JP2002012728A - Non-birefringent optical resin composition and optical element prepared therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical resin composition excellent in non-birefringence, heat resistance, low moisture absorption and releasability from molds, and an optical element prepared from the composition. SOLUTION: There is provided a non-birefringent optical resin composition which is prepared by copolymerizing 5-40 pts.wt. of a methacrylate or acrylate ester having a 5-22C alicyclic hydrocarbon group in the alcoholic moiety, 50-80 pts.wt. of methyl methacrylate, 5-40 pts.wt. of an N-substituted maleimide, 0-30 pts.wt. of benzyl methacrylate and 0-10 pts.wt. of a monomer copolymerizable with these, the total being 100 pts.wt., in such composition ratios that the absolute value of the orientational birefringence of the resultant resin may become 1×10-6, and comprises 0.05-2.0 wt.%, based on the total of the monomers, of a fatty amide or ester which has an endothermic peak temperature of 70 deg.C or above as measured by a differential scanning calorimeter, and an optical element prepared from the composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-birefringent optical resin composition having good releasability, which is suitably used for various optical elements, and an optical element using the same.

[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. As for poly (methacrylate), 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, a laser pickup lens for mini discs using laser light, DV
Laser pickup lenses for D etc. are required not only to have low birefringence but also to have a birefringence near zero near the gate.Since polymethyl methacrylate does not have zero birefringence near the gate,
It cannot be used for such an optical element.

[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.

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. Copolymerization so that the modulus of elasticity is -1 × 10 ^-13 cm ² / dyne or more and + 1 × 10 ^-13 cm ² / dyne or less (JP-A-60-185236), methyl methacrylate, carbon number A method of copolymerizing an alkyl methacrylate having an alkyl group of 3 to 8 and styrene (JP-A-60-25010 and JP-A-61-76509), methyl methacrylate,
Tricyclo [5.2.1.0 ^2,6 ] methacrylate
Method for copolymerizing 8-yl and styrene (Japanese Patent Application Laid-Open No. Sho 62-62)
246914), a monomer capable of forming a homopolymer having positive birefringence (trifluoroethyl methacrylate, benzyl methacrylate, etc.) and a monomer capable of forming a homopolymer having negative birefringence (methyl methacrylate, etc.) Copolymerization method (JP-A-2-129)
No. 211), a method of copolymerizing a compound having an unsaturated double bond whose photoelastic coefficient is opposite to that of polymethyl methacrylate when it is made into a homopolymer, and methyl methacrylate (JP-A-4-76013) Publication), a method of copolymerizing methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, methyl methacrylate, N-substituted maleimide, benzyl methacrylate, etc. 8-199901) has been proposed.

[0007]

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.

[0008] The above-mentioned methods include combinations thereof, in which 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.

Further, 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) can be 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, in the former case, the mixing ratio required to cancel the orientation birefringence is MMA / 3FMA = 50 /
50 (wt% / wt%), in the latter case MMA / BZM
A = 80/20 (wt% / wt%). For this reason,
The resulting material cannot have the same properties as PMMA, and is inferior to PMMA in heat resistance and transparency.

On the other hand, in the above method, materials satisfying various characteristics for optical elements can be obtained in terms of characteristics such as heat resistance and transparency, which are problems in the above method. However, a mini disk pickup lens or DV
When molding an optical element used for a pickup lens for D which requires high precision, since mold transferability is required, the mold temperature becomes considerably high, and the resin obtained by this method is used. In this case, some releasability is recognized but not sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an optical resin composition having excellent non-birefringence, heat resistance, low hygroscopicity and mold releasability, and a non-birefringent composition using the same. An object of the present invention is to provide an optical element which is excellent in refraction, heat resistance and low hygroscopicity and has few mold release defects.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in an ester portion, 5 to 40 parts by weight, and 50 to 80 parts by weight of methyl methacrylate. Parts, 5 to 40 parts by weight of N-substituted maleimide, 0 to 3 benzyl methacrylate
0 parts by weight and 0 to 10 parts by weight of monomers copolymerizable therewith, with the total weight being 100 parts by weight, such that the absolute value of the orientation birefringence of the obtained resin is less than 1 × 10 ^−6. Fatty acid amide or fatty acid ester having an endothermic peak temperature of 70 ° C. or higher in a differential scanning calorimeter obtained by copolymerization at a composition ratio of 0.05 to
The present invention relates to a non-birefringent optical resin composition containing 2.0% by weight.

