JP2000044614A - Production of nonbirefringent optical resin and optical element using resin obtained by the production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an optical resin for supplying a lens having excellent nonbirefringent properties, heat resistance and low moisture absorption, etc., and to obtain an optical element having excellent nonbirefrigent properties, heat resistance and low moisture absorption free from striae using the resin. SOLUTION: This method for producing a nonbirefringent optical resin comprises adding (F) 0.1-2.0 wt.% of a glycerol fatty acid ester of the formula (R is a 5-30C aliphatic hydrocarbon group) to 100 wt.% of the total of monomer components of (A) 5-40 wt.% of a methacrylic acid ester or acrylic ester containing a 5-22C alicyclic hydrocarbon group at the ester part, (B) 50-80 wt.% of methyl (meth)acrylate, (C) 5-40 wt.% of an N-substituted maleimide, (D) 0-30 wt.% of benzyl methacrylate and (E) 0-10 wt.% of a monomer copolymerizable with the components A to D and copolymerizing the monomers in a monomer mixing ratio to make the absolute value of orientation birefringence of the obtained resin <1×10-6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-birefringent optical resin capable of obtaining a molded product such as a striae-free lens suitably used for various optical elements, and a method for producing the same. The present invention relates to an optical element using a resin obtained by the method described above.

[0002]

2. Description of the Related Art Conventionally, lenses, prisms, optical disks,
Glass has been used for optical elements such as LCD substrates. However, in recent years, plastics have been used for weight reduction and miniaturization. Polystyrene, polycarbonate, polymethyl methacrylate, styrene-methyl methacrylate copolymer, and the like are generally known as plastics used for optical elements. But,
Since polystyrene and polycarbonate have an aromatic ring in the molecule, birefringence is likely to occur due to orientation distortion, and it is necessary to devise a molding die as shown in JP-A-61-14617. So far,
Polymethyl methacrylate has been mainly used as an optical element material.

Polymethyl methacrylate has a small photoelastic coefficient and is relatively unlikely to cause birefringence due to orientation distortion, and is therefore used for optical elements that do not require relatively high precision, such as finder lenses and CD pickup lenses. It has been.

However, in recent years, there has been a demand for optical elements that require higher precision. In particular, laser pickup lenses for write-once optical disks using laser light, laser pickup lenses for magneto-optical disks, write-once optical disks, magneto-optical disks, etc., have not only low birefringence but also near-zero birefringence near the gate. Is required.

[0005] A birefringence of the member to be used is most important in a liquid crystal element. As is well known, liquid crystal elements have a structure that controls the transmission and non-transmission of light by rotating the plane of polarization of the polarized light by the liquid crystal layer between the polarizer and crossed Nicol or parallel Nicol polarizer. Therefore, in the liquid crystal element, the birefringence of each member constituting the liquid crystal element becomes a serious problem, which hinders widespread use of the optical resin in the liquid crystal element.

Further, in an optical element which is a thick molded article such as a prism element used for a liquid crystal projector or the like, not only non-birefringence is required but also striae and flow marks inside the molded article. It is also required that density unevenness does not exist.

On the other hand, polymethyl methacrylate can reduce the birefringence to some extent depending on the molding conditions, but the birefringence in the vicinity of the gate does not become zero and is used for the above-mentioned optical element requiring high precision. It is not possible.

For the purpose of reducing birefringence, a monomer capable of obtaining a resin having a positive photoelastic coefficient and a monomer capable of obtaining a resin having a negative photoelastic coefficient are used as essential raw materials. Elastic modulus is -1 × 10 ^-13 cm ² / dyne or more, + 1 ×
A method of copolymerizing so as to be 10 ^-13 cm ² / dyne or less (JP-A-60-185236), copolymerization of methyl methacrylate, alkyl methacrylate having an alkyl group having 3 to 8 carbon atoms, and styrene (Japanese Unexamined Patent Publication No.
0-250010 and JP 61-76509 JP), methyl methacrylate, tricyclo [5.2.1.0 ^{2, 6]} dec-8-yl and a method of copolymerizing styrene (JP JP-A-62-246914), a monomer capable of forming a homopolymer having a positive birefringence (trifluoroethyl methacrylate, benzyl methacrylate, etc.) and a monomer capable of forming a homopolymer having a negative birefringence (methyl methacrylate, etc.) ) (JP-A-2-129211),
A method of copolymerizing methyl methacrylate with a compound having an unsaturated double bond having a photoelastic coefficient opposite to that of polymethyl methacrylate when it is a homopolymer (JP-A-4-76013), With 5 carbon atoms
Methacrylate or acrylate having 22 alicyclic hydrocarbon groups, methyl methacrylate, N-
A method of copolymerizing 5 to 40% by weight of substituted maleimide and benzyl methacrylate has been proposed.

