Title of Invention

OPTICAL RECORDING MEDIUM AND METHOD FOR MANUFACTURING THE SAME

Abstract To provide an optical recording medium including: a substrate having at least one of grooves and pits on a surface thereof; and a dye recording layer formed over the substrate, wherein the dye recording layer comprises a cyanine dye represented by the following General Formula (I), a squaric acid complex represented by the following General Formula (II), and an amine compound.
Full Text DESCRIPTION
OPTICAL RECORDING MEDIUM AND METHOD FOR
MANUFACTURING THE SAME
Technical Field
The present invention relates to an optical recording medium
having a dye recording layer, and a manufacturing method for the
same.
Background Art
In addition to such optical recording media as Compact Disc
Read-Only Memory (CD-ROM), recordable CDs (CD-Rs and CD-
RWs) are now commercialized and widely used.
In contrast to conventional CDs, CD-Rs and CD-RWs feature
that the user can write to them and signals generated following
recording are designed to meet the conventional CD standards so
that they can be played on CD players available on the market.
As a method of achieving fabrication of such recording media,
for example, Patent Literature 1 discloses a method of
manufacturing a CD-R disc by applying a dye over a substrate by
spin coating to form a light-absorbing layer and providing a metallic
reflective layer on the light-absorbing layer.
Dye-based materials are used as the materials of the light-
absorbing layer.

One feature of CD-R is its high reflectance (65%), which meets
the CD standards. For the purpose of obtaining high reflectance
with the foregoing disc configuration, the light-absorbing layer
needs to have a specific complex refractive index over a wavelength
range of the laser beam source for recording and reproduction, and
utilization of dye's light absorption property is suitable for
achieving this.
As shown in FIG. 1, however, there is a problem that the
complex refractive index is greatly dependent on the wavelength
because it utilizes the feature of the absorption band end in the
light absorption spectrum of the dye film.
As next-generation recording media, DVD-R and DVD+R are
commercialized that are capable of high-density recording and/or
reproduction by using a laser beam with a wavelength of around
650nm rather than using a conventional laser beam with a
wavelength of around 780nm designed for CD. The performance of
recording material containing the foregoing dye for CD-R (e.g.,
pentamethine cyanine dyes or phthalocyanine dyes) is largely
dependent on the wavelength of the laser beam; therefore, it results
in failure to satisfy recording/reproduction characteristics at 650nm.
This is due to a large absorption coefficient (k) at 650nm and low
reflectance, which makes information recording/reproduction
difficult.
To overcome this problem, organic dyes such as trimethine

cyanine dyes, azo dyes and tetra-azaporhirazine are proposed as
materials for recoding layer which adjust the range of the
absorption wavelength of dyes or recording materials. These dyes
are disclosed for instance in Patent Literatures 2, 3, 4, and 5.
Along with a recent increase in the recording velocity for
recordable DVD discs, improvements are made also on recording
materials; examples are squaric acid complexes and trimethine
cyanine dye materials, which are disclosed for instance in Patent
Literatures 6, 7, and 8.
Even with these recording materials, however, it is difficult to
achieve high-speed recording characteristics and archivability
(durability) at the same time. The reason for this is that although
recording materials that exhibit low thermal decomposition
temperatures and high decomposition rates are preferred, these
materials are likely to cause a reduction in heat resistance and wet
resistance. Generally, two or more dye materials are mixed to avoid
this, which however leads to the problem described below.
While a dye recording film is deposited by application of its
coating solution by spin coating, the coating solution being obtained
by dissolving a dye in solvent, the combined use of two or more
different recording materials — for example, a coating solution
containing a cyanine dye with ionic structure and a squalene
compound with chelate structure — is more likely to cause
interactions such as exchange reactions in the mixture, resulting in

failure to obtain desired characteristics due to chemical changes.
In particular, the PF6- ion, an anion in the cyanine dye, is so
reactive that it tends to cause dechelation of squaric acid complex,
for example.
(Patent Literature l) Japanese Patent Application Laid-Open
(JP-A) No. 02-42652
(Patent Literature 2) Japanese Patent (JP-B) No. 2594443
(Patent Literature 3) Japanese Patent Application Laid-Open
(JP-A) No. 09-169166
(Patent Literature 4) Japanese Patent Application Laid-Open
(JP-A) No. 09-66671
(Patent Literature 5) Japanese Patent Application Laid-Open
(JP-A) No. 11-48612
(Patent Literature 6). International Publication No.
WO2002/050190
(Patent Literature 7) Japanese Patent (JP-B) No. 3698708
(Patent Literature 8) Japanese Patent (JP-B) No. 3659922
Disclosure of the Invention
It is an object of the present invention to solve the foregoing
problems and to provide an optical recording medium having a dye
recording layer, which the medium is excellent in recording
characteristics, durability, and productivity, and a method of
manufacturing the optical recording medium.

