JP2003221418A - Methacrylic resin and optical material using the methacrylic resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a methacrylic resin having a low hygroscopicity, an excellent heat resistance and dimensional stability, and an optical material using the methacrylic resin. <P>SOLUTION: The methacrylic resin is obtained by copolymerizing a,monomer mixture containing 5-95 wt.% of (A) alkyl methacrylate, and 95-5 wt.% of (B) methacrylic acid alicyclic hydrocarbon ester having a C≥8 alicyclic hydrocarbon group in the alcoholic portion of the ester. The methacrylic acid alicyclic hydrocarbon ester (B) contains at least two kinds of compounds selected from bornyl methacrylate, isobornyl methacrylate, adamanthyl methacrylate, dimethyladamanthyl methacrylate, phenthyl methacrylate, 1-menthyl methacrylate, and 3,5-trimethylcyclohexyl methacrylate. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a methacrylic resin excellent in heat resistance and low hygroscopicity, and an optical material using the methacrylic resin.

[0002]

2. Description of the Related Art Polymethylmethacrylate resins are excellent in transparency and weather resistance, and have well-balanced properties such as mechanical properties, thermal properties and molding processability. It is used in the field. In recent years, taking advantage of features such as low birefringence of polymethylmethacrylate resin, applications of optical materials include information recording optical elements such as video discs, audio discs, computer information files, and LCD light guide plates. It is used as a material for.

However, while the conventional polymethylmethacrylate resin has the above-mentioned excellent properties, it has poor heat resistance because the permissible temperature limit for use is about 100 ° C., and the water absorption rate at 100% relative humidity is low. Since it is 2% or more, there are drawbacks such as lowering of the allowable limit temperature, dimensional change, warpage, etc., and cracking due to repeated cycles of moisture absorption and drying. Therefore, particularly for optical material applications, improvements in dimensional stability, heat resistance, and low hygroscopicity that do not cause warpage in molded products are demanded.

JP-A-58-53186 and JP-A-58-13652 disclose a copolymer of cyclohexyl methacrylate and methyl methacrylate for the purpose of improving low hygroscopicity. However, as a result of using a relatively large amount of cyclohexyl methacrylate as a component for suppressing hygroscopicity, the heat resistance of the obtained copolymer is lowered and the use temperature is limited.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a methacrylic resin having low hygroscopicity, heat resistance and dimensional stability, and an optical material using the methacrylic resin. Another object of the present invention is to provide a methacrylic resin having low birefringence and high mechanical strength in addition to the above properties, and an optical material using the methacrylic resin.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have identified a methacrylic acid alkyl ester (A) and a specific methacrylic acid alicyclic hydrocarbon ester (B), respectively. It was found that a methacrylic resin having low hygroscopicity and excellent heat resistance can be obtained by copolymerizing a monomer mixture containing a large amount thereof, and completed the present invention.

That is, according to the present invention, (A) a methacrylic acid alicyclic carbonic acid having 5 to 95% by weight of a methacrylic acid alkyl ester and (B) an ester alcohol portion having an alicyclic hydrocarbon group having 8 or more carbon atoms. Hydrogen ester 95-5% by weight
A methacrylic resin obtained by copolymerizing a monomer mixture containing, wherein the methacrylic acid alicyclic hydrocarbon ester (B) is bornyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, dimethyladamantyl methacrylate, A methacrylic resin containing at least two compounds selected from fentyl methacrylate, 1-menthyl methacrylate, and methacrylic acid (3,3,5-trimethylcyclohexyl). The methacrylic acid alkyl ester (A) may be methyl methacrylate.

The present invention also provides an optical material using the above methacrylic resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The methacrylic resin in the present invention contains a specific amount of a methacrylic acid alkyl ester (A) and a methacrylic acid alicyclic hydrocarbon ester (B) in which the alcohol portion of the ester has an alicyclic hydrocarbon group having 8 or more carbon atoms. It is obtained by copolymerizing a monomer mixture. "C8 or more" means that, when a hydrocarbon group such as an alkyl group is bonded to the alicyclic ring, the number of carbon atoms in the hydrocarbon group is 8 or more.