[0009]

These conventional methods are:
Although they have each produced a certain effect, there are still many aspects that are not sufficient. For example, the above, and methods, when injection molding, it is impossible to completely eliminate birefringence, birefringence due to stress strain remains near the gate, is insufficient as a non-birefringent material. is there.

[0010] The above-mentioned methods include a combination thereof, wherein methyl methacrylate (MMA) and trifluoromethacrylate (3FMA) are included.
In the method using the monomer mixture of (2), the latter material (3F
MA) is a very expensive material.

In addition, any of a method of copolymerizing a monomer mixture of methyl methacrylate (MMA) and trifluoroethyl methacrylate (3FMA) and a method of copolymerizing a monomer mixture of methyl methacrylate (MMA) and benzyl methacrylate (BZMA) are used. ,
Unless the mixing ratio of trifluoroethyl methacrylate (3FMA) or benzyl methacrylate to methyl methacrylate is considerably increased, the development of orientation birefringence cannot be suppressed. That is, the mixing ratio necessary to cancel the orientation birefringence is MMA / 3FMA = 50 in the former case.
/ 50 (% by weight /% by weight), in the latter case MMA / BZ
MA = 80/20 (% by weight /% by weight). For this reason, the obtained material cannot have the same properties as PMMA, and is inferior in heat resistance and transparency as compared with PMMA.

On the other hand, in the above method, materials which are satisfactory as various optical elements can be obtained in terms of characteristics such as heat resistance and transparency, which are problems in the above method.
When an optical element which is a thick molded article such as a prism element used for a liquid crystal projector or the like is molded, density irregularities such as striae are present inside the molded article, which hinders use in these applications.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides an optical resin which is excellent in non-birefringence, heat resistance and low moisture absorption and is capable of obtaining a molded article such as a lens without striae. An object of the present invention is to provide a production method, and to provide an optical element which is excellent in non-birefringence, heat resistance and low hygroscopicity and has no striae using a resin obtained by the production method.

[0014]

According to the present invention, the following monomer component (F) is contained with respect to a total amount of 100% by weight of a monomer mixture comprising the following monomer components (A) to (E). The present invention also relates to a method for producing a non-birefringent optical resin, which is characterized in that the obtained resin is copolymerized at a monomer mixing ratio such that the absolute value of the orientation birefringence is less than 1 × 10 ⁻⁶ . (A) 5 to 40% by weight of a methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, (B) 50 to 50% of methyl methacrylate
80% by weight, (C) 5 to 40% by weight of N-substituted maleimide, (D) 0 to 30% by weight of benzyl methacrylate,
(E) 0 to 10% by weight of a monomer copolymerizable with (A) to (D) and (F) 0.1 to 2.0% by weight of a glycerin fatty acid ester represented by the following general formula (I). .

Embedded image Here, R represents an aliphatic hydrocarbon group having 5 to 30 carbon atoms.

In the present invention, the monomer component (F): the glycerin fatty acid ester represented by the general formula (I) is at least one selected from the group consisting of monoglycerides of palmitic acid, stearic acid, arachiic acid and behenic acid.
Preferably, it is a compound of the species.

In the present invention, the monomer component (A): a methacrylate or an acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion is selected from cyclohexyl methacrylate and isobornyl methacrylate. , Norbornyl methacrylate, norbornylmethyl methacrylate, tricyclomethacrylate [5.
At least one compound selected from the group consisting of 2.1.0 ^2,6 ] dec-8-yl and tricyclo [5.2.1.0 ^2,6 ] dec-4-methyl methacrylate preferable.

