JPH08133756A - Production of glass optical element - Google Patents

Abstract

PURPOSE: To reduce the cycle time necessary for press forming and to obtain a glass optical element without any surface flaw and high in profile irregularity by preheating a preform while floating it up with an air current, transferring the preform in a forming die and press-forming the preform. CONSTITUTION: A glass preform is preheated >=30 deg.C lower than the glass transition point. The preform preheated and softened is transferred to a preheated forming die while holding the softened preform by suction with a suction holder 15 having a movable lower opening 16. The opening 16 is communicated with a pressure reducing pump, vacuum pump, etc. A glass preform 1 held by a holder 14 and softened on a floating jig 10 is floated and held by the injection of a gas (contg. 98% N2 and 2% H2 , for example) supplied from within a floating jig support 13. A glassy-carbon vacuum pad 15 movable vertially and horizontally is placed outside the heater 14 and allowed to stand by at the upper part.

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 glass lens which does not require grinding and polishing after press molding. In particular, the present invention relates to a method for manufacturing a glass optical element capable of significantly reducing the cycle time required for press molding and improving the production speed.

[0002]

2. Description of the Related Art A glass preform, which is a glass material to be molded, is press-molded with a molding die having a surface precision and a surface roughness required for the surface of the glass molded body, and the grinding and polishing after the press molding is unnecessary. Various methods have been conventionally known as a method for manufacturing an optical element. For example, JP-A-64
The method described in Japanese Patent Publication No. 72929 or Japanese Examined Patent Publication No. 16251/1990 is a method of heating the molding die and the glass preform together. That is, a glass preform is inserted into a forming die including an upper die, a lower die, and a guide die for guiding them, and the glass preform is heated to a temperature at which the preform is sufficiently softened, and then press-molded. Next, after cooling to near the glass transition temperature at a cooling rate that does not impair the surface accuracy of the molded glass after molding (or cooling to near room temperature for a certain period of time), A glass molded body is taken out from.

On the other hand, a method of inserting a pre-softened glass preform into a heated mold separately from this is described in JP-A-62-113730 or JP-B-63-46010. . That is, the glass preform held on the ring-shaped member was heated and softened together with the ring-shaped member, inserted into the molding die together with the ring-shaped member, and then the lower mold penetrated through the inner wall of the ring-shaped member to be softened. The preform is lifted and pressure molding is performed between the preform and the upper mold. Alternatively, the ring-shaped member serves as a body for guiding the upper die and the lower die, and is press-molded.

Further, in the method of molding a glass preform inserted into a molding die by using a ring-shaped member, the temperature condition for prolonging the life of the molding die is disclosed in JP-A-62-27.
No. 334 publication. That is, after the mold temperature is maintained in the temperature range from below the transition point of the glass to 200 ° C. lower than the transition point, and the temperature of the glass preform is heated so that the viscosity of the glass is in the range of 10 ⁶ to 10 ⁸ poises. , Insert into the mold and press mold.

[0005]

In the method in which the preform is heated, molded, and cooled together with the molding die in the state where the glass preform is held in the molding die, the temperature of the glass and the molding die is almost constant. As the pressing process progresses equally, there is no difference in temperature between the surface and the inside of the glass, so sink marks are less likely to occur and stable surface accuracy can be obtained. However, there is a drawback in that the cycle time required for all steps is remarkably lengthened because the temperature rising time before starting the press and the cooling time required for taking out after the press are required. Further, since the contact time between the glass and the mold surface in the steps of heating to pressing is long, there is a drawback that a reaction easily occurs between the glass and the mold surface and the mold life is shortened.

On the other hand, in the method of press-molding the glass preform which has been previously heated to a temperature (low viscosity) higher than that of the molding die by using the ring-shaped member as the inserting means, the pressing time is very short. Further, the temperature of the mold can be made relatively low, and the mold can be released if a certain time is allowed to cool the glass temperature after pressing, so that the cycle time can be greatly shortened. However, when the preform is inserted into a molding die at a low temperature (a temperature range lower than the transition point of glass to 200 ° C. lower than the transition point) for the purpose of prolonging the life of the molding die, the temperature of the glass surface sharply decreases, There is a problem that the glass is cooled and solidified before press molding to a desired wall thickness.

As a countermeasure against this, it has been proposed to use a glass preform having a lower viscosity under similar temperature conditions. However, the lower the viscosity, the softer the preform on the ring-shaped member falls from the opening of the ring-shaped member (deforms and sags). For example, depending on the shape of the preform, when the viscosity is 10 ⁷ poises or less, the tendency to cause the sag is large. Therefore, the outer diameter of the preform must be considerably larger than the inner diameter of the preform supporting portion of the ring-shaped member in order to prevent the preform from falling from the ring-shaped member. However, as a result, the lens after press molding becomes remarkably larger than the desired outer diameter, and it is necessary to largely scrape off the lens to the desired outer diameter in a later step. In addition, in the method using this ring-shaped member, since a preform larger than the final product is used, a surplus protruding portion is generated and the temperature of the molding die is low, so that it is not possible to manufacture a biconvex lens or a meniscus lens with thin edges. It's extremely difficult.

