JP2003073132A - Method and apparatus for forming optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming an optical element with desired thickness without generating roughness of the formed surface or a haze of the optical element. SOLUTION: The method for forming the desired optical element comprises press forming a heated and softened glass material 5 by a forming mold comprising an upper mold 8 and a lower mold 9 oppositely arranged to each other, characterized by comprising a step of heating to soften the glass material 5 at a temperature at which the viscosity becomes in the range of 10<7.8> dPa.s to 10<12> dPa.s, and a step of heating the forming mold before starting forming at a temperature corresponding to the viscosity of the glass material 5 in the range of 10<12> dPa.s to 10<13.5> dPa.s.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method and a molding apparatus for obtaining a desired optical element by pressing a glass material that has been softened by heating with a molding die placed opposite to the glass material.

[0002]

2. Description of the Related Art Heretofore, a molding method described in Japanese Patent Publication No. 4-32007 has been known as a method for molding an optical element of this type.

The method for molding an optical element described in the publication is 1
A method of molding a glass material, which has been heated and softened to a viscosity of 0 ⁶ poises or more and 10 ⁸ poises or less, with a molding die heated to a temperature lower than the glass transition temperature of the glass material to a temperature equivalent to 10 ^14.5 poises or more. Is.

[0004]

However, according to the above-mentioned prior art, when a glass material containing an alkaline component such as Na and K and a readily volatile component such as Pb is to be molded, the glass material is heated to a high temperature. However, there is a problem in that the easily volatile components are volatilized and the surface of the mold is oxidized, the surface of the mold is roughened, and clouding occurs in the molded optical element.

In order to solve the above-mentioned problems, it has been attempted to lower the heating temperature of the glass material to form it in order to suppress the volatilizing action of easily volatile components, but if the temperature is below the glass transition temperature of the glass material. In the molding die heated to a temperature equal to or higher than 10 ^14.5 poise, the temperature of the die is too low,
Since the cooling time of the heated glass material is shortened, an optical element having a desired size of the inner wall cannot be formed.

Especially, it is 0.2 mm like an endoscope lens.
In the case of molding into such a thin wall, there is a problem that the fluidity of the glass material is not obtained and the molding becomes impossible.

The present invention has been made in view of the above circumstances, and an optical element molding method capable of molding an optical element having a desired thickness without causing surface roughness on the molding surface or clouding of the optical element. And a molding apparatus.

[0008]

The invention according to claim 1 is
A glass material that has been softened by heating is pressure-molded by a molding die placed oppositely to obtain a desired optical element. In the method for molding an optical element, the glass material is heated and softened at a temperature within a viscosity range in which an easily volatile component does not volatilize. Before the process and molding start
And a step of heating the mold to a temperature corresponding to the viscosity at which the glass material can be deformed.

According to a second aspect of the present invention, in a method of molding an optical element, a glass material that has been softened by heating is pressure-molded by a molding die that is arranged to ^face the glass material. dPa · s or more 10 ¹² dPa · s
A step of heating and softening at a temperature within the following viscosity range, and a molding die having a glass viscosity of 10% before the start of molding.
Heating to a temperature corresponding to ¹² dPa · s or more and 10 ^13.5 dPa · s or less.

According to the first and second aspects of the invention, in order to suppress the generation of the easily volatile components, the temperature at which the glass material is in a viscosity range where the easily volatile components do not volatilize, that is, 10 ^7.8 d.
A desired optical element, which is softened by heating to a temperature corresponding to a viscosity in the range of Pa · s or more and 10 ¹² dPa · s or less, and heated to a temperature corresponding to a viscosity at which the glass material can be deformed to delay the cooling time of the glass material. The glass viscosity of the glass material was 10 ¹² dPa before the start of molding for the purpose of obtaining the inside meat.
-The mold is heated to a temperature corresponding to s or more and 10 ^13.5 dPa-s or less, and the glass material is pressure-molded by this mold.

As a result, an optical element having a desired thickness can be molded without causing surface roughness on the molding surface or clouding of the optical element.

According to a third aspect of the present invention, there is provided an optical element molding apparatus in which a glass material is pressure-molded by a molding die composed of an upper die and a lower die which are arranged to face each other in a molding chamber to obtain a desired optical element. A heating furnace for heating and softening the glass material to a temperature corresponding to a viscosity range of 10 ^7.8 dPa · s or more and 10 ¹² dPa · s or less, and a molding die including an upper mold and a lower mold before starting the molding The glass viscosity of the material is 10 ¹² d
Pa · s or more 10 ^{13 .} Mold heating means for heating to a temperature corresponding to ⁵ dPa · s or less, the upper mold in the molding chamber,
It is arranged so as to face the lower mold and has an auxiliary heating means for performing heat retention heating of the upper mold and the lower mold during pressure molding of a glass material by a molding mold composed of the upper mold and the lower mold. Is.

According to the third aspect of the present invention, the surface of the molding surface is roughened and the optical element becomes cloudy due to the heating of the glass material by the heating furnace and the heating of the upper and lower molds by the mold heating means. It is possible to mold an optical element of a desired thickness without generating heat, and the upper mold and the lower mold are heated by the auxiliary heating means at the time of pressure molding of the glass material. It is possible to provide an optical element molding apparatus capable of molding an optical element of a desired size without unnecessarily raising the mold temperature even in the case of a fast and small volume glass material.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

(First Embodiment) (Structure) FIG. 1 is a schematic sectional view of an optical element molding apparatus according to the first embodiment of the present invention.

In this optical element molding apparatus, the molding chamber 7
Is a space for maintaining a non-oxidizing atmosphere to prevent the upper mold 8 and the lower mold 9 from being oxidized. A non-oxidizing gas is introduced into the molding chamber 7 by a member not shown.

In the first embodiment, nitrogen gas is used as the non-oxidizing gas. In the first embodiment, the inside of the molding chamber 7 is kept at an oxygen concentration of 15% or less. The oxygen concentration inside the molding chamber 7 can be appropriately selected depending on the mold material and film forming material used for molding. For example, when using a mold in which a WC (tungsten carbide) substrate is coated with a WC film, the oxygen concentration is preferably in the range of 5 ppm to 200 ppm.

In the first embodiment, the upper mold 8 and the lower mold 9 in which the WC substrate is coated with the chromium nitride film are used.

The upper die 8 is a molding die in which WC is mirror-polished and then covered with a chromium nitride film, and has an outer diameter (diameter) of 35 mm, a flange portion 8b on the upper portion and a molding surface on the lower portion. A convex aspherical tip portion 8a is provided.

The upper die retainer 10 is formed of a cylindrical member for holding the upper die 8, is fixed to the upper portion of the molding chamber 7 by a member (not shown), and has a hole through which the rod-shaped portion of the upper die 8 passes. 10 a is provided to hold the flange portion 8 b of the upper die 8 in the upper die retainer 10 and direct the tip 8 a downward of the molding chamber 7.

The upper die heater 11 constituting the die heating means is
A heater for heating the upper die 8, which is arranged in the upper die retainer 10, is in contact with the upper surface of the upper die 8, and is held by the upper die retainer 10 together with the upper die 8.

The lower mold 9 facing the upper mold 8 is a molding mold in which WC is mirror-polished and then covered with a chromium nitride film. The lower die 9 is formed into a rod shape having an outer diameter (diameter) of 35 mm, and has a concave tip portion 9a which is a molding surface having a radius of curvature of 18 mm. The tip portion 9a is attached to the tip 8a of the upper die 8.
It is provided with a base portion 9b. The lower die heater 12 that constitutes the die heating means is for heating the lower die 9, and is fixed and in contact with the lower surface side of the base portion 9b of the lower die 9 by a member (not shown). A pressure shaft 13 is arranged on the lower surface side of the lower die heater 12, and is connected to the lower die heater 12 by a member (not shown).

The pressurizing shaft 13 is vertically driven by a drive mechanism (not shown), and the lower die heater 12 mounted on the pressurizing shaft 13 and the lower die 9 are attached to the pressurizing shaft 13. With this, it is possible to move the lower mold 9 up and down with respect to the upper mold 8 to bring the lower mold 9 into contact with and separate from the upper mold 8.

The glass material 5 has an outer diameter (diameter) of 36 mm.
Is a glass gob having a thickness of 8 mm and a mirror surface. In the first embodiment, the viscosity 10 ¹³ dPa · s is 5
SF11 corresponding to 05 ° C. and having a viscosity of 10 ⁸ dPa · s of 630 ° C. was used.

The transfer tray 2 is a transfer member for accommodating and transferring the glass material 5, and the transfer tray 2 is placed on an arm 3 which is a transfer member.

The arm 3 is driven by a drive mechanism (not shown) so as to move in the left-right direction (directions of arrows a and b) in FIG. 1, and the transfer tray 2 containing the glass material 5 is adjacent to the forming chamber 7. It can be transported to each position outside the heating furnace 1, inside the heating furnace 1, and inside the molding chamber 7.

The heating furnace 1 is a heating means for heating the glass material 5. Between the right end of the heating furnace 1 in FIG. 1 and the molding chamber 7, the heat inside the heating furnace 1 is formed. There is provided a shutter 4 for shutting off so as not to be transmitted to the inside of the furnace and for releasing the space between the heating furnace 1 and the molding chamber 7 at a predetermined timing.

That is, the shutter 4 is pivotally supported by the rotary shaft 6 to rotate to open or close the space between the molding chamber 7 and the heating furnace 1, and when the shutter 4 is open. ,
The arm 3 is provided inside the molding chamber 7 with the glass material 5 and the transfer tray 2.
It is possible to carry in and carry out the glass material 5 after molding. Further, the heating furnace 1 includes a heater 20 for heating the glass material 5.

(Operation) Next, the operation of the first embodiment will be described. After the glass material 5 is placed and accommodated on the transfer tray 2 outside the heating furnace 1, the transfer tray 2 is supported by the arm 3.

Next, the arm 3 is driven in the direction of the arrow a, and the glass material 5 and the transfer dish 2 are loaded into the heating furnace 1.
The heating furnace 1 starts heating the glass material 5. In the first embodiment, in order to suppress the generation of easily volatile components, the glass material 5 is heated to a temperature (63 ° C.) equivalent to 10 ⁸ dPa · s.
Heated to 0 ° C).

Next, the shutter 4 is rotated about the rotary shaft 6 as a support shaft. Immediately after the shutter 4 has rotated to a range where it does not come into contact with the transport tray 2 and the arm 3, the arm 3 is driven in the direction of arrow a, and the glass material 5 and the transport tray 2 are loaded into the molding chamber 7.

The drive of the arm 3 is stopped when the center of the transfer tray 2 and the center of the upper mold 8 and the lower mold 9 come to the same position.

At this time, the upper mold 8 and the lower mold 9 are made of glass of the glass material 5 before the start of molding for the purpose of delaying the cooling time of the glass material 5 in order to obtain the desired inside thickness of the optical element. Viscosity is 10 ¹² dPa · s or more 10 ^13.5 dPa ·
It is preferable to heat to a temperature corresponding to s or less.
In the first embodiment, the viscosity of the glass 5 is 10 ¹² dPa.
Heated to a temperature corresponding to s.

Next, the pressurizing shaft 13 is driven to rise, and the lower die 9 is raised. When the lower mold 9 is raised, the glass material 5 is transferred to the transport tray 2
The upper mold 8 and the lower mold 9 are brought into contact with the glass material 5 and pressure-molded. In the first embodiment, the glass material 5 has a desired thickness of the optical element of 2.5 mm.
Was pressure-molded to have a thickness of.

Next, the molded glass material 5 is heated to 0.6 ° C. /
Cool at a cooling rate of 2 seconds. The viscosity of the glass material 5 is 10
^{After 14} dPa · s or more, the pressure shaft 13 is lowered. At this time, the glass material 5 that has been molded is placed on the lower mold 9 and descends.

When the lower die 9 continues to descend, the glass material 5
Are placed on the transport tray 2. After the tip of the lower mold 9 is further lowered from the lower end of the transport tray 2, the pressing shaft 13 is stopped.

Next, the arm 3 is moved in the direction of the arrow b, and the carrying tray 2 on which the glass material 5 that has been molded is placed is carried out from the heating furnace 1 to the outside in FIG. After that, the glass material 5 is taken out from the transport tray 2 as an optical element which is a molded product, and the molding process is completed.

(Effect) According to the first embodiment, the glass material 5 is heated at a temperature within a viscosity range in which easily volatile components do not volatilize, and the upper mold 8 is heated to a temperature corresponding to a viscosity at which the glass material 5 can be deformed. Since the mold temperature of the lower mold 9 is controlled for molding,
It is possible to obtain an optical element which has no cloudiness on the surface of the obtained optical element and is pressure-molded to a desired inner wall size.

(Second Embodiment) (Configuration) A second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic sectional view of the optical element molding apparatus of the second embodiment.

In this optical element molding apparatus, the molding chamber 7
Is a space for maintaining a non-oxidizing atmosphere to prevent the upper mold 8 and the lower mold 9 from being oxidized. A non-oxidizing gas is introduced into the molding chamber 7 by a member not shown.

In the second embodiment, nitrogen gas is used as the non-oxidizing gas. In the second embodiment, the oxygen concentration inside the molding chamber 7 is maintained at 20 ppm or less.

In the second embodiment, the upper mold 8 and the lower mold 9 in which the WC substrate is coated with the chromium nitride film are used.

The upper mold 8 is formed by polishing the WC to a mirror surface and then
It is a mold covered with a membrane and has an outer diameter (diameter) of 2 mm.
A flange portion 8b is provided on the upper portion, and a tip end portion 8a having a convex aspherical surface which is a molding surface is provided on the lower portion.

The upper die retainer 10 is formed of a cylindrical member for holding the upper die 8, is fixed to the upper portion of the molding chamber 7 by a member (not shown), and has a hole through which the rod-shaped portion of the upper die 8 passes. 10 a is provided to hold the flange portion 8 b of the upper die 8 in the upper die retainer 10 and direct the tip 8 a downward of the molding chamber 7.

The upper die heater 11 is a heater for heating the upper die 8 and is disposed in the upper die retainer 10 and
Is in contact with the upper surface of the upper mold and is held by the upper mold holder 10 together with the upper mold 8.

The lower mold 9 facing the upper mold 8 is a molding mold in which WC is mirror-polished and then covered with a WC film.
The lower die 9 is formed in a rod shape having an outer diameter (diameter) of 2 mm, and has a concave tip portion 9a which is a molding surface having a curvature radius of 0.9 mm.
And the base portion 9b is provided when the tip portion 9a is arranged toward the tip 8a of the upper mold 8.

The lower die heater 12 is for heating the lower die 9, and is fixed and in contact with the lower surface of the base portion 9b of the lower die 9 by a member not shown.

A pressure shaft 13 is provided on the lower surface side of the lower heater 12.
Is arranged and is connected to the lower die heater 12 by a member (not shown).

The pressurizing shaft 13 is vertically driven by a drive mechanism (not shown). The lower die heater 12 mounted on the pressurizing shaft 13 and the lower die 9 are attached to the pressurizing shaft 13. With this, it is possible to move the lower mold 9 up and down with respect to the upper mold 8 to bring the lower mold 9 into contact with and separate from the upper mold 8.

The glass material 5A has an outer diameter (diameter) of 2.2.
The thickness is 0.8 mm and the surface is formed in a cylindrical shape with a mirror surface.

The transfer tray 2 is a transfer member for accommodating and transferring the glass material 5A, and the transfer tray 2 is placed on the arm 3 which is a transfer member. The tip of the arm 3 is formed into a semicircle so as to fit with the outer peripheral portion of the transport tray 2.

The arm 3 moves in the left-right direction (directions of arrows a and b) in FIG. 2, and the transfer tray 2 containing the glass material 5A is placed outside the heating furnace 1 adjacent to the molding chamber 7 and inside the heating furnace 1. It is possible to convey the respective parts inside the molding chamber 7.

In addition to the above-mentioned structure, the optical element molding apparatus according to the second embodiment has an upper die auxiliary heater 1 which is an auxiliary heating means.
4. A lower die auxiliary heater 15 and a push-up ring 16 are provided.

The upper die auxiliary heater 14 is a tip 8a of the upper die 8.
It is a heater for heating the vicinity and is formed in an annular shape. Further, the lower die auxiliary heater 15 is a heater for heating the vicinity of the tip 9a of the lower die 9 and is also formed in a substantially annular shape. The left side portion of the lower die auxiliary heater 15 in FIG. A part of the ring is machined into an open shape so as not to come into contact with the incoming arm 3 and the transport tray 2. The lower die auxiliary heater 15 is attached to a cylinder (not shown) and can move up and down in synchronization with the movement of the lower die 9.

The push-up ring 16 is a cylindrical member for lifting the transfer tray 2 from the arm 3, and is arranged on the base portion 9b of the lower die 9 so as to surround the rod-shaped portion of the lower die 9.

In the second embodiment, the heating furnace 1,
The structure of the shutter 4 is similar to that of the first embodiment,
The same elements as those shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

(Operation) The operation of the second embodiment will be described below. First, the glass material 5A is placed on the transport tray 2 outside the heating furnace 1.

The arm 3 is driven in the direction of the arrow a, and the glass material 5A and the transfer dish 2 are transferred into the heating furnace 1.

Next, the heating furnace 1 starts heating the glass material 5A. In the second embodiment, the glass material 5A is set to 10 ¹² dPa · in order to prevent volatilization of easily volatile components.
Heated to a temperature corresponding to a viscosity of s.

Next, the rotary shaft 6 is rotated to open the shutter 4. After the shutter 4 has rotated to a position where it does not contact the transport tray 2 and the arm 3, the arm 3 is driven in the direction of arrow a,
The glass material 5A and the transport tray 2 are loaded into the molding chamber 7. Then, as shown in the upper column of FIG. 3, the driving of the arm 3 is stopped when the central portion of the transport tray 2 and the central portions of the upper mold 8 and the lower mold 9 come to the same position.

At this time, the upper mold 8 and the lower mold 9 had a viscosity of the glass material 5A of 10 ^{12 in} advance, as in the first embodiment.
It is preferable to heat to a temperature range corresponding to dPa · s or more and 10 ^13.5 dPa · s or less. These upper molds 8,
The lower die 9 is heated by the upper die heater 11 and the upper die auxiliary heater 1.
4, the lower die heater 12 and the lower die auxiliary heater 15 are used. In the second embodiment, the glass material 5A is heated to a temperature corresponding to 10 ^12.5 dPa · s.

Next, the pressing shaft 13 is driven to move up, and the lower die 9 is moved up. The glass material 5A is lifted from the carrying tray 2 by the lower mold 9. After this, the carrier plate 2 is lifted by the arm 3 by the push-up ring 16.

At this time, at the same time, the lower die auxiliary heater 15 rises while maintaining the same distance as the lower die 9 by a cylinder (not shown). The lower die 9 rises as it is, and the glass material 5A is pressed by the upper die 8 and the lower die 9 as shown in the column in FIG.

At this time, the upper mold auxiliary heater 14 and the lower mold auxiliary heater 15 keep the upper mold 8 and the lower mold 9 warm so that the mold temperatures do not decrease. In the second embodiment, the glass material 5A having a small volume of 2.2 mm in diameter and 0.8 mm in thickness is molded, but since the upper die auxiliary heater 14 and the lower die auxiliary heater 15 have a heat retaining effect, Even if the mold temperature is not raised, the extremely small glass material 5A having a small heat capacity and a high cooling rate can be formed. The second embodiment
Is 0.1 m, which is the desired thickness of the optical element.
m could be pressure molded.

Next, the glass material 5A is cooled at a cooling rate of 0.6 ° C./sec. Glass material 5A is 10 ¹⁴ dPa
・ Pressure shaft 13 after reaching the temperature corresponding to viscosity of s or more
Is driven downward to lower the lower mold 9. At this time, the glass lens 5B, which is an optical element for which molding has been completed, is placed on the lower mold 9. The lower die 9 continues to descend, and the push-up ring 16 also descends. As shown in the lower column of FIG. 3, the glass material 5A is placed on the carrying tray 2 and the carrying tray 2 is held on the arm 3.

After the tip of the lower mold 9 is further lowered from the lower end of the transport tray 2, the pressing shaft 13 is stopped.

Next, the arm 3 is moved in the direction of the arrow b, and the transport tray 2 on which the glass material 5A which has been molded is placed.
Is further carried out from the heating furnace 1 to the outside in FIG. After that, the glass material 5A is taken out from the carrying tray 2 as an optical element which is a molded product, and the molding process is completed.

(Effect) According to the second embodiment, since the upper die auxiliary heater 14 and the lower die auxiliary heater 15 prevent the die temperature of the upper die 8 and the lower die 9 from decreasing, a small volume having a high cooling rate is used. Even with the glass material 5A, it is possible to perform pressure molding to a desired inner wall size without unnecessarily increasing the mold mixing degree.

[0069]

According to the present invention, it is possible to provide an optical element molding method capable of molding an optical element that does not cause surface roughness on the molding surface and does not cause clouding on the surface.

Further, according to the present invention, it is possible to mold an optical element which does not cause surface roughness on the molding surface and does not cause clouding on the surface, and at the same time, the optical element made of a glass material of a small volume having a fast cooling rate can be formed. It is possible to provide a molding device for an optical element that can also be molded.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical element molding apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of an optical element molding device according to a second embodiment of the present invention.

FIG. 3 is a process drawing showing the molding method by the optical element molding apparatus according to the second embodiment of the present invention.

[Explanation of symbols]

1 heating furnace 2 Transport tray Three arms 4 shutter 5 glass material 5A glass material 5B glass lens 6 rotation axes 7 molding room 8 Upper mold 8a tip 8b Flange part 9 Lower mold 9a tip 9b base 10 Upper die holder 11 Upper heater 12 Lower heater 13 pressure shaft 14 Upper die auxiliary heater 15 Lower die auxiliary heater 16 Thrust ring 20 heater

Claims (3)

[Claims] 1. A method of molding an optical element, wherein a heat-softened glass material is pressure-molded by a molding die placed oppositely to obtain a desired optical element. In the method of molding an optical element, the glass material is in a viscosity range where an easily volatile component does not volatilize. A method for molding an optical element, comprising: a step of heating and softening at a temperature; and a step of heating a molding die to a temperature corresponding to a viscosity at which a glass material can be deformed before starting molding. 2. A method of molding an optical element, wherein a heat-softened glass material is pressure-molded by a molding die placed oppositely to obtain a desired optical element, wherein the glass material is 10 ^7.8 dPa · s or more 10 ¹² dPa
A step of heating and softening at a temperature within a viscosity range of s or less, and a temperature corresponding to a glass viscosity of the glass material of 10 ¹² dPa · s or more and 10 ^13.5 dPa · s or less before starting the molding. A method of molding an optical element, comprising: a step of heating. 3. A glass material, forming chamber oppositely disposed upper mold, pressurizing and pressure molded by the mold comprising a lower mold, the molding apparatus of an optical element to obtain a desired optical element, the glass material 10 ⁷ More than ⁸ dPa · s 10 ¹² d
A heating furnace that heats and softens to a temperature corresponding to a viscosity range of Pa · s or less, and a molding die including an upper mold and a lower mold before the molding is started has a glass viscosity of 10 ¹² dPa · s or more 10
A mold heating means for heating to a temperature corresponding to ^13.5 dPa · s or less, and a glass material formed by a molding mold including the upper mold and the lower mold arranged facing the upper mold and the lower mold in the molding chamber. A molding device for an optical element, comprising: an auxiliary heating unit that performs heat retention heating of the upper mold and the lower mold during pressure molding.