JPH04247342A - Methacrylic resin for optical information recording body - Google Patents

Abstract

PURPOSE:To provide a methacrylic resin useful as an information recording body. CONSTITUTION:This methacrylic resin for information recording body consists of 85 to 99.5wt.% methyl methacrylate unit and 15 to 0.5wt.% tricyclo[5.2.1.0<2.6>]decanyl acrylate unit. The methacrylic resin for information recording body which has excellent heat resistance and flowability while maintaining the excellent optical characteristics intrinsic to the methacrylic resin is obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a methacrylic resin useful for optical information recording media such as video discs.

0002

[Prior Art] Methacrylic resin has excellent moldability and transparency, and exhibits useful optical properties, so it is known that it can be used in various optical devices.Recently, its excellent properties have been used to make video discs, etc. Used as a substrate for optical information recording media.

Substrates for optical information recording media are required to have low optical distortion, excellent heat resistance, and moldability, and in recent years, there has been a strong desire to improve the productivity of video discs, that is, to shorten the molding cycle. desired.

A copolymer of methyl methacrylate and ethyl methacrylate (Japanese Unexamined Patent Publication No. 123208/1983) has been proposed as a methacrylic resin for optical information recording media.

[0005]

[Problems to be Solved by the Invention] However, when the fluidity of the above-mentioned copolymer is improved, the optical distortion decreases;
On the other hand, it has been difficult to improve productivity because of the disadvantages of decreased heat resistance and decreased mechanical strength.

Currently, optical information recording substrates, especially video disks and audio disks, are mainly manufactured by injection molding, but when considering the productivity, the heat resistance and fluidity of the resin make it difficult to The molding cycle has been determined. In order to improve productivity in injection molding, optical distortion is small, excellent transparency, and heat resistance is improved to reduce resin fluidity and cooling time during injection molding without sacrificing mechanical strength. It is necessary to let
Existing molding materials have a problem in that improving their heat resistance is accompanied by a decrease in fluidity and mechanical strength.

[0007]

[Means for Solving the Problems] In view of the current situation, the inventors of the present invention have conducted intensive studies to provide a material for optical information recording media that does not have the above-mentioned problems.
We have arrived at the present invention.

That is, the present invention provides 85 to 99.5% by weight of methyl methacrylate units and tricyclo[5.2.1.
02.6] A methacrylic resin for information recording media comprising 15 to 0.5% by weight of decanyl acrylate units.

The copolymerization ratio of the methacrylic resin of the present invention is as described above, and outside this range, the mechanical strength of the molded article
It is not possible to combine this with productivity during mass production. That is, if the content of methyl methacrylate units exceeds 99.5% by weight, the molecular weight must be lowered in order to maintain the fluidity of the resin, resulting in a decrease in mechanical strength. On the other hand, if the tricyclo[5.2.1.02.6]decanyl acrylate unit exceeds 15% by weight, the mechanical strength will be significantly inferior.

[0010] Furthermore, the heat deformation temperature of the methacrylic resin of the present invention is AS
The temperature is preferably 70°C or higher, more preferably 80°C or higher, as measured under a load of 18.56 kg based on TM-D648. If the heat distortion temperature is lower than 70°C, the heat resistance of the molded product will be poor, and in particular, heat distortion during molding and use will become large, which may be undesirable.

For producing the methacrylic resin of the present invention, conventional methods for producing methacrylic resins such as suspension polymerization, bulk polymerization, and solution polymerization can be used. Stabilizers, mold release agents, lubricants, plasticizers, dyes, etc. can also be added to the methacrylic resin of the present invention, if necessary.

The methacrylic resin of the present invention thus obtained can be molded into a substrate by either injection molding or compression molding.

[0013]

[Examples] The present invention will be specifically explained below with reference to Examples. Note that "%" and "parts" in the examples indicate "% by weight" and "parts by weight", respectively. In addition, the measurement of each physical property value is
It was done in the following way. ■Heat distortion temperature (HDT) Measured under a load of 18.56 kg according to ASTM-D648. ■Melt flow rate (MFR) Measured under a load of 3.8 kg according to ASTM-D1238. (2) Tensile strength and tensile elongation A dumbbell type test piece was injection molded using an injection molding machine (PS-60E, manufactured by Nissei Plastics Co., Ltd.), and measured according to ASTM-D638. ■Light transmittance injection molding machine (M-200 Dynamelta, manufactured by Meiki Seisakusho)
A φ300 mm disk (1.2 mmt) was injection molded at a cylinder temperature of 260°C, and the transmittance at a point 7 cm from the center of the obtained disk molded product was measured using Shimadzu Corporation;
It was measured in the region of 500 to 900 nm using UV-160A. ■Birefringence■ Birefringence at a point 7 cm from the center of the disc molded product obtained using a polarizing microscope (Nikon, OPTIPHOT-
POL, SENARMONT COMPENSATO
R: Usage wavelength 546nm, single pass)
It was measured by

