Title of Invention

RESIN ROLL FOR CALENDERING MAGNETIC RECORDING MEDIUM AND A METHOD OF MANUFACTURING THE SAME

Abstract The invention relates to resin roll for calendaring a magnetic recording medium and a method for manufacturing the same. The said resin roll comprising a metal roll core (1); and a thermosetting resin outer layer (3); wherein a surface portion of the thermosetting resin outer layer has a storage elastic modulus (E') from 5 x 1010, to 5 X 10" dyn/cm2 at a temperature from 50 to 150°C at a frequency of 10 Hz. The said method comprising the steps of: casting a mixture of a thermosetting resin raw material and an inorganic powder having average particle diameter of 0.05 to 50.0µm into a cylindrical mold for rotational casting, forming an outer layer hollow cylinder of a thermosetting resin containing at a surface portion the inorganic powder at a content of 60 to 95 percent by weight by rotational casting, fitting a metal roll core in the outer layer hollow cylinder and joining together the roll core and the outer layer hollow cylinder. PRICE: THIRTY RUPEES.
Full Text



BACKGROUND OF THE INVENTION Field of the Invention
The present invention relates to a resin roll for calendering a magnetic recording medium and to a method for manufacturing the same. Description of the Background Art
Generally, it is a wide spread practice in manufacturing a magnetic recording medium to apply a magnetic layer on a base film and to perform calendering thereafter.
Generally, in the process of manufacturing a magnetic recording medium, a magnetic recording medium is :alendered by running between a mirror-surfaced metal roll and an elastic roll such as a resin roll opposed to thereto while applying high nip pressure, so as to iliminate voids of the magnetic layer, to make smooth the urface of the magnetic recording medium and to increase ensity of the magnetic layer. In this case, the magnetic ayer side of the magnetic recording medium is brought nto contact with the metal roll.
Signal density of the magnetic recording medium has sen significantly improved recently. In order to obtain

a highly dense magnetic recording medium, it is necessary to apply a magnetic coating filled with magnetic powder to a high density on the base film so as to increase magnetic flux density. However, if the amount of the magnetic powder is increased, it becomes difficult to eliminate voids in the magnetic layer generated when solvent is dried, and it has been also difficult to obtain sufficient surface smoothness of the magnetic layer under the conventional conditions for calendering, because hardness of the magnetic coating could have been increased.
Accordingly, in order to make smooth the surface of the above described magnetic layer filled with magnetic powder to a high density and to eliminate voids perfectly, it,becomes necessary to apply higher temperature and higher nip pressure in the step of calendering.
Accordingly, there has been a demand for a resin roll for calendering which can be used at higher temperature and which can provide greater pressure.
The following characteristics are required of the resin roll for calendering.
(1) Satisfactory roll high surface smoothness.
(2) Hardness, especially high surface hardness.
(3) Heat resistance. Especially heat resistance to render the roll less likely to deform due to thermal expansion or melting that would result from autogenous

heat.
(4) Compression strength to withstand the high nip
pressure applied by the metal roll for the roll to remain
free of cracking or breaking.
(5) Free of pin holes in the roll.
However, in the conventional resin roll for
calendering a magnetic recording medium, roll properties are limited, so that nip width, that is, nip area tends to be unavoidably large. Therefore, in terms of applied pressure, that is, pressure per unit area acting on the nip surface, satisfactory pressure by unit area to meet the recent demand for high density magnetic recording medium could not be obtained. Further, in order to improve efficiency in processing, when heating is performed at higher temperature or when the press load is increased to obtain larger pressure by unit area, the nip width, that is, the nip area is further enlarged, making it difficult to obtain the effective pressure by unit area at the nip surface. SUMMARY OF THE INVENTION
An object of the present invention is to provide a resin roll for calendering a magnetic recording medium of which nip width is smaller than in the prior art under similar load, of which nip width is not increased even under high load at high temperature, thus providing

substantially larger pressure per unit area, of which surface is smooth and surface hardness is high, which has superior compression strength and heat resistance and which is free of pin holes.
Another object of the present invention is to provide a method of manufacturing the above described high performance resin roll for calendering a magnetic recording medium at low cost with high efficiency.
Still another object of the present invention is to provide a calendering apparatus employing the above described high performance resin roll as an elastic roll.
The above described objects of the present invention are attained by the resin roll for calendering a magnetic recording medium including a metal roll core and a thermosetting resin outer layer, wherein surface portion of the thermosetting resin outer layer has a storage elastic modulus (E') from 5 x 10 to 5 x 1010 dyn/cm2 at a temperature in the range from 50 to 150°C at a frequency of 10 hertz (Hz). More specifically, according to the present invention, the storage elastic modulus (E') of the surface portion of the thermosetting resin outer layer of the resin roll for calendering at a temperature of use is increased, whereby the nip width can be made smaller, and as the high storage elastic modulus (E') of the surface portion is maintained even at a high temperature, the

