JPS62240535A - Manufacture of optical element - Google Patents

Abstract

PURPOSE:To form an optical element with high accuracy by a method wherein the optical element is molded with a mold made of porous material and then the molded optical element is released from the mold by feeding gas to the interface between said mold and the optical element through the fine internal pores of the mold. CONSTITUTION:Raw material for an elastic body is poured through an inlet provided on a side mold 3 in a gap portion, which is shaped by a mold 2 (or a mold holder 1), the side mold 3 and a bottom plate 4, and then cured in order to form a columnar elastic body 5. When gas such as air or the like is poured under pressure through the gas inlet 1a of the mold holder 1, the gas passes from the bottom surface side of the mold 2 through the fine internal pores of the mold 2 made of porous material and reaches the interface between the mold 2 and the elastic body 2, resulting in releasing the elastic body from the mold in such state as to float the elastic body off the mold 2 (or in such a state that the lowering of molding accuracy is suppressed). A variable focus optical element 7 is obtained by arranging the elastic body, which is as released from the mold in the state of being tightly adhered to the circular bottom plate 4, in a cylindrical opening member 1 having a circular opening part 6a.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing optical elements such as lenses and prisms, and more specifically, the present invention relates to a method for manufacturing optical elements such as lenses and prisms. The present invention relates to a method for manufacturing an optical element that forms an optical element with excellent characteristics.

11. Methods for molding optical elements used in optical equipment, optical communications, electro-optics equipment, etc. usually include the glass molding method, which molds optical elements using molds, the plastic replica method, the injection method, Compression method etc. are used.

In order to obtain optical elements with excellent optical properties using these molding methods, it is important to improve molding accuracy in the optical element molding process, but at the same time, it is important to improve molding accuracy in the optical element mold release process. It is also extremely important to suppress the decline. If the molding precision in this mold release step is insufficiently maintained, it becomes difficult to obtain an optical element with high molding precision.

Glass has traditionally been used in the field of optical elements.

Methods for releasing a molded optical element made of resin etc. from a mold include a method of driving a 7-shaped square into the contact surface between the optical element and the mold, a method of driving the optical element into close contact with the mold using an air gun, etc. By blowing air onto the body to cool the adhered body, or by alternately immersing it in a heating water tank and a cooling water tank, the temperature of the adhered body is changed to change the expansion coefficient of the mold and the optical element. There are known methods of releasing from the mold by utilizing a difference in shrinkage rate, and methods of releasing by applying ultrasonic vibrations to the mold or optical element.

However, in the method of driving a 7-shaped blade into the contact surface between the mold and the optical element, there is a problem in that the optical properties of the optical element are significantly impaired because scratches are likely to occur on the surface of the mold or the optical surface of the elastic body. There is.

On the other hand, in the method of blowing air onto the mold and optical element in close contact with an air gun, the cooling efficiency is poor, so mold release tends to be incomplete. In the method of releasing from the mold through changes, not only is it necessary to repeatedly perform heating or cooling operations in order to provide a temperature difference that allows reliable release from the mold, but also:
Since deformation of the surface of the optical element due to thermal expansion or thermal contraction during heating or cooling is unavoidable, this method is particularly inappropriate as a mold release method for optical elements using materials that are susceptible to such thermal deformation.

Furthermore, in the method of mold release using ultrasonic vibration, it is necessary to repeatedly apply ultrasonic vibration to the mold or optical element before the # mold is confirmed, and repeated operations are required to ensure mold release. The disadvantage is that the number of repetitions tends to vary. In particular, when releasing an optical element made of an elastic body, ultrasonic vibrations are absorbed by the elastic body.
There is a problem that not only is the mold effect less likely to occur, but also that the temperature of the elastic body rises due to absorption of this ultrasonic vibration, making it easy to cause thermal deformation of the elastic body.

