JPH0782121B2 - Optical element manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing an optical element. For more details,
For example, a method for manufacturing an optical element such as an aspherical lens, a Fresnel lens, a focus plate of a camera, etc. that constitutes an optical system such as a camera for photography, a video camera, a microscope, a telescope or an optical disc pickup part, particularly on a glass base material. The present invention also relates to an optical element having a resin layer made of an ultraviolet curable resin. In the following, the present invention will be described mainly by taking the case of manufacturing an aspherical lens as an example, but of course the present invention is not limited to the case of manufacturing such an aspherical lens, and the above-mentioned Frennel is used. It can also be applied when manufacturing a lens or a focus plate of a camera.

[Conventional technology]

Conventionally, an aspherical lens having a structure in which a resin layer is laminated on a glass base material is known. A so-called replica method using an ultraviolet curable resin is generally used as a method for producing such an aspherical lens.

FIG. 8 is a diagram for explaining a basic mode at the time of producing an aspherical lens by such a replica method.
Reference numeral 3 denotes a glass base material, 3 denotes a mold, 2 denotes a resin layer made of an ultraviolet curable resin, and 4 denotes ultraviolet rays for curing the ultraviolet curable resin forming the resin layer 2. As shown in FIG. 8, after a UV curable resin monomer for forming a resin layer 2 is laminated between a glass base material 1 having a desired shape and a mold 3, the UV curable resin is applied to the UV curable resin. The ultraviolet ray 4 is irradiated and cured, and the mold 3 is separated from the resin layer 2 to obtain an aspherical lens having the resin layer 2 on the glass base material 1.

This replica method is an excellent method for mass production because an aspherical lens having an optical surface having a desired shape can be obtained relatively easily because the optical surface is formed using an ultraviolet-curable resin that is easy to mold. However, it is difficult to manufacture a high-precision aspherical lens. This is mainly due to the curing shrinkage of the ultraviolet curable resin at the time of curing, but it is also due to insufficient consideration of the ultraviolet rays to be irradiated, such as the relationship between the irradiation intensity of ultraviolet rays and the curing time. .

Conventionally, as the ultraviolet ray, one having a large energy sourced from a high pressure mercury lamp with an output of about 80 W / cm is generally used, but such an ultraviolet ray is used, for example, by using an acrylate-based ultraviolet curable resin. When forming a resin layer of such an aspherical lens as described above, the time required for curing is extremely short, such as several seconds to several minutes, and excellent mass productivity is exhibited. However, when ultraviolet rays having high energy intensity as described above are used, it is usual that the resin cures rapidly, and along with that, rapid cure shrinkage of the resin occurs. Under such conditions, resin shrinkage usually occurs in the direction in which the distance between the mold 3 and the glass base material 1 is shortened, as shown in FIG. 9, that is, in the direction of the arrow in the figure, For this reason, the transfer accuracy of the obtained aspherical lens from the mold, particularly the surface accuracy, often deteriorates.

In order to prevent such a rapid contraction of the resin and improve the accuracy, it is effective to use ultraviolet rays having a small energy. That is, under such conditions, the shrinking direction of the resin becomes slow along the mold surface as shown by the arrow in FIG. 10, and the transfer accuracy can be improved. However, in this case, since the irradiation energy is small, the curing time becomes as long as several tens of minutes to several hours, and there is a drawback that mass productivity is insufficient. Further, in this case, since the energy of ultraviolet rays is small, if the irradiation time is insufficient, the curing of the resin does not proceed completely, so that unreacted monomer remains in the resin and the product is cured. It may deteriorate the weather resistance such as the light resistance and the high temperature and high humidity resistance at the time, and may cause the aging of the product.

[Problems to be solved by the invention]

The present invention has been made in view of the above points, and an object of the present invention is to eliminate the drawbacks of the method for producing an optical element of the conventional example, and particularly to provide a resin layer made of an ultraviolet curable resin. An object of the present invention is to provide a method for manufacturing an optical element that can be formed with high accuracy without impairing weather resistance and that is excellent in mass productivity.

