JPS58221801A - Plastic lens - Google Patents

Abstract

PURPOSE:To increase the refractive index by copolymerizing methyl methacrylate with alpha-methylstyrene in a specified ratio. CONSTITUTION:Methyl methacrylate is copolymerized with alpha-methylstyrene represented by the structure formula in 90:10-60:40 weight ratio. The refractive index of the resulting copolymer is increased in accordance with increase in the percentage of alpha-methylstyrene, yet when >40wt% alpha-methylstyrene is contained in the copolymer, the copolymer becomes fragile and unpractical. When the percentage of alpha-methylstyrene is <10wt%, the refractive index is reduced to <=1.50.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plastic lens with a high refractive index.

Plastic lenses are becoming more widely used in optical products because they are lighter than traditional glass lenses, have the potential for mass production, and are expected to be inexpensive. .

Currently, there are glass lens materials whose main components are diethylene glyconoσ bisallyl carbonate and methyl methacrylate called acrysilub for casting, and polymethyl methacrylate, polycarbonate, etc. are commonly used for injection molding. However, compared to conventional glass lenses, there are far fewer types of materials in practical use for both casting and injection molding. Moreover, in the case of glass lenses, there is a considerable range of refractive index from low to high power and dispersion, whereas plastic lens materials have a small variety of materials and have a refractive index of 1.49. ~1.60, which is extremely narrow compared to glass lenses.

This poses a serious problem when designing lenses. For example, in the case of eyeglass lenses, the refractive index is smaller than that of glass lenses, so the center thickness and curvature are large, giving the user a different impression from the appearance of conventional glass glasses. As another example, in camera lenses, microscope lenses, etc., one way to eliminate various aberrations such as chromatic aberration, spherical aberration, and coma is to combine lenses with different refractive indexes and dispersion. However, it is difficult to use this method in the case of plastic lenses because there are only a few types of them. In view of the above, there is a strong desire for plastic lenses having various refractive indexes and dispersions in addition to the currently used plastic lens materials (diethylene glycol bis alicarbonate, polymethyl methacrylate, etc.).

The present invention has been made in view of these points, and has impact resistance equivalent to that of plastic lenses obtained by polymerizing methyl methacrylate, is colorless and transparent, and is superior to plastic lenses made of methyl methacrylate. The present invention also provides a plus lens with a higher refractive index. That is, the present invention is based on the fact that by adding α-methylstyrene represented by the following structural formula to methyl methacrylate and copolymerizing it, a plus J: tinkle lens that satisfies the above requirements can be obtained.

4B-1, JP-A-58-221801 (2) A plastic lens obtained by polymerizing methyl methacrylate and having an increased refractive index is a plastic lens obtained by copolymerizing styrene. In this case, although the refractive index becomes high, the structure does not have a structure in which methyl methacrylate and styrene molecules are arranged alternately, but instead takes a so-called block copolymer-like structure in which each molecule has a number of consecutive molecules. Therefore, when looking at the lens as a whole, the molecular orientation is partially uneven. Alternatively, problems such as differences in light transmittance may occur.

On the other hand, when a-methylstyrene according to the present invention is copolymerized, the molecules of methyl methacrylate and α -methylstyrene do not have a block copolymer structure, so changes in molecular orientation and light transmittance may occur. few.

Methyl methacrylate and α-methylstyrene can be mixed in any ratio, and as the mixing ratio of α-methylstyrene increases, the refractive index also increases.

However, if the mixing ratio of α-methylstyrene exceeds 40% by weight, it becomes brittle and becomes impractical. Also, 5be--
If the mixing ratio of α-methylstyrene is less than 10% by weight, the refractive index will be 1.60 or less.

As a polymerization initiator for copolymerizing methyl methacrylate and α-methylstyrene, a conventional thermal polymerization catalyst can be used. However, since α-methylstyrene has a slow polymerization rate and a relatively low ceiling temperature, it is preferable to use a thermal polymerization catalyst that can be cleaved even at low temperatures.

In addition, the plastic lens according to the present invention can be produced by directly pouring a transparent mixed solution of methyl methacrylate, a-methylstyrene, and a polymerization initiator into a mold having a desired shape and copolymerizing it (so-called casting method). It is possible to obtain. It is also possible to copolymerize by suspension polymerization or emulsion polymerization, then pelletize to produce a material for injection molding, and use this material to obtain the glass lens of the present invention by injection molding. be.

In order to facilitate mold release, a known mold release agent may be applied to the surface of the mold in advance, or an internal mold release agent may be added to the resin.

Ribe-7 Examples of the present invention will be described below.

[Example 1] Diameter 50 mm, radius of spherical surface 200. Prepare a concave glass mold and a flat glass mold, and set the edge thickness between the two glass molds to 3.
A gasket was inserted so that the distance was 1 mm. On the other hand, the mixing ratio of methyl methacrylate and α-methylstyrene was set as shown in the table below, each was mixed and dissolved, and 1 part by weight of benzoyl peroxide as a polymerization initiator was mixed and dissolved in this solution to form a transparent solution. . This solution was poured into glass molds and polymerized at 60°C for 3 hours and then at 90°C for 5 hours. The refractive index of the completed convex plastic lens was measured. The results are shown in the table below. In addition,
For comparison, the table also shows the measurement results of the refractive index of a plastic lens obtained by polymerizing only methyl methacrylate.

(Blank below) Page 7 "■ Comparative Example [Example 2] 70 parts by weight of methyl methacrylate and 30 parts by weight of α-methylstyrene were mixed and dissolved, and 1 part of azobisisobutyronitrile was added as a polymerization initiator to this solution. Part by weight was dissolved to form a transparent solution. 10Oy of this solution and 300V of water were charged into a reactor, and suspension polymerization was carried out at 60°C for 2 hours and then at 90°C for 4 hours.Then, it was pelletized and methyl methacrylate and α - An injection molding material of methylstyrene copolymer was produced.Meanwhile, the diameter was eiom, and the radius of curvature of one spherical surface was 2.
00 mm N Radius of curvature of the other spherical surface 300 m
m.

A mold for manufacturing a biconvex lens was manufactured, and the mold was attached to an injection molding machine. Then, the biconvex plastic lens was obtained by injection molding using the injection molding material prepared in advance. The refractive index of the obtained lens was measured and found to be 1,529.

As is clear from the above explanation, the present invention is a plastic lens material made by copolymerizing methyl methacrylate and α-methylstyrene, and according to the present invention, it is possible to provide a plastic lens with a high refractive index. Therefore, its practical value is great.

Claims (1)

[Claims] Methyl methacrylate and α- represented by the following structural formula
Plastic lens 0 made of a resin obtained by copolymerizing a composition with a weight ratio of 90:10 to 60:40 with methylstyrene.