JP4094587B2 - Glass optical element molding method - Google Patents

Description

  The present invention relates to a method for molding a glass optical element such as a glass lens that does not require grinding and polishing after press molding. 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 the cycle time required for press molding.

A method for producing a glass optical element, in which a glass preform, which is a glass material to be molded, is press-molded with a mold in which surface accuracy and surface roughness necessary for a glass molded body are ensured, and grinding / polishing after press molding is unnecessary There are various known in the past.
For example, the method described in JP-A-64-72929 or JP-B-2-16251 is a method of heating the mold and the 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, and heated together with the molding die to a temperature at which the preform is sufficiently softened, and then press-molded. Next, after cooling to the vicinity of the glass transition point at a cooling rate that does not impair the surface accuracy of the molded glass body after molding (or to cool to near room temperature after a certain period of time), from inside the mold The glass molded body is taken out.

  In a method in which the preform is heated, molded, and cooled together with the mold while the glass preform is held in the mold, the glass surface is kept at the same temperature because the temperature of the glass and the mold is almost equal. This eliminates the temperature difference between the inside and the inner surface, so that it is difficult for sink marks to occur and a stable surface accuracy can be obtained. However, since the temperature raising time until the press is started and the cooling time required for the removal after the pressing are necessary, the cycle time required for the entire process is remarkably increased. Further, since the contact time between the glass and the mold surface in the process from heating to pressing is long, there is also a drawback that the reaction between the glass and the mold surface is likely to occur and the mold life is shortened.

  On the other hand, there is also known a glass optical element molding method in which a glass preform that has been softened in advance is inserted into a mold that is heated separately from the glass preform so that grinding and polishing after press molding is unnecessary [Japanese Patent Laid-Open 61-251529, 61-286232, 62-27334, 63-45134]. Also in this method, as described above, a molding die in which the surface accuracy and surface roughness necessary for the glass molded body surface are secured is used. However, in these methods, when it is necessary to greatly deform the glass material, it may not be possible to form it into a desired shape, and sink marks and shape distortion are likely to occur, and surface accuracy is difficult to be obtained. There were drawbacks.

The method of press-molding a heat-softened glass preform in a preheated mold has the advantage that a short press time is required. Furthermore, since the mold temperature can be relatively lowered and the mold can be released if a certain amount of time is allowed for cooling of the glass temperature after pressing, the cycle time can be greatly shortened.
However, in the above-described method, the glass cools and solidifies before press molding to a desired thickness, and the molded product, particularly a biconvex lens having a thin edge (about 1.0 to 1.3 mm) is stable. There is a problem that a glass molded body such as a meniscus lens cannot be obtained, and a problem that shape transferability is insufficient.

Accordingly, an object of the present invention is a method for producing a glass optical element by pressing a glass material such as a heat-softened glass preform or the like with a preheated mold, which can significantly reduce the cycle time required for press molding. Accordingly, it is an object of the present invention to provide a method for molding a glass optical element which can be stably obtained even with a lens having a thin edge thickness and has good shape transferability.
A further object of the present invention is to provide a method for molding a glass optical element having no surface defects such as sink marks and surface shape distortion and having high surface accuracy.
Furthermore, an object of the present invention is to provide 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. There is.

Furthermore, when a glass material such as a glass preform is heat-softened, there is a problem that the heat-softened glass material is fused with a jig for 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, to a jig for holding the glass material. An object of the present invention is to provide a glass optical element molding method that can prevent glass fusion, has good shape transferability, and can significantly reduce the cycle time required for press molding.

The present invention is a method of molding a glass optical element by press-molding a glass material to be molded that has been heat-softened with a preheated mold,
The heating temperature of the glass material is set to a temperature corresponding to a viscosity of the glass material of less than 10 ⁹ poise, and the preheating temperature of the mold is set to a temperature corresponding to a viscosity of the glass material of 10 ⁹ to 10 ¹² poise. The present invention relates to a method for molding a glass optical element, wherein a heat-softened glass material is pressurized in the preheated mold, and the glass mold is released from the mold after cooling.

