JPS61132525A - Forming of optical glass part - Google Patents

Abstract

PURPOSE:To obtain an optical glass part having stable optical characteristics, at a low cost, by placing a molding material of the optical glass part on a transfer table, inserting the material between a pair of molds, and molding in a nonoxidizing atmosphere. CONSTITUTION:A molding material 52 of an optical glass part is placed on a receiving part 33 of a gob table 31 having excellent releasability, clamps 38a and 39a of the transfer members 38, 39, inserted into a heating furnace 34, and heated at the transition point or thereabout, and the gob table 31 is placed on the supporting table 30. The upper and lower molds 21, 22 of the compression molding molds 20 are operated in a nonoxidizing atmosphere, the lower mold 22 is lifted along the guiding member 26 to receive and push up the material 52 with the forming face 22 of the lower mold 22, and at the same time, the upper mold 21 is lowered along the guide member 25 to effect the compression molding of the material between the forming faces 21a, 22a of the molds 21, 22. After the compression molding, the lower mold 22 is retracted downward, and at the same time, the releasing part 24 is slidden up along the outer circumference of the lower mold, the contacting surface 24a of the releasing part 24 is made to contact with the circumferential edge 51 of the glass lens, and the lens is released from the forming face 22a. Thereafter, the releasing member 23 of the upper mold 21 is lowered to release the lens from the forming face 21a.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a method for heating and softening a molding material for optical glass parts.
The present invention relates to a method for molding optical glass parts and articles by press molding using a mold.

BACKGROUND OF THE INVENTION Conventionally, many optical i-glass components such as lenses, prisms, and filters have been formed by a method that mainly involves polishing a molding material for optical glass components such as glass. However, this polishing process requires a considerable amount of time and skill, and in particular, forming an aspherical lens by polishing requires an even more advanced polishing technique and requires a longer processing time. It was difficult to manufacture optical glass parts in large quantities.

Therefore, a method for molding optical glass parts such as lenses by simply inserting and arranging a molding material for optical glass parts into a pair of molds and applying pressure has been developed and is attracting attention.

Pressure molding methods for optical glass parts generally include a reheat press method and a direct press method. In the reheat press method, the required amount of glass material, for example, as a molding material for optical glass parts that has been melted and solidified in advance is measured, heated to a predetermined temperature to soften it, and then put into a mold for molding. This is a method of molding optical glass parts by applying pressure.

However, this reheat press method did not clarify the relationship between glass viscosity and mold temperature, which caused various problems such as sticking, sink marks, and folding, making it impossible to stably mold high-precision optical glass parts. Met.

On the other hand, the direct press molding method is conventionally carried out by the method shown in WG1, and the specific method will be described below.

First, I will explain the equipment for carrying out the method.
Below the orifice 1, which is connected to a glass melting furnace (not shown), there is provided a rotary table 3 which can be rotated and stopped via a main shaft 2. Lower M for molten glass molding
4, 5, 6, and 7 are arranged at positions that equally divide the circumference into four. When the rotary table 3 is stopped, that is, before starting lens molding, the lower mold 4
The configuration is such that the opening 8 of the orifice 1 faces the upper position (lower mold on the left side in the figure), and the upper position of the lower mold 5 adjacent to the lower mold 5 is located in cooperation with the lower mold 5. A plunger 10 is provided so as to be slidable in the vertical direction. Further, between the opening 8 of the orifice 1 marked h and the lower mold 4 located below it, molten glass 9 flowing and hanging down from the opening 8 is provided.
A cutting peg 11 is provided that can be opened and closed to cut a predetermined amount. The rotary table 3 is controlled to slowly rotate and stop in 45 degree increments, and when the lower mold 4 repeats 45 degree increments and stops four times and is restored to its original position, one stroke is completed. is configured to end.