small nip width can be maintained.
Preferably, the storage elastic modulus (E') at the surface portion of the thermosetting resin outer layer of the roll should be at least 6 x 1010 dyn/cm2, and more preferably, it should be at least 8 x 1010 dyn/cm2. Preferably, it should be at most 2 x 1010 dyn/cm2, and more preferably, it should be at most 1.5 x 1011 dyn/cm2.
The conditions for measurement for temperature and frequency described above are set as close as possible to the conditions for use of the resin roll for calendering. The temperature is normally in the range from 50 to 150°C, which is preferably 50 to 180°C and, more preferably, 50 to 200°C.
The frequency is set to 10 hertz. This value is selected from the following reasons. If the outer, periphery of the resin roll for calendering is set to Im and the running speed to 300m/min, for example, the number of rotation of the roll is 300 rpm, and the frequency corresponding to this number of rotation is 5 Hz. However, if the resin roll for calendering is pinched between two metal rolls, the surface portion of the roll passes twice the nip per one rotation, and hence the frequency is set to 10 Hz.
In the foregoing, if the storage elastic modulus (E') at the surface portion of the thermosetting resin outer

layer of the resin roll for calendering is not higher than 5 X 1010 dyn/cm2, the nip width becomes too large, resulting in similar pressure per unit area as that of the prior art, and hence it is not preferable. If the storage elastic modulus (E') exceeds 5 x 1010 dyn/cm2, the nip width becomes smaller and larger pressure per unit area can be obtained. However, since the storage elastic modulus (E') is too large, ups and downs of the material to be processed cannot be absorbed by the roll surface, hindering uniform calendering. Therefore, it is not preferable.
The thermosetting resin constituting the outer layer of the resin roll for calendering includes, for example, epoxy resin, polyurethane resin, polyisocyanurate resin, cross linked polyesteramide resin, unsaturated polyester resin and diallylphthalate resin. In view of durability, heat resistance and moldability, epoxy resin and cross linked polyesteramide resin are preferable, and specifically, epoxy resin is desired.
The aforementioned metal roll core is made of a metal such as iron, steel, stainless steel or aluminum.
From another view point, the resin roll for calendering magnetic recording medium in accordance with the present invention includes a metal roll core and a thermosetting resin outer layer, wherein an expression (1

-v2)/E' representing relation between storage elastic modulus (E') and the Poisson's ratio (p) with respect to Hertz's equation representing nip width of the surface portion of the thermosetting outer layer is within the range of
5 X 10-11 cm2/dyn In the above expression, E' represents storage elastic modulus of the surface portion of the thermosetting resin outer layer of the resin roll, and v represents the Poisson's ratio of the surface portion.
Here, generally, it is known that the nip width when two rolls are in contact with and parallel to each other and subjected to a load (P) per unit length in axial direction can be represented by the Hertz's equation



where
N: nip width
Rl: radius of first roll
R2: radius of second roll
P: load power unit length
v1: Poisson's ratio of the first roll
v2= Poisson's ratio of the second roll
E] : elastic modulus of the first roll
E2: elastic modulus of the second roll
7: : the ratio of the circumference of a circle to its
diameter.
In the foregoing, if the first roll is the resin roll for calendering and the second roll is a metal roll, for example, it is understood that the nip width (N) is in proportion to a squire root of (K1 + K2) provided that the radii (R1 , R2) of both rolls and the load (P) are constant.
When the relation between the resin roll and the nip width is considered, the nip width (N) is influenced by the value of (1 - v2)/E1.
In other words, the smaller the value (1 - v2 )/E1 of

the surface of the resin roll, the smaller the nip width
(N).
The foregoing is a theory assuming a static
condition. When the roll in actual use is considered, the
slastic modulus (Ei) must be considered as a dynamic elastic modulus, that is, storage elastic modulus.
Conventionally, the importance of the relation between temperature and storage elastic modulus (E') of the resin roll for calendering have been recognized. However, the Poisson's ratio (v) has not been considered. Based on the theory described above, the inventors recognized that the relation between each of temperature, storage elastic modulus (E') and Poisson's ratio ( i/) is important, and through extensive study, they have found that the resin roll providing desirable nip width as a resin roll for calendering a magnetic recording medium has the value within the following range: 2 X 10-11 cm2/dyn
preferable.
Further, if the value of the expression (1 - i/2 )/E' exceeds 2 x 10- cm2/dyn, the nip width becomes too large, and only the pressure per unit area similar to that of the prior art can be obtained. Therefore, it is not preferable.
Preferably, the value of the expression (1 - i/2 )/E' should be at least 5 x lO-12 cm2/dyn, and more preferably, it should be at least 6 x 10-12 cm2/dyn. Preferably, it should be at most 1.8 x 10-12 cm2/dyn and, more preferably, it should be at most 1.5 x 10-12 cm2/dyn.
Here, the measuring condition of temperature is set to be 50 to 150°C as described above. Preferably, the temperature should be from 50 to 180°C, and more preferably from 50 to 200°C.
The frequency is set to 10 Hz from the same reason as described above.
According to the present invention, as the value of the expression (1 - y^)/'^' representing the relation between storage elastic modulus (E') and Poisson's ratio . ( V) at the surface portion of the thermosetting resin outer layer of the resin roll is small, the nip width can be made smaller, and as the value of the expression (1 - y 2)/E' is maintained at a small value' even at a high