Therefore, an object of the present invention is a method for producing a glass optical element by press-molding a preheated and softened glass preform with a preheated mold.
An object of the present invention is to provide a method capable of manufacturing a glass optical element by using a glass preform that softens to have a low viscosity and is easily deformed to preheat and soften the glass preform while easily holding it. Further, the object of the present invention is to transfer the preheated and softened and easily deformable glass preform to a molding die without causing large deformation,
An object of the present invention is to provide a method capable of favorably manufacturing a glass optical element.

It is another object of the present invention to use a glass preform having a size that substantially satisfies the desired effective outer diameter of the target glass optical material, and to provide a glass optical element capable of minimizing the centering allowance in the subsequent step. It is to provide a manufacturing method. A further object of the present invention is to provide a manufacturing method capable of significantly shortening the cycle time required for press molding and obtaining a glass molded body having high surface accuracy without surface defects. In addition, another object of the present invention is to provide a method capable of easily manufacturing a biconvex lens or a meniscus lens having a thin edge. It is another object of the present invention to provide a method capable of favorably manufacturing a glass optical element by transferring a glass gob which is softened by heating and easily deformed to a molding die.

[0010]

The first aspect of the present invention is as follows.
A preheated and softened glass preform is a method for producing a glass optical element by press-molding with a preheated mold, wherein the preform is preheated by heating while floating the preform by an air flow. ,
In addition, the present invention relates to a method for producing a glass optical element, characterized in that the preheated and softened preform is transferred to the preheated mold and then press-molded.

Further, a second aspect of the present invention is a method for producing a glass optical element by press-molding a glass gob which is softened by being heated while being floated by a preheated mold, wherein the glass optical element is heated and softened. The glass optical element characterized in that the glass gob is suction-held or placed on a ring-shaped mounting tool having an inner diameter smaller than the outer diameter of the glass gob, transferred to the preheated mold, and then press-molded. Manufacturing method. The present invention will be described below.

A first aspect of the present invention is a method for producing a glass optical element by press-molding a preheated and softened glass preform with a preheated mold. The glass preform refers to a molded product molded into a predetermined shape to be used as a precursor when molding a glass optical element. The glass preform may be formed by cold forming or hot forming of molten glass, and may be mirror-polished or the like. However, the surface of the preform may be a rough surface instead of a mirror surface, for example, # 800
It is also possible to use the ground product ground with the diamond as a glass preform.

The type of glass constituting the glass preform, the shape of the glass preform, and the like are conventionally known. However, the glass preform used in the present invention is preferably used with a relatively low viscosity. For example, it is preferable to exhibit a viscosity of 10 ^5.5 to 10 ^9.0 poise in a preheated and softened state. The shape of the preform is determined in consideration of the size and capacity of the glass optical element that is a product, the amount of change during molding, and the like. further,
At the time of molding, in order to prevent a gas trap from occurring, it is preferable that the center of the molding surface is in contact with the surface to be molded of the preform first. The capacity of the glass preform is preferably larger than that of the final product by a slight amount of centering performed in the subsequent step. 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.

A second aspect of the present invention is a method for producing a glass optical element by press-molding a glass gob that is heated and softened while being floated with a preheated mold. The glass gob is a glass piece obtained by dividing molten glass into a predetermined volume, and the glass preform is formed by further shaping the glass gob into a predetermined shape. There is no particular limitation on the type of glass constituting the glass gob.

As the mold used in the present invention, a conventionally known mold can be used as it is. For example, a structure where pressure is applied to the molded product (optical element) during cooling after molding,
The structure may be such that the pressure can be reduced after the initial pressurization. Further, the pressure after the initial pressure may be applied by the weight of the upper mold. Further, a resistance heater, a high frequency heater, an infrared lamp heater, or the like can be used for heating the mold. In particular, a high-frequency heating heater and an infrared lamp heater are preferable from the viewpoint that the recovery time of the mold temperature is short. Further, the molding die can be cooled by disconnection cooling, cooling gas flowing in the molding die, or the like.

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. 6 can be used. However, it is not limited to these. Further, as a molding die, a silicon carbide sintered body on which a silicon carbide film is formed by a CVD method and then an i-carbon film is formed by an ion plating method can be used. Furthermore, silicon, silicon nitride, tungsten carbide, cermet of aluminum oxide and titanium carbide, diamond on these surfaces,
Those coated with ceramics such as refractory metals, noble metal alloys, carbides, nitrides, borides, and oxides can also be used. However, a carbon-based film such as an i-carbon film is particularly advantageous in that it has good releasability. The pressure molding conditions can be appropriately determined in consideration of the temperature of the preform or gob, the temperature of the molding die, and the like. Normally 30-200kg / c
It can be molded by pressing at a pressure of m ² for 3 to 60 seconds, preferably 5 to 30 seconds. Further, the temperature of the preform and gob, the temperature of the molding die and the temperature of the mold release can be appropriately selected.

