JP3219460B2 - Optical element mold and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for press-molding an optical element and a method for producing the same.

[0002]

2. Description of the Related Art A technique for heat-softening a glass material to press-mold an optical element is known. It is important to accurately transfer the shape of the molding die to be pressed to the glass material.However, when molding a molded product with a large thickness difference, the difference in temperature distribution inside the glass material increases. A phenomenon referred to as sink occurs. In order to prevent such a phenomenon, for example, Japanese Patent Application Laid-Open No.
No. 8716. The technique described in this publication is a technique in which the mold forming surface is divided into several members concentrically, and the temperature is controlled independently of each other, thereby providing a difference in the cooling rate of the glass. Details will be described with reference to FIG.

FIG. 8 is a diagram shown in FIG.
It is sectional drawing from the front which shows the state during the shaping | molding of the shaping die. The press mold 30 includes an upper mold 31 and an upper mold 31.
And a lower mold member 32 disposed opposite to the lower mold member 32. The lower mold member 32 includes a split mold 33 and a split mold 34 which are concentrically split in the axial direction.
When the glass material 35 is pressed and formed by the pressing die 30 having the above-described configuration, the temperature of each of the split dies 33 and 34 is controlled independently, so that the temperature difference is made concentric with the glass material 35. This is the technology of the configuration.

[0004]

In carrying out the molding method using the pressing die disclosed in the above publication, there has been a problem that the temperature control means of the molding apparatus and its configuration are complicated and the cost is increased. Further, there is a problem that it is extremely difficult to manufacture a mold divided into concentric circles. That is, if any gap or step is generated between the divided molds, there is a problem that the glass penetrates there and burrs are generated in the molded optical element.

In order to reduce the gap and the step, the tolerances such as the inner and outer diameters and cylindrical accuracy of the parts to be combined concentrically must be extremely severe. Difficult to process. In particular, heat-resistant materials used as glass optical element molding dies are cemented carbides and various ceramics, and it is substantially difficult to process these difficult-to-cut materials with severe tolerances as described above. . Even if the above processing can be performed, it is extremely difficult to combine them because the gaps between the members are very small, and the workability is poor. If there is, there is a risk that both members may be damaged, and it is practically impossible to combine them without any gap.
Therefore, it is possible to mold with the mold of the method described in the above-mentioned gazette, but it is not inevitable to use even if a little burr occurs, but molding of the optical element, or performing various processing after molding, greatly increasing the cost There is a restriction that the optical element is limited to the optical element that can be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a simple structure and a mold for forming an optical element for molding a high-quality optical element which prevents sink marks with an inexpensive mold. It is intended to provide a method.

[0007]

According to the present invention, there is provided a mold for press-molding an optical element, wherein pores provided in the mold correspond to thin and thick portions of the optical element to be molded. Are optical element molding dies having different ratios. Further, in the molding die of the present invention, in the molding die for press-molding the optical element, the ratio of the pores provided in the mold base of the molding die is different depending on the thin portion and the thick portion of the optical element to be molded. An optical element molding die, wherein a thin film for preventing fusion during molding of the optical element is formed on the molding surface side of the mold base. Further, the mold of the present invention, in a mold for press-molding an optical element, corresponding to the thin portion and the thick portion of the optical element to be molded, differing the thermal conductivity in the mold base of the mold and An optical element molding die in which a thin film for preventing fusion during molding of the optical element is formed on the molding surface side of the mold base. Further, the method for manufacturing a mold according to the present invention is a method for manufacturing a mold for press-molding an optical element, wherein the specific component contained in the mold base is etched by etching in accordance with the shape of the optical element to be molded. This is a method for manufacturing an optical element mold formed by changing the porosity. Further, the manufacturing method of the molding die of the present invention, in the method of manufacturing a molding die for press-molding an optical element, corresponding to the shape of the optical element to be molded, impregnating a substrate made of a sintered body with an impregnating agent, This is a method for manufacturing an optical element molding die formed by fusing with a sintered portion in the base material and changing the porosity.

