JP3229943B2 - Glass optical element molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a glass optical element such as a glass lens which does not require grinding and polishing after press forming. In particular, the present invention relates to a molding method capable of obtaining a glass optical element having good optical characteristics at a relatively high production speed by greatly reducing a cycle time required for press molding.

[0002]

2. Description of the Related Art A glass preform, which is a glass material to be molded, is press-molded in a molding die having the required surface accuracy and surface roughness required for the surface of the glass molded body, and the glass which does not require grinding and polishing after the press molding is required. Various methods for manufacturing an optical element have been conventionally known. For example, the method described in JP-A-64-72929 or JP-B-2-16251 is a method of heating a mold and a glass preform together. That is, a glass preform is inserted into a molding die composed of an upper die, a lower die and a guide die for guiding them, heated together with the molding die to a temperature at which the preform is sufficiently softened, and then pressed. Next, the glass molded body is cooled to a temperature near the glass transition point at a cooling rate that does not impair the surface accuracy of the molded glass (or cooled to around room temperature after a certain period of time). The glass compact is removed.

In a method in which the preform is heated, molded, and cooled together with the molding die while the glass preform is held in the molding die, the temperature of the glass and the molding die are almost always equal, and the pressing process proceeds. The temperature difference between the surface of the glass and the inside of the glass is eliminated, so that sink is unlikely to occur and stable surface accuracy is obtained. However, there is a drawback that the cycle time required for all the steps is extremely long because the temperature rise time before starting the press and the cooling time required for taking out after the press are required. Furthermore, since the contact time between the glass and the mold surface in the process from heating to pressing is long, there is a disadvantage that a reaction easily occurs between the glass and the mold surface, and the mold life is shortened.

On the other hand, a glass preform softened in advance is inserted separately into a heated mold,
There is also known a method of forming a glass optical element which can eliminate the need for grinding and polishing after press forming [Japanese Patent Laid-Open No. 61-251529].
No., No. 61-286232, No. 62-27334,
No. 63-45134]. Also in this method, as described above, a molding die having the required surface accuracy and surface roughness required for the glass molded body surface is used. However, in these methods, when it is necessary to greatly deform the glass material, it may not be possible to form the glass material to a desired shape, and it is easy to cause sink marks and shape distortion, and it is difficult to obtain surface accuracy. There were drawbacks.

[0005]

The method of press-molding a glass preform that has been softened by heating in a preheated mold has the advantage that a short press time is required. Furthermore, since the temperature of the mold can be made relatively low and the mold can be released if a certain period of time is left for cooling the glass temperature after pressing, the cycle time can be greatly reduced.
However, in the above-described method, the glass is cooled and solidified before press molding to a desired thickness, so that the molded product is stable, especially a biconvex lens having a small edge thickness (about 1.0 to 1.3 mm). There is a problem that a glass molded body such as a lens or a meniscus lens cannot be obtained and a problem that shape transferability is insufficient.

Accordingly, an object of the present invention is to manufacture a glass optical element by press-molding a glass material such as a heat-softened glass preform with a preheated molding die, which can greatly reduce the cycle time required for press molding. An object of the present invention is to provide a method for forming a glass optical element which can be obtained stably even with a lens having a small edge thickness and has good shape transferability. It is still another object of the present invention to provide a method for forming a glass optical element having high surface accuracy without surface defects such as sink marks and surface shape distortion. It is a further object of the present invention to provide a method for forming a glass optical element which has high surface accuracy without surface defects such as sink marks and surface shape distortions and which can produce a glass optical element having a center thickness within an allowable tolerance. It is in.

Further, when a glass material such as a glass preform is heated and softened, there is another problem that the heat-softened glass material is fused with a jig holding the glass material. Therefore, another invention of the present invention is a method of manufacturing a glass optical element by press-molding a glass material such as a heat-softened glass preform with a preheated mold, and a method for holding a glass material. It is an object of the present invention to provide a method for forming a glass optical element, which can prevent glass fusion, has good shape transferability, and can greatly reduce the cycle time required for press molding.