First, 1. The main object of the present invention is to eliminate the drawbacks of the above-mentioned mold release method, suppress the deterioration of molding accuracy during mold release, and reliably release the molded optical element from the mold. An object of the present invention is to provide a method for manufacturing an optical element that can form an optical element with high precision.

The optical element manufacturing method of the present invention was developed to achieve the above object, and uses a mold made of a porous material, and molds an optical element on the molding surface of the mold. and a step of releasing the optical element from the mold by supplying gas to the interface between the mold and the optical element through the internal micropores of the mold.

Further, an optical element manufacturing method according to another aspect of the present invention uses a mold made of a porous material and has a thin film coated on the molding surface thereof, and a step of releasing the optical element and the thin film from the mold by supplying gas to the interface between the mold and the thin film through the internal micropores of the mold. This is a characteristic feature.

In the mold release step of the manufacturing method of the present invention, gas is directly supplied to the interface (close contact surface) between the mold and the optical element through the internal micropores of the mold made of porous material, so the pressure of this gas is Based on this, a uniform release promoting force acts along the surface of the optical element, and the optical element is released from the mold on the contact surface in such a manner that it floats from the mold.

Therefore, according to the manufacturing method of the present invention, the mold release process can be carried out smoothly and reliably while minimizing the external force applied per unit area of the optical element surface (on the contact surface). It is now possible to minimize the deterioration in molding accuracy of optical elements during processing, and as a result,
An optical element with excellent optical properties formed with high precision can be obtained.

In the mold release process of the present invention, the mold release promoting force that acts uniformly along the contact surface can be directly applied to the surface of the optical element. Smooth and reliable mold release is possible. In particular, for optical elements made of elastic bodies, which have been difficult to release well using conventional methods, we can suppress deformation of the optical surface due to thermal expansion or contraction, absorption of ultrasonic vibrations, etc. The mold release process can be performed smoothly and reliably.

Hereinafter, the present invention will be explained in more detail with reference to the drawings as necessary. “%” indicates quantitative ratio in the following descriptions.
and 1 part" are based on heavy weight standards unless otherwise specified.

1 to 3 are schematic cross-sectional views in the thickness direction of an elastic body for explaining an embodiment of manufacturing a variable focus optical element made of an elastic body in the present invention.

Here, the variable focus optical element is composed of an elastic body and a relatively hard aperture member that has an aperture and contacts the elastic body, and is exposed through the aperture of the aperture member by deforming the elastic body. An optical element whose focal length can be varied by changing the shape of the optical surface (hereinafter referred to as "aperture surface") of an elastic body.

Referring to FIG. 1, it is made of metal, l1lIW, etc., and has a gas inlet 1a inside (centered on the optical axis).
A rotary mold fixing holder l is made of a porous material such as metal or glass, and a molding surface (elastic body contact surface) of a desired shape is attached.
This mold holder holds a cylindrical mold 2 having a
A cylindrical side mold 3 made of metal, resin, etc. is placed in contact with the outer peripheral surface of the mold 2, and a circular bottom plate 4 made of a transparent material such as glass, resin, etc. is placed at a constant distance from the mold 2.
to face each other.

In this way, the mold 2 (or mold holder 1) and the side mold 3
After injecting an elastic material such as silicone into the gap formed by the side mold 3 and the bottom plate 4 through an injection port (not shown) provided in the side mold 3, it is cured and the optical axis is centered. An elastic body 5 having a cylindrical shape is formed (casting method).

Next, when a pressurized gas such as air is injected through the gas inlet 1a of the mold holder 1, this gas flows into the mold made of porous material from the bottom surface of the mold 2 (the opposite side to the molding surface). It passes through the internal micropores in the mold 2 and reaches the interface (close contact surface) between the mold 2 and the elastic body 5, and on this close contact surface,
A *-type promoting force is generated that acts uniformly along the surface of the elastic body 5.

Based on this female mold promoting force, the elastic body 5 is released from the mold 2 made of a porous material by floating (with a reduction in molding accuracy being suppressed), but at this time, the mold holder
1 is also separated from the elastic body 5 at the same time.