temperature, small nip width can be maintained.
The thickness of thermosetting resin outer layer is, appropriately, from 5 to 50 mm.
In the resin roll for calendering a magnetic recording medium in accordance with the present invention, normally, the thermosetting resin outer layer is filled with inorganic powder, and the surface portion of thermosetting resin outer layer is uniformly filled with high percentage content of the inorganic powder. The percentage content of the inorganic powder at the surface portion of the resin outer layer is from 60 to 95 percent by weight.
Here, the inorganic powder includes carbon black, quartz powder, silica powder, silicon oxide, silicon carbide, glass powder, alumina, titanium oxide, potassium titanate, aluminum hydroxide, calcium carbonate, magnesium carbonate, talc, clay, glass beads, bentonite, iron powder, copper powder, aluminum powder and ferrite powder.
The average particle diameter of inorganic powder is from 0.05 to 50.0 um.
Since the surface portion of the thermosetting resin outer layer of the resin roll is uniformly filled with high percentage content of inorganic powder, the elastic roll comes to have high strength, high hardness, and high storage modulus, and hence the nip width can be made

smaller.
If the content of inorganic powder at the surface portion of the thermosetting resin outer layer of the resin roll is smaller than 60 percent by weight, necessary strength, hardness, or elastic modulus cannot be obtained. If the content of the inorganic powder exceeds 95 percent by weight, viscosity of slurry-like mixture of thermosetting resin material and inorganic powder becomes too high, making it difficult to cast the thermosetting resin outer layer of the roll, and also making it difficult to remove air during casting. As a result, pin holes would be generated in the thermosetting resin outer layer. Therefore, it is not preferable.
Preferably, the lower limit of the content of the inorganic powder is at least 6 5 percent by weight, and more preferably, it should be at least 70 percent by weight. The upper limit should preferably be at most 85 percent by weight, and more preferably, 8 0 percent by weight.
If the average particle diameter of the inorganic powder is smaller than 0.05 um, the viscosity of the slurry-like mixture of thermosetting resin raw material and inorganic powder becomes too high, making it difficult to cast the thermosetting resin outer layer of the roll, and also making it difficult to remove air during casting.

As a result, pin holes would be generated in the thermosetting resin outer layer. Therefore, it is not preferable. Further, if the average particle diameter of the inorganic powder exceeds 50.0 ^m, smoothness of the roll surface is degraded, and hence it is not preferable.
Preferably, the lower limit of average particle diameter of the inorganic powder should be at least 0.1 µm and more preferably, at least 0.3µm. The upper limit should preferably be at most 30 µm and, more preferably at most 10 µm.
The thickness of the surface portion of the thermosetting resin outer layer filled with high percentage content of inorganic powder should preferably be at least 0.5 mm, and more preferably, at least 1.0 mm.
Here, if the thickness of surface portion filled with high content of inorganic powder of the thermosetting resin outer layer is smaller than 0.5 mm, the nip portion would be influenced by the inner thermosetting resin layer which has lower hardness, and hence it is not preferable. Though there is not a specific upper limit in the thickness of the surface portion filled with high content of inorganic powder of the outer layer, the thickness at most 20 mm may be appropriate.
Further, in the resin roll for calendering a magnetic recording medium in accordance with the present invention.

the hardness of the surface portion of the thermosetting resin outer layer is not smaller than 95° and smaller than 100° in terms of shore D hardness.
If the hardness of the surface portion of the thermosetting resin outer layer is smaller than 95° in terms of shore D hardness, the nip width becomes,too large to provide satisfactory pressure per unit area. The hardness should preferably be at least 96° . Strictly speaking, it is not possible to have the hardness of 100° . However, the hardness should desirably be as close as 100° .
In the resin roll for calendering a magnetic recording medium is in accordance with the present invention, generally, surface roughness (Ra) at the surface portion of the thermosetting resin outer layer is in the range of not more than 0.5 µm, preferably not more than 0.2 µm and desirably, not more than 0.1 µm. Here, the surface roughness (Ra) means the arithmetical mean roughness (Ra) defined by JIS (Japanese Industrial Standard) B0601. The surface portion of the thermosetting resin outer layer should be as smooth as possible. However, in practice, it is difficult to make the surface roughness (Ra) at the surface portion of the resin outer layer to be smaller than 0.01 µm. If the surface roughness (Ra) at the surface portion of the thermosetting

resin outer layer exceeds 0.5 µm, the smoothness of the roll surface is degraded, making it impossible to make smooth the surface of the magnetic recording medium. Therefore, it is not preferable.
The resin roll for calendering a magnetic recording medium in accordance with the present invention is further provided with a fiber-reinforced lower winding layer
formed of a fiber material impregnated with a thermosetting resin on an outer peripheral surface of the metal roll core. The fiber-reinforced lower winding layer is formed by a fiber material impregnated with a thermosetting resin around the metal roll core.
The fiber material to be used may be made of an inorganic fiber or an organic fiber. It is desirable to use an inorganic fiber such as glass fiber, carbon fiber or metal fiber, which is hard, has high ability of elastic recovery, exhibits good adhesion to resins and exhibits high fastening force. Also usable is an organic fiber such as polyamide fiber, aromatic polyamide fiber, polyimide fiber, polyester fiber, phenolic fiber or acrylic fiber.
The fiber material is in the form of a yarn, roving, cloth tape or the like. In view of strength of the roll obtained, it is desirable to use the cloth tape or the
•roving and cloth tape in combination.