[0008]

SUMMARY OF THE INVENTION The present invention is a method for forming a glass optical element by pressing a heat-softened glass material to be formed with a preheated forming die. Is 10 ⁹
With a temperature corresponding to less than Poise, the temperature of the preheating of the mold is set to a temperature at which the viscosity of the glass material is 10 ⁹ to 10 ¹² Poise, and the heat-softened glass material is pressurized in the preheated mold, The present invention relates to a method for molding a glass optical element, which comprises releasing a glass molded body from a mold after cooling.

Further, the present invention relates to a method for forming a glass optical element, wherein the glass material is softened by heating while being floated by an air current. Hereinafter, the present invention will be described.

The present invention is a method for molding a glass optical element by press-molding a heat-softened glass material to be molded with a preheated mold. The types and shapes of the glass constituting the glass material are conventionally known.
The glass material can be, for example, a glass preform or a glass gob. The glass preform refers to a molded product formed into a predetermined shape used as a precursor when molding a glass optical element. The glass preform may be formed by cold forming or molten glass being formed by hot forming, or may be obtained by subjecting them to mirror polishing or the like. Further, the surface may be not a mirror surface but a rough surface. For example, a ground product ground with # 800 diamond may be used as a glass preform.

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

In the molding method of the present invention, the glass material is heated to a temperature corresponding to a viscosity of less than 10 ⁹ poise to soften the glass material. By the viscosity of the glass material is less than 10 ⁹ poise, it is possible to mold by sufficiently deforming the glass material in the mold preheated to a temperature corresponding to a viscosity of more than ¹⁰⁹ poises. In order to mold the mold at a relatively low temperature, the glass material is preferably 10
It is appropriate to heat to a temperature corresponding to ^5.5 to ^7.6 poise to soften. The preheating temperature of the mold is a temperature at which the viscosity of the glass material is equivalent to 10 ⁹ to 10 ¹² poise. If the viscosity is below the temperature corresponding to 10 ¹² poise,
The glass material stretched large, it becomes difficult to obtain a thin glass shaped material edge thickness, also difficult to obtain a high surface accuracy, at temperatures above the temperature at which the viscosity corresponds to ¹⁰⁹ poise, requires the molding cycle time As a result, the life of the mold becomes shorter.

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

In the molding method of the present invention, the heat-softened glass material is initially pressed in the preheated mold for 3 to 60 seconds. If the initial pressure is less than 3 seconds, the elongation of the glass is insufficient, and a glass optical element having a desired shape cannot be obtained. The initial pressurization increases the surface accuracy and the like as much as it is longer. However, if it is too long, the cycle time cannot be shortened, and the life of the mold may be adversely affected. The upper limit is 60 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 it is usually appropriate to set the pressure in the range of 30 to 300 kg / cm ² .

Simultaneously with the start of the initial pressurization, during the initial pressurization, or after the end of the initial pressurization, the vicinity of the molding surface of the mold is cooled at a rate of 20 ° C./min or more. The cooling rate can be slower than 20 ° C./min, but this only unnecessarily increases the molding cycle time. Although it depends on the size and shape of the glass molded body, from the viewpoint of obtaining high surface accuracy, the vicinity of the molded surface is 20 to 18
Cooling at a rate of 0 ° C./min is preferred.

After the initial pressurization, 5 to 70% of the initial pressurization
It is possible to obtain good surface accuracy without sink marks and surface shape distortion by applying secondary pressurization at a constant pressure and maintaining this pressure while maintaining this pressure. It is preferable from the viewpoint that it can be maintained. More preferably, the secondary pressurization is suitably set to 20 to 50% of the initial pressurization. Further, the center thickness of the heat-softened glass material is 0.03 mm smaller than the center thickness of the final product.
It is preferable to perform initial pressurization so as to be within a range larger by 15 mm, and then to perform secondary pressurization from the viewpoint of maintaining the center thickness of the final product within an allowable tolerance. That is, in the second pressurization, the pressure is reduced at a stretch, and the glass has a high viscosity, so that the center thickness can be deformed by pressurizing only about 0.001 to 0.12 mm. It is easy to set the wall thickness within a tolerance of ± 0.03 mm.

