JP2007126314A - Mold for forming optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold capable of press-molding a high-precision optical element excellent in the precision of its optical axis. <P>SOLUTION: A forming surface 5a for transferring one side of the optical function surfaces is formed on the upper mold member 5 and a forming surface 6a for transferring the other side of the optical function surfaces is formed on the lower mold member 6. A drum mold is composed of one side of the split mold 1 and the other side of the split mold 2 and holds the forming surface 5a of the upper mold member 5 and the forming surface 6a of the lower mold member 6 so as to face each other and move freely toward and apart. Between the reference surface 1a of one side of the split drum mold 1 and the coupling part 1b, an adjustable part 1c having a lowered rigidity compared with the other parts and an elastic deformability is provided. Similarly, an adjustable part 2c is provided between the reference surface 2a of the other side of the split drum mold 2 and the coupling part 2b. One side of the split drum mold 1 and the other side of the split drum mold 2 are coupled at the coupling parts 1b and 2b to leave the space S of a specified dimension. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mold for molding an optical element for press-molding an optical element by heating and softening a glass material.

  A molding die for press-molding an optical element by heating and softening a glass material includes an upper mold member and a lower mold member, and a body mold that holds the upper mold member and the lower mold member so as to approach and separate from each other. I have.

  For example, when a lens having optical functional surfaces on both sides is press-molded, it is necessary to prevent relative deviation or inclination between the optical axis of one optical functional surface and the optical axis of the other optical functional surface. is there.

  However, in the mold for molding optical elements, the size of the gap between the upper mold member and the lower mold member and the body mold that holds them close to and away from each other changes due to thermal expansion caused by temperature distribution during heating and cooling. To do. For this reason, even if the optical axis accuracy of the upper mold member and the lower mold member and the body mold is adjusted at room temperature, the optical axis accuracy deteriorates during press molding. Therefore, an optical element molding apparatus (see Patent Document 1) as shown in FIGS. 9 and 10 that can adjust the optical axis during press molding has been proposed.

In this optical element molding apparatus, as shown in FIGS. 9 and 10, the optical function is adjusted between the optical function surface 101a of the upper mold member 101 and the optical function surface 102a of the lower mold member 102 with the optical axis adjusted. After placing the glass material, each driving means 106 and 108 is activated to perform press molding. During this press molding, the optical axes of both optical functional surfaces 101a and 102a are adjusted again by the optical axis adjusting means. The optical axis adjusting means includes a pair of pressing members 111 and 112 that press the upper mold member 101 and the lower mold member 102 in a direction intersecting with the optical axis, and each driving means for the pressing members 111 and 112. 114 and 115 are activated so that the optical axis can be adjusted again.
Japanese Patent Laid-Open No. 11-157854

  However, the optical element molding apparatus disclosed in Patent Document 1 requires a drive device for operating the optical axis adjusting means, resulting in an increase in cost and size of the apparatus. In addition, there is an unsolved problem that not only the molding die but also the surrounding of the atmosphere at the time of molding around the drive unit of the optical axis adjusting means is not perfect, and it tends to cause a temperature disturbance.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and provides a high-precision optical element having excellent optical axis accuracy without providing a drive device for driving the optical axis adjusting means. An object of the present invention is to provide a mold for molding an optical element that can be press-molded.

  In order to achieve the above object, an optical element molding die according to the present invention includes an upper mold member having a molding surface for transferring an optical functional surface and a lower mold member having a molding surface for transferring the optical functional surface. And a barrel mold having a holding portion that guides the upper mold member and the lower mold member with the molding surfaces facing each other so as to approach and separate from each other, and heat and soften the glass material with the upper mold member In an optical element molding die that is placed between the lower die member and press-molded, the barrel die is provided with at least two divided barrel dies connected to both side ends of the holding portions of each divided barrel die. The coupling portion is coupled by a fastening member, and has an adjusting means for adjusting a tightening force of the holding portion against the upper mold member and the lower mold member.

  Since the present invention is configured as described above, the following effects can be obtained.

  It can be adjusted by the adjusting means even during the press molding, with respect to the change in the clamping force caused by the dimensional difference between the body mold and the upper mold member and the lower mold member generated during the press molding. Thereby, with a relatively simple configuration without using a large-scale device, the tightening force of the upper die member and the lower die member by the barrel die is in an optimum state, that is, the gap size is 1-2 μm or zero, or It can be kept under a slight preload.

  Adjustment of the clamping force of the upper mold member and the lower mold member between the divided cylinder molds coupled to each other is always performed during molding. Therefore, the mold is damaged too much in the middle of the process, or the dimension of the gap becomes too large, and the optical axis of the molding surface of each of the upper mold member and the lower mold member does not shift, and the optical axis accuracy is excellent. An optical element can be obtained. Furthermore, it is easy to block the atmosphere around the molding die, the occurrence of temperature distribution in the molding die can be suppressed, and a more accurate optical element can be molded.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a mold for molding an optical element according to the first embodiment, wherein (a) is a schematic cross-sectional view taken along line BB in (b), and (b) is taken along line AA in (a). It is a model longitudinal cross-sectional view which follows.

  As shown in FIGS. 1A and 1B, a molding surface 5 a for transferring one optical function surface is formed on the lower end surface of the upper mold member 5, and an upper end surface of the lower mold member 6 is formed on the upper end surface. A molding surface 6a for transferring the other optical functional surface is formed.

  The body mold is composed of one divided body mold 1 and the other divided body mold 2, and approaches and separates in a state where the molding surface 5a of the upper mold member 5 and the molding surface 6a of the lower mold member 6 face each other. Hold freely. Further, a collar part 5 b is provided at the upper end of the upper mold member 5, and a collar part 6 b is provided at the lower end part of the lower mold member 6.

  One split body mold 1 has a reference surface 1a composed of a V-shaped surface that intersects at an angle of about 90 degrees, and a coupling portion 1b is connected to both ends of the reference surface 1a via an adjustment portion 1c. Has been. Similarly, the other split cylinder mold 2 has a reference surface 2a composed of V-shaped surfaces intersecting at an angle of about 90 degrees, and coupling portions 2b are connected to both ends of the reference surface 2a via adjustment portions 2c. It is connected continuously.