After separating the side mold 3, the elastic body 5 released in this way is obtained in a state in close contact with the circular bottom plate 4 as shown in FIG. A cylindrical opening member 6 made of a relatively hard material such as metal or resin.
A variable focus optical element 7 is placed inside the optical element 7. In this optical element 7, the bottom plate 4 is provided so as to be movable in the direction along the optical axis with respect to the aperture member 6.

Although the outline of the optical element manufacturing method of the present invention is as described above, the method for molding the elastic body 5 includes, in addition to the above-mentioned casting method, molding methods known in the field of plastics such as injection method and combination method. can be used as well.

Next, the configuration of each part shown in one drawing will be explained.

As the porous material constituting the mold 2, for example, glass such as Vycor, sintered alumina, ceramics such as silicon carbide, polymers such as polysulfone, polypropylene, etc. are used, but the mold releasability with respect to the elastic body 5 is limited. These porous materials can be used as they are, or they can be made porous by forming micropores inside them through physical or chemical treatment. You may also use a quality one.

The mold 2 made of the porous material has a thickness along the optical axis of preferably 0.1 to 10 mm, more preferably 0.1 to 10 mm, although it depends on the mechanical strength of the material used as the mold. 1.
It is formed to have a diameter of 0 mm. Further, the opening pore diameter of the porous material on the molding surface of this mold 2 is 10 to 300.
About 0 people, more preferably about 10 to 300 people.

If the opening diameter exceeds 3,000, the problem of roughness of the optical surface of the elastic body 5 tends to occur.

The mold 2 formed in this way is manufactured using nitrogen gas (
When a pressure of 5 kg/cd higher than the molding surface side is applied to the bottom side (at the temperature at which the mold release operation is performed),
X 10” mol/(cnf e cm)Ig
It is preferable that the material exhibits a gas permeability of 5 in.e or more.

The size of the molding surface of the mold 2 (that is, the surface where the mold contacts the elastic body 5) is preferably approximately equal to or larger than the size of the opening surface 5a of the elastic body 5. The larger the size of the molding surface is, the more preferable it is from the viewpoint of applying a mold release promoting force as uniformly as possible along the optical surface (the surface facing the mold 2) of No. 5.

In the present invention, the gas supplied to the interface between the elastic body 5 and the mold 2 through the internal micropores of the mold 2 as described above is in a gaseous state at the temperature at which the mold release operation is performed (usually room temperature). Although any substance can be used without any particular limitation, it is preferable to use a gas (eg, air, nitrogen, etc.) that does not easily react chemically with the elastic body 5, mold 2, etc. at this temperature.

Such a gas is injected from the bottom surface (the surface opposite to the molding surface) of the mold 2 while being pressurized, and the pressure of the gas near the bottom surface is preferably about 1 to 20 kg/crt1.

Note that this gas can pass through the internal micropores of the mold 2 and be supplied to the interface between the mold 2 and the elastic body 5, so this gas can be supplied from the outer peripheral surface of the cylindrical mold y112. May be injected.

The side mold 3 that forms a gap for molding the elastic body 5 together with the mold 2, and the mold holder 1 that holds the mold 2 are made of materials such as metal and resin. It is preferable to be made of a material with good mold releasability (for example, a resin such as Teflon, a metal whose contact surface with the elastic body 5 is coated with a resin such as Teflon, etc.).

The material constituting the elastic body 5 is 80% at 350 nm.
It has a spectral transmittance of 92% or more in the 500-700 nm region, and an elastic modulus of 5 x 10" d y n e / c
m' or more and lXl0" dyne/Cm2 or less is preferably used. When using a plurality of materials having different elastic moduli selected from this range (for example, although not particularly shown, from the opening surface 5a side, the first elastic modulus is (When forming the elastic body 5 by laminating the body and the second elastic body), the ratio of the elastic modulus (El) of the first elastic body to the second elastic body (E2) (El
/E2) is 2 to 1 (although it varies depending on the thickness of each layer)
It is preferable to select within the range of oooo.