Furthermore, the present invention relates to a method for molding a glass optical element, wherein the glass optical element is softened by heating the glass material to be molded while being floated by an air current.
The present invention will be described below.

  The present invention is a method of molding a glass optical element by press-molding a glass material to be molded that has been softened by heating with a preheated mold. The type and shape 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 molded into a predetermined shape used as a precursor when molding a glass optical element. The glass preform can be formed by cold forming or hot glass forming from molten glass, and further by mirror-polishing these. Furthermore, the surface can be a rough surface instead of a mirror surface, and for example, a ground product ground with # 800 diamond can 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. Furthermore, in order to prevent a gas trap from being generated during molding, it is preferable that the shape of the molded product be in contact with the molding surface of the preform first. The shape of the glass preform can be, for example, a spherical shape, a marble shape, a disk shape, a spherical shape, or the like.
On the other hand, the glass gob is a glass piece obtained by dividing molten glass into a predetermined volume, and usually has an irregular shape such as a wrinkle. The glass preform is obtained by further molding the glass gob into a predetermined shape.

  Note that the capacity of the preform or gob is slightly larger than the capacity of the final product, and the final outer diameter can be determined by centering in a subsequent process.

In the molding method of the present invention, the glass material is softened by heating to a temperature corresponding to a viscosity of the glass material of less than 10 ⁹ poise. 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 molding die at a relatively low temperature, the glass material is preferably softened by heating to a temperature corresponding to 10 ^5.5 to 10 ^7.6 poise.
The preheating temperature of the mold is set to a temperature at which the viscosity of the glass material corresponds to 10 ⁹ to 10 ¹² poise. If the viscosity is lower than the temperature corresponding to 10 ¹² poise, it is difficult to obtain a glass molded body with a thin edge by greatly stretching the glass material, and it is difficult to obtain high surface accuracy, and the viscosity corresponds to 10 ⁹ poise. If the temperature exceeds the temperature, the molding cycle time becomes longer than necessary, and the life of the mold is shortened.

As the mold used in the present invention, a conventionally known mold can be used as it is. However, it is preferable to use a mold whose molding surface is composed of an amorphous and / or crystalline carbon film composed of a single component layer or mixed layer of graphite and / or diamond. In a mold having a molding surface composed of the 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, glass fusion (adherence) does not occur.
The carbon film is formed by means such as sputtering, plasma CVD, CVD, or ion plating. In the case of forming a film by sputtering, Ar is used as a sputtering gas in a range of a base temperature of 250 to 600 ° C., an RF power density of 5 to 15 W / cm ² , and a vacuum degree of sputtering of 5 × 10 ^{−4 to} 5 × 10 ⁻¹ torr. It is preferable to sputter such an inert gas using graphite as a sputtering target.
When the film is formed by the microwave plasma CVD method, it is formed using methane gas and hydrogen gas as source gases under the conditions of a base temperature of 650 to 1000 ° C., a microwave power of 200 W to 1 kW, and a gas pressure of 10 ^{−2 to} 600 torr. A membrane is preferred.
When forming by an ion plating method, it is preferable that the base temperature is 200 to 450 ° C. and the benzene gas is ionized.
These carbon films include those having C—H bonds.

In the molding method of the present invention, the heat-softened glass material is initially pressurized in the preheated mold for 3 to 60 seconds. If the initial pressure is less than 3 seconds, the glass is not sufficiently stretched, and a glass optical element having a desired shape cannot be obtained. In addition, as long as the initial pressurization becomes longer, the surface accuracy and the like are improved, but if it is too long, the cycle time cannot be shortened, and the life of the mold may be adversely affected, and 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 completion of the initial pressurization, the vicinity of the molding surface of the mold is cooled at a rate of 20 ° C./min or more. Although the cooling rate may be slower than 20 ° C./min, it only unnecessarily increases the molding cycle time. Although it varies depending on the size and shape of the glass molded body, it is preferable to cool the vicinity of the molding surface at a rate of 20 to 180 ° C./min from the viewpoint of obtaining high surface accuracy.

