JP2004137146A - Method and apparatus for forming optical glass element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an optical glass element which is very difficult to form, by positively controlling the temperature distribution inside an optical glass base material to be formed during heating and cooling. <P>SOLUTION: The optical glass base material is arranged between a couple of upper and lower molds, and the base material is heated and made into a flowable state while heating the above-mentioned molds. Thereafter, press molding is performed by approximating the molds relatively, and after cooling, the optical glass element is taken out by releasing the optical glass base material from the molds. During heating or cooling or heating and cooling, a temperature distribution is imparted to the molds. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method and a device for forming an optical glass element.

Recently, there has been an increasing demand for lens system design flexibility, miniaturization or large aperture, which has been impossible so far, and improvement in optical performance, and the need for aspherical lenses that can achieve this has been increasing. As a method for molding an optical element having an aspheric lens shape, there are many methods for forming an optical element having a desired shape by pressing an optical glass material in a state of being disposed between molds having an aspherical shape. Is being developed.

For example, in a state where an optical glass material is sandwiched between a pair of substantially cylindrical molds slidably inserted into a sleeve (hereinafter, simply referred to as “sleeve”) which is a substantially cylindrical member, Heating is performed from the outer periphery by a lamp heater, and a molding die is relatively approached and pressed to perform molding. In this method, the lamp heater is designed to heat the mold and the optical glass material evenly. As a method for such uniform heating, in Japanese Patent Application Laid-Open No. Hei 7-277750 and the like, a temperature control is performed so that a hollow concave portion is provided inside a mold so as to cancel the disturbance of the molding surface. As described above, on the structure of the molding die or the heating means, various means for equalizing the temperature distribution are based on the concept that it is optimal to maintain the uniform temperature distribution inside the glass to be molded. Things.

However, in such a method, when the optical glass material is thick or aspherical, it is difficult to uniformly control the temperature distribution, and it is impossible to cope with the problem. For this reason, a method of controlling the temperature according to the thickness of the optical glass material has been conventionally developed.

As one of the conventional methods, in a method including a step of heating an optical glass material by itself, at the time of heating the element alone, a temperature distribution is given according to a thickness of a desired optical glass element shape. (See Patent Document 1)

Further, as another method, in a cooling step after molding, cooling is performed while maintaining the temperature at the center of the optical surface portion higher than the temperature of the non-optical surface portion (see Patent Document 2).
JP-A-5-24858 JP-A-2-55235

However, as in JP-A-5-24858, even if the optical glass material is formed by applying a temperature distribution in a heating step in a single state of the optical glass material before pressing, the optical glass material and the molding die are actually formed. Since heat exchange occurs between the optical glass material and the mold within a very short time after the contact of the molding surfaces, there is a problem that the applied temperature distribution disappears. This has been clarified as a result of actually calculating the temperature distribution using the recently advanced simulation technology for temperature distribution calculation.

In Japanese Patent Application Laid-Open No. 2-55235, a part of a mold in contact with a heat source is provided with a hollow in order to impart a temperature distribution to the mold during cooling. However, according to the present invention, the temperature distribution is not positively imparted regardless of during heating or cooling, and the temperature distribution cannot be controlled reliably and accurately.

The object of the present invention is to solve the above-mentioned conventional problems by positively controlling the temperature distribution during heating and cooling inside the optical glass material to be molded. More specifically, it solves the conventional problems by controlling not only the temperature control of the optical glass element during cooling, which has been attracting attention, but also the transitional temperature distribution from heating to cooling. And a molding method and a molding apparatus therefor.

In order to achieve the above object, a method for molding an optical glass element according to the invention of claim 1 includes disposing an optical glass material between a pair of opposed upper and lower molds and heating the mold. While heating the optical glass material to a flowable state, performing press molding by relatively approaching the mold, and after cooling, separating the mold and the optical glass material, the optical glass In the molding method for removing a material, a temperature distribution is given to the molding die during the heating, the cooling, or the heating and the cooling.

As described above, by giving the temperature distribution to the mold, a highly accurate optical glass element can be obtained.

The invention according to claim 2 is the method for molding an optical glass element according to claim 1, wherein the optical glass material starts to be deformed by the pressing due to the relative approach of the molding die, and then after the cooling. The time required for separating the mold and the optical glass material from each other is 50 seconds or more.

The invention according to claim 3 is the method for molding an optical glass element according to claim 1 or 2, wherein, during the pressing of the optical glass material, portions of the molding die and the optical glass material that are not in contact with each other. It is characterized by heating or cooling by gas.

The invention of claim 4 is the method for molding an optical glass element according to any one of claims 1 to 3, wherein a temperature distribution in which a temperature at a central portion is higher than a peripheral portion is given to the molding die, It is characterized by molding a glass element.

The method for molding an optical glass element of the invention according to claim 5 is the method for molding an optical glass element according to claim 4, wherein a temperature distribution in which a temperature at a central portion is higher than that at the outer peripheral portion is given to the molding die, An optical glass element having a length in a direction parallel to a direction in which the mold is relatively approached and having an outer peripheral portion longer than a central portion is molded.

The invention according to claim 6 is the method for molding an optical glass element according to any one of claims 1 to 3, wherein a temperature distribution in which a temperature at a central portion is lower than that at an outer peripheral portion is given to the molding die. It is characterized in that the element is molded.

The method for molding an optical glass element according to the invention of claim 7 is the method for molding an optical glass element according to claim 6, wherein a temperature distribution in which a temperature at a central portion is lower than that at the outer peripheral portion is given to the molding die. An optical glass element having a length in a direction parallel to a direction in which the mold is relatively approached and having an outer peripheral portion shorter than a central portion is molded.

The invention of claim 8 is the method for molding an optical glass element according to any one of claims 1 to 7, wherein a tangent of a molding surface where the molding die comes into contact with the optical glass material, and the molding die are relative to each other. A maximum value of an angle formed by a plane perpendicular to the direction approaching to is 15 degrees or more.

The molding apparatus for an optical glass element according to the ninth aspect of the invention is to dispose an optical glass material between a pair of upper molds and a lower mold opposite to each other, heat the molds, and remove the optical glass material. Heating to a flowable state, performing press molding by relatively approaching the molding die, separating the molding die and the optical glass material after cooling, and taking out an optical glass element, It is characterized by having a temperature distribution providing means for providing a temperature distribution to the mold.

As described above, by providing the temperature distribution to the mold by the temperature distribution applying means, a highly accurate optical glass element can be obtained.

According to a tenth aspect of the present invention, there is provided the optical glass element molding apparatus according to the ninth aspect, wherein the temperature distribution imparting means is provided in the space formed inside at least one of the upper mold and the lower mold. It is characterized in that a temperature adjusting member made of a material having a different thermal conductivity from the material is arranged.

According to an eleventh aspect of the present invention, in the optical glass element molding apparatus according to the tenth aspect, the temperature adjustment member is in contact with the molding die and a shaft member to which the molding die is fixed. And

According to a twelfth aspect of the present invention, there is provided the optical glass element forming apparatus according to the tenth or eleventh aspect, wherein the temperature adjusting member has a heating unit.

According to a thirteenth aspect of the present invention, in the optical glass element molding apparatus according to the eleventh or twelfth aspect, the amount of heat transmitted by the temperature adjusting member is such that the amount of heat transmitted by the contact between the molding die and the shaft member. It is characterized by being larger than the amount.

