JP2005272279A - Apparatus and method for forming optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an optical element even having a complicated shape difficult to form with excellent transfer accuracy without lengthening a cycle time. <P>SOLUTION: The apparatus for forming the optical element forms the optical element by forming an optical element base material into the optical element with the use of a pair of forming dies. The apparatus has a pair of the forming dies 4 and 8 for pressing the optical element base material 7 softened by heating and a pair of plates 3a and 9a each of which is provided with a heater 12 and a part of which being in contact with each of a pair of the forming dies 4 and 8 in cooling the pressed optical element base material 7 is composed of a material having ≤30 W/(m×K) thermal conductivity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

When manufacturing an optical element by press molding, it is desirable to shorten the cycle time and improve the efficiency. As such a conventional molding method, Patent Document 1 describes that a plurality of press shafts are arranged, a predetermined process is performed on each press shaft, and the mold is sequentially transferred to be molded.
JP 2001-151518 A

  In the conventional molding method described above, it is necessary to set the temperature and transfer the mold for each press shaft process. For example, in the process of determining the shape, the cooling rate at the stage where the glass material is solidified from the fluid state is a major factor. Therefore, contrary to the importance of the set temperature in this process, the glass is rapidly cooled at the moment it is transferred to the cooling stage. In the case of a complicated shape such as an aspherical shape that is thin (hereinafter referred to as edge thickness) and is difficult to mold, the transfer accuracy deteriorates due to rapid cooling. For this reason, the number of stages is increased to make the temperature lowering step gentle.

  On the other hand, the above publication describes that even a single press stage can be used, but even in this case, it is necessary to control the temperature of the stage. Therefore, in these countermeasures, the cycle time becomes long and the apparatus becomes large, so that the efficiency is low and it is not possible to easily cope with it.

  The present invention has been made in consideration of such circumstances, and provides a molding apparatus and a molding method capable of easily obtaining high-precision transfer accuracy even with an optical element having a complicated shape that is difficult to mold. The purpose is to provide.

  An optical element molding apparatus according to a first aspect of the present invention is an optical element molding apparatus in which an optical element material is molded by a pair of molding dies into an optical element, and a pair of molding dies for pressing the heat-softened optical element material; A pair of plates each having a heater and having a material having a thermal conductivity of 30 W / (m · K) or less in contact with the pair of molds when the pressed optical element material is cooled. It is characterized by that.

  In the first aspect of the present invention, the portion of the plate that comes into contact with the mold has a thermal conductivity of 30 W / (m · K) or less, so that the optical element material can be cooled by slowing the cooling rate. Therefore, the transfer accuracy can be improved.

  An optical element molding apparatus according to a second aspect of the present invention is an optical element molding apparatus in which an optical element material is molded by a pair of molding dies into an optical element, and a pair of molding dies for pressing the heat-softened optical element material; And a pair of plates each having an area of a portion that comes into contact with the bottom surfaces of the pair of molds when the pressed optical element material is cooled, and is smaller than the entire area of the bottom surfaces. And

  In the invention of claim 2, since the area of the portion of the plate that comes into contact with the mold is reduced, the optical element material can be cooled by slowing the cooling rate, so that the transfer accuracy can be improved. it can.

  A third aspect of the present invention is the optical element molding apparatus according to the first or second aspect, wherein the portions respectively in contact with the pair of molds are removable from the plate.

  According to the invention described in claim 3, since only the contact portion with the pair of molds can be exchanged, it is possible to easily cope with wear and the like.

  An optical element molding method according to a fourth aspect of the present invention is an optical element molding method in which an optical element material is molded by a pair of molding dies into an optical element. The pressing step for pressing, the transferring step for transferring the pressed optical element material and the pair of molds to the cooling position, and the material of the portions in contact with the pair of molds, respectively, have a thermal conductivity of 30 W / (m K) A cooling step of cooling a pair of molds by a pair of plates provided with the following heaters.

  In the invention described in claim 4, since cooling is performed using a plate whose portion in contact with the mold has a thermal conductivity of 30 W / (m · K) or less, the cooling rate is decreased to cool the optical element material. As a result, the transfer accuracy can be improved.

