JP2004217459A - Mold for glass-made optical element, and processing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an improved mold which is easily set and unnecessitates a posttreatment, such as centering or deburring, in economically advantageously molding a glass-made optical element. <P>SOLUTION: The mold for molding a glass-made optical element has a tubular trunk mold 6 and a pair of force plungers 7, 8 freely slidably inserted into the mold 6. A glass material heated to a specified temperature and placed between the plungers 7, 8 having been inserted in the mold 6 is press molded by causing the plungers 7, 8 to forcibly approach to each other, giving the glass-made optical element. The plungers 7, 8 are made of a material having a thermal expansion coefficient higher than that of the material of the mold 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mold for glass optical elements such as a lens and a prism used in a device for a CD drive, a laser device, a camera, a microscope, a telescope, an optical fiber and the like, and a processing machine for a glass optical element. The present invention relates to a molding die for molding.
[0002]
[Prior art]
Conventionally, glass lenses have been manufactured using a processing method involving a plurality of steps including a step of grinding a lens base material and a polishing step, but the use of lenses has increased due to the development of optical elements in recent years. In order to cope with such a situation, a manufacturing method in which lens molding is performed by molding excellent in mass productivity is being changed.
[0003]
For example, the molding of a glass lens includes a downward pressing die having a vertical cylindrical cross section, an upward pressing die having a reverse convex cylindrical shape, and a main body die having a small diameter in these upper and lower pressing dies. It is common to use a molding die composed of a cylindrical body die that can be fitted over the entire part. That is, the molding glass is put between the upper and lower pressing dies, and the upper and lower pressing dies are moved closer to each other while softening the molding glass by raising the temperature of the mold to a high temperature, so that a predetermined time can be efficiently obtained. This is a manufacturing method of press forming into a shape. As such a molding, the one shown in Patent Document 1 is known.
[0004]
[Patent Document 1]
JP-A-2002-220239
[Problems to be solved by the invention]
In molding with the advantage of being able to produce at low cost, in order to make a high-precision lens, molding using three molds, upper and lower pressing molds and barrel molds, requires upper and lower molds, and lower pushing. The point is how to reduce the fitting gap between the mold and the body mold. That is, if the gap is reduced, the optical axis concentricity of the lens is improved, and there is an advantage that post-processing (grinding) or the like for centering becomes unnecessary, but it is difficult to perform a setting operation for fitting the dies. In addition, when molding (hot pressing) at a high temperature near the glass softening point, the molds may be damaged or bitten by contact with each other, or the material of the mold may be SiC (silicon carbide). In the case of a brittle material, there is a possibility of inconvenience such as chipping.
[0006]
Therefore, if the above-mentioned fitting gap is enlarged, the setting work of the dies and the molding itself become easy, but the accuracy (deviation of the optical axis) of the molded lens is not good, and burrs are easily generated, and Post processing for deburring and deburring is required. In other words, no matter which method is used, there are advantages and disadvantages.Therefore, at present, there is no choice but to set the size of the gap in consideration of the type and purpose of the molded product, and there is room for improvement in molding. Was.
[0007]
An object of the present invention is to perform a molding process which is economically advantageous for manufacturing a glass optical element, in which a mold setting operation is easy, and post-processing such as centering and deburring is not required. Thus, the present invention is to achieve an improved mold.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a glass mold for an optical element, comprising: a cylindrical body die; and a pair of pressing dies which are slidably fitted in the body die. In a state in which the pair of pressing dies are forcibly moved relative to each other in a state, the glass material interposed between the two pressing dies is press-formed while being heated to a predetermined temperature to form a glass optical element. In addition, the thermal expansion coefficient of the material of the pressing die is set to be larger than the thermal expansion coefficient of the material of the body die.
[0009]
The temperature of the molding die is low during the fitting set operation of the die for fitting the pressing die into the body die, and becomes high during the molding after heating and raising the temperature. Since the coefficient of thermal expansion of the material of the stamping die is set to be larger than the coefficient of thermal expansion of the material, the gap between the body mold and the stamping die is set to be larger when the fitting set operation of the mold with relatively low temperature is performed. It is possible to smoothly and easily assemble the molding die without inconvenience such as strong rubbing against each other or chipping due to the corner of the die.
[0010]
Then, when the glass material is heated to press molding and becomes relatively high in temperature, the inner press die fitted inside the trunk die expands more than the trunk die arranged outside, The gap between the die and the die becomes smaller than when the die is set, and the phenomenon that the softened glass material enters between the die and the die due to the pressure of press molding occurs more than before. It can be difficult or not to happen. As a result, it is possible to obtain an advantage that burrs and misalignment of the optical axis are suppressed or eliminated, and post-processing such as deburring and optical axis adjustment is reduced or unnecessary.