The manufacturing method of the present invention is characterized in that the glass preform is heated while being floated by an air current to preheat the preform, and the preheated and softened preform is transferred to the preheated mold. Is.
In a low-viscosity region where the glass preform is deformed by its own weight, it is not easy to prevent fusion between the jig holding the preform and the glass during heating. In the present invention, for example, the glass preform is floated by the air flow by ejecting gas from the inside of the jig. Gas layers are formed on both the jig surface and the glass surface, so that the jig and the glass do not react with each other, and it is possible to heat and soften the glass preform while maintaining the shape of the glass preform.

In the present invention, there is no particular limitation on the gas used as the air flow for floating the preform. However, it is preferable that the heated glass preform does not react with the jig, and from the viewpoint of preventing deterioration of the heated jig due to oxidation, that it is a non-oxidizing gas,
For example, nitrogen or the like is suitable. Further, 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 from which the airflow is blown, the shape and weight of the preform, and the like. Normally,
A gas flow rate of 0.005 to 20 liters / minute is suitable for floating the glass preform. However, if the gas flow rate is less than 0.005 liters / minute, the preform may not be sufficiently floated up when the weight of the glass preform is 300 mg or more. Also, 20
If it exceeds liter / minute, even if the weight of the glass is 2000 mg or more, the glass on the levitation jig may shake greatly and the shape of the preform may change during heating. Furthermore, the preheating conditions of the preform can be appropriately changed depending on the type of glass and the like, and are adjusted so that the viscosity required for the softened preform is obtained.

The floating of the preform by the air flow can be performed, for example, by an air flow flowing upward from an upper opening having an opening diameter smaller than, equal to, or larger than the diameter of the preform. For example, in the case of the upper opening having an opening diameter smaller than the diameter of the preform, the levitation jig 1 supported by the levitation jig support 13 as shown in FIG.
The upper opening 11 of 0 is smaller than the diameter of the glass preform 1, and the preform 1 floats above the upper opening 11 due to the airflow flowing upward from the bottom 12 of the upper opening 11 of the levitation jig 10. , Is held so as not to contact the floating jig 10. The preform 1 is heated by the glass softening heater 14 provided around the preform 1. In addition, at least 1 for supplying an air flow to the bottom 12 of the upper opening 11.
There can be one opening. The floating of the preform by the air flow can also be performed by the air flow flowing out from a porous surface having a spherical surface or a flat surface that approximates the curvature of the preform. As shown in FIG. 3, the levitation jig support 19
The preform 1 is held in a levitated state by the air flow flowing out from the porous surface 18 on the levitation jig 17 having a porous surface 18 having a spherical surface that is close to the curvature of the preform 1 supported by the preform 1. . Also in this case, preform 1
Is heated by the glass softening heater 14 provided in the periphery.

Further, the glass preform is preheated by first heating the glass preform from the glass transition point to 30 ° C.
It can also be carried out by heating to a lower temperature as described above and then softening by heating the heated glass preform to a predetermined temperature while floating the glass preform by an air stream. This state is shown in FIG. As shown in FIG. 4, first,
The glass preform 1 is heated on the glass holding jig 20 to a temperature lower than the glass transition point by 30 ° C. or more. Next, the heated glass preform 1 is transferred onto a floating jig 10 similar to that shown in FIG. 2 by an appropriate transfer means, that is, a suction holding transfer device described later in FIG. 4, and further heated while being floated by an air flow. To do. In FIG. 4, a floating jig similar to that of FIG. 2 is shown, but the floating jig shown in FIG. 3 can also be used. Also, the heated glass preform 1
In addition to the suction holding, for example, a ring-shaped mounting tool can also be used for the transfer of.

The preheated and softened preform can be transferred to the preheated mold while the softened preform is suction-held. For example, it can be performed by the suction holding device 15 having the movable lower opening 16 shown in FIG. The lower opening 16 is connected to a vacuum pump, a vacuum pump, or the like that sucks inward, and the preform can be sucked and held in the lower opening 16. The glass preform 1 that has been heated and softened on the floating jig 10 is suction-held in the lower opening 16 of the movable suction-holding device 15, and as shown in FIG. 5, the molding surface of the lower mold 34 of the molding die. 40. Next, as shown in FIG. 6, the softened preform 1 is press-molded by the molding surface 40 of the lower mold 34 and the molding surface 41 of the upper mold 35 to obtain the glass optical element 2.

Suction holding of the preform that has been preheated and softened can also be performed by suction from a suction port provided in the vicinity of the molding surface of the upper mold. For example, as shown in FIG. 7, the guide die 3 located near the molding surface 41 of the upper die 35 of the molding die.
The suction can be performed by suction from the suction port 45 provided in No. 6. As shown in FIG. 7, a guide mold 36 in which the softened preform 1 on the floating jig 10 is set together with the upper mold 35.
Of the preform 1 is sucked from the suction port 45 of the guide die 36 to suck up the preform 1 onto the molding surface 41 and suck it. Then, the floating jig 10 is moved and removed, and the lower mold is moved under the softened preform, or the softened preform sucked and held in the vicinity of the molding surface of the upper die of the molding die is removed from the molding surface of the lower die. It is also possible to move upward and perform press molding with the molding surface of the upper mold and the molding surface of the lower mold (FIG. 9).