As the methacrylic acid alkyl ester (A), for example, methacrylic acid C _1-8 alkyl ester such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate and 2-ethylhexyl methacrylate. Etc. Among them, methyl methacrylate is preferably used because it is economically inexpensive.

As the methacrylic acid alicyclic hydrocarbon ester (B) in which the alcohol portion of the ester has an alicyclic hydrocarbon group having 8 or more carbon atoms, methacrylic acid or a chloride thereof can be used. Examples thereof include methacrylic acid esters obtained by esterification with the formula hydrocarbon monool. By using such a methacrylic acid alicyclic hydrocarbon ester as a monomer component, heat resistance and low hygroscopicity of the resulting copolymer can be simultaneously improved.

Examples of the alicyclic hydrocarbon monool having 8 or more carbon atoms include 1-adamantanol, 2-adamantanol, 2-methyl-1-adamantanol, and the like.
3,5-Dimethyl-1-adamantanol, 3-ethyladamantanol, 2-methyl-6-ethyl-1-adamantanol, 2,6,8-triethyl-1-adamantanol, 3,5-dimethyl-8 -Adamantanols such as ethyl-1-adamantanol; 1-mentanol, octahydro-4,7-mentanoinden-6-ol, octahydro-4,7-mentanoindene-1-
Ilmentanol, 8, p-mentanol-2,6,6
Menthanols such as -hydroxy-2,6,6-trimethyl-bicyclo [3.1.1] heptane; 3,
7,7-Trimethyl-4-hydroxy-bicyclo [4.
1.0] Heptane borneol, borneols such as isoborneol; 2-methylcamphor, fentyl alcohol, 2,2,5-trimethylcyclohexanol, 3,3,5-trimethylcyclohexanol, tricyclo [3.2. 1] Decylol and the like can be mentioned.

Among them, alicyclic hydrocarbon monools having 10 or more carbon atoms, such as adamantanols, mentanols, borneols, 2-methylcamphor, fentyl alcohol, tricyclo [3.2.1] decylol, etc. It is preferable in terms of heat resistance and low water absorption.

When methacrylic acid aromatic hydrocarbon ester is used instead of the methacrylic acid alicyclic hydrocarbon ester (B), the birefringence of the obtained resin becomes large, and the weather resistance is poor and it tends to be colored. Not suitable for optical materials. Further, even if the alcohol portion of the ester is an alicyclic hydrocarbon group, if the carbon number is 7 or less, low hygroscopicity and heat resistance are not improved, and the alcohol portion of the ester has 8 carbon atoms. Even if the above is the case, in the case of a linear or branched aliphatic hydrocarbon group, it does not contribute to the improvement of heat resistance, but rather, heat resistance and mechanical strength are impaired.

One of the features of the present invention is as a methacrylic acid alicyclic hydrocarbon ester (B), bornyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, dimethyladamantyl methacrylate, fentyl methacrylate, 1-methacrylic acid. The point is that at least two compounds selected from menthyl and methacrylic acid (3,3,5-trimethylcyclohexyl) are used. By using two or more of the above compounds, it is possible to suppress a decrease in heat resistance while significantly decreasing hygroscopicity, and it is possible to obtain a lower birefringence.

When two or more of these compounds are combined, compared to the case where only one of these compounds is used,
There is an advantage that the hygroscopicity of the obtained resin is significantly reduced.

The proportion of these compounds in the whole methacrylic acid alicyclic hydrocarbon ester (B) is, for example, 5
It is 0 to 100% by weight, preferably 80 to 100% by weight, and more preferably 90 to 100% by weight.

As a preferred combination of two or more of these compounds, a combination of either adamantyl methacrylate or dimethyladamantyl methacrylate (adamantyl methacrylates) and another compound can be mentioned, and a further preferred combination is given. , A combination of dimethyladamantyl methacrylate and isobornyl methacrylate. The combination ratio is adamantyl methacrylate: other compound =
It is from 1: 1 to 60, preferably from 1/5 to 50, more preferably from 1:10 to 40.