[0011]
A cemented carbide such as WC (tungsten carbide) having a large thermal expansion coefficient as a material of the body mold and SiC (silicon carbide) having a small thermal expansion coefficient. In this case, it is possible to obtain the function and effect of the configuration of claim 1 while making the mold material suitable for mass production that is general and easily available.
[0012]
Furthermore, when the glass optical element having a diameter of about 10 mm is formed as in the configuration of claim 3, the gap d between the body mold and the press mold is set to 0.011 mm ≦ d ≦ 0.023 mm. Although the details will be described in the section of the embodiment, the operation and effect of the configuration of claim 2 can be more reliably enjoyed.
[0013]
According to a fourth aspect of the present invention, in the glass optical element processing machine, a cylindrical body, a pair of push dies that are slidably fitted in the body, and a pair of push dies that are fitted in the body. A driving mechanism capable of forcibly moving the pressing dies relative to each other and a heating means capable of heating a glass material disposed between a pair of the pressing dies in a state of being fitted in the drum, and a drum. The thermal expansion coefficient of the material of the pressing die is set to be larger than the thermal expansion coefficient of the material.
[0014]
According to a fourth aspect of the present invention, there is provided a processing machine using the glass optical element forming die defined by the first aspect of the present invention. According to the configuration of claim 1, the coefficient of thermal expansion of the material of the pressing mold is larger than the coefficient of thermal expansion of the material of the body mold, although the temperature is low during the joint setting operation and high during molding after heating. Because it is set, the gap between the body die and the press die is made large at the time of the fitting set operation of the molding die with a relatively low temperature, and there is no inconvenience such that the dies are strongly rubbed or the corners of the dies hit and chipped The mold can be smoothly and easily assembled.
[0015]
Then, at the time of molding that is heated to a relatively high temperature, the inner die that is fitted inside the die expands more than the die that is disposed outside, so that the die and the die are not squeezed. The gap is smaller than when the mold is set. Therefore, the phenomenon that the glass material in the softened state under pressure enters between the barrel mold and the press mold can be less likely or not to occur as compared with the conventional case, and burrs and misalignment of the optical axis can be suppressed. Or, it is eliminated, and post-processing such as deburring and optical axis adjustment is reduced or becomes unnecessary, while the optical axis accuracy is greatly improved, and the glass optical element created by the glass optical element processing machine is used. Performance was improved.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
【Example】
FIG. 1 shows a glass lens processing machine A as an example of a glass optical element processing machine, and FIG. 2 shows a model diagram of a molding die S used for the processing machine A. The glass lens forming apparatus A is provided with a molding die S on the upper floor 2 of the frame 1, a mold driving mechanism 4 on the lower floor 3, and controls the temperature of the molding die S and the driving control of the mold driving mechanism 4. It is configured to include a control device 5 for controlling.
[0018]
The molding die S includes a hollow cylindrical body die 6, an upper pressing die 7 which is internally fitted to the body die 6 so as to be vertically slidable, and a lower pressing die 8 which is also internally fitted to the body die 6 so as to be vertically slidable. It is composed of The upper pressing die 7 is provided so as to be suspended and fixed to the upper wall 9 of the frame 1, and is configured to drive up and down the lower pressing die 8 by the die driving mechanism 4. (Example of means) 10 is housed in a trunk mold 6.
[0019]
The mold drive mechanism 4 has an AC servomotor 11 as a drive source, and supports a downward press mold 7 via a load cell 12 on an output table 4a that can be driven up and down. Each of the upper and lower pressing dies 7 and 8 is formed with a nitrogen gas (inert gas) introduction path 13 for obtaining an atmosphere in which the glass lens can be formed stably. An exhaust path 15 for evacuating the inside of the chamber 14 which is the inner peripheral wall of the body die 6 is also formed.
[0020]
As shown in FIG. 3, the processing machine A (in the molding die S) has a granular glass material (preform) having a diameter of 9.7 mm and a height of 6.6 mm, which has an elliptical shape in a side view. Use 16. The characteristics of the glass material 16 are L-LAM69 and Tg = 497 ° C. By molding this glass material 16 with the molding apparatus A shown in FIG. 1, a convex lens (glass optical element) having a diameter of 10 mm can be formed.
