JPH06345464A - Mold for optical element molding, production thereof and method of molding optical element - Google Patents

Abstract

PURPOSE:To provide optical elements of uniform optical performance with reduced fluctuation pressing a mold which can be readily transferred and set for press molding. CONSTITUTION:The top force 10B and the bottom force 10A are provided with the cylinder or column part having the molding face processed into a specified shape and the collar connecting to the end face opposing to the molding face of the cylinder or column for forming the optical face of the optical elements mainly comprising a glass material. The top force 10B and the bottom force 10A are arranged in the trunk force 22 so that they are freely slidable and the material for an optical element is placed in the space surrounded with the top and bottom forces and the trunk force. Then, the top force 10B is allowed to go down to press the material 1 whereby the optical element is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inexpensive optical element molding die having excellent shape accuracy and surface accuracy, a method of manufacturing the same, and a method of manufacturing an optical element.

[0002]

2. Description of the Related Art Conventionally, when an optical element is manufactured by press molding, an optical material to be molded is preheated to its softening temperature. A method of press-molding the preheated optical material, supplying it between an upper mold and a lower mold that are processed to have the same shape as the surface of a predetermined optical element, and pressing at a predetermined temperature and pressure. Was common.

A molding die for press-molding such an optical element has been manufactured by highly accurately grinding a superhard metal material having excellent heat resistance and corrosion resistance with an ultraprecision lathe. However, such a precision grinding process requires a long machining time, and the grindstone wears during the machining, and the grindstone must be replaced during the machining.There are many problems in mass-producing high-precision molds. there were.

Therefore, a method of using glass as a molding die material and manufacturing a glass molding die by press molding (for example, Japanese Patent Laid-Open No. 64-33022) has attracted attention. A conventional glass mold will be described below with reference to the drawings. FIG. 6 shows a structure of a molding die for making an optical element molding die. As shown in the figure, a glass material 30 used for an optical element molding die is placed in a space surrounded by molding mother dies 31 and 32 for forming a molding die and a heating ring 33 containing a heater. The lower surface of the molding die 32 is processed into a flat surface, and the upper surface of the molding die 31 is processed into the surface shape of an optical element to be pressed. The molding dies 31, 32 and the glass material 30 are sufficiently heated by the heating ring 33 to near the softening temperature of the glass material 30, and then the molding dies 31, 32 are pressed to transfer the surface shape of the molding dies to the glass material 30. Then
Cool and remove the glass mold from the mold. FIG. 7 shows the shape of the glass molding die 42 for molding an optical element formed. After that, a mold-releasing film is formed on the molding surface of the glass molding die 42 by a method such as a vacuum deposition method.

FIG. 8 shows the configuration of an optical element molding apparatus using a glass molding die. As shown in the figure, the optical material 40 is placed in the space surrounded by the lower glass mold 41, the upper glass mold 42, and the heating ring, that is, the so-called body mold 43, heated to near the softening temperature of the optical material, and then pressed and pressed. It was cooled as it was, and the optical element was taken out.

[0006]

However, in such a conventional glass molding apparatus and molding method, the glass molding dies 41 and 42 have a cylindrical shape. Prior to the optical element molding, the molded glass molding dies 41 and 42 are formed with a release coating on the surface. However, since the shape is cylindrical, they are slippery and difficult to hold during the working process. That is, in order to form a release coating by the vacuum vapor deposition method, above the vapor deposition source,
It is necessary to keep the release coating formation surface (optical element molding surface) facing downward and hold it horizontally. Therefore, for example, it is conceivable to form a notch groove for holding on the side surface of the glass molding die and use the groove to fix the glass molding die in the vapor deposition device while preventing sliding. However, when vacuum vapor deposition is performed on a large number of glass molding dies, there is a problem in that it takes time and effort to fix the glass molding dies and the productivity of the deposition process decreases.