  An optical element molding method according to a fifth aspect of the present invention is an optical element molding method in which an optical element material is molded by a pair of molding dies into an optical element. The optical element molding method uses a pair of molding dies that press the heat-softened optical element material. The pressing step for pressing, the transfer step for transferring the pressed optical element material and the pair of molding dies to the cooling position, and the area of the part in contact with the bottom surfaces of the pair of molding dies are the entire area of the bottom surface And a cooling step of cooling the pair of molds with a pair of plates each having a smaller heater.

  In the invention described in claim 5, since the cooling is performed using the plate having a small area in contact with the mold, the optical element material can be cooled by slowing the cooling rate. Accuracy can be improved.

  A sixth aspect of the present invention is the optical element molding method according to the fourth or fifth aspect, wherein the portions respectively in contact with the pair of molds are removable from the plate.

  According to the sixth aspect of the present invention, since only the contact portion with the pair of molds can be exchanged, it is possible to easily cope with wear and the like.

  According to the optical element molding apparatus of the present invention, since it has a plate structure that slows the cooling rate of the mold in the cooling process, the transfer accuracy can be improved, and molding is performed even if the shape is complicated. be able to.

  According to the optical element molding method of the present invention, it is possible to improve the transfer accuracy by slowing the cooling rate. Therefore, it is possible to easily mold a shape that is usually difficult to mold.

  Hereinafter, the present invention will be specifically described with reference to embodiments shown in the drawings. In each embodiment, the same members are assigned the same reference numerals.

(Embodiment 1)
1 to 4 show Embodiment 1 of the present invention, FIG. 1 is an overall front view of an optical element molding apparatus, FIGS. 2 and 3 are perspective and sectional views of a plate used for molding, and FIG. It is a characteristic view of accuracy.

  As shown in FIG. 1, the optical element molding apparatus arranges a plurality of (four) press shafts side by side in a space formed by the entrance shutter 5, the exit shutter 10 and the casing 2. And the optical element is molded. Molding is performed by making the inside of the space an inert gas atmosphere and moving the die block 20 in order from the right press shaft to the left press shaft. The mold block 20 is moved by an arm (not shown).

  Step 1 is a heating step for a glass material as a mold and an optical element material, Step 2 is a pressing step for a glass material, Step 3 is a first cooling step for the pressed optical element, and Step 4 is a temperature at which the optical element can be taken out. This is the second cooling step.

  The mold block 20 is configured by combining the upper mold 4 and the lower mold 8 as a pair of molds and the sleeve 6.

  The upper die 4 is composed of a molding surface portion 4a for molding a glass material, a cylindrical main body portion 4b, and a flange portion 4c having a larger outer diameter than the main body portion 4b. Similarly, it is comprised from the molding surface part 8a, the main-body part 8b, and the flange part 8c. The sleeve 6 has the main body portions 4 b and 8 b of the upper and lower molds 4 and 8 fitted therein, and a lower end portion is placed on the flange portion 8 c of the lower mold 8. In this case, a gap is provided between the upper end portion of the sleeve 6 and the flange portion 4c of the upper die 4 so that the upper die 4 can be lowered in the pressing step of step 2 described later.

  Each press shaft has an upper plate 3 and a lower plate 9 that sandwich the mold block 20. In addition, the upper and lower plates 3, 9 of the press shaft in steps 1, 2, and 3 incorporate a heater 12, and the upper and lower plates 3, 9 of the press shaft in step 4 are cooling pipes 11 through which a coolant such as water circulates. Built in. In this embodiment, the lower plate 9 is fixed at a fixed position, but the upper plate 3 is moved up and down by the cylinder 1.

  FIG. 2 is a perspective view of the lower plate 9a of the press shaft in step 3 as viewed from above. The chip 14 is in contact with the lower mold 8 by installing the chip 14 at a portion where the mold is transferred and placed on the lower plate 9a. The chip 14 is attached to the plate 9 a by forming a recess 24 in the plate body 23 and mounting the chip 14 in the recess 24. The plate body 23 and the chip 14 are made of different materials and different shapes.

  FIG. 3 shows a structure for attaching the chip 14 to the plate 9a. The chip 14 is fixed to the plate body 23 by screws 27 through elastic members 25 and 26 having elasticity, and the plate 9a and the chip 14 are securely fixed even at high temperatures. The chip 14 is fixed in such a manner that the side surface of the chip 14 is sandwiched between the elastic members 25 and 26 and inserted into the concave portion 24 of the plate body 23, and the one elastic member 25 is pressed against the side surface of the chip 14 with a screw 27. It is done by tightening with.