[0021]
The forming operation by the processing machine A is as follows. First, the dies 6 to 8 are assembled and set so that the glass material 16 is arranged between the upper and lower pressing dies 7 and 8, and then the exhaust device and the exhaust path 15 not shown. The inside of the chamber 14 is evacuated using. Then, the mold S is heated to a predetermined high temperature by turning on the infrared lamp 10, and then nitrogen gas is introduced from the upper and lower introduction paths 13 into the chamber 14 until atmospheric pressure is reached. The downward pressing die 8 is moved upward by the drive of 11, and pressurized to a predetermined pressure. After being held for 5 minutes, the molded body is taken out after cooling.
[0022]
The specific main specifications of the processing machine A are that the molding die S is molded at a temperature of 500 ° C. and a press pressure of 10 MPa, and after maintaining the state for 5 minutes, it is cooled. The body 7 is made of a SiC sintered body, and the upper and lower pressing dies are made of WC (tungsten carbide), which is a cemented carbide. The SiC sintered body has a purity of 99% and a density of 3.17 grams / cubic centimeter (g / cm3), a coefficient of thermal expansion of up to 600 ° C. and an average of 4/100000 ° C. (4 / million ° C.). Has an average coefficient of thermal expansion of 6 / 1,000,000 ° C. (6 / million ° C.) up to 600 ° C.
[0023]
In molding a glass lens using the processing machine A and the glass material 16 under the above-described conditions, ease of mold setting when the fitting tolerance between the body mold 6 and the vertical pressing molds 7 and 8 is variously changed and set, FIG. 5 shows a list summarizing the status of molded articles (whether or not burrs are generated). In FIG. 5, D1 is the outer diameter of the pressing dies 7 and 8 at normal temperature, D2 is the inner diameter of the drum dies 6 at normal temperature, D3 is the outer diameter of the pressing dies 7 and 8 at 500 ° C., and D4 is the diameter of the drum dies 6 at 500 ° C. It is the inner diameter, and the thermal expansion coefficient of SiC, which is the material of the body mold 6, is set to 3.8 to 4.2 / 1,000,000 ° C (3.8 to 4.2 / million ° C) in the range of 25 to 600 ° C. The coefficient of thermal expansion of WC, which is the material of the pressing dies 7 and 8, is set to 5.8 to 6.2 / 1,000,000 ° C (5.8 to 6.2 / million ° C) in the range of 25 to 600 ° C. It is.
[0024]
FIG. 4 shows a conceptual diagram in which burrs are generated by molding. If the gap between the outer diameters of the pressing dies 7 and 8 and the inner diameter of the body mold 6 is large at the time of molding at a high temperature, the glass material enters into the gap, which becomes a burr. Is sufficiently small, the glass material cannot enter, and a good glass lens without burrs can be produced.
[0025]
As a result of observing the shape of the glass lens obtained by the molding by the processing machine A, when the body die 6 and the pressing dies 7, 8 are made of the same material, the clearance d (D2-D1) at room temperature is about 10 μm and the mold is formed. The assembling to set and fit each other is tight, especially when the material is SiC, the edges of the pressing dies 7 and 8 are easily chipped, and a gap d at room temperature of about 20 μm is required for assembling. There was found. Further, even when the gap d is about 9 μm, burrs are generated in the glass molded body, and it is necessary to further reduce the gap d in order to eliminate the burrs.
[0026]
On the other hand, when the material of the body mold 6 is SiC and the material of the press dies 7 and 8 is WC, when the room temperature gap d (D2−D1) is about 14 μm, the molding gap k at the time of molding at 500 ° C. (D4-D3) became smaller than 14 μm, and the burr of the glass molded article was reduced to a slightly recognizable degree. Furthermore, when the room temperature gap d (D2−D1) is about 11 μm, a state in which burrs are hardly observed after molding is obtained, and the molding gap k (D4−D3) is estimated to be close to 2 μm. I was able to speculate.
[0027]
From various experimental results as shown in FIG. 5, when a lens (glass optical element) having a diameter of about 10 mm is formed, the normal-temperature gap d (D2-D1) and the molding gap k (D4-D3) are:
Z: 0.011 mm ≦ d (D2−D1) ≦ 0.023 mm
Y: 0.002 mm ≦ k (D4-D3) ≦ 0.014 mm
It is good to set in the range.
[0028]
More preferably,
X: 0.011 mm <d (D2-D1) <0.023 mm
W: 0.002 mm <k (D4-D3) <0.014 mm
It is good to set in the range.