When the optical element is press-molded using the glass molding die, the glass molding die 4 is used to transfer the glass molding die from the disassembling and assembling stage to the molding stage.
The side surfaces of 1, 42 are clamped and held, or the lower glass mold 41
There is a method in which a plate is inserted underneath to transfer the glass molding dies 41 and 42. However, if the optical element molding material is transported by sandwiching the side surface, the optical element molding material is easily damaged by the holder, and the optical element formed by molding the damaged optical element molding material remains with scratches even after molding. In addition, when mounted on a plate and transferred, there is a problem that the optical element molding material is damaged by vibration or impact when it is installed in the molding apparatus.

Further, since the glass molding dies 41 and 42 are cylindrical, the glass molding dies 41 and 42 easily move along the inner surface of the barrel mold during the molding process, particularly in the cooling process after press molding. The thickness of the optical element after molding was not constant, and there was a problem that the optical performance varied.

The present invention solves such a problem, and the glass mold is easily chucked, the optical element molding material is not damaged during the transfer, and the optical performance is constant and the variation is small. And a manufacturing method thereof and an optical element molding method.

[0010]

In order to solve the above-mentioned problems, the present invention comprises a forming cylinder mold in which an upper forming mold and a lower forming mold are slidably incorporated. A method of placing an optical element material in an enclosed space, heating the optical element material to soften it, and press-molding it. The upper molding die and the lower molding die are mainly glass materials, and the optical surface of the optical element is molded. A cylindrical portion or a columnar portion having a molding surface processed into a predetermined shape, and a collar portion connected to the end surface of the cylindrical portion or the columnar portion on the side opposite to the molding surface, each of which has a shape similar to the shape of the optical element. The mold is formed by heating and pressurizing with an upper and lower processing mold having an optical surface processed into the above.

The upper molding die and the lower molding die are mainly made of a glass material, and have a cylindrical portion or a columnar portion having a molding surface processed into a predetermined shape for molding the optical surface of the optical element, and the cylindrical portion or The upper and lower forming dies are formed by heating and pressurizing with the upper and lower processing dies each having a collar part connected to the end surface on the side opposite to the forming surface of the columnar part, and having an optical surface processed into a shape similar to the shape of the optical element. The mold and the lower mold are slidably arranged in the mold body, the optical element material is placed in the space surrounded by the upper and lower molds and the mold body, and the optical element material is heated to soften it. The optical element is manufactured by lowering the molding die and press-molding the optical element material.

[0012]

According to the structure and method described above, a machining die having a collar portion is prepared by machining a cemented carbide material in advance, and using this machining die, the glass transition temperature higher than the glass transition point of the optical element material is used. A glass material having dots is press-molded under heating to form a mold having a collar portion. An optical element material can be placed between the molds and press-molded at a temperature near the glass transition point. Further, according to the present invention, a large number of glass molding dies can be manufactured by manufacturing a pair of working molds by machining and molding a high melting point glass molding mold for a molding mold using the working molds. In addition, a plurality of glass molds are sandwiched between the flanges, and the transfer robot is used to transfer the heating, molding, and cooling steps, and press molding is performed continuously by an automatic machine to ensure high-precision optics. It is possible to produce a large number of elements uniformly.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical element molding die according to an embodiment of the present invention, a method for manufacturing the same, and an optical element molding method will be described below with reference to the drawings. 1 (a) to 1 (e) show the configuration of a glass molding die manufacturing apparatus of this embodiment. As shown in FIG. 1A, a molding master mold (hereinafter abbreviated as a master mold) for molding an optical element molding mold (hereinafter abbreviated as a mold mold) 2 on an assembly stage 6A.
The flat plate-shaped molding die material 10a is placed on the lower working die 3 to be the following, and then the working barrel die 5 is inserted according to the outer diameter of the molding die material, and the lower end is pressed until it contacts the lower working die 3. To do. The plate-shaped molding die material 10a has a surface roughness of the upper surface of 0.1 μm.
It is necessary to finish to m or less. On the other hand, since the fractured surface formed by stress-breaking the glass rod material is a mirror surface, it is not necessary to further perform mirror surface processing. Therefore, in this example, a disk having at least a split cross section on its upper surface was used as the molding die material.