According to a fourteenth aspect of the present invention, in the apparatus for molding an optical glass element according to any one of the ninth to thirteenth aspects, the temperature distribution providing means is provided near a shaping die of a shaft member fixing the shaping die. It is characterized in that gas or liquid is circulated in the flow path.

According to a fifteenth aspect of the present invention, there is provided the optical glass element molding apparatus according to any one of the ninth to fourteenth aspects, wherein the molding die is disposed inside a sleeve which is a substantially cylindrical member, and is provided outside the sleeve. And a light energy heating means for heating the mold from the above.

The invention of claim 16 is the optical glass element molding apparatus according to claim 15, wherein the sleeve has a plurality of gas permeable holes formed therein.

The invention according to claim 17 is the molding apparatus for an optical glass element according to claim 15 or 16, wherein the light energy heating means comprises two or more light energy heating means corresponding to the upper mold and the lower mold. In addition, the sleeve has a heat insulating boundary corresponding to the upper mold and the lower mold.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to implement | achieve the shaping | molding conditions by various temperature distributions which were not possible conventionally, and this enables shaping | molding the optical glass element with a high shape difficulty which was not able to be done conventionally. Can be. In addition, the optical glass element can be manufactured by greatly increasing the molding surface accuracy or the molding stability, and furthermore, the shape change (for example, “warping”) occurring in the optical glass element can be controlled and the mold can be easily released. It is possible to control the amount of shrinkage to the mold, and it is not always necessary to take measures to improve precision such as delicate control of the molding pressure and the maintenance of the molding pressure as in the conventional isothermal heating molding. Can be shortened.

The present invention will be described in principle with reference to FIGS. FIG. 1 shows a biconcave lens having a rotationally symmetric shape with respect to the optical axis, a center thickness in the optical axis direction of 1 mm, an outermost peripheral portion in contact with the molding die having a thickness of 4 mm, and a diameter of 15 mm. 5 shows a molding die for molding, in which an upper upper die 51 and a lower lower die 52 face each other. The molding surface 51a of the upper mold 51 has an aspherical shape, and the molding surface 52a of the lower mold 52 has a spherical shape. The shape of the optical glass element to be molded may be other than the rotationally symmetrical shape shown in FIG. 1, for example, a prism or a binary optical element, or a non-rotationally symmetrical glass element shape forming a toric surface. And other shapes.

(4) The optical glass material 55 is sandwiched between the upper mold 51 and the lower mold 52, and heating thereof is started. Here, the heating is performed in a state where the upper mold 51 and the lower mold 52 and the optical glass material 55 are in contact with each other until the pressing is started. However, after the heating is completed, the upper mold 51 may be brought into contact with the optical glass material 55. Although the shape of the optical glass material 55 to be molded is a cylindrical shape on both planes, the shape and type of the optical glass material 55 are limited as long as the optical glass material 55 and the shape at the time of completion of molding are slightly different. Not something.

Glass transition temperature of the optical glass material 55, for example, at 510 ° C., the viscosity at that time ^is 10 12.75 poise, a softening point for example, at 595 ° C., the viscosity at that ^time, at 10 7.65 poise Yes, the temperature-viscosity curve in this section changes almost linearly. By heating the optical glass material 55, the upper mold 51 and the lower mold 52, the temperature of the optical glass material 55 reached 550 ° C. or more, and the optical axis center (surface top) of the molding surface of the upper mold 51 reached 555 ° C. Pressing starts at that point. At this time, the temperatures of the outermost peripheral portions of the molding surfaces 51a and 52a of the upper mold 51 and the lower mold 52 that are expected to come into contact with the optical glass material 55 are set to 548 ° C.

The pressing force F for performing the pressing is, for example, 2000 N / cm ² . Simultaneously with the pressurization, the heated optical glass material 55 starts to be deformed, and along the upper mold 51 and the lower mold 52, the molding surfaces 51a and 52a of the upper mold 51 and the lower mold 52 and the optical glass material 55 in contact therewith. The optical glass material 55 is extended in the peripheral direction while the temperature of the glass material 55 is assimilated to the temperature of the upper mold 51 and the lower mold 52 having a much larger heat capacity. To go.

FIG. 1 shows a state immediately after the pressing is started. Since the optical glass material 55 existing at the center of the molding surface 51a of the upper mold 51 hardly flows to the outer peripheral side, it is perpendicular to the tangent line of the upper mold 51. When the pressure F is applied in a certain direction, a reaction force F 'is generated, but since the viscosity is reduced, F> F', and the optical glass material 55 starts to deform.

Next, when the optical glass material 55 is spread by pressing, the angle θ between the tangent to the molding surface and the plane perpendicular to the optical axis becomes 20 ° (the upper mold 51-the optical glass material 55 at this time). FIG. 2 illustrates a case where molding is performed at a uniform temperature, which has been performed conventionally, in the case where the contact portion is point A).

In FIG. 2, as the distance from the center position increases, the decomposed reaction force decreases, and the reaction force F ″ at the point A becomes very small as compared with the reaction force F ″ at the center portion. This is because the degree of freedom of flow is higher because the outer peripheral portion has a free outer peripheral portion (a non-molding contact portion of the optical glass material 55) as compared with the central portion of the optical glass material 55. Further, the released area increases when the length in a direction parallel to the direction in which the mold is relatively approached is longer than the central portion, and the pressure acting on the molding surface decreases. Similarly, the reaction force from the optical glass material 55 decreases as the angle θ formed with respect to a plane perpendicular to the optical axis of the outer peripheral portion increases. Further, when the angle θ exceeds a predetermined angle, the optical glass material 55 may be separated from the molding surface.

As a result, in the related art, when approaching the outer peripheral portion, it is not possible to obtain a pressure for securing a desired molding surface accuracy. FIG. 3 shows a method of the present invention in which pressing is performed by using a mold provided with a temperature distribution as compared with the conventional method.

At the point A of the upper die 51 shown in FIG. 3, a temperature distribution lower by 3 ° C. than the optical axis center position of the upper die 51 is given to the upper die 51. In this case, at point A, the heat exchange with the optical glass material 55 in contact with the molding surface of the molding die causes the temperature to be lower than the center position and the viscosity to be higher, so that the degree of freedom of flow decreases. Therefore, the reaction force F "" at the point A can be increased. That is, it is possible to improve the transfer accuracy by increasing the pressing force on the molding surface. In particular, when the angle between the tangent of the molding surface and the plane perpendicular to the optical axis is 15 ° or more, a remarkable effect is produced as compared with FIG.

In the present invention, in order to lower the viscosity of the glass, the temperature of the molding surface being heated and pressed, that is, the temperature distribution of the molding die is dynamically changed, and thereby, the optical glass is formed at the central portion and the outer peripheral portion. It is possible to control the pressure acting on the material 55 and the molding surface. Here, the ideal temperature difference between the central portion and the peripheral portion greatly varies depending on the viscoelasticity and pressing speed of the glass to be pressed, the volume of the optical glass material 55, and the shape of the molding surface, but is not particularly defined, but at least. It is desirable to provide a temperature difference of 2 ° C. or more, which is larger than the temperature measurement error.