The present invention is based on the findings by the present
inventors, and means of solving the foregoing problems are as
follows:
An optical recording medium including: a substrate
having at least one of grooves and pits on a surface thereof; and a
dye recording layer formed over the substrate, wherein the dye
recording layer comprises a cyanine dye represented by the
following General Formula (I), a squaric acid complex represented
by the following General Formula (II), and an amine compound:
General Formula (I)

wherein R,1 and R2 independently represent an alkyl group which
may be substituted, an aryl group which may be substituted, or a
benzyl group which may be substituted, Z represents an atom group
for forming an aromatic ring, X represents a monovalent anion, and
L represents a linking group for forming a carbocyanine,
General Formula (II)


wherein R1 and R2, which may be identical or different, are an alkyl
group which may be substituted, an aralkyl group which may be
substituted, an aryl group which may be substituted, or a
heterocyclic ring which may be substituted, Q represents a metal
atom which has a coordinating property, q represents an integer of 2
or 3, and A represents an aryl group which may be substituted, a
heterocyclic ring which may be substituted, or Y=CH- (where Y
represents an aryl group which may be substituted or a heterocyclic
ring which may be substituted).
Since the recording layer contains at least the foregoing
cyanine dye, squaric acid complex and amine compound, it is
possible to prevent interaction of dye with other ingredients upon
mixed and thus to provide an optical recording medium with a dye
layer, which is excellent in recording characteristics, durability, and
productivity.
The optical recording medium according to , wherein
the cyanine dye in the recording layer has PF6 as an anion. By
using PF6 as the anion of the cyanine dye of the dye recording

medium, it is possible to provide an optical recording medium which
is excellent in high-speed recording performance.
The optical recording medium according to , wherein
the content of the amine compound in the recording layer is 10% by
mass or less.
If the content of the amine compound in the dye recording
layer is 10% or less, it is possible to ensure stability upon dye
mixing without causing a reduction in recording characteristics.
The optical recording medium according to one of
and , wherein the amine compound is a nitrogen-containing
heterocyclic compound.
When the amine compound is a nitrogen-containing
heterocyclic compound, the thermal decomposition temperature of
the dye recording layer increases and it is possible to provide an
optical recording medium with excellent heat resistance.
A method for manufacturing an optical recording
medium, including: applying over a surface of a substrate a solvent
in which at least a cyanine dye represented by the following General
Formula (I), a squaric acid complex represented by the following
General Formula (II), and an amine compound are dissolved, to
thereby form a dye recording layer over the substrate, wherein the
optical recording medium comprises the substrate having at least
one of grooves and pits on a surface thereof, and the dye recording
layer formed over the substrate:


wherein R1 and R2 independently represent an alkyl group which
may be substituted, an aryl group which may be substituted, or a
benzyl group which may be substituted, Z represents an atom group
for forming an aromatic ring, X represents a monovalent anion, and
L represents a linking group for forming a carbocyanine,
General Formula (II)

wherein R1 and R2, which may be identical or different, are an alkyl
group which may be substituted, an aralkyl group which may be
substituted, an aryl group which may be substituted, or a
heterocyclic ring which may be substituted, Q represents a metal
atom which has a coordinating property, q represents an integer of 2

or 3, and A represents an aryl group which may be substituted, a
heterocyclic ring which may be substituted, or Y=CH (where Y
represents an aryl group which may be substituted or a heterocyclic
ring which may be substituted).
With this method of the present invention, it is possible to
prevent interaction of dye with other ingredients upon mixed. Thus,
the method of the present invention provides excellent productivity.
The method for manufacturing an optical recording
medium according to , wherein the amine compound is a liquid
tertiary amine.
The use of a liquid tertiary amine in the method of the
present invention results in a high effect of preventing interactions
of dye with other ingredients when mixed. In addition, since the
amine compound is a liquid, the amine compound is not contained in
the resultant recording layer and hence it is possible to bring about
the effect of the present invention.
The method for manufacturing an optical recording
medium according to one of and , wherein the solvent is a
fluorine-substituted alcohol.
Fluorine-substituted alcohols have high solubility, providing
excellent productivity when used in the preparation of a coating
solution for a recording layer in the method of the present invention.
Brief Description of Drawings