The upper plate 3a on the press shaft in step 3 is the same as the lower plate 9a, and a description thereof is omitted.
In the molding apparatus as described above, the molding die and the glass material are cooled mainly by heat transfer due to heat conduction caused by contact between the molding die and the plate by transferring the molding die onto a low-temperature plate. The heat transfer quantity q per unit time and unit area at this time is expressed as q = t / (m / λ) where λ is the thermal conductivity, t is the change in temperature, and m is the thickness. . Therefore, in order to suppress rapid cooling, it is necessary to reduce the amount of heat transfer, but it can be seen from the above formula that this can be achieved by reducing the thermal conductivity λ and the area. Therefore, as measures for preventing rapid cooling, it is effective to reduce the thermal conductivity of the contact portion of the plate with the mold and to reduce the contact area of the contact portion.

  In this embodiment, the contact portions of the plates 9a and 3a used in step 3 with the forming die are constituted by the chip 14, and the material of the chip 14 is changed to reduce the thermal conductivity. By changing the shape and reducing the contact area, the mold is prevented from being rapidly cooled. The reason for dealing with the chip 14 without changing the whole of the plates 9a and 3a is that the temperature control is not stable when a material having a low thermal conductivity is used. This is because it is necessary to deal with the size. Accordingly, the cooling rate can be easily changed depending on the shape of the optical element such as a lens to be molded, and the cooling rate can be controlled with a simple configuration, so that the cycle time can be shortened.

  Next, molding of the optical element according to this embodiment will be described.

  When a fine gob made of a glass material for molding (transition point 506 ° C., softening point 607 ° C.) is used as the glass material 7 to form a concave meniscus lens, the lens has an outer diameter φ of 15 mm and an optical surface curvature of R30 mm, It is R100 mm, the thickness is 1.1 mm, and it is a complicated shape that is difficult to be molded. When rapid cooling is performed at the time of molding, good transfer accuracy cannot be obtained.

  As shown in FIG. 1, a glass material 7 is placed on a lower mold 8, a cylindrical sleeve 6 is installed, and then the upper mold 4 is gently inserted into the sleeve, The mold block 20 holding the glass material 7 by the lower mold 8 and the sleeve 6 is assembled. At this time, a gap is provided between the upper end portion of the sleeve 6 and the flange portion 4 c of the upper die 4 so that the upper die 4 can be lowered in the pressing step of step 2.

  Next, the mold block 20 is set in front of the shutter 5 and a start button (not shown) is pressed to start molding. Each process has a time setting of 2 minutes.

  In step 1, the mold block 20 is heated to raise the temperature to a temperature at which the glass material 7 can be pressed. In this embodiment, the upper plate 3 connected to the upper mold 4 and the lower plate 9 in contact with the lower mold 8 are set to have a temperature of 570 ° C., respectively. After heating for 2 minutes by heat conduction from the upper plate 3 and the lower plate 9, the mold block 20 is transferred to step 2.

  In step 2, the heated and softened glass material 7 is pressed. The pressing is performed by lowering the upper mold 4 with the upper plate 3 and pressing it with a force of 500N. The pressing is completed in about 1 minute, and the remaining 1 minute is set to hold its own weight with the press pressure released.

  Next, it transfers to the process 3 which performs the 1st cooling of the pressed glass raw material 7. FIG. In this step 3, it is necessary to solidify the glass material 7 to ensure transfer accuracy, and it is necessary to deform the glass material 7 in accordance with the shrinkage of the glass at the time of solidification. When the first cooling is rapid cooling, the thin portion of the glass material is solidified first, so in the concave lens described above, the thin central portion is solidified first, whereas the outer peripheral portion and the thick portion Since the lens is still contracted, the central portion of the lens becomes a stopper when the central portion is solidified, and the shape cannot be pressed and cannot follow the contracting portion because the pressure cannot be pressed. Therefore, it is preferable to keep the cooling rate as slow as possible so that no temperature distribution occurs.

  In the upper plate 3a and the lower plate 9a used in the step 3, chips 14 made of different materials are embedded in portions where the bottom surfaces of the flanges 4a and 8a of the upper and lower molds 4 and 8 are in contact with each other, as shown in FIGS. The chip 14 is not made of the material of the plates 9a and 3a, but is made of other materials. In this embodiment, the entire upper plate 3a and lower plate 9a are made of a cemented carbide having a thermal conductivity of 42 W / (m · K). On the other hand, as the chip 14, zirconia having a thermal conductivity of 1.7 W / (m · K) is used. When the entire upper and lower plates are made of zirconia, the control is difficult because the thermal conductivity of zirconia is small, and the fracture toughness is small, so that the upper and lower plates are likely to be damaged due to cracks. For this reason, the chip | tip 14 which consists of zirconia is used.

