JP3188676B2 - Method for manufacturing glass molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass molded body including a glass optical element such as a high-precision lens which does not require grinding or polishing after press molding. In particular, the present invention provides a method for producing a glass molded body having higher surface accuracy with high production efficiency.

[0002]

2. Description of the Related Art There is a method of molding glass optical elements such as lenses using a molding die in which softened glass is not fused and a mirror-finished mold material is precisely processed, and which does not require grinding or polishing after press molding. Various types have been developed. In such a method for forming a glass optical element, there is a problem of further improving productivity. That is, a method and an apparatus for forming more glass optical elements in a unit time with a single apparatus are required.

Conventional methods for molding glass optical elements include, for example, US Pat. No. 3,833,347 and US Pat.
No. 81,023. The method described in U.S. Pat.No. 3,833,347 involves setting a glass lump in a mold, raising the temperature in a non-oxidizing atmosphere, isothermally pressing the mold and the glass at a temperature near the softening point of the glass, and pressing to maintain the load. This is a method in which the temperature of the mold is lowered to a temperature lower than the glass transition temperature, the load is removed, and the temperature is further cooled to 300 ° C. or less to prevent oxidation of the mold. Further, the method described in U.S. Patent No. 4,481,023 uses a glass preform shape approximate to the final product, the preform and the mold and the isothermal conditions at a temperature at which the glass viscosity is in the range of 10 ⁸ to 10 ¹² poises Then, the molded lens is removed from the mold at a temperature showing a viscosity of between 10 ^{11 and} 10 ¹³ poise. Each of these methods is called an isothermal pressing method, and a lens having high surface accuracy can be obtained, but has a drawback that a molding cycle time (a time required for molding one lens) is extremely long.

On the other hand, Japanese Patent Application Laid-Open No. 7-10556 discloses the following optical element molding method. In a method of heating and softening a glass material, pressing it with a molding die, and molding an optical element, the heated glass material is heated to a viscosity of 10 ⁷ to 10 ⁹ dPaS (Poise), and 10 ¹⁰
~ 10 ¹² dPaS (Poise) Pressed with a mold adjusted to a temperature corresponding to the viscosity of Poise, then the temperature of the mold was 10 ¹³ dPaS
After cooling to a temperature below the temperature corresponding to the viscosity of (Poise), the press pressure is released. This method is a method using a molding die having a temperature lower than the temperature of the glass material (non-isothermal pressing method), and since the heating temperature of the molding die can be kept low, the cycle time of molding is reduced as compared with the above method. It can be shortened.

[0005]

The length of the molding cycle time mainly depends on the time required for raising and lowering the temperature of the molding die. In general, the temperature at which the lens is released from the mold and the cooling rate greatly affect the surface accuracy of the obtained lens, and therefore, depending on the shape and size of the lens, the release and cooling rate at a high temperature are generally reduced. It is problematic to make the value more than a certain value. Therefore, in order to shorten the molding cycle time, it is necessary to shorten the temperature rise of the molding die.
In order to shorten the temperature rise of the molding die, it is necessary to set the temperature to be raised low and to speed up the temperature rise rate and the operation related to the temperature rise.

However, in the method described in Japanese Patent Application Laid-Open No. 7-10556, attention is paid only to setting the temperature to be raised low, and no consideration is given to the temperature rising speed and the speeding up of the operation related to the temperature rising. Not done. Japanese Patent Application Laid-Open No. 7-10556 attaches a drawing in which a heater is attached to an upper and lower mold, but does not describe the type of the heater, the temperature required for raising the temperature, and the like. Generally, a resistance heater is used for raising and lowering the temperature of a molding die. However, it is hard to say that raising and lowering the temperature of the mold by the resistance heater is rapid.

By the way, there is a high-frequency induction heating as a method of increasing the temperature rising rate faster than the resistance heating, and US Pat. No. 3,833,347 discloses an example in which the high-frequency induction heating is employed as a method of forming an optical member.
And JP-A-63-10556. In these methods, the molding die is heated by an induction heating coil disposed outside the molding apparatus via a heat-resistant glass tube. In this apparatus, the heating of the mold itself is performed quickly, but it takes time to carry the glass material into and out of the mold in the glass tube, and as a result, the cycle time cannot be reduced. As described above, in order to shorten the cycle time, it is necessary to speed up not only the heating rate but also the operation related to the heating,
In the methods known so far, there is no method that takes into account the speeding up of the operation related to the temperature rise. In addition, in the case of the above-described mechanism, the distance between the upper mold and the lower mold must be separated by several tens of cm or more.In this case, the upper and lower molds to which the preheated glass material is supplied approach and are pressed until the glass is pressed. As the material travels longer, the temperature of the glass material decreases,
This leads to deterioration of surface accuracy after pressing. The problem is more severe the smaller the glass material.

Accordingly, an object of the present invention is to provide a method for molding a glass molded body having excellent surface accuracy which is not different from that of a conventional product in a shorter cycle time.

