JP2016104678A - Method for manufacturing optical glass molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical glass molding, capable of obtaining an optical glass molding extremely low in poor burning and devitrification and contributing even to extension of the lifetime of a thermal resistance softening plate and the reduction of consumption energy (electric power, etc.) in a softening furnace.SOLUTION: The method for manufacturing an optical glass molding comprises softening a glass gob and press-molding the glass gob. The glass gob is softened in a state placed on a thermal resistance softening plate including metal having a melting point of 1300°C or more.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an optical glass molded product.

  In general, the lenses constituting the optical system generally include a spherical lens and an aspheric lens. Many spherical lenses are manufactured by grinding or polishing a glass material or by cold working a glass molded product obtained by reheat press molding.

  Optical glass reheat press molding is performed after the glass material is reheated and softened. Optical glass molded products are often produced using direct press molding or precision press molding in addition to reheat press molding. In particular, the manufacturing method using reheat press molding maintains a certain level of quality. Since the glass gob can be press-molded in a state, it is useful as an optical molded product such as a lens.

  For example, in Patent Document 1 (paragraph 0058, Example 2), optical glass is ground and polished to produce a glass material for press molding, and then boron nitride powder is uniformly applied to the surface of the press molded glass material. It is described that it is placed on a heat-resistant softening dish, placed in a heat softening furnace, heated, introduced into a press mold, pressed, annealed, ground and polished to obtain a lens.

JP 2012-229135 A

  In reheat press molding, a glass gob is produced by grinding and polishing a plate-like glass or glass block product in accordance with a target weight such as a final lens shape. Then, the glass gob is loaded on a heat-resistant softening dish, put into a heating and softening furnace, and after heating and softening the glass gob, the glass gob is transferred to a reheat press mold formed for each product, and reheat press molding is performed. .

  Here, in a glass heating mechanism called a softening furnace, the glass gob is placed in a heat-resistant softening dish, the temperature in the softening furnace is increased, and the glass gob is heated and softened. As the heat-resistant softening dish, a heat-resistant softening dish made of diatomaceous earth or a ceramic material (sometimes referred to as “molding dish”) is used.

  However, these heat-resistant softening dishes are chipped and cracked by being used multiple times, so that the deterioration is remarkable and the strength is not sufficient. Moreover, if reheat press molding is performed with the fragments generated when these heat-resistant softening plates deteriorate and cracked, the defective baking occurs.

  In addition, the heat conductivity of these heat-resistant softening dishes is low, and it may take a long time for the glass gob to be heated to a temperature suitable for the press. There is a disadvantage that it is likely to occur.

  In addition, if energy consumption (electric power, etc.) in the softening furnace can be further reduced, it is advantageous in terms of reducing environmental burden and cost.

The present invention aims to solve such problems.
That is, an object of the present invention is to obtain an optical glass molded product with extremely low burn-in failure and devitrification during reheat press molding, to extend the life of a heat-resistant softening dish and to reduce energy consumption (electric power, etc.) in a softening furnace. Another object of the present invention is to provide a method for producing an optical glass molded product that contributes to the above.

  The present inventors have intensively studied to solve the above problems, and by making the heat-resistant softening dish made of a specific metal from conventional diatomaceous earth and ceramics, fragments generated from the heat-resistant softening dish itself In addition to suppressing the occurrence of poor baking due to the above, in addition to lowering the softening furnace set temperature, and succeeding in suppressing the growth of glass devitrification, the present invention was completed.

The present invention includes the following (1) to (2).
(1) A method for producing an optical glass molded article, comprising press molding after softening a glass gob,
A method for producing an optical glass molded article, wherein the glass gob is softened in a state of being placed on a heat-resistant softening dish containing a metal having a melting point of 1300 ° C or higher.
(2) The method for producing an optical glass molded article according to (1), wherein the heat-resistant softening dish is made of stainless steel.

  According to the present invention, an optical glass molded product can be obtained which has an extremely low burn-in defect and devitrification, and contributes to extending the life of a heat-resistant softening dish and reducing energy consumption (electric power, etc.) in a softening furnace. A method for manufacturing a product can be provided.

The present invention will be described.
In the present invention, a glass gob is first prepared.
A glass gob is not specifically limited, For example, a conventionally well-known thing can be used. Specifically, a glass gob can be obtained, for example, by cutting a plate-like glass or glass block product into a predetermined size using a cutting tool, and performing polishing, appearance inspection, or the like as necessary.

  The kind of glass gob is not limited to a composition system, For example, a fluoro acid type, a lanthanum type, and a silica titanium type can be used.

  A glass gob having a softening temperature of 430 to 950 ° C. can be preferably used. This is because an optical glass molded article with less baking failure and less devitrification is obtained, and further contributes to extending the life of the heat-resistant softening dish and reducing energy consumption (electric power, etc.) in the softening furnace. The lower limit of the softening temperature is preferably 430 ° C, more preferably 450 ° C, and most preferably 500 ° C. The upper limit of the softening temperature is preferably 950 ° C, more preferably 850 ° C, and most preferably 820 ° C. The upper limit is assumed.

  The size and shape of the glass gob are not particularly limited, and examples thereof include a rectangular parallelepiped shape having a side of 5 to 220 mm. Consists of two pairs of long sides of approximately 80 to 90% diagonal length with respect to the outer diameter of the glass gob, and almost equal lengths, and one short side having a length equal to or shorter than the two long sides. A rectangular parallelepiped may be sufficient. The weight is also not particularly limited, and examples include about 1 to 3700 g.

