JP3409383B2 - Manufacturing method of aspherical optical element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aspherical optical element comprising an aspherical resin molding layer and an element base material. Here, the "aspherical optical element" refers to, for example, an aspherical lens or a "blank of a reflecting mirror having an aspherical reflecting surface". When a reflective layer made of aluminum, silver or a multilayer optical thin film is formed on this blank, it becomes a reflecting mirror. An example of the element manufactured by the present invention is conventionally called a resin-bonded lens.

[0002]

2. Description of the Related Art Lenses used in optical products such as cameras and microscopes are mainly glass lenses. A glass lens is a glass block press-molded from molten glass (called a lens blank).
A lens having a desired curvature is manufactured by performing mechanical processing on the lens. A method of manufacturing a resin lens by a method such as press molding, injection molding, or casting using a resin instead of glass has been put into practical use. This method has a feature that the manufacturing cost is low because once a mold is manufactured, a large number of lenses can be mass-produced using the mold. But,
The resin lens has a fatal defect that its optical performance greatly changes due to changes in temperature and humidity, and is not used for precision lenses.

By the way, as the lens, there is an aspherical lens, and the surface shape is an aspherical surface. This aspherical surface is generally rotationally symmetrical about the optical axis. Aspherical lenses are widely used because they have excellent performance that cannot be obtained with spherical lenses. However, if an aspherical lens is manufactured in the same process as that for a spherical lens (grinding → polishing), it takes a lot of time and labor. Therefore, the manufacturing cost is considerably higher than that of the spherical lens.

In order to solve this drawback, resin-bonded aspherical lenses as shown in FIGS. 7 and 8 have been developed. This is composed of a thin (for example, 5 to 100 μm) resin molding layer 2 having an aspherical surface and a glass lens (element base material) 1 as a main component. The element substrate 1 is a spherical surface (FIG. 7: JP-A-60-56544).
No.) or a rough aspherical surface (see FIG. 8: JP-A-63-157103). Both are available at low manufacturing costs. Such a resin-bonded aspherical lens is manufactured, for example, by a manufacturing method including the following steps (a) and (b). See FIG. 9. (A) Mold 3 having an aspherical surface that is the opposite of the desired aspherical surface
(B) A predetermined amount of the radiation curable resin liquid 2 is placed in the center of the mold 3.
Step a in which a is hung (c) Step in which the glass lens 1 having a spherical surface or rough aspherical surface is placed on the mold 3 (d) The distance between the glass lens 1 and the mold 3 is brought close to a predetermined value (at this time, resin The liquid is spread to the outside of the effective diameter of the objective lens) Step (e) The resin liquid 2a sandwiched between the glass lens 1 and the mold 3 is irradiated with radiation 4 to be cured (f) ) A step of peeling the resin molding layer 2 obtained by curing from the interface with the mold 3.

[0005]

In the aspherical optical element as described above, when the thickness of the resin molding layer becomes thicker toward the outer peripheral portion in the vicinity of the effective diameter of the optical element (see FIG. 3), In some cases, it becomes thinner (see FIG. 4). By the way, in the conventional manufacturing method, when the resin liquid is irradiated with radiation to be cured, the resin layer may be separated from the mold or the base material (glass lens) during curing, or bubbles (air bubbles) may be formed on the outer peripheral portion of the resin molding layer.
Was involved. Therefore, in many cases, the shape accuracy of the surface (aspherical surface) of the resin molding layer 2 becomes low. In particular, when the resin molding layer has a shape that becomes thinner toward the outer peripheral portion of the effective diameter as shown in FIG. 4, such a phenomenon is likely to occur. Since a product having a low shape accuracy on the surface of the resin molding layer is a defective product, the conventional manufacturing method has a problem of a low yield rate. An object of the present invention is to improve the non-defective rate by reducing the cases where the shape accuracy is low.

[0006]

To achieve the above object, in the present invention, a resin liquid is sandwiched between a die having an aspherical surface that is the reverse of the desired aspherical surface and an element substrate, and the resin liquid is An aspherical optical element for obtaining an aspherical optical element by spreading to the outside of a desired region and then curing to form an aspherical resin molding layer, and peeling the aspherical resin molding layer from the interface with the mold In the manufacturing method, when curing the resin liquid, first,
Shield "outside of the desired area in the resin liquid"
Irradiate the resin liquid with radiation through the light shielding means, and then shield the resin liquid.
Radiates to the resin liquid including the part that was blocked by the light means
Irradiate a line.