FIG. 1 shows an absorption spectrum of a dye film.
FIG. 2 shows an example of a layer configuration of a DVD+R
or DVD-R disc.
FIG. 3 shows optical absorption spectra of dye films in
Examples and Comparative Example.
Best Mode for Carrying Out the Invention
(Operation)
FIG. 2 shows an example of a layer configuration of a DVD+R
or DVD-R disc.
In this drawing, reference numeral 1 denotes a substrate; 2 a
recording layer made of dye; 3, a reflective layer; 4, a protective
layer; 5, an adhesive layer; 6, a cover substrate; and 7, a groove.
Information is recorded on or reproduced from the disc by
irradiation with laser beam light from the substrate 1 side. The
substrate 1 has a groove formed over the surface.
One of the features of such recording media as DVD+R and
CD-R that can be played on CD players is that the track information
is embedded in the form of wobbling grooves or pits.
The degree of wobbling can be detected as a wobble signal
from a track signal. Track information is previously recorded in the
substrate by modulating a given frequency by FM modulation or
phase modulation.
The track information includes address information and disc

rotation frequency information. When the wobble signal is to be
detected from the track signal, it is easy to distinguish the wobble
signal from information data signals and to obtain ROM signal
compatibility.
The present invention relates to the dye recording layer
materials described above. The optical recording medium of the
present invention is an optical recording medium having at least a
dye recording layer over a substrate which has at least one of
grooves and pits formed on a surface thereof, wherein the recording
layer comprises at least a cyanine dye represented by the foregoing
General Formula (I), a squaric acid complex represented by the
foregoing General Formula (II), and an amine compound.
Cyanine dyes represented by General Formula (I) and squaric
acid complexes represented by General Formula (II) have excellent
performance as recording materials for DVD.
In particular, among cyanine dyes represented by General
Formula (I), those represented by the following Formula (3) with
various combinations of substituents listed in Table 1, which have
PFG" as an anion, are generally used because their thermal
decomposition property is suitable for high-speed recording.
However, ions such as PF6 causes an increase in acidity of
coating solution when mixed with a squaric acid complex, thereby
dechelating the squaric acid complex.
Formula (3)


In Table 1 "Ph" denotes a phenyl group, "CH3" denotes a
methyl group, "Cl" denotes a chlorine atom, "i-Pr" denotes an
isopropyl group, "Cyclohexyl" denotes a six-member ring formed of
R3 and R4 combined together, and "Naphthyl" denotes a naphthyl
group formed together with a benzene ring.
Specific examples of squaric acid complexes represented by
For example, the No.l cyanine in Table 1 has a structure
represented by the Formula (4) below.
Formula (4)


General Formula (II) are compounds represented by the following
Formula (5) with various combinations of substituents listed in
Table 2.
Formula (5)



In Table 2 "Ph" denotes a phenyl group, "CF3" denotes a
trifluoromethyl group, "CH3" denotes a methyl group, "t-Bu" denotes
a tertiary butyl group, "i-Pr" denotes an isopropyl group,
"Cyclohexyl" denotes a six-member ring formed of R3 and R4
combined together, and "Naphthyl" denotes a naphthyl group
formed together with a benzene ring.
For example, the No.l and No.2 squaric acid complexes have
the structures represented by the Formulae (6) and (7), respectively.
The position of substituent R6 in the No.3 and No.7 compounds is
the same as in the Formula (7).
Formula (6)



To avoid dechelation, in the present invention, an amine
compound is added as a stabilizer.
Amine compounds are basic compounds which prevent
oxidation (dechelation).
Meanwhile, general solvents used for the preparation of
coating solution are fluorine-substituted alcohols such as 2,2,3,3-
tetrafluoropropanol, in light of their high solubility for the foregoing
dyes.
The acidity, water content, etc., of the solvent also influence
the amine's stabilizing capability. It is, however, difficult to control
these parameters and it results in high manufacturing costs. When
an amine compound is a solid, it is contained in the recording layer
by means of spin coating. For this reason, the content of amine
compound is preferably not greater than 10% by mass of dye; a too
high content influences the optical characteristics and
thermophysical properties of the recording layer, increasing the

