JPS60175009A - Production of plastic optical element having refractive index distribution - Google Patents

Abstract

PURPOSE:To obtain easily an element having a refractive index distribution by polymerizing partly a monomer to form a transparent gel-like material, adding another monomer which provides a polymer having a different refractive index to the surface, diffusing the monomer from the surface in a perpendicular direction to polymerize the monomers and subjecting the polymer to curving. CONSTITUTION:A monomer Ma forming a net-like polymer having a refractive index Na (e.g., diallyl phthalate) is poured into a cylindrical vessel 2 and is partly polymerized by heating to form a transparent gel object 1. A monomer Mb which forms a polymer having the refractive index different from the refractive index of Na (e.g., ethyl acrylate) is poured onto the surface of the object 1 and is diffused from the surface in a perpendicular diretion; at the same time said monomers are polymerized by heating to form a refractive index distribution in which the refractive index changes continuously in one direction into the object 1. The object is heated in succession to complete the polymn. and to fix the refractive index distribution. The one surface of the resulted plymer is worked to have a curved surface by which the optical element having the refractive index distribution is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic resin optical element 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 in the optical axis direction is expressed by the following formula (1) or (2).
.

n (z)=no (t-tz) (1) n(z)
=noy7: 范(2) (In the formula, n(z) is the refractive index of a point located at a distance of 2 from the center of the spherical surface in the optical axis direction, no is the refractive index of the center of the spherical surface, t is a positive constant, 2 It has been theoretically shown that the spherical aberration of the lens can be dramatically reduced if the distance (distance in the optical axis direction from the center of the spherical surface) is satisfied.

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, when using inorganic glass, ion exchange or CVD may be used.
It can be formed by methods such as the law. However, when inorganic glass is used, both ion exchange and OVD require enormous amounts of heat and vacuum equipment, which is not very practical. Therefore, 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 equipment has become popular in recent years, and cameras using plastic lenses have recently been manufactured, but their optical performance is still inferior to that of glass*. It seems that it is inferior. This is said to be due to the fact that the coefficient of thermal expansion of plastic is about an order of magnitude larger than that of glass, and that when molded, it does not faithfully reflect the mold. Such defects can be greatly improved by using a spherical lens having a refractive index distribution as described above.

An object of the present invention is to provide a method for manufacturing a synthetic resin lens having a refractive index distribution simply and with high precision, which can greatly improve the drawbacks of conventional plastic lenses having a uniform refractive index. It is in.

That is, the present invention (barrel) has a reticular polymer (including a copolymer) with a refractive index of Na, Pa
A step of partially polymerizing the monomer (including monomer mixture) Ma forming the transparent gel body.

(t)) A polymer (
A monomer (including a mixture of monomers) that forms Pb (including a copolymer) is brought into contact with the transparent gel object in either a liquid, gas, or atomized state, and is applied from its surface to its surface. A process of diffusing and polymerizing in the vertical direction to form a refractive index distribution in which the refractive index changes continuously in one direction.

(C) fixing the refractive index distribution by completing the polymerization by heating, etc.; and (d) turning at least one side of the polymer with the refractive index distribution formed on a predetermined curved surface, for example, on the axis of the refractive index change direction. The key point is a method of manufacturing a synthetic resin optical element having a refractive index distribution, which includes the step of processing into a spherical surface centered at .

The present invention will be explained in detail below.

First, a container is filled with a monomer (including a monomer mixture) Ma that forms a network polymer (including a copolymer) having a refractive index of Ha, and a portion of the monomer (including a monomer mixture) is polymerized to form a transparent gel object. This transparent gel body contains 55% of a solvent-insoluble component (a polymer with a network structure).
Contains ~90% by weight.