  One split cylinder mold 1 and the other split cylinder mold 2 are coupled by a fastening member such that the respective reference surfaces 1a and 2a are opposed to each other and an interval S having a predetermined dimension is generated at the coupling portions 1b and 2b. . The fastening member is a simple member in which a bolt 3 is fitted and inserted into a coaxial through hole provided in each of the coupling portions 1 b and 2 b and a lock nut 4 is screwed to the tip of the bolt 3.

  Each of the reference surfaces 1a and 2a has a flatness within 1 μm, and the upper die member 5 and the lower die member 6 are brought close to each other through a highly accurate and heat-resistant bearing 11 having a roller 9 and a retainer 10. And guides freely.

  Between the reference surface 1a and the coupling portion 1b of one split barrel mold 1, there is provided an adjustment portion 1c that generates elastic deformation due to bending with a reduced cross-sectional area and reduced rigidity compared to other portions. ing. Between the reference surface 2a of the other split cylinder mold 2 and the coupling portion 2b, there is provided an adjusting portion 2c that generates deformation due to bending with a reduced cross-sectional area and reduced rigidity compared to other portions. Yes. Both split body molds 1 and 2 are joined in a state where the upper mold member 5 and the lower mold member 6 are sandwiched with a desired tightening force via a roller 9 in an initial state.

  By the way, during press molding, since heating and cooling are repeatedly performed, the dimensional relationship between the two split cylinder molds 1, 2, the roller 9, the upper mold member 5, the lower mold member 6, and the like differs from the initial state. Usually, since the thermal expansion coefficients of the roller 9 and the two split cylinder molds 1 and 2 are larger than the thermal expansion coefficients of the upper mold member 5 and the lower mold member 6, the size of the latter is larger than that of the former during heating.

Further, in the case where the molding die E ₁ is heated from inside or outside the split cylinder molds 1 and 2, the split cylinder molds 1 and 2 are first heated first, and then the The mold member 5 and the lower mold member 6 are heated. For this reason, a temperature difference occurs between the two, and in this case also, the two split barrel molds 1 and 2 have larger dimensions, and the optical axis is deteriorated due to an increase in the dimension of the gap between the upper mold member 5 and the lower mold member 6. appear.

  Further, during cooling, the size of the gap due to the difference in the amount of thermal expansion decreases, but both the split barrel molds 1 and 2 on the outside are easy to cool first, and the upper mold member 5 and the lower mold member 6 Cooling is delayed. As a result, the dimensions of both split body molds 1 and 2 are reduced, and the roller 9, the upper mold member 5, and the lower mold member 6 are tightened. In some cases, the upper mold member 5, the lower mold member 6, The roller 9 may be plastically deformed or damaged.

  Therefore, the rigidity of the adjusting portions 1c and 2c and the initial tightening force are determined so that these problems do not occur. Specifically, a holding force F <b> 1 for holding the upper mold member 5 and the lower mold member 6 at the time of pressing is necessary. Further, in the above example, the clamping force by the two split cylinder dies 1 and 2 is more relaxed at the time of pressing than in the initial state. Therefore, the initial clamping force FA = F1 + F2 is required to which the reduced force F2 is added.

  Moreover, since it tightens on the contrary at the time of cooling, the force F3 of the increase is added and it becomes the tightening force FB = F1 + F2 + F3 at the time of cooling.

Considering the plastic deformation of the molding die E ₁ and the roller 9, it is desirable to make it as small as possible except for the holding force F 1 for holding during pressing. However, since F2 and F3 depend on the rigidity of the adjusting portions 1c and 2c, the adjusting portions 1c and 2c have a small spring constant (a change in force with respect to the displacement is small) while maintaining strength against the holding force F1. It is desirable to design.

  Incidentally, the amount of change in the mold dimensions during press molding may be several μm to several tens of μm, although it depends on the material and size of the mold and the heating / cooling method.

  According to this embodiment, even when there is a dimensional difference due to a difference in material or temperature between the split cylinder molds 1, 2, roller 9, upper mold member 5, and lower mold member 6 during heating / cooling, adjustment is possible. The parts 1c and 2c are elastically deformed to absorb these dimensional differences. At the time of pressing, the upper die member 5 and the lower die member 6 are held by the split cylinder dies 1 and 2 with an appropriate tightening force. In addition, even during cooling, it is possible to hold the split cylinder molds 1 and 2 and the rollers 9 without generating an excessive tightening force that causes plastic deformation. That is, in the present embodiment, the adjusting portions 1c and 2c correspond to adjusting means for adjusting the tightening force of the upper die member 5 and the lower die member 6 of the holding portion.

Next, details of press molding using the optical element molding die E _{1 according} to the first embodiment will be described.

In the press molding machine, a glass material W is disposed between the molding surface 5 a of the upper mold member 5 and the molding surface 6 a of the lower mold member 6. The molding die E ₁ is placed in a chamber filled with an inert gas, the atmosphere of which is cut off from the outside air. Further, a press shaft for applying a pressing force (not shown) is disposed above the upper die member 5 and is connected to an actuator for controlling the pressing force and position.

Around the mold E ₁ , there are provided an upper mold member 5, a lower mold member 6, a heater for heating the glass material W, and an inert gas ejection means (not shown) for cooling. . Further, a cylindrical reflector for increasing temperature uniformity is disposed around the body mold, and the upper mold member 5 and the lower mold member 6 are each provided with temperature detection means to perform temperature control. It is like that.

