JP2001328829A - Apparatus and method for molding optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for molding an optical element, excellent in profile irregularity by properly controlling the temperature of a molding surface and the time of the molding, and slow and uniform cooling of the whole molded glass material. SOLUTION: This apparatus for molding the optical element for obtaining the optical element by conveying a glass material to the space between a pair of forming molds heated to a temperature lower than the temperature of the glass material, and molding the glass material by the pair of the forming molds has an infrared lamp heater 4a for heating the upper mold, capable of heating the forming mold, an infrared lamp heater 4b for heating the lower forming mold, and a heating controller 30, a switch 31, a temperature regulator 32 and a heating output regulator 33 consisting a heating temperature-controlling means for controlling the temperature distribution of the molding surfaces of the pair of the forming molds so as to be the prescribed temperature distribution to compensate the largeness and smallness of heat capacity distribution based on the shape of the optical element to be molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a molding apparatus and a molding method for an optical element.

[0002]

2. Description of the Related Art Generally, a glass material used for molding an optical element has a difference in thickness between a central portion and an outer peripheral portion. If the glass material is pressed at a temperature lower than that of the glass material, at a temperature near the glass transition point, and the molding surface is heated evenly, the thin part of the glass material solidifies quickly and the thick part hardens later. In addition, the amount of shrinkage of the thick part increases, causing internal strain and large undulation on the surface, making it impossible to obtain an optical element with good surface accuracy. For example, in the case of an optical element having a convex shape, a thin outer peripheral portion is first cooled to a temperature lower than the glass transition point, and a central portion is delayed to be lower than the glass transition point. Can not get.

[0003] As a conventional technique for solving this problem, there is a method for molding an optical element disclosed in Japanese Patent Application Laid-Open No. 02-133325.

The method of molding an optical element disclosed in Japanese Patent Application Laid-Open No. H02-133325 discloses a method of forming a glass material such that a thin portion that is easy to cool has a high temperature, a thick portion that is difficult to cool has a low temperature, and a temperature distribution in a concentric direction. This is a molding method for an optical element in which the glass material is heated and pressed on a molding surface heated to a uniform temperature, and the curing time of the entire glass material is made uniform.

[0005]

However, Japanese Patent Application Laid-Open No.
In the molding method disclosed in JP-A-133325, it is difficult to control the heating temperature of the glass material, and the temperature variation is large. Therefore, the reproducibility of the molding conditions is poor, the yield is reduced, and an optical element of stable quality cannot be obtained.

Further, there is a problem that a high temperature portion of the glass material causes a large heat shock when coming into contact with the molding die, causing cracks and seizures and deteriorating the durability of the die.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to appropriately control the temperature of a molding surface after molding and to make the cooling rate of the entire molded glass material slow and uniform. Accordingly, the present invention provides an optical element molding apparatus and a molding method capable of obtaining an optical element with good surface accuracy.

[0008]

According to a first aspect of the present invention, there is provided a molding apparatus for an optical element, wherein a heat-softened glass material is conveyed between a pair of molding dies heated to a lower temperature than the glass material by a conveying device. In an optical element forming apparatus for forming an optical element by forming the glass material with a pair of forming dies, a heating unit for heating the pair of forming dies, and a heating power is sent to the heating unit to form the pair of forming dies. Heating temperature control means for controlling the surface to a constant temperature distribution and controlling the temperature distribution of the molding surface during molding of the glass material so as to have a temperature distribution that complements the magnitude of the heat capacity distribution based on the shape of the optical element to be molded. And characterized in that:

According to a second aspect of the present invention, an optical element is obtained by conveying a heat-softened glass material between a pair of opposite molds heated to a temperature lower than that of the glass material and pressing the glass material to obtain an optical element. In the method, a heating power is sent to a heating means for heating the pair of molding dies, and the molding surfaces of the pair of molding dies are controlled to have a constant temperature distribution, and the temperature distribution of the molding surfaces is molded when the glass material is molded. The optical element is formed by controlling the temperature distribution so as to complement the magnitude of the heat capacity distribution based on the shape of the optical element.

According to a third aspect of the present invention, an optical element is obtained by transporting a heat-softened glass material between a pair of opposite molds heated to a temperature lower than that of the glass material by a mold heater and pressing. In the method of molding an optical element, a step of heating the glass material to a uniform temperature and heating a molding surface of the molding die in a state of providing a temperature distribution in a concentric direction, and transporting the glass material between the molding dies. And, during the molding of the glass material by the mold, by supplying a large amount of heat to the easily cooled portion of the glass material and supplying a fixed amount of heat to other portions, the cooling rate of the entire surface of the glass material is reduced. Controlling so that it is small and even, pressing and holding until the temperature of the glass material is below the glass transition point, cooling the formed glass material, and releasing a pair of molds It is characterized in that including the that step.

Hereinafter, a molding method according to a second aspect of the present invention will be described using the configuration of the molding apparatus according to the first aspect.

The glass material is heated in advance in a heating furnace so that the temperature of the glass material becomes uniform. Thereafter, the glass material is conveyed by the conveying means between the pair of molds heated to a lower temperature than the glass material using the heating means.

The temperature of the molding die is controlled so that the molding surface has a constant temperature distribution. During molding, the temperature distribution of the molding surface is molded by a heating temperature control means in accordance with the shape of the optical element. The temperature distribution is controlled so as to complement the magnitude of the heat capacity distribution based on the shape of the optical element.

For example, when molding an optical element having a small ratio between a thick portion and a thin portion and a small amount of deformation, a constant temperature distribution is maintained as it is, the ratio between the thick portion and the thin portion is large, and the deformation amount is small. In the case of a large optical element, it is rapidly heated immediately before molding to form a molding surface with a temperature distribution that complements the magnitude of the heat capacity distribution of the optical element.

That is, after the molding surface of the mold contacts the glass material, the heating power for the heating means is rapidly increased,
A large amount of heat is applied to the molding surface of the mold that corresponds to the portion of the glass material that is easy to cool, that is, the portion with a high cooling rate, and the molding surface of the mold that corresponds to the portion of the glass material that is difficult to cool, that is, the portion that has a low cooling speed An amount of heat is supplied, and the cooling rate is controlled so that the entire glass material has a uniform cooling rate.

In this way, since the entire glass material is uniformly cooled, it is possible to eliminate the occurrence of internal strain and surface undulation. Further, by reducing the cooling rate of the entire glass material, the deformation time is increased, and even an optical element having a large deformation amount can be formed with high surface accuracy.

According to the molding method of the third aspect, similarly to the case of the molding method of the second aspect, after the molding surface of the mold contacts the glass material, a portion of the glass material that is easy to cool, In other words, a large amount of heat is supplied to the molding surface of the molding die corresponding to the portion having a large cooling rate, and a fixed amount of heat is also supplied to the molding surface of the molding die corresponding to the portion of the glass material that is difficult to cool, that is, the portion having a small cooling speed. The cooling rate is controlled so that the entire glass material has a uniform cooling rate.

In this way, since the entire glass material is uniformly cooled, it is possible to eliminate the occurrence of internal strain and surface undulation. Further, by reducing the cooling rate of the entire glass material, the deformation time is increased, and even an optical element having a large deformation amount can be formed with high surface accuracy.

[0019]

Embodiments of the present invention will be described below.

(Embodiment 1) (Configuration) FIGS. 1 and 2 are schematic views of a molding apparatus used in a method for molding an optical element according to Embodiment 1 of the present invention.

In this molding apparatus, the concave molding surface 1
The upper die 1a having the letter c is mounted on the pedestal 2a using the positioning member 3a.

Further, a lower mold 1 having a concave molding surface 1d is provided.
b is attached to the pedestal 2b so as to be able to move up and down by using a positioning member 3b, facing the upper die 1a.

The lower die 1b is provided with a cylindrical spacer 9 which can be brought into contact with the transport tray 7 and pushed up.

An upper heater housing 5a is arranged on the outer periphery of the upper die 1a, and an infrared lamp heater 4a for heating the upper die is mounted in the upper heater housing 5a. A lower heater housing 5b is arranged around the outer periphery of the lower die 1b, and a lower die heating infrared lamp heater 4b composed of an infrared lamp heater is attached to the lower heater housing 5b.

The upper mold heating infrared lamp heater 4a and the lower mold heating infrared lamp heater 4b are provided with a temperature controller 32 (glass material) controlled by a heating control device 30 constituting a heating temperature control means shown in FIG. The temperature of each mold is adjusted to the set temperature during the molding process, and the heating output controller 33 (additionally and forcibly heats the mold temperature to each mold temperature during the molding of the glass material). The upper mold 1a and the lower mold 1 are controlled by the heater 32 and the heating output controller 33.
b is heated from the respective side surfaces to form a molding surface 1c and a molding surface 1d
Is configured to be adjustable.

The heating power (electric power) for the upper die heating infrared lamp heater 4a and the lower die heating infrared lamp heater 4b can be rapidly increased by the heating output controller 33.

One of the temperature controller 32 and the heating output controller 33 is selectively operated by a switching unit 31 controlled by a heating controller 30.

The glass material 6 is a convex lens that has been ground, polished, and centered in advance, and is supplied to the transfer plate 7.

The transfer tray 7 can be placed on a transfer arm 8.
The transfer arm 8 can carry in and out the transfer tray 7 and the glass material 6 between the upper mold 1a and the lower mold 1b by a driving means (not shown).

In the first embodiment, SK11 (glass transition point; 541 ° C.) was used as the glass material 6. The upper die 1a and the lower die 1b are made of WC (tungsten carbide).
Was used.

(Operation) Next, with reference to FIGS. 3, 4 and 5, a method of manufacturing an optical element by the molding apparatus according to the first embodiment of the present invention will be described.

The upper mold 1a and the lower mold 1b shown in FIGS.
Heated from the side by the temperature controller 32, the outer periphery is 800 ° C., the molding surface 1c, and 540 ° C. near the glass transition point at the outer periphery of the molding surface 1d, the molding surface 1c, and
It is heated to a temperature of 525 ° C. near the center of the molding surface 1d.

The glass material 6 is placed on a transfer tray 7 and heated to a temperature near the glass softening point (glass softening point +2 degrees or +3 degrees) by a heating device (not shown).
Is carried between the upper mold 1a and the lower mold 1b.

Thereafter, as shown in FIG. 2, the lower die 1b is raised by a driving device (not shown) to press-mold the glass material 6. In the first embodiment, the pressing time is set to 15 seconds.

At this time, the molding surface 1c and the molding surface 1d
Comes into contact with the glass material 6 and at the same time, the switching device 31
Causes the heating output controller 33 to operate instead of the temperature controller 32, thereby rapidly increasing the heating output (electric power) of the upper die heating infrared lamp heater 4a and the lower die heating infrared lamp heater 4b for a certain period of time. .

In the first embodiment, the heating output is increased from about 0.6 KW at the time of temperature adjustment of each mold before molding to about 1.2 KW for 10 seconds.

The amount and time of the increase in the heating output can be variously adjusted according to the amount of deformation of the glass material 6 to be formed.

Here, the lower mold 1b will be described as a representative example. Due to the increase in the output of the lower mold heating infrared lamp heater 4b, a temperature distribution occurs in the lower mold 1b inside and outside the mold. That is, as shown in FIG. 4, the outer peripheral portion is the high-temperature portion 11 and the vicinity of the center of the molding surface is the low-temperature portion 10 of 573 ° C. The lower mold 1 shown in FIG.
Each of the arc-shaped solid lines L in the vicinity of the center of the molding surface in b represents a temperature distribution in increments of 10 degrees, and the density of the solid lines L becomes deeper toward the outer periphery and cannot be displayed as a distribution.

According to this temperature distribution, as shown in FIG.
The amount of heat 13 sent to the molding surface 1d is large at the outer peripheral portion of the lower mold 1b and becomes smaller toward the central portion. The upper die 1
In the case of a, the temperature distribution is similar to that of the lower mold 1b.

On the other hand, when the glass material 6 is pressed, the lower mold 1b
The amount of heat 12 that moves to the outside is large at the outer periphery and smaller at the center due to heat radiation from the outer periphery of the mold.

Thereafter, a cooling step is performed. Here, as described above, a large amount of heat is applied to the molding surface 1d of the lower mold 1b at the outer peripheral portion which is easy to be cooled (a heat amount such that the temperature near the center of the molding surface becomes 573 ° C.). ) Is given, and the same applies to the case of the upper mold 1a.
As a whole, it becomes substantially uniform, and a portion (the outer peripheral portion that is easy to cool) does not solidify first.

FIG. 6 shows a temporal change in temperature of the molding die composed of the upper mold 1a and the lower mold 1b and a temporal change in temperature of the glass material 6 during molding and cooling of the glass material 6 of the first embodiment. Shown in As can be understood from FIG.
When the glass material 6 is pressed by a and 1b, the glass material 6 is deformed and the temperature of the glass material 6 becomes lower and higher.
b, the temperature is rapidly increased for a certain period of time so as to provide a temperature distribution near the center of the molding surface of each mold and the outer peripheral portion within the deformation time.
The cooling rate at the central portion and the outer peripheral portion is substantially equal, and this cooling speed is lower than the cooling speed of the glass material 6 at the initial stage of deformation.

When the temperature of the glass material 6 becomes lower than the glass transition point, the lower mold 1b is lowered with respect to the upper mold 1a to release the mold.

