JPS6390520A - Disk base using methacrylic resin composition as base - Google Patents

Abstract

PURPOSE:To obtain a disk base having excellent transparency, heat-resistance, mechanical strength, etc., by molding a methacrylate resin composition produced by polymerizing methyl methacrylate, a substituted phenylmaleimide monomer and a copolymerizable vinyl monomer at specific ratios. CONSTITUTION:The objective disk base is produced by molding a methacrylate resin produced by polymerizing (A) 55-98wt%, preferably 65-90wt% methyl methacrylate, (B) 2-45wt%, preferably 10-30wt% substituted phenylmaleimide monomer of formula (R1 and R2 are 1-3C alkyl) (e.g. N-2,6- dimethylphenylmaleimide) and (C) 0-40wt%, preferably 0-20wt% other vinyl monomer copolymerizable with the above monomers (e.g. acrylic acid). The methacrylate resin composition can be used also as an optical lens, automobile part, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a disc disk based on an extremely practical methacrylic resin having excellent transparency, heat resistance and moldability.

(Prior art) Generally, polymethyl methacrylate resin or methacrylic resin containing methyl methacrylate as a main component has transparency,
Due to its excellent properties such as surface gloss, mechanical strength, and moldability, the demand for it as a material for optical elements such as optical lenses and optical discs has been increasing in recent years. However, due to its poor heat resistance, as represented by its heat distortion temperature, its use is limited in applications that require shape stability at high temperatures, and research is underway to improve the heat resistance of methacrylic wood. It is widely practiced. For example, there is an optical disk substrate (Japanese Unexamined Patent Publication No. 61-95011) made of a copolymer obtained by copolymerizing a methyl methacrylate resin with a maleimide monomer to improve heat resistance.

(Problem to be solved by the invention) Does the copolymer obtained by this patent retain the excellent properties of methacrylic resins and has improved heat resistance? Since it is transparent with a yellowish tint, it is particularly suitable for applications that require transparency, such as optical disk substrates in optical disk memory systems such as optical video disks, digital audio disks, and image file disks. Instead, a colorless and transparent disc with no coloring was desired.

(Means for Solving the Problems) In view of the above problems, the inventors of the present invention have conducted intensive research to obtain a colorless and transparent disc with excellent mechanical properties and heat resistance. The present inventors have discovered that a disk obtained from a copolymer of methacrylate and a specific substituted phenylmaleimide has excellent heat resistance, is colorless and transparent, and has a low birefringence, and has completed the present invention.

That is, the present invention provides methyl methacrylate 55 (in the formula:
R1 and Rz each represent an alkyl group having 1 to 3 carbon atoms. ) Based on a methacrylic resin composition formed by polymerizing 2 to 45% by weight of a substituted phenylmaleimide monomer shown in It is a disc record.

The copolymer itself obtained by copolymerizing methyl methacrylate and maleimide monomer used in the present invention
It is known from Japanese Patent No. 9753.

Specifically, the substituted phenylmaleimide monomer represented by the general formula (I) of the present invention may include [engineering, for example, N-2,6-
Examples include dimethylphenylmaleimide, N-2,6-dinitylphenylmaleimide, N-2-ethyl-6-methylphenylmaleimide, and N-2,6-dipropylphenylmaleimide.

Specific examples of copolymerizable vinyl monomers include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, ethyl methacrylate, styrene,
Examples include α-methylstyrene, P-methylstyrene and acrylonitrile.

The copolymer used in the present invention is methyl methacrylate 5
It is necessary to contain 5 to 98% by weight, preferably 65 to 90% by weight. 55% by weight of methyl methacrylate
If it is less than this, transparency, birefringence and mechanical strength will deteriorate, which is not preferable. The substituted phenylmaleimide monomer represented by the general formula (υ) is preferably 2 to 45% by weight, preferably
It is necessary to contain an amount of 03i. If the substituted phenylmaleimide monomer is less than 2 quantum molecules, heat resistance decreases,
45:! If the content exceeds Et%, mechanical strength and high-temperature formability will decrease, causing a practical problem.

Further, other vinyl monomers copolymerizable with these monomers are contained in an amount of 0 to 40% by weight, preferably 0 to 20% by weight. When you cross it,
Problems with transparency and coloration occur, which is undesirable. The methacrylic resin composition of the present invention can also contain light stabilizers such as ultraviolet absorbers, heat stabilizers such as antioxidants, and the like.

The methacrylic resin composition of the present invention can be polymerized according to a commonly known method.

For example, various methods such as suspension polymerization, bulk polymerization, emulsion polymerization, and solution polymerization of the polymerization components can be used in the presence of a radical polymerization initiator at a temperature of 50 to 95°C. At this time, in addition to the initiator, a chain transfer agent, a usual suspending agent, an auxiliary agent, etc. can also be used. Furthermore, the methacrylic resin composition thus obtained can be molded into a disk having a shape and size depending on the purpose by injection molding, compression molding, or the like. Generally, the methacrylic resin composition of the present invention can also be used as optical lenses, automobile parts, etc.

(Effects) By selecting 2,6-dialkyl-substituted phenylmaleimide as a monomer to be copolymerized with methyl methacrylate, the present invention maintains the mechanical strength and moldability of conventional methacrylic resins, and has excellent heat resistance. This not only improves the quality of the disc, but also makes it possible to obtain a colorless and transparent disc.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 90 parts of methyl methacrylate, 10 parts of N-2,6-dinitylphenylmaleimide, and 0.5 part of azobisisobutyronitrile were mixed and heated in a container. Fill a cell with two glass plates (distance 0.32 m) with the produced syrup,
A resin composition was obtained by keeping at 75°C for 6 hours and then at 95°C for 2 hours.

Examples 2 to 6, Comparative Examples 1 to 4 Resin compositions having the type of maleimide and the proportion of each monomer of Example 1 shown in Table 1 were manufactured.

Table -1 Comparison 2 90 ``E;kereimido -0(
Physical properties of molded articles) The methacrylic resin compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were injection molded and their physical properties were measured. The heat deformation resistance ()[)T) is in accordance with ASTM-D648, the light transmittance is in accordance with JIS-6714, and the birefringence is in accordance with the thickness obtained by injection molding (cylinder temperature 260'Q mold temperature 60°C). Measurements were made using a precision strain meter using a 1.2B plate.

The results are shown in Table-2.

Table-2 Cup HDT (°C) Light transmittance (typ. Birefringence (
n,) Colorability Example 1 115 90
15 Colorless transparent view 6 125 δδ 1δ Comparison 1 95 92 8

Claims (1)

[Claims] Methyl methacrylate 55-98% by weight, represented by the general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R_1 and R_2 each represent an alkyl group having 1 to 3 carbon atoms.) A disc disk based on a methacrylic resin composition formed by polymerizing 2-45% by weight of a substituted phenylmaleimide monomer and 0-40% by weight of another vinyl monomer copolymerizable with these monomers. .