[0008]

The porosity changes when molded with the optical element mold of the above construction, and the thermal conductivity changes significantly. The thermal conductivity of a gas is, for example, air = 0.
02 w / mk, graphite = 100 w / mk,
Because it is two to four orders of magnitude smaller, the presence of the pores significantly reduces the thermal conductivity. That is, the higher the porosity, the lower the thermal conductivity. Therefore, when molding an optical element, the temperature distribution inside the molded product is reduced by increasing the porosity of the portion corresponding to the thin portion of the molded product and decreasing the porosity of the portion corresponding to the thick portion of the molded product. Was prevented. Based on the concept described above, using a technique of etching a specific component of the mold base material, or impregnating with an impregnating agent, one having a different porosity at the inner and outer circumferences from the integrated one, `` that is, within the integrated base material By manufacturing a material having a different porosity (or thermal conductivity) on the inner and outer circumferences, a mold can be manufactured with a simple structure and at low cost, and by molding an optical element using the mold, High quality optical elements without sink marks can be molded with high productivity.

[0009]

[Embodiment 1] A specific example of an optical element molding die and a method of manufacturing the same according to the present invention will be described with reference to the drawings. 1 to 3 show the steps of manufacturing the mold of Example 1 according to the method of manufacturing an optical element mold of the present invention. FIG. 1 is a front sectional view showing a state in which a mold base is immersed in a container filled with a solution. FIG. 2 is a front sectional view showing a step following FIG. FIG. 3 is a cross-sectional view from the front showing a main part in a state where the mold manufactured according to the present embodiment is mounted on a molding machine.

In order to form a mold base, 76% by weight of SiO ₂ ,
_{B 2 O 3 13wt%, Na} 2 O6wt%, Al 2 O 3 4
A glass powder having a composition of wt% and other unavoidable impurities is charged into a crucible, mixed and melted at 1100 ° C. for 1 hour. By doing so, an irregular shaped glass lump is obtained. Further, the quenched glass ingot is heated in a heating furnace for 510 minutes.
Heat treatment at 100 ° C. for 100 hours to cause phase separation. Next, the glass lump is sent to a grinding step to form the glass lump to a desired size and is ground. In this embodiment, for example, it is formed by grinding into a round bar 3 having a shape of φ8 mm and a length of 20 mm.

As shown by the arrow in FIG. 1, the glass material (round bar) 3 formed by the above-mentioned grinding step is put into a container 1 filled with an H ₂ SO ₄ solution 2 and suspended for 240 hours by a suspension. Soak. By this immersion, the B ₂ O ₃ phase and the Na ₂ O phase contained in the glass lump 3 elute into the solution. When a cross section of the glass rod 3 produced by the above-mentioned dissolution method was cut in a radial direction, a large number of pores were formed from the outer periphery to a depth of about 3 mm. However, no pore was observed in the range of φ2 from the center (axial center). When the center and the outer periphery were cut out of the glass material 1 and the thermal conductivity was measured, the center was 1.13 watts.
/ Mk, and the outer peripheral portion was 0.77 w / mk.

As shown in FIG. 2, the grinding process is performed to form a molding surface corresponding to the shape of an optical element formed on one of the pair of glass bars 3 manufactured by the above method. Is done. In this grinding step, first, the lower end 5 of the eluted glass lump 3 is cut by 5 mm, and the cut lower end surface 8 is ground and polished with a concave aspheric surface 6 having a paraxial curvature radius of, for example, R10.3 mm. . The above-mentioned ground and polished aspheric surface 6 is coated with a thin film having a high effect of preventing fusion when glass such as CrN or BN is formed via an intermediate layer for enhancing the adhesive force, and the production of the molding die is completed. I do.

The configuration of a molding apparatus for molding a plano-convex glass optical element using the molding die manufactured by the above method will be described with reference to FIG. The pair of molds 10 and 14 manufactured by the above-described method have their base ends 7 and 16 respectively.
Are fixedly mounted on the upper die mount 11 and the lower die mount 17 disposed facing the apparatus, with their molding surfaces facing each other. An upper mold heater 13 for heating the upper mold 10 is embedded in the upper mold mount 11 to which the upper mold 10 is attached, and is fixedly attached to the apparatus. Also, a lower mold heater 18 for heating the lower mold 14 is embedded in a lower mold mount 17 to which the lower mold 14 is attached, and the lower mold mount mounts a glass material to be formed and rises. The upper mold 10 is configured to be movable up and down so as to be pressed against the upper mold 10.

