JPS62230633A - Forming of high-precision glass raw material - Google Patents

Abstract

PURPOSE:To carry out the forming of a high-precision glass raw material without causing the seize of the forming mold and the glass raw material, by heating a forming mold and a glass raw material to be formed at an equal temperature, forming the glass raw material maintaining a definite forming pressure according to the deformation of the glass raw material and releasing the formed article after cooling. CONSTITUTION:A glass raw material 21 preformed to a nearly spherical form is placed on a lower mold 23. The space in a forming chamber is maintained to a non-oxidizing atmosphere. The upper and the lower molds 22, 23 and the glass raw material 21 are heated at equal temperature with a heater 24. The temperature of the glass raw material 21 is set to a level to give a glass viscosity of 10<8>-10<14> poise. The molding pressure applied by the own weight of the mold is set to a proper level within 8g-3kg/ cm<2> while keeping the above temperature and the glass is molded while maintaining the above definite pressure during the time preset according to the deformation to be applied to the glass raw material 21. The forming molds 22, 23 and the formed article are cooled below the transition temperature of the glass and the molded article is released from the mold. A high-precision forming of a glass raw material 21 can be performed without causing the seize of molds 22, 23 and the glass raw material 21.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for molding a high-precision glass material.

[Prior art] As a method for molding a high-precision lens material, Patent Publication-IM
(A technique disclosed in Japanese Patent No. 56-378 is known. In this technique, the temperature of the metal mold is kept constant at a temperature below the softening point of the glass to be formed.

A fluidized softened glass is placed in this metal mold and pressure molded, and this state is held for at least 20 seconds until the temperature distribution of the molded glass becomes uniform to mold a high-precision lens material. It's a method.

According to the above method, it is possible to equalize the temperature difference between the surface layer of the lens material in contact with the metal mold and the inside, and also correct the difference in the amount of convergence wI due to the initial temperature difference by using the flow inside the glass. It can be removed, allowing high-precision lens materials to be molded.

[Problems to be solved by the invention] In the above-mentioned prior art, metal 5! Molding is carried out by maintaining the temperature of the mold at a constant temperature above the transition point and below the softening point of the glass to be formed, but when press-molding a fluid glass material under such conditions, It is a well-known fact that a glass material sticks to either the upper or lower metal mold, causing so-called seizure. This fact has also been proven by Raman spectrum analysis conducted by the applicant.

This Raman spectrum analysis will be explained in the examples of the present invention. Regarding the theory regarding the adhesion of the metal mold and glass, please refer to pages 514 to 54 of Glass Optics Handbook (#11 Used Bookstore Moriya Tabe et al. 3 authors).
It is described on page 8.

In the prior art described in Section L, the occurrence of such seizure made it difficult to release from the mold, leading to a decline in the quality of the molded product and deterioration of the optical properties.

The present invention has been made in view of the problems of the prior art described above, and is a high-precision glass material that allows the glass material to be molded with high precision without causing seizure between the mold and the glass material. The purpose is to provide a molding method.

[Means and effects for solving the problem] The present invention includes a step of heating the mold and the glass material to be formed to an isothermal state in a non-oxidizing atmosphere, and a step of heating the glass material to an isothermal heating f. Set the temperature to an arbitrary temperature within the viscosity range of 1011 to 10th poise, maintain that temperature, and set the molding pressure due to the mold's own weight to an appropriate pressure within the range of 8 g/cm2 to 2 kg/cs+2. The process consists of a process of molding while maintaining a constant molding pressure for a time set according to the amount of deformation, and a process of cooling the mold and molded body to below the transition temperature of the glass and releasing the molded body. This prevents the glass material from burning into the mold and prevents sink marks due to heat, allowing high-precision glass material to be molded.