In the mold E ₁ before heating, the two split cylinder dies 1 and 2 are joined at the joining portions 1b and 2b by bending the adjusting portions 1c and 2c. For this reason, the reference surfaces 1 a and 2 a of the two split cylinder dies 1 and 2 hold the side surfaces of the upper die member 5 and the lower die member 6 through the rollers 9 with a predetermined initial fastening force FA. Then, heating of the upper mold member 5, the lower mold member 6, and the glass material W is started by the heaters disposed around. When the upper mold member 5, the lower mold member 6 and the glass material W reach a temperature at which pressing is possible, a pressing force is applied to the upper mold member 5 by a press shaft (not shown), and pressing is started. At this time, the two split cylinder dies 1 and 2 are heated prior to the upper mold member 5 and the lower mold member 6. Furthermore, since the rollers 9 are interposed between the reference surfaces 1a and 2a of the split cylinder molds 1 and 2 and the upper mold member 5 and the lower mold member 6 and the heat conduction is not so good, the split cylinder mold 1 The temperature of 2 is higher. In addition, the thermal expansion coefficient of the two split barrel molds 1 and 2 is larger than that of the upper mold member 5 and the lower mold member 6. For this reason, since the dimensions of the two split barrel dies 1 and 2 are larger than the outer peripheries of the upper die member 5 and the lower die member 6, the bending of the adjusting portion 1c is reduced, and the holding force F1 at this point Compared to the initial initial tightening force FA, the force is reduced by a reduced force F2. However, since the initial initial fastening force FA is set so that the holding force F1 is large enough to hold the upper die member 5 and the lower die member 6 at the time of pressing, there is no problem.

When the glass material W is deformed by a predetermined amount, the pressing force is once released, and then cooling by the inert gas ejection means arranged around the molding die E ₁ is started.

  Then, when it is cooled to a predetermined temperature, a pressing force is again applied to the upper mold member 5 by the press shaft so that the surface shape of the molded product does not collapse, and when the cooling is continued and the predetermined temperature is reached, the pressing pressure is applied. Is released.

At this point, the molding die E ₁ may be cooled from the outer peripheral side, the temperature difference between the inside and outside is reversed, and the upper die member 5 and the lower die member 6 are more than the two split barrel die 1 and 2. Becomes a high temperature state. For this reason, the dimensions of the two split cylinder dies 1 and 2 are tightened compared to the outer peripheries of the upper mold member 5 and the lower mold member 6, and the deflection of the adjusting portions 1c and 2c is increased. The force F3 is higher than the initial initial fastening force FA. However, upon cooling the clamping force FB or plastically deform the member constituting the mold E _1, adjuster 1c to be lower than the force as or to destroy, by setting the shape of 2c No problem.

And further subjected to cooling, when reaching to a predetermined temperature, the cooling is terminated, remove the upper mold member 5 from the mold E _1, demolded, and ends the molding.

  Molding is repeatedly performed by the series of steps as described above. Here, a lens used for the camera will be described in more detail as an example.

  Heavy crown glass (refractive index 1.58, Abbe number 59.4, transition point 506 ° C) is used for the glass material, both surfaces are convex aspherical surfaces (approx. R9mm), outer diameter φ7mm, center wall thickness 3.0mm, outer circumference A convex lens having a thickness of 1.6 mm is molded.

First, the upper mold member 5, heated to a temperature of the lower mold member 6 and the glass material W is 580 ° C. (10 ^9.0 poises equivalent), and waits. After that, press molding is performed by applying a pressing force of 2450 N (Newton) by the upper mold member 5, and the pressing process by the upper mold member 5 is canceled when the thickness of 20 to 30 μm remains up to 3.0 mm. finish.

Next, when cooling was started and the temperature reached 560 ° C. (equivalent to 10 ^9.8 poise), the upper mold member 5 applied a pressing force of 1950 N again to the molded product to continue cooling and reached 490 ° C. (equivalent to 10 ^13.5 poise). At that time, the pressing force of the upper mold member 5 is released. At this point, the thickness of the molded product is approximately 3.0 mm.

And after the completion of the cooling, remove the upper mold 5 from the mold E _1, taken out of the molded article.

  At this time, the holding force F1 of the body mold required at the time of pressing is set to 250 N, and the relative dimensions of the body mold holding portion at that time (the outer diameters of the upper mold member 5 and the lower mold member 6 in consideration of the dimensions of the roller 9) The amount of increase from the initial value with respect to (dimension) was 8 μm. Similarly, the amount of decrease from the initial value at the time of cooling is set to 2 μm, and the adjusting portions 1c of the split cylinder molds 1 and 2 are set so that the cooling tightening force FB at this time is 350 N (initial tightening force FA = 330 N). The shape of 2c was designed.

  Although the above press molding was repeated, there was no problem of deformation or breakage of the mold. When the molded product was evaluated, the parallel decentering of the optical axis between the two surfaces of the molding surface 5a which is the optical function surface of the upper mold member 5 and the molding surface 6a which is the optical function surface of the lower mold member 6 was 2 μm or less. . In addition, the inclination was 20 seconds or less, and the partial displacement of the surface shape was 0.1 μm or less, and a lens that can be said to be highly accurate among camera lenses could be obtained.

In this way, by using the molding die E ₁ having a structure capable of adjusting the optical axes of the molding surfaces 5a and 6a, which are optical function surfaces of the upper mold member 5 and the lower mold member 6, at all times during press molding, the optical axis An extremely high precision optical element including the precision could be obtained.

  Next, an optical element molding die according to the second embodiment will be described with reference to FIG. Except for a part of the configuration of the molding die, the configuration is the same as that of the molding die for the optical element according to the first embodiment.

  The body mold is composed of two members, one divided body mold 21 and the other divided body mold 22. One split barrel die 21 has a reference surface 21a composed of V-shaped surfaces intersecting at an angle of approximately 90 degrees, and flange-like coupling portions 22b are continuously provided at both ends of the reference surface 21a. The other split barrel die 22 has a reference surface 22a formed of a V-shaped surface that intersects at an angle of approximately 90 degrees, and flange-like coupling portions 22b are continuously provided at both ends of the reference surface 22a. One split barrel die 21 and the other split barrel die 22 are coupled by a fastening member such that a predetermined dimension interval S is generated in the coupling portions 21b and 22b with the respective reference surfaces 21a and 22a facing each other. Yes.

  The fastening member includes a bolt 23 having a compression spring 25 interposed on the head side in a coaxial through hole provided in each of the coupling portions 21b and 22b, and a lock nut 24 is screwed onto the tip of the bolt 23. Are connected. As a result, the roller 9, the upper mold member 5 and the lower mold member 6 are clamped with a predetermined tightening force by the elastic force of the compression spring 25 set to the initial length by adjusting the screwing position of the lock nut 24, and the elasticity Have concluded.

