JPH1135333A - Production of glass shaped body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a glass optical element having better surface accuracy and more specifically, the glass optical element having Newton's rings within ±2 pieces and astigmatism within 0.5 piece. SOLUTION: This process for producing the glass shaped body includes a stage for initially pressurizing and forming the glass blank to be formed which has a viscosity in a range of 10<5.5> to 10<8> poises with forming molds exhibiting the temp. at which the glass blank to be formed exhibits a viscosity of 10<8> to 10<10.5> poises (provided that the temp. of the glass blank to be formed is higher than the temp. of the forming molds), a stage for lowering the forming molds and the formed glass (hereafter described as the formed glass) to the transition point of this glass or below and a stage for taking the formed glass out of the forming molds. In such a case, for example, a pressure of 0.001 to 0.5 kg/cm<2> is kept applied on the formed glass during the time from the completion of the initial pressurization to the temp. lowering down to the glass transition temperature or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass molded body including a glass optical element such as a high-precision lens, which does not require grinding or polishing after press molding. In particular, the present invention provides a method for producing a glass molded body having higher surface accuracy with high production efficiency.

[0002]

2. Description of the Related Art High precision glass optical elements such as lenses, which do not require grinding or polishing after press molding, use a molding die which is made by precisely processing a mold material capable of mirror finishing without softening glass being fused. Various molding methods have been recently developed.
In order to obtain a required lens by press molding, it is necessary to satisfy specifications such as wall thickness, outer diameter, and eccentricity, as well as surface shape accuracy and surface quality (smooth surface roughness). It goes without saying that the internal quality such as the refractive index and the transmittance is good.

Further, in putting such a glass optical element molding method to practical use, it is a major problem how much productivity can be obtained. That is, it is a big issue whether more glass optical elements can be produced in a shorter time. One of the means for improving the productivity is to process a plurality of glass materials in parallel, and the other is to reduce the time for one processing. Various improvements have been proposed for each. In order to shorten one processing time, it is necessary to further shorten the cycle of heating and cooling the molding die. For this reason, among the molding conditions, various conditions have been devised for the temperature of the glass material and the temperature of the molding die during molding.

For example, Japanese Patent Application Laid-Open No. Hei 7-10556 (hereinafter referred to as Prior Art 1) discloses that a glass material having a viscosity in the range of 10 ⁷ to 10 ⁹ poise is made of 10 ¹⁰
A method of pressure molding with a mold having a temperature of from 10 to 10 ¹² poise is described. Also, Japanese Patent Application Laid-Open No. 9-12317
Publication (hereinafter referred to as “prior art 2”) includes 10 ^5.5 to 10 ⁹
A method of pressure-molding a glass material having a viscosity in the range of poise using a mold having a temperature at which the glass material exhibits a viscosity of 10 ⁸ to 10 ¹² poise (however, the temperature of the mold is lower than the temperature of the glass material) is known. Are listed. In each method, the temperature of the mold is not unnecessarily increased, so that the time required for raising and lowering the temperature is shortened, and the cycle time is shortened.
Further, in any method, in order to prevent deterioration of the molding surface of the molding die, the glass material which has been heated and softened at a place other than the molding die is transferred to the molding die before molding and molded.

[0005]

By the way, in the method for molding a glass optical element, in addition to the production technical requirements such as the shortening of the cycle time and the prevention of deterioration of the molding die as described above, the requirements for the performance of molded products are also required. There is also. That is, it is also necessary to provide an optical element that meets the needs and has excellent optical properties. The surface accuracy required for the glass optical element varies depending on the use of the glass optical element, but in a normal application, Newton which is a measure of the surface accuracy is within ± 4 lines, preferably within ± 2 lines. Is 1
It is necessary that the number be no more than 0.5, preferably no more than 0.5. With respect to the method described in the example of Prior Art 1, the surface precision of the formed glass optical element was measured. That is, when the compact is released from the mold without cooling to the glass transition point or lower after the pressure molding (the conditions in Table 2 of Prior Art 1), the number of Newtons is 4 to 6, and the habit is 1 to 2 The above standard could not be satisfied. In the case of Prior Art 2, the number of Newtons was ± 2 to 4 but the number of ass was 1 to 1.5, which did not satisfy the above standard. Further, even under the same molding conditions, the obtained surface accuracy may differ depending on the size of the glass material to be molded, the shape of the target molded body, and the like. Particularly, when molding a relatively large glass optical element having an outer diameter of 15 mm or more, a desired surface accuracy cannot be often obtained. Therefore, an object of the present invention is to provide a method for forming a glass optical element having better surface accuracy, and more specifically, Newton is within ± 2,
Another object of the present invention is to provide a method for molding a glass optical element having asbestos of 0.5 or less. In particular, it is an object of the present invention to provide a Newton having ± 2 even for a relatively large glass optical element.
It is an object of the present invention to provide a method for forming a glass optical element capable of obtaining a high surface accuracy of not more than 0.5 pieces and less than 0.5 pieces.

[0006]

The first aspect of the SUMMARY OF THE INVENTION The The present invention is ^105.5 to ¹⁰⁸ poise range this the glass molding material 10 ⁸ to 10 to be molded glass material having a viscosity of
^The process of initial pressing and molding with a mold having a temperature of ^10.5 poise viscosity (however, the temperature of the glass material to be molded is higher than the temperature of the mold), the mold and the molded glass (hereinafter referred to as molded glass) A step of lowering the temperature to below the glass transition point, and a method of producing a glass molded body including a step of removing the molded glass from the mold, wherein the temperature of the molded glass is reduced from the completion of the initial pressurization to the glass transition point or lower. To a method for producing a glass molded body, characterized by continuously applying a pressure of 0.001 to 0.5 kg / cm ² to the glass.

