JP2000053433A - Production of glass optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of a glass optical element by which problems such as foaming in glass, melt sticking to dies, rough surface and pullout can be prevented irrespective of the kind of glass in an isothermal pressing method or an anisothermal pressing method. SOLUTION: This method includes a process (softening process) to heat and soften a glass raw material to a temp. at which the glass raw material has 105.5 to 199.5 Poise viscosity, a process (temp. controlling process) to control the temp. of the softened glass material to a temp. lower by 10 deg.C than the softening temp., and a process (molding process) to mold the glass raw material with the controlled temp. by using a press.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass optical element such as a high-precision lens which does not require grinding, polishing or the like after press molding.

[0002]

2. Description of the Related Art In recent years, a technique for press-molding a high-precision glass optical element using a precision-molded mold has been greatly advanced, and mass production of aspherical lenses and the like has been performed. The molding method can be roughly classified into an isothermal pressing method in which glass and a mold are pressed at the same temperature and a non-isothermal pressing method in which press molding is started in a state where the glass temperature is high and the mold temperature is low.

As an isothermal pressing method, for example, US Pat.
The temperature of the glass and the mold is raised to near the softening point of the glass in a non-oxidizing atmosphere described in No. 833,347, the glass is pressed by the mold at a temperature substantially equal to the mold, and the mold temperature is maintained while maintaining the pressure. There is a method of lowering the temperature to below the transition point.
Further, the method described in U.S. Patent No. 4,481,023 prepares a glass preform shape approximate to the final product, the preform and the mold to 10 ⁸ to 10 ¹² poises equivalent temperature, pressurized for a time sufficient to mold And the preform are molded at the same temperature, removed from the mold at 10 ¹¹ to 10 ¹³ poise, and subjected to precision annealing. In these isothermal pressing methods, the transferability of the mold is good and the shape accuracy is easily obtained, but the cycle time of molding is long and the productivity is not improved.

Therefore, a non-isothermal pressing method is being studied as a method for solving such a drawback of the isothermal pressing method.
For example, in the method described in JP-A-7-10556, 10 ⁷ ~
A glass material heated to a viscosity of 10 ⁹ poise is pressed with a molding die adjusted to a temperature at which the glass material has a viscosity of 10 ¹⁰ to 10 ¹² poise. In the method described in JP-A-9-48621, a glass material heated to a viscosity of 10 ⁵ to 10 ⁷ poise is molded at a temperature at which the glass material has a viscosity of 10 ⁹ to 10 ¹¹ poise. Press molding with a mold.

[0005]

SUMMARY OF THE INVENTION The present inventors have studied the suitability of using glasses of various compositions and various mold materials and found that water and hydroxyl groups on the glass surface have a very bad influence on press molding. I got the knowledge. In the isothermal pressing method, depending on the type of glass, foaming due to release of moisture easily occurs at the interface with the pressed mold. This phenomenon is particularly remarkable in phosphate glasses. Also,
This moisture oxidizes the mold made of a non-oxide material, causing fusion and rough skin. When the mold is covered with a carbon-based thin film, the carbon film is significantly attacked. In the case of a hard and brittle type material such as silicon carbide, the surface of silicon carbide is oxidized and fused with glass, and silicon carbide is locally removed (this phenomenon is called pullout). For these phenomena, the glass material to be molded was preliminarily heat-treated at 200 ° C. to remove water adsorbed on the surface, and press molding was attempted. However, there was little effect.

On the other hand, in the non-isothermal pressing method in which the glass temperature is raised and the mold temperature is lowered, the type of glass varies depending on the type of glass. Problems such as fusion of the mold, roughening of the surface, and pull-out are not perfect, but are solved to some extent. This is considered to be because some water is released from the glass surface during the softening process of the glass, and the glass is pressed with a mold at a lower temperature than the glass. However, for example, in the case of phosphate glass, the problem of foaming and the like cannot be solved even by a non-isothermal pressing method.