Examples of the thermosetting resins for impregnating the fiber material are epoxy resin, unsaturated polyester resin, diallylphthalate resin, polyurethane resin and the like. Such thermosetting resins include both thermosetting-type resin and cold setting-type resin.
A filler in the form of inorganic powder such as quartz, glass beads, hydrated alumina, clay powder, silica powder or calcium carbonate may be used as admixed with the thermosetting resin. The average particle diameter of the inorganic powder should be form 1 to 200 µm, and preferably from 5 to 100 µrn. Here, powder having the average particle diameter of smaller than 1 µm is not readily available, leading to higher cost. Therefore, it is not preferred. Further, if it exceeds 200 µm, uniform dispersion in resin becomes difficult.
A non-woven fabric is also usable for the lower winding layer. For example, on an outer peripheral surface portion of the aforementioned cloth tape or of the roving and cloth tape impregnated with filler-contained thermosetting resin, a layer of a non-woven fabric which is similarly impregnated with filler-mixed thermosetting resin may be wound around to be fitted over and joined together, to serve as the lower winding layer.
Such a non-woven fabric has the excellent function of holding the inorganic material as uniformly incorporated

therein in its entirety. The non-woven fabric to be used is made of an organic fiber such as acrylic fiber, polyester fiber or phenolic fiber, or an inorganic fiber such as glass fiber or metal fiber. Preferably, the non-woven fabric is in the form of a tape.
The lower winding layer is 1 to 50 mm in overall thickness. If less than 1 mm in thickness, the layer is insufficient in strength, exerts a smaller fastening force on the roll core, and therefore it is not suitable to use. On the other hand, if the thickness exceeds 50 mm, the layer will not have correspondingly increased strength but becomes more costly, and therefore it is undesirable. In view of the strength of the roll, the fastening force of the roll core and the like, the thickness of the lower winding layer is preferably in the range of 2 to 15 mm.
In this manner, the lower winding layer formed on the outer peripheral surface of the roll core is positioned between the roll core and the thermosetting resin outer layer and has a function of realizing good fitting and joining of these two and it also has a function of preventing separation from the roll core as it reinforces the fastening force to the roll core.
The above described objects of the present invention can be attained by the method of manufacturing a resin roll for calendering a magnetic recording medium in which

a slurry-like mixture of thermosetting resin raw material and an inorganic powder having the average particle diameter of from 0.05 to 50.0 µm is cast to a cylindrical mold for rotational casting, an outer layer hollow cylinder of the thermosetting resin containing at its surface portion the inorganic powder at the content of 60 to 95 percent by weight is formed by rotational casting, a metal roll core is fitted in the outer layer hollow Cylinder, and the roll core and the outer layer hollow cylinder are fitted and joined together.
Here, preferably, an adhesive is injected to annular clearance between the metal roll core and the outer layer hollow cylinder and the adhesive is cured so that the roll core and the outer layer hollow cylinder are bonded together by the adhesive layer.
Preferably, the method of manufacturing a resin roll for calendering a magnetic recording medium in accordance with the present invention includes the step of forming a fiber-reinforced lower winding layer formed of the aforementioned fiber material impregnated with the thermosetting resin on an outer peripheral surface of the metal roll core.
The method of manufacturing the resin roll for calendering a magnetic recording medium in accordance with the present invention will be described with reference to

the figures.
First, as shown in Fig. 1, a fiber material impregnated with the thermosetting resin is wound to a prescribed thickness on an outer peripheral surface of a metal roll core (1), thus forming a fiber-reinforced lower winding layer (2), The metal roll core (1) is formed on a metal such as stainless steel, and it is desirable to make the outer periphery thereof rough-surfaced by sandblasting or by forming a multiplicity of helical grooves, since the rough-surface promotes tight joining of the roll core (1) and the lower winding layer (2).
Separate from the above, an outer layer hollow :ylinder (3) of a thermosetting resin shown in Fig. 2 is arepared. This is formed by casting a slurry-like mixture 3f the thermosetting resin raw material and an inorganic powder having average particle diameter of 0.05 to 50.0 µm to a cylindrical mold for rotational casting, performing rotational casting so that the surface portion (3a) comes •o contain the inorganic powder at a prescribed content, .nd curing the thermosetting resin at a prescribed emperature. Thus, the outer layer hollow cylinder (3) of he thermosetting resin is formed.
The curing temperature of the thermosetting resin is etermined dependent on the type of the resin used. If he resin is thermo-setting type one, the curing

temperature is generally from 100 to 300°C, and if the resin is cold-setting type one, reaction and curing takes place at a room temperature.
In this manner, by rotational casting, the thermosetting resin outer layer (3) containing at its surface portion (3a) the inorganic powder at a prescribed ratio having superior surface smoothness, high surface hardness, superior compression strength and heat resistance and being free of pin holes can be obtained. Thereafter, as shown in Fig. 3, the thermosetting resin outer layer (3) is fitted around the metal roll core (1) having the fiber-reinforced lower winding layer (2), an adhesive is injected to annular clearance formed between the lower winding layer (2) and the outer layer hollow cylinder (3), the adhesive is cured at a prescribed temperature, fiber-reinforced lower winding layer (2) and the outer layer hollow cylinder (3) are fitted and bonded together by the adhesive layer (4), and thus the resin roll (5) for calendering a magnetic recording medium in accordance with the present invention is manufactured.
Examples of usable adhesives are those of epoxy resin type, unsaturated polyester resin type, diallylphthalate resin type or the like, in view of heat resistance, pressure resistance and so on.
The adhesive is cured at a temperature usually of 20