In addition, after the initial pressurization, secondary pressurization is performed at a constant pressure of 5 to 70% of the initial pressurization, and the vicinity of the molding surface is cooled while maintaining this pressure, without causing sink marks or surface shape distortion. It is preferable from the standpoint that accurate surface accuracy can be obtained and the center wall thickness can be kept within the allowable tolerance. More preferably, the secondary pressure is suitably 20 to 50% of the initial pressure.
Furthermore, the initial pressurization so that the center thickness of the heat-softened glass material is within the range of 0.03 mm to 0.15 mm larger than the center thickness of the final product, and then the secondary pressurization is performed. This is preferable from the viewpoint of keeping within the tolerance of the wall thickness. That is, in the secondary pressurization, since the pressure is reduced at a stretch and the glass has a high viscosity, the center thickness can only be deformed by pressure about 0.001 to 0.12 mm. It is easy to put the wall thickness within a tolerance of ± 0.03 mm.

The initial pressurization and the secondary pressurization are performed by applying the initial pressurization of the heat-softened glass material to a desired center thickness within a range of 0.03 mm to 0.15 mm larger than the center thickness of the final product. The center thickness of the final product is obtained by stopping by the means for stopping the pressure, and by starting the secondary pressurization before or simultaneously with the stop of the initial pressurization, and the initial pressurization and the secondary pressurization. Since pressurization is continued between pressurizations, it is preferable from the viewpoint that surface accuracy is not impaired. When a desired center thickness is obtained by an external stopper mechanism or the like and further subjected to secondary pressurization, the pressurization is interrupted for a moment, so that good surface accuracy tends to be difficult to obtain. The initial pressurization and the secondary pressurization are preferably performed by a double cylinder mechanism. The double cylinder mechanism will be further described in the examples described later.

The glass molded product that has been pressure-molded as described above and then cooled is released from the mold after the temperature in the vicinity of the molding surface has become equal to or lower than the temperature corresponding to 10 ¹² poise of the glass material. If the glass viscosity exceeds 10 ¹² poise, viscous flow does not occur in a short time, and it can be considered that the glass is almost consolidated. As a result, no deformation or the like occurs in the glass molded body after the mold release, and good surface accuracy is obtained. The release of the glass molded body is particularly preferably performed at a temperature in the vicinity of the molding surface corresponding to a viscosity of the glass material of 10 ¹² to 10 ^14.5 poise.

  There is no restriction | limiting in particular in the shaping | molding die used for the shaping | molding method of this invention except a molding surface. Furthermore, a resistance heater, a high-frequency heater, an infrared lamp heater, or the like can be used for heating the mold. In particular, from the viewpoint that the recovery time of the mold temperature is short, a high frequency heater and an infrared lamp heater are preferable. Further, the cooling of the mold can be carried out by electric discharge cooling, a cooling gas circulating in the mold, or the like.

  As the mold used in the present invention, for example, a mold 39 composed of an upper mold 35, a lower mold 34, and a guide mold 36 as shown in FIG. 5 can be used. However, it is not limited to these. Also, cermets such as silicon carbide, silicon, silicon nitride, tungsten carbide, aluminum oxide and titanium carbide as molds, and diamond, refractory metals, noble metal alloys, carbides, nitrides, borides, oxides etc. on their surfaces What coated ceramics etc. 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, an amorphous and / or crystalline graphite such as an i-carbon film is formed by an ion plating method or the like. What formed the carbon film which consists of a single component layer of diamond or a mixed layer is preferable. The reason for this is that 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 molding method of the present invention, the heat softening of the glass material can be performed while the glass material body is floated by an air current, and the heat 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 the glass from being fused with the jig that holds the glass material during heating. On the other hand, by blowing out gas from the inside of the jig, the glass material is levitated by the air current to form a gas layer on the jig surface and both surfaces of the glass. As a result, the jig and glass react. Without being softened. 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 glass gob and there are surface defects such as wrinkles in the irregular shape, it is possible to prepare the shape and erase the surface defects by floating by air flow while softening with heat. is there.