As such an elastic body, when the optical element obtained according to the present invention is used as a lens, it is preferable to use one that has poor transparency (at least to light of the wavelength used).

Specifically, the elastic material used in the present invention includes natural rubber and synthetic rubber, which are generally known as "rubber", such as styrene-butadiene rubber (SBR),
Butadiene rubber (BR), imprene rubber (iR), ethylene propylene rubber (EPM, EPDM), butyl rubber (iiR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), urethane rubber (U
), silicone rubber (Si), fluororubber (FPM),
Polysulfide rubber (T), polyether rubber (POR, CHR
, CHC), etc. are listed.

The elastic materials listed above are crosslinked if necessary; for example, by controlling the degree of crosslinking, the elastic modulus E can be changed. This crosslinking may be carried out using, for example, a crosslinking agent made of sulfur, peroxide, or the like.

In the present invention, various elastomers such as those described above are used as the material constituting the elastic body 5, but preferred mechanical properties (elastic modulus, etc.) or preferred optical properties (transparency, refractive index, etc.) can be easily achieved. From the point of view of obtaining silicone rubber (for example, KE10 manufactured by Shin-Etsu Chemical Co., Ltd.)
6. KEIO4GeJl, YE5 manufactured by Toshiba Series Corporation
822, YE5818), ethylene-propylene rubber, etc. are particularly preferred.

The elastic body 5 made of the above-mentioned elastic material has a thickness of preferably 0.5 to 50 Omm (depending on the elastic modulus E), preferably 1. 0-3
0.0s+s Referring to FIG. 3, the opening member 6 that accommodates the above-mentioned elastic body 5 is made of a relatively hard material such as metal, glass, or resin, and preferably has a thickness of 0.1 to 0.0s+s.
It is formed by forming a plate of about 10° Ova into a cylindrical shape having a circular opening 6a.

This opening member 6 is preferably made of an opaque material.

The circular bottom plate 4, which holds the elastic body 5 together with the above-mentioned opening member 6, is made of a transparent and relatively hard material such as glass or resin, and preferably has a thickness of about 0.1 to 5.0 mm.

The optical element 7 includes an elastic body 5 as described above and an aperture member 6.
and a bottom plate 4, and the entire optical element 7 is formed in a cylindrical shape as shown in FIG. The rectangular aperture surface of such an optical element, which may be constructed using a rectangular parallelepiped aperture member, can be used as a cylindrical lens, a toric lens, or the like.

It is also possible to use the opening surface 5a of the elastic body 5 as a reflecting surface by a method such as attaching metal to the opening surface 5a. In such an embodiment, the material constituting the elastic body does not need to be transparent, and a filler such as metal powder may be dispersed in the elastic body.

Next, a method of using the optical element 7 obtained by the manufacturing method of the present invention will be described.

Referring to FIG. 3, in the optical element 7, when pressure is applied to the bottom plate 4 from below in the drawing to deform the elastic body 5 under pressure, the opening of the elastic body 5 is surface 5
a can reversibly change the convex lens shape of the aperture surface 5a by controlling the magnitude of the pressure applied to the elastic body 5 protruding from the aperture 6a of the aperture member 6 in the shape of a convex lens. , a desired focal length can be obtained using this optical element 7.

On the other hand, when negative pressure is applied to the elastic body 5, contrary to the above, the opening surface 5a of the elastic body 5 gives a reversibly changeable concave lens shape (not shown).

As described above, how the opening surface 5a of the elastic body 5 changes when the elastic body 5 is deformed can be easily analyzed using, for example, a structural analysis program based on the finite element method.

In the above, an embodiment of the present invention has been described in which gas is directly injected into the surface of the elastic body 5 facing the mold 2 (close contact surface) through the mold 2 made of a porous material. It is also possible to do something like the one shown in Figure 4.

