JPS59120607A - Transparent plastic - Google Patents

Abstract

PURPOSE:A transparent plastic excellent in machinability, etc., and suitable for optical use, comprising a crosslinking polyfunctional monomer, a linear polymer- forming monomer containing ethylene glycol dimethacrylate and an allyl group- containing monomer. CONSTITUTION:A composition is used which consists mainly of a multi-component monomer mixture obtained by adding up to 30wt%, based on the reaction system, ethylene glycol dimethacrylate as a crosslinking polyfunctional monomer to a monomer which, when homopolymerized, forms a linear polymer and a monomer containing an allyl group in the molecular structure. Examples of the linear polymer-forming monomers used include vinyl chloride, acrylonitrile, methyl methacrylate, and styrene. Examples of the monomers containing an allyl group in the molecular structure include allyl methacrylate, diethylene glycol bisallyl carbonate, and triallyl isocyanurate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to transparent plastics, and particularly to transparent plastics suitable for optical applications.

Conventionally, hard transparent resins used for various optical applications include polymethyl methacrylate, polycarbonate, polystyrene, acrylonitrile-styrene copolymer resin, polymethylpentene, copolymer resin of methyl methacrylate and styrene monomer, There were styrene-butadiene copolymer resins, etc. These transparent resins are polymers with a linear molecular structure. Therefore, optical molded products are generally made by injection molding or extrusion molding. However, since it is a linear polymer, it has some practical problems in terms of chemical resistance, solvent resistance, heat resistance, dimensional stability, etc. in the case of optical applications where the usage environment is harsh. .

In particular, these transparent resin molded products have low surface hardness and are easily damaged, which not only impairs the beauty of the product, but also significantly reduces optical properties, as well as stabilizes optical properties such as refractive index and dispersion. However, it also had drawbacks such as being unsuitable for processing such as cutting and polishing.

Various methods have been proposed in the past in order to improve the fragility of the surface of the above-mentioned plastic lenses, which are molded products of transparent resin.

For example, a method of forming a thin film of an inorganic oxide mainly containing SiO2 on the surface of a plastic lens by vacuum evaporation, sputter linking, ion plating, etc. As a coating material for plastic lenses, there are known methods in which it is applied to the surface by coating, spraying, or dipping, and then hardened by heating or irradiation with ultraviolet rays or electron beams to form a coating with high hardness on the surface of the plastic lens. was. However, although the plastic lenses manufactured by these methods have improved surface hardness, the (thermal)
The thin film is difficult to follow deformation, resulting in insufficient heat resistance and impact resistance, and poor adhesion between the film and the plastic lens base material, making it easy for cracks to form at the interface and peeling off of the film. This tendency is remarkable under high temperature and high humidity conditions, and in order to form a uniform film, it is difficult to adjust the viscosity of the coating material and control the coating processing conditions, which can lead to increased costs and deterioration of productivity. It had disadvantages such as inviting people.

Furthermore, there have been significant advances in the processing accuracy of machine tools in recent years, and people are beginning to consider using these ultra-precision processing machines to make plastic aspheric lenses. Generally, glass is hard and brittle, so it is extremely difficult to process glass into aspherical lenses or prisms using such machine tools. On the other hand, plastics are more suitable for machining than glass, but in the case of linear polymers such as the various transparent resins mentioned above, they tend to stick or fuse during machining, or due to the heat generated. There was a drawback that it caused the phenomenon of deformation.

In addition to the various resins mentioned above, diethylene glycol bisallyl carbonate is used as an optical transparent resin under the trade name CR-
It is known as 39. This CR-39 has a three-dimensional three-dimensional network structure, so it has much better chemical resistance, solvent resistance, heat resistance, machinability, etc. than the various transparent resins mentioned above. It has good transparency and also good adhesion to antireflection coating materials. However, since CR-39 is a thermosetting resin,
It is obtained by bulk polymerization by casting the molded product,
Since the volumetric shrinkage during polymerization is large (about 14% shrinkage) and the reactivity of the monomer is low, it takes a long time to obtain the polymer. Furthermore, CR-39 tends to cause internal strains such as birefringence, and when internal strains occur, it becomes brittle, so bulk polymerization to obtain large molded products is not suitable. For this reason, it is only used in small molded products such as eyeglass lenses. In the case of eyeglass lenses, polishing after casting,
The cost of CR-39 as a lens is extremely high because it requires anti-reflection coating and cutting into the desired shape, and the monomer is expensive.

For the reasons mentioned above, the development of an excellent optical transparent resin to replace CR-39 is expected.

In addition to excellent transparency, this invention has physical properties that include excellent surface hardness, chemical resistance, water resistance, heat resistance, and machinability, as well as excellent adhesion to antireflection coating materials. The purpose of this project is to provide transparent plastic that can be used as a material for optical equipment lenses such as glasses lenses, telescopes, and cameras.