likelihood of jitter increase in the recording signals.
Whereas a too low amine compound content makes it difficult
to obtain the stabilizing effect. A particularly preferred amine
compound content range with respect to dye is 0.5% by mass to 3%
by mass.
In addition, amine compounds having a nitrogen-containing
heterocyclic ring are preferable. Furthermore, amine compounds
with a melting point of 150°C or higher are preferable. The reason
for this is that those with a melting point of less than 150°C are
more likely to cause changes in characteristics (particularly optical
characteristics) of the light-absorbing layer when placed under high
temperature, high humidity conditions. Among those amine
compounds, imidazole, benzimidazole, and thiazole derivatives are
most preferable.
When the amine compound is a liquid present in a small
amount, the amine compound can be removed from the recording
layer either during the spin coating process or following heating
process.
Thus, the content of the liquid amine compound in coating
solution is preferably not greater than 10% by mass as has been
described above, because a content of 10% or more makes it difficult
to remove the amine compound.
There is no need to allow any amine compound to exist in the
resulting recording layer.

Tertiary amines (e.g., triethylamine and tripropylamine) are
preferably employed in the case of a liquid amine compound,
because this increases basicity of the coating solution and amine's
stabilizing capability.
A dye recording layer provided for example in a DVD+R disc
is generally produced by spin coating, a method that involves
dropwise application of coating solution onto a rotating substrate,
followed by removal or drying of solvent by further increasing the
rotational speed of the substrate. This method, however, can utilize
as small as 10% to 20% of the coating solution for film deposition
onto the substrate, and the rest of the coating solution remains in
the spin coating tank. Re-use of the tank content refers to as a "dye
recycle," wherein the tank content (liquid and solids) is again
dissolved in coating solvent to prepare a coating solution.
By allowing an amine compound to be present in the dye film,
it can also realize recycling of dyes while ensuring the stability of
coating solution.
Specific examples of amine compounds include n-butylamine,
n-hexylamine, tert-butylamine, pyrrole, pyrrolidine, pyridine,
piperidine, purin, imidazole, benzimidazole, 5,6-
dimethylbenzimidazole, 2,5,6-trimethylbenzimidazole,
naphthoimidazole, 2-methylnaphthoimidazole, quinoline,
isoquinoline, quinoxaline, benzoquinoline, phenanthridine, indoline,
carbazole, norharman, thiazole, benzothiazole, benzoxazole,

benzotriazole, 7-azaindole, tetrahydr'oquinoline, triphenylimidazole,
phthalimide, benzoisoquinoline-5,10-dion, triazine, perimidine, 5-
chlorotriazole, ethylenediamine, azobenzene, trimethylamine,
triethylamine, N,N-dimethylformamide, l(2H)-phthalazinone,
phthalhydrazide, 1,3-diiminoisoindoline, oxazole, polyimidazole,
polybenzimidazole, and polythiazole.
Conventional cyanine dyes can be employed without any
modification, examples of which are those disclosed in JP-B Nos.
2594443, 3698708, and 3659922.
In particular, as described above, compounds that have PF6
as an anion are suitable for high-speed, high-density recording
because they produce small amount of heat when thermally
decomposed.
Conventional squaric acid complexes can be employed, as can
the cyanine dyes, and examples of such squaric acid complexes are
those disclosed in International Publication No. 2002/050190 and
JP-A No. 2004-244342.
(Layer Configuration)
Hereinafter, materials of other layers provided in the optical
recording medium of the present invention will be described in
detail.
Materials of the substrate used in the present invention can
be selected from any materials for use in substrates for conventional
recording media; examples include acrylic resins such as

polymethylmethacrylate, vinyl chloride resins such as polyvinyl
chloride and polyvinyl chloride copolymers, epoxy resins,
polycarbonate resins, amorphous polyolefins, polyesters, glass such
as soda-lime glass, and ceramics.
Among these, polymetylmethacrylate, polycarbonate resins,
epoxy resins, amorphous polyolefins, polyesters, and glass are
preferable in view of their shape stability, transparency, and the
ease with which they can be flattened.
Furthermore, polycarbonate resins are more preferable in
view of their moldability.
A surface of the substrate over which an optical recording
layer is to be deposited may be provided with an undercoat layer for
the purpose of improving flatness, enhancing adhesive property, and
preventing degradation of the optical recording film.
Examples of materials of the undercoat layer include
polymers such as polymethylmethacrylate, acrylic acid/methacrylic
acid copolymers, styrene/ maleic acid anhydride copolymers,
polyvinyl alcohol, N-methylolacrylamide, styrene/vinyl sulfonic acid
copolymers, styrene/vinyl toluene copolymers, chlorosulfonated
polyethylene, nitrocellulose, polyvinyl chloride, chlorinated
polyolefins, polyesters, polyimides, vinyl acetate/vinyl chloride
copolymers, ethylene/vinyl acetate copolymers, polyethylene,
polypropylene, and polycarbonates; organic materials such as silane
coupling agents; inorganic oxides such as SiO2 and AI2O3; and