Transfer of the preheated and softened preform to the preheated mold is performed by placing the preform on a ring-shaped placing tool having an inner diameter smaller than the outer diameter of the preform, and placing the preform on the placing tool. Can also be carried out while suction-holding. For example, as shown in FIG. 11, the outer diameter of the upper opening of the levitation jig 10 is slightly larger than that of the preform 1.
The ring-shaped member 23 having an inner diameter smaller than the outer diameter is installed so that the upper opening of the levitation jig 10 is inserted into the ring of the ring-shaped member 23. Then, after the preform is softened to a predetermined viscosity, the preform 1 is softened by being heated while floating on the floating jig 10, and the ring-shaped member 2
Place on 3 and transfer. For the transfer by the ring-shaped member 23, the vacuum pad 24 capable of suction-holding the ring-shaped member 23 is illustrated in FIG. However, there is no limitation on the transfer method using the ring-shaped member. Then, as shown in FIG. 11, the preform 1 is placed on the lower surface 34 of the mold and on the molding surface 40.
Is moved to a position where the preform 1 is placed, the suction of the vacuum pad 24 is stopped, and the preform 1 is placed on the molding surface 40. The preform 1 on the molding surface 40 is molded with the upper mold as shown in FIG.

Although the method of softening and molding the glass preform has been described above, the second aspect of the present invention also includes
A glass optical element can be manufactured by heating, transferring and molding a gob instead of the preform in the same manner as in the first aspect.

[0025]

EFFECT OF THE INVENTION According to the present invention, even when a glass preform whose viscosity becomes low and becomes easily deformed when softened,
A glass optical element can be manufactured by preheating and softening a glass preform while easily holding it, and then press-molding the softened glass preform with a preheated mold. Further, according to the present invention, it is possible to manufacture a glass optical element having good optical characteristics by transferring a glass preform that is preheated and softened and is easily deformed to a molding die without being largely deformed. Further, according to the present invention, by using a glass preform having a size substantially satisfying a desired effective outer diameter of a desired glass optical element, it is possible to manufacture a glass optical element capable of minimizing a centering margin in a subsequent step. You can Further, according to the present invention, it is possible to significantly reduce the cycle time required for press molding, and to manufacture a glass optical element having high surface accuracy without surface defects. In addition, according to the present invention, a biconvex lens or a meniscus lens having a thin edge can be easily manufactured. Further, according to the present invention, a glass gob that is softened by heating and easily deformed can be transferred to a molding die to manufacture a good glass optical element.

[0026]

The present invention will be described below with reference to examples. Example 1 Press Forming Mold As shown in FIG. 1, the press forming mold uses a silicon carbide (SiC) sintered body 31 as a base material, and after processing into a press forming mold shape by grinding, further on the forming surface side. A silicon carbide film 32 was formed by the CVD method, and was further ground and polished to give a mold base by mirror-finishing into a shape corresponding to a glass molded body to be manufactured. Furthermore, the silicon carbide film 3 of the mold base
The i-carbon film 33 is formed on the surface 2 by ion plating to a thickness of 500 Å and has a molding surface 40.
m (φ15 mm after centering) Lower mold for biconvex glass lens 34
I got The upper mold 35 shown in FIG. 6 was also obtained by the same method as the lower mold 34. The upper mold 35 and the lower mold 34 are shown in FIG.
As shown in FIG. 2, the upper mold 35, the lower mold 34, and the guide mold 36 that guides the same are set on the same axis during press molding.
The molding die 39 is composed of. Lower mold 34 and upper mold 3
The heating of No. 5 is performed by a mold heater 44 attached to the outer periphery of the barrel mold 37, and is controlled by a mold temperature measuring thermocouple 42 inserted into the lower mold 34 from the lower part of the mold supporting base 38. Further, the temperature of the body die 37 is measured by a body temperature measuring thermocouple 43 inserted in the body die 37.

Floating jig and transfer means The floating jig and transfer means shown in FIG. 2 are also provided in the same closed chamber (not shown) having the above-mentioned molding die heating mechanism. First, a glass softening heater 14 for heating and softening a glass material (preform) 1 is provided. Inside the glass softening heater 14, a glassy carbon floating jig 10 (hereinafter, G
C levitation jig) is arranged. Further, the glass material 1 is supplied from the inside of the levitation jig support base 13 to the lower portion of the GC levitation jig 10 at 100 ml / min of 98% N.
Suspended and held by the ejection of ₂ + 2% H ₂ gas. Also, outside the glass softening heater 14, a glassy carbon vacuum pad 15 that can move vertically and horizontally.
(Hereinafter, referred to as a GC vacuum pad), and normally stands by above the GC floating jig 10.