If the thin W18 is interposed as shown in FIG. 4, when the opening hole diameter on the molding surface of the mold 2 is relatively large (for example, even if the opening hole diameter is too Å or more, but preferably several tens to hundreds). Also, the effect of FillQ8 has the advantage that the roughness of the optical surface of the elastic body 1 can be maintained within a preferable range from the viewpoint of optical accuracy.

In this embodiment in which the thin film 8 is interposed, the mold may be released by injecting a gas such as air under pressure from the bottom side of the mold 2, as in the case shown in FIG. A suction means (not shown) is connected to the gas inlet la of the holder l, and the thin film 8 coated on the molding surface of the mold 2 is
After molding the elastic body 5 while applying negative pressure to (that is, reducing the pressure on the bottom side of the mold 2), the application of negative pressure to the thin film 8 is released to return it to normal pressure (or the gas is released). It is preferable to perform the mold release operation by applying slight pressure and injecting from the bottom side of the mold 2.

Like this fil! 8. (At this time, the pressure of the gas in the direction from the mold 2 toward the elastic body 5 should be lower than when molding the elastic body 5, as in the case of pressurized gas injection in FIG. When performing a mold release operation due to a relative increase in pressure, the thin film 8 itself undergoes spontaneous deformation due to its restoring force after the negative pressure is released, or the release effect of the thin film 8 on the elastic body 5 (relatively increases in gas pressure). This is preferable from the standpoint of releasing the elastic body 5 from the mold 2 more smoothly.

The thickness of this thin film 8 is about 0.1 pm to several tens of pm, and furthermore, the thickness is about 5.5 pm. The thickness of this thin film 8 is preferably thin as long as it has the necessary strength, which is preferably less than OILm.

Full! As the material constituting J8, it is preferable to use a material that has good releasability from the elastic body 51. For example,
Films made of polymers such as polyethylene, polyimide, polyacrylonitrile, and vinylidene chloride are preferably used.

It is more preferable that the surface of these films in contact with the elastic body 5 is subjected to a treatment (for example, corona discharge, glow discharge, surface treatment with S/base, etc.) to increase the releasability from the elastic body.

In the above, an embodiment of the present invention for manufacturing a variable focus optical element made of an elastic body has been described. However, according to the manufacturing method of the present invention, mold release that acts uniformly along the contact surface between the mold and the optical element By using the accelerating force, it is possible to suppress the deterioration in molding accuracy of optical elements during mold release without selecting the type of optical element material, so it is possible to suitably obtain general optical elements that are molded using molds. can.

As described above, according to the present invention, a mold made of a porous material and an optical element (or a thin film interposed between them)
There is provided a method for manufacturing an optical element, which includes a step of releasing the optical element from the mold so as to float the optical element by relatively increasing the pressure of the gas supplied to the surface in close contact with the mold.

According to the manufacturing method of the present invention, a deterioration in the molding accuracy of the optical element during mold release is suppressed based on the mold release promoting force that acts uniformly along the contact surface between the mold and the optical element (or the above-mentioned thin film). At the same time, since the mold release process is performed smoothly and reliably with - times of mold release operations, an optical element molded with high precision and excellent in optical properties can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Referring to FIG. 5, a rotary mold fixing holder l (made of stainless steel, outer diameter 25 mm on the side opposite the elastic body 5), which has a gas inlet 1a inside, has a porous hole. A cylindrical mold 2 (bottom diameter: 20 layers φ) made of quality material Corning Vycor Glass 7930 (approx. 40 holes, manufactured by Corning) and whose molding surface is a concave spherical surface with a radius of curvature of 50 layers is glued. and these were integrally formed. At this time, a gap portion tb was provided on the bottom surface (the surface opposite to the molding surface) of the mold 2 to allow gas to flow therethrough.