[0007]

As a result of the earnest research conducted by the present inventors, when a notch is provided on the outer peripheral portion of the mold or the element substrate, the curing shrinkage of the liquid generated during the curing of the resin liquid causes the notched portion. It is found that the resin molding layer (liquid) does not separate from the mold or element base material during the curing and bubbles (air bubbles) are not entrained in the outer peripheral part of the resin molding layer because it is supplemented by the resin liquid stored in It was In the present invention, the position where the notch is provided is set on the outer peripheral portion of the mold or element base material that is outside the effective diameter of the desired aspherical optical element, thereby affecting the performance of the obtained optical element. I try not to give it. It should be noted that the notch may be provided on at least one of the mold and the element base material, but when it is provided on the element base material, it is necessary to perform the same treatment on each element base material of the aspherical optical element, which is troublesome. Therefore, it is preferable to provide it in the mold.

When the resin liquid is cured, first, the resin liquid is irradiated with radiation through a light shielding member that shields the cutout portion, and thereafter the resin including the portion shielded by the light shielding member is included. It is advisable to irradiate the liquid with radiation.
In this case, since the resin liquid accumulated in the cutout portion is in an uncured state at the time of the first irradiation, the resin is likely to move and the effect of replenishing the curing shrinkage of the resin liquid becomes more remarkable.

The element base material mainly used in the present invention is preferably made of glass, but may be made of resin in some cases. The shape may be set according to the target optical element, and may be a convex lens shape, a concave lens shape, a flat plate, or a rectangular parallelepiped. Generally, the substrate is a spherical lens made of glass. However, a glass lens having a rough aspherical surface may be used. The rough aspherical surface has a rougher processing accuracy than the desired processing accuracy or surface accuracy (for example, 6 μm or less or 3 μm or less) and has the same or approximate aspherical surface as the desired aspherical surface. Since such a glass lens may be rougher than a desired processing accuracy, it is an aspherical lens, but the manufacturing cost is not so high. The manufacturing method of such an aspherical lens is
It is already known and can be easily manufactured by a commercially available grinding machine.

In order to improve the adhesive force with the resin (layer), it is preferable that the glass element base material is previously subjected to silane coupling treatment. The thickness of the resin molding layer is generally 1 to 500 μm at the center, preferably 5 to 100 μm. The refractive index of the resin molding layer and the element base material do not necessarily have to be the same, except when the target element is molded into an aspherical surface with rough processing accuracy.

This resin molding layer is formed by curing a resin liquid. As the resin (liquid) used,
Examples include thermoplastic resins, radiation-curable resins (thermosetting resins), monomers and the like. As the thermoplastic resin, polymethylmethacrylate (acrylic resin), thermoplastic polyester, polyvinyl chloride, polystyrene, polycarbonate or the like can be used. In this case, the resin liquid which is heated and melted is sandwiched between the element base material and the mold, spread to the outside of a desired region, and then cooled and cured to obtain a resin molding layer.

Examples of the radiation curable resin include thermosetting resins such as epoxy resin, unsaturated polyester, polyurethane, ultraviolet curable resin and modified acrylic resin. These are kept in a liquid state and are sandwiched between the element base material and the mold to be spread to the outside of a desired region, and then irradiated with radiation to be cured to obtain a resin molding layer. As the radiation, for example, ultraviolet rays, electron beams, γ rays, α rays and the like are used. Further, when the resin is cured by simply heating, the mold and the element substrate may be cured by putting them in warm water.