Preheating and Pressing Step After evacuating the inside of the closed chamber (not shown) of the molding machine in which the above-mentioned press molding mechanism and glass heating mechanism are housed, 98% N ₂ + 2% H ₂ gas is introduced. The inside of the closed chamber was set to the same gas atmosphere. Next, preform 1 made of barium borosilicate optical glass (a marble-shaped hot-molded product having a mirror surface with no surface defects, weight 1000 m
g, transition point 534 ° C., yield point 576 ° C.) so that the temperature of the upper mold 35 and the lower mold 34 measured by the mold temperature measuring thermocouple 43 is 576 with the mold heater 44. ℃
It heated until it became and was kept at the same temperature. On the other hand, the glass softening heater 14 heats the temperature of the glass preform 1 on the GC levitation jig 10 to 700 ° C. at which the viscosity of the glass becomes 10 ⁶ poise to soften the levitation. Then, the GC soft pad 15 standing by above the GC floating jig 10 outside the glass softening heater 14 descends to the preform 1 and sucks and holds the floating and softened preform 1. At this time, the temperature of the GC vacuum pad is 300 to 4 due to the radiant heat from the glass softening heater 14.
Since it is heated to 00 ° C, it is less likely to react with low viscosity glass.

Next, as shown in FIG. 5, the preform 1
The GC vacuum pad 15 holding the above rapidly moves to the upper side of the lower mold 34, descends again to the vicinity of the molding surface 40 of the lower mold 34, and at the same time stops suction, and the preform 1 is formed on the molding surface 40 of the lower mold 34. Put. After that, the GC vacuum pad 15 retracts from above the lower mold 34 and returns to the original standby position, so that there are no obstacles above the lower mold 34.
The upper mold 3 in which the lower mold 34 and the lower mold 34 are instantaneously fixedly set together with the lower mold 34 by the mold supporting base 38 instantly.
As shown in FIG. 6, the molding die 39 is composed of an upper die 35, a lower die 34, and a guide die 36 for guiding the same.
Inside, the preform 1 is pressure-molded for 10 seconds at a pressure of 100 kg / cm ² to have a predetermined wall thickness. Next, the molding die heater 44 is cut off to allow the glass molding 2 and the molding die 39 to cool, and after 70 seconds, the temperature of the upper mold 35 and the lower mold 34 measured by the mold temperature measuring thermocouple 42 is measured. However, when the temperature reached 534 ° C., which was near the glass transition point, the glass molded body 2 was released from the molding die 39 and taken out.

Glass molded body 2 thus obtained
The performance of the (outer diameter φ18 mm, wall thickness 2.9 mm, biconvex lens) after annealing was evaluated with respect to two points: surface accuracy by an interferometer, visual appearance, and surface state by a stereoscopic microscope, and the results are shown in Table 1. 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.

Example 2 The molding die, conditions and the like used were the same as in Example 1 except that the glass floating softening mechanism was changed. After the inside of the closed chamber of the molding machine in which the press forming mechanism and the glass heating mechanism are housed is evacuated, gas is introduced to make the inside of the closed chamber a 98% N ₂ + 2% H ₂ gas atmosphere. Next, the temperature of the upper mold 35 and the lower mold 34 is heated and held by the mold heater 44 so as to be near the sag point of the glass preform 1 (the same glass type and the same shape as in Example 1). did. Further, as shown in FIG. 3, the glass softening heater 14
The preform 1 on the porous ceramics floating jig 17 set on the floating jig supporting base 19 is supplied from the inside of the floating jig supporting base 19 to the lower portion of the porous ceramics floating jig 17. ₂ Gas is jetted at 200 ml / min through the pores of the levitating jig material to be levitated, and heated and held at 700 ° C. where the viscosity of the glass becomes 10 ⁶ poise.

Next, the GC vacuum pad (not shown) standing by above the porous ceramic levitation jig 17 outside the glass softening heater 14 descends to suck and hold the pre-float softened preform 1. Then, as shown in FIG. 5, the GC vacuum pad quickly moves to above the lower mold 34 and again descends to the vicinity of the surface of the lower mold 34, and at the same time, stops suction and preforms on the molding surface 40 of the lower mold 34. 1
, And the GC vacuum pad retracts to its original standby position. Next, the molding die support base 38 moves the lower die 34 to the lower die 34.
The upper mold 3 shown in FIG.
The glass material 1 is placed in a molding die 39 composed of a guide die 36 for guiding the lower die 34 and the lower die 34, and the glass material 1 is 100 kg / cm for 10 seconds.
Pressure molding is performed at a pressure of ² to obtain a predetermined wall thickness. Next, the molding die heater 44 was cut off, and after 70 seconds, when the temperature of the upper mold 35 and the lower mold 34 reached 534 ° C., which was near the glass transition point, the glass molded body 2 was released from the molding die 39. I took it out. Glass molded body 2 thus obtained
The performance after annealing (having the same shape as that of Example 1) is shown in Example 1.
It evaluated similarly to. The results are shown in Table 1.