[0009]

The present invention that achieves the above object is as follows. [Claim 1] A step (A) of pressing a preheated glass material with a preheated upper mold and lower mold to form a glass molded body corresponding to each molding surface of the upper mold and the lower mold, and forming the formed glass. Cooling the molded body (B), separating the cooled glass molded body by separating the upper mold and the lower mold (C), and preheating the glass material, the upper mold and the lower mold (D ) Is repeated to produce a glass molded body, at least one of the upper mold and the lower mold is movable, the upper mold and the lower mold are preheated by induction heating in a state of being separated from each other, separated A manufacturing method, characterized in that after supplying a preheated glass material to a lower mold preheated in a state, one of an upper mold and a lower mold moves to perform a pressurizing step (A). [Claim 2] When the temperatures near the molding surfaces of the upper mold and the lower mold are cooled to or below the transition temperature of the glass constituting the glass molded body, the cooled glass molded body is released. The production method according to 1. [Claim 3] The production method according to claim 1 or 2, wherein the upper die or the lower die moved for performing the pressing step is subjected to induction heating during the pressing step. [4] The production method according to any one of [1] to [3], wherein the steps (A) to (D) are performed in a non-oxidizing atmosphere. The [Claim 5] The glass material preheated to the corresponding temperature to a viscosity of 10 ⁹ poise, and transferred onto the molding surface of the lower mold preheated to below the preheating temperature of the glass material, of the preceding claims to pressurize The production method according to any one of the preceding claims. [Claim 6] The lower mold is movable up and down, the moving distance between the preheating position and the pressing position of the lower mold is 30 cm or less, and within 5 seconds after the preheated glass material is supplied. The production method according to any one of claims 1 to 5, wherein pressure molding is started. [7] The production method according to any one of [1] to [6], wherein the induction heating is performed by a high-frequency induction heating coil. [8] The method according to any one of [1] to [7], wherein the induction heating of the upper mold and the lower mold are independently performed. [Claim 9] The method according to claim 7, wherein the upper mold and the lower mold are induction-heated by one high-frequency induction heating coil. [Claim 10] The manufacturing method according to claim 9, wherein the temperature of the upper mold and / or the lower mold is adjusted by changing the positions of the high-frequency induction heating coil and the upper mold and / or the lower mold. [Claim 11] A servo motor drive is used as a vertical drive device for performing one of the upper die and the lower die to perform the pressing step (A).
The production method according to the paragraph. [12] The production method according to any one of [1] to [11], wherein the glass molded body is a microlens having a diameter of 8 mm or less. [Claim 13] The glass molded body is an optical element that does not require grinding and polishing after press molding.
3. The production method according to any one of 2.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The production method of the present invention comprises the following steps.
This is a method for producing a glass molded body by repeatedly performing a cycle consisting of (A) to (D). Step (A): A step of pressing a preheated glass material with a preheated upper mold and lower mold to form a glass molded body corresponding to each molding surface of the upper mold and the lower mold. Step (B): Formed Step of cooling the glass molded body Step (C): a step of separating the cooled glass molded body by separating the upper mold and the lower mold Step (D): a step of preheating the glass material, the upper mold and the lower mold By repeating the cycle consisting of steps (A) to (D),
The method for producing a glass molded body is already known, and also in the present invention, the glass material to be used, molding dies such as an upper mold and a lower mold, molding conditions, etc. Can be used as is. Further, it is preferable to perform the steps (A) to (D) in a non-oxidizing atmosphere from the viewpoint of preventing oxidation of the mold and preventing fusion of the glass material to the mold.

[0011] In the method for producing a glass molded article according to the present invention, at least one of the upper mold and the lower mold is movable, and the upper mold and the lower mold are preheated by induction heating in a state where they are separated from each other. After supplying the preheated glass material to the lower mold preheated in step (1), one of the upper mold and the lower mold moves to perform the pressurizing step (A). The upper mold and the lower mold are preheated when the upper mold and the lower mold are preheated by induction heating, and when the members around the upper mold and the lower mold, for example, the mother mold are induction heated, and the heat causes the upper mold to be heated. And the case where the lower mold is preheated. This will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a molding die used in a method for molding a glass molded article of the present invention. The apparatus for forming a glass formed body includes a transfer mechanism including a forming die 10 and a vertical driving device selected from a cylinder, a servomotor drive, a piston, and the like for moving the lower portion 14 of the forming die in a vertical direction as described later. And a high-frequency coil for inductively heating a predetermined member in the molding die 10, and the molding die 10 is mounted in a molding device. Mold 10
Has a molding die upper part 12 which is substantially cylindrical and fixed at a predetermined position, and a molding die lower part 14 which can be moved in the vertical direction by the vertical driving device (not shown).
The upper mold part 12 has a substantially disc-shaped first upper mold 16 and a second cylindrical upper mold 18 located below the upper mold 16 and fixed to the upper mold 16. An upper mold 20 which is located concentrically with the second upper mold 18 and presses and forms a glass material at the lower end face thereof, and which is concentric with the second upper mold 18 and the upper mold 20 and has a radius. In the direction, the upper die lowering stop ring 22 which is the holding means of the upper die positioned between them, and the upper die lowering stop ring
And a spring 25 disposed vertically between the upper die stopper ring 22 and the sleeve 24. Here, as a vertical drive device,
When the servo motor drive is used, since both position control and torque control can be performed, vertical position control and torque control can be performed, so that position control and position speed control on the order of microns can be performed.

On the other hand, the lower mold part 14 has a lower mother mold 26 and a lower mother mold 2 fixed at its lower surface to a cylinder (not shown).
6, a hollow cylindrical second lower mold 28 fixed to the lower mold 26, and concentric with the lower mold 28;
Further, a lower mold 30 adapted to receive a glass material on a molding surface which is an upper end surface thereof is provided.