inorganic materials such as inorganic fluorides such as MgF2. Note
that the undercoat layer generally ranges from 0.005μm to 20μm in
thickness, preferably from 0.01μm. to 10μm.
A pre-groove layer may be formed over the substrate or
undercoat layer for the purpose of forming a tracking groove or a
pattern of concaves and convexes that represents information such
as address signal.
Examples of available materials of the pre-groove layer
include a mixture of a photoinitiator and at least one monomer (or
oligomer) selected from a monoester, diester, triester, and tetraester
of acrylic acid.
Moreover, a reflective layer is provided over the optical
recording layer for the purpose of increasing the S/N ratio,
reflectance, and sensitivity upon recording. Light reflective
materials used for manufacture of the reflective layer are materials
that reflect laser beam light to a great extent; examples include
metals and semi-metals such as M.g, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr,
Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al,
Ca, In, Si, Ge, Te, Pb, Po, Sn, Si, and Nd.
Among these, Au, Al, and Ag are preferable. These metals
and semi-metals may be used singly or in combination or as an alloy.
Note that the reflective layer generally ranges from 100A to 3,000A
in thickness.
A protective layer is provided over the optical recording layer

(or reflective layer) in order to protect the optical recording layer
and the like physically and chemically.
This protective layer may be provided to the other side of the
substrate where no light absorbing layer is provided, for increasing
scratch resistance and wet resistance. Examples of materials of the
protective layer include inorganic materials containing for example
SiO, SiO2, MgF2, SnO2, ZnS, or ZnO as a main ingredient,
thermoplastic resins, thermosetting resins, and UV-curable resins.
Note that the protective layer generally ranges from 500A to 50μm
in thickness.
In addition to the foregoing dye materials — cyanine dyes,
squaric acid complexes and araine compounds, additional
ingredient(s) may be added where necessary for the purpose of
improving light stability, optical characteristics, temperature
resistance, wet resistance, etc.
Examples of the additional ingredient include cyanine dyes,
phthalocyanine dyes, pyrylium dyes, thiopyryliium dyes, azulenium
dyes, squaric acid dyes, azo dyes, formazan chelate dyes, metal (e.g.,
Na and Cr) complex dyes, naphthoquinone dyes, anthraquinone dyes,
indophenol dyes, indoaniline dyes, triphenylmethane dyes,
triallylmethane dyes, aminium dyes, diimmonium dyes, and nitroso
dyes.
The method of the present invention for manufacturing an
optimal recording medium will be described below. In the method of

the present invention for manufacturing an optical recording
medium with, a DVD-R disc configuration is characterized in that (l)
an optical recording layer containing the dye compounds (I) and (II)
and amine compound as main ingredients is provided on a surface of
a substrate by coating means either directly or with a layer
interposed between them, the surface having at least one of grooves
and pits thereon, (2) a reflective layer is provided over the optical
recording layer by means of vacuum deposition either directly or
with a layer is interposed between them, and (3) a protective layer
is provided over the optical recording layer.
That is, the method according to the present invention for
manufacturing an optical recording medium comprises (l) providing
an optical recording layer containing the dye compounds (I) and (II)
and amine compound as main ingredients on a surface of a
substrate by coating means either directly or with a layer
interposed between them, the surface having at least one of grooves
and pits thereon,' (2) providing a reflective layer over the optical
recording layer by means of vacuum deposition either directly or
with a layer interposed between them; and (3) providing a protective
layer over the optical recording layer.
(Optical Recording Layer Formation Step)
In the first step of the method of the present invention, an
optical recording layer containing the dye compounds (I) and (II)
and amine compound as main ingredients is provided on a surface of