[Example] Examples of the present invention will be described below, but before describing specific examples, first, using FIG. We will explain the results of analyzing the structural changes in using Raman spectroscopy. Figure 1 shows the wave number (cm-') on the horizontal axis and the intensity on the vertical axis.The spectrum in (a) in Figure 1 is 400℃.
The spectra were the same regardless of the temperature from room temperature to around 400°C. In addition,
The transition point temperature of the flint-based glass material was 440°C, and the eaves temperature was around 470°C. In Figure 0, the spectrum shown in (b) shows the spectrum around 440°C.
The spectrum shown in C) is around 490°C. Further, the spectrum shown in (d) is around 600°C (near the softening point), and the spectrum shown in (e) is around 650°C.

As is clear from each spectrum in the figure, from 400℃ to 60℃
In the spectrum at 0°C, peaks 1 and 2 in Figure 1
, 3.4 and second peak portions 5, 6, and 7.8 appear, but the first peak portion does not appear near 650°C,
Only the second peak portion 9 appears. 10, 11, 12° and 13.14 indicate the third peak in the spectrum near each temperature.

15.16.17 shows the first peak part 1.2,
3,4. This is a line connecting the second peak portion 5, 6.7° 8.9 and the third peak portion 10, 11, 12° 13.14.

First peak part 1.2, 3 in the spectrum at each temperature
．． When we investigated the chemical structure of 4, we found that it was a filter and had a plate-like structure. In this structural formula, since there is only one bond, it has a property that it is difficult to bond to objects, that is, it is difficult to cause seizure. or.

After examining the structural formulas of the second peak portions 5, 6, 7, and 8.9.

$ and had a chain structure. In this structural formula, there are two bonds, so it is easy to bond to things.

That is, it has the property of easily causing burn-in. In particular, in the case of the spectrum (e) at 650° C., there is only the second peak portion 9, and it can be seen that adding press pressure increases the number of collisions and promotes seizure. Furthermore, at temperatures where the transition temperature is 440°C or higher and the softening point is 600°C or lower, the intensity of the first peak portion 2.3.4 decreases, and the intensity of the second peak portion 2.3. It can be seen that the intensity at the peak portion 7°6.5 gradually increases. Therefore, in the region above the transition temperature and below the softening point, it can be determined from the Raman spectrum analysis in Figure 1 that the glass to be formed may seize against the mold, and this It has been demonstrated that the technology has the disadvantage of being susceptible to burn-in. Moreover, at high temperatures above the softening point of around 600°C, the third peak portions 10, 11, 12, 13° 1
By changing the absorption band form of 4, a complex structural change, ie, an anion-active structure with many bonds is formed.

Further, as a result of examining the wettability of flint-based glass with various materials, it was found that when the temperature reached a softening point of 600° C. or higher, the wettability of the various materials decreased as the temperature increased. The materials that are difficult to wet were carbide-monide ceramics, nitride ceramics, carbide ceramics, oxide ceramics, nickel-based alloys, cobal 7 alloys, and stainless steel.

In addition, in order to investigate the degree of seizure of various glass materials to molds in relation to the viscosity and molding pressure of various glass materials, the following experiment was conducted. That is, a mold is formed of nitride-based ceramics, the glass to be molded which has been softened by heating and the mold are heated to an isohumidity J78 (uniform temperature state) via a heater, and various materials (to be coated) are heated under isothermal heating. Glass to be molded was molded by changing the viscosity and molding pressure of the molded glass material. After molding under each condition, we air-cooled the molded product and mechanically removed it from the mold to find the appropriate molding pressure (pressure that allows mold release) that would not cause seizure for each viscosity of the various materials. I tried it. In addition, the molding pressure is
The weight of the mold is set as the molding pressure, and the material is tellurite glass.

Phosphate glass and flint crown glass were used.

The above experimental results are shown in Table f.