The upper mold 20 and the lower mold 30 of such a mold 10 can be formed of a material which is induction-heated. Further, the members around the upper mold 20 and the lower mold 30 or the upper molds 16 and 18 and the lower molds 26 and 28 may be formed of a material which is induction-heated. Further, all of the upper mold 20, the lower mold 30, the sleeve 24, the upper mold 18 and the lower mold 28 may be formed of a material which is induction-heated. The material to be induction-heated can be, for example, a metal material such as a tungsten alloy or a cemented carbide.

When the upper mold 20 and the lower mold 30 are formed of a material to be induction-heated, the molding surface is formed of, for example, ceramics such as diamond, heat-resistant metal, noble metal alloy, carbide, nitride, boride, oxide and the like. Etc.
It is preferable from the viewpoint that high durability can be obtained. In particular,
A silicon carbide film is formed on a substrate made of a material to be induction-heated by a CVD method and processed into a finished shape, and then an amorphous and / or crystalline material such as an i-carbon film is formed by an ion plating method or the like. It is preferable to form a carbon film composed of a single component layer or a mixed layer of high quality graphite and / or diamond. Even if these carbon films are molded at a relatively high mold temperature, there is an advantage that fusion does not occur and the mold can be easily released at a relatively high temperature because of good releasability.

When the upper mold 20 and the lower mold 30 are formed of a material other than the material to be induction-heated, for example, cermet of silicon carbide, silicon, silicon nitride, tungsten carbide, aluminum oxide or titanium carbide, or cermet of these materials is used. May be formed by coating the surface of the substrate with a ceramic such as diamond, heat-resistant metal, noble metal alloy, carbide, nitride, boride and oxide. In particular, after a silicon carbide film is formed on a silicon carbide sintered body by a CVD method and processed into a finished shape, amorphous and / or crystalline graphite such as an i-carbon film is formed by an ion plating method or the like. Preferably, a carbon film formed of a single component layer or a mixed layer of diamond is formed. The reason is,
This is because even if the molding is performed at a relatively high mold temperature, fusion does not occur, and the mold can be easily released at a relatively high temperature because of good releasability.

The upper mother dies 16, 18 and the lower mother dies 26, 28
Can be made of a material to be induction heated, for example, metal. The spring 25 can be made of, for example, a ceramic material. At the center in the radial direction of the upper mold 16, a cylindrical protrusion 32 protruding downward is provided, so that the lower end surface of the protrusion 32 and the upper end surface of the upper mold 20 can abut. . Also, the upper mold 16 and the second upper mold 1
8 are mutually fixed by screws or the like.

The hollow cylindrical second upper mold 18 accommodates an upper mold 20, an upper mold lowering stop ring 22 and a sleeve 24 inside thereof, and has an inner peripheral surface formed by: The sleeve 24 comes into contact with the outer peripheral surface of the sleeve and guides the sleeve 24. Further, the lower surface of the second upper mother die 18 comes into contact with the upper surface of the second lower mother die 28 when the glass material is pressed (at the time of molding). A projecting portion 19 projecting radially inward is formed on the lower inner peripheral surface of the second upper mold 18. This guides the sleeve 24 and limits the downward movement of the sleeve 24. A flange 34 is formed on the upper side of the upper die 20. Further, the shape of the lower end surface of the upper mold 20 matches one surface shape of the glass molded body.

The upper die stopper ring 22 has an upper flange 36 projecting radially outward and a lower flange 38 projecting radially inward. Upper flange 36
One is in contact with the upper mold 16, and the other is in contact with one end of the spring 25. For this reason, the ring 22 is urged upward by the spring 25, that is, toward the upper matrix 16.
The lower flange 38 can be engaged with the flange 34 of the upper mold 20, thereby preventing the lowering of the upper mold 20.

The sleeve 24 is integrally formed, and for convenience, the upper sleeve upper side 40 and the lower sleeve 4
The description will be made separately from the above. The upper sleeve 40 is provided with a projection 44 projecting outward in the radial direction, and the upper surface of the projection is in contact with the other end of the spring 25. As a result, the sleeve 24 is urged downward. The upper sleeve 4
0 and the outer peripheral surface of the upper mold 20 are in contact with each other.
The sleeve 40 can slide up and down while being guided by the inner peripheral surface of the sleeve 40. The inner diameter of the upper sleeve 40 is smaller than the inner diameter of the lower sleeve 42. A step 46 is formed at the boundary between the lower sleeve 42 and the upper sleeve 40. The function of the step 46 will be described later. Further, the lower sleeve 42 is fitted into a donut-shaped hole between the lower mold 30 and the second mother mold 28, which will be described later.
, And is guided by the outer peripheral surface of the lower mold 30. The spring 25 is wound between the second upper matrix 18 and the sleeve 24, one end of which is in contact with the upper mold lowering restriction ring 22, and the other end of which is a protrusion 44 of the sleeve 24.
Is in contact with

Similarly to the upper mother dies 16 and 18, the lower mother dies 26 and the second lower mother dies 28 are fixed to each other by screws. Further, the lower mold 30 is placed on the lower mold 26 and is positioned by a protrusion 48 projecting radially inward of the second lower mold 28. The upper end surface of the lower mold 30 is
The molding surface conforms to the other surface shape of the glass molding.