Accordingly, an object of the present invention is to provide an isothermal pressing method or a non-isothermal pressing method regardless of the type of glass.
An object of the present invention is to provide a method for manufacturing a glass optical element which does not cause problems such as foaming of glass, fusion of a mold, roughening of the surface, and pull-out.

[0008]

Means for Solving the Problems The present inventors removed water and hydroxyl groups near the glass surface by softening the glass at a high temperature, and then lowered the temperature to reduce the water content from the surface. It was found that the above problem could be solved by freezing and pressing in this state, and completed the present invention.

That is, according to the present invention, a glass material to be molded is made of a glass material of 10 ^5.5 to 10 ^9. A step of heating to a temperature at which a viscosity of ⁵ poise is softened (softening step), a step of controlling the softened glass material to a temperature lower than the softening temperature by 10 ° C. or more (temperature control step), and a step of controlling the temperature of the glass material. The present invention relates to a method for producing a glass optical element including a step of press molding (molding step).

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Manufacturing method of glass optical element of the present invention
The method includes a softening step, a temperature control step, and a forming step.Softening process  In the softening step, the glass material to be molded is
Material is 10^5.5-10 ^9.5Temperature at which the viscosity of Poise
(Figure 1 (a) (non-isothermal press) and (b) Temperature T during (isothermal press)
A) to soften. Preferably, the glass material is
10⁶-10⁹Softens by heating to the temperature at which poise has viscosity
I do. In addition, the glass material to be molded has a
Even if the preform is properly prepared, it flows down from the molten pipe.
The molten glass to be dropped or cut by a cutting blade
Molten glass lump, and^9.5Pore
Temperature below the temperature corresponding to the viscosity of the
(Temperature -100 ° C.) or more.
Such a molten glass lump is disclosed in, for example, JP-A-8-277.
No. 132 can be prepared.

The glass material to be molded is made of 10
^When heated to a temperature higher than the temperature at which the viscosity becomes ^5.5 poise, the glass material to be molded becomes too soft, so that it is difficult to float the glass material to be molded by airflow, and the glass material contacts and fuses with the floating plate. The danger increases. In the case of floating by an air current, a dent is formed on the surface of the glass material to be formed due to gas pressure, and a gas trap may be generated by pressing. Moreover, the the glass molding material, when the glass material is heated to a temperature above the temperature at which the viscosity of 10 ^5.5 poise, when the mold temperature lower surface accuracy is difficult to obtain, easily reacts with high mold temperature trends There is.

[0012] Softening of the glass molding material, in the case of heating at a temperature below the temperature at which the glass material is the viscosity of 10 ^9.5 poise, the glass is too hard extended by press molding (deforming) is difficult is there. Furthermore, the detachment of water and hydroxyl groups near the surface of the glass material is small, and it is difficult to obtain the effects of the present invention.

The heating and softening of the glass material to be molded is preferably performed while the glass material to be molded is floated by an air current from the viewpoint that the glass material to be molded can be softened while preventing fusion. Also, when compared to the method of heating and softening after introducing the glass material to be molded into the mold,
It is more preferable because the deterioration of the molding die due to water and hydroxyl groups detached from the glass material to be molded is small, and there is no hindrance of detachment due to contact with the molding die. A method of softening a glass material to be formed while floating it by an air current is disclosed in, for example,
The method can be performed by the method described in JP-A-259242.

The gas used for the air flow for floating the glass material is
It is preferable to select an appropriate material in consideration of the deterioration of the floating softening device and the forming device of the glass material and the prevention of contamination of the glass material to be softened. Such a gas is a gas that does not substantially react with the glass material and the molding apparatus, and is not particularly limited as long as it does not contain substances or components that contaminate the glass material. In order to prevent oxidation of the heated molding device and the like, and to thereby expand the range of selection of the material of the molding device, it is appropriate to use a non-reactive gas or a non-oxidizing gas. For example, nitrogen and the like can be mentioned. Furthermore, it is also possible to add some reducing components, such as hydrogen gas, to nitrogen or the like. Further, it is preferable to use a dry airflow as the airflow for floating the glass material to be molded, from the viewpoint of promoting the release of moisture and hydroxyl groups near the surface of the glass material in the softening step.