  In other words, the adjusting means for adjusting the tightening force according to the present embodiment performs the absorption action of the dimensional difference between the molds caused by the elastic deformation of the adjusting portion 2c in the first embodiment by replacing the compression spring 25. ing.

Both split barrel dies 21 and 22 hold the side surfaces of the upper die member 5 and the lower die member 6 with a predetermined clamping force via the rollers 9 by the spring action (restoring force) of the compression spring 25. Regarding the force required for the compression spring 25, the optical element molding die E ₁ according to the first embodiment and the holding force F1, the initial tightening force FA required during pressing, and the cooling tightening force FB generated during cooling are the same. The same is required.

  The camera lens was molded under the same conditions as in the first embodiment, and the spring constant of the compression spring 25 was designed to be the same as the rigidity of the adjusting portion 2c of the first embodiment. There was no problem of deformation or breakage of the mold, and an extremely high-precision molded product including the optical axis accuracy could be obtained as in the first embodiment.

  Subsequently, a modified example of the adjusting means in the second embodiment will be described. In the adjusting means of this modification, instead of the compression spring 25 shown in FIG. 2 described above, a thermal expansion member (not shown) having a thermal expansion coefficient larger than that of the split barrel dies 21 and 22 is used. Between the coupling part and the coupling part. For example, the thermal expansion member may be a cylindrical body having an inner diameter in which a bolt can be loosely fitted.

  The thermal expansion member may be interposed on the lock nut side of the bolt or on both the head side and the lock nut side of the bolt.

  That is, the adjusting means in the present modification is such that the thermal expansion coefficient is constantly energized from the outside of at least one of the split cylinder molds so that the split cylinder molds clamp the upper mold member and the lower mold member. The thermal expansion member is larger than the thermal expansion coefficient of the mold.

  According to this modification, during heating, the length of the thermal expansion member is extended by thermal expansion, and the upper die member and the lower die member are always urged from the outer side of at least one of the split barrel molds. To do. As a result, the same effects as those of the second embodiment shown in FIG.

  Next, an optical element molding die according to a third embodiment will be described. In FIG. 3, except for a part of the configuration of the molding die, it is the same as the first embodiment, so the same parts are denoted by the same reference numerals, description thereof is omitted, and different parts will be described.

  It has one divided cylinder mold 31 and the other divided cylinder mold 32, and consists of a reference surface 31a made of a V-shaped surface of one divided cylinder mold 31 and a V-shaped surface of the other divided cylinder mold 32. The upper die member 5 and the lower die member 6 are positioned and held near the center of the reference surface 32a. The difference from the first embodiment is that a part of the reference surface 31a of one divided cylinder mold 31 and a part of the reference surface 32a of the other divided cylinder mold 32 directly guide the upper mold member 5 and the lower mold member 6. Yes. In addition, the fastening member that couples the one split cylinder mold 31 and the other split cylinder mold 32 so as to generate the interval S is provided with a thermal expansion member 34 interposed between the respective coupling portions 31b and 32b, and by bolts 33. It is fixed from both sides.

  The thermal expansion member 34 is made of a material having a predetermined thermal expansion coefficient, so that the upper mold member 5 and the lower mold member 6 can slide with high precision at least during pressing. For this reason, the length of the thermal expansion member 34 is adjusted so that the dimension of the gap between the reference surfaces 31a, 32a of the split cylinder dies 31, 32 and the side surfaces of the upper mold member 5 and the lower mold member 6 is 1 to 2 μm. Is done. And it is fixed by being sandwiched between the coupling part 31 b of one split cylinder mold 31 and the coupling part 32 b of the other split cylinder mold 32.

  Here, when considering actual molding, the thermal expansion coefficients of one divided cylinder mold 31 and the other divided cylinder mold 32 are usually larger than the thermal expansion coefficients of the upper mold member 5 and the lower mold member 6. . For this reason, the size of the latter is larger than that of the former during heating. According to the conventional method, the size of the gap between the body mold and the upper mold member 5 and the lower mold member 6 is enlarged, thereby causing a deviation of each molding surface, and the optical axis accuracy of the optical element to be molded. Will worsen.

  Furthermore, in the case where heating is performed from the inside or the outer peripheral side of the body mold, the body mold is heated first, and the upper mold member 5 and the lower mold member 6 are heated later. For this reason, a temperature difference occurs between the two, and in this case as well, the size of the body mold is larger, and the optical axis is deteriorated due to the increase in the size of the gap.

During cooling, the size of the gap due to the difference in thermal expansion decreases. However, if the outer die is cooled first and the cooling of the upper die member 5 and the lower die member 6 is delayed, both of them are reversed. In some cases, the size of the split barrel molds 31 and 32 is smaller. As a result, the upper mold member 5 and the lower mold member 6 are strongly tightened, and in some cases, plastic deformation or breakage of the molding die E ₃ may occur.

  In the third embodiment, the bearing (roller) is not interposed between the two split body molds, the upper mold member, and the lower mold member, so that compared with the first and second embodiments, the heating and cooling are not performed. The temperature difference is reduced.

  Therefore, the thermal expansion coefficient of the thermal expansion member 34 and the dimensions of the gaps between the reference surfaces 31a and 32a of the initial split cylinder molds 31 and 32 and the side surfaces of the upper mold member 5 and the lower mold member 6 cause these problems. Specifically, the following two methods are taken.

  One is that, as described above, the dimensions of one of the divided cylinder molds 31 and the other divided cylinder mold 32 at the time of pressing are wider than the outer diameters of the upper mold member 5 and the lower mold member 6. For this reason, the thermal expansion member 34 selects a material having a thermal expansion coefficient that cancels out the spread smaller than the thermal expansion coefficient of both split cylinder types. In that case, since the dimensions of the split barrel molds 31 and 32 tend to be tightened during cooling, the cooling of the thermal expansion member 34 is delayed by, for example, preventing the thermal expansion member 34 from being directly cooled. A gap can be secured.

  The other is that the coefficient of thermal expansion of the thermal expansion member 34 is further reduced, and the initial gap size is kept large, and the size of the gap is reduced to 1 to 2 μm during pressing. Furthermore, a gap having an appropriate size can be ensured by offsetting the amount of increase in the size of the gap due to the difference in thermal expansion and the amount of decrease in the size of the gap due to the temperature difference during cooling.

