface of the stamper and


residues of the interlayer were observed. Scratches were also observed on the surface of the interlayer. Industrial Applicability
[0152]
The present invention can be widely used in any field
relevant to optical recording media. The present invention is particularly suitable for the production of optical recording media each including an interlayer having an uneven pattern, more specifically, CDs, DVDs, and optical recording media
compatible to a blue laser, for example. [0153]
The specific embodiments of the present invention have been described in detail. The foregoing preferred embodiments can be modified by those skilled in the art without departing from the
scope and spirit of the present invention.
This application is based on Japanese Patent Application No, 2005-334434 filed on Nov. 18, 2005 and No. 2006-310969 filed on Nov. 17, 2006, which are hereby incorporated herein by reference.


WE claim:
1. A method for producing an optical recording medium including
a substrate, a recording layer, and an interlayer having an
uneven pattern, the method comprising:
forming the recording layer on the substrate directly or with another underlying layer;
forming a resin material layer on the recording layer directly or with another underlying layer;
placing a stamper having an uneven transfer pattern corresponding to the uneven pattern on the resin material layer and curing the resin material layer to form a bonded body including the substrate, the recording layer, the resin material layer, and the stamper; and
detaching the stamper from the bonded body, whereby the uneven transfer pattern is transferred to the resin material layer to form the interlayer,
wherein the stamper is detached from the bonded body in a heated state.
2. The method according to claim 1, wherein the temperature of the bonded body during the detachment of the stamper is 50°C or more.
3. The method according to one of claims 1 or 2, wherein the temperature of the bonded body during the detachment of the

stamper is not higher than the glass transition temperature of the stamper.
4. The method according to one of claims 1 and 2, wherein
the resin material layer includes a plurality of resin sublayers and the outermost sublayer among the plurality of resin sublayers is in contact with the stamper, and
the temperature of the bonded body during the detachment of the stamper is not higher than the glass transition temperature of the stamper and the glass transition temperature of the cured outermost resin layer.
5. The method according to any one of claims 1 to 4, wherein the stamper comprises a polycarbonate resin.
6. The method according to any one of claims 1 to 5, wherein the resin material layer comprises a radiation-curable resin.
7. The method according to any one of claims 1 to 6, wherein the optical recording medium is a multilayer optical recording medium having two or more recording layers.
8. An apparatus for producing an optical recording medium including a substrate, a recording layer, and an interlayer having an uneven pattern, the apparatus comprising:

means for forming the recording layer on the substrate directly or with another underlying layer;
means for forming a resin material layer on the recording layer directly or with another underlying layer;
means for placing a stamper having an uneven transfer pattern corresponding to the uneven pattern on the resin material layer and curing the resin material layer to form a bonded body including the substrate, the recording layer, the resin material layer, and the stamper; and
means for detaching the stamper from the bonded body, whereby the uneven transfer pattern is transferred to the resin material layer to form the interlayer,
wherein the means for detaching the stamper detaches the stamper from the bonded body in a heated state.






ABSTRACT
To produce an optical recording medium including an interlayer having an excellent uneven pattern with few defects at low costs, a recording layer is formed on the substrate directly or with another underlying layer; a resin material layer is formed on the recording layer directly or with another underlying layer; a stamper having an uneven transfer pattern corresponding to the uneven pattern is placed on the resin material layer and curing the resin material layer to form a bonded body; and the stamper is detached from the resin material layer while the bonded body is in a heated state, whereby the uneven transfer pattern is transferred to the resin material layer to form an interlayer.


