JPH061560B2 - Optical record carrier - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical record carrier, and more particularly, to an optical recording medium substrate capable of recording and reproducing by a light beam.
P (Photopolymerization)
The present invention relates to a 2P resin material used when manufacturing by a method called a method.

[Prior Art] Conventionally, glass, acrylic resin, polycarbonate resin, or the like has been used as a substrate material of an optical recording medium. In order to perform high-density recording on an optical recording medium, it is necessary to form an optical guide groove on the substrate,
Conventionally, two methods are known as such methods.
One of the methods is a method of transferring the guide groove at the same time as the molding of the substrate by injection molding using a mold in which irregularities corresponding to the shape of the guide groove are engraved.

Another method is to first apply an ultraviolet curable resin or the like on a mold in which irregularities corresponding to the shape of the guide groove are engraved, and then place the substrate on this resin, and then UV or the like. Is applied to cure the resin and fix the resin to the substrate to form a guide groove made of a curable resin.
It is a method called the law.

Although the former method is excellent in mass productivity, it has a drawback in that the transferability of the guide groove shape is poor, and there is a problem in that only plastic such as acrylic resin or polycarbonate resin can be used as the substrate material. That is, in a recording medium using a plastic substrate, since the plastic substrate has air permeability, the recording layer is corroded by moisture, oxygen, etc., and the recording characteristics thereof are gradually deteriorated. Therefore, if this method in which only plastic can be used as the substrate material is adopted, there arises a problem that it is impossible to manufacture a recording medium capable of maintaining recording characteristics for a long period of time.

On the other hand, the latter method not only has good transferability of the guide groove shape, but glass can be used as the substrate material other than plastic. Therefore, by using the glass substrate provided with the guide groove by this method, it is possible to manufacture a recording medium that can maintain high reliability for a long period of time.

[Problems to be Solved by the Invention] The ultraviolet curable resin used in the 2P method is required to have conflicting performances such as easy peeling from the mold and good adhesion to the substrate. However, since it is generally difficult to satisfy both performances at the same time, a method of performing mold surface treatment so that the resin can be released even if it has good adhesion, and good adhesion between the substrate and resin In order to achieve this, a method of providing another layer for improving the adhesiveness between the 2P layers has been considered.

However, the former method has a drawback that the surface treatment is used to diminish defects on the mold surface or contaminate the substrate surface during molding. Further, there is a problem that the frequency of replacement of the mold is increased because the treatment effect has a long life.

On the other hand, in the latter method, noise may increase due to uneven coating of the layer provided to improve the adhesion between the resin and the substrate, and the coating process is performed for each substrate to provide the layer. Therefore, there is a problem that mass productivity is lowered.

Further, in consideration of the film forming property of the recording layer on the 2P layer, when the inorganic film or the metal film is formed by the vacuum process, the temperature of the substrate may increase during the film formation or the stress of the film may be large.
Therefore, the 2P layer is required to have heat resistance and hardness.
However, in general, a curable resin has a large residual stress at the time of curing and the adhesive force tends to decrease. Therefore, if the polar group is wiped in order to improve the adhesion, the water absorption is increased and a problem occurs in durability.

An object of the present invention is to solve these conventional problems, and by using a 2P resin having excellent adhesion to a substrate and good releasability, high productivity and high reliability can be maintained for a long time. To provide an optical record carrier.

[Means for Solving Problems] and [Operation] That is, the present invention comprises a resin layer between the substrate and the recording layer, the resin layer being integrated with the substrate and facing the substrate. In an optical record carrier having a guide groove on the non-coated surface, the resin layer comprises (A) a mixture of pentaerythritol acrylic acid ester and its derivative (B) bifunctional acrylic acid ester (C) flexibility Giving agent (D) A cured product of an ultraviolet curable resin containing a photopolymerization initiator and containing, as the flexibility-imparting agent, di (2-ethylhexyl) phthalate or an acrylate ester containing a benzene ring. An optical record carrier characterized by:

Hereinafter, the present invention will be described in detail.

In the present invention, a mixture of pentaerythritol acrylic acid ester and its derivative is used as a base resin of an ultraviolet curable resin used in the 2P layer of the optical record carrier according to the present invention.

Specific examples of the pentaerythritol acrylic acid ester and its derivative include pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol monohydroxypentaacrylate.

Among them, a mixture containing dipentaerythritol hexaacrylate and dipentaerythritol monohydroxypentaacrylate in a total amount of 50% by weight or more is preferable.

Further, the content of the mixture of acrylic acid ester of pentaerythritol and its derivative in the ultraviolet curable resin is 10 to 80% by weight, preferably 20 to 40% by weight,
If it is less than 10% by weight, the adhesiveness between the resin and the substrate will be reduced, and if it exceeds 80% by weight, on the contrary, the adhesiveness will be too good and release will be difficult.