  Incidentally, although the amount of change in the mold dimensions during molding depends on the material and size of the mold and the heating / cooling method, it may be assumed to be several μm to several tens of μm.

  According to the present embodiment, due to the action of the thermal expansion member 34 (including temperature adjustment of the thermal expansion member 34), between the split barrel dies 31, 32, the upper mold member 5 and the lower mold member 6 during heating and cooling. Even if there is a difference in material or temperature, a dimensional difference between them can be absorbed. For this reason, at least during pressing, cooling, and mold opening / closing, the dimensions of the gaps between the holding portions of the split barrel molds 31 and 32 and the upper mold member 5 and the lower mold member 6 can be always maintained in an appropriate state. It becomes possible.

Next, details of molding using the molding die E ₃ will be described.

  The apparatus to be used is the same as that of the first embodiment, but in the molding die before heating, the reference surfaces 31a, 32a of both split cylinder dies 31, 32 and the side surfaces of the upper die member 5 and the lower die member 6 are used. The lengths of the thermal expansion members 34 and 35 are set so that the dimension of the gap is, for example, 4 to 5 μm, and the two split cylinder dies 31 and 32 are combined.

Then, heating of the molding die E ₃ and the glass material W is started by the heater disposed around the body mold, and when the upper mold member 5, the lower mold member 6 and the glass material W reach a pressable temperature. Then, pressing force is applied to the upper mold member 5 by the press shaft to start pressing. At this time, both split cylinder dies 31 and 32 are heated before the upper mold member 5 and the lower mold member 6, and the gap between the split cylinder dies 31 and 32 and the upper mold member 5 and the lower mold member 6 is further increased. Since there is a gap and the heat conduction is not so good, the temperature of both split cylinder dies 31 and 32 is higher. Further, the thermal expansion coefficients of both split body dies 31 and 32 are larger than those of the upper die member 5 and the lower die member 6. For this reason, there is a tendency that the dimensions of the holding portions of both split body dies 31 and 32 are wider than the outer peripheral surfaces of the upper die member 5 and the lower die member 6. However, here, the thermal expansion coefficient of the thermal expansion member 34 between the split cylinder dies 31 and 32 is set small. As a result, when the temperature at which pressing is possible is reached, the size of the gap is reduced to 1 to 2 μm.

  When the glass material W is deformed by a predetermined press amount, the pressing force is once released, and then cooling is started by the inert gas ejection means arranged around the body mold.

  And when it cools to predetermined temperature, pressing force is again applied to the upper mold | type member 5 with a press shaft so that the surface shape of a molded product may not collapse, and when cooling continues and it reaches predetermined temperature, pressing force Is released.

When this point, the thermal expansion coefficient of the both split barrel die 31, 32 is greater than the upper mold 5 and lower mold 6, by the mold E ₃ is cooled from the outer peripheral side, out of the temperature The difference is reversed. Therefore, the temperature of the upper mold member 5 and the lower mold member 6 is higher than that of the body mold, and the size of the gap tends to decrease. However, since the thermal expansion coefficient of the thermal expansion member 34 is set to be small here, the dimensional change of the gap is offset and cooling is performed while maintaining 1 to 2 μm.

And further subjected to cooling, when reaching to a predetermined temperature, the cooling is terminated, remove the upper mold member 5 from the mold E _3, demolded, and ends the molding.

When the cooling is finished and the temperature difference between the inside and outside of the molding die E ₃ is eliminated, the size of the gap returns to the initial setting of 4 to 5 μm.

  Here, if it is difficult to adjust the size of the gap only by setting the thermal expansion coefficient of the thermal expansion members 34 and 35, for example, the cooling to the thermal expansion members 34 and 35 is limited at the time of cooling. It is also possible to adjust the size of the gap auxiliary.

Molding is repeated by the series of steps as described above. Here, as in the first embodiment, a description will be given taking a camera lens as an example. Detailed conditions and the like are the same as those in the first embodiment, and are omitted. However, the molds used at this time were all super hard materials. The thermal expansion coefficient is 5.3 × 10 ⁻⁶ / K for both split barrel dies 31 and 32, the upper mold member 5 and the lower mold member 6 are all 4.8 × 10 ⁻⁶ / K, and the thermal expansion member 34 is 4 0.0 × 10 ⁻⁶ / K was selected and used.

  As a result, the dimensional adjustment of the gap is good, and there is no problem of deformation or breakage of the mold. When the molded product is evaluated, the parallel decentration of the optical axis between both optical functional surfaces is 3 μm or less, The inclination was 30 seconds or less, and a molded product with excellent optical axis accuracy could be obtained as in the first example.

An optical element molding die according to the fourth embodiment will be described. As shown in FIG. 4 and FIG. 5, the molding die E ₄ is configured such that the body mold is composed of one divided body mold 41 and the other divided body mold 42. The molding surface 55a for transferring one optical function surface of the upper mold member 55 and the molding surface 56a for transferring the other optical function surface of the lower mold member 56 have a convex meniscus lens shape.

  The optical element, which is a molded product, has a convex meniscus lens shape on the optical functional surface, and is obtained by press molding heavy crown glass having a transition point temperature of 506 ° C., a deflection point temperature of 538 ° C., and a softening point temperature of 607 ° C. is there.

  The body mold is composed of one divided body mold 41 and the other divided body mold 42, and approaches and separates with the molding surface 55a of the upper mold member 55 and the molding surface 56a of the lower mold member 56 facing each other. Hold freely.

  One split cylinder 41 has a V-shaped reference surface 41a that intersects at an angle of about 60 degrees, and coupling portions 41b are connected to both ends of the reference surface 41a. The other split cylinder die 42 has a flat reference surface 42a, and coupling portions 42b are connected to both ends of the reference surface 42a.

  The one split cylinder mold 41 and the other split cylinder mold 42 are coupled to each other by fastening members so that the respective reference surfaces 41a and 42a face each other and an interval of a predetermined dimension is generated at the coupling portions 41b and 42b. The fastening member includes a bolt 43 having a compression spring 25 interposed on the head side in a coaxial through hole provided in the coupling portions 41b and 42b. It is fastened so that the dimensions can be changed.

