JPH08217472A - Method for forming optical element - Google Patents

Abstract

PURPOSE: To form a glass optical element with a high accuracy without any shrink. CONSTITUTION: The central parts 1a and 2a on recessed forming surfaces of a glass material are cooled by blowing cooling gases 4a and 4b from the surface side of forming surfaces just before press forming the glass in thermally softening the glass material, then conveying the glass material between a pair of a top force 1 and a bottom force 2 having each recessed forming surface and press forming the optical element in a protruding shape. Thereby, a temperature distribution so as to raise the temperature toward the central parts of the forming surfaces for press forming the thick wall parts of the glass material is produced in the forming surfaces. Furthermore, the outer peripheral parts of the forming surfaces are cooled in press forming the optical element of a recessed shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an optical element in which an optical material such as glass is softened by heating and then pressure-molded to obtain an optical element.

[0002]

2. Description of the Related Art Conventionally, in a method of press-molding an optical element with a molding die after heating and softening a glass material, a pair of molding metals having a molding surface corresponding to a desired optical element shape is used. The mold is used.

Japanese Patent Publication No. 4-20855 discloses a method in which one molding die is divided into ring-shaped zones and the optical elements are press-molded while separately setting the temperatures of the divided zones.

Further, Japanese Patent Laid-Open No. 2-133325 discloses a method of heating and softening a glass material so that a thin portion of the glass material is heated to a temperature higher than a temperature of a thick portion of the glass material. .

Further, in JP-A-5-24858, a glass in a heat-softened state is attached on a lower mold, a heating member having a shape in which the upper surface of the glass material is inverted is brought close to the glass material, and heating is performed from the heating member. Gas is blown onto the upper surface of the glass material to heat it, and molding is performed while delaying the solidification of the thin portion of the glass material. Then, after that, the heating member is retracted to replace the upper mold, and the upper mold is pressed against the upper surface of the glass material to perform press molding.

[0006]

[Problems to be Solved by the Invention] However, Japanese Patent Publication No. 4-2
In 0855, since the molding die is divided, a dividing line is generated on the surface of the molded optical element, and if this dividing line is located on the optical function surface, post-processing such as polishing is required. Become. In order to eliminate the need for post-processing, the dividing line must not be located on the optical functional surface, and therefore cannot be used if the optical functional surface of the optical element is equal to or close to the outer diameter of the optical element. I have

Further, in JP-A-2-133325, in order to provide a temperature difference in the glass material, a heating heater is brought close to the temperature difference to provide a temperature difference. However, in reality, a thin portion of the glass material is heated. Therefore, the thin part of the glass that has a small heat capacity will quickly cool down,
It has a drawback that the effect of providing a temperature difference in the glass material by the heater cannot be obtained so much.

Further, in JP-A-5-24858, since a large pressure cannot be applied when the upper surface of the glass material is not in contact with the heating member, almost no molding is possible, and the upper surface is replaced with an upper mold for press molding. In this case, as mentioned above, the thin portion of the glass has a small heat capacity, so that the glass is immediately cooled and the effect of heating the thin portion of the glass material cannot be obtained so much.

The present invention has been made in view of the above problems of the prior art, and the invention of claim 1 is a method of molding an optical element capable of obtaining a glass optical element having a highly accurate convex shape without sink marks. The purpose is to provide.

It is an object of the invention of claim 2 to provide a method of molding an optical element capable of obtaining a glass optical element having a highly accurate concave shape without sink marks.

A third aspect of the present invention is, in the first and second aspects, an object of the present invention is to provide a cooling means for molding a glass optical element.

[0012]

In order to solve the above-mentioned problems, the invention of claim 1 is characterized in that after the glass material is softened by heating,
In a method of molding an optical element that conveys between a pair of molds having a concave molding surface and press-molds a convex optical element, the center of the concave molding surface is formed on the surface of the molding surface immediately before pressing the glass material. It was configured to be cooled from the side and to have a temperature distribution on the molding surface.

Further, the invention of claim 2 is a method for molding an optical element, in which a glass material is heated and softened and then conveyed between a pair of molding dies having a convex molding surface to press-mold a concave optical element. In the above, the outer peripheral portion of the convex molding surface was cooled from the surface side of the molding surface immediately before press molding the glass material, and the temperature distribution was provided on the molding surface.