At least one of the upper mold 20 and the lower mold 30 is movable. For example, the lower mold 30 can move together with the lower mold 14 that can be raised by the vertical drive device (not shown). The preheating by induction heating in this state where the upper mold and the lower mold are separated from each other will be described with reference to FIG. As shown in FIG.
The upper mold 20 in 2 is preheated by the high frequency heating coil 60. The lower mold 30 in the lower mold part 14 is preheated by the high-frequency heating coil 61 with the lower mold part 14 lowered. Thereby, preheating can be performed in a state where the upper mold 20 and the lower mold 30 are separated from each other. The high-frequency heating coils 60 and 61 can be operated under the same conditions or individually different conditions, and the temperatures of the upper mold 20 and the lower mold 30 can be set to the same or different temperatures.

Next, as shown in (b), the glass material heated to a predetermined temperature is conveyed to above the lower mold 30 by the jig 50 for holding the glass material, and Dropped and transported. In this embodiment, the heating and softening of the glass material can be performed while floating the glass material on a jig 50 by an air current, and the heated and softened glass material is subjected to predetermined heating by, for example, induction heating using a high-frequency heating coil. Is transferred to the mold 10 which has been preheated to the temperature. Here, the jig 50 has, for example, a left-right symmetrically shaped opening from which gas is blown out from below, so that the glass material floats on the opening with an airflow formed by blowing out the gas. A drop jig that can be arranged and that can drop the glass material by dividing the jig horizontally from the center can be used. Therefore, the glass material can be dropped and transferred onto the lower mold by dividing the drop jig horizontally above the lower mold.

At this time, when the lower mold is dropped and supplied, the preform is dropped and supplied to the lower mold by interposing a drop position adjusting member between the drop jig and the lower mold. Can be. By interposing the drop position adjusting member in this way, it is possible to prevent the preform from jumping out of the molding die and from being supplied to a position deviated from the center of the lower molding die. The drop position adjustment member is
It may be one having a guide portion which forms a falling passage for the glass material to be formed and allows the glass material to be dropped substantially vertically. Further, the drop position adjusting member may have a means for moving the guide portion. The falling passage of the glass material to be molded preferably has an inner diameter slightly larger than the diameter of the glass material to be molded. A passage whose inner diameter decreases downward and whose minimum inner diameter is slightly larger than the diameter of the glass material to be formed is more preferable. The shape of the falling position adjusting member is not limited as long as it has a passage for the glass material to be molded and a guide portion that can regulate the falling position of the glass material to be molded in the horizontal direction. The guide portion may be, for example, a thick plate body provided with a through hole. The through-hole preferably has a funnel shape that at least partially narrows downward. Further, the guide portion may be a substantially cylindrical member. Further, the guide portion may be a funnel-shaped member that at least partially narrows downward. Further, the guide portion may be formed by projecting three or more leg members on the ring. Preferably, each leg member is inclined toward the center of the ring from the base to the tip. The material of the drop position adjusting member is not particularly limited as long as it is a heat-resistant material. For example, it may be a metal, ceramic, or carbon material. The falling path of the glass material to be molded of the guide means may be subjected to surface processing in order to allow the glass material to be molded to slide. In order to guide the glass material to be molded more smoothly and to prevent the glass material to be molded from being scratched, it is preferable that the corners present in each of the above shapes are curved.

Further, the distance between the lower mold and the drop jig, and the distance between the lower mold and the drop position adjusting member and the drop jig are used to prevent the displacement of the drop position of the preform and to prevent the temperature drop during the drop of the preform. From the viewpoint, a smaller one is preferable. Therefore, by using the servo motor drive as the vertical drive device, the lower mold does not contact or collide with the drop jig or the drop position adjusting member, and
It is easy to move to a position that does not leave much space with the drop jig or the drop position adjusting member. Preferably, from the viewpoint of reducing the mold life of the the molding time, 10 ⁹ poises glass material preheated to the corresponding temperature on the viscosity below, on the molding surface of the lower mold preheated to below the preheating temperature of the glass material And pressurized. Further, from the viewpoint of shortening the cycle time, preferably, the lower mold can be moved up and down, the moving distance between the preheating position and the pressing position of the lower mold is 30 cm or less, and the preheated glass material is used. Suitably, pressure molding is started within 5 seconds after the supply.

It is preferable that the smaller the preform becomes, such as when the glass molded article is a microlens, the shorter the moving distance and the pressing start time are. Therefore, the moving distance may be 20 cm or less, or 10 cm, if necessary.
It is also possible to: Also, the pressurization start time is 3
It can be within seconds. As described above, the high-frequency induction heating coil may have the upper mold heating coil and the lower mold heating coil separately, but it is preferable to heat the upper mold and the lower mold with one coil. By doing so, there is no fear that both will interfere with each other when a current flows through the upper and lower heating coils. Here, even when heating the upper mold and the lower mold with one coil, the heating temperature of the upper mold and the lower mold can be changed. For example, by using the fact that the heating temperature of the mold can be lowered by shifting the position of the mold from the position of the coil, the upper mold and / or the lower mold can be moved up and down by moving the position of the mold vertically. The upper mold and / or the lower mold can be heated to a desired temperature. Alternatively, by controlling the balance between the currents flowing through the coil wound around the upper mold and the coil wound around the lower mold, the upper mold and / or the lower mold can be heated to the respective desired temperatures. it can.