[Means for solving problems]

The above object of the present invention is achieved by the following present invention.

In the method for producing an optical element having a resin layer made of an ultraviolet curable resin on a glass base material, a first step of irradiating the ultraviolet curable resin with ultraviolet rays having a small energy to partially cure the ultraviolet curable resin; A second step of curing the ultraviolet-curable resin by irradiating the ultraviolet-curable resin that has completed the first step with ultraviolet rays having energy higher than that of the first step. Optical element manufacturing method.

[Action]

In the method of the present invention, after irradiating the ultraviolet curable resin on the glass base material with the ultraviolet light having the small energy, the resin layer is formed on the glass base material by irradiating the ultraviolet light having the larger energy than that, It is possible to obtain an accurate optical element without causing a rapid resin contraction as in the method. Further, since the resin can be sufficiently cured by ultraviolet rays having large energy in a short time, it is possible to mass-produce the optical element having excellent weather resistance.

Hereinafter, the present invention will be described in detail with reference to the drawings as necessary.

First, FIG. 1 shows an example of an aspherical lens obtained by applying the method of the present invention.

This aspherical lens is formed by laminating a resin layer 2 made of an ultraviolet curable resin on a glass base material 1. The base material 1 is made by polishing a normal optical glass into a spherical surface. The resin layer 2 has an aspherical shape that is rotationally symmetric with respect to the optical axis, but in an aspherical lens, the resin layer 2 is usually formed thinner than the base material 1, It is preferable that the average thickness is about 10 to 300 μm.

In manufacturing the optical element as described above, in the present invention, the ultraviolet curable resin forming the resin layer 2 is irradiated with ultraviolet light having a smaller energy and then further irradiated with ultraviolet light having a larger energy.

Specifically, for example, an appropriate amount of UV-curable resin monomer is poured into an aspherical mold 3 having a transfer surface having a shape opposite to the desired aspherical shape as illustrated in FIG. The base material lens 1 is stacked so as to keep a constant distance from the mold 3.

Next, the base material lens 1 side is irradiated with an ultraviolet ray having a small energy to partially cure the ultraviolet curable resin on the base material lens 1, and then an ultraviolet ray having an energy larger than that is further irradiated to the resin. Is cured to form the resin layer 2. At this time, of course, a transparent mold may be used to irradiate the ultraviolet rays from the mold side. Thereafter, an external force is applied to the mold 3 to remove the mold from the surface of the resin layer to obtain an aspherical lens as illustrated in FIG.

In the present invention, a well-known ultraviolet curable resin can be used without particular limitation. Specifically, for example, polyfunctional or monofunctional acrylates such as polyester acrylate, polyurethane acrylate and epoxy acrylate, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, trimethylolpropane tri (meth) acrylate, tris ( A polyfunctional or monofunctional (meth) acrylate such as tri (meth) acrylate of 2-hydroxyethyl) isocyanurate, and a photopolymerization initiator such as benzophenone, benzoin, acetophenone, etc. are combined respectively, and at least one of the above-mentioned compounds is used. A vinyl-based radical-polymerization type resin composed of a mixture containing several kinds is preferably used, but a polyene-polythiol addition-polymerization type resin or an epoxy resin or the like that is cured by ultraviolet rays If it can be used.

The ultraviolet rays used in the first step of the present invention are:
It is preferable that the energy is as small as 5 to 10 mW / cm ² . An ultraviolet fluorescent lamp, which is a so-called chemical lamp, is suitable as an ultraviolet ray generating source for generating such ultraviolet rays, and its output is preferably about 0.1 to 100 W (watt).