Example 3 Example 3 was repeated except that the glass floating softening mechanism was changed. After evacuating the closed chamber of the molding machine containing the press molding mechanism and the glass heating mechanism,
98% N ₂ + 2% H ₂ gas is introduced to make the inside of the closed chamber the same gas atmosphere. Next, glass preform 1
The temperature of the upper mold 35 and the lower mold 34 is heated and maintained at 576 ° C. so as to be near the sag point of the same glass type and the same shape as in Example 1. Further, as shown in FIG. 4, the preform 1 was first placed on the glass holding jig 20 set on the holding jig support base 21 in the glass preheating heater 22 at a temperature lower than the glass transition point by 30 ° C. And hold at 504 ° C. At this time, since the preform 1 is not softened to have fluidity, it is not necessary to levitate from the glass holding jig 20. Next, the GC vacuum pad 1 that was standing by above the glass holding jig 20 outside the glass preheating heater 22
5 descends to hold the preform 1 by suction and preheat it in the glass softening heater 14 at a temperature higher than the glass transition temperature of 20.
The tungsten alloy levitation jig 10 heated and held at 335 ° C. is moved so that the temperature becomes 0 ° C. lower. Next, as it descends, suction is stopped and the preform 1 is placed on the receiving portion of the floating jig 10 and then the GC vacuum pad 1
5 is made to stand by above the glass softening heater 14.

200 ml supplied from the inside of the levitation jig support 13 to the tungsten alloy levitation jig 10
The preform 1 on the levitation jig 10 which was floated and held by the injection of 98% N ₂ + 2% H ₂ gas at a flow rate of / min was rapidly heated by the glass softening heater 14 to 700 ° C. at which the viscosity of the glass became 10 ⁶ poise. To heat. At this time, since the temperature of the tungsten alloy levitation jig 10 was 170 ° C. lower than the glass temperature when the preform 1 was placed, the temperature was always lower than the glass temperature even in the subsequent rapid heating. The tool 10 and the glass did not react. Next, the floated and softened preform 1 is moved down to the lower mold 34 after the GC vacuum pad 15 standing by above the glass softening heater 14 is lowered and the preform 1 is suction-held. At the same time, the suction is stopped at the same time as the lower mold 34 surface is lowered, the preform 1 is placed on the molding surface 40 of the lower mold 34, and the GC vacuum pad retracts to the original standby position.

Then, the molding die support base 38 moves the lower die 34
The preform 1 is raised to the upper mold 35 coaxially above the lower mold 34, and the preform 1 is held in the molding mold 39 shown in FIG. 6 for guiding the upper mold 35 and the lower mold 34 for 100 seconds.
It was pressure-molded at a pressure of kg / cm ² to a predetermined wall thickness. Then, the molding die heater 44 is cut off, and after 70 seconds, when the temperature of the upper die 35 and the lower die 34 reaches 534 ° C., which is near the glass transition point, the glass molding 2 is released from the molding die 39. I took it out. The glass molded body 2 (having the same shape as that of Example 1) thus obtained was evaluated for performance after annealing in the same manner as in Example 1. The results are shown in Table 1.

Example 4 Example 4 was repeated except that the mechanism for inserting the float-softening glass into the mold was changed. After the inside of the closed chamber of the molding machine in which the press forming mechanism and the glass heating mechanism are housed is evacuated, 98% N ₂ + 2% H ₂ gas is introduced to create the same gas atmosphere in the closed chamber. Next, the temperature of the upper mold 35 and the lower mold 34 is set to 5 so that the glass preform 1 (the same glass type and shape as in Example 1) is near the sag point.
It was kept heated to 76 ° C. Further, as shown in FIG. 7, the levitation jig support base 1 is set in a glass softening heater (not shown).
Preform 1 on the GC levitation jig 10 set to 3
Of 300% / min of 98% N ₂ +2 supplied from the inside of the levitation jig support 13 to the bottom of the GC levitation jig 10.
The glass was heated up to 700 ° C., at which the viscosity of the glass became 10 ⁶ poise, while being floated by the jetting of H ₂ gas. Next, the levitation jig support base 13 moves to the position where the pre-float softened preform 1 is located just below the upper mold 35.

Next, as shown in FIG. 8, the levitation jig support base 13
Moves up and moves the preform 1 to the vicinity of the surface of the upper mold 35, and then guides the upper mold 35 and the lower mold 34.
The inner wall is sucked through a suction hole 45 provided at a position corresponding to the side surface of the preform 1, and the preform 1 is sucked onto the surface of the upper mold 35. At the same time as the intake, the flow rate of the gas ejected from the levitation jig 10 is temporarily increased so that the preform 1
It is also possible to make the suction on the surface of the upper mold 35 smoother by pushing up. Next, the floating jig support base 1
3 retreats from under the upper mold 35 and returns to the original glass softening heater heating position. At the same time, the mold support 38 raises the lower mold 34 to the upper mold 35, and as shown in FIG. 9, in the mold 39 composed of the upper mold 35 and the guide mold 36 for guiding the lower mold 34, Preform 1 100kg / cm for 10 seconds
Pressure molding was performed at a pressure of ² to obtain a predetermined wall thickness. Next, the molding die heater 44 was cut off, and after 70 seconds, when the temperature of the upper mold 35 and the lower mold 34 reached 534 ° C., which was near the glass transition point, the glass molded body 2 was released from the molding die 39. I took it out. Glass molded body 2 thus obtained
The performance after annealing (having the same shape as that of Example 1) is shown in Example 1.
It evaluated similarly to. The results are shown in Table 1.