There is no restriction | limiting in particular as gas used as the airflow used for the float of a glass raw material in this invention. However, in terms of preventing the heated glass material from reacting with the jig and preventing deterioration of the heated jig due to oxidation, it is preferably a non-oxidizing gas, for example, nitrogen or the like is appropriate. It is. A reducing gas such as hydrogen gas may be added.
The flow rate of the airflow can be changed as appropriate in consideration of the shape of the mouth that blows out the airflow, the shape and weight of the glass material, and the like. In a normal case, a gas flow rate in the range of 0.005 to 20 liters / minute is suitable for floating a glass material. However, if the gas flow rate is less than 0.005 liter / min, the glass material may not be sufficiently floated when the weight of the glass material is 300 mg or more. Further, when the gas flow rate exceeds 20 liters / minute, even when the glass weight is 2000 mg or more, the glass on the floating jig is greatly shaken, and when the glass material is a preform during heating, its shape changes. Because there are things.

  The levitation of the glass material by the airflow can be performed by, for example, an airflow flowing upward from an upper opening having an opening diameter smaller than that 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 to the upper opening 11 and is held so as not to contact the lifting jig 10. The glass material 1 is heated by a glass softening heater 14 provided around the glass material 1. Further, the levitation jig 10 may have a structure (each portion is indicated by 10a and 10b) that can be divided into two as shown in FIG.

  Further, the levitation of the glass material by the air current can also be performed by the air current flowing out from a porous surface having a spherical surface or a plane that approximates the curvature of the outer diameter of the glass material. In particular, when the glass material is a preform, it is effective because it is very easy to maintain the shape of the preform. Furthermore, when the glass material is a glass gob, the surface defects of the glass gob can be removed by heating while being floated by an air flow from the porous surface. For example, as shown in FIG. 3, the material flows out from the porous surface 18 onto the floating jig 17 having a porous surface 18 having a spherical surface approximate to the curvature of the glass material 1 supported by the floating jig support 19. The glass material 1 is held in a state of being floated by the flowing airflow. The levitation jig support 14 and the levitation jig 15 may have a structure that can be divided as in the case of FIG.

  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 the predetermined temperature is used. For example, when the glass material is a glass gob, a glass gob made from molten glass can be used without cooling.

In the present invention, the heat-softened glass material can be transferred to the preheated mold by, for example, sucking and holding the glass material to be molded or dropping the softened glass material.
The glass material can be sucked and held, for example, by a suction holding device 15 having a movable lower opening 16 shown in FIG. The lower opening 16 communicates with, for example, a decompression pump, a vacuum pump, or the like that sucks the inside, and the glass material can be sucked and held in the lower opening 16. The glass material 1 heated and softened on the levitation jig 10 is sucked and held in the lower opening 16 of the movable suction holding device 15, and the molding surface 40 of the lower mold 34 of the molding die as shown in FIG. Move up. Next, as shown in FIG. 5, the glass molded body 2 can be obtained by press-molding the softened glass material 1 with the molding surface 40 of the lower mold 34 and the molding surface 41 of the upper mold 35.

  Transfer of the heat-softened glass material can also be performed by dropping the glass material. The glass material can be dropped by, for example, dividing the floating jig used for heating the glass material into two or more and opening the lower part. For example, as shown in FIG. 6, when the glass material 1 is softened by heating the glass material 1 on the floating jig 10, the floating jig 10 is divided into two parts 10a and 10b horizontally as shown in FIG. The glass material 1 falls by moving in opposite directions (left and right in the figure). At this time, the glass material 1 can be transferred onto the molding surface 40 of the lower die 34 by installing the lower die 34 of the molding die as a receiver for the falling glass material 1.

Furthermore, in the present invention, a 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, a cylindrical guide means 50 (dividable 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 at the upper portion of the floating jig 10. The glass material 1 can be dropped at 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 shifting when the floating jig is divided and moved. For example, it is not limited to a cylindrical shape, and may be a plurality of pipes arranged in a lattice shape or two or more opposing plates. 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 and press-molds onto the lower mold holding the glass material during molding.