Further, the invention of claim 3 relates to claims 1 and 2.
In the method of molding an optical element, when cooling the molding surface, a cooling gas is blown onto the surface of the molding surface, or a cooling member cooled by the cooling gas is brought into contact with the molding surface to provide a temperature distribution. Configured.

[0015]

According to the structure of claim 1, the central portion of the concave molding surface is cooled from the molding surface side of the mold immediately before the pressure molding of the glass material, and the temperature is increased toward the outer peripheral portion of the molding surface. A temperature distribution occurs.

According to the structure of claim 2, the outer peripheral portion of the convex molding surface is cooled from the molding surface side of the mold immediately before the pressure molding of the glass material, and the molding surface is heated toward the central portion. Temperature distribution occurs.

According to the structure of claim 3, cooling gas is blown to the molding surface from the molding surface side of the mold, or a member cooled by the cooling gas is brought into contact with the molding surface,
Temperature distribution occurs on the molding surface.

That is, a temperature distribution can be formed on the molding surface by spraying a cooling gas on a part of the molding surface or by bringing a member cooled by the cooling gas into contact with the molding surface. This temperature distribution shows that when molding a convex lens, the molding surface is concave, so the temperature at the center of the molding surface is lower than the outer peripheral portion, and when molding a concave lens, the mold molding surface is convex, so The temperature is lower than the center. Therefore, if the heat-softened glass material is sandwiched between a pair of molds and pressure-molded while the temperature distribution is formed in the mold, the part corresponding to the thick part of the glass material (the center part of the convex lens, the concave lens Since the temperature of the molding surface is relatively low, the outer peripheral part is cooled quickly, so there is no temperature difference between the thin and thick parts of the glass molding material, and there is no thermal damage part, and the lens that has been molded is completed. No sink marks occur.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. In this embodiment, a convex lens is molded.
FIG. 1 is a cross-sectional view showing a step of producing a temperature distribution on a forming surface in the present embodiment, FIG. 2 is a cross-sectional view showing a pressure forming step of a glass material after producing a temperature distribution on a forming surface, and FIG. 3 is a glass. It is a figure showing the temperature change in the cooling process after the press molding of the material.

First, the molding apparatus used in this embodiment will be described. As shown in FIG. 1, an upper mold 1 having a cylindrical shape and a concave molding surface formed on a tip end surface thereof is fixedly mounted on a fixing member (not shown) equipped with a heating means of the upper mold 1 provided in a molding apparatus. ing. A lower mold 2 having a concave molding surface formed on a tip end surface facing the molding surface of the upper mold 1 is coaxially arranged at a lower position facing the molding surface of the upper mold 1. It is provided so as to be vertically movable by being connected to a driving means (not shown) equipped with the heating means.

Between the molding surface of the upper mold 1 and the molding surface of the lower mold 2, a cooling gas supply pipe 3 connected to a cooling gas supply device (not shown) is connected to a driving device (not shown). It is provided so that you can move in and out. Holes 3a and 3b are provided at the tip of the cooling gas supply pipe 3 toward the center of the molding surfaces of the upper mold 1 and the lower mold 2, and the holes 3a and 3b are supplied from the cooling gas supply device to pass through the cooling gas supply pipe 3. Through holes 3a, 3
The cooling gas 4a, 4b discharged from b is blown to the molding surface center 1a of the upper mold 1 and the molding surface center portion 2a of the lower mold 2, respectively. That is, the temperature of each molding surface of the upper and lower molds 1 and 2 is lowered by the discharge of the cooling gas 4a and 4b, and the temperature of the molding surface center portions 1a and 2a becomes the lowest temperature. It produces a wide temperature distribution.

Next, the structure in the press which is a step after the temperature distribution is generated will be described with reference to the sectional view of FIG. Between the molding surfaces of the upper mold 1 and the lower mold 2, a glass material 6 press-molded is placed and disposed in a donut-shaped holder 5. That is, the step 5a formed inside the inner diameter of the holder 5 outside the molding apparatus.
A desired shape that is conveyed by a holder conveying arm (not shown) on which a holder 5 having an optical material 6 to be formed thereon is placed and can be formed by a heating means (not shown) which is a pre-step of forming. Is heated and softened to the heating temperature of, and heated to near the transition point temperature of the glass material 6 to be molded in advance, and is conveyed between the upper mold 1 and the lower mold 2 having the temperature distribution on the molding surface, It is configured to be press molded.