Examples 1 to 3 Methyl methacrylate and tricyclo[
5.2.1.02.6] 0.35 parts of n-octyl mercaptan to 100 parts of the monomer mixture of decanyl acrylate
0.44 part of lauroyl peroxide as a polymerization catalyst and 0.1 part of stearyl alcohol as a mold release agent.
1 part, 0.01 part of a copolymer of methyl methacrylate and potassium 3-methacryloyloxypropanesulfonate as a suspension polymerization dispersant, 0.15 part of sodium sulfate, and 145 parts of water as a dispersion medium. The mixture was mixed into a glass flask polymerization apparatus, polymerized at 80°C, and after the internal temperature reached a peak, it was held at 95°C for 30 minutes, cooled, filtered, washed with water, and dried to obtain a bead-shaped copolymer.

The obtained copolymer was kneaded and pelletized at 240° C. using a 40 mm extruder (manufactured by Tanabe Plastic Machinery Co., Ltd.). When the obtained pellets were used for various evaluations, the results shown in Table 1 were obtained.

[0016] In all Examples, the light transmittance was 91% or more in the wavelength range of 500 to 900 nm, and the birefringence was 20 nm or less, which was good.

Comparative Examples 1 to 4 Except for using 100 parts by weight of a monomer mixture consisting of methyl methacrylate and ethyl acrylate or tricyclo[5.2.1.02.6]decanyl acrylate in the proportions shown in Table 1. An experiment was conducted in exactly the same manner as in Example 1. In Comparative Example 4, the amount of n-octyl mercaptan used was 0.62 parts. The results are shown in Table 1. In addition, the copolymer obtained by copolymerizing 20 parts of tricyclo[5.2.1.02.6]decanyl acrylate and 80 parts of methyl methacrylate (Comparative Example 3) has low mechanical strength, so it is not practical. Furthermore, the polymer obtained by polymerizing 100 parts of methyl methacrylate (Comparative Example 4) had an MRF of 22
．． The fluidity was 5 g/10 minutes, which was almost the same as that of Example 2, but the tensile strength was less than half, and it lacked practicality.

From the results of Examples 1 to 4 and Comparative Examples 1 to 2, the relationship between MRF and HDT is as shown in FIG.
When trying to obtain a copolymer with an RF of 20 g/10 min,
Methyl methacrylate and tricyclo [5.2.1.02
．． 6] The copolymer of decanyl acrylate has more H than the copolymer of methyl methacrylate and ethyl acrylate.
It can be seen that an improvement of about 7°C is observed in DT.

In addition, when trying to obtain a resin with HDT of 86°C, methyl methacrylate and tricyclo[5.2.
1.02.6] The copolymer of decanyl acrylate was found to have an improvement of about 20 g/10 min in MRF than the copolymer of methyl methacrylate and ethyl acrylate, and the copolymer of methyl methacrylate and tricyclo[5.2.1. 02.6
] It can be said that the copolymer of decanyl acrylate has better moldability than the copolymer of methyl methacrylate and ethyl acrylate in terms of productivity.

[0020]

[Table 1] MMA: Methyl methacrylate TA: Tricyclo[5.2.1.02.6]decanyl acrylate EA: Ethyl acrylate

[0021]

[Effects of the Invention] The methacrylic resin for optical information recording media of the present invention is a molding material with excellent heat resistance, good fluidity, and productivity while retaining the excellent optical properties inherent to methacrylic resin. Because it can be suitably used as
It has excellent industrial effects.

[Brief explanation of the drawing]

FIG. 1 shows the H
It shows the relationship between DT and MRF.

Claims (1)

[Claims] [Claim 1] Methyl methacrylate units 85-99
．． 5% by weight and tricyclo[5.2.1.02.6]
A methacrylic resin for information recording media comprising 15 to 0.5% by weight of decanyl acrylate units.