Next, after supplying the preheated glass material to the lower mold 30, the jig 50 moves, and one of the upper mold 20 and the lower mold 30 moves to perform the pressing step (A). In the case of FIG. 2, as shown in FIG.
4 together with the upper part 12 of the mold,
The pressurizing step (A) is performed. The positional relationship between the high-frequency heating coils 60 and 61 and the upper mold 20 and the lower mold 30 can be other than that shown in FIG. For example, as shown in (1) of FIG. 3, the high-frequency heating coil 60 for preheating the upper mold 20 is arranged so as to be able to heat the lower mold 30 that has moved upward. In the above, the structure can be such that the mold can be heated if necessary. Also,
As shown in FIG. 3 (2), the high-frequency heating coil for preheating the upper mold 20 is composed of 60a and 60b.
b, the temperature of the lower mold 30 which has been moved upward by the high-frequency heating coil 60b can be controlled separately, not only in the preheating but also in the pressing step if necessary.
The structure may be such that heating can be performed under different conditions. Using a high-frequency heating coil as shown in FIG. 3, induction heating of the upper mold and / or the lower mold moved to perform the pressing step during the pressing step can be performed by changing the shape and size of the molded object. In some cases, it is preferable to maintain the mold at a predetermined temperature in order to obtain a desired surface accuracy. In addition, during the cooling step, the upper mold and / or the lower mold can be induction-heated to obtain a desired surface accuracy, and the cooling rate can be controlled.

Incidentally, in the state of FIG.
The upper mold 20 is located at the lowest position along the sleeve 24 due to its own weight and the lower flange of the upper mold stopper ring 22. Further, the sleeve 24 is located at the lowermost position by the urging force of the spring 25 and the engagement between the protrusion 44 and the protrusion formed at the lower part of the upper mother die 18. When the upper mold 12 and the lower mold 14 in which each member is in such a position engage with each other, first, the lower sleeve 42 of the sleeve 24 forms the lower mold 42 with the lower mold 30 and the second mother mold 28. 4 (c) and 4 (c).
(C)). Next, the lower mold 14 is further pushed upward by the vertical drive device, thereby forming the upper mold 2.
The glass material is compressed by the contact of the lower end surface of the glass material with the glass material (see FIG. 4D). At this time, the lower part 14 of the molding die is, for example, about 30 to 3
The glass material is pressed with a pressure of 00 kg / cm ² . Also,
The upper mold 20 moves slightly upward and contacts the lower end surface of the upper mold 16.

When the lower portion 14 of the mold 10 is further raised by the piston, the lower end surface of the upper sleeve 40 of the sleeve 24 comes into contact with the upper end surface of the second lower mold 28 (FIG. 4E). This causes the sleeve 24 to move upward against the spring 25. As shown in FIG. 4 (f), when the lower end surface of the second upper mother die 18 and the upper end surface of the second lower mother die 28 come into contact with each other, the glass material is pushed and cut off. In this position, the glass molding (lens)
Is determined.

In the state shown in FIG. 4F, the outer diameter of the compressed glass material is slightly larger than the outer diameter of the lower end surface (forming surface) of the upper mold 20. Meanwhile, the sleeve 24
The lower sleeve 42 has a larger inner diameter than the upper sleeve 40. Therefore, the upper mold 20 and the lower sleeve 42 are
They are separated by a predetermined distance. Therefore, the outer peripheral portion of the glass material does not contact the lower sleeve 42.

Note that the state shown in FIG.
Until the state shown in (f), the inner peripheral surface of the lower sleeve 42 of the sleeve 24 is substantially in contact with the outer peripheral surface of the lower mold 30, so that the sleeve 24 is guided, and The upper die 20 is guided by the outer peripheral surface substantially contacting the inner peripheral surface of the upper sleeve 40 of the sleeve 24. For this reason, axial displacement between the upper mold 20 and the lower mold 30 is prevented, and these are appropriately positioned with respect to each other.

Next, in the state shown in FIG. 4 (f), the formed glass material (lens) is cooled at a cooling rate of, for example, 30 to 150 ° C./min until the temperature becomes equal to or lower than the glass transition point. Here, the upper mother dies 16 and 18 correspond to the lower mother dies 26 and 2
The position of the upper mold 20 is determined by 8, but the upper mold 20 is in a free state, and its own weight is applied to the lens. Therefore, the upper mold 20 follows the contraction of the lens due to cooling, and the weight of the upper mold (for example, 0.002 to 0.1 kg / cm ² ) is applied to the lens during cooling. That is, during cooling, contact between the upper surface of the lens and the lower end surface (molding surface) of the upper mold is maintained. This makes it possible to obtain good surface accuracy on the lens after release.

When the lens is cooled to a predetermined temperature (for example, the transition point of glass to the transition point of −50 ° C.), the lower mold part 14 of the mold 10 is lowered to release the lens. At the time when the temperature near the molding surface of the upper mold and the lower mold is cooled to or below the transition temperature of the glass constituting the glass molded body, it is possible to release the cooled glass molded body,
It is preferable from the viewpoint of obtaining good surface accuracy. In the present embodiment, since the lens to be molded has a meniscus shape, the lens is released from the lower mold 30 when the lower mold part 14 is slightly lowered as shown in FIG. On the other hand, it is easy to stick to the upper mold 20.

In the present embodiment, the lower mold part 14
Is lowered, the sleeve 24 of the upper mold 12 is moved downward by the biasing force of the spring 25.
As described above, the step portion 46 is formed at the boundary between the upper sleeve 40 and the lower sleeve 42 of the sleeve 24. Therefore, when the sleeve 24 descends, the step 46 and the upper end of the molded lens come into contact with each other, and the lens stuck to the upper mold 20 is pushed downward. When the molding die lowering part 14 descends, the upper die 20 also descends slightly, but its lowering is stopped by the lower flange 38 of the upper die lowering stop ring 27. Therefore, the lens is released from the upper mold 20 and falls on the lower mold 30 (FIG. 2 (h)).
reference).

After the lens is released from the mold in this way, the lower mold part 14 is lowered to a predetermined position, and the lens on the lower mold 30 is taken out using a suction pad (not shown). The removed lens may be annealed as needed. According to the present embodiment, after the initial pressurization is completed and the upper part of the mold and the lower part of the mold come into contact with each other, the weight of the upper mold is applied to the glass. Following the glass, the contact between the upper surface of the lens and the lower end surface (molding surface) of the upper mold is maintained. Therefore, it is possible to obtain good surface accuracy on the lens after release.

In a low-viscosity region where the glass material is deformed by its own weight, it is very difficult to prevent fusion of the glass with a jig holding the glass material during heating. Thus, the jig 50 shown in FIG. 2B forms a gas layer on both the jig surface and the glass surface by ejecting gas from the inside of the jig to float the glass material by an air current. As a result, it is preferable that the jig and the glass can be heated and softened without reacting. Further, when the glass material is a preform, it can be softened by heating while maintaining the shape of the preform. In addition, even if the glass material is a glass gob and has an irregular shape with surface defects such as wrinkles, it is possible to adjust the shape and eliminate surface defects by floating by airflow while heating and softening. is there.

The above-mentioned floating of the glass material and transfer of the glass material heated and softened to the preheated mold are performed, for example, by:
It is disclosed in JP-A-8-133758. The heating of the glass material includes a case of heating from room temperature to a predetermined temperature, a case of further heating using a glass material of a certain temperature, and a case of using a glass material already heated to a predetermined temperature. For example, when the glass material is a glass gob, a glass gob made of molten glass can be used without cooling.

[0038] In the method of the present invention, there is provided a molding apparatus in which a plurality of upper dies and / or lower dies are arranged on the upper mold and / or the lower mold, and an induction heating coil is arranged around the matrix. It can also be used. By using such an apparatus, it is possible to produce a plurality of glass molded articles by a single press molding. In this case, it is preferable that the upper matrix and / or the lower matrix have a long shape having a certain width, and a plurality of molds are arranged on the matrix in a line in a longitudinal direction, and the center of the molds is aligned with the center of the mold. It is preferable to provide it so as to be located on the center line of the matrix. In addition, it is preferable that at least the distance between the coil and the matrix at the lateral end of the matrix is constant. That is, a preferred molding apparatus is, specifically, a molding die composed of an upper die and a lower die, a mother die supporting the molding die, and a heater for heating the molding die wound around the mother die. A molding device having a heating means, wherein the matrix has a long shape, and has a certain width, and a plurality of the molding dies are formed on the matrix in a line at equal intervals in a longitudinal direction. An apparatus in which the center of the mold is provided so as to be located on the center line of the mold, and at least the distance between the heating means and the mold at the short-side end of the mold is constant. By using this device,
It is possible to simultaneously press-mold a plurality of heat-softened glass materials to be molded simultaneously with a plurality of molds composed of an upper mold and a lower mold, which are arranged in a row in a longitudinal shape in a matrix along a longitudinal direction. Further, each of the plurality of molds is heated by heat conduction from the mold heated by the heating means wound around the matrix, and this heating is performed at least for each mold. This is done so that two opposing positions in the horizontal section are heated substantially evenly. As a result, it is possible to minimize the occurrence of a temperature distribution on the molding surface of each mold due to a difference in distance from the heating means, and it is possible to simultaneously mold a plurality of glass optical elements having good surface accuracy and surface quality. It is preferable that both ends of the long matrix are preferably substantially semicircular from the viewpoint that the heating to the mold near the both ends can be uniform. By using the above-mentioned apparatus, each mold can be uniformly heated and press-molded, so that a glass molded product having high surface accuracy and good surface quality without causing problems such as partial spread failure. Can be manufactured. The floating softening jig and the drop position adjusting member used at this time also preferably have a plurality of openings for quick drop supply.

The apparatus in which the plurality of upper dies and / or lower dies are arranged will be further described with reference to FIG. FIG. 5 is a cross-sectional view showing an assembled state of an upper mold, a lower mold, and a mother die of a press molding apparatus. In the molding apparatus shown in FIG. The upper mold 2 and the lower mold 3 are used. The upper mold 2 and the lower mold 3 are made of, for example, a cemented carbide, and may have a molding surface coated with a noble metal alloy thin film. The matrix 1 can be made of, for example, a tungsten alloy and has a coefficient of thermal expansion slightly larger than that of a cemented carbide. Reference numeral 5 denotes a tray for transferring the matrix 1 having the upper mold 2 and the lower mold 3 into the press molding chamber. Numeral 6 is a spacer provided on the lower surface of the lower mold in order to adjust the thickness according to the dimensions of each mold so that the thickness of the molded product is constant in each mold. As shown in FIG. 6, the press forming apparatus further includes an upper main shaft 9 and a lower main shaft 8 for pressing an upper die and a lower die, and an induction heating coil 7 for performing induction heating during molding. Have. The induction heating coil 7 is wound in a shape surrounding a long matrix.

A molding method using this press molding apparatus will be described. The spherical preform 4 is set between the upper mold 2 and the lower mold 3 in the matrix 1, and the matrix 1 is placed on the tray 5 and placed in a molding device kept in an inert atmosphere. It is arranged together with the tray 5 on the lower main shaft 8 of the molding device. Thereafter, the lower main shaft 8 is raised, and the lower die 3 is raised inside the induction heating coil 7 of the forming apparatus (FIGS. 6a and 6b). A high-frequency power is applied, the matrix 1 is induction-heated, and the glass material to be molded is heated. Then, the lower main shaft is further raised, and the upper surface of the upper die is pressed against the head 9 of the upper main shaft, thereby softening the preform. Is pressed (FIG. 6c). Then, after cooling to below the glass transition point, the lower main shaft is lowered, and the molded article is taken out of the molding apparatus together with the molding die, whereby a plurality of glass molded articles can be manufactured at once.

[0041]

The present invention will be described in more detail with reference to the following examples. Embodiment 1 In this embodiment, as shown in FIG. 2, the upper mold 12 is preheated by the upper high frequency coil 60, and the lower mold 14 is preheated by the lower high frequency coil 61. And from the 18mm gap between the upper and lower high frequency coils,
Insert the floating plate 50 with the softened preform,
The floating plate 50 was opened left and right, the preform was dropped, the lower mold was raised, and press molding was performed. In this example, the floating plate was set to open and retracted, so that the time from the fall to the start of the press was 0.5 seconds. Since the temperature of the preform was low during this period, the temperature of the mold was set to 556 ° C. (a temperature corresponding to a glass viscosity of ^109.8 poise), so that the temperature was sufficiently increased. Further, when the preform is dropped and supplied, a drop position adjusting member is inserted between the floating plate and the lower mold, and the preform is dropped and supplied to the lower mold with the interposition thereof. Can be. By interposing the drop position adjusting member in this way, it is possible to prevent the preform from jumping out of the molding die and from being supplied to a position deviated from the center of the lower molding die. In this case, the gap between the upper and lower high-frequency coils is such that the drop position adjusting means can be inserted, for example, about 10 mm.
Extra spacing can be provided. Next, the suction pad was inserted into the gap between the upper and lower coils, and the glass molded body was taken out. Recovery time was also reduced, resulting in an overall cycle time of 53 seconds. The lens obtained in this way had good surface accuracy and could be continuously produced in a very short cycle time. In the present embodiment, press molding is performed with the high-frequency power turned off, but the pressing may be performed while applying the high-frequency power. The time required for each step of this example is shown below.

(1) As shown in FIG. 2, a split type floating plate in which the preform is floated and softened is brought directly above the lower mold (1 sec). (2) Open the split-type floating pan to the left and right, and drop the softened preform onto the lower mold (1 sec). At this time, the temperature of the preform is 647 ° C. and the viscosity is 10 ^5.5 poise. (3) Withdraw the split mold floating pan from the lower mold while keeping it open
(1 sec). (4) The lower mold immediately rises, and press-molding with the upper mold is started (in some cases, the temperature is maintained at a constant temperature for a predetermined time, or in the case, it is immediately cooled) (0.5 sec). (5) The mold is cooled to a temperature lower than the glass transition point (in this embodiment, a temperature lower by 10 ° C. than the glass transition temperature). (It may be cooled by applying power) (31sec). (6) The mold is released, the lower mold is lowered, and the glass molded body is taken out with a suction pad (not shown) (1.5 sec). (7) The upper mold is subjected to high-frequency induction heating to 561 ° C (glass viscosity of 10 ° C). Preheat to a temperature corresponding to ^9.5 poise). (Recover) (18 sec) Press molding is repeated in steps (1) to (7). The time required for each step is also shown.

The time from (1) to (3) is about 3 seconds,
The time until the start of the press in (4) was about 0.5 seconds. The temperature drop of the lower mold for 3.5 seconds was about 5 ° C., and there was no problem in molding. Move the lower mold upward and / or
Alternatively, the temperature of the lower molding die can be raised by 5 ° C. in advance in anticipation of a temperature drop by slightly moving the lower molding die and the high-frequency coil so as to preheat them by slightly shifting their positions.

Example 2 In this example, as shown in FIG. 3 (1), the lower molding die was preheated by a lower high-frequency coil, and was heated by an upper high-frequency coil during pressing. The preheating temperature of the mold is 596 ° C (corresponding to a glass viscosity of 10 ⁸ poise) and the temperature of the softening preform is also 596 ° C.
(Temperature corresponding to a glass viscosity of 10 ⁸ poises), pressed at a constant temperature for 10 seconds while applying high frequency power, and then cooled. Others are basically the same as the first embodiment.