For example, when the shape to be molded is a convex lens in which the thickness of the outer peripheral portion is smaller than the thickness of the vicinity of the central portion, the radially extending distance becomes larger toward the outer peripheral portion due to a change in the relative distance between the upper mold 51 and the lower mold 52. . In other words, the flow speed of the optical glass material 55 increases, but the flow direction of the optical glass material 55 and the pressing direction of the molding surface (for example, 51a) are opposite to each other, and the resistance for spreading at the same time increases. By increasing the pressure, the molding pressure for pressing the mold can be reduced, and at the same time, the molding surface accuracy of the outer peripheral portion can be ensured.

(4) After sufficient deformation of the optical glass material 55 is completed, the process proceeds to a step of starting cooling. In the steps up to this point, there is an effect that the temperature distribution is given to the optical glass material 55 via the temperature distribution already given to the molding die. In the case of a conventional method of starting to apply a temperature distribution after starting cooling, the cycle time can be extended by performing partial cooling, or less preferably, by performing partial heating. This is inevitable, and is likely to become an unstable factor in securing the stability of the surface accuracy. On the other hand, in the method of the present invention, the temperature distribution applied during the heating is maintained, or the shape of the distribution is continuously changed, thereby shifting to the next step in a stable state, that is, the cooling step of lowering the temperature. It becomes possible. It is not always necessary to change the state of the distribution, but according to the temperature distribution providing means of the present invention, it is possible to control the temperature distribution stably and positively.

In the cooling step, when cooling is started in a uniform temperature state, that is, in a state in which there is no temperature difference between the mold and the optical glass material as in the related art, Japanese Unexamined Patent Application Publication No. 2-552352 uses FIG. Catastrophic problems occur as described. This is because, as shown in FIG. 4 of the publication, the mold and the glass at the outer peripheral portion are separated due to the difference in the amount of shrinkage generated based on the difference in the thickness of the glass between the central portion and the peripheral portion. At this time, if the viscosity of the glass is sufficiently high, the transfer accuracy of the molding surface does not decrease, but in reality, the peeling occurs in a cooling state where the increase in the viscosity is still insufficient, so that the desired transfer accuracy can be reduced. I can't get it.

On the other hand, the present invention is different from the conventional method in which the temperature distribution from the central portion to the peripheral portion of the optical glass material in contact with the molding die is not particularly controlled. In the present invention, the temperature distribution applied to the mold is positively controlled, and the above problems can be solved.

FIG. 4 illustrates this, and shows a state immediately before the pressing by the mold is completed, the optical glass material 55 spreads to a desired range, and cooling is started. The central temperature and the outer peripheral temperature are continuously controlled to 555 ° C. and 545 ° C., respectively, until the optical glass material 55 is completely spread, and the pressure is maintained in the same state as at the time of pressing.

The overall temperature decreases over time due to cooling and eventually reaches a state where it cannot flow. In such a process, it is possible to generate a state in which the central portion can flow and the outer peripheral portion cannot flow due to the applied temperature distribution. At this time, in response to the contraction of the outer peripheral portion, the central portion can be further deformed so that the optical glass material 55 does not separate from the molding surface due to the contraction of the outer peripheral portion. Strictly, the flow state is stopped from a position separated from the molding surface of the outer peripheral portion, and the flow is slightly generated to the outer peripheral portion, so that the occurrence of the peeling can be prevented.

The control of the flow by the temperature distribution not only prevents the separation between the molding surfaces 51a and 52a and the optical glass material 55, but also prevents the molded product from cracking during cooling. . That is, in the shape of the molding surface shown in the figure, when pressing and cooling are performed at the conventional uniform temperature, a change in the shape (for example, “warpage”) due to cooling occurs due to the shape factor. This corresponds to a distance L1 on the aspheric surface side and a distance L1 on the spherical surface side with respect to a plane perpendicular to the optical axis 53 of the molded product shown in FIG. Assuming the stress generated in the optical glass material 55 when the distance L2 is different and cooled at a uniform temperature, the stress occurs because the residual stress on the aspherical surface side is large. On the other hand, in the present invention, the above-mentioned “warpage” is unlikely to occur. This is because a flow is generated at the time of cooling, whereby the stress can be controlled to the minimum state, so that the internal distortion can be significantly reduced. In such a state, sufficient cooling is performed, and the upper mold 51 and the lower mold 52 are relatively separated from each other in a region where the glass does not flow to obtain a molded optical glass element.

In the present invention, the heating of the optical glass material is completed, the optical glass material starts to deform by relatively approaching the mold, and after completing the pressing, is cooled and any one of the molds is removed from the optical glass material. It takes 50 seconds or more to separate them, during which time the positive temperature distribution is continued. Thereby, the conventional problem that the temperature distribution disappears in a short time can be solved.

In the present invention, by controlling the temperature distribution, the “warp” of the optical glass material 55 that can be easily released while maintaining the transfer accuracy of the molding surface is reduced by the residual stress state in the optical glass material 55. Can also be created. That is, by using the means for positively changing the temperature distribution of the upper and lower molds, it is possible to control the flow state generated in the molded article, and furthermore, the direction and amount of stress generation.

Next, the operation of the convex lens in the cooled state will be described. In the case of a convex lens, contrary to a concave lens, in the cooling process, the temperature in the central portion, that is, the portion with a large thickness is low, and the temperature in the portion with a small thickness in the outer peripheral portion is cooled with a high temperature distribution. Even if the viscosity increases and shrinkage occurs in a non-flowable state, the outer peripheral portion is still in a flowable state, so that the glass is further spread to the outer peripheral portion, thereby preventing separation of the molding surface and the glass. . Also, in the case of conventional uniform cooling, that is, when cooling while maintaining the temperature distribution, even if the molding surface is cooled evenly, the cooling at the center portion is delayed due to the difference in heat capacity generated from the shape, and finally the center glass is cooled. The part shrinks. Accordingly, the molded product is damaged because the outer peripheral portion and the central portion are pulled. This often occurs when cooling is performed in a short time to shorten the cycle time. However, by using the present invention, damage can be prevented. In addition to the above, by actively controlling the temperature distribution according to the present invention, it is possible not only to prevent the breakage of the molded article, but also to control the amount of the optical surface of the molded article and its position. .

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

(Embodiment 1)
FIG. 6 shows a molding apparatus according to the first embodiment in which a temperature distribution can be given.

The upper mold 1 and the lower mold 2 are made of a material (for example, cemented carbide, SIC, or the like) having sufficient strength in a temperature range enough to mold the optical glass material 20. These dies 1 and 2 are connected by attachments 16 and 17 to an upper shaft 5 and a lower shaft 6 for relatively driving the dies. In addition, although the shape of the molding surface of the upper mold | type 1 and the lower mold | die 2 is flat for ease of description, the molding surface can be made into a desired shape quite arbitrarily.

空間 A space 3 and a space 4 are formed inside the upper mold 1 and the lower mold 2. The spaces 3 and 4 are formed so as to be located at substantially the center of each of the molds 1 and 2. The spaces 3 and 4 are filled with a material having a thermal conductivity smaller than that of the material forming the molds 1 and 2, for example, high-density alumina. As long as the heat conductivity and the heat capacity are equal to or lower than the heat conductivity of the material constituting the mold, an optimum material for a desired temperature distribution described later can be appropriately selected.