  There is no particular limitation on the method of dividing and moving the floating jig used to heat the glass material. For example, when the levitating jig moves horizontally as described above, the levitating jig is divided into three or four, and moved in three directions (different directions by 120 °) or four directions (different directions by 90 °). Then, the glass material can be dropped. By dropping and moving the heat-softened glass material, the glass material can be transferred into the mold in a short time.

According to the present invention, it is a method for producing a glass optical element by press molding with a preheated mold such as a heat-softened glass preform, which can significantly reduce the cycle time required for press molding, It is possible to provide a method for molding a glass optical element which can be stably obtained even with a lens having a thin edge thickness and has good shape transferability.
Furthermore, according to the present invention, it is possible to provide a method for molding a glass optical element having no surface defects such as sink marks and surface shape distortion and having high surface accuracy.
Further, according to the present invention, there is provided a glass optical element molding method capable of producing a glass optical element having no surface defects such as sink marks and surface shape distortion and having high surface accuracy and having a center thickness within an allowable tolerance. be able to.
That is, according to the present invention, the cycle time required for press molding is greatly reduced and the surface is compared with the conventional technique (5 to 20 minutes / cycle) in which the mold and the glass preform are heated together. A glass optical element having no defects and high surface accuracy can be produced.
Further, according to the present invention, it is possible to provide a method for molding a glass optical element while completely preventing glass fusion (adhering) to a molding surface.

Next, an example explains the present invention.
Examples 1-1 to 1-5
As shown in FIG. 1, the press mold is a silicon carbide (SiC) sintered body 31 as a base material, processed into a press mold shape by grinding, and further formed by CVD on the molding surface side. A silicon carbide film 32 was formed, and further mirror-finished to a shape corresponding to a glass molded body to be manufactured by grinding and polishing to obtain a mold base. Further, an i-carbon (diamond-like carbon) film 33 is formed on the forming substrate silicon carbide film 32 by an ion plating method to have a molding surface 40, φ18 mm (φ15 mm after centering) biconvex glass lens The lower mold 34 for was obtained.

  The upper mold 35 shown in FIG. 5 was also obtained by the same method as the lower mold 34 described above. As shown in FIG. 5, the upper die 35 and the lower die 34 are set on the same axis, and in the case of press molding, the upper die 35, the lower die 34, and the guide die 36 that guides the molding die 39 constitute the molding die 39. Has been. Further, a push rod 45 for secondary pressurization is provided on the upper surface of the upper die 35.

  The lower die 34 and the upper die 35 are heated by a molding die heater 44 attached to the outer periphery of the body die 37 and controlled by a thermometer 42 for measuring the temperature of the die inserted into the lower die 34 from the lower part of the molding die support base 38. Is done. Further, the temperature of the body mold 37 is measured by a body temperature measuring thermocouple 43 inserted into the body mold 37.

2. Levitation jig and transfer means The levitation jig and transfer means shown in FIG. 2 are also provided in the same sealed chamber (not shown) having the above-described mold heating mechanism.
First, a glass softening heater 14 for heating and softening the glass material (preform) 1 is provided, and in this glass softening heater 14, a glassy carbon levitation jig 10 (hereinafter referred to as GC levitation) set on a levitation jig support base 13 is provided. Called a jig). Further, the glass material 1 is composed of 98% N ₂ + 2% H ₂ gas (Examples 1-1 to 1-1) of the flow rate shown in Table 1 supplied from the inside of the levitation jig support base 13 to the lower part of the GC levitation jig 10. -3) or N ₂ gas (Examples 1-4 to 1-5) is kept floating.
Further, outside the glass softening heater 14, there is a glassy carbon vacuum pad 15 (hereinafter referred to as a GC vacuum pad) that is movable in the vertical and horizontal directions, and is normally waiting on the GC floating jig 10.