to 150°C. It is especially desirable to set the curing temperature of the adhesive to be approximately the same as the surface temperature of the resin roll (5) for calendering a magnetic recording medium during use.. The reason for this is that this eliminates the residual stress of the thermosetting resin outer layer (3) when the resin roll (5) is in use, rendering the thermosetting resin outer layer (3) more resistant to breaking even when subjected to high pressure.
In the resin roll for calendering a magnetic recording medium in accordance with the present invention described above, the surface porion of the thermosetting resin outer layer has high storage elastic modulus (E') from 5 X 10"' to 5 x 10^^ dyn/cm2 at a temperature from 50 to 150°C with the frequency of 10 hertz (Hz), and the value of the expression (1 - p^)/E' representing the relation between the storage elastic modulus (E') and Poisson's ratio (V ) has a value as low as
2 X 10-11 cm2/dyn
the surface of the magnetic recording medium and to surely perform processing such as increase in density of the magnetic layer by passing a recording medium through the rolls while applying high nip pressure.
According to the method of manufacturing a resin roll for calendering a magnetic recording medium in accordance with, the present invention, a mixture of a thermosetting resin raw material and an inorganic powder is molded by rotational casting, so that an outer layer hollow cylinder of the thermosetting resin containing, at its surface portion, inorganic powder at a high percentage content. Therefore, the resin roll for calendering a magnetic recording medium can be manufactured at low cost with high efficiency, and the obtained resin roll for calendering has,smooth surface, high surface hardness, superior compression strength and heat resistance and is free of pin holes. Therefore, the resin roll thus obtained is suitable for manufacturing the magnetic recording medium. The calendering apparatus for the magnetic recording medium in accordance with the present invention per:&orms surface processing of the magnetic recording medium by nip pressure between a metal roll and an elastic roll, and as the elastic roll, the above described high performance resin roll is used. According to one aspect, the elastic roll includes a metal roll core and a thermosetting resin

outer layer, and the surface portion of the thermosetting resin outer layer has a storage elastitcmodulus (E') of -5 X lO to 5 X 10 dyn/cm2 at the temperature of from 50 to 150°C at the frequency of 10 Hz. According to another aspect, the elastic roll includes a metal roll core and a thermosetting resin outer layer, and at the surface portion of the thermosetting resin outer layer, the expression (1 - v2)/E' representing the relation between storage elastic modulus (E') and Poisson's ratio (v) related to Hertz's equation representing the nip width is within the range of
2 X 10-12 cm2/dyn
Accordingly, the present invention provides a resin roll for calendering a magnetic recording medium, comprising:
a metai roll core; and
a thermosetting resin outer layer, wherein
a surface portion of the thermosetting resin outer layer has a storage elastic modulus (E) from 5 x 1010 to 5 x 10 dyn/cm2 at a temperature from 50 to 150oC at a frequency of 10 Hz.
Accordingly, the present invention also provides a method of manufacturing a resin roll for calendering a magnetic recording medium as described above, comprising the steps of:
casting a mixture of a thermosetting resin raw material and an inorganic powder having average particle diameter of 0.05 to 50.0 µm into a cylindrical mold tor rotational casting forming an outer layer hollow cylinder of a thermosetting resin containing at a surface portion the inorganic powder at a content of 60 to 95 percent by weight by rotational casting, fitting a metal roll core in the outer layer hollow cylinder and joining together the roll core and the outer
layer hollow cylinder.



The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partially omitted cross sectional view of a roll core with a lower winding layer.
Fig. 2 is a partially omitted cross sectional view of a thermosetting resin outer layer.
Fig. 3 is a partially omitted cross sectional view of a resin roll for calendering a magnetic recording medium




in accordance with the present invention.
Fig. 4 is a graph showing relation between temperature of use and storage elastic modulus (E') at a surface portion of a thermosetting resin outer layer of small size test rolls in accordance with embodiments of the present invention and examples for comparison.
Fig. 5 is a graph showing relation between temperature of use and expression (1 - z/^-)/E' representing relation between storage elastic modulus (E') and Poisson's ratio { i/) at the surface portion of the thermosetting resin outer layer of the small size test rolls in accordance with embodiments of the present invention and examples for comparison.
Fig. 6 is a graph showing relation between the nip width and load of small size test rolls in accordance with embodiments of the present invention and examples for comparison. DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described, with reference to examples for comparison.
[Inventive Example 1]
The resin roll (5) for calendering a magnetic recording medium in accordance with the present invention shown in Fig. 3 was prepared by the following method.
First, as shown in Fig. 1, an iron roll core (1)

having a length of 1200 mm, surface length of 550 mm and outer diameter of 300 mm was rough-surfaced over the outer periphery by sandblasting, and a fiber material impregnated with epoxy resin was wound around the outer periphery of the roll core (1) to form a fiber-reinforced lower winding layer (2) having the thickness of 4 mm. The fiber-reinforced lower winding layer (2) was formed by winding a glass cloth tape impregnated with epoxy rfesin mixed with silica powder on a peripheral surface of roll core (1), and thereafter winding a glass roving impregnated with the similar epoxy resin of the outer periphery of the tape layer. The epoxy resin was cured at 110°C.
Then, separate from the above, a mixture including epoxy resin raw material containing 100 parts by weight of resin and 52 parts of weight of a hardener mixed with 120 parts by weight of silica powder having average particle diameter of 0.5 /jm was cast to a cylindrical mold for rotational casting (not shown), rotational casting was performed at a mold temperature of 80°C and a number of rotation of 1500 rpm, and thus outer layer hollow cylinder (3) of epoxy resin containing at its surface portion (3a) a prescribed high percentage content of silica powder was prepared. The hollow cylinder (3) taken out from the mold was subjected to post curing at a temperature of 90 to