  The reference surface 41a of one divided cylinder mold 41 and the reference surface 42a of the other divided cylinder mold 42 are each finished with a flatness within 1 μm.

  An opening for handling a glass material which is a molding material and a molded product is provided in a cylinder die composed of both split cylinder dies 41 and 42. 4 and 5, the two split body dies 41 and 42 are fastened at a plurality of locations with an axial force of about 2KN by bolts 43 and nuts 44 each having a compressed spring 45. The fastening portion is provided with an interval of about 0.1 mm at room temperature.

  In the fastened state, the upper mold member 55, the lower mold member 56, the split cylinder molds 41 and 42, and the cylindrical bearing member 49 are free of backlash and are always in contact with each other.

The upper die member 55, the lower die member 56, the split cylinder dies 41 and 42, and the cylindrical bearing member 49 are each tungsten carbide carbide material and have a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / K. is there. These materials are not limited to the above, and other ceramics such as silicon nitride, tungsten superpolymerized gold, or the like may be used in consideration of linear expansion coefficient, high temperature durability, compressive strength, and the like.

Although not shown, heating heaters are respectively provided in the split cylinder dies 41 and 42, the upper die member 55, and the lower die member 56, and the temperature can be controlled independently. The split cylinder dies 41 and 42, the upper die member 55, and the lower die member 56 are each provided with an introduction pipe for spraying N ₂ as a cooling means after molding.

Next, an optical element molding method will be described using the optical element molding die E ₄ having the above structure.

  First, a glass material is introduced into a cavity, which is a molding mold inner space, through the openings of both split cylinder dies 41 and 42 while being adsorbed by a handling device (not shown), and molding of the lower mold member 56 is performed. It is placed on the surface 56a. At this time, the temperature of the glass material is 506 ° C. or less, which is the glass transition temperature.

  Next, in a state where the glass material heating device (not shown) is maintained at a temperature equal to or higher than the glass material temperature at the time of introduction (800 ° C. which is equal to or higher than the softening point of the glass material in this embodiment), both split cylinder dies 41 and 42 are used. The glass material side is approached from the opening of and heated. At the same time, the upper mold member 55 and the lower mold member 56 are heated to a temperature optimal for molding by a heater (not shown) in one of the split cylinder mold 41, the upper mold member 55, and the lower mold member 56. For example, the glass is heated to a temperature at which log η = 8 to 10 (580 ° C. in this embodiment).

  When the temperature of the glass material and the temperature of the upper mold member 55 and the lower mold member 56 are suitable for molding, for example, the glass viscosity is logη = 8 to 12 (580 ° C. in this embodiment), a heating device (not shown) is installed. Retract from the trunk member opening. Next, the lower mold member 56 is raised using a linear drive means (not shown), for example, a piston / cylinder mechanism using hydraulic pressure or atmospheric pressure, or an electric cylinder mechanism, and the glass material is press-molded at 30 MPa. At this time, there is a temperature difference between the split cylinder dies 41 and 42, the cylindrical bearing member 49, the upper die member 55, and the lower die member 56. In particular, since the cylindrical bearing member 49 has no heating means, the temperature rises only to a temperature lower than that of the upper mold member 55, the lower mold member 56, and the two split cylinder dies 41 and 42. In this state, if the fastening member fastened by the bolts 43 and nuts 44 (hereinafter referred to as “fastening members”) provided with the split cylinder dies 41 and 42 at the normal temperature is not elastically deformed, the upper die member 55. In addition, the lower mold member 56, the two split cylinder molds 41 and 42, and the cylindrical bearing member 49 are loosely caused by the difference in thermal expansion. However, when the fastening member is elastically deformed, the backlash between the split body dies 41 and 42 and the upper die member 55 and the lower die member 56 is absorbed by the elastically deforming spring 45 of the fastening member and is always in contact. It becomes a state.

  And after press-molding a glass raw material to arbitrary shapes at shaping | molding temperature, a pressing force is reduced to 1 Mpa and it enters into a cooling process. During this cooling step, secondary press molding is performed again with a pressing force of 30 MPa near the glass transition point (540 to 490 ° C. in this embodiment) in order to improve the surface accuracy of the molded product. At this time, a temperature difference different from that during press molding occurs between the split cylinder dies 41 and 42, the cylindrical bearing member 49, the upper die member 55, and the lower die member 56. In particular, since the cylindrical bearing member 49 has a small contact area with the split cylinder dies 41 and 42, the upper die member 55, and the lower die member 56, a temperature drop due to heat conduction hardly occurs. Therefore, the temperature of the cylindrical bearing member 49 is higher than that of the upper mold member 55, the lower mold member 56, and the both split cylinder molds 41 and 42. In this state, the upper mold member 55, the lower mold member 56, the two divided cylinder molds 41 and 42, and the cylindrical bearing member, unless the fastening members that fasten the divided cylinder molds 41 and 42 with the fastening members at room temperature are elastically deformed. There is a possibility that each member is damaged due to a difference in thermal expansion amount at 49. However, when the fastening member is elastically deformed, the part of the fastening member 41, 42, the upper die member 55, and the lower die member 56 due to the temperature difference of the cylindrical bearing member 49 is tightly fitted. Absorbed by elastically deforming spring parts. Therefore, each member is not damaged and is always in contact.

  Thereafter, after the secondary press is finished, the molded product is taken out from the cavity by vacuum suction from the openings of both split cylinder dies 41 and 42 by a handling device (not shown).

  The molded product obtained by this method had a parallel eccentricity of 2 μm or less, an optical axis tilt of 20 seconds or less, and was able to satisfy the standard value for surface accuracy. In addition, among the lenses of digital compact cameras, this is a class that requires high optical axis accuracy, and a lens with good surface accuracy could be obtained.

  In this way, the two split barrel dies 41 and 42 are fastened and fixed by the fastening member including the elastic body that is elastically deformed with respect to the force in the range of 10N or more and 10000N or less applied in the direction opposite to the fastening force. As a result, the backlash and tight fitting state due to the temperature difference between the upper die member 55, the lower die member 56, the split cylinder dies 41 and 42, and the cylindrical bearing member 49 during press molding are absorbed. As a result, it is possible to slide the upper mold member and the lower mold member without backlash, and the molded product has a very high optical axis accuracy, and a molded product that satisfies the standard value of the surface accuracy can be obtained.