(Effect) According to the molding method using the molding apparatus shown in the first embodiment, when the glass material 6 is cooled, the cooling rate is reduced by the above-described heating treatment of the entire glass material 6, As the deformation time becomes longer, desired molding can be performed even when the amount of deformation of the glass material 6 is large. In addition, since the entire glass material 6 is uniformly cooled and the cooling rate is slowed, the deformation time is prolonged, so that sinks and residual internal stress due to uneven cooling portions can be removed. It is possible to mold an optical element with high accuracy.

(Embodiment 2) (Structure) FIG. 7 is a schematic view showing the structure of a molding apparatus according to Embodiment 2 of the present invention.

In the second embodiment, the first embodiment
Is characterized in that a high-frequency heating method using eddy current is employed instead of the upper mold heating infrared lamp heater 4a and the lower mold heating infrared lamp heater 4b shown in FIG.
That is, as shown in FIG. 7, a high-frequency coil 14a is provided on the outer periphery of the upper mold 1a, and a high-frequency coil 14b is provided on the outer periphery of the lower mold 1b.
Are attached and connected to a high-frequency heating power supply (not shown). The other configuration is the same as that of the first embodiment, and the detailed description is omitted.

(Effect) In the forming method using the forming apparatus shown in the second embodiment, similarly to the first embodiment, a glass material 6 heated to a temperature near the glass softening point by a heating device (not shown) is subjected to a high frequency wave. The upper mold 1a and the lower mold 1b heated to a temperature equal to or lower than the glass transition point by the coils 14a and 14b are pressed by the upper mold 1a and the lower mold 1b, and when the glass material 6 comes into contact with the molding surface 1c and the molding surface 1d, the high frequency heating is started. Increase output, mold 1
a and a large amount of heat is supplied to the side surface of the mold 1b with good heat transfer efficiency. Other operations are the same as those in the first embodiment.

(Effects) According to the molding method of the second embodiment, the high frequency coils 14a and 14b are employed, and the amount of increase in the output and the increase time thereof, and the frequency of the high frequency are changed, so that the glass material 6 is formed. Therefore, heat transfer can be efficiently performed in various patterns, the shape and range of the glass material 6 that can be formed can be expanded, and various optical elements can be obtained.

(Embodiment 3) (Configuration) FIG. 8 is a schematic view showing the configuration of a molding apparatus according to Embodiment 3 of the present invention.

In the third embodiment, the second embodiment
In place of the high-frequency coils 14a and 14b for heating the molding die shown in FIG. 7, an upper-type heating high-frequency coil 16a and a lower-type heating high-frequency coil 16b are replaced with an upper die 15a and a lower die 15 respectively.
b, and the molding surfaces 15c and 15d of the upper die 15a and the lower die 15b are each formed in a convex shape.

That is, the upper die 15a having the convex molding surface 15c is provided with a coil insertion hole 23a therein, and is mounted using a positioning member 3a on a pedestal 24a having a through hole 22a formed in the center. ing.

The lower mold 15b having the convex molding surface 15d has a coil insertion hole 23b formed therein.
Using a positioning member 3b, it is mounted on a pedestal 24b having a through hole 22b at the center thereof so as to be able to move up and down, facing the upper die 15a.

The upper mold heating high-frequency coil 16a is inserted into the coil insertion hole 23a through the through hole 22a. The lower mold heating high-frequency coil 16b is inserted into the coil insertion hole 23b through the through hole 22b.

The upper mold heating high-frequency coil 16a and the lower mold heating high-frequency coil 16b are connected to a high-frequency heating power supply (not shown) to heat the upper mold 15a and the lower mold 15b from inside. I have to. The other configuration is the same as that of the second embodiment, and the detailed description is omitted.

(Operation) In the molding method using the molding apparatus of the third embodiment, the molding surface 15c and the molding surface 1
5d contacts the glass material 17 and, at the same time, the output to the upper die heating high-frequency coil 16a and the lower die heating high-frequency coil 16b is rapidly increased by the high-frequency heating power supply for a certain period of time.

In this case, the output increase amount and the increase time are adjusted by the deformation amount of the glass material 17 to be formed. Here, in the case of the lower mold 15b, the high-frequency coil 16 for lower mold heating is used.
Due to the increase in the output of b, as shown in FIG. 9, a temperature distribution occurs in which the outside (outer peripheral portion) becomes the low temperature portion 18 and the inside (the center portion side) becomes the high temperature portion 19.

Due to the temperature distribution, as shown in FIG.
The amount of heat (indicated by an arrow) 21 is large at the center and becomes smaller toward the outer periphery. The same applies to the case of the upper mold 15a.

On the other hand, the lower mold 1
The amount of heat (indicated by an arrow) 20 moving to 5b is large at the center and small at the outer periphery.

Here, on the molding surface 15d of the lower mold 15b,
Since a large amount of heat is applied to the central portion, the cooling rate of the glass material 17 becomes substantially uniform as a whole of the glass material 17, and a portion does not solidify first.

Further, the cooling rate of the entire glass material 17 is reduced, and the deformation time is increased.
Molding becomes possible even when the deformation amount of 7 is large. After a certain period of time, the upper mold heating high-frequency coil 16a, and
The output of the lower mold heating high-frequency coil 16b is output to the molding surface 15c,
After returning to the temperature control state of 15d, the upper mold 15a, the lower mold 15b, and the glass material 17 are cooled by a quenching device (not shown).
Is rapidly cooled, and when the temperature of the glass material 17 becomes lower than the glass transition point, the lower mold 15b is lowered to release the mold.

(Effect) According to the molding method using the molding apparatus shown in the third embodiment, the entire glass material 17 having a concave surface during molding is uniformly cooled, and the cooling rate is reduced. Since the deformation time is long, sink marks and residual internal stress due to uneven cooling portions can be removed, and a desired optical element with good surface accuracy can be obtained.

[0062]

According to the present invention, by appropriately controlling the heating of the mold using the heating means, and making the cooling rate of the entire molded optical element uniform and slow, an optical element having good surface accuracy can be obtained. A molding device capable of obtaining an element can be provided.

Further, according to the present invention, the entire glass material being formed is uniformly cooled, and the cooling rate is slow and the deformation time is long. It is possible to provide a molding method capable of removing a residue and obtaining a desired optical element with high surface accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a molding device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view at the time of a molding step by the molding apparatus according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a heating temperature control system of the molding apparatus according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a temperature distribution of a lower die according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a state of heat transfer between the lower mold and the glass material according to the first embodiment of the present invention.

FIG. 6 is a graph showing temperature changes of a molding die and a glass material according to the first embodiment of the present invention.

FIG. 7 is a schematic sectional view showing a molding device according to a second embodiment of the present invention.

FIG. 8 is a schematic sectional view showing a molding device according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a temperature distribution of a lower die according to Embodiment 3 of the present invention.

FIG. 10 is an explanatory diagram showing a state of heat transfer between a lower mold and a glass material according to Embodiment 3 of the present invention.

[Explanation of symbols]

 1a Upper die 1b Lower die 1c Molding surface 1d Molding surface 2a Pedestal 2b Pedestal 3a Positioning member 3b Positioning member 4a Upper die heating infrared lamp heater 4b Upper die heating infrared lamp heater 5a Upper die heater housing 5b Lower heater housing 6 Glass Material 7 Transfer tray 8 Transfer arm 9 Spacer 30 Heating control device 31 Switching device 32 Temperature controller 33 Heating output controller

Claims (3)

[Claims] An optical element for conveying a glass material which has been heated and softened to a pair of molds heated to a temperature lower than that of the glass material by a conveying device, and molding the glass material with the pair of molds to obtain an optical element. A heating means for heating the pair of molding dies, a heating power is supplied to the heating means to control the molding surfaces of the pair of molding dies to a constant temperature distribution, and the molding surface is formed at the time of molding the glass material. A heating temperature control means for controlling the temperature distribution to be a temperature distribution that complements the magnitude of the heat capacity distribution based on the shape of the optical element to be molded. 2. A method for forming an optical element, wherein a glass material which has been heated and softened is conveyed between a pair of molding dies heated to a temperature lower than that of the glass material and pressed to obtain an optical element. A heating power is sent to heating means for heating the molding die, and the molding surfaces of the pair of molding dies are controlled to have a constant temperature distribution, and at the time of molding the glass material, the temperature distribution of the molding surface is adjusted to the shape of the optical element to be molded. A method for molding an optical element, characterized in that an optical element is molded by controlling the temperature distribution so as to complement the magnitude of a heat capacity distribution based on the optical element. 3. A method for molding an optical element, wherein a glass material which has been heated and softened is conveyed between a pair of opposite molds heated to a lower temperature than the glass material by a mold heater and pressed to obtain an optical element. Heating the glass material to a uniform temperature and heating the molding surface of the mold to a state in which a temperature distribution is provided in a concentric direction; and transporting the glass material between the molds; At the time of molding the glass material by the mold, by supplying a large amount of heat to the easily cooled portion of the glass material and supplying a fixed amount of heat to the other portions, the cooling rate of the entire surface of the glass material is small and uniform. Controlling and pressing and holding the glass material until the temperature of the glass material becomes equal to or lower than the glass transition point; and cooling the formed glass material and releasing the pair of molds. Method of molding an optical element characterized and.