The flow rate of the airflow can be changed as appropriate in consideration of the shape of the outlet for blowing the airflow, the shape and weight of the glass material, and the like. Usually, a gas flow rate in the range of 0.005 to 20 liters / minute is suitable for floating the glass material. However, if the gas flow rate is less than 0.005 liter / min, the glass material may not be able to float sufficiently when the weight of the glass material is 300 mg or more. Further, when the gas flow rate exceeds 20 liters / minute, the glass weight becomes 200
This is because, even in the case of 0 mg or more, the glass on the floating jig shakes greatly, and the glass material may change to an unintended shape during heating.

Further, in the method of the present invention, the shape and shape of the glass material can be changed to a desired shape by controlling the rotation direction and the number of rotations of the heat-softened glass material. Examples of the desired shape include a spherical shape, a marble shape (a shape obtained by flattening a sphere), a disk shape, and a spherical shape.

[0017]Temperature control process  Vitreous softened by heating to a predetermined temperature in the softening step
The temperature of the material (temperature: TA) is at least 10 ° C lower than the softening temperature.
Is controlled. A temperature lower than the softening temperature by 10 ° C or more is preferable.
For example, the glass transition temperature of the glass material is 100
At higher temperature (TB) than lower temperature (Tg-100 ° C)
is there. The heated and softened glass material is preferably
Temperature is controlled to be at least 15 ° C lower than the softening temperature.
You. This freezes the condition of reduced moisture from the surface
Let it. Further, the cooling temperature is higher than (Tg-100 ° C).
When the temperature drops to room temperature, moisture will
Adsorbs, but there is no such problem and cycle tie
This has the advantage of preventing the system from becoming unnecessarily long.

In the temperature control step, performing the temperature control (cooling) of the glass material to be molded while floating the glass material by an air current can cool the glass material to be molded while preventing fusion. Preferred from a viewpoint. In addition, when compared with the method in which the glass material to be molded is heated and softened after being introduced into the molding die, there is no deterioration of the molding die due to water or hydroxyl groups detached from the glass material to be molded, and water and hydroxyl groups are reduced due to contact with the molding die. It is more preferable because it does not prevent the elimination. The method of cooling the glass material to be formed while floating it by an air current can be performed by, for example, the method described in JP-A-8-259242, similarly to the above-described softening step. Further, it is preferable to use a dry airflow as an airflow for floating the glass material to be formed.

The glass material to be formed, which has been temperature-controlled (cooled) in the temperature control step, is then subjected to press molding with a mold having a temperature equal to or lower than the temperature of the glass material. The former is an isothermal press and the latter is a non-isothermal press. Non-isothermal press Non-isothermal press [Fig. 1 (a)]
In the temperature control step, the glass material to be formed is cooled to a temperature (TB) suitable for starting press forming. By cooling to a temperature (TB) suitable for starting press molding, there is an advantage that a state in which moisture is reduced from the surface can be frozen. The temperature of the glass material to be cooled in the temperature control step is preferably, for example, 10 ° C. or more higher than the temperature of the forming die suitable for starting press forming. The cooled glass material to be formed (temperature: TB) is softened and cooled, preferably while floating with gas, as described above, and is transferred from a floating device to a forming die (TM which is lower in temperature than the glass material to be formed) for forming. Then, press molding is started. In the case of a non-isothermal press, since the temperature of the mold is lower than the temperature of the glass material, there is an advantage that the cycle time of molding can be shortened. When a split-type floating plate is used to transfer the glass material to be molded to the molding die, it is preferable to provide a mechanism for preventing uneven wall thickness at the time of falling during floating.