Next, a method of molding the optical element of this embodiment will be described. The cooling gas supply pipe 3 is advanced by a drive device (not shown), and the tip end portion of the cooling gas supply pipe 3 is inserted and arranged between the molding surfaces of the upper mold 1 and the lower mold 2, and then the cooling gas supply pipe 3 is moved. Hole 3 at the tip
Cooling gas 4 supplied from a and 3b by a cooling gas supply device (not shown) and passing through the cooling gas supply pipe 3.
a and 4b are the center parts 1 of the molding surfaces of the upper mold 1 and the lower mold 2, respectively.
It discharges toward a and 2a. Then, the temperature of the molding surfaces of the upper mold 1 and the lower mold 2 decreases around the molding surface center portions 1a and 2a, and a temperature distribution is generated. Immediately after the cooling gas supply pipe 3 is withdrawn from between the molding surfaces, the cooling gas supply pipe 3 is molded by the heating means (not shown) in the state of being mounted in the holder 5 previously mounted on the holder carrying arm (not shown). The glass material 6 heat-softened to a possible state is the upper mold 1 and the lower mold 2.
It is conveyed between the molding surfaces of.

Next, the lower mold 2 is moved upward by the lower mold driving means located below the holder 5 and the glass material 6 being conveyed, and the lower mold 2 is provided on the outer peripheral edge of the lower mold 2 and the lower surface of the holder 6. Then, the holder 5 and the glass material 6 are lifted from the holder transporting arm and separated from each other. Then, the upper end surface of the glass material 6 separated from the holder carrying arm contacts the molding surface of the upper mold 1, and the upper and lower surfaces of the glass material 6 are pressed by the molding surfaces of the upper and lower molds 1 and 2.

Due to the temperature distribution of the upper die 1 and the lower die 2, the glass material 6 to be press-molded has a temperature difference between the central portion corresponding to the thick wall and the peripheral portion corresponding to the thin wall as shown in FIG. Is cooled evenly without spreading.

Thereafter, the optical element molded by lowering the lower mold 2 is placed on the holder carrying arm together with the holder 5 and carried out to the outside to be taken out, thus completing the molding.

According to the molding method of this embodiment, the temperature of the central portion for molding the thick portion having the slow cooling rate is low, and the temperature of the peripheral portion for molding the thin portion having the fast cooling rate is high. Cooling gas 4 discharged from cooling gas supply pipe 3
Since a temperature distribution is generated on the molding surfaces of the upper mold 1 and the lower mold 2 by means of a and 4b, as shown in FIG. 3, the temperature difference between the thick and thin portions of the glass material 6 is reduced during press molding. Therefore, it is possible to obtain an optical element free from sink marks and distortion due to the difference in shrinkage amount. Further, since the temperature distribution is generated in the upper mold 1 and the lower mold 2 having a large heat capacity, the glass material 6 is removed after the cooling gas supply pipe 3 is withdrawn from between the molding surfaces.
The temperature distribution generated on the molding surface is not eliminated during the transportation of the resin between the molding surfaces.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a cross-sectional view showing a step of producing a temperature distribution on the molding surface in this embodiment, FIG. 5 is a cross-sectional view showing a cooling member on the molding surface, and FIG. 6 is a glass after the temperature distribution is generated on the molding surface. FIG. 7 is a cross-sectional view showing the pressure molding step of the material, and FIG. 7 is a diagram showing the temperature change in the cooling step after the glass material is pressure molded. In the drawings, the same members, shapes and configurations as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The present embodiment is an example of molding a concave lens. Each of the upper mold 11 and the lower mold 12 used in this embodiment is provided with a convex molding surface on its tip surface. Further, the tip of the cooling gas supply pipe 13 is formed in a ring shape, and the ring-shaped portion is provided with a plurality of holes 13a, 13b in the vertical direction as shown in FIG. 5, and the holes 13a, 13b. As a result, the cooling gases 4a and 4b are discharged toward the molding surface outer peripheral portion 11a of the upper mold 11 and the molding surface outer peripheral portion 12a of the lower mold 12, respectively. That is, the temperatures of the molding surface of the upper mold 11 and the molding surface of the lower mold 12 are lowered by the discharge of the cooling gases 4a and 4b, respectively.
It is configured such that temperature distribution occurs concentrically around the center of the molding surface in the lowest temperature at the molding surface outer peripheral portions 11a and 12a. Other configurations are the same as those in the first embodiment.

