JPH039926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a synthetic resin for lenses having a large refractive index and small aberrations. Various studies have been conducted on synthetic resins for lenses that can replace inorganic glass. Examples of these include polydiethylene diglycol bisallyl carbonate (hereinafter abbreviated as CR-39), polymethyl methacrylate, polycarbonate, polystyrene, and the like. However, while CR-39 and polymethyl methacrylate have the advantage of being lightweight and impact resistant, they have a low refractive index of 1.49, while polycarbonate and polystyrene have a high refractive index of 1.59, but have the disadvantage of large chromatic aberration. are doing. In recent years, research has been conducted to produce resins with high refractive index and small chromatic aberration, and Japanese Patent Application Laid-Open No. 13747/1983 describes di(meth)acrylic esters, (meth)acrylic esters, or styrene monomers. There is a description of a high refractive index resin composition obtained by copolymerizing a monomer with a monomer having a chlorine, bromine or iodine atom in an aromatic ring, and carbonates or ( There is a description of a transparent high refractive index resin composition obtained by copolymerizing meth)acrylic acid esters. It is stated that the resin composition thus obtained has a high refractive index of 1.60, small chromatic aberration, and a light transmittance of 85% or more. However, monomers with chlorine, bromine, or iodine atoms in their aromatic rings become solid needle-like crystals at room temperature as the amount of halogen atoms they contain increases.
When used alone, it is extremely difficult to fill the mold with the monomer and degas it during cast polymerization, and the resulting polymer is extremely brittle and unsatisfactory in terms of heat resistance and weather resistance. Furthermore, if the above monomers are dissolved in (meth)acrylic acid esters, cast polymerization is possible in the same process as ordinary liquid monomers.
Even in this case, as the content of the monomer increases, the impact strength, heat resistance, and weather resistance of the resulting polymer also decrease. We inventors conducted research aimed at obtaining a resin for lenses that has a high refractive index and low chromatic aberration, as well as excellent transparency, impact resistance, and heat resistance. However, by copolymerizing specific monomers in a specific ratio, the residual monomers in the resin can be reduced. They discovered that it is possible to obtain a resin that has a high refractive index and low chromatic aberration, and also satisfies the transparency, impact resistance, heat resistance, weather resistance, etc. desired as a resin for lenses. The invention was completed. That is, this invention is based on the formula

Tribromophere represented by [Formula] 40-90% by weight of nil methacrylate units, formula

5 to 35% by weight of methyl methacrylate units represented by [formula], general formula () [In the formula, R represents hydrogen or a methyl group, and n is an integer of 1 to 23. ] 2 to 30% by weight of at least one type of polyethylene glycol di(meth)acrylate unit represented by
and expression