a substrate by coating means either directly or with a layer
interposed between them, the surface having at least one of grooves
and pits thereon. To be more specific, the dye compounds (I) and
(II) and amine compound are dissolved into a solvent to produce a
coating solution, which is then applied over the substrate to form
the optical recording layer.
Solvents that can be used for the preparation this coating
solution are known organic solvents such as alcohols, cellosolves,
halogenated carbons, ketones, and ethers.
Moreover, spin coating is a preferable coating method
because it is possible to control the layer thickness by adjusting the
concentration and viscosity of the optical recording layer and the
drying temperature of the solvent.
A surface of the substrate over which the optical recording
layer is to be deposited is provided with an undercoat layer for the
purpose of improving flatness, enhancing adhesive property, and
preventing degradation of the optical recording film.
This undercoat layer can be formed by dissolving or
dispersing any of the foregoing materials for undercoat layer into an
suitable solvent and by applying the resultant coating solution over
the substrate by technique such as spin coating, dip coating, or
extrusion coating.
(Optical Reflective Layer Formation Step)
In the second step of the method of the present invention, a

reflective layer is provided over the optical recording layer by
vacuum deposition either directly or with a layer interposed
between them. To be more specific, the reflective layer is deposited
over the optical recording layer by vapor deposition, sputtering, or
ion plating of any of the foregoing light reflective materials.
(Protective Layer Formation Step)
In the third step in the method of the present invention, a
protective layer is provided over the reflective layer. To be more
specific, the protective layer can be formed by vacuum deposition or
application of any of the foregoing materials for protective layer,
including inorganic materials and various types of resins; It is
particularly preferable to adopt UV-curable resin; the protective
layer is formed by applying UV-curable resin by spin coating
followed by application of UV to cure the resin.
Example
The present invention will be described with reference to
Examples and Comparative Example, which however shall not be
construed as limiting the invention thereto.
(Example l)
A substrate with a pattern of grooves (depth = approximately
l,600A, width = approximately 0.24μm, track pitch = 0.74μm)
formed on a polycarbonate disc (diameter = 120mm, thickness =
0.6mm) was prepared. Subsequently, the No.l dye in Table 1

(Cyanine Dye (I)), the No.2 dye in Table 2 (Squaric Acid Complex
(II)), and 5,6-dimethylbenzimidazole (Amine Compound) were mixed
together in 2,2,3,3-tetrafluoropropanol to produce a coating solution
for dye recording layer.
The dye compounds were dissolved in the solvent by stirring
at 60°C for 5hr, and the obtained coating solution was applied by
spin coating and annealed at 90°C for 15min to form a dye recording
layer of about 800A thickness.
The dye concentration was set to 1.0%, and the Dye (l):Dye
(2): Amine Compound ratio was set to 60:39:1 (by mass). The
optical absorption spectrum of the coating solution is shown in FIG.
3.
A reflective layer was then deposited on the recording layer by
sputtering of a Ag alloy (Ag/IN .= 99.5/0.5) to a thickness of l,400A
using Ar gas as sputtering gas.
A protective layer made of UV-curable resin was formed on
the reflective layer to a thickness of about 4μm to fabricate a disc-
shaped article, which was then bonded to a polycarbonate cover
substrate of similar shape with a UV-curable resin adhesive. In
this way a DVD+R disc was manufactured.
The recording medium was evaluated using disc evaluation
equipment (ODU-1000 and DDU-1000 by PulseTec) under the
evaluation conditions described below.
(Signal Recording)

DVD(8-16) signals were recorded under the following
condition: laser wavelength = 659nm, lens NA = 0.65, recording
linear velocity = 16x (55.8 m/s). A write strategy based on the
DVD+R standards was adopted.
(Signal Recording)
The disc was played on a DVD-ROM player (lens NA = 0.60,
laser wavelength = 650nm) at Ix (3.5 m/s), measuring the jitter of
pit edge-clock (σ/T) by Time Interval Analyzer. In addition,
reflectance to reflection signals was measured. It succeeded in
obtaining such excellent signal characteristics that σ/T was 7.2%
and reflectance was 48%.
(Comparative Example l)
An optical recording medium was manufactured as in
Example 1 except that no amine compound was added, and a similar
signal evaluation was made. The optical absorption spectrum of the
dye coating solution prepared upon manufacture of this optical
recording medium is shown in FIG. 3, which is different from that of
the dye coating solution prepared in Example 1.
The result of the signal evaluation was as follows: σ/T was
9.5% and reflectance was 41%. This means that signal
characteristics of Comparative Example 1 was poor compared to
Example 1 (i.e., σ/T increased and reflectance decreased), resulting
in failure to meet the DVD+R standards.
(Example 2)