As shown in Table 2, the glass viscosity of various materials is 108
The glass viscosity is set in the range of ~1013 poise, and seizure due to the weight of the mold does not occur in this range of glass viscosity.
That is, the range of molding pressure for the fa type rotatable part is 8 g/cm2 to 2
kg/cm2. Also, from the results shown in the table above,
It can be seen that as the viscosity of each glass material decreases, the molding pressure during mold release also decreases. Therefore,
When molding each glass material, unless the molding pressure is set low in accordance with the decrease in the viscosity of the glass to be molded, the glass to be molded will seize on the mold. From this, when molding glass using the mold's own weight, it is sufficient to change the molding holding time depending on the viscosity of the glass to be molded.
By setting the molding retention time to be long when the viscosity is a hole, and by setting the molding retention time to be short when the viscosity is low, it is possible to reliably prevent the glass to be molded from sticking to the mold.

From the results of the Raman spectrum analysis and various experiments described above, the mold and the glass material are heated isothermally at a temperature lower than the softening point of each glass material (glass material), that is, all parts of the mold and the glass material are in an isothermal state. Under heating conditions of
It is clear that by setting the molding retention time that does not cause seizure according to the viscosity of the glass material, it is possible to mold into the desired shape and reliably prevent seizure from occurring. It is.

The magnitude of the molding pressure due to the mold weight of the mold is changed and set according to the amount of deformation (forming amount) of the glass to be molded. That is, when the amount of deformation of the glass to be molded is large, the molding pressure is set high, and when the amount of deformation of the glass to be molded is small, the molding pressure is set to be low.

If you want to change the mold self-weight to be large or small, you can adjust it by increasing or decreasing the weight attached to the mold, as shown in Figure 2.
Figure 2 shows the relationship between the deformation amount and deformation time of a flint-based glass material under isothermal heating conditions and a constant load (500 g/c layer 2). It is a graph diagram in which the amount of deformation is plotted on the axis, and the mold (
We investigated the time dependence of the amount of deformation due to the weight of the mold when it was heated to 530°C and reached an isothermal state.As shown in Figure 1, 30 minutes after reaching the isothermal state,
Deformation occurred to the extent of 0 layers. From this graph, it is possible to set the molding pressure holding time under constant load and isothermal heating depending on the degree of deformation.

FIG. 3 is a graph showing the relationship between temperature and viscosity in flint-based glass, with the horizontal axis representing temperature (Tevarging temperature 9° C.) and the horizontal axis representing viscosity. At a transition point temperature of 440°C (viscosity 1013 poise), the molded glass has the potential to change its material, but at a temperature below the transition point, for example 400°C, it cannot be formed. Around 400℃ (viscosity IQ+
If the molded product (glass lens) is removed at a temperature of 4.5 poise, a high-precision molded product that does not cause sink marks due to heat can be removed. Furthermore, as shown in the Raman spectrum (a) in Figure 1, the first peak part 1, where seizure is less likely to occur at 400°C, is much larger than the second peak part 8, so the molded product cannot be taken out at 400°C. For example, the molded product can be taken out without seizure.

Based on the above experimental results, specific examples will be described below.

FIG. 4 is a cross-sectional view showing an example of the configuration of a mold fi20 for carrying out the method of molding a high-precision glass material according to the present invention. As the glass material 21 which is the object to be molded, phosphate glass preformed into an approximate spherical shape is used. I tried molding it into a spherical shape. 24
2 is a heater disposed around the molds 22 and 23 to heat the molds 22 and 23 and the glass material 21t isothermally.

Gold for molding! 122 and 23 are made of nitride-based ceramics, and the radius of curvature of each molding surface 22 and 23 is set to 150mm and 100mm, respectively.

In addition, the molding pressure in the molding molds 22 and 23, that is, the mold 1
] The molding load due to the balls was set at 22.5 g/c2.

The glass material 21 has a diameter of 30 mm, and the curvature h of both surfaces is set to 150.5 tag and 100.5 mm, respectively, and is preformed into an approximate slope shape.

First, the preformed glass material 21 is placed on the mold 23F. The inside of the molding chamber is a non-oxidizing atmosphere using 99.9% or more nitrogen gas.