In the present invention, the monomer component (C): N-substituted maleimide is N-methylmaleimide,
N-ethylmaleimide, N-propylmaleimide, N-
i-propylmaleimide, N-butylmaleimide, N-
i-butylmaleimide, Nt-butylmaleimide, N
It is preferably at least one compound selected from the group consisting of -cyclohexylmaleimide, N-laurylmaleimide and N-phenylmaleimide.

The present invention also relates to an optical element using the non-birefringent optical resin obtained by the above-mentioned production method.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a non-birefringent optical resin according to the present invention and an optical element using the resin obtained by this method will be described in detail. Monomer component (A) used in the present invention: Examples of the methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion include cyclopentyl acrylate, cyclohexyl acrylate, and acrylic Methylcyclohexyl acrylate, trimethylcyclohexyl acrylate, norbornyl acrylate, norbornylmethyl acrylate, cyanonorbornyl acrylate, isobornyl acrylate, bornyl acrylate, menthyl acrylate, fentyl acrylate, adamantyl acrylate,
Dimethyl adamantyl acrylate, tricyclo [5.2.1.0 ^2,6 ] dec-8-yl acrylate, tricyclo [5.2.1.0 ^2,6 ] deca-4-methyl acrylate,
Cyclodecyl acrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, cyanonorbornyl methacrylate, phenylnorbornyl methacrylate, isobornyl methacrylate Bornyl methacrylate, menthyl methacrylate, fentyl methacrylate, adamantyl methacrylate, dimethyl adamantyl methacrylate, tricyclo [5.2.1.0 ^2,6 ] dec-8-yl, tricyclomethacrylate [5.2] .1.0 ^2,6 ] dec-4-methyl, cyclodecyl methacrylate and the like. Of these, from the viewpoint of low hygroscopicity, cyclopentyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, isobornyl methacrylate, bornyl methacrylate, menthyl methacrylate , Fentyl methacrylate,
Adamantyl methacrylate, dimethyl adamantyl methacrylate, tricyclomethacrylate [5.2.1.0
^2,6 ] dec-8-yl, tricyclomethacrylate [5.
2.1.0 ^2,6 ] dec-4-methyl, cyclodecyl methacrylate and the like are preferred. Further, more preferable ones in terms of heat resistance and low hygroscopicity include cyclohexyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, norbornylmethyl methacrylate, and tricyclomethacrylate [5.2.1.0 ^2,6. ] Dec-8-yl and tricyclo [5.2.1.0 ^2,6 ] deca-4-methyl methacrylate.

The monomer component (C) used in the present invention includes N-substituted maleimide, for example, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide,
Ni-propylmaleimide, N-butylmaleimide,
Ni-butylmaleimide, Nt-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N-
(4-chlorophenyl) maleimide, N- (4-bromophenyl) phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenylmaleimide, N- (2-methoxyphenyl) maleimide, N-
(2,4,6-trimethylphenyl) maleimide, N-
(4-benzylphenyl) maleimide, N- (2,4,
6-tribromophenyl) maleimide and the like.
Preferred from the viewpoint of non-birefringence and heat resistance are N
-Methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-
Butyl maleimide, N-cyclohexyl maleimide, N
-Laurylmaleimide and N-phenylmaleimide.

Monomer component (E) used in the present invention: The monomer copolymerizable with the monomer components (A) to (D) includes transparency, non-birefringence and heat resistance of the copolymer. If it does not impair the properties and low hygroscopicity, there is no particular limitation, specifically,
Methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, i-butyl acrylate,
T-butyl acrylate, pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, octadecyl acrylate, butoxyethyl acrylate, phenyl acrylate, benzyl acrylate, acrylic Naphthyl acid,
Glycidyl acrylate, acrylates such as 2-hydroxyethyl acrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, n-methacrylate -Methacrylic acid such as hexyl, 2-ethylhexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, butoxyethyl methacrylate, phenyl methacrylate, naphthyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate Esters, α-methylstyrene, α-ethylstyrene, α-fluorostyrene, α-chlorostyrene, α-bromostyrene, fluorostyrene, chlorostyrene, bromostyrene, methylstyrene, Aromatic vinyl compounds such as methoxystyrene, acrylamide, methacrylamide, N-
(Meth) acrylamides such as dimethylacrylamide, N-diethylacrylamide, N-dimethylmethacrylamide, N-diethylmethacrylamide, calcium acrylate, barium acrylate, lead acrylate, tin acrylate acrylate, zinc acrylate, methacryl (Meth) such as calcium acrylate, barium methacrylate, lead methacrylate, tin methacrylate, zinc methacrylate, etc.
Examples thereof include metal salts of acrylic acid, unsaturated fatty acids such as acrylic acid and methacrylic acid, and vinyl cyanide compounds such as acrylonitrile and methacrylonitrile. These can be used alone or in combination of two or more.