[0020]In case of isothermal press  In the case of an isothermal press [Fig. 1 (b)], in the temperature control process
After the glass material is cooled to near the strain point,
Before starting molding, heat up the temperature and then start press molding.
Start. When heating and raising the temperature before press molding starts,
Heating and heating should not raise the glass material to be formed by airflow.
Or transfer the glass material to the mold
Can be done after. Cool to near the strain point.
With this, it is possible to freeze the state where the moisture has been reduced from the surface
There is a point, and it is necessary to heat up before starting press molding
Therefore, there is an advantage that surface accuracy is easily obtained. In addition, gala
Cool the material to a temperature below the strain point and allow it to solidify
Transfer to the mold with the pad and raise the temperature again with the mold
You can also press. In this case, the center of the mold
Easy setting and easy surface accuracy
There is a point. Either method should be adopted for isothermal press
Can also.

The temperature of the mold at the start of press molding
Means that the viscosity of the glass material to be molded is 10 ^7.3-10¹²Po
Preferably, the temperature is equivalent to as. Mold temperature
If the viscosity of the glass material to be molded is 10^7.3Poise
If the temperature exceeds the applicable temperature, the mold and glass may react with each other.
The skin becomes rougher and foams easily
The problem that the mold life is shortened is caused. Further
In addition, it also causes an increase in molding cycle time. Success
When the temperature of the mold is 10 and the viscosity of the glass material is 10¹²Pore
If the temperature of the glass material to be formed is lower than the temperature
If it is relatively low, the glass material
It is difficult to extend (deform) by press molding
Problem. The temperature of the glass material to be molded is relatively
If it is high, the glass surface cools rapidly, and surface accuracy is obtained.
If the edge is too thin,
You. In the case of a non-isothermal press, the viscosity of the glass
Is 10^5.7-10⁸Temperature equivalent to poise,
The molding die has a viscosity of 10⁸-10
¹²Preferably, the temperature is equivalent to poise.

In the above press molding, the heat-softened glass material is placed in a mold, for example, from 0.5 to 240
Initial pressurization can be performed for seconds. This initial pressurization is 0.5
If the time is less than seconds, elongation of the glass is generally insufficient, and it is often difficult to obtain a glass optical element having a desired shape. In addition, the initial pressurization may be lengthened to improve surface accuracy and the like, but if it is too long, the cycle time cannot be shortened, and the life of the mold may be adversely affected. On the order of seconds. Preferably, 2-120
Range of seconds. The molding pressure can be appropriately determined in consideration of the temperature of the glass material, the temperature of the molding die, and the like, and is usually set to a pressure in the range of 30 to 300 kg / cm ² .

After the start of press molding, the temperature of the mold is cooled to the glass transition point of the glass to be molded or lower, and then the mold is released. More specifically, after molding, for example, the vicinity of the molding surface of the mold is cooled 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, it is preferable to cool the vicinity of the molded surface at a rate of 20 to 180 ° C./min, preferably 50 to 150 ° C./min. .

After the start of press molding, the temperature of the mold is cooled to the glass transition point or lower of the glass to be molded, and then the mold is released, whereby a glass optical element having excellent surface accuracy can be obtained. When the mold is released at a temperature higher than the glass transition point, sink marks are generated, and it becomes difficult to obtain surface accuracy. Further, since the mold and the glass optical element are in close contact with each other, it is not easy to release the mold at a temperature exceeding the glass transition point. It is more preferable that the release is lowered to near the strain point. However, lowering the temperature further lowers the cycle time only.

According to the production method of the present invention, an optical element having good physical properties can be produced regardless of the type of the glass material to be molded.
Even in the case of phosphate glass containing a large amount of water, foaming and oxidation of the mold can be prevented.