That is, the glass material heated and softened is conveyed between the upper mold 10 and the lower mold 14 to near the transition point of the glass molding material, and is brought into contact with the upper mold 10 when the lower mold 14 is lifted and pressed. Molded. As a result of the press molding, an optical element having good shape accuracy without sink marks was obtained. Further, in the present embodiment, an example in which a glass material is made porous and used as a mold has been described, but the present embodiment is not limited to this. It was found that similar results were obtained.

According to the above-mentioned mold and the method of manufacturing the same,
By increasing the porosity of the outer peripheral part of the upper mold, the cooling rate becomes slower in the thinner part (outer peripheral part) of the optical element to be molded. Therefore, the thick part (central part) of the molded article and the thinner part of the molded article The difference in cooling rate between the portions (outer peripheral portion) can be suppressed to be small, and an optical element without sink marks can be obtained.

[0016]

Embodiment 2 Embodiment 2 of the optical element molding die and the method of manufacturing the same according to the present invention will be described with reference to FIGS. FIG.
It is sectional drawing from the front which shows the manufacturing process of Example 2 which concerns on the optical element shaping | molding die of this invention, and its manufacturing method. FIG.
FIG. 7 is a front sectional view of an optical element molding die manufactured according to a second embodiment. In the drawings of this embodiment, the same members, the same shapes, the same configurations, and the same methods as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In this embodiment, the glass substrate is melted and cooled to obtain an irregular shaped glass block as described in the first embodiment, and the glass block is heated in a heating furnace at a temperature of 510.degree. The steps of heat-treating for a time to form a phase separation in the glass lump and grinding the glass lump to a desired size in the grinding step to obtain a glass round bar are the same, and will not be described.

As shown in FIG. 4, a hole 21 having a diameter of φ2 is formed from the center of the upper end surface of the glass round bar 20 to, for example, a depth of 15 mm, and an H ₂ So ₄ solution 22 is injected into the hole 21. Subsequently, a glass round bar 20 filled with the solution 22 is put into 100
It is stored in a box (not shown) kept at ° C. and left for 240 hours. The B ₂ O in the glass round bar 20
_{The three} phases, the Na ₂ O phase, elute in the solution 22. Due to this elution, the porosity near the center (axial portion) in the glass round bar 20 becomes large, and the glass round bar 2 having the porosity OVo1% is formed in the outer peripheral portion. The glass round bar 20 described above is, for example, shown in FIG.
As shown in (1), the lower end surface is ground and polished to a convex aspheric surface 23 having a paraxial R12.1. Subsequent steps are the same as those in the first embodiment, and are omitted.

[0019]

Third Embodiment A third embodiment of the optical element molding die of the present invention and a method of manufacturing the same will be described with reference to FIGS. FIG.
It is sectional drawing from the front which shows the manufacturing process of Example 3 which concerns on the optical element shaping | molding die of this invention, and its manufacturing method. FIG.
FIG. 13 is a front sectional view showing the optical element mold manufactured according to the third embodiment. In the drawings of the present embodiment, the same members, the same shape, and the same configuration as those of the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted. The description of the same method is also omitted.

The cylindrical member indicated by reference numeral 24 in FIG. 6 is obtained by grinding a substrate made of an Al ₂ O ₃ sintered body having a desired shape. For example, it is ground to a φ11 length of 20 mm. This ground sintered substrate 24
To 69% of SiO ₂ , 10% of B ₂ O ₃ , 9% of Na ₂ O,
FIG. 6 shows a state of being immersed in a container 1 filled with 8% of K ₂ O, 3% of BaO, and a glass melt 25 made of unavoidable impurities. The glass melt 25 into which the sintered base material 24 is immersed is always kept at 1500 ° C. By immersing the glass melt 25 in the glass melt 25 for 2 hours, the glass melt 25 as shown by an arrow in FIG. , Penetrate into the inside of the sintered base material 24. Melted glass melt 2
5 and Al ₂ O 3 in the sintered substrate 24 are fused and completely integrated to form a glass round bar 27. The integrated glass round bar 27 is again ground into a φ11 length of 20 mm.