To explain the method of molding a lens using the above-mentioned apparatus, first, the molten glass 9 is made to flow down into the lower mold 4 from the orifice 1, and the molten glass 9 is cut through the cutting scissor 11 with a cutting tool. Next, the rotary table 3 is rotated 45 degrees counterclockwise in the figure and then stopped, and the lower mold 4 filled with molten glass 9 is moved to a position directly below the plunger 10. Then, in this state, the plunger 10 is moved downward, and the molten glass 9 is pressed by the S operation of the plunger 10 and the lower die 4, thereby performing press molding of the molten glass 9. In this case, the heat of the molten glass 9 is removed by the plunger 10.

After press molding, the plunger 10 is moved upward, and then the rotary table 3 is rotated 45 degrees counterclockwise in the figure and then stopped. That is, the lower mold 4 stops at the position of the lower mold 6 in the figure. At this stop position, no work is performed, and only the shape of the molded glass (molded lens) 9 is maintained.Then, the rotary table 3 is further rotated by 45 degrees, i.e., at the position of the lower mold T in the figure. The lower mold 4 is stopped, the molded lens 9 inside the lower mold 4 is pushed up from below, and the molded lens 9 is taken out, thereby completing the lens molding method.

The lens molding method is carried out using each lower mold 4, 5, 6, and 7, so that the lenses are molded continuously.

The molded lens 9 taken out from the lower mold 4 is placed in a slow cooling furnace (not shown) and cooled to room temperature while being placed under a temperature gradient to prevent distortion.

However, the direct press molding method has the following problems.

First, the molten glass must be allowed to flow down into the lower mold at a high temperature of about 10" poise, and for this purpose, the orifice 1, cutting peg 11, lower mold 4.5.6.7, plunger 10, etc. There was a problem in that each member was easily oxidized, and the lifespan of each member was shortened.

Second, to uniformly remove heat from the molten glass 9 during molding.
, the surface of the falling glass flow becomes cold when it comes into contact with the outside air, and its viscosity increases. This, combined with the relatively high falling speed of the free-falling glass flow, causes the glass flow to form a sinking flow at the inlet position and fold. There was a problem that it was easy to generate bubbles and the like.

Thirdly, since the viscosity of glass is low (high temperature), the mold surface becomes rough and easily reacts, which causes severe deterioration of the mold and prevents optical glass parts from releasing from the mold after molding. There is a problem of poor production efficiency.

Fourthly, in order to maintain the plunger 10 at a molding temperature (temperature suitable for molding), a device for cooling the plunger 10 is required, making the device complicated.

Purpose of the Invention The present invention was developed in view of the problems in the conventional molding method, and aims to prolong the life of a mold, improve mold releasability, and keep molding conditions constant. This allows us to produce optical glass parts with stable optical properties.
It is an object of the present invention to provide a method for molding optical glass parts that can be manufactured at low cost.

SUMMARY OF THE INVENTION The present invention provides a method for forming a molded material for an optical glass component that has been softened by heating to a temperature near an inflection point (hereinafter referred to as a "knick point") determined by a viscosity-temperature curve obtained by an intrusion method in a non-oxidizing atmosphere. This is a method for molding an optical glass component, which comprises inserting the optical component between molding molds heated to a temperature near the transition temperature of , and then press-molding the component.

Actual 1jff4 example The molding method of the present invention will be explained below with reference to the drawings.

Figure 4 shows an outline of the apparatus directly used for carrying out the molding method of the present invention. In the figure, 20 denotes a glass lens 50 as an optical glass component consisting of a pair of molds, an upper mold 21 and a lower mold 22. In this press molding mold, both the upper and lower molds 21.22 of the mold 20 are provided with release members 23.24 that are slidable in the vertical direction on their respective outer peripheries, and the upper and lower molds 21.22 themselves are are arranged to face each other while being supported by guide members 25 and 26, respectively, so as to be slidable in the vertical direction.

Further, both the upper and lower molds 21 and 22 are connected to drive parts (not shown) that move in opposite directions.