The above-mentioned initial pressurization and secondary pressurization reduce the initial pressurization of the heat-softened glass material to a desired center thickness within a range of 0.03 mm smaller and 0.15 mm larger than the center thickness of the final product. As a result, the center thickness of the final product can be obtained by starting the secondary pressurization before or at the same time as the stoppage of the initial pressurization. Since the pressurization is continuous between the pressure and the secondary pressurization, it is preferable from the viewpoint that the surface accuracy is not impaired. When a desired center thickness is obtained by an external stopper mechanism or the like and further secondary pressurization is performed, the pressurization is interrupted for a moment, so that there is a tendency that it is difficult to obtain good surface accuracy.
The initial pressurization and the secondary pressurization are preferably performed by a double cylinder mechanism. The double cylinder mechanism will be further described in embodiments described later.

The glass molded article molded under pressure as described above and then cooled is released from the mold after the temperature in the vicinity of the molding surface has fallen below the temperature corresponding to the viscosity of the glass material of 10 ¹² poise. Is done. If the glass viscosity exceeds 10 ¹² poise, viscous flow does not occur in a short time, and the glass may be regarded as substantially solidified. As a result, the glass molded body is not deformed after the mold release, and a good surface accuracy is obtained. It is particularly preferable that the mold release of the glass molded body is performed at a temperature near the molding surface at a temperature corresponding to a viscosity of the glass material of 10 ¹² to 10 ^14.5 poise.

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

As the molding die used in the present invention, for example, a molding die 39 composed of an upper die 35, a lower die 34 and a guide die 36 as shown in FIG. 5 can be used. However, it is not limited to these. In addition, as a molding die, cermets such as silicon carbide, silicon, silicon nitride, tungsten carbide, aluminum oxide and titanium carbide, and diamond, heat-resistant metal, noble metal alloy, carbide, nitride, boride, oxide, etc. Those coated with ceramics or the like can be used. In particular, after a silicon carbide film is formed on a silicon carbide sintered body by a CVD method and processed into a finished shape, amorphous and / or crystalline graphite such as an i-carbon film is formed by an ion plating method or the like. Preferably, a carbon film formed of a single component layer or a mixed layer of diamond is formed. The reason is,
This is because even if the molding is performed at a relatively high mold temperature, fusion does not occur, and the mold can be easily released at a relatively high temperature because of good releasability.

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

In the present invention, there is no particular limitation on the gas used as an air flow for floating the glass material. However, from the viewpoint that the heated glass material does not react with the jig, and furthermore, from the viewpoint of preventing the heated jig from being deteriorated by oxidation, it is preferable to use a non-oxidizing gas.
Suitably, it is nitrogen or the like. Also, reducing gas,
For example, hydrogen gas or the like can be added. The flow rate of the airflow can be changed as appropriate in consideration of the shape of the opening 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. When the gas flow rate exceeds 20 liters / minute, the glass on the floating jig shakes greatly even when the glass weight is 2000 mg or more, and the shape changes when the glass material is a preform during heating. This is because there are times.

The floating of the glass material by the air current is, for example,
This can be performed by an airflow flowing upward from an upper opening having an opening diameter smaller than the diameter of the glass material. As shown in FIG. 2, the upper opening 11 of the floating jig 10 supported by the floating jig support 13 is smaller than the diameter of the glass material 1 and is above the bottom 12 of the upper opening 11 of the floating jig 10. The glass material 1 floats on the upper opening 11 by the airflow flowing out of the glass material 1 and is held so as not to contact the floating jig 10. The glass material 1 is heated by a glass softening heater 14 provided around the glass material. In addition, the floating jig 10
May have a structure that can be divided into two as shown in FIG. 6 (each part is indicated by 10a and 10b).

The floating of the glass material by the air current can also be performed by an air current flowing out from a porous surface having a spherical surface or a flat surface approximating the curvature of the outer diameter of the glass material. In particular, when the glass material is a preform, it is effective because the shape of the preform is extremely easy to maintain. Further, when the glass material is a glass gob, the surface defect of the glass gob can be removed by heating while being floated by an air current from the porous surface. For example, as shown in FIG. 3, a porous surface 18 having a spherical surface approximating the curvature of the glass material 1 supported by a floating jig support 19.
The glass material 1 is held in a floating state by the airflow flowing out of the porous surface 18 on the floating jig 17 having the following. The floating jig support 14 and the floating jig 15 are shown in FIG.
As in the case of (1), it is also possible to have a dividable structure.