Embodiment 3 This embodiment is similar to Embodiment 2, except that the upper high-frequency coil is divided into two circuits, and pressing and cooling are performed while controlling the upper and lower temperatures separately (FIG. 3 (2)). The upper mold is slightly cooler than the lower mold (about 10
C) is effective to prevent sticking to the upper mold during release. Although the first to third embodiments have been described using a lens having an outer diameter of 15 mm as an example, an optimum method may be selected according to the size and shape of the lens.

In the mold structure shown in FIG. 1, in the cooling step after the upper and lower molds collide with each other by pressing, the upper weight of the upper mold is applied to the glass molded body. By slightly changing the mold structure, the second pressing can be performed with the middle push bar from above the upper mold after the upper and lower molds have collided. Further, in order to prevent sticking to the upper mold when the mold is released at or below the transition point, the sleeve is pressed down near the outer periphery of the glass molded body by the action of a spring and is released from the upper mold.

[0047]

According to the present invention, while maintaining productivity,
It is possible to provide a molding method and a molding apparatus for a glass molded body having better surface accuracy. That is, in the present invention, the rate of temperature rise and fall is increased by employing high-frequency heating. Resistance heating and infrared lamp heater heating generally have good heat retention, so that the rate of temperature decrease is slow, whereas high-frequency induction heating can increase the rate of temperature decrease. Furthermore, in the method of the present invention, the high-frequency coil is not provided outside the heat-resistant glass tube, but is provided around the outer periphery of the forming die in the apparatus. It is possible to make the distance very close, with only an interval for inserting the product take-out pad, so that the vertical moving distance of the lower mold can be shortened. Whereas a conventional heat-resistant glass tube method would result in a device of several hundred mm, the method of the present invention can reduce it to 100 mm or less or 50 mm or less. According to the method of the present invention, press molding can be performed with a very fast operation and in a short cycle time, thereby greatly improving the production efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a molding die used in the method for producing a glass molded body of the present invention.

FIG. 2 is a view showing the operation of a molding die used in the method for producing a glass molded body of the present invention.

FIG. 3 is a view showing the operation of a molding die used in the method for producing a glass molded body of the present invention.

FIG. 4 is a schematic sectional view of a molding die used in the method for producing a glass molded body of the present invention.

FIG. 5 is a sectional view showing an assembled state of a press molding apparatus used in the method for producing a glass molded body of the present invention.

FIG. 6 is an explanatory view of a forming method using the press forming apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mold 12 Mold upper part 14 Mold lower part 16, 18 Upper mother die 2, 20 Upper die 22 Upper die lowering stop ring 24 Sleeve 25 Spring 26, 28 Lower mother die 3, 30 Lower die

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 11/00 C03B 11/12

Claims (12)

(57) [Claims] 1. A step (A) of pressing a preheated glass material with a preheated upper mold and a lower mold to form a glass molded body corresponding to each molding surface of the upper mold and the lower mold. Step (B) of cooling the molded body, moving at least one of the upper mold and the lower mold to separate the upper mold and the lower mold, and cooling the glass molded body from between the separated upper mold and the lower mold. Releasing step (C), and the glass material, the upper mold and the lower mold ,
The glass material will be at a higher temperature than the upper and lower molds
A method of producing a glass shaped material by repeating the steps (D) to urchin preheating, the preheating of the upper and lower molds in the step (D) is the upper and lower molds in step (C) is separated from each other In the state , said separated
Induction heating coils that wind around the upper and lower molds respectively
The glass material, which is preheated separately from the upper mold and the lower mold in the step (D), is placed in the gap between the induction heating coils in the preheated lower mold in the separated state in the step (C). And a pressurizing step (A) is performed by moving one of the upper mold and the lower mold after the supply. 2. The method according to claim 1, wherein the upper die or the lower die moved for performing the pressing step is subjected to induction heating during the pressing step. 3. The method according to claim 1, wherein steps (A) to (D) are performed in a non-oxidizing atmosphere. 4. The production method according to claim 1, wherein the preheating of the upper mold and the lower mold in the step (D) is performed at a temperature lower than the preheating temperature of the glass material. 5. The method according to claim 1, wherein the glass material preheated to a temperature corresponding to a viscosity of 10 ⁹ poise or less is transferred onto a molding surface of a lower mold preheated to a temperature lower than the preheating temperature of the glass material and pressurized. The production method according to any one of the preceding claims. 6. The method according to claim 1, wherein the pressure molding is started within 5 seconds after the preheated glass material is supplied. 7. The method according to claim 1, wherein one of the lower mold and the upper mold is movable up and down, and a moving distance between a movable preheating position and a pressurizing position of the lower mold or the upper mold is 30 cm or less.
7. The production method according to any one of items 6 to 6. 8. The production method according to claim 1, wherein the induction heating of the upper die and the lower die is performed independently. 9. The method according to claim 1, wherein the induction heating is performed by a high-frequency induction heating coil, and the temperature of the upper mold and / or the lower mold is adjusted by changing the positions of the high-frequency induction heating coil and the upper mold and / or the lower mold. The production method according to any one of Items 1 to 8. 10. An up-down driving device for performing one of the pressurizing step (A) by moving one of the upper mold and the lower mold,
10. The method according to claim 1, wherein a servo motor drive is used.
The production method according to the paragraph. 11. The production method according to claim 1, wherein the glass molded body is a microlens having a diameter of 8 mm or less. 12. The glass element is an optical element that does not require grinding and polishing after press molding.
The production method according to any one of claims 1 to 7.