JPS63210111A - Optical resin material - Google Patents

Abstract

PURPOSE:To provide the title material low in birefringence and superior in transparency, heat resistance, and water absorption properties, which is suitable for a substrate of optical discs, and comprises as a main component a polymer produced from a compound having 2 or more vinylphenyl groups in the molecule and other vinyl monomer copolymerizable with the compound. CONSTITUTION:A composition obtained by mixing 5-50wt.% compound (A), as crosslinking agent, having 2 or more vinylphenyl groups in the molecule of formula I (wherein R is a substituent such as an aliphatic hydrocarbon group, halogenated alkyl, an aliphatic ring, an aromatic ring, a heterocyclic ring, or phenyl-substituted alkyl; and n is 2 or more, and a bond, for example, of O, S or formulae II-V may be included in the compound), for example, bisphenol A vinylbenzyl ether, 1,2-bis(p-vinylphenyl)ethan, or 1,6-bis(p-vinylbenzyl)hexyl ether, with 95-50wt.% other vinyl monomer (B) copolymerizable with component (A), for example, styrene (derivatives), is mixed with a radical initiator in a predetermined amount, and the mixture is poured into a mold for polymerization followed by degassing, and polymerized at a predetermined temperature for a predetermined time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention particularly relates to optical resin materials having low birefringence and excellent transparency, heat resistance, and hygroscopicity.

(Prior Art) In recent years, optical disks have attracted attention as information recording media that have a particularly large storage capacity and are randomly accessible, and their use has been remarkable. Such optical discs are classified into read-only types, write-once-only types, and rewritable types depending on their type, and the read-only types have been applied to, for example, video discs, compact discs, etc., and have formed a large-scale market.

On the other hand, for write-only types and rewritable types, for example, text files.

Some of these have been applied to computer files, video files, etc., and have reached the market, but further development is underway. A substrate for such an optical device has low birefringence and is transparent.

Functions such as heat resistance and hygroscopicity are required, and in particular, write-only types and rewritable types are required to be superior to the above-mentioned functions compared to read-only types. Conventionally, optical resin materials such as substrates for optical disks are made of polymethyl methacrylate, polycarbonate, etc., and are injection molded and used as substrates for video disks, compact disks, and the like. However, such conventional optical resin materials such as disk substrates have problems due to the lack of the above-mentioned functions when applied to write-once type or rewritable type.

In order to solve the above-mentioned problems, recently, for example, a method for manufacturing an optical disk substrate by cast polymerization of epoxy resin (Japanese Patent Laid-Open No. 59
-22248), radical polymerization of a methacrylic partial mixture with a specified viscosity, consisting of methyl methacrylate, a specific methacrylic acid alkyl ester, a crosslinkable monomer, and a monoethylenically unsaturated monomer copolymerizable with these. A method for producing an optical disk substrate in which the substrate is cured under pressure and heat in a mold in the presence of an initiator (JP-A-61-8!1)
No. 213), a monomer mixture or a monomer comprising a specific amount of an aromatic vinyl monomer and another vinyl monomer copolymerizable with the aromatic vinyl monomer. Optical disk substrate formed by mold polymerization (Japanese Patent Application Laid-Open No. 61-24621
No. 0) etc. have been proposed.

(Problem to be Solved by the Invention) However, the optical resin materials proposed above do not satisfy all the required functions, and are especially suitable for write-once type and rewritable type optical discs. When used as a substrate, it has lower birefringence, transparency, and heat resistance.

There is a need for an optical disk substrate that satisfies all the functions of hygroscopicity and hygroscopicity. An object of the present invention is to provide a plastic optical resin material suitable for such optical disk substrates.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the present inventors have developed a composition comprising a crosslinking agent of a specified compound and a vinyl monomer copolymerizable with the crosslinking agent. The present inventors have discovered that a resin having desired physical properties can be obtained by cast polymerization, and have proposed the present invention. That is, the present invention provides a composition comprising 5 to 50% by weight of a compound having at least 42 or more vinyl phenyl groups in the molecule and 50 to 95% by weight of another vinyl monomer copolymerizable with the compound. It is an optical resin material whose main component is optical resin material.