The methacrylic resin of the present invention contains 5 to 95% by weight of the above-mentioned methacrylic acid alkyl ester (A) and 95 to 95% of methacrylic acid alicyclic hydrocarbon ester (B).
It is obtained by copolymerizing a monomer mixture containing 5% by weight. The methacrylic resin having the above proportions has the characteristics of low hygroscopicity and excellent heat resistance.

More preferably, it is a copolymer comprising a monomer mixture containing 15 to 70% by weight of methacrylic acid alkyl ester (A) and 85 to 30% by weight of methacrylic acid alicyclic hydrocarbon ester (B). . For example, a methacrylic resin obtained by copolymerizing a monomer mixture containing 15% by weight or more of ester (A) and 85% by weight or more of ester (B) has a mechanical strength more suitable for optical materials.
Further, the methacrylic resin containing 70% by weight or less of the ester (A) and 30% by weight or more of the ester (B) is
In addition to the above characteristics, the rate of increase of the glass transition temperature becomes large, and the effect of improving heat resistance and low hygroscopicity is remarkable.

A known radical polymerization initiator can be used as a polymerization initiator in the copolymerization, and examples thereof include 2,2'-azobis (isobutyronitrile) and 1,1'-azobis (cyclohexanecarbonitrile). 2,2'-azobis (2,4-dimethylvaleronitrile), azo compounds such as azobisisobutanol diacetate; and organic peroxides such as lauroyl peroxide and di-tert-butyl peroxide. The amount of radical polymerization initiator used is about 0.001 to 1 mol% based on the total amount of the monomers.

Further, a chain transfer agent may be added to the polymerization system in order to control the molecular weight of the polymer. Examples of the chain transfer agent include tert-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan and n-dodecyl mercaptan (dodecanethiol). The amount used is, for example, about 1 mol% or less based on the total amount of the monomers.

Polymerization includes bulk polymerization, solution polymerization, suspension polymerization,
It can be carried out by a conventional method used for producing an acrylic polymer, such as emulsion polymerization. Specifically, in the case of bulk polymerization, for example, a method of preparing a partial copolymer from a monomer mixture, injecting it into a glass or stainless cell and polymerizing for several hours, generally called a casting method. By the method. Further, in the case of suspension polymerization or emulsion polymerization, for example, a dispersant or an emulsifier is previously dissolved or dispersed in water, a polymerization initiator and a chain transfer agent are dissolved therein, and the entire amount of the monomer is dispersed for polymerization. .

As the polymerization solvent, known solvents can be used,
For example, ether (cyclic ether such as tetrahydrofuran and dioxane), ester (methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, etc.), ketone (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), amide (N, N-dimethylacetamide) , N, N
-Dimethylformamide, etc.), sulfoxides (dimethylsulfoxide, etc.), alcohols (methanol, ethanol, propanol, etc.), hydrocarbons (aromatic hydrocarbons such as benzene, toluene, xylene, etc., aliphatic hydrocarbons such as hexane, fats such as cyclohexane). Cyclic hydrocarbon), water, and a mixed solvent thereof, and the like. The polymerization temperature can be appropriately selected within a range of, for example, about 130 to 150 ° C.

By the above method, a methacrylic resin having a glass transition temperature of, for example, 150 ° C. or higher (eg 150 to 200 ° C.), preferably 160 ° C. or higher (eg 160 to 200 ° C.) can be obtained.

When a methacrylic resin having such a glass transition temperature is used as an optical material, the heat resistance is greatly improved. As a result, even in the temperature range where conventional methacrylic resins cannot be used, The molded product is less likely to warp, and high dimensional stability can be obtained.

The water absorption of the methacrylic resin is 100.
% Relative humidity, for example, 0.5% or less (0 to 0.5
%). When a methacrylic resin having such low hygroscopicity is used as an optical material, it is possible to reduce the occurrence of cracks seen by repeated cycles of moisture absorption and drying, so that an optical material having more stable quality can be obtained. Can be provided.