  In this embodiment, the chip 14 shown in FIG. 2 has a size of 40 mm in width, 40 mm in length, and 10 mm in thickness with respect to the diameter φ22 mm of the bottom surface of the mold. About these conditions, a magnitude | size and a material can also be calculated | required by simulation etc., and it can also obtain | require from experiment.

  FIG. 4B shows shape measurement data when the chip 14 of this embodiment is used, and the transfer accuracy is improved as compared with the conventional case of FIG. This is apparent from the fact that the PV (peak to valley) value in FIG. 4B is smaller than that in FIG.

  Such an effect is achieved by changing the temperature gradient. That is, when the temperature decrease rate of the glass material 7 is measured, the temperature decrease rate of the glass material 7 from the At point (deflection point temperature) to the Tg point (transition temperature) is conventionally about 3 ° C./second on average. On the other hand, in this embodiment, the average is about 1 ° C./second. Therefore, it is considered that the temperature distribution of the glass material 7 is also reduced, and the transfer accuracy is improved.

  Thus, by providing the chip 9a, 3a at the time of the first cooling with a chip made of a material having low thermal conductivity and controlling the cooling rate, the glass material 7 is good even if it is difficult to form. Transfer accuracy can be obtained. In addition, by changing the material and size of the chip, the cooling rate can be controlled and changed as necessary, so transfer to a shape that is difficult to form without lengthening the cycle or complicating the process Accuracy can be improved.

  Step 4 as the second cooling is a step of cooling the glass material 7 to a temperature at which the glass material 7 can be taken out to form a lens as an optical element. In this step, the temperature was set to 180 ° C. After the process up to step 4 is completed and the mold block 20 is discharged from the apparatus, the upper mold 4 is removed and the molded lens is taken out to complete the molding.

  When the number of moldings is repeated, the plate is reduced by abrasion due to sliding, and a problem occurs in the eccentric accuracy of the molded lens. This is because the inclination of the upper plate 3 and the lower plate 9 influences the inclination of the upper die 4 and the lower die 8 to touch the bottom surfaces of the upper die 4 and the lower die 8 respectively when pressed. . Since the lens eccentricity is determined in the step 3 of performing the first cooling, the inclination of the upper plate 3a and the lower plate 9a in this step is important. In this embodiment, the sliding portion is the chip 14, and since this chip 14 can be easily replaced, the above-described requirements can be easily met. In addition, it is possible to provide the tip 14 with an inclination due to a change in thickness, and this makes it easy to correct the tilt of the plate that is slightly under-adjusted.

  In this embodiment, a plate obtained by changing the material of only the chip part is used, but if the plate itself is designed to be small or the cycle time is allowed, without the configuration of chip mounting, The cooling rate may be reduced by changing the material of the entire plate.

  Although zirconia is used as the material of the chip 14, it can be used if it satisfies the thermal conductivity of ceramics, alloys, stainless steel, or the like. When the material is changed, the required shape based on factors such as specific heat, breaking strength, and linear expansion coefficient is changed, so it is necessary to confirm the transfer accuracy. In this case, the selection can be made in consideration of other costs, availability of materials, workability, and the like.

  According to such an embodiment, in a mold moving type molding apparatus and molding method, even with an optical element such as a lens having a complicated shape that is difficult to mold, high accuracy with a minimum number of stages and a minimum cycle time. Transfer accuracy can be easily obtained.

(Embodiment 2)
In the second embodiment, the overall configuration and operation are the same as in the first embodiment, and the shape of the lens to be molded, the shape of the mold, the glass material to be used, and the like are also the same. In this embodiment, chips 15 having a small contact area with the mold are used for the upper and lower plates 9a, 3a used in step 3 as the first cooling, so that the cooling rate is reduced. It is something to control.

  FIG. 5 shows the lower plate 9a in this embodiment, and the upper plate 3a is the same. A chip 15 is fixed to the lower plate 9a. The chip 15 is made of a cemented carbide made of the same material as that of the plate main body 23 and has a plurality of grooves 16. The plurality of grooves 16 are parallel and extend along the same direction as the feed direction H of the mold block 20 indicated by an arrow.