Next, a method of molding the optical element of Example 2 of the present invention will be described. The cooling gas supply pipe 13 is advanced by a driving device (not shown), and the ring-shaped tip of the cooling gas supply pipe 13 is inserted and arranged between the molding surfaces of the upper mold 11 and the lower mold 12, and then the cooling gas supply pipe 13 is inserted. Cooling gas 4a, 4b supplied from a cooling gas supply device (not shown) and passing through the cooling gas supply pipe 13 through a plurality of holes 13a, 13b provided at the tip of the upper and lower molds 12, 13 respectively. Molding surface outer peripheral portions 11a, 12a
Discharge toward. Then, the temperature of the molding surfaces of the upper mold 11 and the lower mold 12 decreases from the molding surface outer peripheral portions 11a and 12a, and a concentric temperature distribution centering on the centers of the upper and lower molds 11 and 12 is generated. Immediately after the cooling gas supply pipe 13 is withdrawn from between the molding surfaces, the cooling gas supply pipe 13 is mounted in the holder 5 previously mounted on the holder transfer arm (not shown) and molded by the heating means (not shown). The glass material 6 heat-softened to a possible state is the upper mold 11 and the lower mold 12.
It is conveyed between the molding surfaces of.

Due to the temperature distribution of the upper mold 11 and the lower mold 12, the press-molded glass material 6 has, as shown in FIG. 7, an outer peripheral portion corresponding to a thick wall and a central portion corresponding to a thin wall,
The temperature difference does not spread and it is cooled evenly. Other molding methods are the same as in Example 1.

According to the forming method of this embodiment, the temperature of the outer peripheral portion forming the thick portion of the glass material 6 having a low cooling rate is low, and the central portion forming the thin portion of the glass material 6 having a high cooling rate. So that the temperature of the upper mold 11 is increased by the cooling gases 4a and 4b discharged from the cooling gas supply pipe 13.
Since a temperature distribution is generated on the molding surface of the lower mold 12, the temperature difference between the thick portion and the thin portion of the glass material 6 can be reduced during press molding as shown in FIG.
An optical element free from sink marks and distortion due to the difference in shrinkage amount can be obtained.
Further, since the temperature distribution is generated in the upper mold 11 and the lower mold 12 having a large heat capacity, after the cooling gas supply pipe 13 is withdrawn from between the molding surfaces, the glass material 6 is conveyed between the molding surfaces. The temperature distribution generated on the molding surface is not eliminated.

[Third Embodiment] A third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a sectional view showing a step of producing a temperature distribution on a molding surface when molding a convex lens, FIG. 9 is a sectional view showing a step of producing a temperature distribution on a molding surface when molding a concave lens, and FIG. 10 is a concave lens. FIG. 6 is a cross-sectional view showing a cooling member of a molding surface for molding the.

In this embodiment, the cooling members 21 and 22 in which the cooling gas supply pipes 3 and 13 shown in Embodiments 1 and 2 are inserted and arranged are used. The cooling members 21 and 22 are used.
2 includes contact portions 21a and 22a capable of contacting the molding surface.
Are formed. That is, as shown in FIG. 8, the cooling member 21 used when molding the convex lens has a concave surface 2
The tip end portion is bent in the molding surface direction so that it can come into contact with the center of the molding surface, and a contact portion 21a is provided. In addition, as shown in FIGS. 9 and 10, the cooling member 22 used when molding the concave lens has a cylindrical shape with its tip end facing the molding surface direction so as to be able to contact the outer peripheral surface of the molding surface of the convex mold 26. Is provided with a contact portion 22a. This cooling member 21,2
2 is provided by a drive device (not shown) so that it can come into contact with and separate from the molding surfaces of the molds 25 and 26, and can move in and out between the molding surfaces.
Cooling gas 23, 24 can flow in via a cooling gas supply device (not shown) through the contact portion 21.
When a contacts the molding surface, the center of the molding surface of the concave die 25 is cooled, and when the contact portion 22a contacts the molding surface, the outer periphery of the molding surface of the convex die 26 is cooled. It is configured to generate a distribution. Other configurations are the same as those of the first and second embodiments.

