JPH0374166B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic resin article having a refractive index distribution.

In recent years, it has been proposed to correct aberrations in spherical lenses by creating a refractive index distribution in the optical axis direction.For example, in a convex lens formed by a spherical surface and a flat surface, The refractive index distribution is determined by the following formula (1) or (2) n(Z)=no(1-TZ) (1) n(Z)=no√1- (2) (where n(Z) is Z from the center of the sphere to the optical axis direction.
( _n0 is the refractive index at the center of the spherical surface, T is a positive constant, and Z is the distance from the center of the spherical surface in the optical axis direction). It has been theoretically shown that this can improve In order to form such a refractive index distribution, it is only necessary to form the composition distribution of the material. For example, when using inorganic glass, ion exchange is CVD, and when using organic glass, two-step copolymerization is used. Various methods are known.
However, when using inorganic glass, both ion exchange and CVD require enormous amounts of heat and vacuum equipment, which is not very practical. Therefore,
Organic glass is suitable for manufacturing a spherical lens material having the refractive index distribution as described above. By the way, the above-mentioned two-step copolymerization method is to partially polymerize the monomers that form the crosslinkable polymer into a gel state, and then diffuse another monomer from the surface into the gel body to form monomers. This method fixes the monomer composition distribution by forming a monomer composition distribution and then completing the polymerization, and the above object can be manufactured (Japanese Patent Publication No. 52-5857), but in this method, the refractive index The uniform distribution shape of the distribution does not form a uniform plane and tends to cause local distortion.

In other words, since the surface of an object in a gel state has relatively large irregularities, when a monomer is diffused from this gel surface, the isoconcentration surface of the diffused monomer, in other words, the equirefractive index distribution surface, is the same as that of the above gel. There is a problem that the distribution surface is distorted according to the unevenness of the body surface, and furthermore, the gel body swells as the monomer diffuses, and the distortion of the uniform refractive index distribution surface is further expanded.

An object of the present invention is to provide a method for manufacturing with high precision a synthetic resin article having a refractive index distribution that can greatly improve the drawbacks of ordinary plastic lenses having a uniform refractive index. .

The method of the present invention which achieves the above object comprises: (a) a monomer mixture containing at least two types of monomers having different refractive indexes and monomer reactivity ratios when turned into polymers in a container; (b) polymerization, such as by standing under conditions such that the energy applied to each part of the monomer mixture in the container is substantially uniform except for that due to gravitational and inertial forces; (c) a step of allowing the reaction to proceed and precipitating the precipitated polymer using gravity and/or inertial force to bring the entire monomer mixture into a gel state; and (c) the monomer mixture that has become a gel state. The gist of the invention is a method for manufacturing a synthetic resin article having a refractive index distribution, which includes a step of finally heating to complete polymerization.

Furthermore, according to the method of the present invention, an initial precipitated polymer layer is formed on the container wall surface, and later, polymer layers having different refractive indexes are sequentially deposited and laminated on this polymer layer. If the surface of the container wall is made sufficiently smooth, it is possible to obtain a uniform refractive index distribution surface with no local distortion along the wall surface of the container. This is extremely easy compared to the step copolymerization method in which the surface of the gel body is smoothed.

The monomer mixture used in the present invention may contain any number of monomers as long as they are plural, but at least two of them must satisfy the following conditions.

(1) Different monomer reactivity ratios.

(2) The refractive index of homopolymers obtained from each monomer is different.

Hereinafter, the present invention will be explained in detail. The present invention was basically completed based on the findings in the polymerization reaction of two or more types of monomers having different refractive indexes and monomer reactivity ratios when turned into polymers. That is, X types (X is at least 2) of monomers M ₁ , M ₂ , M ₃ ...Mx that satisfy the following conditions
Polymerize the mixture. In general, multicomponent copolymerization reactions are as follows. If the rate constant of the growth reaction Mi*+Mj→Mj* is Kij, the reactivity ratio Rij is defined as Rij=Kii/Kij, and there are X (X-1) reactivity ratios in the X-element copolymerization.

The monomer combinations of the present invention indicate the conditions to be satisfied. Now, two integers i and j are 1≦i and j≦
_{When there} is a relationship _such as Mi and monomer Mj
The mixing molar ratio of

(2) Regarding the refractive index, it is necessary that (2a) Ni (refractive index of Mi homopolymer) < Nj (refractive index of Mj homopolymer) or (2b) Ni (......) > Nj (......) be.

The case where X=3 will be specifically explained. In ternary copolymerization, the following nine types of growth reactions occur in competition.

M ₁ ※＋M ₁ →M ₁ ※(rate constant K ₁₁ ) M ₁ ※＋M ₂ →M ₂ ※( 〃K ₁₂ ) M ₁ ※＋M ₃ →M ₃ ※( 〃K ₁₃ ) M ₂ ※＋M ₁ →M ₁ *(rate constant K ₂₁ ) M ₂ *+M ₂ →M ₂ *( 〃 K ₂₂ ) M ₂ *+M ₃ →M ₃ *( 〃 K ₂₃ ) M ₃ *+M ₁ →M ₁ *( 〃 K ₃₁ ) M ₃ *+M ₂ →M ₂ *(〃K ₃₂ ) M ₃ *+M ₃ →M ₃ *(〃K ₃₃ ) The monomer reactivity ratio is defined by equation (3).

R ₁₂ =K ₁₁ /K ₁₂ R ₂₁ =K ₂₂ /K ₂₁ R ₁₃ =K ₁₁ /K ₁₃ R ₃₁ =K ₃₃ /K ₃₁ R ₂₃ =K ₂₂ /K ₂₃ R ₃₂ =K ₃₃ /K ₃₂ (3 ) The conditions that the combination of monomers M ₁ , M ₂ , and M ₃ of the present invention must satisfy are (1) Regarding the reactivity ratio (R ₁₂ (M ₁ /M ₂ ) _n +1)/{(M ₁ /M ₂ ) _n + R ₂₁ }＞1.1(
4) (R ₁₃ (M ₁ /M ₃ ) _n + 1) / {(M ₁ /M ₃ ) _n + R ₃₁ }＞1.1(
5) (R ₂₃ (M ₂ /M ₃ ) _n + 1) / {(M ₂ /M ₃ ) _n + R ₃₂ }＞1.1(
6) Here, (Mi/Mj) _n is the mixing molar ratio of monomer Mi and monomer Mj.

(2) Regarding the refractive index, (2a) n ₁ (refractive index of M ₁ homopolymer) < n ₂ (refractive index of M ₂ homopolymer) < n ₃ (refractive index of M ₃ homopolymer), or (2b) n ₁ > n ₂ > n ₃ . Here, both |n ₃ −n ₂ | and |n ₂ −n ₁ | are preferably at least 0.005.

Condition (1) is that as the terpolymerization progresses, the initial monomer
M ₁ rapidly polymerizes, then monomer M ₂ polymerizes,
It shows that monomer M ₃ polymerizes most slowly. In other words, the copolymer formed at the initial stage of polymerization contains a large amount of monomer _M1 , but as the polymerization progresses, the content of _M1 rapidly decreases until the content of monomer _M2 decreases. To increase. As the polymerization progresses further, the content of M ₂ also decreases, and the content of monomer M ₃ increases. If condition (2a) is satisfied, the refractive index of the copolymer produced will increase as the polymerization progresses, but by adjusting the type of monomer and the monomer charging ratio, the refractive index of the copolymer will increase as the polymerization progresses. The refractive index of the polymer can be gradually increased with the polymerization conversion rate over a wide range of conversion rates. If condition (2b) is satisfied, the refractive index of the copolymer decreases with the polymerization conversion rate.

In the case of a combination of two types of monomers M ₁ and M ₂ , it is sufficient that equation (4) holds regarding the reactivity (However, in this case, γ ₁₂ and γ ₂₁ are usually expressed as γ ₁ and γ ₂ , respectively. ).

In the present invention, it is desirable to select a monomer system that has poor affinity between the produced copolymer and the remaining monomers. Since the polymerization reaction proceeds at the same rate throughout the system, the generation of polymerization heat is the same everywhere in the system, creating no temperature non-uniformity, and therefore no convection can occur.

The precipitated copolymer is not transported by convection. Since the precipitated copolymer settles under the action of gravity and/or inertia, a polymer layer (containing monomers) is formed as the polymerization reaction progresses, forming a composition distribution and, ultimately, a refractive index distribution. be done. In a monomer system in which condition (2a) is satisfied regarding the refractive index, the refractive index of the part that precipitates first is low, and the refractive index of the part that precipitates last is high.

The opposite is true for condition (2b).

Monomers that can be used in the present invention are preferably monomers that form transparent polymers, but even if a single polymer tends to become opaque due to, for example, a high degree of crystallinity, If it becomes transparent when copolymerized, it can be used. Such monomers include polymerizable double bonds such as vinyl groups, acrylic groups, methacrylic groups, allyl groups, etc.
Compounds having one or more species are preferred, examples include vinyl chloride, vinyl acetate, styrene,
Phenyl vinyl acetate, vinyl benzoate, vinyl fluoride, vinylnaphthalene, vinylidene fluoride, vinylidene chloride, methyl acrylate, ethyl acrylate, 2,2,2-trifluoroethyl acrylate,
Benzyl acrylate, phenyl acrylate, naphthyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile, 2,2,2-trifluoroethyl methacrylate, phenyl methacrylate, benzyl methacrylate, naphthyl methacrylate, methacrylic acid 1, 1,3-trihydroperfluoropropyl, allyl benzoate, phenyl allyl ether, methacrylonitrile, α-methylstyrene, parachlorostyrene, butadiene,
1,5-hexadiene, vinyl acrylate, vinyl methacrylate, divinyl phthalate, divinyl isophthalate, divinylbenzene, divinylnaphthalene, ethylene glycol divinyl ether, α
- Vinyl naphthoate, β-vinyl naphthoate, diallyl phthalate, diallyl isophthalate, allyl acrylate, allyl methacrylate, β-methacrylate, methacrylic anhydride, diethylene glycol bisallyl ether, diethylene glycol bisallyl carbonate, tetraethylene glycol These include dimethacrylate, bisphenol A dimethacrylate, triallyl trimellitate, triallyl phosphate, triallyl phosphite, diphenyldiallylsilane, diphenyldivinylsilane, and the like.

Among these monomers, select monomers that satisfy the conditions of reactivity ratio and refractive index, and add to the mixture,
A thermal radical initiator such as a peroxide or an azo compound may be added. Examples include benzoyl peroxide, azobis-t-butane, and azobisisobutyronitrile.

The monomer mixture is placed in a mold and held in a predetermined shape. For example, as shown in Figure 1, metal,
A liquid monomer mixture 1 is filled into a lens mold 2 made of glass or the like, and the lens is left standing with its center axis 3 perpendicular. FIG. 2 shows an example of molding a flat lens material. The mold filled with the monomer mixture is placed under conditions such that the energy applied to each part of the mold is substantially uniform except for gravitational and inertial forces. That is, the conditions are such that light is irradiated from one direction and there is no heating element nearby. When applying heat, it must be applied uniformly from the surrounding area, and the rate of temperature rise must be slow enough to avoid creating a temperature gradient between the center and periphery of the container that are in contact with the heating medium. No. Under such conditions, the polymerization reaction will proceed substantially uniformly in each part of the container, and at a certain point, the same composition will be found everywhere within the container. A polymer will be forming.

In a polymerization system placed under such conditions, gravity is the only directional force acting, and the polymer formed within the system moves downwards due to gravity. It sinks and precipitates to the bottom. At this time, if it is applied to a centrifuge or the like, it will of course be deposited in the direction of inertial force. Therefore, by changing the direction of the polymerization system within the centrifuge, it is possible to create an article in which the direction of distribution is different in each part of the container, not just in one direction.

After precipitation of the polymer in the monomer mixture in the polymerization system is completed, heating is performed to complete the polymerization. This is because polymer precipitation occurs not only in monomers but also in a form containing monomers.

The method for manufacturing a synthetic resin article having a refractive index distribution has been described in detail above, and the present invention will be explained in detail using examples below. Note that the present invention is not limited to the following examples.

In the examples, the refractive index distribution was measured using an interference microscope.

Example 1 Ethylene glycol dimethacrylate (EDMA) and 2,2,2-trifluoroethyl methacrylate (3FMA) were mixed in equal amounts, and 2% benzoyl peroxide was added thereto. This was injected into a rectangular parallelepiped glass cell, wrapped in aluminum foil to prevent light from entering, and left at 20°C for 31 days. Next, it was kept at 40°C for 3 days, and after 1 day at 65°C, it was taken out from the cell. As a result, a refractive index difference of 0.01 was formed over a thickness of 5 mm from the bottom surface.

Example 2 Methyl methacrylate (MMA), benzyl acrylate (BZA), and phenyl vinyl acetate (VPAC) were mixed in a ratio of 3:1:1, and 0.8% benzoyl peroxide was added. This was placed in a glass cell, wrapped in aluminum foil, and left at 20°C for 64 days. After that, 40℃ x 3 days -65℃ x 1 day -25℃ x
Heat treatment was performed for 12 days at -65°C for 2 days.

As a result, a refractive index distribution as shown in FIG. 3 was obtained.

Example 3 Diethylene glycol bis(allyl carbonate) (CR-39) and 2,2,2-trifluoroethyl methacrylate were mixed at a ratio of 1:2, and 0.5% benzoyl peroxide was added. This was placed in a glass cell, wrapped in aluminum foil, and left indoors for 31 days. Thereafter, heat treatment was performed at 40°C for 3 days to 65°C for 1 day.

As a result, a refractive index distribution as shown in FIG. 4 was formed.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a state in which a monomer mixture is filled into a lens mold according to the present invention, Fig. 2 is a cross-sectional view showing an example using another mold, and Figs. 3 and 4 are 1 is a graph showing the refractive index distribution of polymers molded in Examples 2 and 3 of the present invention, and the vertical axis represents the refractive index difference Δn. 1... Monomer mixture, 2... Molding mold, 3... Lens central axis.

Claims (1)

[Claims] 1. A step of holding in a container a monomer mixture containing at least two types of monomers having different refractive indexes and monomer reactivity ratios when turned into polymers, and carrying out a polymerization reaction in the mixture. A step of allowing the polymer to advance and precipitate to settle using gravity and/or inertia force, and sequentially stacking the polymer on the bottom wall of the container to make the entire mixture into a gel state, and the monomers in the gel state. 1. A method for producing a synthetic resin article having a refractive index, the method comprising the step of finally heating a polymer mixture to complete polymerization.