A second aspect of the present invention is ^{105.5 to 108}
A molded glass material having a viscosity in the range of poise is formed in a molding die having a temperature at which the molded glass material exhibits a viscosity of 10 ⁸ to 10 ^10.5 poise (however, the temperature of the molded glass material is higher than the temperature of the molding die). A method for producing a glass molded body, comprising a step of initial pressing and molding, a step of lowering the temperature of a molding die and a molded glass (hereinafter, referred to as a molded glass) below the glass transition point, and a step of removing the molded glass from the molding die. And the glass is ^109.5-
While cooling to a temperature exhibiting a viscosity in the range of 10 ¹² poise,
In the range of 10 to 200 kg / cm ² for the molded glass, the pressure is kept lower than the pressure of the initial pressurization, and then, while the temperature is lowered to the glass transition point or lower, 0.001 to the molded glass.
The present invention relates to a method for producing a glass molded body, characterized by continuously applying a pressure of 0.5 kg / cm ² .

A third aspect of the present invention is ^{105.5 to 108}
A molded glass material having a viscosity in the range of poise is formed in a molding die having a temperature at which the molded glass material exhibits a viscosity of 10 ⁸ to 10 ^10.5 poise (however, the temperature of the molded glass material is higher than the temperature of the molding die). A method for producing a glass molded body, comprising a step of initial pressing and molding, a step of lowering the temperature of a molding die and a molded glass (hereinafter, referred to as a molded glass) below the glass transition point, and a step of removing the molded glass from the molding die. And the glass is ^109.5-
While cooling to a temperature exhibiting a viscosity in the range of 10 ¹² poise,
A pressure of 0.001 to 0.5 kg / cm ² is continuously applied to the formed glass, and then a pressure in a range of 10 to 200 kg / cm ² and smaller than the pressure of the initial pressurization is applied to the formed glass, and then the glass is The present invention relates to a method for producing a glass molded body, wherein a pressure of 0.001 to 0.5 kg / cm ² is continuously applied to a molded glass while the temperature is lowered to a temperature below a transition point.

According to the method for producing a glass molded body of the first aspect of the present invention, for example, for a biconvex lens or a meniscus lens having a diameter of 20 mm or less, the Newton is within ± 2 and the asbestos is 0.5. High surface accuracy of within. Furthermore, according to the method for producing a glass molded body of the second and third aspects of the present invention, for example, in addition to the small lens, a large convex lens exceeding φ20 mm,
Also for a biconcave lens and a lens having a large difference between the wall thickness and the edge thickness, Newton is within ± 2 and ass is 0.5
High surface accuracy of less than one can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. The present invention, both the first to third aspects, 10 ^5.5 to 1
0 ⁸ poise ranging this the glass molding material of the molded glass material having a viscosity of 10 ⁸ to 10 temperature mold that exhibits a viscosity of ^10.5 poises (however, the temperature of the glass molding material is higher than the temperature of the mold ), A step of initial pressurizing and forming, a step of lowering the temperature of a forming die and a formed glass (hereinafter, referred to as a formed glass) below the transition point of the glass, and a step of removing the formed glass from the forming die. It is a manufacturing method.

The kind and shape of the glass constituting the glass material to be formed are conventionally known. The glass material can be, for example, a glass preform or a glass gob. The glass preform refers to a molded product formed into a predetermined shape used as a precursor when molding a glass optical element. The glass preform may be formed by cold forming or molten glass being formed by hot forming, or may be obtained by subjecting them to mirror polishing or the like. Further, the surface can be a rough surface instead of a mirror surface, for example, # 80
A ground product ground with a diamond of 0 can also be used as a glass preform.

The shape of the glass preform is determined in consideration of the size and capacity of the glass optical element as a product, the amount of change during molding, and the like. Further, in order to prevent a gas trap from being generated at the time of molding, it is preferable that the shape of the molded article is such that the center of the molded article first comes into contact with the molding surface of the preform. The shape of the glass preform can be, for example, spherical, marble, disk, spherical, and the like. On the other hand, a glass gob is a piece of glass obtained by dividing molten glass into a predetermined volume, and usually has an irregular shape such as wrinkles. The glass preform is obtained by further molding this glass gob into a predetermined shape. still,
The volume of the preform or gob is made slightly larger than the volume of the final product, and the final outer diameter can be determined by centering in a later step.

In the forming method of the present invention, the glass material is softened by heating to a temperature corresponding to a viscosity of the glass material in the range of 10 ^5.5 to 10 ⁸ poise. When the viscosity of the glass material is 10 ⁸ poise or less, 10 ⁸ to 10
^The glass material can be sufficiently deformed and molded with a mold preheated to a temperature corresponding to a viscosity of ^10.5 poise. Further, when the viscosity of the glass material is 10 ^5.5 poise or more, it is possible to prevent the glass material from being largely deformed by its own weight before molding. In order to stably perform good molding by setting the temperature of the mold at a relatively low temperature, it is appropriate to heat the glass material to a temperature corresponding to preferably 10 ^6.5 to ^107.6 poise. The temperature of the preheating of the mold is such that the viscosity of the glass material is 10 ⁸ to 10 ^10.5.
The temperature is equivalent to poise. If the viscosity is lower than the temperature corresponding to 10 ^10.5 poise, the glass material is greatly stretched,
It is difficult to obtain a thin glass shaped material edge thickness, also difficult to obtain a high surface accuracy, at temperatures above the temperature at which the viscosity corresponds to ¹⁰⁸ poise, the molding cycle time becomes longer than necessary, also, The life of the mold is shortened. The preheating temperature of the mold is preferably a temperature at which the viscosity of the glass material corresponds to 10 ⁸ to ^109.6 poise. The temperature of the molding die is set lower than the temperature of the glass material to be molded. By doing so, the cycle time can be reduced, and the life of the mold can be extended.