Example 5 FIGS. 10 to 12 show an outline of the apparatus and the molding die used in this example. The structure of the molding die is the same as that of the first embodiment.
First, after evacuating the closed chamber of the molding machine in which the press molding mechanism and the glass heating mechanism are housed, 98% N
₂ + 2% H ₂ gas is introduced to make the inside of the closed chamber the same gas atmosphere. Next, a glass preform 1 (a marble-shaped hot molded product having a mirror surface with no surface defects, weight 1
800 mg, transition point temperature 534 ° C, yield point temperature 576
The temperature of the upper mold 35 and the lower mold 34 is heated to 592 ° C. and maintained at the same temperature so that the viscosity of (° C.) becomes 10 ¹⁰ poise. On the other hand, as shown in FIG. 10, the preform 1 having a slightly larger outer diameter than the floating jig on the GC floating jig 10 set on the floating jig support base 13 by the glass softening heater 14 is From the inside of the levitation jig support base 13, the GC levitation jig 10
600 ml / min of 98% N ₂ + supplied to the bottom
While being floated by jetting 2% H ₂ gas, it is heated and held up to 660 ° C., which is equivalent to the glass viscosity of 10 ^7.2 poise. Next, the prefabricated softened preform 1 is standing by above the GC floating jig 10 outside the glass softening heater 14, and the GC vacuum pad 24 is lowered to a ring-shaped member installed in the vicinity of the GC floating jig 10. 23 is suction-held and at the same time rises again. At this time, the inner diameter portion of the ring-shaped member 23 pushes up the outer diameter portion of the preform 1 slightly larger than the outer diameter of the GC levitation jig 10 to lift and transfer the preform 1 together with the ring-shaped member 23. Since it is a short time, it does not naturally deform and fall from the ring-shaped member 23.

Next, as shown in FIG. 11, the GC vacuum pad 24 holding the ring-shaped member 23 on which the preform 1 is mounted is sucked and moved quickly to above the lower mold 34. Then, the suction is stopped at the same time when the preform 1 is lowered to the vicinity of the lower mold 34 again.
Further, the ring-shaped member 23 is mounted by the flange portion provided slightly below the molding surface. Thereafter, the GC vacuum pad 24 recedes from above the lower mold 34, and at the same time, the molding die support base 38 raises the lower mold 34 to the upper mold 35 coaxially above the lower mold 34, and as shown in FIG. And a guide die 36 for guiding the lower die 34
Preform 1 at 100 kg / cm ² for 10 seconds
Pressure molding was performed at a pressure of 1 to obtain a predetermined wall thickness. Next, the molding die heater 44 was cut off, and after 70 seconds, when the temperature of the upper mold 35 and the lower mold 34 reached 534 ° C., which was near the glass transition point, the glass molded body 2 was released from the molding die 39. I took it out. Glass molded body 2 thus obtained
The performance after annealing (φ25 mm, φ20 mm after centering, biconvex lens) was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0040]

[Table 1]

Example 6 Preform type (glass type and shape), floating gas flow rate,
A glass molded body was obtained in the same manner as in Example 1 except that the molding die temperature and the mold releasing temperature were set to the conditions shown in Table 2. The performance of the obtained glass molded body was evaluated in the same manner as in Example 1. Table 2 shows the results. All the glass molded products showed good performance.

[0042]

[Table 2]

In the above-mentioned embodiments of the present invention, the mold used was a silicon carbide sintered body on which a silicon carbide film was formed by the CVD method and then an i-carbon film was formed by the ion plating method. However, in addition, silicon, silicon nitride, tungsten carbide, cermet of aluminum oxide and titanium carbide, or diamond, refractory metal, noble metal alloy, or carbide, nitride on their surface,
Those coated with ceramics such as borides and oxides could be used. However, the i-carbon film of this example was advantageous in that it had good releasability.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of a lower die of a forming die used in an example.

FIG. 2 is a schematic explanatory diagram of a method of softening and transferring a glass preform on a floating jig used in Examples for floating and softening.

FIG. 3 is a schematic explanatory diagram of a method of softening the glass preform on the floating jig used in Examples for floating softening.

FIG. 4 is a schematic explanatory diagram of a method for softening the glass preform to float on a floating jig used in Examples.

FIG. 5 is a schematic explanatory view of a method of transferring a softened glass preform to a molding die.