An optical element mold according to the fifth embodiment will be described. As shown in FIGS. 6 to 8, the molding die E ₅ is composed of a first split barrel die 61, a second split barrel die 62, and a third split barrel die 63. . A molding surface 75a for transferring one optical function surface of the upper mold member 75 and a molding surface 76a for transferring the other optical function surface of the lower mold member 76 have a convex meniscus lens shape.

  The optical element is obtained by press molding heavy crown glass having a transition point temperature of 506 ° C., a bending point temperature of 538 ° C., and a softening point temperature of 607 ° C.

  The body mold that sandwiches the upper mold member 75 and the lower mold member 76 so as to be able to approach and separate from each other includes a first divided cylinder mold 61, a second divided cylinder mold 62, and a third divided cylinder mold 63.

  As shown in FIG. 7, the lower mold member 76 is in point contact with one surface via a spherical bearing member 79. Further, as shown in FIG. 6, the upper die member 75 is in direct line contact with the reference surfaces 61a, 62a, 63a, and this surface is formed with a flatness of 1 μm or less.

  In addition, the opening part for handling the glass raw material which is a shaping | molding raw material, and a molded article is provided in the trunk | drum which consists of the 1st-3rd division | segmentation cylinder type | molds 61-63.

  And the 1st-3rd division | segmentation trunk | drum 61-63 is an axial force in nine places as shown in FIGS. 6-8 with the fastening member which consists of the volt | bolt 64 provided with the spring 65 which elastically deforms, and the nut 66. FIG. It is fastened with a combination of about 2KN and 120 degree rotational symmetry. The coupling portion is provided with an interval of about 0.1 mm at room temperature.

  In the fastened state, the upper mold member 75, the lower mold member 76, the first to third divided cylinder molds 61 to 63, and the spherical bearing member 79 are free of backlash and are always in contact with each other. As a result, the upper mold member 75 and the lower mold member 76 are slidable in the optical axis direction in which the molding material is press-molded in a state where there is no parallel decentering or tilting on the optical axis.

The upper mold member 75, the lower mold member 76, the first to third divided cylinder molds 61 to 63, and the spherical bearing member 79 are each made of a tungsten carbide cemented carbide material and have a thermal expansion coefficient of 5.0 × 10. ^-6 / K. However, these materials are not limited to those described above, and may be other ceramics such as silicon nitride, tungsten superpolymerized gold, or the like in consideration of linear expansion coefficient, high temperature durability, compressive strength, and the like.

  Although not shown in the figure, a heating heater is provided in each of the body mold including the first to third divided cylinder molds 61 to 63, the upper mold member 75, and the lower mold member 76, and independently controls the temperature. is doing.

Further, nitrogen gas (N ₂ ) is blown to the first to third divided barrel dies 61 to 63, the upper die member 75 and the lower die member 76 through the introduction pipe as cooling means after molding, respectively, during cooling. It has become.

Next, a molding die E ₅ for the optical element having the structure described above.
Will be used to explain the optical element molding method of the present invention.

  In a state where a glass material as a molding material is adsorbed by a handling device (not shown), the glass material is introduced into the cavity through the opening of the body mold and placed on the molding surface 76 a of the lower mold member 76. At this time, the temperature of the glass material is 506 ° C. or less, which is the glass transition temperature. Next, a glass material heating device (not shown) is brought closer to the upper side of the glass material than the opening of the body mold in a state where the glass material temperature is maintained at 800 ° C. which is equal to or higher than the glass material temperature at the time of charging. Heat. At the same time, a heater (not shown) in the body mold, the upper mold member 75 and the lower mold member 76 is used to form a temperature optimum for molding, for example, a temperature at which logη = 8-10 in terms of glass viscosity (580 in this embodiment). C.).

  When the temperature of the glass material, the temperature of the upper mold member 75 and the lower mold member 76 are suitable for molding, for example, the glass viscosity is logη = 8 to 12 (580 ° C. in this embodiment), a heating device (not shown) is installed. Retract from the trunk member opening. Next, the lower mold member 76 is raised using a driving means (not shown), for example, a piston / cylinder mechanism by hydraulic pressure or atmospheric pressure, or an electric cylinder mechanism, and the glass material is press-molded at 30 MPa. At this time, a temperature difference is generated between the body mold, the spherical bearing member 79, and the lower mold member 76. In particular, since the spherical bearing member 79 has no heating means, the temperature rises only to a temperature lower than that of the upper mold member 75, the lower mold member 76, and the first to third divided cylinder molds 61 to 63. In this state, if the spring member 65 of the fastening member that fastens the first to third divided barrel dies 61 to 63 by the fastening member at normal temperature does not elastically deform, the upper die member 75, the lower die member 76, the trunk die, and The spherical bearing member 79 is loose due to a difference in thermal expansion. However, when the spring member 65 is elastically deformed, the backlash between the first to third divided barrel dies 61 to 63 and the upper die member 75 and the lower die member 76 due to the temperature difference of the spherical bearing member 79 is reduced. It is absorbed by the member 65 and is always in contact.

  And after press-molding a glass raw material to arbitrary shapes at shaping | molding temperature, a press pressure is reduced to 3 Mpa and it enters into a cooling process. During this cooling step, secondary press molding is performed again at a pressure of 30 MPa in the vicinity of the glass transition point, in this embodiment, between 540 ° C. and 490 ° C. in order to improve the surface accuracy of the molded product. At this time, a temperature difference different from that during press molding occurs between the first to third divided barrel dies 61 to 63, the spherical bearing member 79, the upper die member 75, and the lower die member 76. In particular, since the spherical bearing member 79 has a small contact area with the first to third divided cylinder dies 61 to 63, the upper die member 75, and the lower die member 76, a temperature drop due to heat conduction hardly occurs. Therefore, the temperature is higher than that of the upper mold member 75, the lower mold member 76, and the first to third divided cylinder molds 61 to 63. In this state, the fastening member fastened by the spring member 65, the bolt 64, and the nut 66 (hereinafter referred to as “fastening member”) that elastically deforms the first to third split cylinder dies 61 to 63 at room temperature is elastically deformed. Otherwise, the upper mold member 75 and the lower mold member 76, the first to third divided cylinder molds 61 to 63, and the bearing member 79 may be in a tight fit state due to a difference in thermal expansion and may be damaged. is there. However, when the fastening member is elastically deformed, the first to third divided barrel dies 61 to 63, the upper die member 75, and the lower die member 76 are tightly fitted due to the temperature difference of the spherical bearing member 79. The extra portion is absorbed by the spring 65 that elastically deforms the fastening member. For this reason, each member will not be damaged but will always be in contact.