Further, it is particularly preferable to set the upper mold temperature lower than the lower mold temperature at the start of the initial pressure molding, from the viewpoint of preventing the molded article from sticking to the upper mold at the time of mold release. More specifically, it is appropriate to lower the upper mold temperature by 5 to 20 ° C. than the lower mold temperature.

As the mold used in the present invention, a conventionally known mold can be used as it is. However, it is preferable to use one in which the molding surface of the mold is made of a carbon film made of a single component layer or a mixed layer of amorphous and / or crystalline graphite and / or diamond.
In a mold having a molding surface composed of a carbon film as described above, even if the temperature of the mold is equal to or higher than the glass transition point of the glass material, fusion (fixation) of glass does not occur. The above carbon film is formed by a sputtering method, plasma C
The film is formed by means such as a VD method, a CVD method, and an ion plating method. When forming a film by the sputtering method, the substrate temperature is 250 to 600 ° C., and the RF power density is 5
-15 W / cm ² , vacuum degree during sputtering 5 × 10 ^-4
Ar as a sputtering gas in the range of 5 × 10 ^-1 torr
It is preferable to sputter an inert gas as described above using graphite as a sputter target. When forming a film by the microwave plasma CVD method, the substrate temperature is 650 to 1000 ° C., the microwave power is 200 W to 1
It is preferable to form a film under the conditions of kW and gas pressure of 10 ^{-2 to} 600 torr using methane gas and hydrogen gas as source gases. When formed by the ion plating method, it is preferable to set the substrate temperature to 200 to 450 ° C. and ionize benzene gas. These carbon films are C-
Includes those having an H bond.

In the forming method of the present invention, the heat-softened glass material is initially pressurized in the preheated forming die. The conditions for the initial pressurization can be appropriately selected depending on the temperature conditions of the glass material and the mold, the material of the glass material, and the like. For example, the pressing time can be in the range of 2 to 60 seconds. By setting the time to 2 seconds or longer, the glass can be sufficiently stretched to obtain a glass optical element having a desired shape. Also, the initial pressurization increases the surface accuracy and the like as much as it becomes longer, but if it is too long, the cycle time cannot be reduced, and the life of the mold may be adversely affected. The upper limit is 60 seconds at most. is there. The molding pressure can also be appropriately determined in consideration of the temperature of the glass material, the temperature of the molding die, and the like, and it is usually appropriate to set the pressure in the range of 30 to 350 kg / cm ² . Preferably 50 to 250 kg / cm
^When the pressure is in the range of ² , and when the glass material to be formed becomes formed glass having a predetermined thickness slightly larger than the thickness of the final product, the initial pressurization can be completed to reduce the thickness variation of the final product. It is preferable from the viewpoint of doing.

Simultaneously with the start of the initial pressurization, during the initial pressurization, or after the end of the initial pressurization, the vicinity of the molding surface of the mold is cooled to lower the temperature below the transition point of the glass material. . The cycle time can be shortened by starting the cooling near the molding surface of the mold early, but depending on the size and shape of the glass molded body, the surface accuracy can be increased by delaying the start of the cooling. The start of cooling is 0 to 20 seconds after the start of the initial pressurization, preferably 5 to 20 seconds.
Appropriately after a second. The rate of cooling can be appropriately determined in consideration of the cycle time and the quality of the formed glass,
For example, it is appropriate to cool at a rate of 20 ° C./min or more. The cooling rate can be slower than 20 ° C./min, but this only unnecessarily increases the molding cycle time. Although it depends on the size and shape of the glass molded body, from the viewpoint of obtaining high surface accuracy, the vicinity of the molded surface is 20 to 18
Cooling at a rate of 0 ° C./min is preferred.

In the first embodiment of the present invention, a pressure of 0.001 to 0.5 kg / cm ² is continuously applied to the formed glass during the period from the completion of the initial pressing to the temperature lower than the glass transition point (final pressing). . The pressure of the final pressing on the molded glass is preferably 0.003 kg from the viewpoint of further increasing the surface accuracy.
/ cm ² or more and 0.2 kg / cm ² or less. At this time, the time of starting the final pressurization, i.e. after completing the initial pressurization, the viscosity of the glass is preferably 10 ^7.6 poise or higher. By ending the initial pressurization with such a viscosity, it is possible to make the shape substantially close to the final product by the initial pressurization, and then to maintain or improve the surface accuracy by the final pressurization to be performed.