In the production method of the present invention, particularly, the glass material to be molded is 10 ^{5. By} heating to a temperature at which the viscosity becomes ⁵ to ^9.5 poise and softening, moisture and hydroxyl groups near the surface of the glass material are reduced, and then the temperature of the glass material is lowered by 10 ° C. or more to reduce the temperature. By starting press molding with a mold having a temperature corresponding to 10 ^7.3 to 10 ¹² poise, the viscosity of the glass material is cooled to a temperature equal to or lower than the glass transition point of the glass, and then the mold is released. In any of the isothermal pressing method and the non-isothermal pressing method, and regardless of the type of glass,
A glass optical element can be manufactured without causing problems such as foaming of glass, fusion of a mold, roughening of the surface, and pull-out.

[0027]

EXAMPLE 1 _P 2 ₀ 5, PbO, in phosphate glass mainly composed of _Nb 2 _{O 5,} refractive index Nd1.80518, Abbe number Nyudi25.5, transition point 466 ° C., yield point 511 ° C. The following describes an example in which a glass having the above shape is formed into a convex meniscus lens having an outer diameter of 15 mm and an aspherical surface on one side by using a mold having a base made of silicon carbide and a hard carbon film coated on the surface. Table 1 shows the relationship between the viscosity of the phosphate glass and the temperature.

[0028]

[Table 1]

The inside of the apparatus was set to a nitrogen gas atmosphere. As the material to be molded, a material having a plano-convex shape by grinding and polishing in a cold state and a material having a marble shape by hot forming were prepared. In order to reduce the moisture and hydroxyl groups near the surface of the glass material to be molded by heating and softening the glass material to be molded, it is necessary to prevent contact and fusion with a member supporting the glass material to be molded. Here, a method similar to the method disclosed in JP-A-8-133758 was adopted.

A non-oxidizing gas (nitrogen gas) is blown from below the split-type floating plate made of high-density carbon, and the glass material to be formed is floated by an air current to be heated and softened. Removing the hydroxyl group,
Reduced. Thereafter, the split-type floating plate is transferred to the lower mold of the forming mold, the glass material to be formed is lowered to a predetermined temperature, and the state in which moisture and hydroxyl groups are released from the vicinity of the glass surface is frozen, and then the split-type floating plate is removed. Opening right and left, the glass material to be molded was dropped on a mold at a predetermined temperature, and immediately press-molded. Table 2 shows the conditions of the example. Press molding was performed 100 times in each example, but no bubbles were generated at the contact interface with the molding die, and there was no abnormality in the hard carbon film.

[0031]

[Table 2]

On the other hand, when the glass material to be formed is heated and softened and then immediately subjected to press forming without lowering to a predetermined temperature, small bubbles are slightly generated at the interface, depending on the forming conditions. Roughness due to erosion of the hard carbon film was observed in press molding, and fusion occurred in about 100 press moldings. In addition, when using another apparatus, the temperature of the glass material to be formed is raised together with the forming die, and when so-called isothermal pressing is performed, remarkable bubbles are generated at the interface, and the hard carbon film is fused by erosion of the hard carbon film by several times of press forming. There has occurred.

Example 2 A mold was the same as that of Example 1 except that the base was made of a cemented carbide without a metal binder and the surface was coated with a Pt-Ir-Rh-Au alloy thin film. As a result of press molding under each molding condition, good results were obtained as in Example 1. The comparative example is good in that no erosion is observed as compared with the comparative example described in Example 1, but bubbles are generated although the bubbles are slightly reduced.

Example 3 The same glass as in Example 1 was pressed into the same shape. In this embodiment, as a glass material to be molded, a glass material cold-polished to a surface shape similar to the final product is used. Instead of floating during heating and softening, the outermost periphery of the glass material to be molded is a ring-shaped holder ( The surface of the high-density carbon is treated with glassy carbon and then softened by heating, set in a lower mold with a ring-shaped holder,
Press molding was performed. Table 3 shows the conditions of the example. Other conditions were the same as in Example 1, and the same results as in Example 1 were obtained.