Further, the heating of the glass material includes a case where the glass material is heated from room temperature to a predetermined temperature, a case where a glass material having a certain temperature is further heated, and a case where a glass material already heated to a predetermined temperature is used. For example, when the glass material is a glass gob, a glass gob made of molten glass can be used without cooling.

In the present invention, the transfer of the heat-softened glass material to the preheated mold can be performed, for example, by holding the glass material to be formed by suction or by dropping the softened glass material. . The suction holding of the glass material can be performed, for example, by a suction holding device 15 having a movable lower opening 16 shown in FIG. The lower opening 16 is connected to, for example, a decompression pump or a vacuum pump that suctions the inside, and the lower opening 16 can hold the glass material by suction. Floating jig 10
The glass material 1 that has been heated and softened by suction is sucked and held in the lower opening 16 of the movable suction holding device 15, and is transferred onto the forming surface 40 of the lower mold 34 as shown in FIG. . Next, as shown in FIG. 5, the softened glass material 1 is pressed and molded with the molding surface 40 of the lower mold 34 and the molding surface 41 of the upper mold 35, whereby the glass molded body 2 can be obtained.

The heat-softened glass material can be transferred by dropping the glass material. The drop of the glass material can be performed, for example, by dividing the floating jig used for heating the glass material into two or more parts and opening the lower part. For example, as shown in FIG. 6, when the glass material 1 is heated on the floating jig 10 and the glass material 1 is softened, as shown in FIG.
Is horizontally divided into two parts 10a and 10b and moves in opposite directions (left and right in the figure), whereby the glass material 1 falls. At this time, the lower mold 34 is set as a receiving mold for the falling glass material 1 so that the lower mold 3 is installed.
The glass material 1 can be transferred onto the molding surface 40 of the fourth material.

Further, in the present invention, guide means can be used for the purpose of dropping and moving the heat-softened glass material onto a predetermined molding surface. For example, as shown in FIGS. 6 and 7, on the upper part of the floating jig 10, there is provided a cylindrical guide means 50 (individable portions 50 a and 50 b) having an inner diameter dimension capable of maintaining an outermost diameter of the glass material 1 and an appropriate clearance. The glass material 1 can be dropped to the center of the mold. However, the structure of the guide means is not particularly limited as long as it can prevent the glass material from being displaced when the floating jig is divided and moved. For example, the present invention is not limited to a cylindrical shape, and may be a plurality of pipes arranged in a lattice or two or more plates facing each other. In addition, the guide means may have a structure that can be divided and moved in consideration of the fact that the upper mold moves onto the lower mold holding the glass material and performs press molding during molding.

The method of dividing and moving the floating jig used to heat the glass material is not particularly limited. For example, when the floating jig moves horizontally as described above, the
Divided into four or four, moving in three directions (different directions by 120 °) or four directions (different directions by 90 °)
Glass material can also be dropped. By dropping and moving the heat-softened glass material, the glass material can be transferred into the mold in a short time.

[0030]

According to the present invention, a glass optical element is manufactured by press-molding a glass material such as a heat-softened glass preform with a preheated molding die, which can greatly reduce the cycle time required for press molding. A method for forming a glass optical element which can be stably obtained even with a lens having a small edge thickness and has good shape transferability can be provided. Further, according to the present invention, it is possible to provide a method for forming a glass optical element having high surface accuracy without surface defects such as sink marks and surface shape distortion. Further, according to the present invention, there is provided a glass optical element molding method capable of producing a glass optical element having high surface accuracy without surface defects such as sink marks and surface shape distortion and having a center thickness within an allowable tolerance. be able to. That is, according to the present invention, the conventional technique (5-2) in which the mold and the glass preform are heated together.
(0 min / cycle), the cycle time required for press molding can be significantly reduced, and a glass optical element having no surface defects and high surface accuracy can be manufactured. Also,
According to the present invention, it is possible to provide a method for molding a glass optical element while completely preventing glass from being fused (fixed) to a molding surface.

