JP2001226428A - Material for optical part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a material for optical parts, having improved low hygroscopicity and low birefringence and rapidly raised reliability as a high- density recording medium of next generation, optical lens, etc. SOLUTION: This material for optical materials uses an acrylic resin containing an alicyclic hydrocarbon group substituted with a 4-12C alkyl group in the molecular structure, represented by a copolymer between 4-tertiary butylcyclohexyl methacrylate and ethyl acrylate, as a main component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for optical parts having excellent low hygroscopicity and low birefringence.

[0002]

2. Description of the Related Art (Meth) acrylic resins are excellent in transparency and weather resistance, and have appropriate mechanical properties and moldability. Therefore, not only sheet materials and molding materials but also video disks, audio disks, computers, and the like. It is useful as an optical material for a write-once disc, an optical fiber, a camera lens, a pickup lens, or the like.

However, on the other hand, conventional (meth) acrylic resins have a high hygroscopicity and thus have the disadvantages of easily causing dimensional changes and warpage of molded articles. Since the optical material is not yet at a sufficient level, the information reading accuracy when used in an optical recording medium, an optical pickup lens, or the like cannot meet the recent demand for higher density.

[0004] Conventionally, as a method for imparting low hygroscopicity and low birefringence to a (meth) acrylic resin, for example, JP-A-58-5318 and JP-A-9-154 are known.
No. 01 proposes a method using cyclohexyl methacrylate as a comonomer.

[0005]

However, the (meth) acrylic resin obtained by the method disclosed in the above-mentioned patent publication exhibits low birefringence, but has a low level of moisture absorption to a level recently required. If it has not been reached, and it is attempted to use it for a high-density recording medium such as a large-capacity digital video disk, the effect is not sufficient and cannot be put to practical use. In particular,
The technology for improving the recording density of high-density recording media is constantly evolving, and slight dimensional changes in the recording medium itself and optical lenses due to moisture absorption and warpage of molded products cause malfunctions in signal reading, significantly increasing product reliability. There was a problem of spoiling. The problem to be solved by the present invention is to provide a material for an optical component that has improved low moisture absorption and low birefringence, and can dramatically improve the reliability as a next-generation high-density recording medium, an optical lens, and the like. it can.

[0006]

Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned problems, and as a result, have found that an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms has in its molecular structure. By using the introduced acrylic resin as the main component, it has been found that the low hygroscopicity and low birefringence of the molded product are dramatically improved, and that the performance required for the next-generation high-density recording medium can be exhibited. Thus, the present invention has been completed.

That is, the present invention is directed to an optical component characterized in that an acrylic resin having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms in a molecular structure is a main component. About the material.

The acrylic resin having an alicyclic hydrocarbon group substituted by an alkyl group having 4 to 12 carbon atoms in the molecular structure used in the present invention is a homopolymer of an acrylic monomer or an acrylic resin. An alicyclic hydrocarbon group which is a copolymer of a monomer and another radical polymerizable monomer, and is substituted at any position of the polymer by an alkyl group having 4 to 12 carbon atoms And, specifically,
(A) a homopolymer of an acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms; (b) a homopolymer substituted with an alkyl group having 4 to 12 carbon atoms; Copolymer of acrylic monomer having alicyclic hydrocarbon group and other radically polymerizable monomer, (c) acrylic monomer and other alkyl group having 4 to 12 carbon atoms With a radically polymerizable monomer having an alicyclic hydrocarbon group substituted with a, (d) an acrylic having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms Copolymers of monomers and other radically polymerizable monomers having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms, and the like can be given.

In the present invention, in particular, from the viewpoint of low hygroscopicity and low birefringence, (a) an acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms. Homopolymer, and (b) a copolymer of an acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms, and another radical polymerizable monomer Is preferred.

The acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms is not particularly limited, but the effect of the present invention is remarkable. In view of the above, an alkylcyclohexyl (meth) acrylate having a cyclohexyl group substituted with an alkyl group having 4 to 12 carbon atoms is preferable, and specifically, 2-tert-butylcyclohexyl (meth) acrylate 3-tert-butylcyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, 2-secondary-butylcyclohexyl (meth) acrylate, 4
-Secondary butylcyclohexyl (meth) acrylate, 2,4-di-tert-butylcyclohexyl (meth) acrylate, 2,4-di-secondary-butylcyclohexyl (meth) acrylate, 4-tert-amylcyclohexyl (meth) acrylate, 2 ,
4-di-tert-amyl cyclohexyl (meth) acrylate, 4-tert-octylcyclohexyl (meth) acrylate, 4- (1-cyclohexylethyl) -cyclohexyl (meth) acrylate, 4- (1
-Methyl-1-cyclohexylethyl) -cyclohexyl (meth) acrylate, nonylcyclohexyl (meth) acrylate, dodecylcyclohexyl (meth) acrylate and the like.