Preheating and pressing process After evacuating the inside of a closed chamber (not shown) of a molding machine containing the press forming mechanism and glass heating mechanism described above, the 98% N ₂ + 2% H ₂ gas or N ₂ gas is supplied. It was introduced and the inside of the sealed chamber was made the same gas atmosphere.
Next, an example using a preform 1 made of barium borosilicate optical glass (marble-shaped hot-formed product having a mirror surface without surface defects, weight 1000 mg, transition point 534 ° C., yield point 576 ° C.) is shown. The mold heater 44 is heated until the temperature of the upper mold 35 and the lower mold 34 (mold temperature) measured by the thermocouple 43 for mold temperature measurement reaches a temperature corresponding to the glass viscosity shown in Table 1. Hold at the same temperature. In addition, the relationship between the viscosity of glass and temperature is as follows.
Glass viscosity Temperature 10 ⁹ poise 614 ° C
10 ¹⁰ poise 592 ° C
10 ¹¹ poise 572 ° C
10 ¹² poise 554 ° C
10 ^12.7 poise 543 ° C
10 ^13.4 poise 534 ° C
10 ^14.5 poise 518 ° C

On the other hand, the glass softening heater 14 heats the temperature of the glass preform 9 on the GC levitation jig 10 to a temperature corresponding to the viscosity of the glass shown in Table 1. In addition, the relationship between the viscosity of glass and temperature is as follows.
Glass viscosity Temperature 10 ^5.5 poise 718 ° C
10 ^6.4 poise 686 ℃
10 ^7.3 poise 658 ℃
10 ^8.2 poise 634 ° C
10 ^8.8 poise 619 ℃

  Then, the GC vacuum pad 15 waiting on the GC floating jig 10 outside the glass softening heater 14 is lowered to the preform 1 and held 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 of the low temperature.

Next, as shown in FIG. 4, the GC vacuum pad 15 holding the preform 1 moves quickly to above the lower mold 34 and again descends to the vicinity of the molding surface 40 of the lower mold 34 and simultaneously stops suction. The preform 1 is placed on the molding surface 40 of the lower mold 34. Thereafter, the GC vacuum pad 15 retreats from above the lower die 34 and returns to the original standby position, so that there is no obstacle on the upper portion of the lower die 34, and the molding die support base 38 instantaneously removes the lower die 34 and the lower die 34. The upper die 35 is moved up to the upper die 35 fixedly set together with the molding die support base 38 on the same axis. As shown in FIG. 5, the preform 1 is press-molded at a pressure of 100 kg / cm ² 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 upper die 35 and the lower die 34. Thus, the thickness where the flange portion of the lower die 34 and the bottom surface of the guide die 36 are in contact with each other is set to be 30 μm larger than the thickness of the final product. On the other hand, 20 kg / cm ² (20 kg / cm ² (on the back surface of the upper die 35) with the push rod 45 connected to the second cylinder inside the first cylinder after 5 seconds from the start of pressurization in the first cylinder. The glass molded body 2 and the molding die 39 are pressurized and held at a pressure of 1-1 to 1-5). Subsequently, the mold heater 44 is cooled by shutting off, and after the elapse of time shown in Table 1 as molding time (initial pressurization time (10 seconds) + secondary pressurization time), a thermocouple for measuring the mold temperature is used. When the temperature of the upper mold 35 and the lower mold 34 measured at 42 becomes the temperature shown in Table 1 as the mold temperature at the time of release, and the glass molded body 2 reaches a predetermined thickness, the glass molded body is changed from the molding mold 39 to the glass molded body. 2 was released and removed. In addition, the relationship between the viscosity of glass and temperature is as above-mentioned.

  The performance of the glass molded body 2 thus obtained (biconvex lens having an outer diameter of φ18 mm, a wall thickness of 2.9 mm, and an edge thickness of 1.0 mm) after annealing, surface accuracy by an interferometer, visual appearance, and stereomicroscope The surface state was evaluated, and 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 2-5
The mold for press molding The same press mold as shown in FIG. 8 except that the push bar 45 is not used was used.
Levitation jig In the same sealed chamber (not shown) having the above-described mold heating mechanism, the levitation jig 10 (10a, 10b), the guide means 50 (50a, 50b) and the glass material shown in FIG. 6 are heated. A softening glass softening heater (not shown) is provided. The levitation jig 10 is a divided levitation jig (hereinafter referred to as a GC division levitation jig) made of glassy carbon, and the guide means 50 is also a divided cylindrical guide (hereinafter referred to as a GC division cylindrical guide) made of the same material. is there. Furthermore, the glass material 1 is levitated and held by the ejection of 98% N ₂ + 2% H ₂ gas at a flow rate shown in Table 1 supplied from the inside of the GC split levitation jig.