[0031]

Next, the present invention will be described by way of examples. Examples 1-1 to 1-5Press mold  As shown in Fig. 1, the press mold is used as a base material.
Using silicon carbide (SiC) sintered body 31, grinding
After processing into a less mold shape, the molding surface is further
Forming silicon carbide film 32 and grinding and polishing
Mirror-finished to the shape corresponding to the glass compact to be
The mold base was obtained. Furthermore, the silicon carbide film 3 of the mold base
2 on top of i-carbon (diamond-like carbon)
The film 33 is formed to a thickness of 500 ° by an ion plating method.
Φ18mm (φ15m after centering)
m) A lower mold 34 for a biconvex glass lens was obtained. Shown in FIG.
The upper mold 35 is also obtained by the same method as the lower mold 34.
Was. The upper mold 35 and the lower mold 34 are coaxial as shown in FIG.
It is set on the top, and the upper mold 35 and the lower mold
A molding die 39 is composed of a guide 34 and a guide die 36 for guiding the same.
Has been established. Further, on the upper surface of the upper mold 35, a secondary
A pressure push rod 45 is provided. Lower mold 34 and upper mold
The heating of 35 is performed by a mold heater attached to the outer periphery of the body mold 37.
In the lower mold 34 from the lower part of the mold support base 38.
Is controlled by a thermocouple 42 for the mold temperature measurement inserted in the. More torso
The temperature of the mold 37 is determined by a thermoelectric thermometer inserted into the mold 37.
The temperature is measured in pairs 43.

[0032]Floating jig and transfer means  The same closed chamber with the mold heating mechanism described above (Figure
(Not shown), a floating jig and transfer means shown in FIG.
Have been killed. First, the glass material (preform) 1
A glass softening heater 14 for heating and softening is provided.
In the glass softening heater 14, the floating jig support 13 is
The glassy carbon floating jig 10 (hereinafter, G
C floating jig). Furthermore, glass
The material 1 is supplied from the inside of the floating jig support 13 to the GC floating jig.
98% N of the flow rate shown in Table 1 supplied to the lower part
_Two + 2% H_Two Gas (Examples 1-1 to 1-3) or N_Two gas
(Examples 1-4 to 1-5) Floating and holding
You. In addition, there is no vertical or water outside the glass softening heater 14.
Glassy carbon vacuum pack
15 (hereinafter referred to as GC vacuum pad),
Usually, it is waiting above the GC floating jig 10.

[0033]Preheating and pressing process  Contains the above-mentioned press forming mechanism and glass heating mechanism
The inside of a closed chamber (not shown) of the molding machine was evacuated.
After that, the 98% N_Two + 2% H_Two Gas or N_Two Introduce gas
Then, the inside of the closed chamber was set to the same gas atmosphere. Next,
Preform 1 made of borosilicate optical glass (Table
Marble-shaped hot molded product having a mirror surface without surface defects,
(Weight 1000mg, transition point 534 ° C, yield point 576 ° C)
Here is an example using. For mold temperature measurement with the mold heater 44
The temperature of the upper mold 35 and the lower mold 34 measured by the thermocouple 43 (composition)
(Molding temperature) is the temperature corresponding to the viscosity of the glass shown in Table 1.
And kept at the same temperature. In addition, the viscosity of glass
The relationship between temperature and temperature is as follows. Glass viscosity temperature 10⁹ Poise 614 ° C 10^Ten Poise 592 ° C 10¹¹ Poise 572 ° C 10¹² Poise 554 ° C 10^12.7Poise 543 ° C 10^13.4Poise 534 ℃ 10^14.5Poise 518 ℃

On the other hand, the glass softening heater 14
The temperature of the glass preform 9 on the floating jig 10 is heated to a temperature at which the viscosity of the glass corresponds to the viscosity shown in Table 1,
Soften the levitation. The relationship between the viscosity of glass and the temperature is as follows. Viscosity of glass 10 ^5.5 poise 718 ° C. 10 ^6.4 poise 686 ° C. 10 ^7.3 poise 658 ° C. 10 ^8.2 poise 634 ° C. ^108.8 poise 619 ° C. Then, the floating softened preform 1 is used as a GC floating jig 10 outside the glass softening heater 14. G waiting above
The C vacuum pad 15 descends to the preform 1 and holds it by suction. At this time, the temperature of the GC vacuum pad is heated to 300 to 400 ° C. by the radiant heat from the glass softening heater 14, but the glass is not fused because it is low temperature.

