JPH03283117A - Information recording carrier - Google Patents

Abstract

PURPOSE:To reduce double refraction of a disk by curing a UV-curing resin composition containing a specified compd. to form a substrate of the information recording carrier. CONSTITUTION:The substrate of the information recording carrier is formed by curing a UV-curing resin composition containing a specified compd. expressed by formula I. In formula I, X is an acyryloyl group or methacryloyl group. As for the photopolymn. initiator, benzil, benzoin, benzophenon, 4- methoxybenzophenon, benzildimethylketale, etc., can be used. Thereby, double refraction of the substrate can be reduced and the obtd. information recording carrier is suitable for magneto-optical recording.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a disc-shaped or card-shaped information recording carrier for recording or reproducing information signals.

(Prior Art) In recent years, information recording media have progressed toward higher density and larger capacity. Optical disks and magneto-optical disks are typical media. A method for forming tracking grooves and address detection bits on these disks is injection molding of thermoplastic resin using a mold called a stubber with grooves and bits on the surface. or ultraviolet curing resin (2P resin) on a transparent resin substrate.
There are methods such as curing (2P method). Although the injection molding method is superior in terms of mass production of media, the 2P method is said to be superior in terms of faithfully transferring the grooves of the stub bar or the shape of the bit.

As an improved means of the 2P method, Japanese Patent Application Laid-Open No. 55-16033
A method of manufacturing a transparent plate and 2PW integrally, as disclosed in Japanese Patent No. 8, has also been proposed. That is, the method involves injecting the 2P resin into a mold having a space equivalent to the size of the disk, curing it by irradiating it with ultraviolet rays from at least one direction, and then taking it out.

At this time, a stand bar is provided on one side of the mold,
Bits are formed on one side of the molded substrate. It is said that substrates made using this method exhibit superior properties in weather resistance tests compared to the conventional 2P method.

Discs produced by this method are disclosed in Japanese Patent Application Laid-Open No. 62-2665.
No. 8, JP-A-62-226101, JP-A-6
It has also been proposed in Publication No. 3-23238, etc. It is stated that these substrates are effective in increasing the number of erasable/recordable times, improving optical anisotropy, and improving durability under high temperature and high humidity conditions, compared to conventional substrates.

(Problems to be Solved by the Invention) One of the factors that influences the C/N (carrier-to-noise ratio) of optical disks and magneto-optical disks is the birefringence of the substrate. A large birefringence, ie, optical anisotropy, causes noise and worsens the C/N of the disk. This particularly affects magneto-optical disks in which signals are reproduced by the Kerr rotation angle, and it is desired that the substrate be free of birefringence.

Although it is generally easier to obtain a monolithic 2P substrate with lower birefringence than with the injection method, it is still large with conventional materials, and improvements in materials are required in the case of magneto-optical disks.

Here, focusing on the components of 2P11[1, the 2P resin is composed of at least (1) a main agent (a sensitive unsaturated resin and a reactive diluent) and (2) a photopolymerization initiator. Among these, the main component (i) mainly determines the physical properties of the cured product, so it is necessary to improve it to reduce the birefringence.

(Means for Solving Problem 1) The present invention has been made to solve the above-mentioned problem, and includes a substrate made of a cured ultraviolet curable resin, and a material formed on the substrate and formed by applying laser light or a magnetic field. In an information recording carrier comprising a recording layer whose optical or magnetic state changes and a protective layer formed on this recording layer, the substrate has an ultraviolet curable compound containing a compound represented by the following general formula (I). The present invention provides an information recording carrier characterized by being made of a cured resin composition.

