JP2001221901A - Plastic lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a plastic lens in which a multifocal structure or the like useful as a multifocal lens spectacle can be easily obtained. SOLUTION: The plastic lens in which a multifocal structure or the like can be formed is obtained by forming a region E having the distribution of different refractive indices which gives different refractive power from that of the base material consisting of a polymer resin in the base material. The region E having the distribution of different refractive indices is formed as locally spread from the peripheral part to the center of the base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic lens which can be used, for example, as a multifocal spectacle lens.

[0002]

2. Description of the Related Art Plastic lenses have advantages such as excellent workability, light weight, and excellent impact resistance, and are already widely used in many fields. However, it is not always the case with today's plastic lens applications that the excellent properties possible for plastics are fully utilized.

[0003]

For example, in the case of a spectacle lens which is one of the major uses of a plastic lens, there is a problem with a multifocal spectacle lens. One of the manufacturing methods of a multifocal spectacle lens is by curved surface processing, and it can be said that this method is the only method currently used in practical use. However, the curved surface processing method has a major problem when using a progressive multifocal type. In other words, in the case of a progressive multifocal type having excellent appearance without a clear external boundary between the far and near areas having different refractive powers, if the curved surface processing method is used, the far and near areas are used. It is unavoidable that the part connecting is an aspheric surface that causes astigmatism,
For this reason, there is a problem that problems such as narrowing of the visual field, fluctuation of the visual field, and distortion of the visual field occur (for example, JP-A-8-234146).

On the other hand, such a problem can be avoided in the case of the refractive index distribution method, which is another method for manufacturing a multifocal spectacle lens. That is, in the refractive index distribution method, in order to obtain the refractive power by the lens action by the refractive index distribution formed using the property that the refractive index distribution, which is one of the characteristics of plastic, is easily provided, the distance region and the near region are used. Without the appearance of the border
Therefore, it is not necessary to provide a structure that causes astigmatism in a portion connecting the distance region and the near region. However, for example, Japanese Patent Application Laid-Open No. 62-90601 and Japanese Patent Application Laid-Open No. 5-127132
No., the refractive index distribution method proposed so far as an example disclosed in each publication of JP-A-5-288901,
For various reasons, in particular, it is difficult to control the distribution at the time of forming the refractive index distribution.

In the case of a method in which a refractive index forming material is partially diffused and penetrated from the refractive surface of a spherical lens as disclosed in Japanese Patent Application Laid-Open No. 62-90601, for example, the refractive index distribution is determined by the thickness of the lens. Since it also occurs in the direction, it becomes extremely difficult to control the refractive index distribution for the intended lens action, and there is great difficulty in designing the lens. Further, as in the example disclosed in JP-A-5-127132, by polymerizing a monomer in a cylindrical container,
In the case of producing a rod having a refractive index distribution in the radial direction and cutting out the rod to obtain a lens, a high-order refractive index such that the refractive index distribution coefficient α becomes 3 or more for multifocalization. Although it is considered that a distribution is required, it is difficult to obtain such a refractive index distribution accurately and stably, and even if it can be realized, the range of the rod diameter that can be achieved is 10 to 20 mm. It is only about the size of a contact lens for practical vision correction. As a method similar to this method, a rod having a refractive index distribution in the radial direction is created by polymerizing the monomer after diffusing another monomer from the outside into a gel rod made of a certain monomer, and forming this rod. There is a method of obtaining a lens by cutting out, but the same can be said for this method. Further, as disclosed in JP-A-5-288901, a method of diffusing and infiltrating a monomer for forming a refractive index distribution from one refraction surface of a preform formed of a polymer involves a method in which a refractive index distribution of a lens is reduced. Since it also occurs in the thickness direction, there is the same problem as in the technique disclosed in Japanese Patent Application Laid-Open No. 62-90601.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to easily obtain a multifocal structure which is useful as, for example, a multifocal spectacle lens by a structure different from the conventional one. The purpose is to provide a plastic lens that can be used, and to provide a manufacturing method thereof.

[0007]

In a plastic lens according to the present invention, a different refractive index distribution region is partially formed in a base material having a lens action formed of a polymer resin. The lens effect of the base material may be obtained only by curved surface processing with the base material having a uniform refractive index, or may be obtained by an isotropic refractive index distribution if possible. If such a plastic lens is used for, for example, a multifocal spectacle lens, the refractive power of the base material gives a lens portion for a distance region, for example, and the refractive power in the different refractive index distribution region. A lens portion for the near zone is provided. The major feature of the present invention as a structure in which a different refractive index distribution region is partially formed in such a base material is that a different refractive index distribution region is formed so as to partially expand from the outer peripheral portion to the center portion of the base material. A region is formed, that is, the gradient direction of the refractive index is directed from the outer peripheral portion of the base material to the center portion, and thus the refractive index is gradually changed from the outer peripheral portion of the base material toward the center portion. That is, a distribution area is formed. Such a refractive index distribution structure is different from any of the conventional refractive index distribution methods.