The monomer component (F) used in the present invention includes glycerin fatty acid esters, such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid. And aliphatic carboxylic acid monoglycerides such as behenic acid, lignoceric acid, cerotic acid, montanic acid, melicic acid, linoleic acid, linolenic acid and oleic acid. Among them, monoglycerides of palmitic acid, stearic acid, arachiic acid and behenic acid are preferred from the viewpoint of transparency and anti-striae. These can be used alone or in combination of two or more.

The monomer component (A) used in the present invention: The amount of the methacrylic acid ester or acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion is determined based on the total amount of the monomer mixture. 5 to 4
0% by weight, and more preferably 10 to 40% by weight from the viewpoint of hygroscopicity. If the content of the alicyclic (meth) acrylate is less than 5% by weight, the birefringence is large,
The hygroscopicity increases, and if it exceeds 40% by weight, the mechanical strength decreases.

The amount of the monomer component (B): methyl methacrylate used in the present invention is 100 parts by weight of the total amount of the monomer mixture.
The weight percentage is 50 to 80% by weight, preferably 60 to 75% by weight. If the amount of methyl methacrylate is less than 50% by weight, the mechanical strength decreases, and if it exceeds 80% by weight, problems occur in non-birefringence, heat resistance and low moisture absorption.

The amount of the monomer component (C) used in the present invention: N-substituted maleimide is 100 parts by weight based on the total amount of the monomer mixture.
The weight percentage is 5 to 40 weight%, and preferably 15 to 30 weight% from the viewpoint of birefringence. If the compounding amount of the N-substituted maleimide is less than 5% by weight, birefringence is large,
If the glass transition temperature is lowered, and if it exceeds 40% by weight, the reactivity is reduced, the residual monomer is increased, and the birefringence is also increased.

The amount of the monomer component (D) used in the present invention: benzyl methacrylate is adjusted so that the total amount of the monomer mixture is 10%.
0% by weight is 0 to 30% by weight, and preferably 4 to 20% by weight in view of heat resistance and birefringence. If the amount of benzyl methacrylate exceeds 30% by weight,
The glass transition temperature decreases.

The monomer component (E) used in the present invention: The amount of the monomer copolymerizable with the monomer components (A) to (D) is as follows:
Assuming that the total amount of the monomer mixture is 100% by weight, it is 0 to 10% by weight, preferably 0 to 5% by weight. If the amount of the monomer component (E) exceeds 10% by weight, heat resistance and non-birefringence will decrease.

The amount of the monomer component (F): glycerin fatty acid ester used in the present invention is 0.1 to 2.0% by weight based on 100% by weight of the total amount of the monomer mixture.
From 0.2 to 1.0% by weight is preferred from the viewpoint of striae prevention. The amount of glycerin fatty acid ester is 0.1
If the amount is less than the weight%, the effect of preventing the occurrence of stria is low,
If it exceeds 2.0% by weight, heat resistance is reduced and silver streaks are liable to occur on the surface of the molded product. Here, striae refers to density unevenness (transparent or white streaks) generated inside a thick molded product, and silver streak refers to silver streaks (transparent molded streaks) generated on a molded product surface. In the case of a product, it means a transparent line.

In the present invention, the method of obtaining the monomer compounding ratio in which the absolute value of the orientation birefringence of the obtained optical resin is less than 1 × 10 ⁻⁶ is determined by using the polymer of each compounding ratio obtained by suspension polymerization. , A film of about 50 μm was prepared and stretched twice (stretching temperature: 90 ° C.), and the absolute value of birefringence was 1
It is performed by searching for a compounding ratio of less than × 10 ⁻⁶ .