  By forming the groove 16 in the chip 15, the contact area with the mold is about 50% compared to the contact area in the normal case, so that the cooling rate is halved. As a result, as in the first embodiment, the temperature reduction rate (cooling rate) of the glass material 7 from the At point to the Tg point can be set to about 1 ° C./second on average, and the transfer accuracy is similarly improved. be able to.

  In this embodiment, the groove 16 is formed in the chip 15 portion to reduce the contact area with the mold. However, the contact surface is provided with minute irregularities, or a plurality of circular shapes such as punch metal are provided. The same applies to the formation of holes. Similarly to the first embodiment, not only the chip portion but also the whole may have the same shape, or the cooling rate may be reduced by combining material changes in order to improve transfer accuracy.

  In addition, it is effective that the contact state between the bottom surface of the mold and the plate is symmetrical with the axis corresponding to the optical axis of the lens to be molded. In the case of a large aperture, the shape asymmetry may be affected. However, when the lens has a small diameter, there is no problem even with the simple groove 16.

  In the above embodiment, the cooling rate is set to 1 ° C./second, but good molding can be performed as long as it is 0.5 ° C./second or more and 2 ° C./second or less. When the cooling rate is slower than 0.5 ° C./second, the cycle time becomes longer than necessary, and when it is faster than 2 ° C./second, the glass material is rapidly cooled, resulting in a decrease in transfer accuracy. Problems arise. Therefore, the materials of the chips 14 and 15 to be inserted into the plates 9a and 3a used in the first cooling step (step 3) so that the cooling rate falls within the range of 0.5 ° C./second or more and 2 ° C./second or less. And the contact area between the chips 14 and 15 and the mold is set.

  Further, in the case where the chips 14 and 15 are made of a material having a thermal conductivity higher than 30 W / (m · K), the glass material is rapidly cooled, which causes a problem that the transfer accuracy is lowered.

It is a front view of the shaping | molding apparatus used for embodiment of this invention. 2 is a perspective view of a plate according to Embodiment 1. FIG. 2 is a cross-sectional view of a plate according to Embodiment 1. FIG. (A) And (b) is a characteristic view which shows a transfer precision. 6 is a perspective view of a plate according to Embodiment 2. FIG.

Explanation of symbols

1 Cylinder 3, 3a Upper plate 6 Sleeve 7 Glass material 8 Lower mold 9, 9a Lower plate 12 Heater 14, 15 Tip

Claims (6)

In an optical element molding apparatus that molds an optical element material with a pair of molding dies into an optical element,
A pair of molds for pressing the heat-softened optical element material;
A pair of plates, each having a heater and having a material having a thermal conductivity of 30 W / (m · K) or less, which is in contact with the pair of molds when the pressed optical element material is cooled;
An optical element molding apparatus comprising: In an optical element molding apparatus that molds an optical element material with a pair of molding dies into an optical element,
A pair of molds for pressing the heat-softened optical element material;
A pair of plates provided with a heater and having a smaller area than the entire area of the bottom surface, each of which is in contact with the bottom surface of the pair of molds when cooling the pressed optical element material;
An optical element molding apparatus comprising:   3. The optical element molding apparatus according to claim 1, wherein the portions in contact with the pair of molds are removable from the plate. 4. In an optical element molding method in which an optical element material is molded by a pair of molding dies into an optical element,
A pressing step of pressing with a pair of molds pressing the heat-softened optical element material;
A transfer step of transferring the pressed optical element material and the pair of molds to a cooling position;
A cooling step of cooling the pair of molds by a pair of plates provided with a heater whose material is in contact with the pair of molds, each having a thermal conductivity of 30 W / (m · K) or less;
An optical element molding method comprising: In an optical element molding method in which an optical element material is molded by a pair of molding dies into an optical element,
A pressing step of pressing with a pair of molds pressing the heat-softened optical element material;
A transfer step of transferring the pressed optical element material and the pair of molds to a cooling position;
A cooling step of cooling the pair of molds by a pair of plates provided with a heater in which the areas of the portions in contact with the bottom surfaces of the pair of molds are smaller than the entire area of the bottom surface;
An optical element molding method comprising:   6. The method of molding an optical element according to claim 4, wherein the portions in contact with the pair of molds are removable from the plate.

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