The lower working die 3 is made of a cemented carbide steel, and the working surface is prefabricated with high precision by a surface grinder.
The outer diameter of the lower processing die 3 is clamped by the robot arm,
It is conveyed to the processing stage 6B as shown in (b). A heater is built in the processing stage 6B and is kept at a predetermined temperature in advance. The mold material 10a needs to have a softening temperature higher than the glass softening temperature of the optical element material. The optical element material used in this example is SF8, and the glass transition point is 420 ° C. Further, the molding die materials 10a and 10b have a BK having a glass transition point of 550 ° C.
7 was used. The temperature of the processing stage 6B was set to 750 ° C. Further, the upper heater block 7B has a built-in heater,
It is connected to a pressure cylinder and moves up and down. The upper heater block 7B was set to 770 ° C.

Here, first, the collar portion 1 of the molding die shown in FIG.
1 is formed. The lower working die 3 conveyed onto the working stage 6B is preheated for 10 minutes to sufficiently heat the forming die material 10a, and then the upper heater block is lowered to move the working die 5
Abut the upper end surface of. Thereafter, a pressure of 3 kg / cm ² is applied, and the lower end surface of the working cylinder die 5 is pressed until it comes into contact with the upper surface of the flange portion of the lower working die 3. An assembly robot (not shown) is arranged between the processing stage 6B and the molding stage 6C shown in FIG. 1 (c). In order to form the cylindrical portion 12 of the forming die 10A shown in FIG. 2, the assembling robot places the forming die material 10b on the forming die material 10a whose brim portion is formed. A cylindrical shape is suitable for the molding die material 10b, and similarly to the molding die material 10a, a cylindrical material formed by stress-cutting a bar material was used.

After the molding die material 10b is placed on the molding die material 10a, the upper working die 4 is inserted into the working barrel die 5 by the assembling robot and brought into contact with the upper surface of the molding die material 10b. It is transferred to the molding stage 6C of FIG. The upper working die 4 uses a cemented carbide steel as in the lower working die 3, and the forming surface is pre-machined with the same shape as the shape of one surface of the optical element at the time of completion with ultrahigh precision. Like the processing stage 6B, the molding stage 6C is preheated to 750 ° C. and the upper heater block 7C is preheated to 770 ° C. After conveying to the molding stage 6C, lower the upper heater block 7C,
After preheating for 7 minutes, the molding material 10b is pressed at a pressure of 4 kg / cm ² for 3 minutes to transfer the shape of the molding surface of the upper working mold 4 to the molding material 10b.

Next, it is conveyed to the cooling stage 6D heated to 550 ° C. shown in FIG. 1 (d) and brought into contact with the upper heater block 7D. After 10 minutes, when the temperature of the molding die material 10b becomes close to 550 ° C. which is its glass transition point, the upper heater block 7D is moved up and conveyed to the cooling stage 6E shown in FIG. 1 (e). After leaving it for 10 minutes, the outermost side of the lower working die 3 is sandwiched by a robot arm and conveyed to the die disassembling / assembling stage 6A shown in FIG. 1A, and the working die is disassembled to take out the lower shaping die 10A.

The upper molding die 10B is similarly manufactured by the above-described molding die manufacturing method. The molding surfaces of the molding dies 10A and 10B thus produced had a shape that was completely the same as the shapes of the molding surfaces of the upper and lower working dies 3 and 4.

In the present embodiment, the cylindrical mold is explained, but it is also possible to connect a columnar part having an elliptical, quadrangular or rhombic cross section to the collar part. Further, the outer shape of the collar portion can be selected similarly to the columnar portion.