The present invention also relates to an optical element using the non-birefringent optical resin composition.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion used in the present invention include:
Cyclopentyl acrylate, cyclohexyl acrylate, 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 ] deca-8-
Yl, tricyclo [5.2.1.0 ^2,6 ] deca-4-methyl acrylate, cyclodecyl acrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, trimethylcyclohexyl methacrylate, norbornyl methacrylate, methacryl Norbornylmethyl acrylate, cyanonorbornyl methacrylate, phenylnorbornyl methacrylate, isobornyl methacrylate, bornyl methacrylate, menthyl methacrylate, fentyl methacrylate, adamantyl methacrylate, dimethyl adamantyl methacrylate, tricyclo [5 methacrylate 2.2.1.0 ^2,6 ] deca-8-
Yl, tricyclomethacrylate [5.2.1.0 ^2,6 ]
Deca-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, tricyclo [5.2.1.0 ^2,6 ] deca-8-yl, tricyclo [5.2.1.0 ^2,6 ] methacrylate Deca-4-methyl,
Preference is given to cyclodecyl methacrylate and the like. Furthermore, 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. ]
Deca-8-yl and tricyclomethacrylate [5.2.
1.0 ^2,6 ] dec-4-methyl.

The N-substituted maleimide includes, for example, N-methylmaleimide, N-ethylmaleimide,
-Propylmaleimide, Ni-propylmaleimide,
N-butylmaleimide, Ni-butylmaleimide, N
-T-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, etc. N-methylmaleimide, N-ethylmaleimide, N-propyl are preferable in terms of non-birefringence and heat resistance. Maleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide, N-laurylmaleimide and N-phenylmaleimide.

The copolymerizable monomer is not particularly limited as long as it does not impair the transparency, non-birefringence, heat resistance and low hygroscopicity of the polymer. Examples include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, i-acrylate
-Butyl, t-butyl acrylate, pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, octadecyl acrylate, butoxyethyl acrylate, phenyl acrylate, acrylic acid Benzyl, naphthyl acrylate, glycidyl acrylate, 2-acrylate
Acrylic esters such as hydroxyethyl, ethyl methacrylate, propyl methacrylate, n-methacrylic acid
Butyl, i-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-methacrylic acid
Methacrylates such as octyl, dodecyl methacrylate, octadecyl methacrylate, butoxyethyl methacrylate, phenyl methacrylate, naphthyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, α-methylstyrene, α-ethylstyrene , Α-fluorostyrene, α-chlorostyrene, α
-Aromatic vinyl compounds such as bromostyrene, fluorostyrene, chlorostyrene, bromostyrene, methylstyrene, methoxystyrene, etc., acrylamide, methacrylamide, N-dimethylacrylamide, N-diethylacrylamide, N-dimethylmethacrylamide, N-
(Meth) acrylamides such as diethyl methacrylamide, calcium acrylate, barium acrylate, lead acrylate, tin acrylate, zinc acrylate, calcium methacrylate, barium methacrylate, lead methacrylate, tin methacrylate, zinc methacrylate (Meth) acrylic acid metal salts, unsaturated fatty acids such as acrylic acid and methacrylic acid, and vinyl cyanide compounds such as acrylonitrile and methacrylonitrile. One or more of these may be used.

In the present invention, fatty acid amides or fatty acid esters having an endothermic peak temperature of 70 ° C. or more in a differential scanning calorimeter are used. This is because the effect cannot be obtained and a mold release failure occurs. Examples of the fatty acid amide having an endothermic peak temperature of 70 ° C. or more in a differential scanning calorimeter used in the present invention include palmitic amide, stearic amide, behenic amide, oleic amide, and erucic amide. Among these, fatty acid amides having 18 or more carbon atoms are preferable in terms of transparency and mold release properties, and stearamide and behenic acid amide are particularly preferable. One or more of these may be used.

The fatty acid ester having an endothermic peak temperature of 70 ° C. or higher in a differential scanning calorimeter used in the present invention includes:
Fatty acid monoglycerides such as stearic acid and behenic acid, ester compounds of pentaerythritol with fatty acids such as stearic acid and behenic acid, and castor hardened oil. Among these, fatty acid glycerin esters are preferable in terms of transparency and mold release properties, and monoglyceride stearate and hardened castor oil are more preferable. One or more of these may be used.

In the present invention, 5 to 40 parts by weight of a methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, 50 to 80 parts by weight of methyl methacrylate, N-substituted Maleimide 5
-40 parts by weight, 0-30 parts by weight of benzyl methacrylate, and 0-10 parts by weight of a monomer copolymerizable therewith, and are copolymerized as a monomer mixture having a total weight of 100 parts by weight.