In the second aspect of the present invention, the molded glass is cooled while the temperature of the glass is lowered from the completion of the initial pressurization to a temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise.
A pressure in the range of 10 to 200 kg / cm ² , which is lower than the pressure of the initial pressurization (intermediate pressurization), and then, while the temperature is lowered to the glass transition point or lower, 0.001 to 0.5 k
Continue to apply g / cm ² pressure (final pressure). From the viewpoint of improving the surface accuracy, the glass is 10
An intermediate pressure up to a temperature at which a viscosity in the range ^9.5 to ¹⁰¹² poise, preferably 30kg / cm ² or more and 100 kg / cm ² or less. The final pressure up to the glass transition point or lower is
It is preferably at least 0.003 kg / cm ² and at most 0.2 kg / cm ² . At this time, the time of starting the final pressurization, i.e. after completing the intermediate pressure, the viscosity of the glass is preferably 10 ^7.6 poise or higher. By terminating the initial pressurization with such a viscosity, the shape can be made substantially close to the final product by the intermediate pressurization, and the surface accuracy can be maintained or improved by the subsequent final pressurization.

Further, in a third aspect of the present invention,
From the completion of the initial pressurization, the pressure of 0.001 to 0.5 kg / cm ² is continuously applied to the formed glass while the glass is cooled to a temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise (intermediate pressurization (1)). Then, a pressure in the range of 10 to 200 kg / cm ² is applied to the formed glass, which is smaller than the pressure of the initial pressurization (intermediate pressurization (2)). The pressure of 0.001 to 0.5 kg / cm ² is continuously applied to the glass (final pressure). From the viewpoint of increasing the surface accuracy, the intermediate pressure (1) is preferably 0.003 kg / cm.
² or more, 0.2 kg / cm ² or less, intermediate pressure (2)
Is preferably 30 kg / cm ² or more and 100 kg / cm ² or less. The final pressure is preferably not less than 0.003 kg / cm ^{2 and not} more than 0.2 kg / cm ² . At this time, the time of starting the final pressurization, i.e. after completing the intermediate pressure, the viscosity of the glass is preferably 10 ^7.6 poise or higher. By terminating the initial pressurization with such a viscosity, the shape can be made substantially close to the final product by the intermediate pressurization, and the surface accuracy can be maintained or improved by the subsequent final pressurization.

By cooling the vicinity of the molding surface while applying an intermediate pressure under the above conditions, good surface accuracy can be obtained without sink marks and distortion of the surface shape, and the center thickness can be kept within the allowable tolerance. Instead, a glass molded body having a desired surface accuracy can be obtained. In addition, 0.001
The intermediate pressure (2) of ~ 0.5 kg / cm ² and the final pressure can be given by the weight of the upper die of the forming die, and the weight of the upper die of the forming die can be determined in consideration of this point. preferable. Furthermore, the final pressurization of the 0.001 ~0.5kg / cm ^2, it performed the glass below the glass transition point to 50 ° C. lower temperature or higher than the glass transition point, at the same time the cycle time when the obtained good accuracy It is preferable from the viewpoint that it is not prolonged.

According to the conditions of the first aspect of the present invention,
With a relatively small glass molded body (having a diameter of about 20 mm or less), a molded body having Newton's of ± 2 or less and asbestos of 0.5 or less can be easily obtained. Examples of the relatively small glass molded body include a biconvex lens and a meniscus lens. According to the conditions of the second and third aspects of the present invention,
Relatively large glass molding (diameter about 20-30mm)
Even easily, Newton is within ± 2,
In addition, a molded article having a surface accuracy of less than 0.5 ass is obtained. Examples of the relatively large glass molded body include a convex lens having a diameter of more than 20 mm, a biconcave lens, and a lens having a large difference between the wall thickness and the edge thickness.

In the first aspect of the present invention, the center thickness of the heat-softened glass material is set to a tolerance of ± 0.03 mm.
Is preferred from the viewpoint of keeping the center thickness of the final product within an allowable tolerance. In the final pressurization, the pressure is reduced at once, and the glass has high viscosity (about ^107.6 poise or more).
This is because only about m can be deformed under pressure.
In the second and third aspects of the present invention,
Initially pressing the center thickness of the heat-softened glass material within the range of 0.03 mm smaller and 0.15 mm larger than the center thickness of the final product, and then applying intermediate pressure, the center thickness of the final product can be obtained. It is preferable from the viewpoint of keeping within the allowable tolerance. That is, in the intermediate pressurization, the pressure is reduced at once, and the glass has a high viscosity (about 10 ^7.6 poise or more).
Since the pressure can be deformed only to a degree, it is easy to set the final center thickness within the tolerance ± 0.03 mm.

In the initial pressing and the intermediate pressing, the initial pressing of the heat-softened glass material is 0.03 mm smaller than the center thickness of the final product and a desired center thickness within a range of 0.15 mm larger. As described above, the pressing is stopped by means for stopping the pressing, and the intermediate pressing is started before or simultaneously with the stop of the initial pressing. Thereby, the center thickness of the final product is obtained, and the pressurization is performed continuously between the initial pressurization and the intermediate pressurization, so that the surface accuracy is not impaired, which is preferable. When a desired center thickness is obtained by an external stopper mechanism or the like and further intermediate pressurization is performed, the pressurization is interrupted for a moment, so that it tends to be difficult to obtain good surface accuracy. The initial pressurization and the intermediate pressurization can also be performed by a double cylinder mechanism. In the first to third aspects, the initial pressurization is a pressure applied to the mold, and this pressure is applied to the glass material until it is stopped by an external stopper mechanism or the like. In the intermediate pressing and the final pressing, the predetermined pressure is applied to the glass material during the pressing.