Heat softening and pressing process After evacuating the inside of the closed chamber of the molding machine containing the press forming mechanism and the glass heating mechanism described above, 98% N ₂ + 2% H ₂ gas was introduced, and the inside of the closed chamber was in the same gas atmosphere. It was.
Next, the forming mold heater 44 shown in FIG. 8, the mold temperature above was allowed measured by temperature measuring thermocouple 43 type 35 and the lower mold 34 is similar to Example 1 of the viscosity of the glass material 1 10 ¹¹ The mixture was heated to 572 ° C. corresponding to Poise (Examples 2-1 to 2-3, 2-5) or 554 ° C. corresponding to 10 ¹² Poise (Example 2-4) and kept at the same temperature. At this time, the upper mold and the lower mold are heated at different positions, respectively, and are assembled as an integral mold as shown in FIG.
On the other hand, as shown in Table 1, the temperature of the glass material 1 on the GC split levitation jig 10 is heated and held to 718 ° C., which is a temperature corresponding to a glass viscosity of 10 ^5.5 poise, with a glass softening heater.

  Next, the GC split levitation jig 10 that floats and holds the heat-softened glass material 1 moves to the position immediately above the lower die 34, and then, as shown in FIG. 7, the GC split levitation jig 10a and the GC split levitation jig. The glass material 1 is dropped and placed on the molding surface 40 of the lower die 34 by 10b moving and opening instantaneously in the horizontal direction. At this time, 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 immediately above the GC divided levitation jig 10. When the jig 10 is opened and the glass material 1 is dropped, it serves as a guide that minimizes the amount of misalignment between the glass material 1 and the lower mold 34.

After the glass is dropped, the GC-divided cylindrical guide 50a and the other 50b move in the horizontal direction and open. Therefore, there is no obstacle at the upper part of the lower mold 34, and the mold support base 38 instantaneously reaches the upper mold 35 fixedly set together with the mold support base 38 in the same manner as the lower mold 34. As shown in FIG. 8, the glass material 1 is pressure-molded at a pressure of 100 kg / cm ² for 10 seconds in a molding die composed of a guide die 36 for guiding the upper die 35 and the lower die 34 as shown in FIG. After the predetermined thickness is reached, the pressure is set to 50 kg / cm ² at a stretch, and at the same time, the glass molded body 2 and the mold held at this pressure are allowed to cool by turning off the mold heater 14, and Table 1 Table 1 shows the temperatures of the upper mold 35 and the lower mold 34 measured with the thermocouple 43 for mold temperature measurement after the elapsed time shown as the molding time (initial pressurization time (10 seconds) + secondary pressurization time). When the temperature corresponding to the viscosity shown as the mold temperature is reached, The glass molded body 2 was released from the mold.

The performance of the glass molded body 2 thus obtained (biconvex lens having an outer diameter of φ18 mm, a wall thickness of 2.9 mm, and an edge thickness of 1.0 mm) after annealing, surface accuracy by an interferometer, visual appearance, and stereomicroscope The surface condition was evaluated and the results are shown in Table 1. Evaluation was performed on five lenses obtained by the same method.
Table 1 shows the evaluation results of the glass moldings obtained by changing the temperature of the softened glass material 1, the shape of the glass material 1, the gas flow rate flowing out of the GC split levitation jig, the mold temperature, and the mold release temperature. Indicates. As a result, all the molded bodies (lenses) were good.

Examples 3-1 to 3-3
Except that the initial pressurization time was 5 seconds (Example 3-1), 30 seconds (Example 3-2) or 55 seconds (Example 3-3), the glass molded body (outside A biconvex lens having a diameter of 18 mm, a wall thickness of 2.9 mm, and an edge thickness of 1.0 mm was obtained. The performance of the glass molded body after annealing was evaluated with respect to surface accuracy by an interferometer, visual appearance, and surface condition by a stereoscopic microscope. The results are shown in Table 1.