The amount of the methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion is 5 to 40 parts by weight,
40 parts by weight is preferred from the viewpoint of hygroscopicity. If the amount of the alicyclic (meth) acrylate is less than 5 parts by weight, the birefringence tends to be large, and the hygroscopicity tends to be high. If it exceeds 40 parts by weight, the mechanical strength decreases. Occurs.

The amount of methyl methacrylate is 5
It is 0 to 80 parts by weight, preferably 60 to 75 parts by weight. If the blending amount of methyl methacrylate is less than 50 parts by weight, the mechanical strength decreases, and if it exceeds 80 parts by weight,
Problems arise in non-birefringence, heat resistance and low moisture absorption.

Further, the compounding amount of the N-substituted maleimide is
5 to 40 parts by weight, preferably 15 to 30 parts by weight, from the viewpoint of birefringence. If the amount of the N-substituted maleimide is less than 5 parts by weight, birefringence tends to be large and the glass transition temperature tends to be low. If it exceeds 40 parts by weight, the reactivity tends to decrease and the residual monomer tends to increase. The birefringence also increases.

The amount of benzyl methacrylate is as follows:
0 to 30 parts by weight, and 4 to 2 parts in terms of heat resistance and birefringence.
It is preferably 0 parts by weight. If the amount of benzyl methacrylate exceeds 30 parts by weight, the glass transition temperature tends to decrease. The amount of the copolymerizable monomer is from 0 to 10 parts by weight. When the amount exceeds 10 parts by weight, there is a problem in any one or two or more of transparency, non-birefringence, heat resistance and low hygroscopicity, depending on the monomer.

In the present invention, the method of determining the compounding ratio of the monomer which results in the absolute value of the orientation birefringence of the obtained resin being less than 1 × 10 ⁻⁶ is determined by the polymer having the respective compounding ratio obtained by the suspension polymerization. A film having a birefringence of 1 × 10 2 when stretched twice (stretching temperature: 90 ° C.).
^It is performed by a method of searching for a compounding ratio of less than ^-6 .

In the present invention, the amount of the fatty acid amide or fatty acid ester having an endothermic peak temperature of 70 ° C. or higher in a differential scanning calorimeter is 0.05 to 2 parts by weight based on the total weight of the monomers. 0.0% by weight, and preferably 0.1 to 1.0% by weight from the viewpoint of releasability. If it is less than 0.05% by weight, a sufficient releasing effect cannot be obtained, and 2.0% by weight
Exceeding the heat resistance lowers the heat and the excess release agent adheres to the mold surface, resulting in a contaminated molded product.

As the copolymerization method for producing the non-birefringent optical resin composition of 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 conducting the polymerization, a polymerization initiator can be used. Benzoyl peroxide, as a polymerization initiator,
Lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-2-ethylhexanoate, 1,1-t-butylperoxy-
Organic peroxides such as 3,3,5-trimethylcyclohexane, azobisisobutyronitrile, azobis-4-methoxy-2,4-dimethylvaleronitrile, azobiscyclohexanone-1-carbonitrile, azodibenzoyl, etc. Any of those that can be used for ordinary radical polymerization, such as an azo compound, a water-soluble catalyst such as potassium persulfate and ammonium persulfate, and a redox catalyst using a combination of a peroxide or a persulfate and a reducing agent can be used. The polymerization initiator is used in an amount of 0.01 to 1 based on the total amount of the monomers.
It is preferably used in the range of 0% by weight.

Further, as a molecular weight regulator, a mercaptan compound, thioglycol, carbon tetrachloride, α-methylstyrene dimer, or the like can be added as required.

In the case of thermal polymerization, the polymerization temperature is from 0 to 20.
It can be appropriately selected between 0 ° C., and preferably 50 to 120 ° C.

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. As a suspending agent, polyvinyl alcohol, methylcellulose, water-soluble polymers such as polyacrylamide, calcium phosphate,
There are poorly soluble inorganic substances such as magnesium pyrophosphate,
The water-soluble polymer is used in an amount of 0.03 to
It is preferably used in an amount of 1% by weight, and the hardly soluble inorganic substance is preferably used in an amount of 0.05 to 0.5% by weight based on the total amount of the monomers.

As a suspending aid, there is an anionic surfactant such as sodium dodecylbenzenesulfonate. When a sparingly soluble inorganic substance is used as a suspending agent, it is preferable to use a suspending aid. . The suspension aid is preferably used in an amount of 0.001 to 0.02% by weight based on the total weight of the monomers.