Next, through the heater 24, the J:″F mold 22°23
Then, the glass material 21 is heated to bring the lower mold 22, 23 and the glass material 21 into an isothermal heating state (all parts are at one temperature).

Ten minutes after the start of heating by the heater 24, the temperature of the glass material 21 was set to a temperature at which the viscosity was around 108 poise under isothermal heating conditions. Then, while maintaining this temperature, the glass material 21 was molded through the upper mold 22 having a molding pressure of 22.5 g/cm due to the mold's own weight. The JA type positive pressure holding time was 50 minutes. These molding conditions were set based on the experimental results described below.

Next, the molded glass material 21 was slowly cooled for 30 minutes until the temperature reached the transition point. Furthermore, at the same temperature 1
The mixture was held for 0 minutes and allowed to cool.

After cooling, the molded glass material (glass lens) 21 was taken out.

Figure 5 shows the molding conditions in press molding.The horizontal axis represents the molding time (minutes), and the vertical axis represents the viscosity (poise) of the preformed glass material 21. In the figure, the horizontal line is drawn at a viscosity of 1013! a25 indicates the transition temperature of the glass. From this figure, 1.
L: The following molding conditions are easier to understand.

The molded product (glass lens) molded under the above molding conditions and molding step 1 has a very smooth surface and no defects such as sink marks, and the curved surface of the lens surface is accurately shaped by the mold 22.
The radius of the curved surface of 23 was inverted. That is, this was verified by the above-mentioned experimental results in this example where the body weight was A.

Therefore, according to this embodiment, it is possible to mold the glass material without causing seizure in the molding die, and while reliably preventing the occurrence of sink marks due to heat. It can be molded under certain molding conditions.

As a result, a highly accurate glass lens can be obtained by press molding. Further, according to this embodiment, the glass material 21 preformed into a spherical shape is molded into molds 22 and 23 having aspherical molding portions 22a and 23a.
It has become clear that this is a particularly preferable method when molding a large-diameter aspherical glass lens. Further, in this embodiment, press molding is performed using the weight of the mold, which eliminates the need for mechanical operations and facilitates the molding operation.

In addition, in Example L, the case of phosphate glass was explained, but it is of course not limited to this case.

[Effects of the Invention] As described above, according to the present invention, it is possible to reliably prevent the glass material (1 & shaped product) from sticking to the mold during molding and demolding, and also to prevent heat It is possible to prevent the occurrence of sink marks caused by molding, and it is possible to mold a glass molded product with high precision.

[Brief explanation of drawings]

Figure 1 is a Raman spectrum analysis diagram of flint-based glass, Figure 2 is a graph showing the relationship between deformation of flint-based glass and deformation time, and Figure 3 is a graph showing the relationship between temperature and viscosity of flint-based glass. FIG. 4 is a cross-sectional explanatory diagram of an apparatus for carrying out an embodiment of the method according to the present invention, and FIG. 5 is a graph diagram showing conditions for forming phosphate glass. 21...Glass material 22.23...Molding mold 24...Heater patent applicant Olympus Optical Industry Co., Ltd. Agent On patent attorney Takeshi Nara 1 ・-' 1200 1UOLI aLXJ
l: +UIJ wave B (cm') Fig. 2 Fig. 8 (0C)

Claims (1)

[Claims] A step of heating the mold and the glass material to be formed to an isothermal state in a non-oxidizing atmosphere, and adjusting the temperature of the glass material to 10^8 to 10^1^4 poise under isothermal heating. Set the desired temperature within the viscosity range, maintain that temperature, and increase the molding pressure due to the weight of the mold to 8g/cm^2 to 2kg/cm^
The process of setting an appropriate pressure within the range of 2 and molding by maintaining that constant molding pressure for a time set according to the amount of deformation of the glass material, and cooling the mold and molded object to below the transition temperature of the glass. A method for molding high-precision glass materials, which consists of a step of releasing the molded object from the mold.