Next, as shown in FIG.
The GC vacuum pad 15 holding the preform 1 quickly moves to above the lower mold 34, descends again to near the molding surface 40 of the lower mold 34, stops suction, and stops the preform 1 on the molding surface 40 of the lower mold 34. Put. Thereafter, the GC vacuum pad 15 retreats from above the lower mold 34 and returns to the original standby position, so that there is no obstacle at the upper part of the lower mold 34,
The upper mold 3 in which the lower mold 34 is fixedly set instantaneously with the lower mold 34 together with the lower mold 34 together with the lower mold 34.
Increase to 5. As shown in FIG. 5, the preform 1 is charged at 100 kg / c for 10 seconds in a molding die 39 composed of an upper die 35, a lower die 34, and a guide die 36 for guiding the same.
Pressure molding is performed at a pressure of m ² , and the thickness at which the flange of the lower mold 34 contacts the bottom surface of the guide mold 36 is 30 μm larger than the thickness of the final product. On the other hand, after 5 seconds from the start of pressurization by the first cylinder, 20 kg / cm ² (20 kg / cm ² ) is applied to the back surface of the upper mold 35 by the push rod 45 connected to the second cylinder inside the first cylinder. 1-1
The glass molded body 2 and the molding die 39 are pressed and held at a pressure of 1-5). Then, the molding die heater 44 is cut off by being cut off, and is allowed to cool. After a lapse of the molding time (initial pressurization time (10 seconds) + secondary pressurization time) shown in Table 1, a thermocouple for mold temperature measurement is used. When the temperature of the upper mold 35 and the lower mold 34 measured at 42 becomes the temperature shown as the mold temperature at the time of mold release in Table 1 and the glass molded body 2 has a predetermined thickness, the glass molded body 39 2 was released from the mold and taken out. The relationship between the viscosity of glass and the temperature is as described above.

The glass compact 2 thus obtained
(Outer diameter φ18mm, wall thickness 2.9mm, edge thickness 1.0mm
The performance of the biconvex lens after annealing was evaluated with respect to the surface accuracy using an interferometer, the visual appearance, and the surface state using a stereomicroscope. The results are shown in Table 1 as 1-1 to 1-5. The evaluation was performed on five lenses obtained by the same method (the same applies to the following examples). As a result, all the lenses were good.

Examples 2-1 to 2-5Press mold  Example 1 except that the press molding die does not have the push rod 45.
The same thing as that shown in FIG. 8 was used.Floating jig  The same closed chamber with the mold heating mechanism described above (Figure
(Not shown) includes a floating jig 10 (10a, 1a, 1a) shown in FIG.
0b), guide means 50 (50a, 50b), glass element
A glass softening heater (not shown) that heats and softens the material
Is provided. The floating jig 10 is made of glassy carbon
Floating jig (hereinafter referred to as GC split floating jig)
And the guide means 50 is also a divided cylindrical shape made of the same material.
A guide (hereinafter, referred to as a GC divided cylindrical guide). Sa
In addition, the glass material 1 is supplied from inside the GC divided floating jig.
98% N of the flow rate shown in Table 1_Two + 2% H_Two Gas jet
By floating, it is held floating.