Documents:

807-MUMNP-2008-ABSTRACT(3-4-2013).pdf

807-mumnp-2008-abstract.doc

807-mumnp-2008-abstract.pdf

807-MUMNP-2008-CERTIFICATION OF TRANSLATION(6-11-2008).pdf

807-MUMNP-2008-CLAIMS(AMENDED)-(3-4-2013).pdf

807-MUMNP-2008-CLAIMS(AMENDED)-(6-8-2012).pdf

807-MUMNP-2008-CLAIMS(MARKED COPY)-(3-4-2013).pdf

807-MUMNP-2008-CLAIMS(MARKED COPY)-(6-8-2012).pdf

807-mumnp-2008-claims.doc

807-mumnp-2008-claims.pdf

807-MUMNP-2008-CORRESPONDENCE(12-2-2013).pdf

807-MUMNP-2008-CORRESPONDENCE(14-07-2008).pdf

807-mumnp-2008-correspondence(14-7-2008).pdf

807-MUMNP-2008-CORRESPONDENCE(4-9-2012).pdf

807-MUMNP-2008-CORRESPONDENCE(6-11-2008).pdf

807-mumnp-2008-correspondence-received.pdf

807-mumnp-2008-description (complete).pdf

807-MUMNP-2008-DRAWING(6-8-2012).pdf

807-mumnp-2008-drawings.pdf

807-MUMNP-2008-FORM 1(14-07-2008).pdf

807-mumnp-2008-form 1(24-4-2008).pdf

807-MUMNP-2008-FORM 1(4-9-2012).pdf

807-MUMNP-2008-FORM 1(6-8-2012).pdf

807-MUMNP-2008-FORM 13(4-9-2012).pdf

807-mumnp-2008-form 2(title page)-(24-4-2008).pdf

807-MUMNP-2008-FORM 26(14-07-2008).pdf

807-MUMNP-2008-FORM 26(3-4-2013).pdf

807-MUMNP-2008-FORM 3(14-07-2008).pdf

807-mumnp-2008-form 3(24-4-2008).pdf

807-MUMNP-2008-FORM 3(6-8-2012).pdf

807-MUMNP-2008-FORM 5(3-4-2013).pdf

807-mumnp-2008-form-1.pdf

807-mumnp-2008-form-18.pdf

807-mumnp-2008-form-2.doc

807-mumnp-2008-form-2.pdf

807-mumnp-2008-form-3.pdf

807-mumnp-2008-form-5.pdf

807-mumnp-2008-form-pct-ib-304.pdf

807-mumnp-2008-form-pct-ib-308.pdf

807-MUMNP-2008-JAPANESE DOCUMENT(6-8-2012).pdf

807-mumnp-2008-pct-search report.pdf

807-MUMNP-2008-PETITION UNDER RULE 137(3-4-2013).pdf

807-MUMNP-2008-PRIORITY DOCUMENT(6-11-2008).pdf

807-MUMNP-2008-REPLY TO EXAMINATION REPORT(3-4-2013).pdf

807-MUMNP-2008-REPLY TO EXAMINATION REPORT(6-8-2012).pdf

807-MUMNP-2008-SPECIFICATION(AMENDED)-(3-4-2013).pdf

807-mumnp-2008-table.doc

abstract1.jpg


Patent Number 255999
Indian Patent Application Number 807/MUMNP/2008
PG Journal Number 16/2013
Publication Date 19-Apr-2013
Grant Date 17-Apr-2013
Date of Filing 24-Apr-2008
Name of Patentee MITSUBISHI KAGAKU MEDIA CO., LTD.
Applicant Address 31-19, SHIBA 5-CHOME, MINATO-KU, TOKYO, 1080014,
Inventors:
# Inventor's Name Inventor's Address
1 ATSUSHI KOMURA C/O MITSUBISHI KAGAKU MEDIA CO. LTD. 31-19, SHIBA 5-CHOME, MINATO-KU, TOKYO, 1080014
2 MASAFUMI AGA C/O MITSUBISHI KAGAKU MEDIA CO. LTD. 31-19, SHIBA 5-CHOME, MINATO-KU, TOKYO, 1080014
3 YUMI MATSUMURA C/O MITSUBISHI KAGAKU MEDIA CO. LTD. 31-19, SHIBA 5-CHOME, MINATO-KU, TOKYO, 1080014
4 KUMI MIZUNO C/O MITSUBISHI KAGAKU MEDIA CO. LTD. 31-19, SHIBA 5-CHOME, MINATO-KU, TOKYO, 1080014
PCT International Classification Number G11B7/26
PCT International Application Number PCT/JP2006/322988
PCT International Filing date 2006-11-17
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2005-334434 2005-11-18 Japan