JPH0527101A - Plastic cleanse - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a plastic lens having low birefringence, excellent transparency, moldability, and dimensional stability (surface accuracy). [Structure] 90 to 10% by weight of a polycarbonate resin having a specific viscosity of 0.451 to 1.176 made of a specific dihydric phenol [eg: bis (4-hydroxy-3,5-dimethylphenyl) propane], and a copolymer. A plastic lens comprising a mixture of 10 to 90% by weight of an acrylonitrile-styrene copolymer having an acrylonitrile content of 5 to 15% by weight and a weight average molecular weight of 30,000 to 600,000 based on the weight of.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has low birefringence, transparency,
The present invention relates to a plastic lens excellent in molding processability and dimensional stability (surface accuracy), and particularly to a plastic lens suitable for an optical pickup objective lens related to optoelectronics, a laser beam printer lens, and the like.

[0002]

2. Description of the Related Art Conventionally, polymethylmethacrylate resin has been used as a plastic lens. However, the polymethylmethacrylate resin has a drawback that it has poor dimensional stability (surface accuracy) because of its high water absorption. On the other hand, polycarbonate resins are used as optical materials because of their low water absorption, high transparency and high dimensional stability. However, the polycarbonate resin has a drawback that molding distortion is likely to occur due to its large birefringence and high melt viscosity.

As a method for improving the birefringence of a polycarbonate resin, JP-A-61-108617 discloses a method of mixing a styrene resin, and JP-A-61-19630.
Japanese Patent Laid-Open No. 63-15822 and Japanese Patent Laid-Open No. 63-15822 propose a method of graft copolymerizing with a styrene resin.

However, in the method of mixing a styrene resin, since the resulting mixture causes phase separation, light is scattered and light transmission is hindered, so that it is not used as a plastic lens using laser light. .. Further, a graft copolymer of a polycarbonate resin and a styrenic resin has low mechanical strength and is extremely brittle, and it is necessary to increase the molecular weight in order to increase the mechanical strength. It deteriorates, and a practical lens cannot be obtained.

On the other hand, tetramethylbisphenol A polycarbonate resin and acrylonitrile content of 2-1
It is reported that a mixture with 3% by weight of a styrene-acrylonitrile copolymer is single-phase and transparent [A. Fernandez, I. W. Barlow and Du R. Paul, Polymer 27, 1788-]. 98 pages (1986), (AC Fernandes, IW Barlow and DRPa
ul, Polymer, 27 , 1788-98 (1986)], and it is also known to reduce the birefringence of polymers by adding polymers with opposite birefringence [J.
Henich, April 14-15, 1986, Lecture at the Conference on New Polymers in Bad Nauheim "Polymer as a Substrate for Optical Disk Recording Devices"]. Further, in JP-A-63-306092, a mixture of the above-mentioned tetramethylbisphenol A polycarbonate resin and a styrene-acrylonitrile copolymer has optical data because of its high rigidity, low birefringence and especially optical uniformity. Proposed to be an excellent substrate for recording devices. However, this publication discloses only the characteristics as an optical data recording device that it is optically uniform, has a low birefringence, and has a high elastic modulus. Regarding the use of such a mixture in a lens, nothing is said. There is no description or suggestion.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plastic lens having low birefringence and excellent transparency, moldability and dimensional stability (surface accuracy).

As a result of earnest studies aimed at achieving the above object, the present inventor has injection-molded a mixture of tetramethylbisphenol A polycarbonate resin having a specific molecular weight and acrylonitrile-styrene copolymer obtained by copolymerizing acrylonitrile at a specific ratio. Then, transparency, low birefringence,
It was clarified that a lens excellent in moldability, dimensional stability (surface accuracy), etc. was obtained, and the present invention was completed based on this finding.

[0008]

The present invention provides the following general formula [1].

[0009]

[Chemical 2] [In the formula, X is an alkylidene group having 2 to 6 carbon atoms, and 5 carbon atoms.
6 cycloalkylidene group, -S- or -SO ₂ - is. ] The specific viscosity of the repeating unit represented by 0.4
90 to 10% by weight of a polycarbonate resin of 51 to 1.176, an acrylonitrile content of 5 to 15% by weight and a weight average molecular weight of 3 based on the weight of the copolymer.
The present invention relates to a plastic lens composed of a mixture of 10,000 to 600,000 acrylonitrile-styrene copolymer and 10 to 90% by weight.