In the present invention, by blending the crosslinking agent of the above-specified compound, the resin obtained by cast polymerization is particularly improved in birefringence, and also satisfies heat resistance and hygroscopicity. It is useful as a disk substrate for molds and rewritable molds.

The crosslinking agent used in the present invention contains at least two
Compounds having at least 3 vinylphenyl groups are represented by the general formula RicH-'H2), where R is, for example, an aliphatic hydrocarbon, a logogenated alkyl, an alicyclic ring, an aromatic ring,
A compound having two vinyl phenyl groups represented by a heterocyclic ring or a substituent such as phenyl-substituted alkyl, where n is 2 or more, etc. R' in the formula C is I(, CH,, C2H
5.

(F, ct, Br, @, etc.), and compounds having six vinylphenyl groups such as, for example. In addition, hydrogen of the vinyl phenyl group or the phenyl group in the above formula is an alkyl group such as a methyl group, respectively.

... May be substituted with rogen.

Furthermore, the vinyl monomer copolymerizable with the above-mentioned crosslinking agent used in the present invention is not particularly limited as long as it is a conventionally known monomer that is subjected to cast polymerization to obtain a disk substrate or the like. Examples include styrene and p-methylstyrene.

α-methylstyrene, chlorostyrene, fluorostyrene, bromostyrene, butylstyrene, trans-
Styrene and its derivatives such as stilbene and divinylbenzene; methyl methacrylate, butyl methacrylate,
Methacrylic acid esters and acrylic esters such as ethyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, bornyl methacrylate, methyl acrylate, and ethyl acrylate; maleic anhydride, maleic acid, and maleic acid such as phenylmaleic anhydride; Derivatives: Maleimide derivatives such as N-methylmaleimide and N-phenylmaleimide can be mentioned, but styrene and its derivatives are particularly used in order to obtain a disk substrate that has good copolymerizability with a crosslinking agent and has low hygroscopicity. It is preferable. Incidentally, in order to improve other physical properties of the target disk substrate, a monomer copolymerizable with the above-mentioned vinyl' monomer can also be used in combination.

Furthermore, it is possible to mix, for example, an antioxidant, a light stabilizer, a mold release agent, an antistatic agent, etc. into the above-mentioned monomer mixture as long as it does not impede the achievement of the objects of the present invention. In order to fully exhibit the effects of the present invention, the blending ratio of a compound having at least two or more vinyl phenyl groups in the molecule and another vinyl monomer that can be copolymerized with the compound should be within one molecule. 5 to 50% by weight, preferably 10 to 30% by weight of a compound having at least two or more vinyl phenyl groups, and 50 to 95% by weight, preferably 50 to 95% by weight of another vinyl monomer copolymerizable with the compound. 90~
It is preferable to select it so that it is 70% by weight. That is, if the amount of the compound having at least two vinyl phenyl groups in the molecule is less than 5% by weight, the heat resistance of the resulting substrate will decrease and the birefringence will increase. On the other hand, if the compound having at least two or more vinyl phenyl groups in the molecule is used in an amount exceeding 50% by weight, the mechanical strength of the resulting substrate will decrease, which is preferable for the polymer of the present invention. It is generally obtained by a cast polymerization method. The cast polymerization method is not particularly limited (it can be used, for example, for a composition containing a compound having at least two or more vinyl phenyl groups in the molecule described above and another vinyl monomer copolymerizable with the compound). For example, a predetermined amount of peroxide-based radical initiators such as bis-(4-1-butylcyclohexyl) peroxydicarbonate and benzoyl peroxide, and azo-based radical initiators are mixed, and the mixture is injected into a polymerization mold and decomposed. This is a method in which polymerization is carried out at a predetermined temperature for a predetermined time after foaming.At this time, a metal original plate with guide grooves or pits is used as a mold for one polymerization, and the guide grooves and pits are transferred directly onto the substrate. Alternatively, after creating a cast-polymerized board with a predetermined thickness, a disc may be cut out from that board.

Alternatively, a predetermined amount of the monomer mixture may be injected into a glass mold having a predetermined gap and polymerized by irradiation with ultraviolet rays or radiation.