In the present invention, the mixture of the acrylic acid ester of pentaerythritol and its derivative has a high viscosity and cannot be used alone for work, and in order to impart various other properties, a bifunctional acrylic acid having a relatively low viscosity is used. The ester is used as the reactive diluent. In selecting the reactive diluent, it is necessary to consider viscosity, reaction rate, volume shrinkage upon curing, flexibility, adhesion to a substrate, releasability from a mold, safety and the like. From the viewpoint of reaction rate and volume shrinkage, it is preferable to use a bifunctional reactive diluent. The reaction rate affects the productivity, and the volume shrinkage causes warp in the finished disk and deteriorates the flatness.

A bifunctional acrylic acid ester is used as the bifunctional reactive diluent, and specific examples thereof include butanediol diacrylate, hexanediol diacrylate, hydroxypivalic acid ester neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene. Examples thereof include glycol diacrylate and neopentyl glycol diacrylate.

Further, the content of the bifunctional acrylic ester in the ultraviolet curable resin is preferably 10 to 80% by weight, preferably 20 to 70% by weight. If it is less than 10% by weight, the resin becomes soft and the heat resistance decreases. However, the above effect cannot be obtained because the amount of addition is small, and when it exceeds 80% by weight, the adhesion between the resin and the substrate decreases.

In the present invention, a resin containing a mixture of the above-mentioned acrylic acid ester of pentaerythritol and its derivative and a bifunctional acrylic acid ester alone becomes a hard and heat-resistant resin, but the residual stress at the time of curing is large and the resin is hard to heat. Since adhesion cannot be obtained, a compound that imparts flexibility as a flexibility-imparting agent is added to reduce stress.

Even if it is given flexibility, it may be wrinkled due to heat applied during film formation if it is simply softened, or wrinkles or cracks may occur when a durability test is performed if a film with strong stress is applied. Can not. Therefore, it is necessary to reduce the stress to the point where the adhesion to the glass substrate is sufficient, and to use a resin having sufficient hardness and heat resistance.

As the flexibility-imparting agent, a plasticizer, an acrylic acid ester containing a benzene ring and the like are suitable. As a plasticizer, di (2
-Ethylhexyl) phthalate is most suitable. Examples of acrylic acid ester containing a benzene ring include phenylcarbitol acrylate, nonylphenoxyethyl acrylate, diacryloyl- (bisethylene glycol) -phthalate and the like.

Further, the content of the flexibility-imparting agent in the ultraviolet curable resin is preferably 2 to 40% by weight, preferably 5 to 30% by weight, and if less than 2% by weight, the residual reaction power becomes large and the adhesion between the resin and the substrate If the amount exceeds 40% by weight, the resin becomes soft and the heat resistance decreases.

In the present invention, a photopolymerization initiator is used in order to efficiently initiate the reaction by UV irradiation.

As the photopolymerization initiator, in consideration of absorption wavelength, absorption coefficient, reaction rate, oxygen inhibition, etc., benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, benzoin isopropyl ether or 2-vidroxy-2-methyl-propiophenone is used. One kind or two or more kinds selected is preferable.

Further, the content of the photopolymerization initiator in the ultraviolet curable resin is 0.5 to 10% by weight, preferably 1 to 5% by weight, and if less than 0.5% by weight, the photopolymerization reaction slows and the curing does not take place. The curing rate does not change even if more than this is added.

In addition to the above-mentioned components, the ultraviolet-curable resin in the present invention may contain a colorant, a filler, an antioxidant, a rust preventive, etc., if necessary.

As the substrate in the present invention, any material can be used as long as it is made of a material generally used in the past, for example, a synthetic resin material such as glass, acrylic resin, or polycarbonate resin.

The optical record carrier according to the present invention comprises a mold having irregularities corresponding to the shape of a guide groove, a mixture of the above-mentioned pentaerythritol acrylate ester and its derivative, a bifunctional acrylate ester, a softening agent, After coating a UV-curable resin produced by mixing a predetermined amount of a photopolymerization initiator, a substrate is placed on the resin, then the resin is cured by irradiation with ultraviolet rays or the like, and the resin is fixed to the substrate. It can be easily obtained by integrating and peeling from the mold.

In the present invention, the ultraviolet-curable resin containing the above components is integrated with the substrate to form an optical record carrier. Therefore, the components of the resin act on each other in a complementary manner. It is presumed that it has excellent adhesiveness, good releasability, and imparts excellent durability to the optical record carrier.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 KAYARADDPHA manufactured by Nippon Kayaku Co., Ltd. as a base resin
16% by weight (mixture of dipentaerythritol hexaacrylate and dipentaerythritol monohydroxypentaacrylate) and PETA manufactured by Osaka Organic Chemical Industry Co., Ltd.
(Mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate) 16% by weight, 2
KAYA manufactured by Nippon Kayaku Co., Ltd. as a functional acrylic ester
55% by weight of RAD HDDA (hexanediol diacrylate), 8% by weight of di- (2-ethylhexyl) phthalate as a compound that imparts flexibility to a cured product, and a photopolymerization initiator manufactured by Merck & Co., Inc., Durcure 1173 (2-hydroxy-2). −
2P molding was performed on a glass substrate using a resin mixed with 5% by weight of methyl-propiophenone.