Preparation of dye coating solution was conducted as in
Example 1 except that dye coating solutions containing different
amounts of amine compound (0.5, 2, 3, 5, 8, and 10 wt%) were
prepared, and their optical absorption spectra were measured. It
turned out that the absorption spectra were similar to that obtained
in Example 1.
(Example 3)
A dye coating solution was prepared as in Example 1 except
that the amine compound was changed from 5,6-
dimethylbenzimidazole to triethylamine, and the optical absorption
spectrum was measured. As shown in FIG. 3, it turned out that the
optical absorption spectrum was similar to that obtained in
Example 1. Also, it succeeded in obtaining such excellent signal
characteristics that σ/T was 7.5% and reflectance was 48%.
(Example 4)
A DVD+R disc was manufactured as in Example 1 except that
the amine compound was changed from 5,6-dimethylbenzimidazolo
to triethylamine, and the absorption spectrum was measured. It
succeeded in obtaining such excellent signal characteristics that σ/T
was 7.5% and reflectance was 48%.
(Examples 5 to 10)
DVD+R media were manufactured as in Example 4 except
that compounds and their ratios listed in Examples 5 to 10 of Table
3 were adopted, and then signal evaluations were made.

The evaluation results shown in Table 3 indicate that all of
the DVD discs prepared in Examples 5 to 10 offered excellent signal
characteristics.
Note in Table 3 that the cyanine dye number "No."
corresponds to the dye number of Table 1, the squaric acid complex
number "No." corresponds to the dye number of Table 2, "DMBi"
stands for 5,6-dimethylbenzimidazole, "Bi" stands for benzimidazole,
and "TEA" stands for tetraethylamine.

A DVD+R disc was manufactured as in Example 1 except that
the anion of the cyanine dye was changed to C104", and then a signal
evaluation was made. The evaluation result shown in Table 3
indicates that it succeeded in obtaining excellent signal
characteristics.

CLAIMS
1. An optical recording medium comprising-
a substrate having at least one of grooves and pits on a
surface thereof and
a dye recording layer formed over the substrate,
wherein the dye recording layer comprises a cyanine dye
represented by the following General Formula (I), a squaric acid
complex represented by the following General Formula (II), and an
amine compound:
General Formula (I)

wherein R1 and R2 independently represent an alkyl group which
may be substituted, an aryl group which may be substituted, or a
benzyl group which may be substituted, Z represents an atom group
for forming an aromatic ring, X represents a monovalent anion, and
L represents a linking group for forming a carbocyanine,
General Formula (II)


wherein R1 and R2, which may be identical or different, are an alkyl
group which may be substituted, an aralkyl group which may be
substituted, an aryl group which may be substituted, or a
heterocyclic ring which may be substituted, Q represents a metal
atom which has a coordinating property, q represents an integer of 2
or 3, and A represents an aryl group which may be substituted, a
heterocyclic ring which may be substituted, or Y=CH- (where Y
represents an aryl group which may be substituted or a heterocyclic
ring which may be substituted).
2. The optical recording medium according to claim 1, wherein
the cyanine dye in the recording layer has PF6- as an anion.
3. The optical recording medium according to claim 1, wherein
the content of the amine compound in the recording layer is 10% by
mass or less.
4. The optical recording medium according to one of claims 1 and
2, wherein the amine compound is a nitrogen-containing
heterocyclic compound.
5. A method for manufacturing an optical recording medium,

comprising-
applying over a surface of a substrate a solvent in which at
least a cyanine dye represented by the following General Formula
(I), a squaric acid complex represented by the following General
Formula (II), and an amine compound are dissolved, to thereby form
a dye recording layer over the substrate,
wherein the optical recording medium comprises the substrate
having at least one of grooves and pits on a surface thereof, and the
dye recording layer over the substrate-
General Formula (I)

wherein R1 and R2 independently represent an alkyl group which
may be substituted, an aryl group which may be substituted, or a
benzyl group which may be substituted, Z represents an atom group
for forming an aromatic ring, X represents a monovalent anion, and
L represents a linking group for forming a carbocyanine,
General Formula (II)


wherein R1 and R2, which may be identical or different, are an alkyl
group which may be substituted, an aralkyl group which may be
substituted, an aryl group which may be substituted, or a
heterocyclic ring which may be substituted, Q represents a metal
atom which has a coordinating property, q represents an integer of 2
or 3, and A represents an aryl group which may be substituted, a
heterocyclic ring which may be substituted, or Y=CH- (where Y
represents an aryl group which may be substituted or a heterocyclic
ring which may be substituted).
6. The method for manufacturing an optical recording medium
according to claim 5, wherein the amine compound is a liquid
tertiary amine.
7. The method for manufacturing an optical recording medium
according to one of claims 5 and 6, wherein the solvent is a fluorine-
substituted alcohol.