熱 A thermocouple 10 and a thermocouple 11 are inserted inside the upper mold 1 and the lower mold 2. An atmosphere heating furnace 8 as a heating means is provided around the upper mold 1, and an atmosphere heating furnace 9 is similarly provided near the lower mold 2. The heating means does not need to be limited to the atmosphere heating furnaces 8 and 9 and can be replaced with a lamp heater or the like. Although the atmosphere heating furnaces 8 and 9 are divided into two corresponding to the upper and lower molds, one atmosphere heating furnace may be used if it is not necessary to adjust the temperatures of the upper and lower molds 1 and 2. . These atmosphere heating furnaces 8 and 9 are controlled in temperature by thermocouples 12 and 13.

Cooling paths 18 and 19 are formed in the upper shaft 5 and the lower shaft 6, and by supplying a cooling medium to the cooling paths 18 and 19, the temperature of the upper mold 1 and the lower mold 2 can be controlled. I have.

In this embodiment, first, the optical glass material 20 is placed on the lower mold 2 by means (not shown), and the upper shaft 5 connected to the upper mold 1 via the attachment 16, The lower glass 6 connected to the mold 2 is relatively approached to sandwich the optical glass material 20, and the upper mold 1, the lower mold 2, and the optical glass material 20 are heated by the atmosphere heating furnaces 8 and 9 using thermocouples 10 and 11. And heat while controlling the temperature.

When the upper mold 1, the lower mold 2, and the optical glass material 20 reach a desired temperature due to radiant heat, a drive unit (not shown) (for example, a linear motion direction using a linear motion air cylinder or a servomotor and a ball screw). Of the optical glass material 20 by applying pressure. Then, after bringing the upper mold 1 and the lower mold 2 close to a desired position, heating by the atmosphere heating furnaces 8 and 9 is stopped, and cooling is started.

At the same time, cooling is started by flowing a cooling medium into the cooling paths 18 and 19 in which the gas has been sealed up to that point. The cooling medium used is pure water pressurized to 20 N / cm ² , but depending on the desired cooling rate, an oil having a larger heat capacity, for example, mineral oil of ISO VG78 class, or steam or nitrogen having a smaller heat capacity may be used. Can be used. At the time of heating, depending on the type of the constituent material of the upper shaft 5 and the lower shaft 6 (for example, SUS304), the temperature of the upper shaft 5 and the lower shaft 6 exceeds the temperature at which the strength of the material of the upper shaft 5 and the lower shaft 6 decreases. It is necessary to control so that the temperature does not rise. In this case, a thermocouple (not shown) for temperature measurement is installed on the upper shaft 5 and the lower shaft 6 and a small amount of cooling medium flows through the cooling paths 18 and 19 to suppress an excessive rise in temperature. These cooling methods are the same for the following embodiments.

(4) After the cooling is started, the heated thermal energy is transmitted to the molds 1 and 2 and moved out of the system by the cooling medium circulating in the cooling paths 18 and 19 inside the upper shaft 5 and the lower shaft 6. At this time, the temperature distribution of the optical glass material 20 that is in contact with the upper mold 1 and the lower mold 2 is such that heat is taken from the outer periphery due to the structural characteristics of the molding die, and the temperature of the outer periphery decreases with respect to the center. I do. The materials filled in the spaces 3 and 4 are heated to almost the same temperature when the molds 1 and 2 are heated, and have low thermal conductivity, so that the temperature at the center can be kept high.

Cooling of the mold is started, and the temperature decreases due to heat conduction to the shafts 5 and 6. However, the material filled in the spaces 3 and 4 has a lower thermal conductivity than the material constituting the mold. In addition, the temperature drops with a delay with respect to the temperature drop of the mold. This makes it possible to keep the temperature at the central part higher than the temperature at the outer peripheral part of the mold, and to set the width of the temperature distribution large. In addition, the temperature distribution state of the molding surface in contact with the pressed optical glass material 20 also changes depending on the shape of the spaces 3 and 4 inside the molding die, so that the spaces 3 and 4 can be freely adjusted according to the desired optical element shape. By setting the shape of the temperature distribution and adjusting the cooling rate, it is possible to arbitrarily set the temperature width of the temperature distribution and the shape of the distribution.

(Embodiment 2)
FIG. 7 shows a molding apparatus according to Embodiment 2 of the present invention. The difference between this embodiment and the first embodiment is that heat conduction shafts 14 and 15 as temperature adjusting members are inserted and arranged in spaces 3 and 4 inside upper mold 1 and lower mold 2. . Each of the heat conduction shafts 14 and 15 has one side in contact with the upper shaft 5 and the lower shaft 6 and the other side in contact with the upper mold 1 and the lower mold 2. In this case, the heat conduction shafts 14 and 15 are arranged so as to be in contact with the central portions of the molds 1 and 2.

The heat conduction shafts 14 and 15 are inserted and fitted into the upper shaft 5 and the lower shaft 6. As a material of the heat conducting shafts 14 and 15, it is preferable to use a material having a heat conduction that is substantially equal to or larger than that of the material used for the molds 1 and 2. At least 7 kcal / mh ° C. The effect can be sufficiently exhibited as long as it has conductivity. As a material, for example, when the material of the molds 1 and 2 is a cemented carbide, if the material of the heat conduction shafts 14 and 15 is not a combination such as alumina having a lower thermal conductivity than the cemented carbide, There is no particular problem.

In the first embodiment, the upper mold 1 and the lower mold 2 have a structure in which the upper mold 5 and the lower mold 6 are in direct contact with each other. In this embodiment, the upper mold 1 and the lower mold 2 Since the heat transfer shafts 14 and 15 are fixed by the attachments 16 and 17 while slightly floating from the upper shaft 5 and the lower shaft 6, the lengths of the heat transfer shafts 14 and 15 are correspondingly longer.

In this embodiment, similarly to the first embodiment, the optical glass material 20 is sandwiched between the upper mold 1 and the lower mold 2, and the upper mold 1, the lower mold 2, and the optical glass The material 20 is heated. When the upper mold 1 and the lower mold 2 reach a desired temperature, the two are relatively approached to press the optical glass material 20.

At this time, since the heat conduction shafts 14 and 15 are present inside the dies 1 and 2, the temperature distribution on the molding surfaces of the dies 1 and 2 during heating is lower at the central portion than at the outer peripheral portion. This is because the upper shaft 5 and the lower shaft 6 have no heating means and the temperature is low, so that the heat is transferred in the axial direction by the heat conduction shafts 14 and 15 which are in contact with the portions on the back side of the center of the molding surfaces of the dies 1 and 2. Because it is Thus, in this embodiment, it is possible to provide a temperature distribution in which the temperature at the central portion is lower than that at the outer peripheral portion during heating.

(4) After the press molding, a cooling medium is circulated through the cooling paths 18 and 19 of the upper shaft 5 and the lower shaft 6 for cooling. As a result, the temperatures of the upper shaft 5 and the lower shaft 6 decrease rapidly, and subsequently, the heat conduction shafts 14 and 15 are cooled, and the temperatures of the upper and lower dies 1 and 2 from the back side of the forming surfaces of the upper and lower dies 1 and 2 which are in contact. Decrease. That is, contrary to the first embodiment, a distribution in which the temperature at the central portion is lower than that at the outer peripheral portion can be realized during cooling.