Examples of the monomer include acrylates such as methyl methacrylate, ethylene methacrylate, methyl acrylate, ethyl acrylate and butyl acrylate, and ethylenically unsaturated monomers such as acrylic acid, styrene, butadiene and divinylbenzene. Examples of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[0014]

EXAMPLE FIG. 2 is a vertical sectional view of an aspherical lens (aspherical optical element) manufactured according to this example. This lens is composed of a glass lens 1 as an element base material and an aspherical resin molding layer 2 formed on the surface thereof. The glass lens 1 is a concave lens having a spherical surface and has a diameter of 27 mm,
The radius of curvature of the concave surface R ₁ is 11.170 mm and the radius of curvature of the convex surface R ₂ is 25.8
It was formed to have a thickness of 0 mm and a center thickness of 1.5 mm. In order to improve the adhesive force with the resin molding layer 2, the glass lens 1 is
The surface is previously subjected to silane coupling treatment.
Trade name KBM503 is used here as a silane coupling agent.
(Shin-Etsu Chemical Co., Ltd.) was diluted with a 2 wt% ethanol solution and used. The resin molding layer 2 is on the convex surface R ₂ side of the glass lens 1 and has a center thickness of about 30 μm. Further, the resin molding layer 2 is formed so as to become thinner toward the outer peripheral portion of the effective diameter of the aspherical lens, and the shapes of the lens 1 and the mold 3 are also molded in accordance therewith.

The mold used for manufacturing is made of a stainless steel alloy and has an aspherical surface with a radius of curvature of 28.8 mm on the side in contact with the resin. The surface of the mold is nickel plated. Also,
The mold 3 is provided with a cutout 3a (exaggerated in the drawing) on the outer peripheral portion outside the effective diameter of the aspherical lens to be manufactured. A urethane acrylate-based UV curable resin liquid was used as the resin liquid 2a (see FIG. 1) for forming the resin molding layer 2.

Mask 5 used for curing the resin liquid
Has an opening diameter of φ = 18 mm. This opening diameter is such that when ultraviolet rays are emitted from a point light source 110 mm away from the glass lens 1 and reach the resin liquid, the ultraviolet rays can irradiate a range slightly wider than a predetermined effective diameter (see FIG. 5). . Next, the manufacturing method of this embodiment will be described for each step with reference to FIG. (A) First step: an aspherical surface that is the inverse of the desired aspherical surface,
70 mg of the ultraviolet curable resin liquid 2a was dropped on the mold 3 having the notch 3a. Then, the glass lens 1 as the element base material is pressed against the resin liquid 2a, and the mold 3
While at least one of the glass lens 1 and the glass lens 1 is rotated about the optical axis of the aspherical lens as the rotation axis, the resin liquid 2a is sandwiched and the mold 3 and the glass lens 1 are formed so that the center thickness of the resin molding layer to be molded is 30 μm. Set the interval. As a result, the resin liquid 2a is in a state of spreading beyond the effective diameter of the target aspherical lens. (B) Second step: The mask 5 was placed on the glass lens 1, and the resin liquid 2a was irradiated with ultraviolet rays through the mask 5 and the glass lens 1. As the ultraviolet light source, a xenon lamp (point light source) with an output of 150 W (not shown) was used. This light source is installed 110 mm away from the glass lens 1. The irradiation intensity of ultraviolet rays is on the resin liquid 2a.
It was set to 30 mW / cm ² . The irradiation time of ultraviolet rays (time from the start to the end of irradiation) was about 30 seconds. At the time of irradiation, the outside of the effective diameter including the cutout 3a is shielded by the mask 5. The thickness of the resin liquid 2a at the boundary between the shaded portion and the non-shielded portion is about 50 μm, and the maximum thickness of the resin liquid 2a slightly inside the lens effective diameter is about 180 μm (see FIG. 6). . (C) Third step: The mask 5 was removed, and the entire resin liquid 2a was irradiated with ultraviolet rays for 30 seconds under the same conditions. As a result, the resin liquid 2a was cured and the aspherical resin molding layer 2 was formed. (D) Fourth step: mold the obtained aspherical resin molding layer 2 into a mold 3
By peeling from the interface with and, an aspherical lens as shown in FIG. 2 was obtained.

In the aspherical lens manufactured according to this embodiment, bubbles are not caught in the outer peripheral portion of the resin molding layer and the resin molding layer is not peeled off from the element base material, and the surface of the resin molding layer is desired. It became the shape accuracy. Further, when the resin liquid 2a is spread in the first step, at least one of the mold 3 and the glass lens 1 is rotated, so that the resin liquid 2a can be spread in a perfect circle. Therefore, the effect of improving the roundness of the resin molding layer 2 of the aspherical optical element can be obtained.