180°C, outer peripheral surface and inner peripheral surface of the outer layer hollow cylinder (3) of epoxy resin were cut, and thus the outer layer hollow cylinder (3) of epoxy resin shown in Fig. 2 having the outer ' diameter of 340 mm, the inner diameter of 309 mm, and the length of 400 mm was prepared.
The outer layer hollow cylinder (3) of epoxy resin was fitted around the roll core (1) having the lower winding layer (2), an adhesive mainly consisting of epoxy resin was injected to annular clearance formed between the lower winding layer (2) and the outer layer hollow cylinder (3), the adhesive was cured at the temperature of 80°C, the lower winding layer (2) and the outer layer hollow cylinder (3) of epoxy resin were bonded together by an adhesive layer (4) having the thickness of 0.5 mm, the outer peripheral surface of the roll was cut and polished, whereby the resin roll (5) for calendering a magnetic recording medium shown in Fig. 3 was manufactured. The resin roll (5) had the outer diameter of 335 mm and the surface length of 400 mm.
[Inventive Example 2]
The resin roll (5) for calendering a magnetic recording medium in accordance with the present invention was manufactured in the similar manner as Inventive Example 1 described above.

First, as in Inventive Example 1, a fiber material impregnated with epoxy resin was wound around the outer peripheral surface of iron roll core (1) to form a fiber-reinforced lower winding layer (2) having the thickness of 4 mm.
Then, separate from the above, a mixture including 100 parts by weight of resin composition of 2.1 mole of bis(2-oxazoline) compound and 1.0 mole of dicarboxylic acid mixed with 1.6 parts by weight of phosphite and further mixed with 94.1 parts by weight of silica p6wder having average particle diameter of 10 /^m was cast to a cylindrical mold (not shown) for rotational casting in the similar manner as in Inventive Example 1 described above. Rotational casting was performed at a mold temperature of 130°C and a number of rotation of 800 rpm, thus an outer layer hollow cylinder (3) of cross linked polyesteramide resin containing at its surface portion (3a) a prescribed high percentage content of silica powder was prepared. The hollow cylinder (3) taken out from the mold was subjected to post curing at a temperature of 160°C, the outer peripheral surface and the inner peripheral surface of the outer layer hollow cylinder (3) were cut, and thus the outer layer hollow cylinder (3) shown in Fig. 2 having the outer diameter of 340 mm, inner diameter of 309 mm and the length of 400 mm was prepared.

The outer layer hollow cylinder (3) of cross linked polyesteramide resin was fitted over the roll core (1) having the lower winding layer (2), an adhesive mainly consisting of epoxy resin was injected to an annular clearance formed between the lower winding layer (2) and the outer layer hollow cylinder (3), the adhesive was ,cured at a temperature of 80°C, the lower winding layer (2) and the outer layer hollow cylinder (3) of cross linked polyesteramide resin were bonded together by the adhesive layer (4) having the thickness of 0.5 mm, the outer peripheral surface of the roll was cut and polished, whereby the resin roll (5) for calendering a magnetic recording medium shown in Fig. 3 was prepared. The resin roll (5) had the outer diameter of 335 mm and the surface length of 400 mm.
Performance Evaluation Test
In order to evaluate the performance of the resin rolls (5) for calendering a magnetic recording medium in accordance with Inventive Examples 1 and 2 above, small sized rolls for performance evaluation were manufactured using the same material and substantially the same conditions for respective rolls. Here, the iron roll core (1) had the size of the outer diameter of 192 mm, the surface length of 290 mm and the length of 760 mm, and the■ manufactured small resin roll (5) had the outer diai^eter

of 230 nun and effective surface length of 230 mm.
[Comparative Example 1]
For comparison, a small sized roll having the same size as above was manufactured by using the same material .and in the same manner as Inventive Example 2 above except that silica powder was not introduced.
[Comparative Example 2]
An iron roll core and a fiber reinforced lower winding layer similar to those of Inventive Example 1 were prepared, the roll core having the lower winding layer was set vertically in a mold for casting having a prescribed size, a mixture including an epoxy resin raw material consisting of 100 parts by weight of resin and 52 parts by weight of a hardener mixed with 79 parts by weight of silica powder having average particle diameter of 10.0 //m was directly injected on the outer side of the iron roll
>
core and cured, the roll outer periphery was cut and polished, thus a small sized roll for comparison test having the same size as described above was manufactured.
[Comparative Example 3]
An iron roll core and a fiber-reinforced lower winding layer similar to those of Inventive Example 1 were prepared. The roll core with lower winding layer was set vertically in a mold for casting having a prescribed size, a mixture including an epoxy resin raw material consisting