A preferred specific example of the dihydric phenol compound constituting the repeating unit represented by the general formula [1] is bis (4-hydroxy-3,5-dimethylphenyl).
Propane, bis (4-hydroxy-3,5-dimethylphenyl) methane, bis (4-hydroxy-3,5-dimethylphenyl) sulfide, bis (4-hydroxy-)
Examples thereof include 3,5-dimethylphenyl) sulfone and bis (4-hydroxy-3,5-dimethylphenyl) sulfoxide, which may be used alone or in combination of two or more kinds. Further, other dihydric phenol compounds may be used in combination as long as the amount is small.

To produce a polycarbonate resin from such a dihydric phenol compound, usually, the dihydric phenol compound and the molecular weight modifier are dissolved in an alkaline aqueous solution and reacted with phosgene in the presence of an organic solvent inert to the reaction. An interfacial polymerization method of polymerizing in the presence of a catalyst, or a pyridine method of directly dissolving the dihydric phenol compound and the molecular weight modifier in pyridine or a mixed solution of pyridine and an inert solvent and reacting with phosgene to obtain a polycarbonate resin. Adopted.

Examples of the molecular weight regulator used here include phenols such as phenol, alkylphenol, p-tert-butylphenol, p-cumylphenol, p-isooctylphenol and 2,6-dimethylphenol, benzoyl chloride, p. Examples thereof include carboxylic acid chlorides such as -tert-butylbenyl chloride and phenyl chloroformates. As the organic solvent inert to the reaction, chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, monochlorobenzene and dichlorobenzene can be used. Examples of the polymerization catalyst include tertiary amines such as trimethylamine, triethylamine, tributylamine, tripropylamine, tridecylamine and pyridine, trimethylbenzylammonium chloride, tetramethylammonium chloride, triethylbenzylammonium chloride, ammonium hydroxide and the like. Examples include quaternary ammonium salts.

The molecular weight of the polycarbonate resin used in the present invention is 0.451 to 1.176 expressed as a specific viscosity.
And the range of 0.727 to 0.977 is particularly preferable. When a polycarbonate resin whose specific viscosity does not reach the above range is used, the strength of the obtained mixture is low and the mixture is apt to crack during molding. When a polycarbonate resin having a specific viscosity higher than the above range is used, the fluidity and moldability of the resulting mixture are poor and the molded product is apt to be distorted. The specific viscosity of the polycarbonate resin was measured by dissolving it in methylene chloride at a concentration of 0.7 g / dl and at a temperature of 20 ° C.

The acrylonitrile-styrene copolymer used in the present invention may be one produced by any method such as solventless polymerization, solution polymerization, suspension polymerization and emulsion polymerization. It is necessary that the amount be within the range of 5 to 15% by weight. If the amount of acrylonitrile is outside the above range, the compatibility with the polycarbonate resin will be poor and a transparent mixture cannot be obtained.

If the molecular weight of the styrene-acrylonitrile copolymer is too low, the mechanical strength of the resulting mixture will be low, and no good molded article will be obtained. If the molecular weight of the styrene-acrylonitrile copolymer is too high, the fluidity and moldability of the resulting mixture will be poor, resulting in poor molding. Since the product is likely to be distorted, a product having a weight average molecular weight in the range of 30,000 to 600,000 is used.
The range of 0 to 250,000 is preferable, and the range of 80,000 to 200,000 is particularly preferable from the viewpoint of mechanical strength and fluidity. This weight average molecular weight is T
It was measured by a gel permeation chromatography method in terms of polystyrene using a packed column of SK-GEL H type [manufactured by Tosoh Corporation] and tetrahydrofuran as an eluent.

The mixing ratio of the polycarbonate resin and the styrene-acrylonitrile copolymer is 10 to 90% by weight, preferably 30 to 70% by weight, based on the total weight of both. When the polycarbonate resin does not reach the above range, the mechanical strength of the obtained mixture is insufficient, and when it exceeds the above range, a sufficient birefringence canceling effect cannot be obtained.

The above-mentioned mixture of the polycarbonate resin and the styrene-acrylonitrile copolymer is molded into a lens by injection molding, compression molding, vacuum molding, or any other means, but the injection molding method is preferable in terms of mass productivity. Most preferred. Injection molding conditions include molding temperature 270-320
C, mold temperature 100-150 C, holding pressure 700-1200
kg / cm ² is preferred. The precision of the molded lens is represented by its dimensional precision and surface characteristics, and if these precisions are poor, the optical distortion will be large, but by using the mixture of the present invention, the optical distortion is small under the above conditions. Excellent plastic lenses are easily obtained.