This invention provides a multi-component mixed monomer in which ethylene glycol dimethacrylate as a crosslinkable polyfunctional monomer is added in an amount of 30% by weight or less of the reaction system to at least one monomer that forms a linear polymer when used as a single polymer; It is a transparent plastic made by curing a composition whose main component is a monomer with an allyl group in its molecular structure.

In this invention, linear polymers, that is, thermoplastic resins, have the advantage that they can be produced in large quantities with the same shape at low cost by injection molding or extrusion molding, but have the disadvantage of being resistant as described above. There are problems with physical properties such as chemical resistance, solvent resistance, heat resistance, machinability, etc. In particular, there is a drawback of poor adhesion with the coating that is formed on the surface to improve the ease of scratching. We thought that there may be a limit to the improvement of linear polymers in terms of improving optical properties such as dispersion and dispersion. In this respect, we thought that crosslinked resins obtained by cast polymerization might be superior in various aspects.

For example, cross-linked polymers are easier to produce in small-scale production quantities with different refractive indexes, and cross-linked polymers have better heat resistance, so they can be used in harsh working environments such as vacuum evaporation and ion plating. It is also suitable for

Typical examples of monomers constituting linear polymers studied in this invention are shown in the following table.

Monomer Chemical formula Vinyl acetate CH3COOCHCH2 Vinyl chloride CH2CHCl Vinylidene chloride
CH2CCl2 Acrylonitrile CH2CHC
N-methyl methacrylate CH2=CCH3COOCH
3ethyl methacrylate CH2=CCH3COOC2
H5 Methyl acrylate CH2=CHCOOCH3
Ethyl acrylate CH2=CHCOOC2H5 Styrene α-methylstyrene monomer Chemical formula methacrylic acid CH2=CCH3COOHEthyl crotonate CH3CH=CHCOOC2H5 Polymers obtained from these monomers contain additives contained in the raw materials, such as polymerization inhibitors and ultraviolet absorbers. Except for the influence of trace amounts of mixed components and the influence of the polymerization initiator used, it is generally colorless, transparent, and hard. The monomers constituting the linear polymer in this invention may be a combination of one or more monomers listed in the preceding table.

The monofunctional monomers shown in the previous table are used alone or in combination, and ethylene glycol dimethacrylate is added as a crosslinkable polyfunctional monomer to the total monomers of the reaction system in an amount of 30% by weight or less, preferably 10% by weight or more and 30% by weight. The polymer obtained by polymerizing the multi-component mixed monomer added below has excellent heat resistance, surface hardness, machinability, etc.

Furthermore, in this multi-component mixed monomer, a monomer having an allyl group in its molecular structure, such as allyl methacrylate,
By adding diethylene glycol bisallyl carbonate, diallyl phthalate, its isomers, triallyl isocyanurate, etc. to the entire reaction system in an amount of several percent by weight, preferably 3 to 7 percent by weight, excellent adhesion to the optical antireflection coating material can be achieved. A polymer is obtained.

In the case of this reaction system, when the proportion of monomers with allyl groups in its molecular structure increases (10% by weight or more), the resulting polymer has poor heat resistance and tends to be colored yellow, although this varies depending on the type of initiator. However, it is difficult to obtain a good colorless, transparent, hard polymer.

The monomer having an allyl group in its molecular structure is not particularly limited, and any monomer may be used.

The polymerization procedure of this invention is to first add a predetermined amount of initiator to the above-mentioned mixed monomer system, perform prepolymerization, vacuum degas the syrup obtained by prepolymerization, and then place it in a glass cell, etc. The main polymerization is carried out in a hot air circulation furnace or hot water bath with the cell sandwiched between clamps.

Prepolymerization is carried out as follows. A predetermined amount of polymerization initiator is added to a predetermined mixed monomer while stirring. Once the initiator is sufficiently dissolved in the monomer, the temperature of the monomer is gradually raised while stirring is continued.

Once the temperature exceeds 60°C, the rate of temperature increase is slowed down and kept constant around 80°C. At a certain point in the reaction, gelation may suddenly occur and crosslinking polymerization may progress and become uncontrollable, so the reaction is stopped just before gelation occurs.

By this operation, most of the reaction heat is generated and volumetric shrinkage can proceed to some extent at this stage, so that shrinkage within the glass cell during main polymerization can be reduced. To prevent gelation, please refer to Japanese Patent Application No. 183750/1983, ``Method for manufacturing transparent plastics with increased prepolymerization rate.''
As shown in , it is safe to add a few percent of α-methylstyrene dimer to the monomer mixture. To stop the prepolymerization reaction, heating is stopped and the temperature of the monomer is immediately lowered by cooling while slowly continuing stirring.

Cooling is performed to at least 10°C or lower.

Thereafter, this monomer is vacuum degassed to remove gas components contained therein, and is injected into a cell such as a glass mold with a gasket surrounding the monomer to carry out main polymerization. As mentioned above, the main polymerization is carried out in a hot air circulation furnace or a hot water bath, and finally, curing is carried out at a high temperature. After curing, the cell is cooled and the polymer inside is removed from the gasket. The main polymerization is
Preheating at a low temperature, main polymerization at a higher temperature,
This is followed by high-temperature curing, which is usually done in three stages.