Further, both the upper and lower molds 21.22 are made of 13 chromium stainless steel or other ultra-hard material whose surfaces are coated with a film of chromium nitride or titanium nitride, and the mold release members 23.24 are made of The outer peripheral edge 51 of the glass lens 50 after press molding on the molding surfaces of both the upper and lower molds 21 and 22
Contact surface 23! , 24eL is made of a rigid member with low elasticity and has a woven fabric part made of carbon and glass fibers or a woven fabric part made of alumina wool.

A mounting table 30 supports a glass gob 52 as a molding material via a gob stand 31 of the glass gob 52, and is installed between the upper and lower molds 21 and 22 of the press molding mold 20.

Further, the gob stand 31 is provided with a through hole 32 in the center thereof having a diameter larger than the outer diameter of the lower mold 21 of the press molding die 20, and a glass gob 52 consisting of a stepped portion is engaged with the upper opening edge of the through hole 32. A retaining edge is formed to form a receiving portion 33 for the glass gob 52.

Further, this gob stand 31 has a glass gob 52 which is received and held in a receiving part 33 of the gob stand 31 in a heating furnace as described later.
Since the glass gob 52 is heated to a temperature near the knick point thereof, the glass gob 5 is made of a material having heat resistance that can withstand this temperature and is softened by heating.
It consists of a receiving part 33 that has a mold releasability from 2.

That is, the gob stand 31 is made of a material that does not easily wet with glass, such as BN (boron nitride) or g-gold material, which is a composite of a portion of carbon and a polymer.

34.35 is a glass lens that has been press-molded between the heating furnace of the glass gob 52 and the upper and lower molds 21 and 22 of the press-molding mold 20, which are arranged opposite to each other on the left and right sides of the mounting table 30 for the glass gob 52. 50 slow cooling furnaces.

The heating furnace 34 also includes a preliminary heating furnace 36 and a main heating furnace 3.
7, and the heating furnace 34 and the slow cooling furnace 35 are equipped with a gob stand 31 with a glass gob 52 engaged in the receiving part 33, and a holding part 38. ! ! , 3! l! A pair of conveying members 38 and 39 are installed inside the annealing furnace 35 so as to be able to move freely in the front and rear directions, and the conveying members 38 and 39 are conveyed while being held in the annealing furnace 35. rear glass lens 5
A conveying member 40 for conveying 0 to an annealing furnace 35 is installed inside the conveying member 40 so as to be movable in the front and rear directions.

In addition, the distal end portion 40α of the conveying member 40 has a receiver for receiving the glass lens 50 to be released from the mold as shown in Figure @5.
1, and a woven fabric part of carbon and glass fiber is provided in the base 41 in consideration of the wooden shape of the glass lens 50 after being released from the mold.

When molding the glass lens 50 using the molding apparatus having the above configuration while applying the molding method of the present invention, the glass gob 52 is placed while being locked on the receiving part 33 of the gob stand 31, and the glass gob 52 is placed in a pair. After carrying the glass gob 52 into the heating furnace 34 while being held between the holding parts 38α and 39α of the conveying members 38 and 39, the glass gob 52 is heated and softened through the preheating furnace 36 and the main heating furnace 37 of the heating furnace 34. As shown in the fourth figure, the gob stand 31 is placed on the upper side of the NN stand 30, and the glass gob 52 of the gob stand 31 is carried between the upper and lower molds 21 and 22 of the press molding die 20.

In connection with the conveyance of the glass gob 52, the driving parts of both the upper and lower molds 21 and 22 of the press molding die 20 start operating, and first, the lower mold 22 is moved opposite the upper mold 21 before the upper mold 21. The glass gob 52 moves upward along the guide member 26 in the direction of the glass gob 52 and is held by the holding portions 38α and 39α of the pair of conveying members 38 and 39, and is locked to the receiving portion 33 of the gob stand 31.
The gob stand 31 is stopped by the molding surface 22α of the lower mold 22.
Push up more.

In response to the upward movement of the lower mold 22 that pushes up the glass gob 52 from above the gob stand 31 while retaining the receiver on the molding surface 22α of the lower mold 22, the front planer upper mold 21 moves downward along the guide member 25, and A glass gob 52 is press-molded between the molding surfaces 21α and 22eL of both the upper and lower molds 21.22, and a glass lens 50 is molded as shown in FIG. 5α.