[0035]

[Table 3]

Example 4 Barium borosilicate glass having a refractive index of nd1.58913,
An example is shown in which a glass material having an Abbe number νd 61.3, a transition point of 514 ° C., and a deformation point of 545 ° C. is prepared, and a hot-formed marble-shaped glass material is prepared, and a convex meniscus lens having an outer diameter of 15 mm is formed. Table 4 shows the relationship between the viscosity and the temperature of this glass.

[0037]

[Table 4]

The inside of the apparatus was set to a nitrogen gas atmosphere containing 2% of hydrogen. The mold used was silicon carbide whose surface was produced by the CVD method. Floating plate with high-density carbon surface treated with glassy carbon (unlike Example 1, not split type)
, A non-oxidizing gas (nitrogen gas containing 2% of hydrogen) was jetted from below, and the glass material to be molded was floated by an air current and softened by heating (conditions are shown in Table 5). Thereafter, the glass material to be molded is cooled to a temperature lower than the glass transition point (in this embodiment, to a strain point of 478 ° C.), and the glass material to be molded is molded with a suction pad in which the surface of high-density carbon has been subjected to glassy carbon treatment. The glass material was transferred to a mold preheated to a temperature corresponding to the strain point. Next, the temperature of the glass material to be molded was rapidly raised together with the forming die to a predetermined press temperature shown in Table 5, and press molding was performed under predetermined conditions shown in Table 5. As a result of performing press molding 10 times under each condition, no pull-out occurred under any condition, and the appearance quality of the lens was good.

[0039]

[Table 5]

On the other hand, in the comparative example, the same operation was performed without heating the glass material to be molded to the softening temperature but to the strain point of 478 ° C. Although there are differences depending on the conditions, pull-out has already occurred in one press molding under each condition, and many pull-outs have occurred in ten presses.

Example 5 The surface of the mold of Example 4 was coated with a hard carbon film and used. Others are the same as the fourth embodiment. 2,000 for each condition
As a result of the first press molding, no pull-out occurred under any of the conditions, and the appearance quality of the lens was good. On the other hand, in the comparative example, although different depending on the conditions, the carbon film was eroded by about 1000 times of press molding, and pull-out occurred.

Example 6 A case where the glass material to be molded is a molten glass gob will be described below. The split type floating plate 1 shown in FIG. 2 has a trumpet-shaped concave portion 3 and a central lower portion of the concave portion 3 (the bottom of the concave portion 3).
Heat-resistant steel (for example, stainless steel) having one pore 4 provided so as to open to
The opening angle Θ of the opening of the recess 3 is 15 °, and the diameter of the pore 4 is 2 mm.

The split type floating dish 1 is placed at a position about 50 mm below a molten glass outflow pipe having an inner diameter of 1 mm and an outer diameter of 2.5 mm at a tip, and is heated so as to have a viscosity of 15 poise. The molten glass lump made of the molten glass made of the lanthanum flint glass was allowed to fall naturally from the tip of the outflow pipe, and the molten glass lump was received by the concave portion 3 of the split type floating dish 1. At this time, the molten glass lump was received while blowing out one liter of air per minute from the fine holes 4 provided in the split type floating dish 1. As a result, the molten glass lump is divided into split type floating dishes 1
And received slightly by the concave portion 3 of the split type floating plate 1 in a state where the floating surface slightly floated without almost contacting the inner surface 2a of the concave portion.

Subsequently, while blowing out one liter of air per minute from the pores 4, the above molten glass lump was formed. At this time, as shown in FIG. 2, the molten glass lump 2 rotated while slightly floating without almost contacting the inner surface 2 a of the concave portion of the split type floating plate 1, and was formed into a spherical shape. The spherically shaped molten glass lump 2 was cooled while floating in the recess 3, and the surface was lowered to a glass transition temperature (Tg). Thereafter, the molten glass lump 2 was heated and softened again while being floated by an air current, thereby removing and reducing moisture and hydroxyl groups from near the glass surface.