A method of molding the optical element of the present invention will be described.
Cooling gas supply pipes 3, 13 shown in the above Examples 1 and 2
After the cooling members 21 and 22 inside of which are inserted and arranged between the molding surfaces, the contact portions 21a and 22a cooled by the cooling gas 23 and 24 are brought into contact with the molding surface. As a result, the portion of the die forming surface for forming the thick portion of the glass material is cooled, and the same temperature distribution as that of the first and second embodiments is generated on each of the forming surfaces of the concave die 25 and the convex die 26. The other method is the same as in the first and second embodiments.

According to this embodiment, the same as in Embodiments 1 and 2, but the cooling members 21 and 22 are brought into direct contact with the molding surface, so that even finer parts can be cooled efficiently.

[0037]

As described above, according to the method of molding an optical element of the present invention, the following effects can be obtained. According to the invention of claim 1, since the central portion of the concave molding surface is cooled to generate the temperature distribution on the molding surface, when the convex lens is press-molded, the thick portion at the center of the glass material and the thin wall at the outer periphery are formed. Since the temperature difference between the portions can be reduced, it is possible to form a convex optical element that is free from sink marks and distortion due to the difference in shrinkage amount.

According to the second aspect of the present invention, since the outer peripheral portion of the convex molding surface is cooled to generate the temperature distribution on the molding surface, when the concave lens is press-molded, the thin wall portion at the center of the glass material Since it is possible to reduce the temperature difference in the thick portion on the outer periphery, it is possible to mold a concave optical element that is free from sink marks and distortion due to the difference in shrinkage amount.

According to the third aspect of the invention, the temperature distribution can be surely provided on the molding surface by blowing the cooling gas or bringing the cooling member into contact.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of producing a temperature distribution on a molding surface in Example 1 of the present invention.

FIG. 2 is a cross-sectional view showing the pressure molding step of the glass material after the temperature distribution is generated on the molding surface in Example 1 of the present invention.

FIG. 3 is a diagram showing a temperature change in a cooling step after the glass material is press-molded in Example 1 of the present invention.

FIG. 4 is a cross-sectional view showing a step of producing a temperature distribution on a molding surface in Example 2 of the present invention.

5 is a cross-sectional view showing a cooling member taken along line AA in FIG.

FIG. 6 is a cross-sectional view showing a pressure molding step of a glass material after a temperature distribution is generated on a molding surface in Example 2 of the present invention.

FIG. 7 is a diagram showing a temperature change in a cooling step after the glass material is press-molded in Example 2 of the present invention.

FIG. 8 is a cross-sectional view showing a step of producing a temperature distribution on a molding surface when molding a convex lens in Example 3 of the present invention.

FIG. 9 is a cross-sectional view showing a step of producing a temperature distribution on the molding surface when molding a concave lens in Example 3 of the present invention.

10 is a cross-sectional view showing the cooling member taken along line BB in FIG.

[Explanation of symbols]

 1 Upper Mold 1a Center of Molding Surface 2 Lower Mold 2a Center of Molding Surface 3 Cooling Gas Supply Pipes 4a, 4b Cooling Gas 11 Upper Mold 11a Molding Surface Outer Part 12 Lower Mold 12a Molding Surface Outer Part 13 Cooling Gas Supply Pipes 21 and 22 Cooling members 23 and 24 Cooling gas 25 Concave type 26 Convex type

Claims (3)

[Claims] 1. A glass material is press-molded in a method of molding an optical element, which comprises heating and softening a glass material, and then conveying it between a pair of molds having a concave molding surface to press-mold a convex optical element. A method of molding an optical element, characterized in that the central part of the concave molding surface is cooled immediately before from the surface side of the molding surface to provide a temperature distribution on the molding surface. 2. A glass material is press-molded in a method of molding an optical element, which comprises heating and softening a glass material, and then conveying the glass material between a pair of molds having a convex molding surface to press-mold a concave optical element. Immediately before the cooling, the outer peripheral portion of the convex molding surface is cooled from the surface side of the molding surface to provide a temperature distribution on the molding surface. 3. When cooling the molding surface, a cooling gas is blown to the surface of the molding surface, or a cooling member cooled by the cooling gas is brought into contact with the molding surface to provide a temperature distribution on the molding surface. 1. The method for molding an optical element according to 1, 2.