Since the methacrylic resin of the present invention has a high glass transition temperature and a low water absorption rate at the same time as described above, it has a hygroscopic property in a wide temperature range from room temperature to around 80 ° C. Significantly reduced compared to polymers and the like. Therefore, it is possible to expand the application to a temperature range that could not be used conventionally.

The methacrylic resin of the present invention may contain additives such as a plasticizer, an oxidation stabilizer, a weather resistance stabilizer and a release agent, and these additives are added at the same time as a monomer mixture at the time of polymerization. It may be added to the polymerization system or may be added after the polymerization. The plasticizer can increase the mechanical strength required for optical material applications, and examples thereof include triphenyl phosphite, bis (cis-3,3,5-trimethylcyclohexyl) phthalate, and trioctadecyl phosphite. Can be mentioned. The amount of the plasticizer used is selected from the range of, for example, about 5 to 20% by weight, preferably about 8 to 15% by weight, based on the entire resin. If it is less than 5% by weight, the mechanical strength cannot be increased, and if it exceeds 20% by weight, the glass transition temperature is lowered. It is preferable to use 8% by weight or more in order to significantly increase the mechanical strength.

The methacrylic resin described above can be preferably used for the optical material of the present invention. Examples of optical materials include video disks, audio disks, computer information files, and information recording optical elements such as LCD light guide plates.

[0031]

The methacrylic resin of the present invention uses a specific methacrylic acid alicyclic hydrocarbon ester (B) as a monomer component, and therefore has low hygroscopicity, excellent heat resistance and dimensional stability. It has a low birefringence, and further exhibits sufficient mechanical strength by mixing a specific amount of methacrylic acid alkyl ester (A) and methacrylic acid alicyclic hydrocarbon ester (B) and copolymerizing them. it can. The methacrylic resin having the above characteristics is suitably used as an optical material.

[0032]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples. Example 1 An aqueous solution prepared by adding 80 g of a slurry of calcium phosphate [manufactured by Taihei Chemical Industry Co., Ltd.] to 5500 g of deionized water in advance was placed in a reaction tank made of stainless steel having an internal volume of 10 L equipped with a stirrer, and a single amount thereof was added thereto. A mixture of 1600 g of isobornyl methacrylate, 80 g of dimethyladamantyl methacrylate, and 720 g of methyl methacrylate as a body component, and lauroyl peroxide 6.2 as an initiator.
6 g, and 7.2 g of dodecanethiol as a chain transfer agent
Was added and suspended, and polymerization was carried out under the conditions of 70 ° C. and a stirrer rotation speed of 250 rpm. About 1 hour after the reaction, the reaction temperature rose to 76 ° C. After about 1 hour, the temperature was lowered to 70 ° C., and the temperature was raised to 100 ° C. After maintaining the temperature at 100 ° C. for 1 hour, the reaction tank was cooled, the aqueous layer was separated, washed with water, and dried to obtain a bead-shaped methacrylic resin. The resulting copolymer,
It was pelletized at 230 ° C. using a uniaxial extruder [trade name “PCM30”, manufactured by Ikegai Co., Ltd.] and dried at 80 ° C. for 12 hours using a hot air dryer. Then, using an injection molding machine [trade name "PS60E9A", manufactured by Nissei Plastic Industry Co., Ltd.], the pellets were heated to a cylinder temperature of 230 ° C
Injection molding under the condition of mold temperature 80 ℃, 500 × 800
X3 (mm) transparent flat plate, and 120 x 12 x 6 (m
A transparent rod of m) was obtained.

Example 2 The procedure of Example 1 was repeated, except that a mixture of 1150 g of isobornyl methacrylate, 50 g of dimethyladamantyl methacrylate and 1200 g of methyl methacrylate was used as a monomer component. A resin, a transparent flat plate and a transparent rod were obtained.

Example 3 In Example 2, the monomer mixture was further mixed with ADEKA STAB AO-40 (manufactured by Asahi Denka Kogyo) 3.8 as a plasticizer.
g and ADEKA STAB 3010 (manufactured by Asahi Denka Kogyo) 1.8
A methacrylic resin, a transparent flat plate and a transparent rod were obtained in the same manner as in Example 2 except that the solution containing 2 g was added to the aqueous solution containing calcium phosphate.