According to the above-described molding die manufacturing apparatus and manufacturing method, the molding die can be mass-produced in 10 minutes. A protective film can be collectively formed on the molding surface of the molding dies that have been molded. For example, using a sputtering device, Pt-I
Although an r-based alloy film is formed, it is possible to mechanically and safely perform degreasing and cleaning before film formation and installation on a sputtering device by using a transfer jig that uses the collar, and to prevent damage to the forming surface. Can be prevented.

Next, a method of manufacturing an optical element using the above molding die will be described. FIG. 3 shows the configuration of the optical element manufacturing apparatus of this embodiment. As shown in FIG. 3, an upper molding die 10B and a lower molding die 10A made of a glass material are inserted inside the molding barrel die 22 adjusted to an arbitrary height to prevent axial misalignment of both molding dies. An optical element having a predetermined thickness is molded. In a space surrounded by the upper molding die 10B, the lower molding die 10A, and the molding barrel die 22, a cylindrical optical element material 1 shown in FIG. 4 is formed into a cylinder so that both end surfaces thereof are in contact with the upper molding die 10A and the lower molding die 10B. Install the shaft vertically. The molding barrel die 22 is made of a glass material having a coefficient of linear expansion larger than that of the optical element material 1. In this embodiment, the linear expansion coefficient is 100 to 300 ° C.
A glass material of 50 × 10 ⁻⁷ / ° C. was used. The upper heater block 23 is connected to a cylinder rod, and a predetermined pressure is applied to the upper molding die 10B via the upper heater block 23 by an air cylinder. The optical element material 1 is an optical glass SF8 having a diameter of 3 mm and a length of 4 mm, a glass transition point of 420 ° C., a yielding temperature of 454 ° C., a softening temperature of 550 ° C., and a linear expansion coefficient of 100 × 300 ° C. at 90 × 10 ⁻⁷ / ° C. is there. The side surface is finished by centerless processing, and the surface roughness is 3 μm. The upper and lower optical surfaces are mirror-finished by polishing, and the surface roughness is 0.1 μm. The total deformation dimension is 2 mm until the optical element material is press-molded and the molding is completed.

Next, the molding process of the optical element will be described. The forming die is transferred onto the forming stage 24 in the forming machine, and the upper heater block 23 is brought into contact with the upper surface of the upper forming die 10B.
At this time, in the molding die, a closed space X is formed between the molding surfaces of the upper and lower molding dies 10A and 10B and the end surface of the optical element 1.
Is made. Upper heater block 23 and molding stage 2
In No. 4, it is necessary to heat the optical element molding material 1 to a temperature at which it is easily deformed by the pressing force of the molding die. However, if the heating temperature is too high, it will not be possible to mold to the specified shape accuracy, so
Generally, the temperature is set between the bending temperature and the softening temperature of the optical element molding material 1.

In this embodiment, the temperature of the upper heater block and the lower heater block is set to 540 ° C. This temperature is slightly higher than that of a conventional mold having a base material of cemented carbide. This is because the mold is made of glass and has a low thermal conductivity. The temperature of the optical element material 1 is 5
When it reaches around 40 ℃, the viscosity of the optical element material becomes 1
It is 0 ¹⁰ poise. Next, the upper heater block is pressed and the optical element material 1 is pressed by the upper molding die 10B. The pressure at this time is preferably ² kg / mm ² or more. The molding process is performed in two stages. Of the total deformation size of 2 mm, 1.6 mm is first pressure-molded. After the start of pressurization, when 0.8 mm is deformed, the pressurization is stopped once, and the upper heater block 23 is lifted and separated from the upper molding die 10B. Immediately before stopping the pressurization, the closed space X to which the positive pressure was applied returns to the normal pressure. Even when the pressure is stopped, the mold and the optical element material are kept in contact with each other.