The resin contained in the non-birefringent optical resin composition obtained by the present invention is not particularly limited in terms of its molecular weight, but has a weight average molecular weight (in terms of polystyrene) of 10,000 to 1,000,000. Are preferred, and in terms of heat resistance and moldability, 100,000 to 300
A range of 000 is particularly preferred.

The non-birefringent optical resin composition of the present invention comprises:
In its use, prevention of deterioration, thermal stability, moldability,
From the viewpoint of processability and the like, phenol-based, phosphite-based, thioether-based antioxidants, aliphatic alcohols, fatty acid esters other than the compounds described above, phthalic acid esters, triglycerides, fluorine-based surfactants,
Release agents such as metal salts of higher fatty acids, other lubricants, plasticizers,
An antistatic agent, an ultraviolet absorber, a flame retardant, a heavy metal deactivator and the like may be added for use.

In the present invention, the application of the non-birefringent optical resin composition to an optical element includes injection molding, compression molding, micromolding, floating molding, and the like.
Known molding methods such as a low-links method and a casting method can be used. In the casting method, after partially polymerizing, the mixture is poured into a mold and subjected to final polymerization to obtain a molded product and at the same time to produce the non-birefringent optical resin composition according to the present invention. You may.

The surface of the molded article obtained by the above molding method is coated with an inorganic compound such as MgF ₂ or SiO ₂ by vacuum evaporation, sputtering, ion plating or the like. By hard-coating an organic silicon compound such as a silane coupling agent, a vinyl monomer, a melamine resin, an epoxy resin, a fluororesin, a silicone resin, etc., moisture resistance, optical properties, chemical resistance, abrasion resistance, Anti-fog can be improved.

Examples of the optical element in the present invention include a general camera lens and finder, a video camera lens, a laser pickup lens, an fθ lens for a laser printer, a cylindrical lens and an oligomer mirror, a projection TV lens, and a liquid crystal. Multi-lenses for projectors, relay lenses, condenser lenses, projection lenses and Fresnel lenses, lenses such as eyeglass lenses, compact discs (CD, CD
-ROM, etc.), mini discs, DVD disc substrates, LCD substrates, polarizing film transparent resin sheets, retardation films, light diffusion films, liquid crystal element members such as liquid crystal element bonding adhesives, projector screens, optics Examples include a filter, an optical fiber, an optical waveguide, a prism, and a lens for a photoelectric conversion element. The resin composition of the present invention is particularly suitable for optical elements such as pickup lenses for mini disks (objective lenses, diffraction gratings, collimator lenses, etc.) and DVD pickup lenses (objective lenses, diffraction gratings, collimator lenses, etc.). .

[0037]

EXAMPLES The present invention will be described below in detail with reference to examples, but is not intended to limit the scope of the present invention.

The water-soluble polymer (A) (polymethacrylate) used as a suspending agent in the following 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. Is blown to remove air in the system, and then the system is heated to 65 ° C. while stirring in a water bath.
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
360 g of 8-yl, 1200 g of methyl methacrylate, N
-360 g of cyclohexylmaleimide, 80 g of benzyl methacrylate, 8 g of lauroyl peroxide, 4 g of n-octylmercaptan, stearic acid amide (fatty acid amide S manufactured by Kao, endothermic peak temperature: 106 as fatty acid amide)
C) 2 g was dissolved to obtain a monomer mixture.

0.1 g of the above-mentioned jelly-like water-soluble polymer (A) and 2500 g of deionized water were added as suspending agents to a 5-liter autoclave vessel equipped with a stirrer. A sodium dihydrogen phosphate combination buffer was added and stirred, and the pH was adjusted to 7.2 to obtain a suspension medium. The above monomer mixture was added thereto with stirring, and the mixture was stirred at a rotation speed of 270 rpm under a nitrogen atmosphere.
Polymerization was conducted at 3 ° C. for 3 hours and then at 120 ° C. for 1 hour to obtain resin particles (the polymerization rate was 99% by a gravimetric method). The resin particles are washed with water, dehydrated and dried, and the cylinder temperature is 260 using an injection molding machine IS-50EP manufactured by Toshiba Machine Co., Ltd.
° C., injection speed 60cm ³ / sec, and a mold temperature of 110 ° C., to obtain a plurality of specimens for property evaluation.

Examples 2 to 4 and Comparative Examples 1 to 7 Test pieces for characteristic evaluation were prepared in the same manner as in Example 1 using monomers, fatty acid amides or fatty acid esters having the composition ratios shown in Table 1.