This invention will be explained below with reference to Examples.

Example 1 0.1 g of t-butylperoxy 2-ethylhexanoate was added to a mixed monomer system of 69 g of methyl methacrylate, 20 g of ethylene glycol dimethacrylate, 5 g of allyl methacrylate, and 6 g of α-methylstyrene dimer. was added, preliminarily loaded, and vacuum degassed, and then injected into two glass plates via a vinyl chloride hollow gasket. After holding this glass cell assembly with a clamp, the temperature was raised from 60°C to 115°C over 10 hours, and then curing was performed at 115°C for 4 hours.

The refractive index of the polymer thus obtained is No=1.
50, and the light transmittance was 92%. The surface hardness was 4H on a pencil hardness scale, and the solvent resistance, heat resistance, and cutting and polishing properties were also excellent.

Example 2 To a mixed monomer system of 69 g of methyl methacrylate, 20 g of ethylene glycol dimethacrylate, 5 g of diallyl terephthalate, and 6 g of α-methylstyrene dimer, 0.1 g of t-butyl peroquine 2-ethylhexanoate was added. , and polymerized in the same manner as in Example 1.

The obtained polymer had a refractive index No. of 1.50 and a light transmittance of 90%. The surface hardness was 3H on a pencil hardness scale, and it had excellent solvent resistance, heat resistance, and cutting and polishing properties.

Example 3 To a mixed monomer system of 69 g of methyl methacrylate, 20 g of ethylene glycol dimethacrylate, 5 g of diethylene glycol bisallyl carbonate, and 6 g of α-methylstyrene dimer, 0.0 g of t-butylperoxy 2-ethylhexanoate was added. 1 g was added, and polymerization was carried out in the same manner as in Example 1.

The obtained polymer had a refractive index No. of 1.50 and a light transmittance of 90%. The surface hardness was 3H on a pencil hardness scale, and it had excellent solvent resistance, heat resistance, and cutting and polishing properties.

An anti-reflection coating was applied to the polymer obtained in the above example by vacuum deposition, and a comparative test of adhesion was carried out with a similar coating of CR-39 and methyl methacrylate cast plates by vacuum deposition. saw.

The test method is a temperature of -23℃ to 42℃ and a humidity of 15% to
Each coated sample was placed in an environment that changed by up to 90%, and the adhesion of the coating film was examined under environmental changes (temperature and humidity changes).

As a result of the test, when the casting plate of methyl methacrylate was coated by vacuum evaporation, there were countless minute cracks in the coating film after the test, indicating that the adhesion of the coating film was not good. When the polymer of the present invention was coated by vacuum deposition, the coating film did not exhibit the above-mentioned phenomenon even after the test, and it was found that the coating film had good adhesion.

As explained above, the present invention is a monopolymer in which ethylene glycol dimethacrylate is added as a crosslinking polyfunctional monomer to at least one monomer forming a linear polymer in an amount of 30% by weight or less of the reaction system. It is a transparent plastic made by curing a composition whose main components are a mixed monomer and a monomer with an allyl group in its molecular structure, so it is transparent, hard, and has good heat resistance and machinability. It also has excellent solvent resistance, making it possible to make highly accurate aspherical lenses and prisms using ultra-precision NC lathes and ultra-precision NC jig grinders.It also has excellent solvent resistance, making it particularly suitable for anti-reflection coatings. Excellent adhesion.

In addition, the transparent plastic of the present invention is useful as a material for optical lenses for glasses, telescopes, cameras, and the like.

Agent Patent Attorney Shoji Watanabe Procedural Abstracts (a July 1958 OLl Director-General of the Special Preparation Agency Wakasugi 411-nin 1 ! 11 Indication 1982 ! 1 Temple License Request No. 226937 3 Person making the amendment Relationship between thing H7 l 1 ('1 exit, ; Sadato f', :g
' 1 Ru I 2 Hatariiya, Shibuya-ku, Tokyo - Eye 4; 3 No. 2 Scene Mr. I; (1/N) (037) Olympus Optical Co., Ltd. Representative Kita + J Shigeru Man 4 227 〒227 'Yamajuku
045-971. -1370 Address Kanagawa Prefecture fp'
ii Private IJ Midori-ku〒t]ri 11'', Town 11 (i 5 back area 206 Supplement 1L Invention number 0 supplement contents (1) Specification dose 1: 3 page 19 line 1-23℃ ~42℃"
Revised 1 [2.

(2) Details 714゛Page 13, Line 20, Section 115~90φ
"+r l oφ ~ 95 section" and 1. J city.

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Claims (1)

[Claims] 1. In the case of a single polymer, a multicomponent mixed monomer in which ethylene glycol dimethacrylate as a crosslinkable polyfunctional monomer is added in an amount of 30% by weight or less of the reaction system to at least one monomer forming a linear polymer, and a molecular structure A transparent plastic made by curing a composition whose main components are a monomer with an allyl group.