After the press molding of both the upper and lower molds 21 and 22, as shown in FIG. The surface 244 comes into contact with the outer peripheral edge 51 of the glass lens 50, and the molded glass lens 50 is released from the molding part 22α of the lower mold 22.

However, at this time, the glass lens 50 after molding is attached and held on the molding surface 21cL side of the upper mold 21.

Incidentally, in connection with the press-forming operation of the glass gob 52 by the cooperation of the upper and lower molds 21 and 22, the pair of conveying members 3
8.39 retreats into the heating furnace 34 and the slow cooling furnace 35, and as the mold release member 24 of the lower mold 22 releases the glass lens 50, the lower mold 22 is lowered again in advance of the upper mold 21. As shown in FIG. 5, it returns to the state shown in FIG. 4 below the mounting table 30.

Further, after waiting for the lower die 22 to move downward from the inside of the through hole 32 of the gob stand 31, the conveying member 40 is moved from inside the lehr 35.
moves forward, and the receiver provided at the tip 40G is mounted on the stand 41.
is set on the lower side of the upper mold 21, and at the same time, the mold release member 23 of the upper mold 21 slides downward on the outer periphery of the upper mold 21, and its contact surface 23α abuts the outer peripheral edge 51 of the glass lens 50. Then, the glass lens 50 is released from the molding surface 22α.

Therefore, the released glass lens 50 is stopped in the tray 41 by the carrier member 40 set on the lower side.
When the conveying member 40 returns to work, the glass lens 50 is carried into the slow cooling furnace 35 and slowly cooled, and then carried out to a predetermined position by a carrying member (not shown) to complete the molding of the glass lens 50. The glass lens 50 can be formed using the following methods.

The glass lens 50 is slowly cooled in the slow cooling furnace 35 at a temperature of 20° C./- by passing through a strain relief temperature region (a region set to a slow strain point temperature lower than the transition temperature) for 15 minutes.
The temperature was lowered to room temperature.

In addition, when molding the glass lens 50 using the molding apparatus, in particular, according to the experimental results described below, the press molding is carried out in a non-oxidizing atmosphere, for example, when molding the press mold 20. Helium, argon,
Molding is performed by creating a non-oxidizing atmosphere by introducing xenon, nitrogen, or a hydrogen-nitrogen mixed gas (
However, in the above embodiment, the glass gob 52 is a glass gob 52 having a cut surface cut by lateral pressure cutting or a molded surface preformed by a processing method such as direct pressing, in addition to nitrogen (this was carried out by injecting 5!/- of nitrogen). This is heated and softened to a temperature near the knick point of the viscosity-temperature curve determined by the penetration method, and then molded into a press molding die 20.
It has been found that the molding conditions require heating to a temperature close to the glass transition temperature.

In other words, among the viscosity-temperature curves obtained by the penetration method for each glass material in order to determine the molding temperature of the glass material in the reheat press method, heavy flint glass (SF
SOI) and barium lanthanum glass (BcLLF3)
Figure 2 α and b show the characteristics.

In the case of the penetration method, the penetration pin and holder were made of nickel metal.

As is clear from Figure 2 α and b, heavy 7-lint glass (SFSOl) with a large amount of PbO shows a knick point near 101 Hatake poise, and It was near 107・Gors.

In addition, the viscosity at the knick point differs depending on the glass material, but the viscosity range at the knick point is ha! It was within 10"・1~10?・1 poise.

Further, Table I below shows the relationship between the knick temperature of each glass material and the mold temperature.

Furthermore, Figure 3 shows the brocade characteristics of heavy 7-lint glass (SFSol) for various materials, especially 5F.
The temperature near the knick point, which is the molding temperature of SO1, is 490°C
The wetting angle at 135° or more indicates that stagnation is difficult for each material.

In other words, it has been found that due to the relationship with the molding material of the press molding die 20, if molding is performed with a viscosity near the knick point, it will not stick to the press molding die 2Q and will easily form an S shape.