[0038]Heat softening and pressing process  Contains the above-mentioned press forming mechanism and glass heating mechanism
After evacuating the inside of the closed chamber of the molding machine, 98% N
_Two + 2% H_Two Gas is introduced, and the same gas is
Atmosphere. Next, the mold heater 44 shown in FIG.
The upper mold 35 and the lower mold 3 measured with the thermocouple 43 for mold temperature measurement.
4, the viscosity of the same glass material 1 as in Example 1 was 1
0¹¹572 ° C. corresponding to poise (Examples 2-1 to 2-3, 2
-5) or 10¹²554 ° C corresponding to poise (Example 2)
Heated until 4) and kept at the same temperature. At this time
The upper and lower molds are heated at different positions, respectively,
At this time, as shown in FIG.
It is. On the other hand, the GC softening heater was
As shown in Table 1, the temperature of the glass material 1 on the
Glass viscosity 10^5.5 71 which is the temperature corresponding to poise
Heat to 8 ° C. and hold.

Next, the GC divided floating jig 10 which floats and holds the heat-softened glass material 1 moves quickly to a position immediately above the lower mold 34, and then, as shown in FIG. The floating jig 10b instantaneously moves in the left and right horizontal directions and opens, whereby the glass material 1 is dropped and placed on the molding surface 40 of the lower mold 34. At this time, GC
Immediately above the divided floating jig 10, a GC divided cylindrical guide 50 having an inner diameter dimension that maintains an appropriate clearance with respect to the outermost diameter of the glass material 1 is installed. When the glass material 1 is opened and falls, the glass material 1 serves as a guide to minimize the amount of setting deviation between the glass material 1 and the lower mold 34.

After the glass falls, the GC divided cylindrical guide 5
0a and the other 50b move in the left and right horizontal directions, respectively, and open. Therefore, there is no obstacle in the upper part of the lower mold 34, and the molding die support 38 instantaneously fixes the lower mold 34 to the upper mold 35 in which the molding die support 38 is fixedly set together with the lower mold 34 in a coaxial manner. Raise the upper die 3 as shown in FIG.
5 and a guide die 36 for guiding the lower die 34, the glass material 1 is press-formed at a pressure of 100 kg / cm ² for 10 seconds to a predetermined thickness, and then the pressure is increased at once. At the same time as the pressure of 50 kg / cm ² , the glass molded body 2 and the mold held at this pressure were allowed to cool by turning off the mold heater 14, and the molding time (initial pressurization time (10 seconds) ) + Second pressurizing time), the upper mold 35 and the lower mold 3 whose temperature was measured by the thermocouple 43 for mold temperature measurement after a lapse of seconds.
When the temperature of No. 4 became a temperature corresponding to the viscosity shown as the mold temperature at the time of mold release in Table 1, the glass molding 2 was removed from the molding die.
Was released from the mold.

The glass compact 2 thus obtained
(Outer diameter φ18mm, wall thickness 2.9mm, edge thickness 1.0mm
After annealing, the performance of the biconvex lens was evaluated for surface accuracy using an interferometer, visual appearance, and surface state using a stereomicroscope. The results are shown in Table 1. The evaluation was performed on five lenses obtained by the same method. Table 1 shows the evaluation results of the glass molded body obtained by changing the temperature of the softened glass material 1, the shape of the glass material 1, the flow rate of the gas flowing out from the GC divided floating jig, the mold temperature, and the mold release temperature. Is shown. As a result, each molded article (lens) was good.

Examples 3-1 to 3-3 The initial pressurization time was 5 seconds (Example 3-1) and 30 seconds (Example 3-2)
Alternatively, a glass molded body (outside diameter φ18 mm, thickness 2.9) was prepared in the same manner as in Example 1-1, except that 55 seconds (Example 3-3) was used.
mm, a biconvex lens having an edge thickness of 1.0 mm). The performance of the glass molded body after annealing is determined by the surface accuracy by interferometer and
The visual appearance and the surface condition by a stereoscopic microscope were evaluated. Table 1 shows the results.

Examples 4-1 to 4-2 The cooling of the mold 39 was simultaneously performed with the initial pressurization (pressurization at a pressure of 100 kg / cm ² ) (Example 4-1) or the initial pressurization 5
A glass molded body (outside diameter φ18 mm, wall thickness 2.9) was operated in the same manner as in Example 1-1 except starting after a lapse of seconds (Example 4-2).
mm, a biconvex lens having an edge thickness of 1.0 mm). The performance of the glass molded body after annealing is determined by the surface accuracy by interferometer and
The visual appearance and the surface condition by a stereoscopic microscope were evaluated. Table 1 shows the results.