CHO-X CH20-X X-0-CH-C-CH-0-CH-C-CH20-X
・(I) 2 2 2 CHO-X CH20-X (However, X is an acryloyl group or a methacryloyl group) (Example) Example and Comparative Example 1.2 It has a space with a diameter of 130 shoes with a spacing of Ill. A mold was prepared. One side of the mold was coated with a nickel stamper, and the opposite side was coated with a silicone-based mold release agent, and a fired glass plate was provided. Resin compositions (Examples 1 to 2 and Comparative Examples 1 to 8) prepared in Table 1 at the mixing ratio shown in Table 1 were injected into this mold, and 120W/
Ultraviolet rays were irradiated from the glass plate side for 30 seconds using an α high-pressure mercury lamp. Subsequently, the cured substrate was taken out from the mold, and its birefringence was measured using a known method.

The characteristics of birefringence in each of the above examples and comparative examples are as follows.
Shown in the table. In addition, the main agent (
The structural formulas of the sensitive unsaturated resins (used as sensitive unsaturated resins and reactive diluents) are shown in Table 2.

Also, oarocur 117 was used as a photopolymerization initiator.
3 is the trade name of 2-hydroxy-2-methyl-1-phenylpropan-1-one (Merck Japan Co., Ltd.).

(The following is a margin.) Here, to describe the permissible range for a magneto-optical disk, it is desirable that the hardened substrate has a hardness of 3n1 or less.

Considering this *i, as can be understood from Table 1, in Example 1, DPHA was used as the main ingredient;
The birefringence of the substrate is very small. Therefore, the C/N of the magneto-optical disk can be improved.

Further, in Example 2, a small amount of THPTA was mixed in the main agent as a reactive diluent for DPHA, but the birefringence is similarly small in this case as well.

On the other hand, in Comparative Examples 1 to 8, a compound other than DPHA is used as the main ingredient, but in this case, the birefringence of the substrate is considerably larger than 30-. In other words, the C/N of the magneto-optical disk is getting worse.

From the above results, it can be easily understood that the optimal base agent is one that mainly contains DPHA in the base agent.

Note that DPHA is a dipentaerythritol type acrylate. Optical anisotropy depends on the basic skeleton of the monomer, and when a dipentaerythritol type is used, the anisotropy becomes extremely small. The terminal group may be either acryloyl or methacryloyl. Acryloyl has the advantage of faster curing speed, but methacryloyl also has features that acryloyl does not have, such as lower viscosity and less skin irritation, so it is desirable to use a mixture of both in an appropriate ratio.

Further, another photopolymerizable monomer, oligomer, etc. may be added to DPHA to adjust the viscosity of the composition, the surface hardness of the cured product, the bending strength, etc. At this time, it is important to keep the amount added so as not to impair the birefringence of the cured product.

The photopolymerization initiators include benzyl, benzoin, benzophenone, 4-methoxybenzophenone, benzyldimethyl ketal, benzoin ethyl ether, benzoin isopropyl ether, myrrhazketone, anthraquinone, 2-methylanthraquinone, acetophenone, αα-dichloro-4- phenoxy-acetophenone,
p-tertbutyltrichloroacetophenone, methyloxobenzoylbenzoate, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropane 1-one, and the like can be used. Furthermore, an amine compound may be added to promote curing.

Furthermore, in the embodiments, the explanation has been made using a disc-shaped information recording carrier such as an optical disc or a magneto-optical disc, but it goes without saying that the same applies to a card-shaped information recording carrier.

(Effects of the Invention) As described above, in the information recording carrier of the present invention, since the substrate contains the compound represented by the general formula (I>) as described above, the birefringence of the substrate can be extremely reduced, and the optical An information recording carrier suitable for magnetic recording can be obtained.

Further, the ultraviolet curable resin composition of the present invention has excellent heat resistance, so that a high-quality magneto-optical film can be formed and high-density recording can be performed.

Claims (1)

[Scope of Claims] A substrate made of a cured ultraviolet curable resin, a recording layer formed on the substrate and whose optical or magnetic state changes upon application of laser light or a magnetic field, and a recording layer formed on the recording layer. An information recording carrier comprising a protective layer comprising a protective layer, wherein the substrate is a cured ultraviolet curable resin composition containing a compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) {However, X is an acryloyl group or a methacryloyl group}