A monomer (including a monomer mixture) forming a polymer (including a copolymer) having a refractive index Nb different from KNa
Mb is brought into contact with the transparent gel object in the form of liquid, gas, or mist, and diffused and polymerized from the surface in a direction perpendicular to the surface, resulting in refraction in which the refractive index changes continuously in one direction. form a rate distribution. The three methods in which Mb is in a liquid, gas, and mist state are each disclosed in the Japanese Patent Publication No. 111-111.
, Special Publication Showa 56-1J7jλl and Special Publication Showa,! 17-1
133! ; Diffusion in the method for manufacturing a synthetic resin optical transmission body described in It.

It can be carried out according to the polymerization method.

For example, by diffusing KMb in the transparent gel object in a liquid state,
Regarding the case of polymerization, as shown in Fig. 1, a predetermined amount of monomer Ma to which an initiator has been added is injected into a cylindrical container 2 through an injection pipe 3, and the upper liquid space inside the container λ is drained through an exhaust pipe. While exhausting at ≦, nitrogen gas is supplied through the nitrogen introduction pipe j to perform nitrogen replacement, and then the cock is closed to seal the tank.

The container is left standing so that the liquid level is parallel to the bottom wall 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.

Monomers (including monomer mixtures) that form Pb (including copolymers) with a refractive index different from that of KNa
A predetermined amount of b is injected onto the surface of the transparent gel object l in the container through the injection tube. Thereafter, the inside of the container is again replaced with nitrogen and sealed, and the container 2 is placed in a constant temperature bath and heated at a predetermined temperature for a predetermined time to transfer the monomer Wb from the surface into the transparent gel object l. By diffusing and polymerizing in the vertical direction, a refractive index distribution in which the refractive index continuously changes in one direction (in the illustrated example, the direction perpendicular to the bottom wall of the container) is formed.

After that, the polymerization is further completed by heat treatment at a predetermined temperature for a predetermined period of time, so that the refractive index changes continuously in two thickness directions from one side surface A to the other surface surface B as shown in Figure 2. A disc-shaped polymer base material g is obtained. Then, depending on the selection of monomers Ha and Mb, the contact surface JA side of monomer Mb has a maximum refractive index n1, and the back surface JB side has a minimum refractive index n2.
Or conversely, the maximum refractive index surface side where the back surface gB side has the maximum refractive index and the gA surface has the minimum refractive index is the axis in the direction in which the refractive index changes, that is, the surface roughness A and the surface roughness of the base material g. A spherical surface having a predetermined radius of curvature R centered at a point lO on the axis 9 perpendicular to B is processed by polishing or the like, and the lower refractive index side is processed into a flat surface.

As a result, a synthetic resin convex lens l/ having a refractive index distribution expressed by the above-mentioned equation (1) or (2) in the optical axis direction and a uniform refractive index in a plane perpendicular to the optical axis can be obtained. It will be done.

Next, a case will be described in which the base material g is prepared by diffusing and polymerizing KMb in the transparent gel body from one direction in the form of a gas or atomized droplets.

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

Thereafter, the monomer Mb is heated externally at a predetermined temperature to vaporize it (gaseous state) or is atomized using ultrasonic waves, a spray nozzle, etc. (fog droplet form a), and then a predetermined amount of nitrogen is added to the 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 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. Thereafter, nitrogen gas is fed into the container again, and after nitrogen substitution, heat treatment is performed at a predetermined temperature for a predetermined time to complete polymerization, thereby creating a base material having a refractive index distribution in two directions of thickness.

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 more than lig.

In the above manufacturing method, when each of the monomers Ma and Mb becomes a polymer, either the refractive index Na or Nb may be higher, but the absolute value of the refractive index difference is Q, 003 or higher. The above is preferable.

In a synthetic resin object having a refractive index distribution as shown in formulas (1) and (2) produced by the above method, the end face with a higher refractive index is processed into a spherical surface, and the end face with a lower refractive index is processed into a flat surface. When a convex lens is formed by using a convex lens, it is possible to manufacture a lens whose spherical aberration is significantly reduced compared to a conventional lens having a constant refractive index.