In addition, when the molding temperature is raised to a temperature higher than the knick point of the viscosity-temperature curve shown in Figure 2 α, b, it becomes easy to wet, adheres to each material, and becomes difficult to release from the mold. This results in deterioration of surface quality.

In addition, at temperatures above the knick point of the viscosity-temperature curve,
It was confirmed by Galaman spectroscopic analysis that the oxygen anion state in the glass structure changes, and the reproducibility of glass forming is
It was found that the crawling in the condensed Newtonian region is superior to the shaping in the non-Newtonian region.

While applying the above molding conditions, each glass material, 5FSO1 (Fig. 5a), Ba
LF3 (Fig. 6 A), Sr1 (Cicada Fig. 6 C>, B
The interference images of the glass lens molded using K7 (@Fig. 6 d) obtained by a Fizeau interferometer are shown in the photographs shown in Fig. 6 α to d.

As is clear from these photographs, the glass lens molded under the above molding conditions was formed on the molding surface of the press molding die.
It was clear that the surface shape was larger than that, and when it was immersed in an immersion liquid with the same refractive index and examined under a polarizing microscope, no distortion was observed.

Furthermore, when 5FSO1 is applied as a molding material and molded by heating and softening it at a temperature above the knick point, 520°C, as shown in the photograph in Fig. 7 α, as shown in the photograph in Fig. When the temperature was set to 540° C., adhesion of the glass lens to the mold after molding was observed.

In addition, when the temperature of the press molding die 20 was lowered by 30° C., a depressed Fizeau interference image was obtained. This is shown in the photograph in Plant 1 and Figure 6.

Effects of the Invention According to the method for molding optical glass parts of the present invention, the molding viscosity varies depending on the type of glass material, but it is higher than 10".1 viscosity, which is higher than the molten glass of the prior art. Since the temperature is below the knick point of the temperature curve, oxygen anions in the glass structure are not activated, and the attack of oxygen anions on the mold is small.As a result, the mold surface is not strongly oxidized, which reduces the mold life. It extends life and improves mold releasability.In addition, since molding is performed at a temperature under a Newtonian fluid, optical glass parts with stable optical properties can be obtained by keeping molding conditions constant. By setting the temperature near the glass transition temperature and the heating temperature of the glass to the knick point where the viscosity is one temperature, there is no sudden structural change in the glass as a molding material, and the mold temperature is easily distorted. Since the temperature is set, optical glass components with less distortion than conventional techniques can be easily obtained.

To put the above point in another way, firstly, since it is molded using a 22-ton air fluid, the occurrence of sink marks, folds, bubbles, etc. can be prevented compared to the prior art.

Secondly, there is no need for slow cooling for a long time as in the prior art, and there is no need for much adjustment of the refractive index, making it possible to mold in a short time.

According to this method of forming the girder 3, it is not necessary to heat the girder 3 to the extent that it melts as in the prior art, and therefore, the life of the upper and lower molds and their peripheral equipment members can be extended without rapidly oxidizing them.