To provide an optical recording medium
including: a substrate having at least one of grooves and pits on a surface thereof; and
a dye recording layer formed over the substrate, wherein the dye recording layer comprises
a cyanine dye represented by the following General Formula (I), a squaric acid complex
represented by the following General Formula (II), and an amine compound.

Documents:

3450-KOLNP-2008-(18-04-2013)-CORRESPONDENCE.pdf

3450-KOLNP-2008-(18-04-2013)-FORM 3.pdf

3450-KOLNP-2008-(22-01-2014)-CORRESPONDENCE.pdf

3450-KOLNP-2008-(22-01-2014)-FORM-13.pdf

3450-KOLNP-2008-(22-01-2014)-FORM-5.pdf

3450-KOLNP-2008-(22-01-2014)-OTHERS.pdf

3450-KOLNP-2008-(31-01-2013)-ABSTRACT.pdf

3450-KOLNP-2008-(31-01-2013)-ANNEXURE TO FORM 3.pdf

3450-KOLNP-2008-(31-01-2013)-CLAIMS.pdf

3450-KOLNP-2008-(31-01-2013)-CORRESPONDENCE.pdf

3450-KOLNP-2008-(31-01-2013)-DESCRIPTION (COMPLETE).pdf

3450-KOLNP-2008-(31-01-2013)-DRAWINGS.pdf

3450-KOLNP-2008-(31-01-2013)-FORM-1.pdf

3450-KOLNP-2008-(31-01-2013)-FORM-2.pdf

3450-KOLNP-2008-(31-01-2013)-OTHERS.pdf

3450-KOLNP-2008-(31-01-2013)-PA.pdf

3450-KOLNP-2008-(31-01-2013)-PETITION UNDER RULE 137-1.pdf

3450-KOLNP-2008-(31-01-2013)-PETITION UNDER RULE 137.pdf

3450-kolnp-2008-abstract.pdf

3450-kolnp-2008-assignment.pdf

3450-kolnp-2008-claims.pdf

3450-KOLNP-2008-CORRESPONDENCE-1.1.pdf

3450-kolnp-2008-correspondence.pdf

3450-kolnp-2008-description (complete).pdf

3450-kolnp-2008-drawings.pdf

3450-kolnp-2008-form 1.pdf

3450-kolnp-2008-form 18.pdf

3450-KOLNP-2008-FORM 3-1.1.pdf

3450-kolnp-2008-form 3.pdf

3450-kolnp-2008-form 5.pdf

3450-kolnp-2008-international publication.pdf

3450-kolnp-2008-international search report.pdf

3450-kolnp-2008-pa.pdf

3450-kolnp-2008-pct priority document notification.pdf

3450-kolnp-2008-pct request form.pdf

3450-KOLNP-2008-PETITION UNDER RULE 137.pdf

3450-kolnp-2008-specification.pdf

abstract-3450-kolnp-2008.jpg


Patent Number 259356
Indian Patent Application Number 3450/KOLNP/2008
PG Journal Number 11/2014
Publication Date 14-Mar-2014
Grant Date 10-Mar-2014
Date of Filing 25-Aug-2008
Name of Patentee RICOH COMPANY, LTD.
Applicant Address 3-6, NAKAMAGOME 1-CHOME, OHTA-KU TOKYO
Inventors:
# Inventor's Name Inventor's Address
1 YASHIRO, TOHRU 22-26-4, NEGISHI-CHO, YOKOSUKA-SHI, KANAGAWA 239-0807
2 MIZUKAMI, SATOSHI COSMO HILLS SAGAMIONO 703, 7-24-15, SAGAMIONO, SAGAMIHARA-SHI, KANAGAWA 228-0803
PCT International Classification Number B41M 5/26,G11B 7/244
PCT International Application Number PCT/JP2007/053234
PCT International Filing date 2007-02-15
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2007-023511 2007-02-01 Japan
2 2006-043599 2006-02-21 Japan