[Formula] [However, x is an integer from 1 to 5. ] A copolymer consisting of 3 to 40% by weight of at least one type of brominated phenyl acrylate unit represented by the following, characterized in that it has an Abbe number of at least 34 and a refractive index of at least 1.55. be. In this invention, the content of tribromophenyl methacrylate units is preferably 40 to 90% by weight.
50-80% by weight is preferred. The higher the content of tribromophenyl methacrylate units, the better the refractive index, hardness, heat resistance, hygroscopicity and flame retardancy of the resulting resin. If the
Weather resistance also decreases. On the other hand, if the content of tribromophenyl methacrylate units is less than 40% by weight, the refractive index value is small and the object of the invention cannot be achieved. The content of methyl methacrylate units is preferably 5 to 30% by weight, preferably 15 to 25% by weight. If the content of methyl methacrylate units is less than 5% by weight, it will not only be difficult to dissolve tribromophenyl methacrylate, but also tribromophenyl methacrylate dissolved during various processes such as injection into a mold and degassing. Workability deteriorates, as it is necessary to maintain the temperature at a high temperature to prevent precipitation, and as a result, defects such as polymerization distortion are likely to occur. Content of methyl methacrylate units is 50% by weight
If it exceeds this value, the refractive index and heat resistance will decrease. Monomers constituting the polyethylene glycol di(meth)acrylate unit represented by the general formula () include diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol Examples include those with an average molecular weight of 400, 600, and 1000. The content of polyethylene glycol di(meth)acrylate units represented by the general formula () is 2 to 30
% by weight, preferably from 5 to 20% by weight is suitable. If the content of polyethylene glycol di(meth)acrylate units represented by the general formula () is less than 2% by weight, the resulting resin composition will have insufficient impact resistance, and if it exceeds 30% by weight, the resulting resin will be unsatisfactory. Not only does the amount of residual monomer from the polymerization increase, resulting in a decrease in heat resistance, but also the shrinkage of the polymer increases at the end of the polymerization, which tends to cause partial peeling of the resin from the mold surface, resulting in poor surface properties. In the general formula (), the value of n is preferably in the range of 1 to 23, and among these, the range of 4 to 20 is particularly effective in improving impact resistance. The content of brominated phenyl acrylate units having 1 to 5 bromine atoms in the aromatic ring used in this invention is suitably 3 to 40% by weight, preferably 5 to 30% by weight. If the content of brominated phenyl acrylate units is less than 3% by weight, the desired effect of reducing residual monomers will be small, and if it exceeds 40% by weight, although the residual monomers will be reduced, the heat resistance will decrease and the mold surface will deteriorate. A phenomenon of partial peeling occurs. That is, in the present invention, by using brominated phenyl acrylate having 1 to 5 bromine atoms in the aromatic ring, a high polymerization rate can be obtained without significant decrease in refractive index and heat resistance. According to the present invention, it is suitably used for a lens having the above composition, having an Abbe number, which is a measure of chromatic aberration, of 34 or more, preferably 35 or more, and a refractive index of 1.55 or more, preferably 1.58 or more. Resin can be obtained. The resin of this invention can be obtained by polymerization in a suitable mold in the presence of a polymerization initiator. Examples of such polymerization initiators include lauroyl peroxide, benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxyisobutyrate,
t-Butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, di-t-
Organic peroxides such as butyl diperoxyisophthalate or 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 1-azobis-1-cyclohexanecarbonitrile, Known radical initiators such as dimethyl-2,2'-azobisisobutyrate can be used alone or in combination. As described above, the lens resin of the present invention not only has a higher refractive index than conventionally known CR-39 and polymethyl methacrylate, and has smaller chromatic aberration than polycarbonate and polystyrene, but also has the surface properties necessary for a lens resin. It has surface hardness, high impact resistance, excellent workability, high heat resistance, and low moisture absorption, so lenses made with this resin have excellent morphological stability during use. In addition, known ultraviolet absorbers such as salicylic acid esters, benzophenones, and benzotriazoles, mold release agents such as higher alcohols, higher fatty acids, and waxes can be added to this resin. The present invention will be specifically explained below with reference to Examples. Example 1 After heating and dissolving 50 parts by weight of tribromophenyl methacrylate and 30 parts by weight of tribromophenyl acrylate in 15 parts by weight of methyl methacrylate at 50°C, 5 parts by weight of polyethylene glycol dimethacrylate of n=14 was added, Furthermore, lauroyl peroxide
0.05 part by weight was added and stirred. Insoluble matter was removed through a filter, and the mixture was poured into a glass plate-making cell prepared by sandwiching a vinyl chloride gasket between two sheets of flat glass placed 5 mm apart. After degassing under reduced pressure, polymerization was carried out at 80℃ for 2 hours, and then at 130℃2
After being allowed to stand for a while, it was cooled to obtain a 5 mm flat plate. The refractive index of this plate was measured at 25°C using an Atsube refractometer and was found to be 1.60, and the Atsube number was 36.6. In addition, the total light transmittance is 90% and the residual monomer content is 1.4.
%, and the Bitskart softening point (VSP) was 138°C. As a measure of the impact resistance of the obtained plate, we tried cutting it with a circular saw cutter, drilling holes with a drill press, etc., and found that it had sufficient workability as a plastic material for lenses. The outline of the cutter and drill press used in the test is as follows. Circular saw cutter Drilling machine model Outer diameter 255mm Outer diameter 2mm Number of teeth 100 Number of revolutions 500rpm Teeth width 3mm Number of revolutions 2800rpm Rake angle 0° Lead angle 20° Outside diameter angle 15° Examples 2 to 9 Comparative examples 1 to 6 Examples Table 1 shows the physical properties of the resin prepared in the same manner as in Example 1. For comparison, commercially available plastic materials for lenses are also listed. It is clear from this that the physical properties of the resin obtained in this example are excellent.

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Claims (1)

[Claims] 1 40 to 90% by weight of tribromophenyl methacrylate units represented by the formula [Formula], 5 to 30% by weight of methyl methacrylate units represented by the formula [Formula], general formula () [In the formula, R represents hydrogen or a methyl group, and n is an integer of 1 to 23. ] 2 to 30% by weight of at least one type of polyethylene glycol di(meth)acrylate unit represented by
and Formula [Formula] [However, x is an integer from 1 to 5. ] A resin for lenses, which is a copolymer comprising 3 to 40% by weight of at least one type of brominated phenyl acrylate unit represented by the formula, and which has an Abbe number of at least 34 and a refractive index of at least 1.55.