Next, the upper heater block is lowered again and brought into contact with the upper mold. In this step, the closed space X has disappeared. Then, the heating is stopped and the pressurization is started while cooling, so that the total deformation amount is 0.4 mm. Mold temperature is 4
When the temperature reaches 00 ° C., the pressurization is terminated and the upper heater block 23 is raised. In the cooling step after the total deformation amount is molded, the optical element shrinks as the temperature drops, but the molding cylinder die 22 also shrinks. The amount of shrinkage of both the optical element and the forming cylinder mold is larger in the forming cylinder mold with respect to the temperature difference t, both in the longitudinal length L and the linear expansion coefficient A. Shrinkage is t × L × A
The shrinkage amount of the molding cylinder is larger than that of the optical element. Therefore, during the cooling process, especially until the vicinity of the glass transition point of the optical element, the molding surfaces of the upper and lower molding dies are pressed and brought into close contact with the surface of the optical element, so that the shape of the molded optical element does not collapse. After the cooling process is completed, the upper and lower molds 10A and 10B are taken out from the molding stage 24 and cooled to room temperature. After cooling completely, the mold is opened and the optical element is taken out. The molded optical element had the shape accuracy as designed and satisfied the optical characteristics.

The molding die becomes unusable after about 3000 shots because the molding surface becomes rough. However, mass production of the optical element can be carried out very inexpensively by the above-mentioned molding die manufacturing method, and thus there is no problem in mass production of optical elements.

Table 1 shows combinations of various mold materials and optical element materials, glass transition points, and changes in the mold surface after 100 shots molding. In (Table 1), the material name of Schott was used as the glass material name. In this combination No. Only in No. 3, the shape of the mold changed, but in other combinations, there was no change. From the above results, it is understood that the difference in glass transition point between the mold material and the optical element material needs to be 50 ° C. or higher.

[0027]

[Table 1]

In this embodiment, an example in which a protective film is formed on the surface of the molding die has been described, but the same effect can be obtained even if a mold release material is applied in advance on the surface of the optical element material instead of the protective film. can get. Further, in the present embodiment, an example in which SF8 is used as the optical element material has been described, but the present invention is not limited to this, and other optical element materials such as organic materials such as polymethylmethacrylate (PMMA) can be used. The same effect can be obtained by using a polymer material.

In this embodiment, the difference in glass transition point between the mold material and the optical element material is 120 ° C., but the present invention is not limited to this, and the glass of the mold material is used. It is desirable that the transition point is as high as possible, and it is desirable that the transition point is high and the abrasion resistance is excellent.

[0030]

As is apparent from the above description of the embodiments of the present invention, according to the present invention, a working die is prepared by machining a cemented steel material in advance, and the working die is used to form a glass of an optical element material. A glass material having a glass transition point higher than the transition point is press-molded under heating to produce a mold. An optical element material is placed between the molds and press-molded at a temperature near the glass transition point. According to this method, a large number of glass molding dies can be produced by preparing a pair of working dies. Further, it is possible to uniformly produce a large number of glass optical elements using the glass mold.

[Brief description of drawings]

1A to 1E are cross-sectional views showing a method for manufacturing a mold according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of the lower molding die.

FIG. 3 is a sectional view showing the configuration of the optical element molding apparatus.

FIG. 4 is a perspective view showing the shape of the optical element material.

FIG. 5 is a sectional view showing the structure of the optical element.

FIG. 6 is a cross-sectional view showing the configuration of a conventional molding die manufacturing apparatus.

FIG. 7 is a sectional view showing the structure of the mother mold.

FIG. 8 is a cross-sectional view showing the configuration of the optical element molding apparatus.