Fourth, as a comprehensive result, it is possible to mold in a short time,
There is no need for post-processes such as re-polishing, and the manufacturing cost can be significantly reduced, making it possible to manufacture optical glass parts with stable quality.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a molding device showing a conventional glass lens molding method, Figure 2 α, b are 5FSO1, BeLl, F3
Figure 3 is a diagram showing the temperature dependence of viscosity according to the penetration method.
The figure is a schematic diagram of the molding apparatus used in the molding method of the present invention.
Figures α and b are explanatory diagrams showing the state of press molding by the press mold and the release state of the glass lens after press molding.
Photographs showing interference images of the surface shapes of glass lenses molded with F801, BaLF3.3F8, and BK 7 molding materials, Figure 7 α and b are molding conditions that are different from those of the molding method of the present invention 1 is a photograph showing an interference image of the surface shape of a glass lens molded using 5FSO1 as a molding material. 20 Book O・Pressure molding mold 211” Upper mold 22… Lower mold 23.24… IIl type member 25.26 #Medium guide member 30… Mounting table 31, Inner, Gob table 32-・・Through hole 331" Receiving part 34@... Heating furnace 35... 50... Φ Glass lens 51... Outer periphery 52 -... Glass gop Fig. 4 Fig. 5 (,) (b) ΣGotsuni°; No change in ζ几嘗) Fig. 6 (a) ( b) (c) (d) Engraving of Figure 100 (No change in content) Figure 7 (a) (b) Procedure amendment writing method) April 25, 1985 1, Indication of case 1988 Patent Application No. 252588 No. 2, Title of invention: Method for molding optical glass parts 3, Relationship with the amended case Patent applicant address: 2-43-2-4 Hatagaya, Shibuya-ku, Tokyo, Agent: March 6, 1985 7. Contents of amendment (1) "Photograph" written in line 9 of member 24 of the specification and line 7 of the same page is corrected to read "interference pattern." (2) Correct the figures 6 and 7 of Drawing 9 as shown in the attached sheet. 8. List of attached documents (1) Amended drawings (1 copy) Voluntary writing of procedural amendments) Mr. Manabu Shiga, Commissioner of the Japan Patent Office■, Indication of the case Patent Application No. 252588 filed in 1982 2. Name of the invention Method for molding optical glass parts 3 , Relationship with the case of the person making the amendment Patent applicant address 2-43-2-4 Hatagaya, Shibuya-ku, Tokyo, Agent 6 Contents (1) "Photograph" written in line 6, line 7 of page 21, and lines 7 to 16 of page 21 of the specification, respectively, is corrected to "interference pattern." (2 ) ``Photograph,'' stated in the first line of page 22 of the specification.
Correct the interference by turning.

Claims (10)

[Claims] (1) The molding material for an optical glass component is placed on a conveyor table with good mold releasability and heated to a temperature near the inflection point determined by the viscosity-temperature curve, and then brought to a temperature near the transition temperature of the molding material. Carrying the heated optical glass component between molds and press-molding the molding material with the mold in a non-oxidizing atmosphere, and then releasing the press-molded product with a mold release member. 1. A method for molding optical glass parts, characterized in that the molding is performed by: (2) The optical glass according to claim 1, wherein the molding material is a molding material having a split surface cut by side pressure cutting or a molding surface preformed by a processing method such as direct pressing. How to form parts. (3) The molding material may be spherical, oval, cylindrical, triangular prism,
The method for molding an optical glass component according to claim 1, characterized in that a glass gob made of a rectangular parallelepiped or a cube is used. (4) The method for molding an optical glass component according to claim 1, wherein the molding material is heated to a temperature near an inflection point in a preheating section and a main heating section. (5) The molding material is once homogenized by heating to a temperature higher than the temperature near the inflection point, and then molded at a temperature around the inflection point during press molding between the molding dies. A method for molding an optical glass component according to claim 1. (6) The molding material is molded at a viscosity of 10^5^,^6 to 10^7^,^5 poise at a temperature near the inflection point. A method for molding an optical glass component according to item 1. (7) The molding die is characterized in that a molding die formed of a 13 chromium stainless steel member or other ultra-hard member coated with a chromium nitride or titanium nitride film is used. A method for molding an optical glass component according to claim 1. (8) The above-mentioned press molding is characterized in that the press molding is performed in a non-oxidizing atmosphere in which the molded part is deaerated and helium, argon, xenon, nitrogen, or a hydrogen-nitrogen mixed gas is introduced. 2. A method for molding an optical glass component according to item 1. (9) The press molding is performed by holding the mold between the molds for several tens of seconds to several minutes to eliminate glass distortion, and then releasing the mold using a mold release member. A method for forming an optical glass component as described in Section 1. (10) The mold release member is formed of a rigid member with low elasticity and has a woven fabric part made of carbon and glass fibers or a woven fabric part made of alumina wool on the contact surface with the molded product after press molding. A method for molding an optical glass component according to claim 1, characterized in that a member is used.