For the resin particles and test pieces obtained in Examples 1 to 4 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),
The state of the striae was examined and shown in Table 1. The evaluation was performed by the following method. (1) Compound Birefringence 1 g of resin particles having each compounding 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
Film was made. Next, this film was stretched twice (stretching temperature: 90 ° C.), and the orientation birefringence was measured. (2) Birefringence of molded product The test specimen of 50 × 40 × 3 (mm) obtained above was
The phase difference (single pass) was measured at the measurement points shown in FIG. 1 using an ellipsometer (AEP-100 manufactured by Shimadzu Corporation) using a He-Ne laser, and the birefringence per thickness was calculated based on the following equation.

[0044]

(Equation 1)

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

[0046]

(Equation 2)

(4) Glass Transition Temperature (Tg) The glass transition temperature (Tg) of the resin particles obtained above was measured with a differential scanning calorimeter (Rigaku ThermoPlus DSC8230). (5) Release Property Using the resin particles obtained above, an injection molding machine IS-50EP manufactured by Toshiba Machine Co., Ltd. was used to obtain a cylinder temperature of 260.
° C, injection speed 60cm ³ / sec, mold temperature 110 ° C
Then, using a test piece 100 times continuously (50 mm x 40 mm x
3 mm), and the occurrence rate of the number of mold release defects (resin adhesion to the mold surface, cracks on the molded product surface, etc.) at this time was determined.

In the following, 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,
SAM is stearic acid amide (Kao fatty acid amide S
Endothermic peak temperature: 106 ° C), OHG is castor-hardened oil (Dainichi Chemical Daiwax OHG, Endothermic peak temperature: 8)
8 ° C.). Table 1 shows the evaluation results.

[0049]

[Table 1]

[0050]

According to the present invention, there is provided an optical resin composition having excellent non-birefringence, heat resistance, low hygroscopicity and mold releasability. Using this resin, non-birefringence, heat resistance, An optical element having excellent low hygroscopicity is provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a method for measuring birefringence of a molded article.

[Explanation of symbols]

 1 gate 2 measurement point

Continued on the front page F-term (reference) 4J002 BG061 BH021 EH046 EP016 GP01 4J100 AB03S AB07S AB08S AB09S AB10S AK13S AL03P AL03S AL08Q AL08S AL09S AL11S AM02S AM15S AM17S AM45R AM47R AM48R AM49R BA05Q BA05R BC04 BC03 BC04 BC03 DA63 JA33 JA35 JA36

Claims (5)

[Claims] 1. A methacrylate or acrylate having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in an ester portion, 5 to 40 parts by weight, and methyl methacrylate 50.
To 80 parts by weight, 5 to 40 parts by weight of an N-substituted maleimide, 0 to 30 parts by weight of benzyl methacrylate and 0 to 10 parts by weight of a monomer copolymerizable therewith, with the total weight being 100 parts by weight. The absolute value of the orientation birefringence of the resin to be obtained is 1 × 1
A fatty acid amide or a fatty acid ester having an endothermic peak temperature of 70 ° C. or higher in a differential scanning calorimeter is obtained by copolymerization at a composition ratio of less than 0 ^{-6 based on} the total weight of the monomer. A non-birefringent optical resin composition containing 0.05 to 2.0% by weight. 2. An endothermic peak temperature of a differential scanning calorimeter of 7
Fatty acid amide or fatty acid ester having a temperature of 0 ° C. or higher,
2. A compound comprising at least one compound of a fatty acid amide and a fatty acid glycerin ester having 18 or more carbon atoms.
The non-birefringent optical resin composition according to the above. 3. A methacrylic acid ester or an acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in an ester moiety, wherein cyclohexyl methacrylate, isobornyl methacrylate, norbornyl methacrylate, norbornylmethyl methacrylate, methacrylic acid tricyclo [5.2.1.0 ^{2, 6]} dec-8-yl and methacrylic acid tricyclo [5.2.1.0 ^{2, 6]} at least one selected from the group consisting of deca-4-methyl The non-birefringent optical resin composition according to claim 1, which is the above compound. 4. The N-substituted maleimide is N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide. The non-birefringent optical resin composition according to claim 1, which is at least one compound selected from the group consisting of N-cyclohexylmaleimide, N-laurylmaleimide and N-phenylmaleimide. 5. An optical element using the non-birefringent optical resin composition according to claim 1, 2, 3, 4, or 5.