  In the present invention, when softening the glass gob as described above, if necessary, a release agent such as boron nitride powder is uniformly applied to the surface of the glass gob, and then heat resistance including a metal having a melting point of 1300 ° C. or higher. Softens while placed on a softening dish. The lower limit of the melting point of this metal is preferably 1300 ° C., more preferably 1400 ° C., most preferably 1450 ° C., and the upper limit of the melting point is preferably 2700 ° C., more preferably 3000 ° C., most preferably 3500 ° C. The upper limit is assumed.

  Moreover, it is preferable that a heat resistant softening dish consists essentially of the metal which has melting | fusing point 1300 degreeC or more. Here, “substantially” means that impurities that are unintentionally mixed in the raw material and the manufacturing process may be included, but other impurities are not included.

  The metal having a melting point of 1300 ° C. or higher is preferably a metal that does not oxidize or soften at the contact point with the metal surface and the glass gob at a softening furnace temperature of 1000 ° C.

Examples of the metal having a melting point of 1300 ° C. or higher include stainless steel, chromium, iron, nickel, tungsten, molybdenum, tantalum, platinum, and alloys containing two or more thereof.
Among these, stainless steel is preferable, and SUS304, SUS316, and SUS444 are more preferable.

  The size and shape of the heat resistant softening dish may be the same as those conventionally known. For example, the glass-shaped thing which has a hollow so that the glass gob to soften may not fall from on the softening plate | curd except a target position is mentioned.

  It is preferable that the heat-resistant softening dish is obtained by melting a raw material containing a metal having a melting point of 1300 ° C. or higher, pouring it into a mold, and casting it. This is because the strength and thermal shock resistance are improved and it is difficult to break.

When the glass gob is softened using the heat-resistant softening dish as described above, the heat-resistant softening dish is hardly deteriorated and is not easily damaged. Therefore, there are very few burn-in defects in the obtained optical glass molded product.
In addition, since the heat conductivity of the heat-resistant softening dish is higher than that of conventional diatomaceous earth, the press temperature (softening furnace set temperature) can be lowered. A glass molded product is obtained. In general, as the optical glass stays in the vicinity of the devitrification temperature region, the loss of devitrification grows, and if the size is large, it becomes defective. It is desirable to press in time. According to the present invention, the press temperature can be lowered by about 20 to 100 ° C. when compared with the conventional method.
Furthermore, it contributes to extending the life of heat-resistant softening dishes and reducing energy consumption (electric power, etc.) in the softening furnace.

  In the present invention, as described above, the glass gob is softened while being placed on a heat-resistant softening dish containing a metal having a melting point of 1300 ° C. or higher. Thereafter, it can be introduced into a press mold and reheat press molded. Further, a conventionally known process such as an annealing process, a grinding process, or a polishing process can be performed to obtain an optical glass molded product (lens or the like).

<Example 1>
After uniformly applying boron nitride powder to the surface of a fluorophosphate glass gob (glass type: S-FPL51D (made by OHARA), softening temperature: 523 ° C., weight: 57.75 g), heat resistance made of stainless steel (SUS304) It was placed on a softening dish and heated in a softening furnace to be softened, and then press-molded. As a result, an optical glass molded article free from scratches and cans and free from devitrification could be obtained.
Compared to the conventional method using diatomaceous earth as a heat-resistant softening dish, the softening temperature could be lowered by 90 ° C., and it is considered that the above-described high-quality optical glass molded product was obtained. Moreover, energy consumption (electric power etc.) in the softening furnace could be reduced by lowering the softening temperature.
Furthermore, although the same test was performed 6 times in total, the heat-resistant softening dish was not deteriorated and cracked. Therefore, there was no burning failure. There was no devitrification.

<Example 2>
After uniformly applying boron nitride powder on the surface of a lanthanum-based glass gob (glass type: L-LAM60A (Ohara), softening temperature: 693 ° C., weight: 20 g), a stainless steel (SUS304) heat-resistant softening dish It was placed on top and heated in a softening furnace for softening, and then press molding was performed. As a result, an optical glass molded article free from scratches and cans and free from devitrification could be obtained.
Compared to the conventional method using diatomaceous earth as a heat-resistant softening dish, the softening temperature could be lowered by 70 ° C., so it is considered that the above-described high-quality optical glass molded product was obtained. Moreover, energy consumption (electric power etc.) in the softening furnace could be reduced by lowering the softening temperature.
Furthermore, although the same test was performed 6 times in total, the heat-resistant softening dish was not deteriorated and cracked. Therefore, there was no burning failure. There was no devitrification.

<Example 3>
After uniformly applying boron nitride powder to the surface of a silica-titanium glass gob (glass type: S-TIH6B (made by OHARA), softening temperature: 690 ° C., weight: 9.4 g), heat resistance made of stainless steel (SUS304) It was placed on a softening dish and heated in a softening furnace to be softened, and then press-molded. As a result, an optical glass molded article free from scratches and cans and free from devitrification could be obtained.
Compared to the conventional method using diatomaceous earth as a heat-resistant softening dish, the softening temperature could be lowered by 70 ° C., so it is considered that the above-described high-quality optical glass molded product was obtained. Moreover, energy consumption (electric power etc.) in the softening furnace could be reduced by lowering the softening temperature.
Furthermore, although the same test was performed 6 times in total, the heat-resistant softening dish was not deteriorated and cracked. Therefore, there was no burning failure. There was no devitrification.

Claims (2)

A method for producing an optical glass molded article comprising press molding after softening a glass gob,
A method for producing an optical glass molded article, wherein the glass gob is softened in a state of being placed on a heat-resistant softening dish containing a metal having a melting point of 1300 ° C or higher. The method for producing an optical glass molded article according to claim 1, wherein the heat-resistant softening dish is made of stainless steel.