In this embodiment, the die 3 is provided with a notch, but the same effect can be obtained by using a notch on the outer peripheral portion of the glass lens 1 which is outside the effective diameter of the aspherical lens. You can Also, using a transparent mold 3,
Ultraviolet rays may be emitted from the mold 3 side. Further, the mask 5 may be formed by applying a masking paint on the glass lens 1 without using a separate member. Instead of the masking paint, a commonly used lens inner surface antireflection paint may be used. In these cases, in the third step, the point light source may be brought closer to the resin liquid 2a instead of removing the mask 5. By doing so, the irradiation range of the ultraviolet rays is expanded to the area shielded by the paint, so that the entire resin liquid is irradiated with the ultraviolet rays. Further, even when the mask 5 is used, the same effect can be obtained by bringing the point light source closer without removing the mask 5 in the third step. The manufacturing method of the present invention can also be applied to an aspherical lens in which the resin molding layer 82 is formed on both the convex surface side and the concave surface side of the base lens 81 as shown in FIG.

[0019]

According to the present invention, an aspherical resin molding layer and an element are formed.
When manufacturing an aspherical optical element composed of a child base material , entrapment of bubbles due to shrinkage during curing of the resin molding layer and peeling of the resin molding layer from the element base material do not occur. Therefore, the aspherical optical element can be manufactured without lowering the shape accuracy of the aspherical surface, and the yield rate of the product is improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing a vertical cross section of a lens or the like in each step of a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of a (resin-bonding type) aspherical lens manufactured in an example of the present invention.

FIG. 3 is a schematic view showing the thickness of the resin liquid (resin molding layer) in the radial direction of the base lens in the aspherical lens in which the resin liquid (resin molding layer) becomes thicker toward the outer peripheral portion of the effective diameter. is there.

FIG. 4 is a schematic diagram showing the thickness of the resin liquid (resin molding layer) in the radial direction of the base lens in the aspherical lens in which the resin liquid (resin molding layer) becomes thinner toward the outer periphery of the effective diameter. is there.

FIG. 5 is a schematic view showing an irradiation range of ultraviolet rays when the mask 5 is installed.

FIG. 6 is a schematic diagram showing the thickness of the resin liquid in the radial direction of the glass lens.

FIG. 7 is a schematic vertical sectional view of a conventional resin-bonded aspherical lens.

FIG. 8 is a schematic vertical sectional view of a conventional resin-bonded aspherical lens.

FIG. 9 is a schematic view showing a vertical cross section of a lens or the like in each step of a conventional manufacturing method.

FIG. 10 is a schematic vertical sectional view of a (resin-bonding type) aspherical lens.

[Explanation of symbols for main parts]

1 Glass lens or element substrate or substrate lens 2 Aspherical resin molding layer 2a Resin liquid (UV curable resin liquid) 3 mold 3a Notch 4 Radiation (ultraviolet rays) 5 Mask (light-shielding means)

Claims (4)

(57) [Claims] 1. An aspherical surface in which a resin liquid is sandwiched between a die having an aspherical surface opposite to a desired aspherical surface and an element substrate, and the resin liquid is spread to the outside of a desired region and then cured. to form a resin molding layer, by peeling off the non-spherical resin molded layer from the interface between the mold, in the manufacturing method of aspheric optical elements to obtain a non-spherical optical element, when curing the resin liquid, first , "In the resin liquid
Through the light shielding means for shielding the "outside of the desired area".
Irradiating the resin liquid with radiation, and then applying light to the light shielding means.
Radiation is applied to the resin liquid, including the part that was shielded from light.
A method for manufacturing an aspherical optical element, which comprises irradiating . 2. The method for manufacturing an aspherical optical element according to claim 1, wherein at least one of the mold and the element base material is provided with
A notch is provided on the outer periphery that is outside the effective diameter of the optical element.
A method of manufacturing an aspherical optical element, characterized by: 3. The aspherical surface according to claim 1 or 2.
In the method for manufacturing an optical element, the aspherical optical element has a resin thickness near the effective diameter on the outer peripheral portion.
Aspherical resin formed so that it becomes thinner as it goes
That it is an aspherical optical element consisting of a shaping layer and an element substrate,
A method of manufacturing a characteristic aspherical optical element. 4. Aspherical light according to any one of claims 1 to 3.
In the method for manufacturing an optical element, the radiation is an ultraviolet ray.
Method for manufacturing scientific elements.