The method of the present invention is not limited to lenses in which one surface is spherical and the other surface is flat; it is also possible to manufacture lenses having a refractive index distribution such that both surfaces are spherical.

As the monomer Ma to be the raw material for the transparent gel object, a monomer having two or more groups selected from the group consisting of an allyl group, an acrylic acid group, a methacrylic acid group, and a vinyl group can be used. can. Next, specific examples of monomer Ma will be given.

(1) Allyl compounds diallyl esters such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diethylene glycol bisallyl carbonate; triallyl esters such as triallyl trimellitate, triallyl phosphate, triallyl phosphite, allyl methacrylate, acrylic Unsaturated acid allyl esters such as allyl acids.

(2) Compounds R1 and R represented by R1-R2-R3
3 is a vinyl group, an acrylic group, or a vinyl ester group.

or a compound that is a methacrylic group: one of R1 and R3 is one of the following groups: a vinyl group, an acrylic group, a methacrylic group, and a vinyl ester group, and the other is any one of the remaining three groups. A compound that is Here, R2 can be selected from the divalent groups shown below.

■ a - C Kichi 3 (CH2 (R20) "CH2CH2-(m-0-20)
”(OH2)P-(P-3~1s) (OH2)iH -0H2(j OH2(1*]-'~3)(CH2)j
H CH3CH3 (3) A mixture of the monomers of (1) and (2) above, or at least laI of the five types of monovinyl compounds, vinyl esters, acrylic esters, and methacrylic esters and the above (1) or a mixture with the monomer (or mixture thereof) of (2).

Furthermore, examples of the monomer Mb include the following.

(4) A compound represented by 0H2-C-000Y, where X is a hydrogen atom or a methyl group, ((3H2)
IH (1-1-1>, i-propyl group, i-butyl group,
S-butyl group, t-butyl group, (h-0-J) and -((3H2(3H20)p-(jH20H3(P
-/-4) or -(OF
2) a-F(at ~6), -OHg(OFg)bH
(b-/-za), -0H20H20・(H2CF3, (OH2CH20)c OFgOFgH(C-/-4'
), -0H2CH20・0H2(OF2)aF (a-
/-4), -0Hz (OF2)do(OF2)
IF (cl-/-2, 1-/-4) and -8i (0
Represents a group selected from the group consisting of 02Hs)3.

Compound 1 represented by (510H2-OHO(3-Rd), where Rd is -(IOHg)f-OHs (f
-0~2), -(OHg)gH(g-z~3), and (h-θ~ko).

(6) Mixture of monomers (4) and (5) 〇 Monomer M
(1) to (3) above as a, (4) as monomer Mb
Any of (6) to (6) 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 monomer having one unsaturated group to the crosslinkable monomer Ha and the method of adding a monomer having one unsaturated group (3Br 4 e
A method of adding a chain transfer agent such as 0C14e mercaptans or a method of using both together is effective.

Example 1 Polymerization opening 1. Diethylene glycol pisaryl carbonate (OR-J9) containing 2.0% by weight of benzoyl peroxide as an IT agent was placed in a cylindrical container 2 such as No. 11il.
After filling the container with nitrogen, the atmosphere inside the container was replaced with nitrogen and the container was sealed. This cylindrical container was heated at 0° C. for 22 minutes and then cooled to 0° C. to form a transparent gel body with a smooth surface inside the container. This gel body consists of an acetone-insoluble component (reticular polymer) 4 (/wt%), an acetone-soluble and methanol-insoluble component (#iI-like polymer aggregate, 3 wt%, methanol-soluble component) It consists of 49.4% by weight of components (monomers).

Next, about 20% by weight of methacrylic acid in the transparent gel body, 2
．． Cotrifluoroethyl (?FMA)'i: After injecting onto the transparent gel object in the volume, the container was placed in a constant temperature bath at 20''C and left for about 3 days.Then, the constant temperature bath was placed at 70℃.
The polymerization was completed by heat treatment for about 2 days. The synthetic resin body obtained in this way is removed from the container,
The whitened surface layer having a thickness of about 1 to 2 mm was scraped off to obtain a parallel plane disk-shaped base material. The results of measuring the refractive index distribution of this base material are shown by curve A in the graph of FIG.