The glass molded product which has been molded under pressure as described above and then cooled is released from the molding die after the temperature in the vicinity of the molding surface becomes equal to or lower than the glass transition temperature of the glass material. When the temperature becomes equal to or lower than the glass transition temperature, viscous flow of the glass does not occur for a short time, and the glass may be regarded as substantially solidified. As a result, the glass molded body is not deformed after the mold release, and a good surface accuracy is obtained. It is preferable to release the glass molded body immediately after the final pressurization is completed. As mentioned above, 0.001-0.5kg / cm
It is preferable that the final pressing of ² is performed up to a temperature not higher than the glass transition point and lower than the glass transition point by 50 ° C. or higher. Therefore, it is appropriate that the mold release of the glass molded body is also performed in the above temperature range.

For releasing the molded glass, it is preferable that after the temperature of the molded glass is lowered to the glass transition point or lower, the molded glass is released from the upper mold, and then removed from the lower mold. This is because when the mold is released from the lower mold, the molded glass adhered to the upper mold falls after the upper mold and the lower mold separate from each other, causing damage to the glass molded body and stopping the apparatus. Furthermore, it is preferable to set the upper mold temperature lower than the lower mold temperature at the time of removing the molded glass from the molding die, from the viewpoint of preventing sticking of the molded glass to the upper mold. More specifically,
It is appropriate to set the upper mold temperature 5-20 ° C. lower than the lower mold temperature.

The mold used in the molding method of the present invention is not particularly limited. Further, for heating the mold, a resistance heater, a high-frequency heater, an infrared lamp heater, or the like can be used. In particular, from the viewpoint that the recovery time of the mold temperature is short, a high-frequency heater and an infrared lamp heater are preferable. Further, the cooling of the molding die can be performed by a power cut cooling or a cooling gas flowing through the inside of the molding die.

For the molding method of the present invention, for example, a molding die 1 as shown in FIGS. 1 and 2 can be used. FIG.
Medium, Mold 1 is upper mold 2, lower mold 3, sleeve 4, upper mold 5
, 6, lower mold 7, 8, upper mold lowering stop ring 9 and spring 1
0 and a push rod 11 for second pressurization (intermediate pressurization). Examples of the upper mold, the lower mold, and the sleeve include cermets of silicon carbide, silicon, silicon nitride, tungsten carbide, aluminum oxide and titanium carbide, and diamond, heat-resistant metals, precious metal alloys, carbides, nitrides on these surfaces. A material coated with a ceramic such as a material, a boride, and an oxide can be used. In particular, after a silicon carbide film is formed on a silicon carbide sintered body by a CVD method and processed into a finished shape, amorphous and / or crystalline graphite such as an i-carbon film is formed by an ion plating method or the like. Preferably, a carbon film formed of a single component layer or a mixed layer of diamond is formed. The reason is that even if the molding temperature is relatively high,
This is because fusion does not occur and the mold can be easily released at a relatively high temperature because of good releasability. The upper and lower molds and the ring can be made of, for example, metal, and the spring can be made of ceramics. Further, the molding die 1 is mounted in a press device in which a high-frequency coil is arranged, and molding is performed.

The temperature and pressurization conditions of the molding method of the present invention will be further described with reference to FIG. 4 for the case where the molding apparatus shown in FIG. 2 is used, taking the second embodiment of the present invention as an example.
In FIG. 4, the left vertical axis indicates temperature, the right vertical axis indicates pressure, and the horizontal axis indicates time. The temperature of the glass material is such that the viscosity of the glass material is 10
Temperature corresponding to a viscosity in the range from ^{5.5 to 108} poise (preferably a temperature corresponding to 10 ^6.5 to 10 ^7.6 poises). The temperature of the preheating of the mold is such that the viscosity of the glass material is
A temperature corresponding to ⁸ to 10 ^10.5 poise (preferably, a temperature corresponding to a viscosity of the glass material of 10 ⁸ to 10 ^9.6 poise). The start of the initial pressurization P1 is started. 30-350kg /
cm ² , preferably in the range of 50 to 250 kg / cm ² . The initial pressurization is performed by raising the lower mother dies 7 and 8 with respect to the upper mother dies 5 and 6 in the mold shown in FIG. Since the glass material is a viscous material, the pressure is not actually applied while the glass material is pressurized and extended, and the pressure is a value obtained by dividing a set pressure by a sectional area of the extended lens. The initial pressurizing time is a time (from about 2 to 6) until the formed glass becomes a predetermined thickness and the upper mold 5 and the lower mold 7 come into contact with each other.
0 seconds). After the upper mold 5 and the lower mold 7 come into contact with each other, no initial pressure is applied to the glass. The temperature of the mold is maintained for 0 to 20 seconds, preferably 5 to 20 seconds after the start of the initial pressurization, and then cooling starts.
The cooling rate is 20 to 180 ° C / min (from the viewpoint of obtaining high surface accuracy). The intermediate pressurization P2 is started, for example, 5 to 20 seconds after the start of the initial pressurization. The intermediate pressurization may be started before the end of the initial pressurization. In this case, P1 + P2
Pressure is applied. However, the pressure of P1 + P2 is 30 to 350 kg / cm ² similar to the initial pressurization, preferably 5
The pressure is in the range of 0 to 250 kg / cm ² . The intermediate pressure P2 is 10 to 200 kg / cm ² (preferably 10 kg / c
m ^{2 to} 150 kg / cm ² ) and a pressure lower than the initial pressure. The intermediate pressure P2 can be reduced halfway as shown in FIG. Start of final pressurization P3. The temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise. The final pressure P3 is 0.001 to 0.5 kg / cm ² (preferably 0.1 kg / cm ² ).
003 kg / cm ^{2 to} 0.2 kg / cm ² ). The mold release temperature is 5% below the glass transition point below the glass transition point.
The temperature is 0 ° C lower or higher.