This was left for 24 hours in a desiccator having a relative humidity of 10% or less. After leaving it for a long time, a JIS G 5400 goggle test was carried out, and the result was 100/100, showing very good adhesion.

Next, the 2P substrate made by the method described above, by forming a protective layer of SiO ₂ having a thickness of 1200Å by a vacuum evaporation method, further, amorphous Gd · Tb · Fe · Co having a thickness of 1000Å by sputtering Was formed into a magnetic recording layer. Then, a protective layer of SiO ₂ having a layer thickness of 2000 Å was formed in the same manner as the protective film described above.

Next, a glass substrate similar to the above-mentioned substrate was bonded via an adhesive layer made of a hot-melt adhesive to prepare an optical recording medium.

This optical recording medium is stored at 45 ° C and 95% relative humidity for 10
Appearance change (wrinkles, cracks, blisters) after leaving for 00hr
The results are shown in Table 1.

Example 2 Instead of di (2-ethylhexyl) phthalate, M-5700 (2-hydroxy-3-phenoxypropyl acrylate manufactured by Toagosei Kagaku Kogyo Co., Ltd., An optical recording medium was produced in the same manner as in Example 1 except that a resin containing 8% by weight of (4) was used, and changes in appearance were observed.
The results were the same as in Example 1.

A goggles test was conducted in the same manner as in Example 1, and the result was 100/100, which was very good adhesion as in Example 1.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1 except that the resin of the combination in which di (2-ethylhexyl) phthalate, which is a compound that gives flexibility to the cured product, was removed was used to change the appearance. saw. The results were the same as in Example 1.

A goggles test was conducted in the same manner as in Example 1, and the result was 0/100, and the adhesion was poor.

Comparative Example 2 Same as Example 3 except that the base resin was removed and the amount of EA-800 (epoxy acrylate) was 30% by weight and the amount of HDDA (hexanediol diacrylate) was 65% by weight. An optical recording medium was prepared and changes in appearance were observed. The results are shown in Table 1.

A goggles test was conducted in the same manner as in Example 1, and the result was 0/100, and the adhesion was poor.

From the results in Table 1 above, it is clear from comparison between Examples 1 and 2 and Comparative Examples 1 and 2 that the resin of the present invention has excellent adhesiveness.

In addition, when the thermal characteristics of each resin were examined, those with a Tg (secondary transition point) of 100 ° C or higher and a sufficiently high rigidity were wrinkled.
No cracks were generated during film formation and during durability (see Table 1). In Comparative Example 2 having a low Tg, wrinkles and cracks are immediately generated by the heat at the time of film formation, so the film is formed while cooling the substrate so that wrinkles and cracks do not occur.
However, after endurance test (45 ℃, 95% RH)
A crack has occurred.

As is apparent from these, it is recognized that the resin of the present invention has excellent adhesion and is suitable for producing an optical record carrier capable of maintaining high reliability for a long period of time.

[Effect of the invention] As is clear from the above description, since the optical record carrier according to the present invention uses the ultraviolet curable resin having a specific composition, the adhesiveness between the resin and the substrate is excellent, It has high releasability, high productivity, and can maintain high reliability for a long time, which is extremely useful.

Claims (4)

[Claims] 1. An optical recording comprising a resin layer between a substrate and a recording layer, the resin layer being integrated with the substrate, and having a guide groove on the surface not facing the substrate. In the carrier, the resin layer contains (A) a mixture of acrylic acid ester of pentaerythritol and its derivative, (B) a bifunctional acrylic acid ester, (C) a softening agent (D) a photopolymerization initiator, and An optical record carrier, which is a cured product of an ultraviolet curable resin containing di (2-ethylhexyl) phthalate or an acrylate ester containing a benzene ring as a flexibility-imparting agent. 2. A mixture of acrylic acid esters of pentaerythritol and its derivatives containing dipentaerythritol hexaacrylate and dipentaerythritol monohydroxypentaacrylate in an amount of 50% by weight or more of the component (A). An optical record carrier according to the item. 3. The optical record carrier according to claim 1, wherein the bifunctional acrylic acid ester is hexanediol diacrylate. 4. A patent in which the photopolymerization initiator is one or more substances selected from benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, benzoin isopropyl ether or 2-hydroxy-2-methyl-propiophenone. An optical record carrier according to claim 1.