The above-mentioned alkylcyclohexyl (meth) acrylates are all industrially produced by a method of hydrogenating an alkylphenol into an alkylcyclohexanol and then subjecting it to (meth) acrylation by esterification or transesterification. From the viewpoint of industrial productivity, butylcyclohexyl (meth) acrylate, octyl (meth) acrylate and nonylcyclohexyl (meth) acrylate are preferable, and among them, 4-tert-butylcyclohexyl (meth) acrylate,
-Tertiary octyl cyclohexyl (meth) acrylate, nonylcyclohexyl (meth) acrylate are particularly preferred.

The acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms described above is an effective component for imparting useful performance as an optical material. As described above, the acrylic monomer used in the present invention may be a homopolymer (a) of this monomer as described above, but may be the above-mentioned copolymer (b), that is, having 4 to 4 carbon atoms. Various performances required for optical components by forming a copolymer of an acrylic monomer having an alicyclic hydrocarbon group substituted with an alkyl group of 12 and another radical polymerizable monomer The balance can be adjusted. In other words, in addition to low hygroscopicity and low birefringence, other radical polymerizable monomer groups for imparting heat resistance, transparency, and fluidity, which are the properties required for optical materials When,
Copolymerization at an appropriate ratio becomes possible.

The copolymer (b) has 4 carbon atoms.
The use ratio of the alkylcyclohexyl (meth) acrylate having a cyclohexyl group substituted with an alkyl group of from 12 to 12 is preferably at least 5% by weight, more preferably at least 10% by weight, based on the amount of all monomers used. Is preferable in that the resulting acrylic resin has a low moisture absorption and a good effect of improving low birefringence.

Here, the other radically polymerizable monomer used in the copolymer (b) is not particularly limited. For example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, 3,3,5
-(Meth) acrylate monomers such as trimethylcyclohexyl (meth) acrylate, and poly (meth) acrylate monomers obtained by (meth) acrylated polyhydric alcohols such as 1,6-hexanediol and hydrogenated bisphenol-A Styrene, styrene, butylstyrene, styrene-based monomers such as α-methylstyrene, maleimide monomers such as phenylmaleimide and cyclohexylmaleimide, and maleic acid.One of these may be used in combination. Also, a plurality of types may be used in combination. When used in combination, the same monomer such as methyl (meth) acrylate and ethyl (meth) acrylate may be used in combination, or a styrene monomer and a maleimide monomer may be used in combination. A combination of different monomers may be used.

Of these, (meth) acrylate monomers are particularly preferred because of their excellent transparency and moldability as optical parts, and particularly when used for high-density recording media, because of their low refractive index. preferable.

The polymerization method of the (meth) acrylic resin of the present invention is not necessarily specified, but a bulk polymerization method, a suspension polymerization method or an emulsion polymerization method is desirable from the viewpoint of productivity. Alternatively, an emulsion polymerization method is particularly desirable from the viewpoint of productivity and workability.

As the radical polymerization initiator, for example,
Azo compounds such as 2,2′-azobisisobutylnitrile and 1,1′-azobiscyclohexanecarbonitrile,
Ditertiary butyl peroxide, dicumyl peroxide, ditertiary butylperoxy-3,3
Organized oxides such as 5-trimethylcyclohexane, tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate, and benzoyl peroxide are exemplified.

The addition ratio of these polymerization initiators may be arbitrarily adjusted according to the molecular weight of the polymer to be obtained, but is generally 0.001 to 1 mol% based on the monomers. Further, a small amount of a chain transfer agent such as tertiary butyl mercaptan may be added for the purpose of controlling the molecular weight of the polymer.

The acrylic resin thus obtained is
Although the molecular weight is not limited, the weight average molecular weight is 1 in view of the balance between ease of molding and mechanical strength.
Range from 0000 to 500,000, especially 20,000
It is preferably in the range of 00 to 100,000.

The material for an optical component of the present invention uses the above-mentioned acrylic resin as a main component, and it is preferable to use the acrylic resin alone since the effect of the present invention is remarkable. An antioxidant or an ultraviolet absorber may be used in combination as long as the effect of the above is not impaired.

The materials of the present invention are specifically used for next-generation high-density recording medium substrates typified by DVDs, optical pickup lenses, optical fibers, photosensitive layer binders for photosensitive drums, and the like. Among these, it is particularly useful as a next-generation high-density recording medium substrate and an optical pickup lens, and is also useful as a next-generation high-density recording medium substrate because of its low refractive index.

Next, the present invention will be described in more detail by way of examples, but the following examples are representative examples, and the present invention is not limited thereto.