After the cooling is started, the outer peripheral portions of the upper mold 1 and the lower mold 2 are heated by controlling the temperature to a desired temperature without stopping the energization of the atmosphere heating furnaces 8 and 9, and at the same time, the cooling paths 18 and 9 are cooled. By using the cooling by the heat exchange of the cooling medium through 19 together, it is possible to provide a distribution with a wider temperature range.

In this embodiment, the bottom surfaces of the molds 1 and 2 and the upper shafts and the lower shafts 5 and 6 are not in direct contact with each other, but this does not mean that some of them must not be in contact with each other in order to obtain the above effects. . Even if the bottom surfaces of the upper mold 1 and the lower mold 2 and a part of the upper shaft 5 and the lower shaft 6 are in contact with each other, a contact area where heat transfer exceeding the heat capacity transmitted by the heat conduction shafts 14 and 15 is not generated. In such a case, the above effects can be obtained. Therefore, by adjusting the contact area between the molds 1 and 2 and the shafts 5 and 6, it is possible to adjust the effect of the temperature distribution by the heat conduction shafts 14 and 15.

(Embodiment 3)
FIG. 8 shows a third embodiment of the present invention. In this embodiment, heat conduction shafts 14 and 15 are disposed inside the spaces 3 and 4 of the first embodiment, and the heat conduction shafts 14 and 15 have, for example, a cartridge heater 22 as heating means. 23 is inserted.

Unlike the second embodiment, the heat conduction shafts 14 and 15 into which the cartridge heaters 22 and 23 are inserted are inserted into the spaces 3 and 4 of the upper mold 1 and the lower mold 2 and adhere to the back side of the molding surfaces of the molds 1 and 2. Not only that, but also at the same time, the molds 1 and 2 are slightly fitted to the side surfaces.

In this embodiment, the contact between the heat conduction shafts 14 and 15 and the upper shaft 5 and the lower shaft 6 is set as small as possible. This is to minimize heat transfer between the upper shaft 5 and the lower shaft 6. For this purpose, if necessary, a heat insulating material or the like may be inserted between the heat conduction shafts 14 and 15 and the upper shaft 5 and the lower shaft 6.

In this embodiment, first, the optical glass material 20 is sandwiched between the upper mold 1 and the lower mold 2 by means (not shown), and is heated by the atmosphere heating furnaces 8 and 9. At this time, heating is performed using the cartridge heaters 22 and 23 at the same time. The merits are that the time required for the molds 1 and 2 to rise in temperature can be shortened, and heating can be performed in a state where a temperature distribution in the central portion is higher than that in the outer peripheral portion. In this case, since the temperature distribution can be changed by the heater outputs of the atmosphere heating furnaces 8 and 9 and the output balance of the cartridge heaters 22 and 23, the output of the cartridge heaters 22 and 23 allows the molds 1 and 2 to be output. It is also possible to make the heating state in which the temperature at the central portion, which is the reverse temperature distribution to that in the first embodiment, is higher than that at the outer periphery while shortening the heating time.

(4) After the desired temperature is reached, the molds 1 and 2 are relatively approached to press the optical glass material 20. At this time, by controlling the temperature of the cartridge heaters 22 and 23 in the heat conduction shafts 14 and 15 to a higher temperature than the set temperature of the atmosphere heating furnaces 8 and 9, the temperature distribution of the molding surface during heating becomes The central part is higher than the central part.

After that, in order to start cooling, the output of the atmosphere heating furnaces 8 and 9 is reduced or stopped, and the cooling medium is circulated through the cooling paths 18 and 19 of the upper shaft 5 and the lower shaft 6. As a result, the temperatures of the upper shaft 5 and the lower shaft 6 rapidly decrease, but the heat conduction shafts 14 and 15 are set so as to minimize the contact with the upper shaft 5 and the lower shaft 6. The back surfaces of the molding surfaces of the molds 1 and 2 and the slightly contacting side surfaces are not cooled directly from the upper shaft 5 and the lower shaft 6. Further, by maintaining the cartridge heaters 22 and 23 in the heat conduction shafts 14 and 15 at a high temperature, the temperature of the central portion can be reduced as compared with the outer peripheral portions of the dies 1 and 2 while cooling the entire system. It is possible to keep giving the temperature distribution kept high.

(Embodiment 4)
FIG. 9 shows a molding apparatus according to the fourth embodiment. In this embodiment, the molds 1 and 2 are inserted into a slidable sleeve 21 fitted therein with high precision. The sleeve 21 has a cylindrical shape and is fixed to the upper mold 1. Note that the sleeve means a substantially cylindrical member, and the sleeve 21 may be any member as long as it is a substantially cylindrical member. Here, the sleeve 21 is a cylindrical member. The heating means uses light energy, and specifically, infrared lamp heaters 28 and 29 are used. The heating means using light energy may be a short wavelength lamp heater or heating using a laser.

In this embodiment, the quartz tube 7 is used, and the dies 1, 2 and the peripheral system are inserted into a space in which the airtightness of the quartz tube 7 is ensured. Thereby, in a high temperature state, the molding can be performed in a non-oxidizing atmosphere with an inert gas, for example, nitrogen, so that the degree of corrosion can be significantly reduced even when a material oxidized at a high temperature is used. . Further, the infrared lamp heaters 28 and 29 are disposed outside the quartz tube 7, and thermocouples 12 and 13 which are temperature sensors for controlling the outputs of the infrared lamp heaters 28 and 29 are installed in the vicinity.

In this embodiment, the side surfaces of the dies 1 and 2 and the side surface of the sleeve 21 are not fitted on the entire surface, but are partially fitted. This is because, when cooling is started after completion of molding, when the sleeve 21 having a large heat capacity is fitted over the entire side surfaces of the molds 1 and 2, the temperature distribution at the outer peripheral portion is smaller than that in the first embodiment. This is because it is difficult to lower it. With this configuration, the driving accuracy of the upper and lower dies 1 and 2, that is, the eccentricity of the optical glass element can be easily maintained at high accuracy by the sleeve 21. It is possible to control the temperature distribution where the temperature is high.

If the thermal conductivity of the material forming the sleeve 21 is smaller than the thermal conductivity of the material of the molds 1 and 2, it is preferable to adjust the length of the fitting portion according to the thermal conductivity.

(Embodiment 5)
FIG. 10 shows a molding apparatus according to the fifth embodiment. This embodiment is based on the second embodiment shown in FIG. 7, but is different from the second embodiment in that the sleeve 21 is used, and the infrared lamp heaters 28 and 29 are used and hermetically sealed by the quartz tube 7. Is different.

In addition, the heat conduction shafts 14 and 15 are inserted into the molds 1 and 2, and the temperature inside the molds 1 and 2 can be set to be higher than the temperature at the outer peripheral portion on the molding surface. This is the same as in Embodiment 2. The side surfaces of the sleeve 21 and the molds 1 and 2 have a structure in which the fitting area is increased as much as possible. Therefore, even in a state where the entire optical glass material emits thermal energy, that is, in a state where the optical glass material is cooled, the sleeve 21 is heated by the infrared lamp heaters 28 and 29, so that a wide distribution temperature range can be controlled.