As a polymerization method for producing the non-birefringent optical resin according to the present invention, existing methods such as bulk polymerization, suspension polymerization, emulsion polymerization and solution polymerization can be applied. For an optical element, bulk polymerization is preferable from the viewpoint of mixing impurities into the resin, and suspension polymerization is preferable from the viewpoint of handling as a product.

In carrying out the polymerization in the present invention, a polymerization initiator can be used. Examples of the polymerization initiator include benzoyl peroxide, lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-3, Organic peroxides such as 3,5-trimethylcyclohexane, azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile,
Conventional radical polymerization such as azo compounds such as azobiscyclohexanone-1-carbonitrile and azodibenzoyl; water-soluble catalysts such as potassium persulfate and ammonium persulfate; and redox catalysts using a combination of peroxides or persulfates and a reducing agent. Any of the above can be used. The polymerization initiator is preferably used in a range of 0.01 to 10% by weight based on the total amount of the monomers.

Further, in the present invention, it is preferable to add a mercaptan-based compound, thioglycol, carbon tetrachloride, α-methylstyrene dimer, or the like as necessary as a molecular weight regulator.

The polymerization temperature in the present invention is from 0 to 200 ° C.
The temperature can be appropriately selected between 50 and 120 ° C.

In the present invention, the suspension polymerization is carried out in an aqueous medium, and is carried out by adding a suspending agent and, if necessary, a suspending aid. Examples of the suspending agent include water-soluble polymers such as polyvinyl alcohol, methylcellulose and polyacrylamide, and poorly soluble inorganic substances such as calcium phosphate and magnesium pyrophosphate. 0.03 to 1% by weight, and the hardly soluble inorganic substance is 0.05 to 0.5% by weight based on the total amount of the monomers.
It is more preferred to use.

As the suspending aid in the present invention, there is an anionic surfactant such as sodium dodecylbenzenesulfonate. When a sparingly soluble inorganic substance is used as the suspending agent, the suspending aid is used. Is preferred. Suspension aids,
It is preferable to use 0.001 to 0.02% by weight based on the total amount of the monomers.

The molecular weight of the non-birefringent optical resin obtained by the present invention is not particularly limited, but the weight average molecular weight (in terms of polystyrene) is 10,000.
Those having a range of 0 to 1,000,000 are preferable, and those having a range of 100,000 to 300,000 are more preferable from the viewpoint of heat resistance and moldability.

The non-birefringent optical resin of the present invention is preferably made of a phenol-based, phosphite-based, thioether-based antioxidant or an aliphatic antioxidant from the viewpoints of deterioration prevention, thermal stability, moldability and processability. Release agents such as alcohols, fatty acid esters, phthalic acid esters, triglycerides, fluorine surfactants, metal salts of higher fatty acids, and other lubricants, plasticizers, antistatic agents, ultraviolet absorbers, flame retardants, heavy metal deactivators Etc. can be added.

In the present invention, the application of the non-birefringent optical resin to the optical element can be performed by a known method such as injection molding, compression molding, micromolding, floating molding, low-links, or casting. A molding method can be used. In the casting method, after partially proceeding the polymerization, it is also possible to obtain a molded article of the non-birefringent optical resin according to the present invention by pouring the mixture into a mold and continuing the polymerization.

The surface of the molded article obtained by the above-described molding method is coated with an inorganic compound such as MgF ₂ or SiO ₂ by a vacuum evaporation method, a sputtering method, an ion plating method, or the like. Organic silicon compounds such as silane coupling agents, vinyl monomers, melamine resins, epoxy resins, fluororesins,
By hard coating a silicone resin or the like, moisture resistance, optical properties, chemical resistance, abrasion resistance, anti-fog, and the like can be improved.