[Explanation of symbols]

 1 Optical Element Material 2 Mold 3 Lower Machining 4 Upper Machining 5 Machining Mold 6A Mold Disassembly and Assembly Stage 6B Machining Stage 6C Molding Stage 6D, 6E Cooling Stages 7B, 7C, 7D Upper Heater Block 10a, 10b Molding Material 10A Lower mold 10B Upper mold 11 Collar part 12 Cylindrical part 22 Mold body 23 Upper heater block 24 Molding stage X Closed space

Claims (15)

[Claims] 1. An optical element material, comprising: a molding barrel mold in which an upper molding mold and a lower molding mold are slidably contained, wherein an optical element material is placed in a space surrounded by the upper and lower molding molds and the molding cylinder mold. A structure for heating and softening a material to press-mold it, wherein the upper molding die and the lower molding die have a cylindrical portion having a molding surface processed into a predetermined shape for molding an optical surface of an optical element, or An optical element molding die comprising a columnar portion and a collar portion connected to an end surface of the cylindrical portion or the columnar portion on the side opposite to the molding surface, and press-molding an optical element material. 2. The optical element molding die according to claim 1, wherein the upper molding die and the lower molding die first form a collar portion and then form a cylindrical portion or a columnar portion. 3. The optical element molding die according to claim 1, wherein the glass transition point of the molding die material is higher than the glass transition point of the optical element material, and the glass transition point temperature difference has a lower limit of 50 ° C. 4. The optical element molding die according to claim 1, wherein the molding die material comprises a flat plate-shaped material forming a collar portion and a columnar material forming a cylindrical portion or a columnar portion. 5. The optical element molding die according to claim 1, wherein the molding die material is a flat plate-shaped or columnar material having a split cross section. 6. An optical element material is provided, which comprises a molding barrel that slidably houses an upper molding die and a lower molding die, and an optical element material is placed in a space surrounded by the upper and lower molding dies and the molding barrel. A method of heating and softening a material to press-mold it, wherein the upper molding die and the lower molding die are mainly made of a glass material, and a molding surface processed into a predetermined shape for molding an optical surface of an optical element. Vertical processing having a cylindrical portion or a columnar portion having a and a collar portion connected to the end surface on the opposite side of the molding surface of the cylindrical portion or the columnar portion, and having an optical surface processed into a shape similar to the shape of the optical element A method for manufacturing an optical element molding die, which comprises heating and pressurizing the mold to form a molding die. 7. The method of manufacturing an optical element molding die according to claim 6, wherein the upper molding die and the lower molding die first form a collar portion and then form a cylindrical portion or a columnar portion. 8. The method for producing an optical element molding die according to claim 6, wherein the glass transition point of the molding die material is higher than the glass transition point of the optical element material and has a glass transition point temperature difference of 50 ° C. as a lower limit. . 9. The method for manufacturing an optical element molding die according to claim 6, wherein a flat plate-shaped material forming a collar portion and a columnar material forming a cylindrical portion or a columnar portion are used as the molding die material. 10. The method for producing an optical element molding die according to claim 6, wherein a flat plate-shaped or columnar material having a split cross section is used as the molding die material. 11. The upper molding die and the lower molding die are mainly made of a glass material, and a cylindrical portion or a columnar portion having a molding surface processed into a predetermined shape for molding an optical surface of an optical element, and the cylindrical portion. Alternatively, the upper and lower molding dies are formed by heating and pressing with a vertical processing die having a collar portion connected to the end surface on the side opposite to the molding surface of the columnar portion and having an optical surface processed into a shape similar to the shape of the optical element. The upper molding die and the lower molding die are slidably arranged in a molding barrel die, an optical element material is placed in a space surrounded by the upper and lower molding die and the molding barrel die, and the optical element material is heated. Then, the optical element molding method is performed in which the optical element material is softened, and the upper molding die is lowered to press-mold the optical element material. 12. The method for forming an optical element according to claim 11, wherein a barrel die mainly made of a glass material is used. 13. The method for molding an optical element according to claim 11, wherein the glass transition point of the molding die material is higher than the glass transition point of the optical element material, and the glass transition point temperature difference has a lower limit of 50 ° C. 14. The optical element molding method according to claim 11, wherein a transparent organic polymer is used as the optical element material. 15. The optical element molding method according to claim 11, wherein the molding barrel is mainly made of a glass material, and a glass material having a linear expansion coefficient of the glass material larger than those of the upper and lower molding materials is used.