of 100 parts by weight of resin and 65 parts by weight of a hardener mixed with 50 parts by weight of silica powder having average particle diameter of 10.0 ^m was directly cast to the outside of the iron roll core in the mold and cured, the roll outer periphery was cut and polished, and thus a small sized roll for comparison test having the same size as described above was manufactured.
The relation between temperature and storage elastic modulus (E') of the surface portion of the thermosetting resin outer layer of each of the small sized test rolls in accordance with Inventive Examples 1 and 2 and the Comparative Examples 1 to 3 at the frequency of 10 Hz was measured by a viscoelastic spectrometer (manufactured by IWAMOTO SEISAKUSHO CO., LTD). The results obtained are shown in Tables 1 and 2 and the graph of Fig. 4.
Poisson's ratio (y) at the surface portion of each roll was measured in accordance with JIS K7054, and based on the measured values and the measured results of the aforementioned storage elastic modulus (E'), the value of the expression (1 - v )/E' representing the relation between storage elastic modulus (E') and Poisson'^s ratio (p) related to Hertz's equation representing the nip width at each temperature was calculated. The obtained results are as shown in Tables 1 and 2 and the graph of Fig. 5.
Thereafter, the content of silica powder at the

surface portion of the epoxy resin outer layer or the cross linked polyesteramide resin outer layer of the small sized test rolls were measured. The measurement of the content of silica powder was performed by taking a sample piece having the thickness of 1 mm from the surface portion of the resin outer layer of each of the small sized test rolls, and ash content measurement of each sample piece was performed. A thermo
gravimetry/differential thermal analyzer (manufactured by Seiko Instruments Inc.) was used for measurement. The obtained results are as shown in Table 1.
The hardness at the surface portion of the resin outer layer of each of the small sized test rolls was measured by a shore durometer (D type), and the surface roughness (Ra) at the surface portion of the resin outer layer was measured by using the surface texture measuring apparatus (manufactured by Tokyo Seimitsu). The obtained results are also shown in Table 1.
Further, nip widths of the small sized test rolls in accordance with Inventive Examples 1 and 2 and Comparative Examples 1 to 3 for performance evaluation test were measured.
The measurement of the nip widths was performed in the following manner. A steel roll having the outer diameter of 202 mm and effective surface length of 230 mm

was brought into contact with each roll, and aluminum foil (not shown) 15 µm in thickness was inserted between both rolls, three different loads of 100 kg/cm, 200 kg/cm and 300 kg/cm were applied between both rolls, and the widths of nipping trace transferred onto the aluminum foil were measured. The measurement was performed with the roll surface temperature of 50°C. The obtained results are as shown in the graph of Fig. 6.





As is apparent from Tables 1 and 2 and from the graph of Fig. 4, the small sized resin rolls for testing corresponding to Inventive Examples 1 and 2 exhibited as high storage elastic modulus (E') as 1.24 x lO11 to 1.08 x 1011 dyn/cm2 and 6.30 x 1010 to 5.21 x 1010 dyn/cm2 at a temperature of 50 to 150°C, while the small sized resin rolls for testing corresponding to Comparative Examples 1
. to 3 exhibited the storage elastic modulus as low as 3.77 x 10 to 2.90 X 1010 dyn/cm2, 4,01 x 10 to 3.01 x 10 dyn/cm2 and 3.41 x lO10 to 9.44 x 1010 dyn/cm2, respectively. Especially, the small sized resin roll for testing corresponding to Inventive Example 1 exhibited as high the storage elastic modulus (E') as 1.01 x lO11 dyn/cm2 at 180°C, and as high as 8.53 x lO10 dyn/cm2 was maintained even at 200°C.
As is apparent from Tables 1 and 2 and from the graph of Fig. 5, the value of the expression (1 - v2)/E' representing the relation between storage elastic modulus (E') and Poisson's ratio (v) in relation to Hertz's equation representing the nip width was as low as 7.36 x 10-12 to 8.45 x 10-11 cm2/dyn and 1.43 x 10-11 to 1.73 x 10-11 cm2/dyn at a temperature range of 50 to 150°, respectively, for the small sized resin rolls for testing
corresponding to Inventive Examples 1 and 2. The values

for the small sized resin rolls for testing corresponding to the Comparative Examples 1 to 3 were as high ,as 2.23 x 10-11 to 2.90 X 10-11 cm2/dyn, 2.17 x 10-11 to 2.89 x 10-11 cm2/dyn and 2.53 x 10-11 to 9.15 x 10-11 cm2/dyn, respectively. Further, the small sized resin roll for testing corresponding to Inventive Example 2 exhibited the value as low as 1.91 x lO-11 cm2/dyn at 180°C. The small sized resin roll for testing corresponding to Inventive Example 1 exhibited the low value of 9.04 x lO"'-'-'^ cm2/dyn at 180°C, and even at 200°C, it exhibited the low value of 1.07 X 10" cm /dyn. Further, as shown in the graph of Fig. 6, the smaller the value of the expression (1 - v2' )/E', the smaller the nip width.
As compared with the small sized resin rolls for testing corresponding to Comparative Examples 1 to. 3, the content of silica powder at the surface portion of the resin outer layer of the small sized resin rolls for testing corresponding to Inventive Examples 1 and 2 were higher and shore D hardness of the rolls corresponding to Inventive Examples were also higher.
As for the surface roughness (Ra) at the surface portion of the resin outer layer of the roll, the surface roughness of the small sized resin rolls for testing corresponding to Inventive Examples 1 and 2 were smaller as compared with the small sized resin rolls for testing