(Embodiment 6)
FIG. 11 shows a molding apparatus according to the sixth embodiment. In this embodiment, the cartridge heaters 22 and 23 as heating means are inserted into the heat conduction shafts 14 and 15, respectively, as compared with the fifth embodiment shown in FIG. By providing the cartridge heaters 22 and 23, heating from the inside becomes possible, and control with a wider distribution temperature range than in the fifth embodiment becomes possible.

(Embodiment 7)
FIG. 12 shows a molding apparatus according to the seventh embodiment. This embodiment differs from the fourth embodiment shown in FIG. 9 in that the molding surfaces of the molds 1 and 2 are optically combined with each other by using a gas filled or flowing as the inert gas G during cooling, for example, nitrogen gas. This cools the molds 1 and 2 and the optical glass material 20 that are not in contact with the glass material 20.

Further, a plurality of gas permeable holes 21 a penetrate through the cylindrical sleeve 21 in the thickness direction, so that gas can flow inside and outside the sleeve 21. In the first to sixth embodiments, the heat distribution on the molding surfaces of the molds 1 and 2 is transmitted to the optical glass material 20 to perform temperature distribution. In this embodiment, the molding surface and the optical glass material 20 are more positively affected. By controlling the temperature of the molds 1 and 2 and the optical glass material 20 at the portions where the glass is not in contact with the inert gas G, a more flexible temperature distribution can be provided during heating or cooling.

The gas used not only controls the temperature of the part where the molding surfaces of the molds 1 and 2 and the optical glass material 20 are not in contact, but also controls the temperature of the surface of the sleeve 21 or the side surfaces of the upper mold 1 and the lower mold 2. By generating heat exchange between them, it is possible to utilize the optical glass material 20 to control the temperature distribution.

In this embodiment, an inert gas is used, but the inert gas is not necessarily required as long as it can be used in an oxidizing atmosphere. In addition, as a gas, heat exchange can be performed by bringing a gas into contact with a temperature control unit (not shown) that has been cooled or heated to a temperature that can affect a desired portion to be changed. it can.

(Embodiment 8)
FIG. 13 shows a molding apparatus according to the eighth embodiment. In this embodiment, the configuration of the sleeve 21 is different from that of the sixth embodiment shown in FIG. That is, in the sleeve 21 of the present embodiment, the thermal insulation boundary 24 is provided between the sleeve portion corresponding to the upper die 1 and the sleeve portion corresponding to the lower die 2. In the sixth embodiment, even if the lamp heaters 28 and 29 are individually controlled in order to perform a desired temperature distribution or temperature control of the distribution, the desired temperature change is transmitted to the upper mold 1 and the lower mold 2 by the heat conduction of the sleeve 21. If this is not possible, this can be achieved by providing a heat insulating boundary 24 on the sleeve 21.

断 熱 The heat insulating boundary 24 of the sleeve 21 can be provided by, for example, reducing the thickness, reducing the cross-sectional area by making a hole, or fastening with a material having low thermal conductivity. By providing the heat insulating boundary 24 in this manner, the effect as a heat transfer member connecting the molds 1 and 2 can be reduced.

(Embodiment 9)
FIG. 14 shows a molding apparatus according to the ninth embodiment. In this embodiment, a biconcave lens having a rotationally symmetric shape is formed as an optical glass element.

The upper mold 1 and the lower mold 2 which are molding dies are made of a cemented carbide, each having a diameter (φ) of 30 mm, a diameter (φ) of the molding surfaces 1a and 2a of 27 mm, and a radius of curvature (R) of 25 mm. Has a convex shape. The molds 1 and 2 are fixed to the upper shaft 5 and the lower shaft 6 by attachments 16 and 17, respectively. Cooling paths 18 and 19 are formed in the upper shaft 5 and the lower shaft 6, and are filled with a gas (N ₂ ) before molding.

The molds 1 and 2 are inserted into the cylindrical sleeve 21 in a slidable fitting state, and the fitting clearance has a diameter difference of 5 μm. The sleeve 21 is made of porous alumina. Cylindrical spaces 3 and 4 are formed in the central portions of the dies 1 and 2, respectively. Thermocouples 10 and 11 are inserted inside the upper mold 1 and the lower mold 2, and heat conduction shafts 14 and 15 are arranged inside the cylindrical spaces 3 and 4.

(4) The heat conduction shafts 14, 15 have a shape having contact surfaces on the back sides of the molding surfaces 1a, 2a and the upper and lower shafts 5, 6, as shown in the figure. Stainless steel (SUS304) is used as the material of the heat conduction shafts 14 and 15. Inside the heat conduction shafts 14 and 15, small-sized cartridge heaters 22 and 23 each having an output of 600 W are arranged. The sleeve 21 and the side surfaces of the dies 1 and 2 are not in contact with each other, and a non-contact portion having a length of 20 mm in the axial direction from the molding surfaces 1a and 2a is provided.

光学 The optical glass element 20 is inserted between the upper shaft 1 and the lower shaft 2 by means not shown, and is sandwiched between the upper mold 1 and the lower mold 2 with a load of 30N. The optical glass material 20 is a glass material L-LAH53, has a cylindrical shape with a diameter of 25 mm and a thickness of 7 mm, and has a flat polished surface at both ends.

The system composed of the molds 1 and 2, the sleeve 21, and the shafts 5 and 6 is arranged in a sealed structure by a quartz tube 7 and a vertical hermetic member (not shown). Further, outside the quartz tube 7, infrared lamp heaters 28 and 29 having a total output of 4000 W are installed, and thermocouples 12 and 13 which are heat sensors for controlling the temperature are installed in the vicinity.

In this embodiment, first, the air in the closed space is replaced with an inert gas (nitrogen), and heating is performed by the lamp heaters 28 and 29 while continuously flowing at a flow rate of 10 L / min. At the same time, heating by the cartridge heaters 22 and 23 is started. In heating, first, the temperature is raised until the measured temperature of the thermocouples 10 and 11 reaches 600 ° C.

When the temperature reaches 600 ° C., the balance is adjusted so that the ratio of the total output W number of the lamp heaters 28 and 29 to the total output W number of the cartridge heaters 22 and 23 is 1: 1.2 (lamp heater). Heating is continued until the total output of 28 and 29 is about 1000 W, the output of the cartridge heaters 22 and 23 (one side is about 600 W), and the thermocouples 10 and 11 reach 610 ° C. When the temperature of the thermocouples 10 and 11 reaches 610 ° C., the temperature of the tops of the molding surfaces 1 a and 2 a of the dies 1 and 2 is 612 ° C. The surface temperature becomes 604 ° C.

After the above heating, in order to start pressing, the upper mold 1 and the lower mold 2 are relatively approached with a load of 8000 N by a driving device (not shown), for example, a combination of an air cylinder or a servomotor and a ball screw.

At this time, the temperature of the optical glass material 20 immediately before the deformation by the pressing was actually 608 ° C., but simultaneously with the flow by the pressing, the optical glass material 20 was formed from the top of the molding surfaces 1 a and 2 a of the molds 1 and 2. The temperature is adjusted to 610 ° C. at a position 1 mm toward the inside of the material 20, and after 30 seconds, the area where the molding surfaces 1 a and 2 a and the optical glass material 20 come into contact with each other is expanded to a position having a diameter of 20 mm by pressing. , 2 had a temperature of 606 ° C. After another 5 seconds, the temperature at a position 1 mm inward into the optical glass material 20 at the same position reaches 605 ° C. Here, the total output of the lamp heaters 28 and 29 is reduced to 700 W, and the pressing is continued.