For example, in comparison with the method of diffusing and penetrating the refractive index forming substance from the refraction surface described above (Japanese Patent Laid-Open Nos. 62-90601 and 5-288901), it is possible to avoid such a problem. it can. That is, in the structure of the present invention in which the different refractive index distribution region is formed so as to partially expand from the outer peripheral portion to the central portion of the base material,
The substance for forming the refractive index distribution is partially diffused and penetrated in the radial direction from the restricted portion of the outer periphery of the base material. Therefore, it is possible to avoid the occurrence of a refractive index distribution in the lens thickness direction, which causes a difficulty in controlling the refractive index distribution, which is a major obstacle in making the refractive index distribution method practical.

In comparison with the above-mentioned refractive index distribution rod method (Japanese Patent Laid-Open No. 5-127132), taking a case of a multifocal spectacle lens as an example, in the present invention, the base material is partially Since the different refractive index portion region is formed, it is not necessary to make the refractive index distribution higher order to give a difference in refractive power, and the diffusion and penetration range of the substance for forming the refractive index distribution is also The size of the final spectacle lens can be reduced to half or less, and the problem of the formation of the refractive index distribution and the difficulty in controlling the refractive index, which is also a major obstacle to the practical use of the refractive index distribution method, can be solved.

As can be understood from the above description, the plastic lens according to the present invention has a different refractive index distribution region that gives a base material formed of a polymer resin a refractive power different from that of the base material. The base material is formed so as to partially spread from the outer peripheral portion toward the central portion.

The refractive index distribution in the different refractive index distribution region is:
It can be formed of a non-polymerizable substance (a substance that does not polymerize or a substance that has already been polymerized and does not react with a monomer) or can be formed of a copolymer. In general, it is preferable to use a copolymer in view of the stability of the formed refractive index distribution over time. The formation of the refractive index distribution by the copolymer is achieved by a copolymer having a different monomer composition ratio between the monomer (Ma) and another monomer (Mb) that gives a polymer having a refractive index different from that of the polymer formed by the monomer (Ma). This is done by giving the distribution to the polymer. On the other hand, in the case of using a non-polymerizable substance, a non-polymerizable substance is diffused and penetrated into a base material to generate a concentration gradient therein, thereby forming a refractive index distribution.

The above-described plastic lens according to the present invention is suitable for obtaining a multifocal lens having two or more regions having different refractive powers. Such characteristics make it possible to use the plastic lens according to the present invention for a multifocal spectacle lens.

Although the plastic lens according to the present invention can be manufactured by various methods, in the present invention,
Regarding the formation of the refractive index distribution by the copolymer, the following method is one of preferred manufacturing methods. That is, a step of preparing a gel body for a base material from a monomer (Ma) that gives a polymer of a polymer resin for a base material, wherein the monomer (Ma)
Diffusing another monomer (Mb) that gives a polymer having a refractive index different from the refractive index of the polymer into the gel body so as to partially spread from the outer periphery toward the center, and the monomer (Ma) ) And monomer (Mb)
Is a production method comprising a step of polymerizing

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In carrying out the present invention, a base material can be formed from a polymer resin obtained from various polymerizable monomers. Preferred polymerizable monomers include, for example, methyl methacrylate, benzyl methyl methacrylate, 2,2,2-trifluoroethyl methyl methacrylate, 4-methylcyclohexyl methacrylate, cyclohexyl methacrylate, furfuryl methacrylate, 1-phenylethyl methacrylate,
Methacrylates such as phenylcyclohexyl methacrylate and phenyl methacrylate; styrenes such as styrene, p-methylstyrene, p-chlorostyrene, o-chlorostyrene, p-bromostyrene, and o-bromostyrene; p-divinylbenzene; o-divinyl Examples thereof include vinyl compounds such as benzene, vinyl acetate, vinyl polpionate, vinyl benzoate, and vinyl isophthalate.