Comparative Example 1 The procedure of Example 1 was repeated except that a mixture of 2000 g of isobornyl methacrylate, 328 g of dimethyladamantyl methacrylate and 72 g of methyl methacrylate was used as the monomer component. A resin was obtained. Molding was carried out in the same manner as in Example 1 using the copolymer, but brittle and no molding test piece was obtained.

Comparative Example 2 In Example 1, 36 g of isobornyl methacrylate and dimethyladamantyl methacrylate 3 were used as the monomer components.
A methacrylic resin, a transparent flat plate and a transparent rod were obtained in the same manner as in Example 1 except that a mixture of 6 g and 2328 g of methyl methacrylate was used.

(Evaluation Test) [Refractive Index] With respect to the transparent flat plates obtained in Examples 1 to 3 and Comparative Example 2, the refractive index was measured according to ASTM D542. The results are shown in Table 1. [Total Light Transmittance and Haze Value] With respect to the transparent flat plates obtained in Examples 1 to 3 and Comparative Example 2, the total light transmittance and haze value were measured according to ASTM D1003. The results are shown in Table 1. [Birefringence] Regarding the transparent flat plates obtained from Examples 1 to 3 and Comparative Example 2, Optical Birefringen
ce Analyzer KOBRA-21ADH
(Oj Scientific Instrument
The value (length / length) obtained by dividing the retardation value measured with the thickness of the transparent flat plate was defined as birefringence. The results are shown in Table 1. [Glass Transition Temperature] With respect to the resin pellets obtained in Examples 1 to 3 and Comparative Example 2, a differential scanning calorimeter (DSC) was used.
Was used to measure the glass transition temperature. The results are shown in Table 1. [Heat Distortion Temperature] The heat distortion temperatures of the transparent rods obtained in Examples 1 to 3 and Comparative Example 2 were measured according to ASTM D648. The results are shown in Table 1. [Saturated Water Absorption] Regarding the transparent flat plates obtained in Examples 1 to 3 and Comparative Example 2, the saturated water absorption was measured according to ASTM D570. The results are shown in Table 1. [Bending Strength] The bending strength of the transparent rods obtained in Examples 1 to 3 and Comparative Example 2 was measured according to ASTM D790. The results are shown in Table 1.

[0038]

[Table 1] The transparent flat plate and transparent rod obtained from Examples 1 to 3 are
While maintaining the properties of conventional methacrylic resins such as refractive index and total light transmittance, the glass transition temperature and heat distortion temperature were greatly increased, and saturated water absorption and birefringence were suppressed to a lower level.
On the other hand, the transparent flat plate obtained from the comparative example had the same glass transition temperature and saturated water absorption as the conventional one, and no improvement was observed.

Continued front page    F-term (reference) 4J100 AL03P AL04P AL08Q BC04Q                       BC08Q BC09Q BC12Q CA04                       DA22 DA25 DA37 DA62 FA18                       FA19 FA20 FA21 JA36                 5D029 KA02

Claims (3)

[Claims] 1. (A) Methacrylic acid alkyl ester 5
˜95% by weight and (B) the alcohol portion of the ester is copolymerized with a monomer mixture containing 95 to 5% by weight of a methacrylic acid alicyclic hydrocarbon ester having an alicyclic hydrocarbon group having 8 or more carbon atoms. A methacrylic resin obtained by the method, wherein the methacrylic acid alicyclic hydrocarbon ester (B) is bornyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, dimethyladamantyl methacrylate, fentyl methacrylate, 1-menthyl methacrylate, And a methacrylic resin containing at least two compounds selected from methacrylic acid (3,3,5-trimethylcyclohexyl). 2. The methacrylic resin according to claim 1, wherein the methacrylic acid alkyl ester (A) is methyl methacrylate. 3. An optical material using the methacrylic resin according to claim 1 or 2.