Examples of the optical element in the present invention include a lens and finder for a general camera, a lens for a video camera, an objective lens for a laser pickup, a diffraction grating, a hologram, and a collimator lens, an fθ lens for a laser printer, a cylindrical lens. Lenses, polygon lenses and projection TV lenses, multi-lenses for liquid crystal projectors, relay lenses, condenser lenses, projection lenses, Fresnel lenses, lenses for spectacles, etc., compact discs (CD, CD-
ROM, etc.), mini disk (MD), DVD disk substrate, LCD substrate, polarizing film transparent resin sheet,
Liquid crystal element members such as retardation films, light diffusion films, and liquid crystal element bonding adhesives, projector screens,
Optical filters, optical fibers, optical waveguides, prisms,
And a lens for a photoelectric conversion element.

The non-birefringent optical resin obtained by the present invention is particularly suitable for a thick molded product such as a prism element for a liquid crystal projector.

[0042]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. The water-soluble polymer (a) (polymethacrylate) used as a suspending agent in the examples was synthesized by the following method.

Synthesis of Water-Soluble Polymer (a) 5 g of methyl methacrylate, 12 g of 2-hydroxyethyl methacrylate, 23 g of potassium methacrylate and 360 g of deionized water were placed in a separable flask having an inner volume of 500 ml, and N ₂ gas was added for 30 minutes. To remove the air in the system, then heat the system in a water bath and stir the system temperature to 65 ° C.
And 0.06 g of potassium persulfate was added. Polymerization was carried out at the same temperature for 5 hours, followed by heating to 90 ° C. and stirring for 2 hours to obtain a jelly-like water-soluble polymer (a).

Example 1 Tricyclo [5.2.1.0 ^2,6 ] decamethacrylate
8-yl 100 g, methyl methacrylate 1500 g, N
-400 g of cyclohexylmaleimide, 8 g of lauroyl peroxide, 4 g of n-octylmercaptan, and 10 g of stearic acid monoglyceride as a glycerin fatty acid ester
g was dissolved to obtain a monomer mixture. 0.1 g of the above jelly-like water-soluble polymer (a) and 2500 g of deionized water are added as suspending agents to a 5-liter separable flask equipped with a stirrer and a condenser, and then disodium hydrogen phosphate-phosphoric acid is added. A buffer solution combined with sodium dihydrogen was added and stirred, and the pH was adjusted to 7.2 to obtain a suspension medium. The above-mentioned monomer mixture was added thereto with stirring, and the mixture was polymerized at 60 ° C. for 3 hours and then at 98 ° C. for 2 hours under a nitrogen atmosphere at a rotational speed of 240 rpm to obtain resin particles (polymerization rate:
It was 99% by weight.) The resin particles are washed with water, dehydrated and dried, and using an injection molding machine IS-50EP manufactured by Toshiba Machine Co., Ltd., cylinder temperature 260 ° C., injection speed 60 cm ³ / sec,
Molding was performed at a mold temperature of 90 ° C. to obtain a test piece for property evaluation.

Examples 2 to 6 and Comparative Examples 1 to 7 Using monomers and fatty acid esters having the composition ratios shown in Table 1,
In the same manner as in Example 1, a test piece for characteristic evaluation was obtained.

For the resin particles and test pieces obtained in Examples 1 to 6 and Comparative Examples 1 to 7, the orientation birefringence, the birefringence of the molded product, the saturated water absorption, the glass transition temperature (hereinafter abbreviated as Tg), and the pulse Table 1 shows the results of examining the processing conditions. The evaluation was performed by the following method. (1) Orientation birefringence 1 g of resin particles of each mixing ratio obtained by suspension polymerization were dissolved in 6 g of tetrahydrofuran, applied on a glass substrate, and the surface was made uniform using a knife coater. After drying this film, peel it off from the glass
m was prepared. Next, this film was stretched twice (stretching temperature: 90 ° C.), and the birefringence was measured. (2) Birefringence of molded article An ellipsometer (AEP-Shimadzu Corporation) using a He-Ne laser was used for a test piece of 50 × 40 × 3 (mm).
100), the phase difference (single pass) was measured for the measurement point A in FIG. 1 and the birefringence per thickness was calculated based on the following equation 1.

(Equation 1) (3) Saturated water absorption A test piece of 20 × 15 × 5 (mm) was dried, its weight was measured, and then it was left in water at 70 ° C. to allow saturated water absorption.
The weight was measured, and the saturated water absorption was calculated by the following equation (2).