In addition, an antioxidant, a light stabilizer, a colorant, a release agent, an antistatic agent and the like may be appropriately added to the mixture in the present invention depending on the molding method and the like.

[0019]

EXAMPLES The present invention will be further described with reference to the following examples. Parts in the examples are parts by weight and% are% by weight. The weight average molecular weight in the examples is 15 mg for pellets.
Is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography after dissolving in 5 ml of tetrahydrofuran. Flow value (Q value) is 1m at a temperature of 280 ° C and a load of 100kg / cm ^{2 using a} flow tester.
Amount of molten resin (cm ³
/ Sec). The moldability was judged by the ease of molding when injection-molding a lens for measuring optical strain, and was indicated by ◯ when it was good and by x when it was difficult. Optical distortion is measured using a lens mold at a resin temperature of 280 ° C, a mold temperature of 145 ° C, and a holding pressure of 800.
77 mm diameter by injection molding machine (Netstal) at Kg / cm ² .
A lens having a thickness of 15 mm was molded and visually judged by a photoelastic photograph. No distortion was indicated by ◯, and large distortion was indicated by x. The photoelastic constant is 120mm x 120mm x 1.2mm
It was measured by Riken photoelastic PA-150 type manufactured by Riken Keiki Co., Ltd. The light transmittance was 150 mm × 150 mm × 2.5 mm, a test piece was injection-molded, and the transmittance (%) at a wavelength of 632.8 nm was measured by Hitachi U-3400 type spectrophotometer manufactured by Hitachi, Ltd. The refractive index was measured using an Abbe refractometer.

[0020]

Example 1 40 parts of tetramethylbisphenol A polycarbonate having a specific viscosity of 0.800 and 60 parts of a styrene-acrylonitrile copolymer having a weight average molecular weight of 100,000 obtained by copolymerizing 10% of acrylonitrile were dry-blended with a tumbler and provided with a vent. Pellets were obtained by extruding with a 30 mm diameter extruder at a temperature of 260 to 280 ° C. The weight average molecular weight, flow value and other evaluation results of this pellet are shown in Table 1.

[0021]

Example 2 Using 60 parts of tetramethylbisphenol A polycarbonate having a specific viscosity of 0.660, styrene-
Example 1 was repeated except that the amount of the acrylonitrile copolymer used was 40 parts. Table 1 shows the weight average molecular weight, flow value and other evaluation results of the obtained pellets.

[0022]

[Comparative Example 1] Bisphenol A in a stainless steel reaction tank
5870 parts of a methylene chloride solution containing 856.4 parts of chloroformate, 4656 parts of an alkaline aqueous solution containing 570.9 parts of bisphenol A, and a 48% alkaline aqueous solution 35
3.2 parts, p-tert-butylphenol 11.4 parts and O
Weight average molecular weight 95,000 including H value 4.6 (meq / g)
874.8 parts of modified polystyrene of (1) was added, 2.6 parts of triethylamine was added, and the mixture was reacted at 33 to 35 ° C. for about 1 hour, washed with water, and powdered with a granulator. The specific viscosity of this polycarbonate-polystyrene graft copolymer powder was 0.480. The obtained powder was pelletized in the same manner as in Example 1, and the weight average molecular weight, flow value and other evaluation results of this pellet are shown in Table 1.

[0023]

[Comparative Example 2] Bisphenol A polycarbonate having a specific viscosity of 0.283 [Panlite AD-55 manufactured by Teijin Chemicals Ltd.]
03] The powder was pelletized in the same manner as in Example 1,
The weight average molecular weight, flow value and other evaluation results of this pellet are shown in Table 1.

[0024]

[Table 1]

[0025]

According to the present invention, it is possible to easily provide a plastic lens excellent in transparency, low birefringence, moldability, dimensional stability (surface accuracy), etc. Effects are exceptional.

Claims (1)

What is claimed is: 1. The following general formula [1] [In the formula, X is an alkylidene group having 2 to 6 carbon atoms, and 5 carbon atoms.
6 cycloalkylidene group, -S- or -SO ₂ - is. ] The specific viscosity of the repeating unit represented by 0.4
90 to 10 wt% of a polycarbonate resin of 51 to 1.176, an acrylonitrile content of 5 to 15 wt% and a weight average molecular weight of 30, based on the weight of the copolymer.
A plastic lens consisting of a mixture of 000 to 600,000 with 10 to 90% by weight of an acrylonitrile-styrene copolymer.