Examples 4-1 to 4-2
The mold 39 was allowed to cool down at the same time as the initial pressurization (pressurization at a pressure of 100 kg / cm ² ) (Example 4-1) or 5 seconds after the start of the initial pressurization (Example 4-2). A glass molded body (a biconvex lens having an outer diameter of 18 mm, a wall thickness of 2.9 mm, and an edge thickness of 1.0 mm) was obtained in the same manner as in Example 1-1. The performance of the glass molded body after annealing was evaluated with respect to surface accuracy by an interferometer, visual appearance, and surface condition by a stereoscopic microscope. The results are shown in Table 1.

The glass molded body was evaluated as follows.
Surface accuracy ○: Asses, habits 0.5 or less ◎: Asses, habits 0.2 or less Surface condition ◎: Good

In the above Examples 1 to 4, the cycle time is the sum of the molding time and the mold temperature recovery time (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 was about 85 to 165 seconds.
By using high-frequency heating or infrared heating for heating the mold, the recovery time can be about 10 seconds, and the cycle time can be shortened accordingly.

It is a schematic explanatory drawing of the lower mold | type of the shaping | molding die used by this invention. It is a schematic explanatory drawing of the floating softening and transfer method of the glass preform on the floating jig | tool used by this invention. It is a schematic explanatory drawing of the floating softening method of the glass preform on the floating jig | tool used by this invention. It is a schematic explanatory drawing of the transfer method to the shaping | molding die of the softened glass preform. It is a schematic explanatory drawing of the press molding with the shaping | molding die used by this invention. It is a schematic explanatory drawing of the transfer method to the shaping | molding die of the softened glass preform. It is a schematic explanatory drawing of the transfer method to the shaping | molding die of the softened glass preform. It is a schematic explanatory drawing of the press molding in a shaping | molding die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glass raw material 2 ... Glass molded object 10, 17 ... Levitation jig 10a, 10b ... Dividing levitation jig 11 ... Upper opening part 12 of levitation jig ... Levitation jig The bottoms 13 and 19 of the upper openings of the levitation jig support 14 ... the heater for glass softening 15 ... the suction holding device 16 ... the lower opening 18 ... the porous surface 34 ... Lower die 35 ... Upper die 36 ... Guide die 37 ... Body die 40, 41 ... Molding surface 45 ... Push rod 50a, 50b ... Guide means

Claims (6)

A method of molding a glass optical element by press-molding a heat-softened glass material with a preheated mold,
The preheating temperature of the mold is set to a temperature corresponding to a viscosity of the glass material of 10 ⁹ to 10 ¹² poise, and the preheating temperature of the glass material is higher than the preheating temperature of the mold , as the temperature at which the viscosity of the glass material corresponds to less than 10 ⁹ poise, the initial pressurizing the glass material was heated and softened by preheating in a mold and the preheating,
Simultaneously with the start of the initial pressurization or in the middle of the initial pressurization, the cooling of the vicinity of the molding surface of the mold is started,
After the initial pressurization, secondary pressurization is performed at a pressure of 5 to 70% of the initial pressurization,
A method for molding a glass optical element, wherein the glass molded body is released from the molding die after the temperature in the vicinity of the molding surface is equal to or lower than the temperature corresponding to 10 ¹² poise of the glass material. The molding method according to claim 1, wherein the molding surface vicinity of the mold is cooled simultaneously with the initial pressurization. 2. The molding method according to claim 1, wherein cooling of the vicinity of the molding surface of the mold is started after the initial pressurization is started and in the middle of the initial pressurization. The said secondary pressure WHEREIN: The center wall thickness of a glass molded object is pressure-deformed in the range of 0.001-0.12 mm, The any one of Claims 1-3 characterized by the above-mentioned. Molding method. The molding method according to any one of claims 1 to 4 , wherein the temperature of the preheating of the glass material is a temperature corresponding to a viscosity of the glass material of 10 ^5.5 to 10 ^7.6 poise. The mold cooling, and carrying out at 20 ° C. / min or more cooling rate, forming method according to any one of claims 1-5.

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