FIG. 6 is a schematic explanatory view of press molding with a molding die used in Examples.

FIG. 7 is a schematic explanatory diagram of suction transfer of a glass preform softened on a floating jig used in an example to a molding die.

FIG. 8 is a schematic explanatory diagram of suction transfer of a glass preform softened on a floating jig used in an example to a molding die.

FIG. 9 is a schematic explanatory diagram of press molding with a molding die used in Examples.

FIG. 10 is a schematic explanatory view of a method of transferring a softened glass preform to a molding die.

FIG. 11 is a schematic explanatory view of a method of transferring a softened glass preform to a molding die.

FIG. 12 is a schematic explanatory diagram of press molding with a molding die used in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ・ ・ ・ Glass preform 2 ・ ・ ・ Glass molded body 10, 17 ・ ・ ・ Floating jig 11 ・ ・ ・ Upper opening of the floating jig 12 ・ ・ ・ Bottom of the upper opening of the floating jig 13, 19・ ・ ・ Floating jig support 14 Glass softening heater 15 ・ ・ ・ Suction holding device 16 ・ ・ ・ Lower opening 18 ・ ・ ・ Porous surface 23 ・ ・ ・ Ring-shaped member 34 ・ ・ ・ Lower mold 35 ・ ・・ Upper mold 36 ・ ・ ・ Guide mold 39 ・ ・ ・ Molds 40, 41 ・ ・ ・ Molding surface 45 ・ ・ ・ Suction port

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Takahara 2-7-5 Nakaochiai Shinjuku-ku, Tokyo Inside Hoya Co., Ltd.

Claims (16)

[Claims] 1. A method for producing a glass optical element by press-molding a preheated and softened glass preform with a preheated molding die, wherein the preform is heated while being floated by an air flow. A method for producing a glass optical element, comprising preheating a reform, transferring a preform softened by preheating to the preheated mold, and then press-molding the preform. 2. The manufacturing method according to claim 1, wherein the floating of the preform by the air flow is performed by the air flow flowing upward from the upper opening. 3. The upper opening has an opening diameter that is less than, equal to, or greater than the diameter of the preform.
The manufacturing method described. 4. The air flow flowing upward from the upper opening,
The manufacturing method according to claim 2 or 3, wherein the gas is supplied from at least one opening at the bottom of the upper opening. 5. The manufacturing method according to claim 1, wherein the floating of the preform by the airflow is performed by an airflow flowing out from a porous surface having a spherical surface or a plane close to the curvature of the preform. 6. The glass preform is preheated by heating the glass preform to a temperature lower than the glass transition point by 30 ° C. or more, and then further heating while floating the glass preform to soften the glass preform. 5. The manufacturing method according to any one of 5 above. 7. The manufacturing method according to claim 1, wherein the preheated and softened preform is transferred to a preheated mold while being suction-held. 8. The manufacturing method according to claim 7, wherein the pre-heated and softened preform is suction-held and transferred to the mold by a suction-holding device having a movable lower opening. 9. A suction holding device having a movable lower opening holds the softened preform by suction and transfers it to the molding surface of the lower mold of the mold, and then the softened preform is transferred to the lower mold. 9. The manufacturing method according to claim 8, wherein press molding is performed by the molding surface of 1 and the molding surface of the upper mold. 10. The production according to claim 1, wherein the preheated and softened preform is suction-held by suction from a suction port provided in the vicinity of the molding surface of the upper die of the molding die. Method. 11. A softened preform sucked and held near the molding surface of the upper mold of the molding die, or a lower mold is moved below the softened preform sucked and held near the molding surface of the upper mold. 11. The reform is moved onto the molding surface of the lower mold, and then press-molded by the molding surface of the upper mold and the molding surface of the lower mold.
The manufacturing method described. 12. The preheated and softened preform is placed on a ring-shaped mounting tool having an inner diameter smaller than the outer diameter of the preform and is transferred to the preheated mold.
7. The production method according to any one of 6. 13. The floating of the preform by the airflow is performed by an airflow that flows upward from an upper opening having an opening diameter smaller than the diameter of the preform, and the upper opening is smaller than the inner diameter of the ring-shaped mounting tool. The manufacturing method according to claim 12, which has an outer diameter. 14. A glass preform softened by heating while being floated by an air flow has a viscosity of 10 ^5.5 to 10 ^9.0.
The manufacturing method according to any one of claims 1 to 13, which is in a range of poise. 15. A method for producing a glass optical element by press-molding a glass gob that is heated and softened while being floated with a preheated mold, wherein the heated and softened glass gob is suction-held. Alternatively, the glass gob is placed on a ring-shaped mounting tool having an inner diameter smaller than the outer diameter, transferred to the preheated mold, and then press-molded, which is a method for manufacturing a glass optical element. 16. The manufacturing method according to claim 15, wherein the glass gob is suction-held by a suction-holding device having a movable lower opening or a suction port provided in the vicinity of the molding surface of the upper die of the molding die.