After approximately 100 seconds, the molds 1 and 2 relatively move to a position where the distance between the molding surfaces 1a and 2a at which the pressing is completed is 1 mm, and the outermost peripheral portions of the molding surfaces 1a and 2a of the molds 1 and 2 The optical glass material 20 reaches a position having a diameter of 27 mm. At this time, the temperature at a position inward of 1 mm from the molding surface at the outermost peripheral portion of the optical glass material 20 is 602 ° C., and the speed at which the optical glass material 20 spreads is reduced, so that heat exchange is sufficiently performed. The temperatures are the same as the outermost peripheral surface temperatures of the effective forming surfaces 1 and 2.

Subsequently, a cooling step is started. First, circulation of pure water at 40 ° C. with a pressure of 50 N / cm ² at a flow rate of ² L / min is started through the cooling paths 18 and 19. Immediately after that, the output of the lamp heaters 28 and 29 is reduced at a total of 20 W / sec, and the output of the cartridge heaters 22 and 23 is reduced at a total of 2 W / sec. Fifteen seconds after the start of cooling, the surface top temperatures of the molding surfaces 1a and 2a of the dies 1 and 2 become 600 ° C., and the outermost peripheral portion of the optical glass material 20 drops to 570 ° C. At this time, the surface temperature of the optical surface is still at a temperature at which it can flow, but the outermost peripheral portion has already reached a viscosity region where flow is difficult.

後 Thereafter, the flow rate of the nitrogen gas is increased to 30 L / min, and the cooling is continued. After 30 seconds, the range in which the flow is possible in the entire area inside the optical glass material 20 with respect to the applied pressure disappears, and the shape as the optical glass element is determined. The surface temperature at the top of the optical surface is about 560 ° C.

According to this temperature condition setting, no deformation occurs such that the formed glass sticks to the forming surfaces 1a and 2a of the upper mold 1 and the lower mold 2, and at the same time, the outermost peripheral portion of the optical glass material 20 is not deformed. The molding is completed without causing separation from the molding surface due to the large amount of shrinkage. Although the flow rates of the cooling passages 18 and 19 are changed at the timing when the flow rate of nitrogen is changed to 30 L / min, the temperature at the center of the molds 1 and 2 can be similarly controlled. In the embodiment, a temperature distribution condition based on the above condition is set in order to obtain a balance of the temperature distribution toward the outer peripheral portion.

After that, the outputs of the lamp heaters 28 and 29 and the cartridge heaters 22 and 23 are set to 0 to increase the circulation amount of pure water to the cooling paths 18 and 19 to 10 L / min. This state is maintained up to 200 ° C. where the influence of oxidation does not become a problem even when the closed space including the molds 1 and 2 is exposed to the atmosphere. Then, the upper mold 1 and the lower mold 2 are relatively separated from each other, the molded optical glass element is taken out by means not shown, and the molding is completed.

This embodiment shows an example of the temperature distribution providing means, and it is possible to actively control various temperature distributions. Further, in this embodiment, for the sake of simplicity, the temperature distribution state of the upper mold 1 and that of the lower mold 2 are the same. It is also possible to reduce or improve the overall transfer accuracy.

(Embodiment 10)
In the tenth embodiment, a biconvex lens having a rotationally symmetric shape is formed as an optical glass element. FIG. 15 shows a molding apparatus used in this embodiment. There is no significant difference from the molding apparatus shown in FIG. 14, and the molding surfaces 1a and 2a of the molding dies 1 and 2 which are in contact with the optical glass material 20 of the upper mold 1 and the lower mold 2 are formed. It has a concave shape with a diameter (φ) of 27 mm and a radius of curvature (R) of 30 mm. SUS304 spacers 31 and 32 having a thickness of 1 mm are inserted between the heat transfer shafts 14 and 15 inserted into the molds 1 and 2 and the upper shaft 5 and the lower shaft 6, respectively. 1. The lower mold 2 is not in direct contact with the upper shaft 5 and the lower shaft 6. The upper mold 1 and the lower mold 2 are fixed to the upper shaft 5 and the lower shaft 6 by attachments 16 and 17 in a state of being connected by the heat conduction shafts 14 and 15. The sleeve 21 is made of a cemented carbide, and the side surfaces of the molds 1 and 2 are all fitted into the sleeve 21.

The optical glass material 20 sandwiched between the upper shaft 1 and the lower shaft 2 is a glass material having a trade name of “VC81 (manufactured by Sumita Optical)”, having a diameter of 23.2 mm, a center thickness of 8 mm, and a radius of curvature of the upper and lower surfaces. (R) has a 25 mm polished surface and has a biconvex shape.

In this embodiment, first, the inside of the closed space is replaced with nitrogen gas, and heating by the lamp heaters 28 and 29 is started while continuously flowing a volume of 5 L / min. at the same time. The heating by the cartridge heaters 22 and 23 is started, and the temperature is increased until the measured temperature of the thermocouples 10 and 11 reaches 540 ° C.

When the temperature reaches 547 ° C., the balance is adjusted so that the ratio of the total output W number of the lamp heaters 28 and 29 to the total output W number of the cartridge heaters 22 and 23 is 6: 1 (the lamp heaters 28 and 29 are not adjusted). Heating is continued until the total output is about 1200 W, the output of the cartridge heaters 22 and 23 (one side is about 100 W), and the thermocouples 10 and 11 reach 548 ° C. When the measurement temperature of the thermocouples 10 and 11 reaches 548 ° C., the temperature at the top of the molding surfaces 1a and 2a of the dies 1 and 2 is 549 ° C., and at the position of 27 mm in diameter corresponding to the outermost periphery of the effective molding surface. And its surface temperature is 554 ° C.

(4) After the heating, pressing is started, and the upper mold 1 and the lower mold 2 are relatively approached by a load of 6000N. At this time, the temperature of the optical glass material 20 immediately before the start of the deformation was actually 547 ° C., but simultaneously with the flow caused by the pressing, the optical glass material 20 was removed from the tops of the molding surfaces 1 a and 2 a of the dies 1 and 2. At a position of 1 mm inward, the temperature was adjusted to 549 ° C. which was almost the same as that of the molding surfaces 1a and 2a.

By continuing the pressing, the area where the molding surfaces 1a and 2a are in contact with the optical glass material 20 is expanded to a position having a diameter of 20 mm after 30 seconds, and the temperature of the optical surfaces 1a and 2a at this position is 550 ° C. . After another 5 seconds, the temperature at a position 1 mm inward of the optical glass material 20 at the same position reaches 549 ° C. Here, the ratio of the total output W number of the lamp heaters 28 and 29 to the total output W number of the cartridge heaters 22 and 23 is adjusted to be 20: 1, and the pressing is continued. After about 30 seconds, the molds 1 and 2 relatively move to a position where the pressing is completed, and the optical glass material 20 reaches a position having a diameter of 27 mm which is the outermost peripheral portion of the molding surfaces 1a and 2a of the molds 1 and 2. I do. At this time, the center temperature of the optical glass material 20 decreases to 547 ° C., and the temperature at a position inward of 0.2 mm from the molding surface at the outermost periphery is 555 ° C., which is lower than the speed at which the glass spreads and the resistance at which the glass spreads. In this state, the optical glass element is heated to a state where the viscosity is sufficiently low so that it can flow.