(Effects) The resin material of the present invention is obtained by cast-polymerizing a composition containing a specified crosslinking agent, so that the resulting resin substrate has a birefringence of 15
mm or less, especially 5 m or less, total light transmittance of 85% or more, especially 90% or more, glass transition temperature of 100°C or more, especially 12
It has excellent physical properties such as 0° C. or higher and a water absorption rate of 0.1% or less, especially 0.05% or less, so it is suitable for substrates for optical disks and the like.

(Example) In order to explain the present invention more specifically, Examples are given below, but the present invention is not limited to these Examples.The material of the disk substrate obtained in the Example is ,
Its physical properties were measured by the following test methods.

(1) Birefringence: A plate with a thickness of 1.3 m was made, and the birefringence at normal incidence and at 30° #4 was measured using a polarizing microscope.

(11) Total light transmittance: Make a plate with a thickness of 1.3 cm, and
Measured according to 8-7105.

(iii) Glass transition temperature: Measured with a differential scanning calorimeter.

(1v) Water absorption rate: Measured according to JIEI-6911.

Example 1 Bisphenol A Vinyl Benzyl Ether C, BAV
(abbreviated as E) and 80 parts by weight of styrene were mixed with 0.2 parts by weight of bis-C4-1-butylcyclohexyl) peroxydicarbonenite as a polymerization initiator, and
After molecular molding was carried out at 0° C. for 30 minutes, the mixture was degassed and poured into a mold composed of two glass plates and a Teflon tube to carry out cast polymerization. Polymerization was carried out at 50°C for 8 hours.
The polymer was heated at 80° C. for 2 hours and at 120° C. for 1 hour, and the polymer was released from the glass mold to obtain a colorless and transparent disk substrate with a thickness of 1.3 cm and a diameter of 150 cm. Table 1 shows the physical properties of the obtained disk substrate.

Examples 2 and 3 K instead of bisphenol A vinylbenzyl ether shown in Example 1, aH2=cH (column ccn2cH2$ca=cH21,2
-Bis(p-vinylphenyl)ethane C or less, BPVg
(hereinafter abbreviated as BPVH)
Cast polymerization was carried out in the same manner as in Example 1 to obtain a disk substrate. Table 1 shows the physical properties of the obtained disk substrate.

Examples 4 and 5 Cast polymerization was carried out in the same manner as in Example 1, except that the amount of BAVB used in Example 1 was changed as shown in Table 1, to obtain a disk substrate. Table 1 shows the physical properties of the obtained disk substrate.

Comparative Examples 1.2.3 and 4 In place of the bisphenol A vinylbenzyl ether shown in Example 1, divinylbenzene C (hereinafter abbreviated as DVB), ethylene glycol dimethacrylate C or less,
Cast polymerization was carried out in the same manner as in Example 1, except that bisphenol A dimethacrylate C (hereinafter abbreviated as BADMA) was used to obtain a disk substrate. Further, cast polymerization was performed using styrene alone in the same manner as in Example 1 to obtain a disk substrate. Table 1 shows the physical properties of the obtained disk substrate.

Example 6 Cast polymerization was carried out in the same manner as in Example 1, except that 60 parts by weight of styrene and 20 parts by weight of trans-stilbene were used instead of the styrene shown in Example 1, to obtain a disk substrate.

Table 1 shows the physical properties of the obtained disk substrate.

Comparative Example 5 Holistyrene (Estyrene H-15, manufactured by Nippon Steel Chemical)
Using a 1.5 oz injection molding machine, the length is 120+W and the width is 12
(2) Molding a plate with a thickness of 1.5 gourds and measuring the birefringence and glass transition temperature of its center.

The water absorption rate was measured. The results are shown in Table-1.

Claims (4)

[Claims] (1) A polymer composition consisting of 5 to 50% by weight of a compound having at least two or more vinyl phenyl groups in the molecule and 50 to 95% by weight of another vinyl monomer copolymerizable with the compound. Optical resin material as main component (2) A compound having at least two or more vinylphenyl groups in the molecule is converted into bisphenol A vinylbenzyl ether, 1,2-bis(p-vinylphenyl)ethane or 1,6-bis(p-vinylbenzyl) The optical resin material according to claim 1, which is xyether (3) The optical resin material according to claim 1, wherein the other vinyl monomer is styrene or a styrene derivative. (4) The optical resin material according to claim 1, which is a cast-polymerized polymer.