[0029]
That is, it is possible to easily mold the glass lens with high productivity and to produce a glass lens at low cost without inconvenience in the fitting and setting operation of the mold. Can be made almost zero (zero), and there is no burr, and the optical axis accuracy as a lens can be dramatically improved. Conversely, if the gap d at the time of setting the mold at a low temperature such as room temperature is set so as to satisfy the above equation Z (or the previous equation X), the gap k at the time of molding at a high temperature will be the same as the equation Y (or the previous equation). A material having a thermal expansion coefficient that satisfies W) may be set as a material for the body mold or the push mold.
[0030]
In other words, the use of cemented carbide (WC) as the material of the pressing dies 7 and 8 reduces the occurrence of chipping as compared with the case of SiC material, and can make use of the toughness of cemented carbide (WC). I was able to prove it. Since the specific gravity of SiC, which is the material of the body mold 6, is 1/5 smaller than that of WC and the weight of the mold is light, the heat capacity of the mold is small, so that the temperature rise to the molding temperature is fast and the thermal conductivity is low. Since it is as large as two to three times, there is also an advantage that the mold is quickly burned and energy is saved.
[0031]
[Another embodiment]
The shape of the fitting portion between the body die 6 and the pressing dies 7, 8 can be circular, triangular, quadrangular, polygonal, or the like. Also, a molding die (not shown) composed of two dies, a trunk die having a recessed hole as a molding space, and a convex pressing die that can be fitted in the hole, The present invention is applicable. FIG. 5 shows a case where a glass optical element having a diameter of about 10 mm is formed. However, the present invention can be applied to a case where a glass optical element having a diameter other than 10 mm is formed.
[0032]
【The invention's effect】
As described above, the glass optical element forming die and the glass optical element processing machine using the same according to the present invention include a cylindrical body die and a pair of slidably fitted inside the body die. Pressing the glass material disposed between the two pressing dies while being heated to a predetermined temperature by a forced relative approach movement of the pair of pressing dies in a state where the pressing dies are fitted inside the body die. The optical element made of glass is formed by molding, and the coefficient of thermal expansion of the material of the pressing mold is set to be larger than that of the material of the body mold.
[0033]
As a result, by using a pressing mold having a large thermal expansion coefficient and a body mold having a small thermal expansion coefficient, at room temperature for setting the mold, the gap between the body mold and the pressing mold is sufficiently large, so that the work of setting the mold can be performed. It can be easily performed without any inconvenience, and since the molding is at a high temperature near the glass softening point, the expansion amount of the stamping die is larger than the expansion amount of the drum die, and the gap between the drum die and the pressing die (radial direction) Gap) can be made as close to zero as possible. As a result, although the molding was economical and could be performed at low cost, burrs did not occur and the optical axis accuracy of the lens could be dramatically improved.
[Brief description of the drawings]
1 is an overall side view showing a schematic structure of a glass lens processing machine. [FIG. 2] FIG. 2 is a model diagram showing a structure of a molding die. [FIG. 3] FIG. FIG. 4 is a schematic diagram showing burrs of a glass lens. FIG. 5 is a diagram showing various specifications of a lens mold.
4 Driving mechanism 6 Body type 7, 8 Push type d Clearance

Claims (4)

A cylindrical body mold and a pair of press dies that are slidably fitted in the body mold, and a forced relative approach movement of the pair of the press dies in a state of being fitted in the body mold, While being configured to press-mold a glass material disposed between the two pressing dies in a state where it is heated to a predetermined temperature to form a glass optical element, the thermal expansion coefficient of the material of the body mold is more than the above. A mold for optical elements made of glass in which the material of the press mold has a large coefficient of thermal expansion. The molding die for a glass optical element according to claim 1, wherein the material of the body die is set to SiC, and the material of the pressing die is set to a cemented carbide. The molding die for a glass optical element according to claim 2, wherein when forming the glass optical element having a diameter of about 10 mm, a gap d between the body die and the pressing die is set as in the following formula Z. .
Formula Z: 0.011 mm ≦ d ≦ 0.023 mm A cylindrical body, a pair of dies that are slidably fitted in the body, and a pair of the dies in the state of being fitted in the body, and a drive that is forcibly movable toward and away from each other. A mechanism and a heating means capable of heating a glass material disposed between the pair of the pressing dies in a state of being fitted in the body die, and the pressing mold having a coefficient of thermal expansion greater than a material of the body die. A glass optical element processing machine in which the thermal expansion coefficient of the material is set to a large value.

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