The irradiation time of ultraviolet rays in the first step depends on the type of resin used, but is preferably several W in the case of a commonly used acrylate-based ultraviolet curable resin.
It is advisable to use a lamp with an output of about 20 W and perform irradiation until the gelation rate (reaction rate) of the resin reaches about 70 to 95%.
Then, such a gelation rate is measured in advance for a resin to be used, and for example, the relationship between the gelation rate and the irradiation time as shown in FIG. 6 is obtained, and this may be used as a guide for the irradiation time. In the case of an acrylate-based ultraviolet curable resin, the irradiation time of the ultraviolet rays in the first step is several minutes to several
10 minutes is enough.

The ultraviolet ray used in the second step of the present invention needs to have a larger energy than that in the first step, and specifically, it is preferably about 10 to 500 mW / cm ² . As a source of such ultraviolet rays, output 80 ~
A high pressure mercury lamp of about 180 W / cm or a metal halide lamp is suitable. Using such a lamp, for example, the resin partially cured to a gelation rate of about 70 to 95% as described above is further cured. Of course, the irradiation time of the ultraviolet ray in the second step depends on the kind of the resin used in the same manner as in the first step.

FIG. 7 shows an example of the gelation rate of the resin and the ultraviolet irradiation time in order to more specifically explain the ultraviolet irradiation in the present invention.

In FIG. 7, the first step is up to t _x . In the first step, as described above, the gelation rate g _x is 70 to 95%.
It is good to finish the ultraviolet irradiation at some point. t _{x to} t _y is the second
In this second step, ultraviolet rays having a higher energy than in the first step are irradiated, and the state where the resin is rapidly cured is shown.

Although not particularly described above, the present invention is limited only to the case of manufacturing an aspherical lens having a constitution in which the resin layer 2 is provided on the convex surface side of the base material lens 1 as illustrated in FIG. Of course, the invention is also applied to the case where the resin layers 2 and 2a are provided on both the convex surface side and the concave surface side of the base material lens 1 as illustrated in FIG. 2, or when the resin layer is provided only on the concave surface side, for example. It is possible. Of course, when manufacturing such an aspherical lens, for example, as shown in FIG. 4, an adhesion improving layer made of a silane coupling agent 6 or the like is provided to improve the adhesion between the resin layer 2 and the base material 1. Alternatively, it is possible to make a contrivance such as providing a functional layer 7 such as a moisture-proof protective layer or an antireflection layer on the resin layer 2 as illustrated in FIG. 5 as desired. Of course, in addition to the above-mentioned aspherical lens, for example, in the case of manufacturing an optical element such as a Frennel lens, a focusing plate of a camera, or a beam splitter element in which the resin layer 5 illustrated in FIG. 3 has a mountain-shaped repeating shape. The present invention is applicable.

〔Example〕

In order to describe the present invention more specifically, examples of the present invention will be shown below.

Example A base material lens having a diameter of 40.5 mm and a radius of curvature of convex surface R ₁ of 41.34 mm
R, concave surface R ₂ radius of curvature 203 mm R, center thickness 11.33 mm, material BK
An aspherical lens having an optical lens (meniscus convex lens) as illustrated in FIG. 7 and having a resin layer provided only on the convex surface R ₁ side of the base material lens was prepared as follows.
The mold used was one in which the center thickness of the resin layer to be formed was 150 μm and the curvature of the resin surface was 41.49 mmR (deviation = about +50 μm).

First, as a UV curable resin, a mixture of urethane modified polyester acrylate 50 parts by weight tris (2-hydroxyethyl) isocyanurate triacrylate 20 parts by weight dicyclopentyloxyethyl acrylate 30 parts by weight 1-hydroxycyclohexyl phenyl ketone 2 parts by weight Was adjusted, and 0.3 g of the mixture was poured into a mold, and a base material lens was superposed thereon so that the center thickness of the resin layer was 150 μm.

Next, from the base material lens side, a chemical lamp with an output of 20 W was used to apply ultraviolet rays with an energy intensity of 0.9 mW / cm ² to the resin layer.
Irradiated for minutes. The gelation rate at this time was 88.5%.