On the other hand, as described above, a non-polymerizable substance can be used for forming the different refractive index distribution region, or a copolymer can be used. Each of these non-polymerizable substances and copolymers has advantages and disadvantages. For example, according to the copolymer, the stability of the refractive index distribution over time is excellent, but the transparency is reduced due to light scattering caused by the mixture of polymers having different refractive indexes. Conversely, the non-polymerizable substance has high transparency, but is inferior in stability over time of the refractive index distribution. However, in the case of a spectacle lens or the like, since the thickness may be very thin, it can be said that the decrease in transparency as described above has no substantial effect. Therefore, when the transparency is not so important as a spectacle lens, a copolymer is usually used.

In the case where the refractive index distribution is formed by a copolymer, two or more monomers appropriately selected from the above-mentioned combinations of monomers capable of forming a copolymer are used. . That is, while a polymer obtained from one kind (or more than one kind in some cases) of a monomer is used as a base material, another monomer that gives a polymer having a refractive index different from that of the base material monomer is diffused into the base material. Infiltrate to form a distribution of copolymers having different composition ratios. In addition, as a substance which can be used when forming a refractive index distribution with a non-polymerizable substance, for example, benzyl phthalate-n-butyl, 1-methoxyphenyl-1-phenylethane, benzyl benzoate, bromobenzene, o-
Examples thereof include dichlorobenzene, m-dichlorobenzene, 1,2-dibromoethane, 3-phenyl-1-propanol, dibenzyl ether, phenoxytoluene, diphenyl ether, biphenyl, and diphenyl sulfide.

The width of the different refractive index distribution region formed in the base material and the state of the refractive index distribution there are appropriately designed according to the functional purpose of the lens to be obtained. For example, in the case of a multifocal lens for a spectacle lens, a distribution in which the refractive index distribution coefficient α is about 2 from the outer peripheral portion toward the center in the lower half where the base material is divided into upper and lower portions or a slightly narrower range. Is formed so that the refractive index gradually decreases. In order to form such a different refractive index distribution region in the refractive index distribution state, for example, in the case of a copolymer, the refractive index of one polymer (monomer for a base material) is the same as that of a polymer. It is a preferable condition that the refractive index of the polymer by the above-mentioned monomer is at least 0.001 or more.

The principle of the manufacturing method will be described below by taking as an example a case where a thin lens such as a spectacle lens is obtained by forming a different refractive index distribution region using a copolymer. First, as a first step, the lens is formed into a thin plate shape having a curved surface shape corresponding to the curved surface shape of the final lens (this may be spherical, aspherical, or even flat). A gel body for a base material is prepared. As shown in FIG. 1, a mold 1 having a shape corresponding to a curved shape given to a base material is provided.
Then, a material (sol) obtained by adding a polymerization initiator and a crosslinking agent to a monomer (Ma) for a base material is injected, and then the monomer (M) is added.
In a), partial polymerization and cross-linking are caused to form a gel body for a base material. Various known techniques can be used for gelling the monomer. Preferable examples include a method of irradiating light having a large energy such as ultraviolet light, a method of heating, and the like. For example, if the monomer (Ma) is methyl methacrylate and this is to be gelled by light irradiation, the crosslinking agent may be EDMA, for example.
(Ethylene glycol dimethacrylate) and Darocur 1173 (2-hydroxy-2-
One example is the use of methyl-1-phenyl-propane-1-on).

In the next step, a different refractive index distribution region is formed by diffusing and penetrating another monomer (Mb) into the gel material 2 for the base material obtained as described above. For this purpose, an immersion method is usually used, but other appropriate methods can be used as necessary. In the case of the immersion method, as shown schematically in FIGS. 2 and 3, the gel body 2 is shielded by providing a partially exposed portion 3 on the outer peripheral portion, and the gel body 2 is filled with the monomer ( Mb). When this immersion is continued for a predetermined time, the monomer (Mb) diffuses and permeates so as to partially spread from the partially exposed portion 3 of the outer peripheral portion toward the center of the gel body 2, and the base of the hetero-refractive index distribution region Is formed, that is, a region where the monomer (Mb) is diffused with a certain concentration gradient in the gel of the monomer (Ma). The size of the region serving as the base can be freely set depending on the size of the exposed portion 3 on the side surface of the gel body 2, that is, the manner of shielding the gel body 2.
The required immersion time varies depending on immersion conditions such as temperature and pressure, the combination of monomer (Ma) and monomer (Mb), or the diffusion distance of monomer (Mb). If there is, it is usually less than 24 hours. Monomer (Mb)
When methyl methacrylate is used as the monomer (Ma), for example, styrene, which can form a copolymer with methyl methacrylate, is used. The above-mentioned shield of the gel body 2 can also be performed by providing an opening in a part of the mold 1.