corresponding to Comparative Examples 2 and 3 containing .
silica powder. That is, the rolls corresponding to
Inventive Examples had superior surface smoothness.
Especially, the small sized resin roll for testing
corresponding to Inventive Example 1 used fine inorganic
powder having smaller average particle diameter, and hence
the surface roughness was at the same level as that of
Comparative Example 1 which was not filled with inorganic
powder.
As shown in the graph of Fig. 6, when the small sized
resin rolls for testing corresponding to Inventive
Examples were each brought into contact with the steel
roll and subjected to a load, smaller nip width can be
obtained and accordingly, substantially larger pressure
per unit area can be obtained. This is the same when the
roll has the size of the machine actually in operation.
Therefore, it is possible to make smooth the surface of a
magnetic recording medium and to surely perform process to
* increase density of magnetic layer or the like by passing
the magnetic recording medium between the resin roll for
calendering magnetic recording medium in accordance with
thia present invention and a steel roll while applying a
high nip pressure.
Although the present invention has been described and
illustrated in detail, it is clearly understood that the

same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of. the present invention being limited only by the terras of the appended claims.


WE CLAIM;
1. A resin roll for calendering a magnetic recording medium, comprising:
a metal roll core (1); and
a thermosetting resin outer layer (3); wherein
a surface portion of the thermosetting resin outer layer has a storage elastic modulus (E') from 5 x 1010 to 5 X 1011 dyn/cm2 at a temperature from 50 to 150°C at a frequency of 10 Hz.
2. The resin roll for calendering a magnetic
recording medium according to claim 1, wherein
the surface portion of the thermosetting resin outer layer is uniformly filled with a high percentage content of an inorganic powder.

3. The resin roll for calendering a magnetic recording
medium according to claim 2, wherein
content of the inorganic powder at the surface portion of the thermosetting resin outer layer is from 60 to 95 percent by weight.
4. The resin roll for calendering a magnetic
recording medium according to claim 2, wherein
average particle diameter of the powder is

from 0.05 to 50.0 pun.
5. The resin roll for calendering a magnetic recording medium according to
claim 1, wherein
hardness of the surface portion of the thermosetting resin outer layer is not lower than 95° and lower than 100o in terms of shore D hardness.
6. The resin roll for calendering a magnetic recording medium according to
claim 1, wherein
surface roughness (Ra) at the surface portion of the thermosetting resin outer layer is not more than 0.5µm.
7. The resin roll for calendering a magnetic recording medium according to
claim 1, wherein
a fiber-reinforced lower winding layer formed of a fiber material impregnated with a thermosetting resin is provided on an outer peripheral surface of the metal roll core.

8. A method of manufacturing a resin roll for calendering a magnetic
recording medium as claimed in claim 1, comprising steps of:
casting a mixture of a thermosetting resin raw material and an inorganic
powder having average particle diameter of 0.05 to 50.0 µm into a cylindrical
mold for rotational casting, forming an outer layer hollow cylinder of a
thermosetting resin containing at a surface portion the inorganic powder at a
content of 60 to 95 percent by weight by rotational casting, fitting a metal roll core
in the outer layer hollow cylinder and joining together the roll core and the outer
layer hollow cylinder.

9. The method of manufacturing a resin roll for calendering a magnetic
recording medium according to claim 8, wherein said step of fitting a metal roll
core in the outer layer hollow cylinder and joining together the roll core and the
outer layer hollow cylinder comprises the step of injecting an adhesive to an
annular clearance between the metal roll core and the outer layer hollow cylinder,
and curing the adhesive to bond the roll core and the outer layer hollow cylinder
with the adhesive layer interposed
10. The method of manufacturing a resin roll for calendering a magnetic
recording medium according to claim 8, wherein before performing said step of
fitting a metal roll core in the outer layer hollow cylinder and joining together the
roll core and the outer layer hollow cylinder, a fiber-reinforced lower winding
layer formed of a fiber material impregnated with a thermosetting resin is formed
on an outer peripheral surface of the metal core.
11. A resin roll for calendering a magnetic recording medium substantially as
herein described with reference to the accompanying drawings.
12. A method of manufacturing a resin roll for calendering a magnetic
recording medium substantially as herein described with reference to the
accompanying drawings.


Documents:

1587-mas-1995 abstract.pdf

1587-mas-1995 claims.pdf

1587-mas-1995 correspondence-others.pdf

1587-mas-1995 correspondence-po.pdf

1587-mas-1995 description(complete).pdf

1587-mas-1995 drawings.pdf

1587-mas-1995 form-1.pdf

1587-mas-1995 form-26.pdf

1587-mas-1995 form-4.pdf

1587-mas-1995 others.pdf

1587-mas-1995 petition.pdf


Patent Number 192677
Indian Patent Application Number 1587/MAS/1995
PG Journal Number 02/2006
Publication Date 13-Jan-2006
Grant Date 26-Oct-2005
Date of Filing 04-Dec-1995
Name of Patentee YAMAUCHI CORPORATION,
Applicant Address 2-7 SHODAI-TAJIKA, HIRAKATA-SHI, OSAKA,
Inventors:
# Inventor's Name Inventor's Address
1 ATSUO WATANABE 2-7-301 , FUJISAKANISHI-MACHI, HIRAKATA-SHI, OSAKA,
2 KENJIRO NAKAYAMA 3-204-104, YUMIOKA, OTOKOYAMA, YAWATA-SHI, KYOTO,
3 TATSUYUKI ABE, 8-2, OTSUKA-CHO 5-CHOME, TAKATSUKI-SHI, OSAKA ,
PCT International Classification Number B21B31/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA