JPH09188529A - Device for forming optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element-forming device having a top force, a top force-holding barrel die for supporting the top force, a bottom force, and a bottom force-holding barrel die for supporting the bottom force, enabling to easily detach the forces from the force-holding barrel dies, respectively, even when molding processes are repeated many times. SOLUTION: This device 10 for forming optical elements is used for pressing a thermally softened optical element material 4 with a mold comprising a top force 22 and a bottom force 26. Therein, the forming device 10 is further provided with a top force-holding barrel die (20) for supporting the top force and a bottom force-holding barrel die (24) for supporting the bottom force, and satisfies relations: α1 >α2 and α1 '>α2 ' wherein α1 and α2 are the linear expansion coefficients of materials constituting the top and bottom forces, respectively, and α1 ' and α2 ' are the linear expansion coefficients of materials constituting the top and bottom force-holding barrel dies, respectively.

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 apparatus for obtaining an optical element by pressing an optical element material softened by heating and then cooling the material.

[0002]

2. Description of the Related Art Conventionally, in a molding apparatus for molding an optical element by pressing an optical element material softened by heating with a molding die consisting of an upper die and a lower die, the upper die is supported. A mold holding cylinder mold and a lower mold holding cylinder mold for supporting the lower mold are provided, and one of the upper mold holding cylinder mold and the lower mold holding cylinder mold is moved toward and away from the other to open and close the molding mold. Molding devices are known.

In the conventional molding apparatus of this type, the constituent material of the molding die and the constituent material of the pressing barrel mold are made of the same material or materials having substantially the same linear expansion coefficient. According to this configuration, during molding (when heated) and at room temperature (when not heated), there is a gap between the mold and the pressing cylinder (that is, between the upper mold and the upper pressing cylinder, and between the lower mold and the lower mold). If the clearance between the die and the press die does not change and the processing precision of the die and the die is good, there was no fear of eccentricity (center misalignment) of the molded product.

Generally, if the clearance between the molding die and the pressing barrel die during molding is small, the processing accuracy of the molded product is improved. However, in this conventional molding apparatus, when the molding die is fitted to the pressing body die with a minute clearance of, for example, about several microns, in order to improve the processing accuracy of the molded product, both of them are repeatedly formed during repeated molding. May be seized, and as a result, the forming die may not be able to be removed from the holding die. If it is attempted to forcibly remove the forming die from the body die in this state, both may be damaged. If the clearance between the two is set large in order to prevent the occurrence of this problem, there is a problem that the processing accuracy of the molded product is deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is an upper die, an upper die holding cylinder die for supporting the upper die, a lower die and a lower die holding cylinder for supporting the lower die. An object of the present invention is to provide an optical element molding apparatus having a mold, which can easily take out the molding die from the barrel mold even if the molding is repeated many times.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a molding apparatus for molding an optical element by pressing an optical element material softened by heating with a molding die composed of an upper die and a lower die. And a lower die holding body die for supporting the lower die, which is provided as a separate member from the upper die holding body die, and has linear expansion coefficients α of the respective constituent materials of the upper die and the lower die. ₁ , α ₁ ′, and the linear expansion coefficients of the constituent materials of the upper die holding cylinder die and the lower die holding cylinder die are α ₂ and α ₂ ′, respectively,
_The feature is that the relationship of ₁ > α ₂ and α ₁ '> α ₂ ' is established.

The present invention also relates to a molding apparatus for molding an optical element by pressing an optical element material softened by heating with a molding die consisting of an upper die and a lower die. An upper die holding cylinder die having an insertion supporting hole; and a lower die holding barrel die having a lower die insertion supporting hole for inserting and supporting the lower die, the lower die holding barrel die being a member different from the upper die holding barrel die,
The upper die and the upper die holding cylinder die, and the lower die and the lower die holding body die, respectively, are the clearance between the upper die and the upper die insertion support hole when not heated, and the lower die and the lower die insertion support hole. The non-heating clearances between the two are made of different materials each having a linear expansion coefficient larger than the two clearances during the heating molding.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on illustrated embodiments. A molding apparatus 10 to which the present invention is applied includes a fixed lower mold base 12 fixed to a main body of the molding device 10 and a movable upper mold support member 14 which is vertically driven so as to be able to come into contact with and separate from the fixed lower mold base 12. have. A quartz tube 16 is provided around the fixed lower mold base 12 and the movable upper mold support member 14. The quartz tube 16 is movable in the vertical direction, and a heater 18 is fixed around the quartz tube 16.

An upper die pressing body die 20 is fixed to the movable upper die support member 14 via bolts or the like (not shown) so as to be detachable. The upper die 22 is supported by the movable upper die support member 14 via the upper die pressing body die 20. On the other hand, to the fixed lower mold base 12, a lower mold holding body mold 24 is detachably fixed via bolts or the like (not shown). Lower mold 2
6 is a fixed lower mold base 1 through the lower mold holding body mold 24.
Supported by 2. Lower surface of lower mold 26 and fixed lower mold base 1
A mold height adjusting spacer 28 having a predetermined thickness is provided between the upper surface of the mold 2 and the upper surface of the mold 2. The mold height adjusting spacer 28 is for adjusting the thickness dimension of the molded product. The temperature of the upper mold 22 heated by the heater 18 is measured by a thermocouple 29 in which the temperature sensor portion is located in the upper mold holding drum 20, and the temperature of the lower mold 26 heated by the heater 18 is lower. The temperature is measured by a thermocouple 30 in which the temperature sensor part is located in the mold holding drum mold 24.

On the side surface of the upper die holding cylinder die 20, there are four locations at approximately 90 ° intervals, which are parallel to the vertical direction (vertical direction in FIGS. 1 and 2), that is, the contact direction between the upper die 22 and the lower die 26. A reference plane (reference plane) 32 extending in the direction is formed (see FIG. 4). On the other hand, on the side surface of the lower die holding body die 24, the upper die holding body die 2
In correspondence with the reference plane 32 formed on the side surface of 0, approximately 9
Reference planes (reference planes) 34 extending in the vertical direction are formed at four positions at 0 degree intervals (see FIG. 5). The reference plane 32 and the reference plane 34 that correspond to each other in the vertical direction are formed so as to be located in the same plane extending in the vertical direction.

The upper die 2 formed on the upper die pressing body die 20.
The center position of the barrel mold hole (molding mold insertion support hole) 36 into which 2 is inserted is determined with reference to the reference plane 32. Similarly, the lower mold 2 formed on the lower mold holding cylinder mold 24
The center position of the barrel die hole (forming die insertion support hole) 38 into which 6 is inserted is determined with reference to the reference plane 34. Therefore, the reference planes 3 corresponding to each other in the vertical direction
When the positions of 2 and the reference plane 34 in the vertical direction are completely aligned, the centers of the barrel mold holes 36 and 38 are aligned.

Positioning plates (centering members) 40 extending downward are fixed to the respective reference planes 32 of the upper die pressing cylinder die 20. A taper portion 41 is formed at the lower end of each positioning plate 40 so as to extend outward as it extends downward. With this configuration, when the movable upper die supporting member 14 is lowered to be in a die closing state (a state shown in FIG. 2 in which the lower end of the upper die holding cylinder die 20 and the upper end of the lower die holding body die 24 are aligned with each other), Since the inner flat surface 40a of the positioning plate 40 slides on the corresponding reference flat surface 34 to guide the upper die holding cylinder die 20 onto the lower die holding barrel die 24, the reference plane 32 and the reference plane that correspond to each other in the vertical direction. The position in the up-and-down direction with 34 completely matches. Therefore, the centers of the body mold hole 36 and the body mold hole 38 are coincident with each other, so that the upper mold 22 and the lower mold 26 are reliably centered. In addition, when the positions of the upper die pressing body die 20 and the lower die holding body die 24 are slightly deviated in the vertical direction, that is, before the movable upper die support member 14 is lowered, the upper die holding body die 20 is vertically moved. Even if the positions of the reference planes 32 and the corresponding reference planes 34 of the lower die holding cylinder die 24 are slightly deviated from each other, the taper portion 4 of the positioning plate 40 is formed.
Since the position shift is adjusted by 1, the positions of the reference plane 32 and the reference plane 34, which correspond to each other in the vertical direction, in the vertical direction completely match each other.
The centering with is surely performed.

As shown in FIG. 3, each of the upper mold 22 and the lower mold 26 used in the present invention has a concave molding surface 42. In each of the upper mold 22 and the lower mold 26, the thin film 2 for the purpose of heat resistance, oxidation resistance and wettability is formed on the surface of the base material 1 on the molding surface 42 side. Each of the upper die 22 and the lower die 26 integrally has a flange portion 3 at the end opposite to the end on which the molding surface 42 is formed, and the corresponding barrel die hole 36 is formed by the flange portion 3. Alternatively, it is prevented from coming off from the body mold hole 38.

Each of the molds including the upper mold 22 and the lower mold 26 has a linear expansion coefficient α ₁ of 48 × 10 ⁻⁷ / deg (α ₁ = 48).
It is prepared using a cemented carbide tungsten carbide WC having a density of × 10 ^-7 / deg) as a base material. In this preparation, first, the forming surface of the above-mentioned base metal cemented carbide tungsten carbide WC was ground with an ultra-precision lathe and then ground with a diamond abrasive to a surface roughness R _{max of} 0.02 μm or less. A thin film 2 made of a platinum film having a thickness of 1 μm is formed on the surface by sputtering.

On the other hand, the upper die holding cylinder die 20 and the lower die holding body die 24 each have a linear expansion coefficient smaller than that of the base material of the upper die 22 and the lower die 26 (that is, the mother die of the upper die 22 and the lower die 26). Material whose coefficient of thermal expansion is lower than that of the material, linear expansion coefficient α ₂ is 38 ×
It is made using silicon carbide (SiC) of 10 ⁻⁷ / deg (α ₂ = 38 × 10 ⁻⁷ / deg).

Then, the molding apparatus 10 to which the present invention is applied.
Satisfies the following equation. 0 ≦ D + D × α ₂ × T− (K + K × α ₁ × T) <0.010, where D is the inner diameter (mm) of each of the cylinder mold holes 36 and 38 at room temperature, and K is each cylinder mold at room temperature. The outer diameter (mm) of the insertion portion of the holes 36, 38, T is the temperature difference (° C.) between the molding temperature and room temperature.

When the above equation is satisfied, D
> K and large clearance.
The clearance between 6 (or the barrel die hole 38) and the upper die 22 (lower die 26) is 10 microns or less. If the clearance between both molds is less than 10 microns during molding, the upper mold and the lower mold will be securely supported in the corresponding body mold holes at the time of molding, and the clearance between them will increase at room temperature, and the upper mold and the lower mold will become larger. Can be easily attached and detached from the corresponding body-shaped hole.

Now, the normal temperature is 20 ° C., and the outer diameter of each insertion portion of the upper mold 22 and the lower mold 26 at this normal temperature is 16.000.
mm, preform 4 to be molded is V made of Sumita Optical Glass
C78 (molding temperature 580 ° C.), and the barrel-shaped hole 36 during molding
In order to have a clearance of 3 microns between the upper mold 22 and the upper mold 22, and between the body mold hole 38 and the lower mold 26,
The inner diameters of the body mold hole 36 and the body mold hole 38 may be calculated as follows using the above equations.

D + D × (38 × 10 ⁻⁷ × (580-2
0))-(16 + 16 × 48 × 10 ⁻⁷ × 560) = 0.
Since it is 003, D = (16 (1 + 48 × 10 ⁻⁷ × 560)) / (1 + 3
8 × 10 ⁻⁷ × 560) + 0.003 = 16.009 +
0.003 = 16.012 Therefore, the inner diameter of each barrel-shaped hole 36, 38 is 16.12 mm.
And it is sufficient.

A specific example of molding an optical element by the illustrated molding apparatus 10 of the present invention will be described. FIG. 1 shows a state before molding in which the preform 4 is placed on the molding surface of the lower mold 26, and FIG. 2 shows a state in which the preform 4 is press-molded.

First, as shown in FIG. 1, with the upper die 22 and the lower die 26 separated from each other, the preform 4 is placed on the molding surface 42 of the lower die 26. After that, the movable upper die support member 14 is lowered to form the upper die 22 into the preform 4
The quartz tube 16 is lowered so as not to come into contact with the mold, and at the same time, the quartz tube 16 is lowered to surround the periphery of the mold and heated by the heater 18 while purging the quartz tube 16 with an inert gas.

The temperature measured by the thermocouples 29 and 30 is 5
When the temperature reaches 80 ° C., the movable upper mold support member 14 is further lowered, and the preform 4 is crushed between the upper mold 22 and the lower mold 26 to perform press molding (FIG. 2). The molding pressure at this time is usually around 100 kg / cm ² . When the movable upper die support member 14 is lowered, the inner planes 40a of the positioning plates 40 slide on the corresponding reference planes 34, and the upper die 22 and the lower die 26 are centered.

After the molding of the preform 4 between the upper mold 22 and the lower mold 26 is completed, the heater 18 is stopped and cooled. After that, when the temperature measured by the thermocouples 29 and 30 reaches a temperature (490 ° C.) below the glass transition point of the molding material, the movable upper die support member 14 and the quartz tube 16 are raised. afterwards,
The optical element molded product is taken out of the apparatus from above the lower mold 26.

Molding apparatus 1 of the present embodiment having the above-mentioned structure
In No. 0, after repeating the above-mentioned forming process 10,000 times, the upper die 2 and the upper die 2 are replaced by the upper die 2 to replace the forming die.
2. The lower mold 26 was taken out, but there was no seizure between them and it could be taken out easily.

In the conventional molding apparatus, since the molding die and the pressing cylinder die are made of the same material or a material having substantially the same linear expansion coefficient, if the clearance between the molding die and the pressing cylinder die is small, both of them can be used. There was a risk of burning,
According to the optical element molding apparatus to which the present invention is applied, the clearance between the two becomes small at the time of molding, so that the processing accuracy of the molded product is good, and the clearance becomes large at the time of cooling, so that there is no fear of seizing both.

In the above embodiment, the thin film 2 on the molding surface 42 of the molding die is formed as a thin film 2 made of a platinum film with a thickness of 1 μm by sputtering, but the present invention is not limited to this and other than sputtering. Other methods such as ion plating may be used to form the thin film 2 made of not only platinum but also other metals (such as gold) and various ceramics. Moreover, the thickness of the thin film 2 is not limited to 1 μm.

Further, in the above embodiment, the upper die 22 and the lower die 26.
Each of the above is made by using a cemented carbide tungsten carbide WC having a linear expansion coefficient α ₁ of 48 × 10 ⁻⁷ / deg as a base material, but the present invention is not limited to this and the upper die holding cylinder die 20 is used. Any other material may be used as long as it is made of a material having a linear expansion coefficient larger than that of the base material forming each of the lower die holding cylinder die 24. Similarly, each of the upper die holding cylinder die 20 and the lower die holding cylinder die 24 has a linear expansion coefficient α ₂ of 38 × 10 ⁻⁷ /
Although it is made using silicon carbide (SiC) of deg, the present invention is not limited to this, and as long as it is made of a material having a smaller linear expansion coefficient than the base materials of the upper mold 22 and the lower mold 26, Other materials may be used.