(Equation 2) (4) Glass transition temperature (Tg) The obtained resin particles were measured by a differential scanning calorimeter (Rigaku Thermo Co., Ltd.).
Plus DSC8230), the glass transition temperature (Tg) was measured. (5) Striae condition 50 × 40 × 6 (mm) test piece 1 obtained by continuous molding
The presence of striae (white streak-like lines) inside the molded article was visually confirmed for 0 pieces. ：: no striae, Δ: striae in 1 to 5 cells, ×: 6 to 10
Individual with stria

[0048]

[Table 1]

In Table 1, MMA is methyl methacrylate, and TCDMA is tricyclomethacrylate [5.2.
1.0 ^2,6 ] dec-8-yl, CHMI is N-cyclohexylmaleimide, BZMA is benzyl methacrylate,
SMG indicates stearic acid monoglyceride, and OMG indicates oleic acid monoglyceride.

[0050]

According to the present invention, there is provided a method for producing an optical resin which provides a lens having excellent non-birefringence, heat resistance and low moisture absorption, and non-birefringence, heat resistance and low moisture absorption using this resin. An optical element having excellent striae and having no striae is provided.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing a test piece for measuring birefringence of a molded product used in Examples.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/24 526 G11B 7/24 526B 11/10 511 11/10 511A F-term (Reference) 4J011 FA07 FB19 GA05 GB07 JA02 JA04 JA06 JA07 JA08 JA13 JB26 NA12 NA25 NA28 PA25 PA30 PA69 PA74 PB40 PC07 PC08 4J100 AB03T AB04T AB07T AB08T AB09T AB10T AJ02T AK13T AL03P AL03T AL04T AL08Q AL08S AL08T AL09T AL10TAMTBA01 AM01 AM15 BA15 AM01 AM15 AM15 BB07T BC03Q BC04Q BC04R BC07Q BC08Q BC09Q BC43R BC43S BC43T BC45R BC49T CA03 CA05 CA06 CA27 DA63 FA21 JA32 JA33 JA36 5D029 KA02 5D075 EE03 FG15 GG16

Claims (5)

[Claims] An orientation of a resin obtained by containing the following monomer component (F) with respect to a total amount of 100% by weight of a monomer mixture comprising the following monomer components (A) to (E): A method for producing a non-birefringent optical resin, comprising copolymerizing at a monomer mixing ratio such that the absolute value of birefringence is less than 1 × 10 ⁻⁶ . (A) 5 to 40% by weight of a methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, (B) 50 to 50% of methyl methacrylate
80% by weight, (C) 5 to 40% by weight of N-substituted maleimide, (D) 0 to 30% by weight of benzyl methacrylate,
(E) 0 to 10% by weight of a monomer copolymerizable with (A) to (D) and (F) 0.1 to 2.0% by weight of a glycerin fatty acid ester represented by the following general formula (I). Embedded image Here, R represents an aliphatic hydrocarbon group having 5 to 30 carbon atoms. 2. The composition according to claim 1, wherein the monomer component (F): the glycerin fatty acid ester is at least one compound selected from the group consisting of monoglycerides of palmitic acid, stearic acid, arachiic acid and behenic acid. Manufacturing method of birefringent optical resin. 3. The monomer component (A): a methacrylic acid ester or an acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in an ester portion thereof, such as cyclohexyl methacrylate, isobornyl methacrylate, and methacrylic acid. Norbornyl, norbornylmethyl methacrylate,
Methacrylic acid tricyclo [5.2.1.0 ^{2, 6]} deca -
8-yl and tricyclomethacrylate [5.2.1.0
^{2. The} method for producing a non-birefringent optical resin according to claim 1, which is at least one compound selected from the group consisting of ^2,6 ] dec-4-methyl. 4. The monomer component (C), wherein the N-substituted maleimide is N-methylmaleimide, N-ethylmaleimide,
Selected from the group consisting of N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide, N-laurylmaleimide and N-phenylmaleimide The method for producing a non-birefringent optical resin according to claim 1, which is at least one compound selected from the group consisting of: 5. An optical element using the non-birefringent optical resin obtained by the production method according to claim 1. Description: