JPS6127501A - Manufacture of synthetic resin optical element having refractive index distribution - Google Patents

Abstract

PURPOSE:To form as one body an optical element having a refractive index distribution by putting a monomer for forming a network polymer into a vessel having a spherical forming surface, polymerizing it partially, and diffusing and polymerizing a monomer having a different refractive index to said monomer. CONSTITUTION:A monomer Ma for forming a network polymer Pa of a refractive index Na is injected into a cylindrical forming vessel 2 having a bottom face consisting of a spherical surface of a prescribed radius of curvature R, the inside of the vessel is brought to nitrogen substitution, and thereafter, it is polymerized partially, and a transparent gel object 1 whose surface is smooth is formed. Subsequently, a monomer Mb for forming a polymer Pb having a refractive index different from Na is injected onto the surface of the transparent gel object 1 in the vessel 2, and after the nitrogen substitution, the vessel 2 is heated, the monomer Mb is diffused and polymerized in the direction vertical to its surface from the surface into the transparent gel object 1, and a refractive index distribution which is varied continuously in the axial direction is formed. Thereafter, an optical element is manufactured by completing the polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION J.-7 Technical Field of the Invention The present invention relates to a method for manufacturing a synthetic resin optical element having a refractive index distribution in the axial direction.

3-2 Prior Art In recent years, it has been proposed to correct aberrations of spherical lenses by creating a refractive index distribution in the optical axis direction. Then, the refractive index distribution in the optical axis direction is expressed by the following equation (1) or (2), n(z)-no(/-tZ) (
1) n (z) -n □ V7:17-(2) (In the formula, n(z) is the refractive index at a point located at a distance of 2 from the center of the spherical surface in the optical axis direction, and no is the refractive index at the center of the spherical surface. , t is a positive constant, and 2 is the distance from the center of the spherical surface in the optical axis direction), it has been theoretically shown that the spherical aberration of the lens is dramatically reduced.

The above-mentioned axially graded index lens generally has a three-dimensional distribution in which all the equirefractive index surfaces are perpendicular to the optical axis, but it is also possible to consider lenses in which the equirefractive index surfaces are curved surfaces.

Expanding this concept, it is thought that aberrations can be determined freely by giving a spherical lens a refractive index distribution such that the equirefractive index surface is a flat surface or a spherical surface with a certain curvature. The technology is extremely useful not only for correcting aberrations of seven lenses, but also for achieving any desired combination of focal length and aberration for a lens in a lens system consisting of a combination of lenses, for example. 0 3, -3 Problem to be solved In order to form such a refractive index distribution, it is sufficient to form a composition distribution that exhibits a predetermined refractive index distribution in the material, for example, by using inorganic glass. In some cases, ion exchange or OVD
It can be formed by methods such as the law. However, when inorganic glass is used, both ion exchange and 0VDK require enormous amounts of heat and vacuum equipment, which is not very practical. Accordingly, organic glasses are advantageous for manufacturing curved lenses with a refractive index distribution.

On the other hand, the use of synthetic resin to manufacture lenses for use in optical devices has become popular in recent years, and cameras using plastic lenses are also being manufactured recently. especially,
Recently, attempts have been made to manufacture aspheric lenses that reduce spherical aberration by precision injection molding, but it is extremely difficult to manufacture molds with precise shape accuracy, and it is difficult to reduce the distortion caused by injection molding. Since it is also difficult to remove, the current situation is that the desired performance cannot be obtained.

Such defects can be greatly improved by manufacturing a spherical lens having a refractive index distribution as described above. A flat plate method is already known as a method for manufacturing a spherical lens having the above-mentioned refractive index distribution.

However, such a method has disadvantages in that post-processing such as cutting or polishing takes time and cost, and furthermore, the formed refractive index distribution cannot be fully used effectively.

3.-q OBJECT OF THE INVENTION An object of the present invention is to provide a seven-body molding method that can solve the above-mentioned drawbacks in a method of manufacturing a spherical lens having such a refractive index distribution.

3-5 Summary of the Invention The method of the present invention that achieves the above objects includes: (a) reticular polymers (including copolymers) having a refractive index of Ha;
Monomers (including monomer mixtures) Ma forming Pa are placed in a cylindrical molding container having a spherical molding surface with a constant radius of curvature ±R, and partially polymerized to form a transparent gel object. Step (b) Adding a monomer (including a monomer mixture) that forms a polymer (including a copolymer) PA having a refractive index Nb different from that of the Ha in a liquid, gas, or atomized state. Step (c) of diffusing and polymerizing from the flat or spherical surface of the transparent gel object in the axial direction of the cylinder to form a refractive index distribution in the transparent gel object in which the refractive index changes continuously in the axial direction of the cylinder; (c) heating, etc. The gist of the present invention is a method for manufacturing a synthetic resin optical element having a refractive index distribution by integral molding, which includes a step of completing polymerization and fixing the refractive index cloth. The present invention will be explained in detail below.

First, refractive index NaO network polymer (including copolymer) pa
A cylindrical container having a flat molding surface and a spherical molding surface with a constant radius of curvature ±R is filled with monomers (including monomer mixtures) Ma that form the , and is partially polymerized and molded into a transparent gel object. do. This transparent gel body contains 0 to 0% by weight of a component insoluble in a solvent (a polymer with a network structure).

Next, a monomer (including a monomer mixture) forming a polymer (including a copolymer) having a refractive index NA different from that of Na
MA is brought into contact with the transparent gel object in the state of either liquid, gas, or mist droplets, and is diffused and polymerized from the plane or spherical surface of the transparent gel object in the axial direction of the cylinder, so that the refractive index changes in the axial direction of the cylinder. to form a continuously changing refractive index distribution. B (The three methods in which a is in the liquid, gas, and mist state are each Tokko Sho!;!;-1111/% Tokko Shoj4-37!;
2/ and special application 1984-'133! The refractive index distribution is fixed by applying the present solution and the like to complete the polymerization by heating or the like according to the diffusion and polymerization method in the method of manufacturing a synthetic resin optical transmission body described in IK. Various examples of axial gradient index lenses that can be molded by the method of the present invention are shown in FIGS. 1A to 1FK.

These lenses 10 are composed of one refractive surface //A being a flat surface and the other refractive surface //B being a convex or concave spherical surface, and the inside thereof is given a refractive index distribution that changes in the lens axis direction. . The equirefractive index surfaces 12 shown in FIG. 1A and B are perpendicular to the optical axis, and those shown in C and D are spherical refractive surfaces.
It has a spherical shape with the center of the negative area almost coincident with B, and E,
The lens shown in F has a spherical shape with the center of curvature in the opposite direction to the spherical refractive surface.

In addition, in each lens shown in FIG. 1A to F, the direction of increase/decrease in refractive index is the maximum on the spherical refractive index surface side, and the planar refractive surface//AK:
There are two cases: case 5, which has a distribution that decreases sequentially toward the plane refractive surface //A side, and dream case, which has a distribution that is maximum on the plane refractive surface //A side and decreases sequentially toward the spherical refractive surface //B side.

Each lens shown in B, C, and F in Figure 1 has a low refractive index on the spherical side, and lenses A, D, and H have a low refractive index on the flat side to eliminate spherical aberration. becomes smaller than In general, the above combination of lens shape and refractive index distribution is used to create a single lens with low aberrations, or to create a lens with positive or negative aberrations that corrects the aberrations of other lenses used in combination. be selected accordingly,
The method of the present invention can produce any of these types of lenses.

As the monomer Ma to be the raw material for the transparent gel object in the present invention, a monomer having two or more types of groups among allyl group, acrylic acid group, methacrylic acid group, or vinyl group can be used. . Next, specific examples of monomer Ma will be given.

(1) Allyl compound 7 Diallyl esters such as diallyl talate, diallyl isophthalate, diallyl terephthalate, diethylene glycol bisallyl carbonate; triallyl esters such as triallyl trimellidate, triallyl phosphate, triallyl phosphite; allyl methacrylate; Unsaturated acid allyl esters such as allyl acrylate.

(2) Compound represented by R1, -R2-R3 A compound in which R1 and R3 are both a vinyl group, an acrylic group, a vinyl ester group, or a methacrylic group: R1 and R3
A compound in which one of these groups is one of the following three groups: a vinyl group, an acrylic group, a methacrylic group, and a vinyl ester group, and the other is one of the remaining three groups. Here, R2 can be selected from the divalent groups shown below.

C- OH3-(c;H20H20)m-OH20H2-(m-0-
20) (cH2)P-(P=3~1S) (OH2)i'OH200HQ, (1l-yl-'
~3) (OH2) (3) A mixture of the monomers (1) and (2) above, or at least one of the five monovinyl compounds, vinyl esters, acrylic esters, and hymethacrylic esters. A mixture of a species and the monomer (1) or (2) above (or a mixture thereof).

Furthermore, examples of the monomer Mb include the following.

(4) A compound represented by 0I (2=O-000Y, where X is a hydrogen atom, an alkyl group, or a phenyl group, (OH2)74H(J-i-za), i-, a propyl group, 1- Butyl group, S-butyl group, t-butyl group, (h-
o~2) and -(OH20H20)p-OH20H3(7'=/
-6), or -(OF2)
a-F(a-t-+), -(J2((3F2)b H(
b-/-za), -cn2ca2o-cu2cr3, -(cH2CH20)c OF2(3F2H(c-/~
4'), -CH2CH20・CH2(OF2)aF(a
-/-4), -CH2(OF2)do(GFz)zF(
(1-t ~x, 1=t-4) and -3i (002H5
) represents a group selected from the group consisting of a.

(5) Compound represented by 0H2-aHoa-Rd.
0 However, in the formula, Rd is -(OH2)f-OH3(f-0-
Represents a group selected from the group consisting of 2>, -(cH2)gHCg1~3), and (ho~2).

(6) A mixture of the monomers of (41 and (5)).

Any of the above (1) to (3) as the monomer Ha and (4) to (6) as the monomer Hb can be combined.

In addition, in order to adjust the gelation state of the transparent gel object, (
As mentioned in section 3), the method of adding a crosslinking monomer Mar monomer having one unsaturated group and GBr4, C
A method of adding a chain transfer agent such as 01+*mercap'tans or a method of using both in combination is effective.

3-B Effect of the Invention According to the method of the present invention, not only a spherical lens with small spherical aberration, but also a lens with the required focal length and spherical aberration can be integrally molded, and there is no need for post-processing steps. , it is possible to manufacture a spherical lens with a precise refractive index distribution at almost the same cost as a currently manufactured plastic molded lens.

3-7 Examples of the invention The present invention will be explained in more detail below using Examples.

For example, in the case of diffusing and polymerizing KMb in the transparent gel body in a liquid state, as shown in FIG. The liquid is injected into a cylindrical molded container 2 having a bottom surface made of . Close the cock and seal.

The container is left standing so that the liquid level is perpendicular to the central axis of the container, and then heated at a predetermined temperature for a predetermined time to form the transparent gel object 1 with a smooth surface.

Next, a monomer (including a monomer mixture) Hb that forms a polymer (including a copolymer) Pb having a refractive index different from that of N''a is injected into the transparent gel body in the container through the injection tube t. After that, the inside of the container was replaced with nitrogen again and sealed, and the container was placed in a constant temperature bath and heated at a predetermined temperature for a predetermined time to remove the monomer Mb. It is diffused and polymerized into the transparent gel object l from the surface in a direction perpendicular to the surface to form a refractive index distribution in which the refractive index changes continuously in one direction (in the illustrated example, the direction of the central axis of the cylindrical container).

Thereafter, by further heat-treating at a predetermined temperature for a predetermined period of time to complete the polymerization, a constant radius of curvature R such that the refractive index changes continuously in the thickness direction from one plane to the other convex surface as shown in FIG. It is possible to manufacture a lens consisting of a convex surface and a flat surface.

Next, a case will be described in which the lens shown in FIG. 1A is manufactured by diffusing and polymerizing Mb in the form of gas or mist droplets from one direction into the transparent gel body.

First, the transparent gel body is formed in a container in the same manner as described above.

Thereafter, the monomer Hb is heated externally at a predetermined temperature to vaporize (gaseous state) or atomized using ultrasonic waves, a spray nozzle, etc. (fog droplet state), and a predetermined amount of nitrogen is added as a carrier gas. , onto the surface of the transparent gel object in the container. By heating the container at a predetermined temperature for a predetermined time, the monomer Mb
is diffused and polymerized into a transparent gel object in a direction perpendicular to its surface to form a refractive index distribution in which the refractive index changes continuously in one direction.Nitrogen gas is then fed into the container again. After nitrogen substitution, a heat treatment is performed at a predetermined temperature for a predetermined time to complete polymerization, thereby producing a lens consisting of a convex surface with a constant radius of curvature R and a flat surface with a refractive index distribution in the thickness direction.

When diffusing and polymerizing in a gaseous state, if the pressure of the Mb vapor in the atmosphere containing monomer Mb vapor is too low, the amount of Mb diffused within the gel body will be small and the desired refractive index distribution will not be obtained. Since there is no
It is 1g or more.

In the above manufacturing method, when each of the monomers Ma and Mb becomes a polymer, the refractive index Na or Nb may be higher than the other, but 1. The absolute value of the refractive index difference is preferably o, oos or more.

When the refractive index Na is larger than Nb, by using the above nine methods, the refractive index distribution expressed by the above formula (1) or (2) is obtained in the optical axis direction, and in the plane perpendicular to the optical axis, the refractive index is A synthetic resin convex lens with uniformity can be obtained by integral molding.
It is possible to manufacture a lens with significantly reduced spherical aberration compared to conventional lenses with a constant refractive index. Also, N
If b is larger than Na, the spherical aberration increases, but it is used to correct spherical aberration in a lens system that produces spherical aberrations with equal absolute values and opposite signs.

The above is an example of manufacturing a synthetic resin optical element (Fig. 1A) having a refractive index distribution in which the refractive index changes in the axial direction from a flat surface to the other convex surface with a radius of curvature R in a plano-convex lens in order to correct spherical aberration. However, according to the present invention, other figures 1B-F! A synthetic resin optical element having i types of refractive index distribution can also be easily manufactured.

For example, to manufacture a lens as shown in FIG. 1B, a cylindrical container 20 having a convex surface with a constant radius of curvature R as shown in FIG.
Instead, a cylindrical container having a concave surface with a constant radius of curvature R as shown in FIG. 3 may be used, and the subsequent manufacturing method is similar to that of the lens shown in FIG. 1A above. When Na<Nb, the lens becomes a concave lens with low spherical aberration.

Also, Fig. 1 0. To manufacture a lens as shown in D, a cylindrical molding container having a flat molding surface 2A and a spherical molding surface 2B as shown in FIGS. In λ, the transparent gel is first carefully removed from the upper part of the mold, which has a concave surface, and then a cylindrical container upper part 7 similar to that shown in FIG. After that, if the manufacturing method of the lens shown in Fig. 1A is followed, the monomer M/L will be diffused and polymerized from the spherical surface of the gel body, and the equirefractive index surface will be on the spherical surface of the lens. It is possible to form a refractive index distribution that is concentric with respect to the other.

Furthermore, in order to manufacture a lens as shown in FIG. 1EK,
A method similar to the method for manufacturing the lens and the lens shown in FIG. 1C may be used. However, in the 441iU (41), the case where H4 is diffused from the convex surface of the transparent gel object is different.

In this case, a mask with a small circular hole in the center is aligned with the center of the transparent gel object and placed on the convex surface, and then the monomer M4 is placed in the container as shown in Figure (A). and spread it from the convex side.

Then, MA diffuses and polymerizes radially within the transparent gel object, producing a lens as shown in FIG. 1E.

Finally, to manufacture a lens like the one shown in Figure 1 FK,
The transparent gel body is first formed in a cylindrical container as shown in FIG. 3(a). Thereafter, the upper part of the flat mold is carefully removed, and the mask ring with a small circular hole lrA in the center is aligned with the center of the transparent gel object and placed on the flat surface in the same manner as in the manufacturing method of the lens shown in FIG. 1E. After placing the monomer MA in the container as shown in Fig. 6, it is diffused from the flat side. Then, the MA diffuses and polymerizes radially in the transparent gel body, and the first A lens as shown in Figure FK is manufactured.In Figures 1A to 1F, the magnitude of spherical aberration can be controlled by adjusting the conversion rate of the transparent gel object and the temperature and time during diffusion. .

As described above, according to the present invention, a lens can be manufactured by freely determining the spherical aberration.

[Brief explanation of drawings]

1A to 1F are cross-sectional views showing examples of combinations of various lens shapes and uniform refractive index distribution surface shapes that can be manufactured by the method of the present invention, and FIG. 2 is an example of a method for molding a convex spherical lens by the method of the present invention. Figure 3 is a cross-sectional view showing an example of a method for molding a concave spherical lens, and Figures 1 (a) and (b) show that molding of the base material and diffusion of monomer Mb are performed in separate containers. 5 is a sectional view showing an example of molding a convex lens, FIG. 5 is a sectional view showing an example of molding a concave lens using the same method as above, and FIG.
) and (b) are cross-sectional views showing an example of a method for molding a lens having a distribution shape such that the center of curvature of the uniform refractive index distribution surface of the lens is on the opposite side to the center of curvature of the refractive surface of the lens. l...transparent gel object, 2...molded container J II 6
11 Monomer M injection tube l... Monomer Mb injection tube 10... Lens //A,
//B--Refractive surface 12... Equal refractive index surface Figure 1 Figure 6 N

Claims (1)

[Claims] (a) A network polymer (including a copolymer) with a refractive index of Na, Pa
A process of placing monomers (including monomer mixtures) Ma forming the molecule into a cylindrical container having a spherical molding surface with a constant radius of curvature ±R, and partially polymerizing it to form a transparent gel object. (b) A monomer (including a monomer mixture) M^b forming a polymer (including a copolymer) P^b having a refractive index N^b different from that of Na is a liquid, gas, or mist. Diffusion in the form of droplets from the plane or spherical surface of the transparent gel object in the axial direction of the cylinder and polymerization to form a refractive index distribution in the transparent gel object in which the refractive index continuously changes in the axial direction of the cylinder ( c) A method for manufacturing a synthetic resin optical element having a refractive index distribution by one-piece molding, which includes a step of fixing the refractive index distribution by completing polymerization by heating or the like.