Thereafter, in the same manner as in Example 1, the molten glass lump 2 is lowered to a predetermined temperature to freeze the state in which water and hydroxyl groups have been released from the vicinity of the glass surface, and then the split-type floating pan is opened right and left. Then, the glass material to be molded was dropped on a mold at a predetermined temperature, and immediately press-molded. Press molding was performed 100 times in the same manner as in Example 1. However, no bubbles were generated at the contact interface with the molding die, and there was no abnormality in the hard carbon film.

[0046]

According to the production method of the present invention, no bubbles are generated at the interface with the mold (the surface of the lens), and a lens having good appearance quality can be mass-produced. Furthermore, according to the production method of the present invention, since the surface of the mold is prevented from being oxidized or eroded by moisture, fusion and roughening of the surface are prevented, and the life of the mold is extended. Further, by selecting the optimal molding conditions, a lens with high surface accuracy can be obtained with an appropriate molding cycle time, and high productivity can be realized.

[Brief description of the drawings]

FIG. 1 shows temperature changes of a glass material to be molded and a molding die in a production method of the present invention [(a) non-isothermal press, (b) isothermal press].

FIG. 2 is a schematic cross-sectional view of a split type floating dish 1 used in Example 6.

Claims (14)

[Claims] 1. A glass material to be molded, wherein the glass material is 1
A step of heating to a temperature at which the viscosity becomes 0 ^5.5 to 10 ^9.5 poise (hereinafter, referred to as a softening step) and a step of controlling the softened glass material to a temperature lower than the softening temperature by at least 10 ° C. And a temperature control step) and a step of press-molding a temperature-controlled glass material (hereinafter, referred to as a forming step). 2. The method according to claim 1, wherein the temperature of the glass material at the start of press molding is equal to the temperature of the mold. 3. In the temperature control step, the glass material is
3. The method according to claim 2, wherein the molding is carried out after cooling to a temperature higher than (glass transition temperature -100 ° C.) and then heating and raising the temperature. 4. The method according to claim 1, wherein the temperature of the glass material at the start of press molding is higher than the temperature of the mold. 5. The glass material to be formed is flowed from a molten pipe.
The falling molten glass is naturally dropped or cut by a cutting blade
Molten glass lump, and ^9.5Po
Below the temperature equivalent to as (however, (glass transition temperature -100
(C) or more).
2. The production method according to claim 1. 6. The method according to claim 1, wherein in the softening step, the glass material to be formed is softened by heating while the glass material is levitated by an air current. 7. The production method according to claim 1, wherein in the temperature control step, the temperature of the glass material to be molded is controlled while the glass material is levitated by an air current. 8. The production method according to claim 6, wherein a dry airflow is used as the airflow for floating the glass material to be molded. 9. The production method according to claim 1, wherein the temperature-controlled glass material to be molded is transferred to a molding die to start press molding. 10. The glass material to be molded whose temperature has been controlled in the temperature control step is heated and heated before starting the press molding, and thereafter the press molding is started.
The production method according to the paragraph. 11. The production according to claim 10, wherein the heating and raising of the temperature before the start of press molding are performed while floating the glass material to be molded by an air current, or after transferring the glass material to be molded to a molding die. Method. 12. The temperature of a molding die at the start of press molding is determined by adjusting the viscosity of the glass material to be molded to 10 ^7.3 to 10
^The method according to any one of claims 1 to 11, wherein the temperature is set to ¹² poise. 13. The production method according to claim 1, wherein after the start of press molding, the temperature of the molding die is cooled to a glass transition point of the glass to be molded or lower, and then the mold is released. 14. The production method according to claim 1, wherein the glass material to be formed is phosphate glass.