In the above embodiment, the upper die 22 and the lower die 26
Made of the same material (with a linear expansion coefficient α ₁ of 48 × 10 ^-7 / deg
And the upper holding cylinder die 20 and the lower holding cylinder die 24 are also made of the same material (silicon carbide having a linear expansion coefficient α ₂ of 38 × 10 ⁻⁷ / deg). However, the present invention is not limited to this, and the upper die 22 and the lower die 26 are made of different materials, and the upper die holding body die 20 and the lower die holding body die 24 are connected to the upper die 22 and the lower die 26. They may be made of different materials selected in consideration of the linear expansion coefficient of each constituent material. In this case, the linear expansion coefficients of the constituent materials of the upper mold 22 and the lower mold 26 are α ₁ , α ₁ ′,
When the linear expansion coefficients of the constituent materials of the upper die holding cylinder die 32 and the lower die holding cylinder die 34 are α ₂ and α ₂ ′, respectively, α ₁ > α ₂
And the relation of α ₁ '> α ₂ ' (α ₂ = α ₂ ') should be established.

Further, in the above embodiment, the barrel-shaped hole 36 is formed at the time of molding.
The inner diameters of the body mold hole 36 and the body mold hole 38 are determined according to the above formula so that a clearance of 3 microns is provided between the upper mold 22 and the upper mold 22, and between the body mold hole 38 and the lower mold 26. However, the present invention is not limited to this, and between the body die hole 36 and the upper die 22 and the body die hole 38 and the lower die 2 at the time of molding.
It suffices that the clearance between each of them and 6 is 10 microns or less.

Further, in the above-mentioned embodiment, each holding cylinder die 20,
Although four reference planes are formed on each of 24,
The number of reference planes is not limited to this number, and may be three or five or more. In the above embodiment, the positioning plate 40 is
Although it is configured to provide three, depending on the number of reference planes provided, three
It may be one or five or more.

In the above embodiment, the positioning plate 40 is fixed to the reference planes 32 on the upper die holding cylinder die 20 side. However, it is fixed to the reference planes 34 on the lower die holding barrel die 24 side. Also, the same effect can be obtained. Further, the positioning plate 40 has the upper die holding body die 20 or the lower die holding body die 2
4 may be integrally formed.

Further, in the above-mentioned embodiment, each holding cylinder die 20,
Although the reference planes of 24 are configured as the reference planes 32 and 34 which are planes, they may be formed as curved planes extending in the vertical direction. In this case, the inner side surface of the positioning plate 40 may also be configured as a curved surface corresponding to the curved surface of the reference surface. Further, as shown in FIG. 6, the reference planes 32 and 34 and the positioning plate 40 are not formed, and a plurality of holes 44 and 46 are formed at positions corresponding to each other in the vertical direction in each of the pressing barrel dies 20 and 24. And the inner peripheral surfaces of these holes 44 and 46 are formed on the reference plane 3 respectively.
2 ', 34', and upper and lower pressing body molds in which either one of the holes 44, 46 (each hole 46 in FIG. 6) corresponds to the shape of the holes 44, 46 and the tip end portion is tapered. Even when the columnar positioning member (centering member) 48 made of the same material as 20, 24 is fixed, when the upper die holding cylinder die 20 is combined with the lower die holding cylinder die 24, the respective positions are closed. The peripheral surface of the delivery member 48 slides on the reference surface 32 '(or reference surface 34') of the corresponding hole 44 (or hole 46) to guide the upper die pressing cylinder die 20 onto the lower die pressing cylinder die 24. Therefore, similar to the above-described embodiment, the upper mold 22 and the lower mold 26
Can be centered.

The above-described molding apparatus 10 includes a pair of upper molds 22.
However, the present invention is not limited to the number of pairs of molding dies, and may be configured to include two or more pairs of upper dies and lower dies. Further, in the above-described embodiment and molding example, the molding apparatus of the present invention is used as the molding apparatus 10
However, the present invention is not limited to this, and the present invention can be applied to a molding apparatus having another structure as long as it is a molding apparatus including an upper mold and a lower mold that are brought into contact with and separated from each other. .

[0034]

As described above, according to the optical element molding apparatus of the present invention, the linear expansion coefficients of the constituent materials of the upper mold and the lower mold are respectively α ₁ , α ₁ ′, and the upper mold holding cylinder mold. When the linear expansion coefficient of each constituent material of the lower die holding cylinder die is α ₂ and α ₂ ′, α
_{Since the} configuration is such that the relationship of ₁ > α ₂ and α ₁ '> α ₂ ' is established, it has an upper die and an upper die holding cylinder die that supports it, and a lower die and a lower die holding body die that supports it. In the optical element molding apparatus, the molding die can be easily taken out of the barrel die even if molding is repeated many times. According to the invention of claim 4, the upper die and the lower die are surely centered.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a molding apparatus to which the present invention is applied.