In the graph of FIG. 4, the horizontal axis represents the depth from the surface of the base material on the diffusion initiation side, and the vertical axis represents the refractive index difference based on the diffusion initiation surface.

Next, the linear portion of the refractive index distribution A formed in the base material is left and the other portions are polished away, and at the same time, the high refractive index side is processed into a spherical surface and the low refractive index side is processed into a flat surface to form a convex lens. Obtained.

It was confirmed that the spherical aberration of this convex lens was extremely small and that it had excellent optical performance.

Example λ A gel body formed in a container λ as in Example 1 was
JFMA was added in a constant temperature bath at 70°C and left for 21 hours. The temperature bath was then raised to 70°C and heated for 2tI hours to complete polymerization. The whitened surface layer was removed. The results of measuring the refractive index distribution of the transparent resin body are shown as curve B in the graph in Figure μ.

Next, a convex lens was obtained by polishing the high refractive index side of the base material into a spherical surface and the low refractive index side into a flat surface.
After injecting FMk, leave it for λ days, ? FMA was diffused and copolymerized into the gel body. Then, 2 was kept at 70°C for an hour to complete the polymerization.

FIG. 3 shows the refractive index distribution of the transparent resin body obtained by removing the surface whitening layer. From the surface of this transparent resin body where the refractive index distribution forms a substantially straight line, the high refractive index surface is polished into a spherical surface and the low refractive index surface is polished into a flat surface using a range of 2 mm to +mm to a diameter of 13. A convex lens with a diameter of 1 mm was manufactured. The spherical aberration of this lens is shown by curve C in FIG. 6, and for comparison, the aberration curve of a lens with a uniform refractive index is shown by D.

It can be seen from FIG. 6 that the gradient index spherical lens obtained by the present invention has significantly less spherical aberration up to the outer periphery than a normal spherical lens.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an embodiment of the method of the present invention, Fig. 2 is a cross-sectional view showing a gradient index base material obtained as a result of diffusion polymerization, and Fig. 3 is a cross-sectional view showing a gradient index base material obtained by processing the same base material. A cross-sectional view showing a refractive index distribution type spherical lens, FIG. 1 and FIG. S are graphs showing specific examples of the refractive index distribution in the base material obtained by the method of the present invention, and FIG. The vertical axis is the distance from the optical axis, and the horizontal axis is the amount of spherical aberration. Ma, Mb Monomer l Transparent gel object 2 Container J, 4/ Monomer injection tube! Nitrogen introduction pipe t Exhaust pipe Za Base material with refractive index distribution 1/ Spherical lens with refractive index distribution Patent applicant Nippon Sheet Glass Co., Ltd. No. 1 I! 1 Figure 2 Figure 30 Factor 4 Figure 5 Figure 6 Door surface is nasal (mm)

Claims (1)

[Claims] (→ Network polymer (including copolymer) with refractive index Na, Pa
A step of placing a monomer (including a monomer mixture) Ma forming a container into a container and partially polymerizing it to form a transparent gel body. (b) A monomer (including a monomer mixture) Mb forming a polymer (including a copolymer) Pb having a refractive index Nb different from that of the Na is used in the transparent gel in a liquid, gas, or atomized state. A step of bringing the gel into contact with an object and causing it to diffuse in a vertical direction from the surface of the gel object and polymerize, thereby forming a refractive index distribution in the gel object in which the refractive index changes continuously in one direction. (phrase) a step of fixing the refractive index distribution by completing the polymerization by heating etc., and (d) a step of processing at least one side of the polymer on which the refractive index distribution has been formed into a curved surface. A method for manufacturing a synthetic resin optical element having a distribution.