Further, the temperature and pressurizing conditions of the molding method of the present invention will be further described with reference to FIG. 5 in the case where the molding apparatus shown in FIG. 2 is used, taking the third embodiment of the present invention as an example. . In FIG. 5, the left vertical axis indicates temperature, the right vertical axis indicates pressure, and the horizontal axis indicates time. Are the same as in the second embodiment. The intermediate pressurization (1) P2 (1) is started, for example, 5 to 20 seconds after the start of the initial pressurization. Intermediate pressurization (1) P2 (1) is 0.001 to 0.5 kg / cm
² (preferably 0.003 kg / cm ^{2 to} 0.2 kg / cm ² ). The intermediate pressure (1) P2 (1) is, for example, 5 to 120
Seconds. Next, intermediate pressurization (2) P2 (2) is performed. Intermediate pressurizing (2) P2 (2) is, 10 to 200 / cm ² (preferably ^{10kg / cm 2 ~150kg / cm 2} ) in the range of, and pressure less than the pressure of the initial pressure. In addition, intermediate pressurization (2) P2
(2) can be reduced on the way as shown in FIG. Start of final pressurization P3. The temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise. The final pressure P3 is 0.001 to 0.5 kg / cm ² (preferably 0.1 kg / cm ² ).
003 kg / cm ^{2 to} 0.2 kg / cm ² ). The mold release temperature is 5% below the glass transition point below the glass transition point.
The temperature is 0 ° C lower or higher.

In the forming method of the present invention, the softening of the glass material by heating can be performed while the glass material body is floated by an air current, and the heated and softened glass material is transferred to the preheated mold. In a low-viscosity region where the glass material is deformed by its own weight, it is very difficult to prevent fusion of the glass and the jig holding the glass material during heating. On the other hand, a gas layer is formed on the surface of the jig and both surfaces of the glass by ejecting gas from the inside of the jig and floating the glass material by air current. As a result, the jig and the glass react. Without
It is possible to soften by heating. Furthermore, when the glass material is a preform, it can be softened by heating while maintaining the shape of the preform. In addition, even if the glass material is a glass gob and has an irregular shape with surface defects such as wrinkles, it is possible to adjust the shape and eliminate surface defects by floating by airflow while heating and softening. is there.

The floating of the glass material and the transfer of the heat-softened glass material to a preheated mold are described in, for example, JP-A-8-1.
No. 33758. The heating of the glass material includes a case where the glass material is heated from room temperature to a predetermined temperature, a case where a glass material of a certain temperature is further heated, and a case where a glass material already heated to a predetermined temperature is further used. For example, if the glass material is a glass gob,
A glass gob made from molten glass can also be used without cooling. According to the molding method of the present invention, it is possible to produce various glass molded articles having excellent surface accuracy. In particular, in the present invention, a glass optical element, for example, a glass lens, a prism, or the like can be given as the glass molded body. There are no restrictions on the type of glass lens, for example,
A spherical or aspherical convex lens, a meniscus lens, and the like can be given, but are not limited thereto.

[0033]

According to the present invention, a glass optical element is formed by press-molding a glass material such as a heat-softened glass preform with a preheated molding die, which can greatly reduce the cycle time required for press molding. It is possible to provide a method for molding a glass optical element having better surface accuracy. In particular, according to the method of the present invention,
It is possible to provide a glass optical element in which the number of Newtons is within ± 2 and the number of ass is within 0.5. Specifically, according to the method for manufacturing a glass molded body of the first aspect of the present invention, for example, for a biconvex lens or a meniscus lens having a diameter of 20 mm or less, Newton is within ± 2, and ass is 0.5 High surface accuracy of less than one can be obtained. Furthermore, according to the manufacturing method of the glass molded body of the second and third aspects of the present invention, for example, in addition to the above-mentioned small lens, a large convex lens exceeding φ20 mm, a biconcave lens, a difference between the wall thickness and the edge thickness. With respect to a lens having a large surface roughness, a high surface accuracy of less than ± 2 Newtons and less than 0.5 lenses can be obtained.

[0034]

EXAMPLES Before describing the examples, Table 1 shows the relationship between the temperature and the viscosity of the used barium borosilicate glass (strain point 478 ° C., transition point 514 ° C., yield point 545 ° C.). Viscosity is important because temperature varies with the type of glass.

[0035]

680 ° C. 10 ^5.8 Poise 643 10 ^6.6 618 10 ^7.3 615 10 ^7.4 596 10 ^8.0 590 10 ^8.2 578 10 ^8.7 567 10 ^9.2 558 10 ^9.7 549 10 ^10.2 543 10 ^10.7 531 10 ^11.7

Example 1 FIG. 1 shows a mold used in the example. Mold 1 is upper mold
2, lower mold 3, sleeve 4, upper mold 5, 6, lower mold 7, 8
It comprises an upper die lowering stop ring 9 and a spring 10. The upper mold, the lower mold, and the sleeve were made of silicon carbide, and the molding surfaces of the upper and lower molds were covered with a carbon-based thin film. The upper and lower molds and the ring are made of metal, and the spring is made of ceramics.