Next, a polymerization step is performed. In the polymerization step, similarly to the preparation of the gel body, the monomer (Ma) remaining in the gel body 2 and the monomer (Mb) permeating the gel body 2 are polymerized by irradiating the gel body 2 with ultraviolet rays or the like. Then, in a region which is a base of the above-mentioned different refractive index distribution region, the monomer (Mb) has a composition ratio corresponding to the concentration of the monomer (Mb) there.
b) and the monomer (Ma) are copolymerized. As a result, copolymers having different composition ratios of the monomer (Mb) and the monomer (Ma) are distributed in accordance with the concentration distribution in which the monomer (Mb) has been formed in the gel body 2, whereby the different refractive index distribution region is formed. It is formed. On the other hand, in other regions, a homopolymer composed of only the monomer (Ma) is generated. In this way, a different refractive index distribution region is formed by the copolymer of the monomer (Ma) and the monomer (Mb) in the base material of the homopolymer containing only the monomer (Ma), and a lens having two regions having different refractive powers is obtained. Can be

[0021]

[Experimental Example] Hereinafter, an experimental example simulating the above manufacturing method will be described. In this experiment, a different refractive index distribution region was formed in the base material having no lens action, and the monomer (M
a) is methyl methacrylate (the refractive index of the polymer is 1.
492) and styrene (the refractive index of the polymer is 1.592) as the monomer (Mb). First, the monomer (M
A gel body was prepared in a). The gel body is a disk having a diameter of 60 mm and a thickness of 3 mm. The gel body is produced by sandwiching a ring made of a fluororesin having a thickness corresponding to the thickness of the gel body to be obtained with a glass plate to form a mold, and adding a monomer (Ma), a polymerization initiator, and a cross-link to the mold. A sol-like material composed of an agent was injected, and irradiation was performed with ultraviolet light. EDMA is used as a cross-linking agent, and 8 wt% of EDMA is added. Darocur 1173 is used as a polymerization initiator.
% Was added. In this case, the gelation time by ultraviolet irradiation is 9 minutes. The gel body thus obtained is immersed in the monomer (Mb) together with the above-mentioned mold and the monomer (Mb)
Was partially diffused and infiltrated into the gel body. This partial diffusion and penetration was performed by cutting out a part of the ring with a width of about 1/4 of the circumference. The immersion time was normal temperature and normal pressure and continued for about 24 hours. Thereafter, the monomer (Ma) and the monomer (Mb) were polymerized by irradiation with ultraviolet rays, and further subjected to a heat treatment. Ultraviolet irradiation was performed for about 48 hours in view of safety in stabilizing the refractive index distribution, and heat treatment was performed at 70 ° C. for about 5 hours.

FIG. 4 shows the result of measuring the refractive index distribution of the sample obtained as described above. FIG.
The ordinate and abscissa represent the distance (mm) from the center of the sample, the refractive index distribution is represented by a contour line of the refractive index, and the refractive index in the different refractive index distribution region E becomes closer to the center. The refractive index gradually decreases, and the refractive index is uniform in other regions. The relationship between the hetero-refractive index distribution region E and the other regions is very close to the relationship between the distance region and the near region in the progressive multifocal spectacle lens on the market by curved surface processing. there were. FIG. 4 shows the refractive index distribution state in a slightly simplified manner.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold into which a monomer has been injected.

FIG. 2 is an explanatory view of a state where a gel body is immersed in a monomer.

FIG. 3 is an explanatory diagram of a masking state of a gel body.

FIG. 4 is a diagram showing a refractive index distribution state of a sample obtained in an experiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Gel body 3 Exposed part E Different refractive index distribution area

Claims (4)

[Claims] 1. A plastic lens, wherein a different refractive index distribution region that gives a base material formed of a polymer resin a refractive power different from the refractive power of the base material from an outer peripheral portion to a central portion of the base material. A plastic lens characterized in that it is formed so as to partially expand toward. 2. The refractive index distribution of the different refractive index distribution region is a combination of a monomer (Ma) and another monomer (Mb) that gives a polymer having a refractive index different from that of the polymer formed by the monomer (Ma). The plastic lens according to claim 1, wherein the plastic lens is formed by a distribution of copolymers having different composition ratios. 3. A multifocal spectacle lens using the plastic lens according to claim 1. 4. The method for producing a plastic lens according to claim 2, wherein a step of preparing a gel body for a base material from a monomer (Ma) for providing a polymer of a polymer resin for a base material, Other monomers (Mb) which give a polymer with a refractive index different from that of the polymer according to (b)
And a step of polymerizing the monomer (Mb) and the monomer (Mb), wherein the step (d) is carried out so as to partially spread from the outer periphery toward the center in the gel body.