FIG. 2 is a vertical sectional view showing the molding apparatus of FIG. 1 in a state different from that of FIG.

3 is a vertical cross-sectional view of an upper die or a lower die of the molding apparatus of FIG.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a top view of the lower die holding cylinder die with the lower die attached, as viewed from above.

FIG. 6 is a modification of the molding apparatus shown in FIG.

[Explanation of symbols]

 10 Molding Equipment 12 Fixed Lower Mold Base 14 Movable Upper Mold Support Member 16 Quartz Tube 18 Heater 20 Upper Mold Holding Body Mold 22 Upper Mold 24 Lower Mold Holding Body Mold 26 Lower Mold 29 30 Thermocouple 32 34 Reference Plane (Reference Surface) 36 38 Body Mold Hole (Molding Mold Insertion Support Hole) 40 Positioning Plate (Centering Member) 42 Molding Surface

Claims (6)

[Claims] 1. A molding apparatus for molding an optical element by pressing an optical element material softened by heating with a molding die composed of an upper die and a lower die, and an upper die pressing body die for supporting the upper die. A lower die holding body die supporting the lower die, which is provided as a separate member from the upper die holding body die; and the linear expansion coefficient of each of the constituent materials of the upper die and the lower die is α ₁ , respectively.
alpha ₁ ', the linear expansion coefficient of each constituent material of the upper mold pressing the body mold and the lower mold holding barrel die each alpha _2, alpha _2' when the relationship α _1> α ₂ cutlet α ₁ '> α _2' An optical element molding apparatus, characterized in that 2. A molding die insertion support hole for inserting and supporting a corresponding upper die or lower die is formed in each of the upper die holding body die and the lower die holding body die according to claim 1. The inner diameter of this mold insertion support hole at room temperature is D (mm), the outer diameter of the corresponding upper mold or lower mold inserted into this mold insertion support hole at room temperature is K (mm), molding temperature and room temperature When the temperature difference with is T (° C.), 0 ≦ D + D × α ₂ × T− (K + K × α ₁ × T) <0.0
10 and 0 ≦ D + D × α ₂ ′ × T− (K + K × α ₁ ′ × T) <0.0
An optical element molding apparatus that satisfies the relationship of 10. 3. The upper die holding body die and the lower die holding body die according to claim 1 or 2, wherein each of the upper die holding body die and the lower die holding body die is formed with at least one reference surface extending parallel to a contacting / separating direction of the forming die. The molding die insertion support hole is a molding device for an optical element, which is positioned with reference to the above-mentioned reference surface of the corresponding pressing barrel die. 4. The reference surface of any one of the upper die holding cylinder die and the lower die holding barrel die according to claim 3, when the upper die holding die die and the lower die holding die die are brought close to each other, A molding device for an optical element, in which a centering member for slidingly contacting the corresponding reference surface for centering the upper die and the lower die is fixed. 5. In a molding apparatus for molding an optical element by pressing an optical element material softened by heating with a molding die composed of an upper die and a lower die, an upper die insertion support hole for inserting and supporting the upper die. An upper die holding cylinder die having a lower die inserting support hole for inserting and supporting the lower die, and a lower die holding body die made of a member different from the upper die holding body die, and the upper die and the upper die. The holding cylinder mold, and the lower mold and lower mold holding cylinder mold, respectively, have the clearance between the upper mold and the upper mold insertion support hole when not heated, and the clearance between the lower mold and the lower mold insertion support hole when not heated. The molding apparatus for an optical element is characterized in that each of the clearances is made of a different material having a linear expansion coefficient that is larger than both clearances during the heat molding. 6. The optical element molding apparatus according to claim 1, wherein the optical element material is a glass material.