Barium borosilicate glass (transition point 514)
An example of forming a meniscus lens (convex surface is spherical and concave surface is aspherical) with a press outer diameter of 15 mm is described with reference to FIG. A preform free of surface defects hot-formed into a marble shape was prepared at 643 ° C. (glass viscosity of 1
0 ^6.6 poise) and transferred by a suction pad (not shown) to a lower mold at about 567 ° C. (temperature corresponding to a glass viscosity of ^109.2 poise) below the molding chamber (FIG. 3a). . Immediately, the lower mold is raised and pressing is started at a pressure of 100 kg / cm ² . FIG. 3c shows the start of the press.
FIG. 3d shows a state during the pressing, and FIG. 3e shows a state after the pressing. At this time, the upper mold and the lower mold collide, and the center thickness of the lens is determined. The sleeve, which has been lowered by the force of the spring, is pushed up to the state shown in FIG. 3E. At this time, the outer diameter of the pressed product is slightly larger than the outer diameter of the upper mold forming surface, and does not hit the sleeve because the structure of the sleeve is as shown in the figure. The sleeve is fitted with the upper mold and the lower mold with a narrow clearance, and slides to prevent axial displacement of the upper and lower surfaces of the lens.

Next, the mold and the molded lens are cooled at a cooling rate of 70 ° C./min until the temperature becomes below the glass transition point. At this time, the upper mold follows the shrinkage of the glass, and is cooled while only the own weight of the upper mold (pressure of 0.005 kg / cm ² ) is applied. That is, during cooling, contact between the upper surface of the lens and the upper mold is maintained. As a result, the lens after releasing has good surface accuracy. Here, the lower mold was lowered at 500 ° C. to release the mold. This is shown in FIGS. 3f and 3g. At the moment when the lower mold is slightly lowered, since it has a meniscus shape, it is easily released from the lower mold and adheres to the upper mold (FIG. 3f). At the same time as the lower mold is lowered, the sleeve is lowered by the force of the spring, and the step of the sleeve hits the upper end of the pressed product, pushing the lens downward. At this time, the upper mold slightly descends, but further lowering is stopped by the lower surface of the upper mold flange hitting the holder. As a result, the lens is released from the upper surface and falls on the lower die (FIG. 3g). The lower mold is lowered to below the molding chamber, and the lens is taken out with a suction pad (not shown). The removed lens may be subsequently annealed as needed. The obtained lens had high surface accuracy, good surface quality, and good eccentricity after centering. Table 2 shows the surface accuracy.

Using a preform polished to a spherical shape and a shape similar to the shape of the final product, only the pressing start temperature
And the temperature of the glass viscosity corresponding to 10 ^6.3 poise and 10 ^7.3 poise, respectively, a molding condition change some other condition is a result of the press in the same manner as described above, satisfactory results were obtained, respectively. Table 2 shows the molding conditions and results.

[0040]

[Table 2] Temperature: ° C, Viscosity: Poise, Initial pressure release temperature: Temperature at which only the upper mold's own weight is applied

Example 2 The outer diameter of the press was 30 mm, the mold was slightly larger, and a hole was formed in the center of the upper part of the upper mold for the second pressurization. Except that a second pressing rod 11 made of a material is arranged, the structure is the same as that of the mold shown in FIG. 1 of the first embodiment (FIG. 2). In this embodiment, the preform and the mold are separately heated. The preform is floated on a split-type floating plate that blows out gas from the lower part, and is softened by heating (Japanese Patent Application Laid-open No.
-133758). The floating plate was transported immediately above the lower mold, quickly opened right and left, and the softened preform was dropped on the lower mold at a predetermined temperature. Immediately raise the lower mold into the molding chamber, and
It was pressed at a pressure of 0 kg / cm ² . Immediately after the upper and lower molds collided, cooling was started at a cooling rate of 30 ° C./min, and a second pressurization was performed at a low pressure (40 kg / cm ² ) by pressing the center with a push rod. The viscosity of the glass during cooling is from 10 ^9.5 to 10 ¹²
The second pressurization is released between the poises, and the pressure applied to the glass is limited to the upper mold's own weight (0.007 kg / cm ² ). The glass is cooled to a temperature below the glass transition point, and then released in the same manner as in Example 1. Typed and removed. Table 3 shows the molding conditions and physical properties of the examples.

[0042]

[Table 3] Temperature: ° C, Viscosity: Poise, Pressure release temperature: Temperature at which only the upper mold's own weight is used

As in Example 1, the preforms used in 2 and 3 were hot-formed into a marble shape without surface defects. For No. 1, a spherical preform ground with diamond of # 800 was used, but the grain of the preform was removed by heating the preform, and the surface quality after pressing was good, being unchanged from a few. The expansion by the second pressurization after the initial pressurization is slight, so the center thickness is stable within the specifications,
In the viscosity region at the initial stage of cooling, a low pressure was maintained, and in the viscoelastic region, only the upper mold's own weight was used so that the upper mold followed the shrinkage of the glass and maintained contact.
Despite being a larger lens than, high surface accuracy was obtained. It should be noted that even if the cooling was started simultaneously with the start of the pressing, the surface accuracy was obtained. The release was good by the same mechanism as in Example 1. The obtained lens is used after annealing. Immediately after releasing the mold and taking out the lens, the mold temperature is recovered and the next molding is performed. In this method, continuous molding can be performed with a very fast cycle time.
In the case where the lens becomes larger and the required accuracy is higher, it may be better to release the mold after lowering the temperature to below the strain point (478 ° C. for the present glass).