[0044]

[Table 1]

The evaluation of the glass molded body was performed as follows. Surface accuracy ○: Asbestos, habit 0.5 or less ◎: Asth, habit 0.2 or less Surface condition ◎: good

In Examples 1 to 4, the cycle time is the sum of the molding time and the recovery time of the mold temperature (the temperature rise time from the temperature at the time of mold release to the temperature at the start of molding). In this example, since the resistance heating was used for heating the mold, the recovery time was about 35 seconds. Therefore, the cycle time is about 8
5 to 165 seconds. By using high-frequency heating or infrared heating for heating the mold, the recovery time can be reduced to about 10 seconds, and the cycle time can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a lower mold of a molding die used in the present invention.

FIG. 2 is a schematic explanatory view of a method of softening and transferring a glass preform on a floating jig used in the present invention.

FIG. 3 is a schematic explanatory view of a method for softening the floating of a glass preform on a floating jig used in the present invention.

FIG. 4 is a schematic explanatory view of a method for transferring a softened glass preform to a molding die.

FIG. 5 is a schematic explanatory view of press molding with a molding die used in the present invention.

FIG. 6 is a schematic explanatory view of a method for transferring a softened glass preform to a molding die.

FIG. 7 is a schematic explanatory view of a method for transferring a softened glass preform to a molding die.

FIG. 8 is a schematic explanatory view of press molding with a molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass material 2 ... Glass molded body 10, 17 ... Floating jig 10a, 10b ... Divided floating jig 11 ... Upper opening part of a floating jig 12 ... Floating jig Bottom of upper opening 13, 19 ... Floating jig support 14 ... Heater for softening glass 15 ... Suction holding device 16 ... Lower opening 18 ... Porous surface 34 ... Lower mold 35 ... Upper mold 36 ... Guide mold 37 ... Body mold 40, 41 ... Molding surface 45 ... Push rod 50a, 50b ... Guide means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B ^7/ 00-7/22 C03B 9/00-17/06

Claims (7)

(57) [Claims] 1. A method for molding a glass optical element by press-molding a heat-softened glass preform with a preheated mold, wherein the temperature of heating the glass preform is determined by adjusting the viscosity of the glass preform. and temperature corresponding to less than 10 ⁹ poise,
The viscosity of the temperature of the mold preheating the glass preform is equivalent to 10 ⁹ to 10 ¹² poise temperature (however, Garasupuri
When the temperature of the foam is 10 ⁷
When a temperature corresponding to 10 ⁹ poise, mold pre
The temperature of the heat is such that the viscosity of the glass preform is 10 ¹⁰ to
10 as excluding temperature) that corresponds to ¹² poise, the heating softened mold in a pressurized the glass preform was the preheating, the glass optical element, which comprises releasing the glass shaped material from the mold after cooling Molding method. 2. At the same time the initial pressure starts with the pressurization in said mold, or during the initial pressure, or after the initial pressurization completion, was cooled molding surfaces near the mold, said mold When the temperature near the surface is such that the viscosity of the glass preform is 10
^2. The molding method according to claim 1 , wherein the glass molded body is released from the molding die after the temperature becomes equal to or lower than ¹² poise. 3. The method according to claim 1, wherein the temperature of the molded surface is in the range of 10 ¹² to 10 when the viscosity of the glass preform is 10 ¹² to 10.
3. The molding method according to claim 2 , wherein the molding is performed at a temperature corresponding to ^14.5 poise. 4. The molding method according to claim 1 , wherein the glass preform is softened by heating while being floated by an air current. 5. The molding method according to claim 4 , wherein the transfer of the heat-softened glass preform to the preheated mold is performed by suction-holding the glass preform or by dropping the glass preform . 6. The molding method according to claim 5 , wherein the heat-softened glass preform is dropped by dividing a floating jig used for heating the glass preform into two or more parts. 7. The molding method according to claim 6, wherein a guide means for dropping the heat-softened glass preform in a predetermined direction is used.