A circular bottom plate 4 (thickness: 5.0
A cylindrical side mold 3 (inner diameter 251 mφ) made of Teflon was placed in contact with the outer circumferential surface of the mold holder l. This side mold 3 is configured to be divisible using cylindrical Teflon frames 3a and 3b, and this Teflon frame 3a
, which can be divided into three parts along its outer circumference.
I used the ``split frame''. In addition, the glass bottom plate 4 is a Teflon frame 3
A and a belt (not shown) made of rubber having a high elastic modulus were used to tightly fix it in the vertical direction of the drawing.

Molding mold 2 (or mold holder 1) arranged in this way
Then, through the raw material injection port 9 provided in the Teflon frame 3a of the side mold 3 into the gap between the glass bottom plate 4 and the side mold 3,
Elastic material raw material (silicone rubber KE10 manufactured by Shin-Etsu Chemical Co., Ltd.)
4Gel, 10 parts by weight, and the company's curing catalyst Cataly.
After injecting a mixture of stl O4 and 1-fold fi part, the elastic body raw material was left to stand in a constant temperature bath at 80° C. for about 4 hours to harden the elastic body raw material, thereby forming a cylindrical elastic body 5.

Next, by injecting air (pressure cuff Kg/ard) from the gas inlet 1a of the mold holder 1, the mold 2 and the elasticity after hardening are Air was supplied to the interface (close contact surface) with the body 5, and the elastic body 5 was released from the mold 2 so as to float therefrom. During this mold release, the stainless steel holder l and the Teflon frame 3b are separated from the elastic body 5 together with the mold 2, while the Teflon (three-part) frame 3a and the bottom plate 4 are in close contact with the elastic body 5. It was released from the mold so that it remained intact.

Furthermore, by dividing the Teflon frame 3a into three parts and separating them from the elastic body 5, the elastic body 5 having a highly precise optical surface is integrated with the glass bottom plate 4 as shown in FIG. (A cylindrical shape having a diameter of 25 mmφ on the surface facing the glass bottom plate 4 and a thickness of 10.0 layers along the optical axis) was obtained.

The elastic body 5 and the bottom plate 4 were housed in an opening member 6 having an opening 6a with an inner diameter of 20 mmφ, as shown in FIG. 3, to obtain a variable focus optical element 7.

When the optical element 7 thus obtained was deformed in the direction of pressurizing the elastic body 5 by applying an external force to the vicinity of the outer periphery of the glass bottom plate 4 (the area through which the light rays do not pass) from below one drawing, it was found that the magnitude of this external force was Opening surface 5a of elastic body 5 depending on the
The radius of curvature of could be continuously and reversibly changed from 50 mm (initial value) to 30 mm.

For details of the operation of such optical element 7,
The applicant's previous application (Japanese Unexamined Patent Publication No. 60-84502,
JP-A-60-111201, etc.) can be referred to.

[Brief explanation of drawings]

1 to 5 are schematic cross-sectional views of one elastic layer viewed in the thickness direction for explaining one embodiment of the optical element manufacturing method of the present invention. l... Molding mold fixing holder la... Gas inlet 2... Molding mold 3 made of porous material... Side mold 4... Bottom plate 5... Elastic body 5a... Opening surface 6...Aperture member 7...Optical element 8...Thin film 9...Raw material injection port illusion J: Fig. 1

Claims (1)

[Claims] 1. A process of molding an optical element on the molding surface of the mold using a mold made of a porous material, and a process of forming the optical element between the mold and the optical element through the internal micropores of the mold. 1. A method for manufacturing an optical element, comprising a step of releasing the optical element from a mold by supplying gas to the interface. 2. The process of molding an optical element on the thin film coated on the molding surface of the mold using a mold made of a porous material and having a thin film coated on the molding surface, and the process of molding the inside of the mold. A method for manufacturing an optical element, comprising the step of supplying gas to the interface between the mold and the thin film through the micropores, and releasing the optical element together with the thin film from the mold.