Example 3 In the same manner as in Example 2, a meniscus lens having an aspherical surface whose upper surface is almost flat was pressed. When it is close to a plane, the releasability from the upper mold is slightly deteriorated, and it is necessary to lower the release temperature slightly under the same conditions as in Example 2. Lowering the release temperature increases the cycle time. Therefore, there is a method of strengthening the spring, but here, a method of providing a temperature difference between the upper and lower molds is also used. The average temperature of the upper and lower molds was almost the same as in Table 2 of Example 2, and the temperature of the upper mold was lower by about 10 ° C. than that of the lower mold. As a result, the adhesiveness of the upper mold at the time of pressing becomes relatively inferior to that of the lower mold, so that the mold was favorably released from the upper mold and could be easily taken out from the lower mold. When the temperature difference between the upper and lower sides exceeds 20 ° C., the surface accuracy deteriorates. Further, when the spring was removed by providing a temperature difference between the upper and lower parts, a release failure from the upper mold occurred.

Example 4 Barium borosilicate glass (transition point: 514 ° C., yield point: 545)
° C) was formed into a biconvex lens having a press outer diameter of 15 mm or a convex meniscus lens having a press outer diameter of 22 mm using a preform having no surface defects hot-formed into a marble shape in the same manner as in Example 1 or 2. However, Table 4 (first embodiment), Table 5
The molding conditions were as shown in (second embodiment) and Table 3 (third embodiment). As a result, the surface precision of the obtained glass molded article was within ± 2 Newtons, 0.5 or less ass, and no defects such as cans and cracks were found.

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

[Brief description of the drawings]

FIG. 1 is an explanatory view of a molding die used in a molding method according to a first embodiment of the present invention.

FIG. 2 is an explanatory view of a molding die used in molding methods according to second and third embodiments of the present invention.

FIG. 3 is an explanatory view of an embodiment of a molding method of the present invention using the molding die shown in FIG.

FIG. 4 is an explanatory diagram of a time series of a temperature and a pressurizing condition of the molding method (second embodiment) of the present invention.

FIG. 5 is an explanatory diagram of a time series of a temperature and a pressurization condition in a molding method (third embodiment) of the present invention.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Saito 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Inside Hoya Corporation

Claims (10)

[Claims] 1. A glass material having a viscosity in the range of 10 ^5.5 to 10 ⁸ poise,
⁸ to 10 ^10.5 poise viscosity mold (however,
(The temperature of the glass material to be formed is higher than the temperature of the forming die), and a step of forming by pressing at an initial pressure; A method for producing a glass molded body including a step of removing glass from a molding die, wherein a pressure of 0.001 to 0.5 kg / cm ² is applied to the molded glass during the temperature reduction from the completion of the initial pressurization to the glass transition point or lower. A method for producing a glass molded body, characterized by continuously adding. 2. A molding glass material having a viscosity in the range of 10 ^5.5 to 10 ⁸ poise,
⁸ to 10 ^10.5 poise viscosity mold (however,
(The temperature of the glass material to be formed is higher than the temperature of the forming die), and a step of forming by pressing at an initial pressure; A method for producing a glass molded body comprising a step of removing glass from a molding die, wherein the glass is cooled to a temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise from the completion of the initial pressurization. A pressure in the range of 10 to 200 kg / cm ² , which is lower than the pressure of the initial pressurization, is continuously applied, and then, while the temperature is lowered to the glass transition point or lower, 0.001 to 0.5 kg / cm ^{2 with} respect to the formed glass.
A method for producing a glass molded body, characterized by continuously applying pressure. 3. A molded glass material having a viscosity in the range of 10 ^5.5 to 10 ⁸ poise,
⁸ to 10 ^10.5 poise viscosity mold (however,
(The temperature of the glass material to be formed is higher than the temperature of the forming die), and a step of forming by pressing at an initial pressure; A method for producing a glass molded body comprising a step of removing glass from a molding die, wherein the glass is cooled to a temperature at which the glass exhibits a viscosity in the range of 10 ^9.5 to 10 ¹² poise from the completion of the initial pressurization. 0.001 continue applying a pressure of ~0.5kg / cm ^2, then a range of 10 to 200 / cm ² on the molding glass, continues to apply the pressure less than the pressure in the initial pressure, then lowered to below the glass transition temperature Between 0.001 and 0.001
A method for producing a glass molded body, comprising continuously applying a pressure of 0.5 kg / cm ² . 4. 0.001 to 0.5 kg / cm ² for molded glass
2. The pressure of the mold is given by the weight of the upper mold.
4. The production method according to any one of items 3 to 3. 5. An initial pressurization of the glass material to be formed is 30 to 35.
The method is carried out at a pressure of 0 kg / cm ² and is completed when the glass material to be formed becomes formed glass having a predetermined thickness.
5. The production method according to any one of 4. 6. below the glass transition point and below the glass transition point
The production method according to any one of claims 1 to 5, wherein the pressure is released from the molded glass at a temperature equal to or lower than 50 ° C and the mold is released. 7. The method according to claim 1, wherein the temperature of the molded glass is lowered to a glass transition point or lower, and then the molded glass is released from the upper mold and then removed from the lower mold. 8. The method according to claim 1, wherein the upper mold temperature is set lower than the lower mold temperature at the start of the initial pressure molding.
The production method according to the paragraph. 9. The method according to claim 1, wherein the upper mold temperature is set lower than the lower mold temperature when the molded glass is removed from the mold.
9. The production method according to any one of 8. 10. The production method according to claim 1, wherein the glass molded body is a glass optical element.