[0023]

Example 1 In a pressure-resistant flask equipped with a stirrer, 600 parts by weight of ion-exchanged water, 366 parts by weight of 4-tert-butylcyclohexyl methacrylate, 34 parts by weight of ethyl acrylate,
As a suspension polymerization dispersant, 3 parts by weight of a hydroxyapatite body of tribasic calcium phosphate, 0.024 parts by weight of sodium dodecylbenzenesulfonate, 75 parts by weight of an 8% by weight aqueous solution of polyvinyl alcohol, and 0.1 parts by weight of calcium hydroxide
2 parts by weight, 1.6 parts by weight of tertiary butyl peroxy-2-ethylhexanoate as a polymerization initiator and 0.4 parts by weight of tertiary butyl peroxybenzoate were charged, and the temperature was raised to 75 ° C. while stirring. The reaction was performed at 75 ° C. for 4 hours. Thereafter, the reaction temperature was changed to 85 ° C., and the reaction was further performed for 2 hours. Thereafter, the flask was sealed, the reaction temperature was changed to 105 ° C., and the reaction was further performed for 2 hours. After the completion of the reaction, the suspension was cooled to room temperature, and 10 parts by weight of 36.5% hydrochloric acid was added for the purpose of decomposing calcium phosphate attached to the surface of the suspended particles. The suspended particles were separated from the dispersion medium by filtration to obtain wet particles. The wet particles are
After washing with 0 parts by weight of ion-exchanged water, drying was performed for 24 hours with a dryer set at 80 ° C. to obtain 382 parts by weight of polymer particles. The obtained polymer particles were supplied to an extruder having a cylinder temperature of 280 ° C. and pelletized.

After drying the pellets at 80 ° C. for 24 hours,
Injection molding was performed at a cylinder temperature of 280 ° C. and a mold temperature of 60 ° C. to obtain a test piece of 50 × 100 × 3 mm. The test piece was dried at 80 ° C. for 24 hours, weighed, then immersed in ion-exchanged hot water adjusted to 95 ° C. for 24 hours, and weighed again. When the saturated water absorption was measured from the weight change before and after the immersion by the following equation, the saturated water absorption was 0.4%. Saturated water absorption (%) = (weight after immersion−weight before immersion) / (weight before immersion) × 100 Next, a total length of 200 m is obtained by injection molding of pellets.
After obtaining a test piece having a thickness of 3.2 mm, a thickness of 3.2 mm, and a width of 12.7 mm, a birefringence was evaluated by measuring the optical path difference at the center with a polarizing microscope. The birefringence was 3 nm or less.

Example 2 An experiment was conducted in the same manner as in Example 1 except that 183 parts by weight of 4-tert-butylcyclohexyl methacrylate and 183 parts by weight of methyl methacrylate were used instead of 366 parts by weight of 4-tert-butylcyclohexyl methacrylate. Was performed to obtain 379 parts by weight of polymer particles. When a test piece obtained from the polymer particles was evaluated, the saturated water absorption was 1.0% and the birefringence was 3 nm or less.

Comparative Example 1 An experiment was carried out in the same manner as in Example 1 except that 366 parts by weight of methyl methacrylate was used instead of 366 parts by weight of 4-tert-butylcyclohexyl methacrylate to obtain 379 parts by weight of polymer particles. . When a test piece obtained from the polymer particles was evaluated, the saturated water absorption was 2.4.
% And birefringence was 11 nm.

COMPARATIVE EXAMPLE 24 Example 1 was repeated except that instead of 366 parts by weight of tert-butylcyclohexyl methacrylate, 183 parts by weight of cyclohexyl methacrylate and 183 parts by weight of methyl methacrylate were used.
An experiment was carried out in the same manner as in the above to obtain 379 parts by weight of polymer particles. When a test piece obtained from the polymer particles was evaluated, the birefringence was 3 nm, but the saturated water absorption was 1.5%.
Met.

[0028]

According to the present invention, low moisture absorption and low birefringence are dramatically improved, and a material for an optical component having excellent reliability as a next-generation high-density recording medium or an optical component such as an optical lens. Can be provided.

Continued on front page F-term (reference) 4J100 AB02Q AB03Q AB04Q AJ09Q AL03Q AL08P AL08Q AM47Q AM48Q BC04P BC04Q CA01 CA04 DA37 DA63 FA03 JA33 JA35 JA36

Claims (5)

[Claims] 1. An optical component material comprising, as a main component, an acrylic resin having an alicyclic hydrocarbon group substituted with an alkyl group having 4 to 12 carbon atoms in a molecular structure. 2. An acrylic resin having 4 to 4 carbon atoms.
The optical component material according to claim 1, wherein the alicyclic hydrocarbon group substituted with 12 alkyl groups is a cyclohexyl group substituted with an alkyl group having 4 to 12 carbon atoms. 3. An acrylic resin having 4 to 4 carbon atoms.
3. The optical component material according to claim 1, wherein the 12 alkyl groups are a butyl group, an octyl group, a nonyl group, or a dodecyl group. 4. A homopolymer of an alkylcyclohexyl (meth) acrylate having an acrylic resin having a cyclohexyl group substituted with an alkyl group having 4 to 12 carbon atoms,
Or a copolymer of an alkylcyclohexyl (meth) acrylate having a cyclohexyl group substituted with an alkyl group having 4 to 12 carbon atoms and another radically polymerizable monomer. Materials for optical components. 5. The material for an optical component according to claim 4, wherein the other radically polymerizable monomer is a (meth) acrylate monomer.