  Thereafter, after the secondary press is finished, the lower mold member 76 is lowered, and the molded product is vacuum-sucked from the openings of the first to third divided cylinder molds 61 to 63 by a handling device (not shown) and taken out from the cavity. .

  The obtained molded product has a parallel eccentricity of 2 μm or less and an optical axis tilt of 20 seconds or less. Furthermore, the surface accuracy satisfies the standard value and can be improved compared to the fourth embodiment, and it is a class that requires high optical axis accuracy among the lenses of the digital compact camera, and obtains a lens with high surface accuracy. I was able to.

  In this way, the fastening member including the elastic body that is elastically deformed with respect to the force in the range of 10N or more and 10000N or less applied in the direction opposite to the force to fasten the first to third divided barrel molds 61 to 63 of the three members. , Fasten and fix. As a result, the looseness of the upper mold member 75 and the lower mold member 76, the first to third divided cylinder molds 61 to 63, and the cylindrical bearing member 79 at the time of press molding are absorbed and the tight fitting state is absorbed. . As a result, it becomes possible to slide the molding die without backlash, and further, an asymmetric temperature distribution with respect to the shaft is less likely to occur compared to the fourth embodiment. A molded product molded with this mold has an extremely high optical axis accuracy, the surface accuracy satisfies the standard value, and an optical element better than that of the fourth embodiment can be obtained.

  The present invention is not limited to the embodiments described above. For example, the number of molds can be expanded to a large number of molds. Furthermore, the present invention can be applied to various cases in terms of applied mold materials, thermal expansion coefficients, and temperature relationship between the inside and outside of the mold set. For example, the present invention can be applied to the case where a ceramic mold material is used or a heating source or a cooling source is inside the upper mold member or the lower mold member.

1 shows a mold for molding an optical element according to a first embodiment of the present invention, wherein (a) is a schematic cross-sectional view taken along line BB in (b), and (b) is taken along line AA in (a). It is a model longitudinal cross-sectional view which follows. FIG. 5 is a schematic cross-sectional view similar to FIG. 1A of an optical element molding die according to a second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view similar to FIG. 1A of an optical element molding die according to a third embodiment of the present invention. FIG. 5 is a schematic cross-sectional view similar to FIG. 1A of an optical element molding die according to a fourth embodiment of the present invention. It is a schematic longitudinal cross-sectional view similar to FIG.1 (b) of the shaping | molding die of the optical element by the 4th Example of this invention. It is a schematic cross section by the side of the upper mold member of the shaping | molding die of the optical element by the 5th Example of this invention. It is a schematic cross section by the side of the lower mold member of the shaping | molding die of the optical element by the 5th Example of this invention. It is a model longitudinal cross-sectional view of the shaping | molding die for optical elements by the 5th Example of this invention. It is a model longitudinal cross-sectional view of the shaping | molding die for the conventional optical elements. FIG. 10 is a schematic cross-sectional view of a molding die for the optical element shown in FIG. 9.

Explanation of symbols

1, 21, 31, 41 One split cylinder type 1a, 21a, 31a, 41a Reference surface 1b, 2b, 21b, 22b, 31b, 32b, 41b, 42b Coupling portion 1c, 2c Adjustment portion 2, 22, 32, 42 The other split barrel mold 2a, 22a, 32a, 42a Reference surface 3, 23, 33, 43, 64 Bolt 4, 24 Lock nut 5, 55, 75 Upper mold member 5a, 6a, 55a, 56a, 75a, 76a Molding surface 5b, 6b Collar part 6, 56, 76 Lower mold member 9 Roller 10 Retainer 11, 49, 79 Bearing 25, 45, 65 Spring 34 Thermal expansion member 44, 66 Nut 61 First split cylinder type 62 Second split cylinder Type 63 Third split cylinder type 61a, 62a, 63a Reference surface 61b, 62b, 63b Coupling part

Claims (5)

An upper mold member having a molding surface for transferring an optical functional surface, a lower mold member having a molding surface for transferring an optical functional surface, and the upper mold member and the lower mold member having the molding surfaces opposed to each other An optical element having a holding part that guides the glass so as to approach and separate from each other, and press-molds a heat-softened glass material disposed between the upper mold member and the lower mold member. In the mold for
The body mold is configured such that at least two divided body molds are coupled to each other by fastening members at joint portions connected to both side ends of the holding sections of the divided body molds, and the upper mold member and the lower A mold for molding an optical element, characterized by comprising an adjusting means for adjusting a clamping force with respect to a mold member.   The said adjustment means consists of the site | part which carries out the elastic deformation which reduced rigidity compared with the other site | part formed between the said holding | maintenance part and the said coupling | bond part in the said division | segmentation cylinder type | mold. A mold for molding the described optical element.   2. The mold for molding an optical element according to claim 1, wherein the adjusting means includes an elastic member that constantly urges the split body mold so as to clamp the upper mold member and the lower mold member.   The adjusting means is constantly energized from the outside of at least one of the divided cylinder molds so that the divided cylinder mold clamps the upper mold member and the lower mold member, and has a thermal expansion coefficient of thermal expansion of the divided cylinder mold. 2. The mold for molding an optical element according to claim 1, wherein the mold is made of a thermal expansion member larger than a coefficient.   The adjusting means includes a thermal expansion member interposed between the coupling portions of the split cylinder type coupled to each other, and a material having a thermal expansion coefficient smaller than that of the split cylinder type. The mold for molding an optical element according to claim 1, wherein

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