The glass round bar 2 manufactured according to the above embodiment.
Looking at the cross-sectional shape of No. 7, the porosity was 3% at the outer periphery and 24% at the center, and the porosity gradually increased from the outer periphery toward the center. The thermal conductivity of the central part was 10 w / m. k, 18 w / m. k.
One end face (upper end face of reference numeral 27) of the glass round bar 27 manufactured by the above method was ground into a convex spherical surface 28 of R20.9. Furthermore, a thin film of CrN, BN, or the like was formed on the upper surface of the convex spherical surface 28 by lamination, and a glass optical element was molded by a molding apparatus. As a result, an optical element having good shape accuracy without sink marks was obtained.

[0022]

According to the present invention having the above configuration and method,
Since the molding tool corresponding to the shape of the optical element to be molded can be manufactured at a low cost by a simple method, the optical element molded with the molding tool is of high quality without sink marks, has good cost performance, and is produced. Various effects such as good molding can be obtained.

[Brief description of the drawings]

FIG. 1 is a front cross-sectional view showing a manufacturing process of a molding die of Example 1 according to a method of manufacturing an optical element molding die of the present invention.

FIG. 2 is a cross-sectional view from the front showing a manufacturing process following FIG. 1;

FIG. 3 is a cross-sectional view from the front showing a main part in a state where the mold manufactured according to Example 1 is mounted on a molding apparatus.

FIG. 4 is a cross-sectional view from the front showing a manufacturing process of an optical element forming die and a manufacturing method thereof according to a second embodiment of the present invention.

FIG. 5 is a sectional view from the front showing the optical element mold manufactured according to the second embodiment.

FIG. 6 is a front sectional view showing a manufacturing process of an optical element molding die and a method of manufacturing the same according to a third embodiment of the present invention.

FIG. 7 is a front sectional view showing the optical element mold manufactured according to the third embodiment.

FIG. 8 is a front cross-sectional view showing a main part of a conventional optical element in a molding state using a molding die.

[Explanation of symbols]

1 container ₂ H 2 So ₄ solution 3,20,27 glass rod 4,26 arrow 5 the lower end 6,23,28 aspherical 7 upper end 8 lower portion 11 upper die mount 13 upper heater 14 lower mold 15 upper surface 16 Lower end face 17 Lower mount 18 Lower heater 21 Hole 22 H ₂ So ₄ solution 24 Al ₂ O ₃ sintered substrate 25 Glass solution

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-139761 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 11/00-11/16

Claims (5)

(57) [Claims] 1. A molding die for press-molding an optical element, wherein a ratio of pores provided in the molding die is made different according to a thin part and a thick part of the optical element to be molded. Optical element mold. 2. A molding die for press-molding an optical element, wherein a ratio of pores provided in a mold base of the molding die is made different according to a thin part and a thick part of the optical element to be molded. An optical element molding die, wherein a thin film for preventing fusion during molding of the optical element is formed on a molding surface side of a mold base. 3. A molding die for press-molding an optical element, wherein thermal conductivity in a mold base of the molding die is varied according to a thin portion and a thick portion of the optical element to be molded. An optical element molding die, wherein a thin film for preventing fusion during molding of the optical element is formed on a molding surface side of the material. 4. A method for manufacturing a molding die for press-molding an optical element, wherein a specific component contained in a mold base material is changed in porosity by etching in accordance with the shape of the optical element to be molded. A method for manufacturing an optical element molding die, characterized in that it is formed. 5. A method for manufacturing a molding die for press-molding an optical element, wherein a substrate comprising a sintered body is impregnated with an impregnating agent in accordance with the shape of the optical element to be molded. A method for producing an optical element molding die, wherein the molding is performed by changing the porosity by fusing with a joint.