Subsequently, a cooling step is started. First, pure water at 20 ° C. at a pressure of 40 N / cm ² is circulated through the cooling paths 18 and 19 at a flow rate of 6 L / min. Immediately after that, the output of the lamp heaters 28 and 29 is reduced at 10 W / sec, and the energization of the cartridge heaters 22 and 23 is stopped.

で Ten seconds after the start of cooling, the surface top temperatures of the molding surfaces 1a and 2a of the dies 1 and 2 decrease to 530 ° C, and the outermost peripheral portion of the optical surface decreases to 550 ° C. At this time, the outer peripheral portion of the optical surface is still at a temperature at which it can flow, but the center portion has already reached a viscosity region where it is difficult to flow. After a further 30 seconds, the flowable range disappears in the entire region inside the optical glass material with respect to the applied pressure, and the shape of the optical glass element is determined. The surface temperature of the outermost peripheral portion of the optical surface is about 520 ° C.

According to this temperature distribution condition, it has conventionally been difficult to mold a lens having an outermost peripheral portion thickness (edge thickness) of 25 mm or more and 1 mm or less. Molding became possible. Further, regarding the surface accuracy of the central portion, although the transfer of the molded surface was not stabilized due to shrinkage, this problem could be solved.

Thereafter, the outputs of the lamp heaters 28 and 29 and the cartridge heaters 22 and 23 are set to 0 to increase the circulation amount of pure water to the cooling passages 18 and 19 to 10 L / min, and the closed space including the molds 1 and 2 is closed. Is cooled to 200 ° C., where the influence of oxidation does not become a problem even when exposed to an air atmosphere. Then, the upper mold 1 and the lower mold 2 are relatively separated from each other, and the optical glass material whose molding has been completed is taken out by means (not shown).

Note that this embodiment also shows an example of the temperature distribution providing means, and it is possible to actively control various other temperature distributions.

It is sectional drawing which shows the shaping | molding method by this invention. It is sectional drawing which shows the change of the vector at the time of shaping | molding. It is sectional drawing which shows the vector at the time of shaping | molding in the state to which the temperature distribution was provided. It is sectional drawing which shows the problem of the conventional shaping | molding. It is sectional drawing which shows shaping | molding by the shaping | molding conditions of this invention. FIG. 2 is a cross-sectional view of the molding device according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view of a molding device according to a second embodiment. FIG. 10 is a cross-sectional view of a molding device according to a third embodiment. FIG. 14 is a cross-sectional view of a molding device according to a fourth embodiment. It is sectional drawing of the shaping | molding apparatus of Embodiment 5. FIG. 13 is a cross-sectional view of a molding device according to a sixth embodiment. FIG. 14 is a cross-sectional view of a molding device according to a seventh embodiment. FIG. 15 is a cross-sectional view of a molding device according to an eighth embodiment. FIG. 21 is a sectional view of a molding device according to a ninth embodiment. FIG. 13 is a cross-sectional view of a molding device according to a tenth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper die 2 Lower die 3,4 Space 5 Upper shaft 6 Lower shaft 8,9 Atmospheric heating furnace 14,15 Heat conduction shaft 18,19 Cooling path 20 Optical glass material 21 Sleeve 22,23 Cartridge heater 28,29 Infrared lamp heater

Claims (17)

An optical glass material is disposed between a pair of upper molds and a lower mold that oppose each other, and the optical glass material is heated to a flowable state while heating the molds. In the molding method of performing the pressure molding by approaching, and removing the optical glass material by separating the mold and the optical glass material after cooling,
A method for molding an optical glass element, wherein a temperature distribution is imparted to the mold during the heating, the cooling, or the heating and the cooling. The time from when the optical glass material starts to be deformed by the pressing due to the relative approach of the mold to when the optical glass material is separated from the mold and the optical glass material after the cooling is 50 seconds or more. The method for forming an optical glass element according to claim 1, wherein: 3. The method of molding an optical glass element according to claim 1, wherein, during the pressing of the optical glass material, portions of the mold and the optical glass material that are not in contact with each other are heated or cooled by gas. . The method for forming an optical glass element according to any one of claims 1 to 3, wherein the optical glass element is formed by applying a temperature distribution having a temperature at a central portion higher than a peripheral portion to the mold. An optical glass in which a temperature distribution in which a temperature in a central portion is higher than that in the outer peripheral portion is given to the mold, and a length in a direction parallel to a direction in which the mold is relatively approached is longer in an outer peripheral portion than in the central portion. The method for forming an optical glass element according to claim 4, wherein the element is formed. The method for forming an optical glass element according to any one of claims 1 to 3, wherein a temperature distribution in which a temperature at a central portion is lower than that at an outer peripheral portion is given to the mold, and the optical glass element is molded. An optical glass in which a temperature distribution in which a temperature at a central portion is lower than that at the outer peripheral portion is given to the mold, and a length in a direction parallel to a direction in which the mold is relatively approached is shorter at the outer peripheral portion than at the central portion. The method for forming an optical glass element according to claim 6, wherein the element is formed. The maximum value of an angle formed by a tangent of a molding surface where the mold contacts the optical glass material and a plane perpendicular to a direction in which the mold relatively approaches is 15 degrees or more. 8. The method for molding an optical glass element according to any one of 1 to 7. An optical glass material is disposed between a pair of upper molds and a lower mold that oppose each other, and the optical glass material is heated to a flowable state while heating the molds. In the molding apparatus to perform pressure molding by approaching, and to remove the optical glass element by separating the molding die and the optical glass material after cooling,
An apparatus for forming an optical glass element, further comprising a temperature distribution providing means for providing a temperature distribution to the mold. The temperature distribution providing means includes a space formed inside at least one of the upper mold and the lower mold, in which a temperature adjusting member made of a material having a different thermal conductivity from the material of the mold is arranged. The optical glass element molding apparatus according to claim 9, wherein: The molding apparatus for an optical glass element according to claim 10, wherein the temperature adjusting member is in contact with the mold and a shaft member to which the mold is fixed. The optical glass element molding apparatus according to claim 10, wherein the temperature adjusting member has a heating unit. The optical glass element molding apparatus according to claim 11, wherein an amount of heat transmitted by the temperature adjusting member is larger than an amount of heat transmitted by contact between the molding die and the shaft member. 14. The method according to claim 9, wherein the temperature distribution providing unit is configured to allow a gas or a liquid to flow through a flow path provided in the vicinity of the molding die of the shaft member fixing the molding die. An apparatus for forming an optical glass element according to the above. The method according to any one of claims 9 to 14, wherein the molding die is disposed inside a sleeve that is a substantially cylindrical member, and further includes a light energy heating unit configured to heat the molding die from outside the sleeve. An apparatus for forming an optical glass element according to the above. The molding apparatus for an optical glass element according to claim 15, wherein the sleeve has a plurality of gas permeable holes. The light energy heating means comprises two or more light energy heating means corresponding to the upper mold and the lower mold, and the sleeve has an adiabatic boundary corresponding to the upper mold and the lower mold. An apparatus for forming an optical glass element according to claim 15.

Images