Next, following the above ultraviolet irradiation, the resin layer was irradiated with ultraviolet rays having an energy intensity of 130 mW / cm ² for 2 minutes using a high-pressure mercury lamp with an output of 80 W / cm to complete the curing of the resin on the base material lens. Then, by removing from the resin layer surface of the mold, an aspherical lens having an aspherical resin layer made of the above ultraviolet curable resin was obtained.

For the aspherical lens thus obtained, the shape of the resin layer was measured with a contact type aspherical surface measuring instrument, and its weather resistance was measured after leaving it under high temperature and high humidity at a temperature of 70 ° C. and a relative humidity of 85% RH for 500 hours. It was evaluated by observing the appearance.
The results are shown in Table 1.

As is clear from Table 1, the shape accuracy and weather resistance were good.

Incidentally, upon the irradiation of the ultraviolet rays, the relationship between the irradiation time of each lamp using the above resin and the gelation rate was obtained in advance, and the irradiation was performed using this as a guide. The gelation rate was determined by using a Soxhlet extractor with an extraction solvent of toluene and methyl ethyl ketone (1: 1) and an extraction time of 24 hours.
The cured resin is extracted over time, and is obtained from the weight of the resin before and after the extraction by the following formula (I).

Gelation rate (%) = [{(weight of resin before extraction)-(weight of resin after extraction)} / (weight of resin before extraction)] × 100 (I) Comparative Example 1 UV irradiation is performed in two steps. However, an aspherical lens was obtained in the same manner as in the example except that only a high pressure mercury lamp with an output of 80 W / cm was used.

This aspherical lens was evaluated in the same manner as in the examples. The results are shown in Table 1.

As is clear from Table 1, this aspherical lens was good in weatherability but inferior in accuracy.

Comparative Example 2 An aspherical lens was obtained in the same manner as in Example except that UV irradiation was not performed in two steps and only a chemical lamp having an output of 20 W was used.

This aspherical lens was evaluated in the same manner as in the examples. The results are shown in Table 1.

As is clear from Table 1, this aspherical lens had good accuracy but poor weather resistance.

[Effects of the Invention] As described above, according to the present invention, it is possible to manufacture an optical element having a resin layer made of an ultraviolet curable resin with high accuracy and without sacrificing weather resistance, and with good mass productivity. It became so.

[Brief description of drawings]

1 to 5 are sectional views of elements for explaining various examples of optical elements obtained by applying the method of the present invention,
6 to 7 are views for explaining the relationship between the irradiation time of ultraviolet rays and the gelation rate of the resin according to the method of the present invention, and FIGS. 8 to 10 are outlines for explaining the outline of the conventional method. FIG. 8 is an explanatory view, and FIG. 8 is a sectional view of an element including a mold at the time of ultraviolet irradiation, and FIGS. 9 and 10 are enlarged views of a portion A shown by a broken line in FIG. ing. 1 ... Glass base material, 2, 2a, 5 ... Resin layer 3 ... Mold, 4 ... UV ray 6 ... Silane coupling agent 7 ... Functional layer

Claims (3)

[Claims] 1. A method of manufacturing an optical element, comprising: irradiating an ultraviolet ray curable resin layer between a glass base material and a mold with ultraviolet rays, and then separating the die from the cured ultraviolet ray curable resin layer. A step of irradiating ultraviolet rays having a small energy to partially cure the ultraviolet curable resin; and an ultraviolet ray having a larger energy than that of the first step is applied to the ultraviolet curable resin which has finished the first step. A second step of irradiating and curing the ultraviolet curable resin. 2. The method for manufacturing an optical element according to claim 1, wherein in the first step, the ultraviolet curable resin is partially cured to a gelation rate of 70 to 95%. 3. The energy of ultraviolet rays in the first step is 0.5 to 10 mW / cm ² , and the energy of ultraviolet rays in the second step is 10 to 500 mW / cm ² . A method of manufacturing an optical element according to the first or second range.