JP2012116705A - Molding apparatus and molding method for optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding apparatus for optical devices in which the temperature distribution of the molding apparatus is effectively controlled and high-accuracy optical devices can be molded in a good yield by controlling the temperature distribution.SOLUTION: In the molding apparatus 1 for optical devices, a mold 50 with an optical material placed between an upper mold part and a lower mold part is sequentially fed to heating, press molding and cooling stages 3, 4 and 5 to mold an optical device. The molding apparatus has a pair of upper and lower heating plates 3b, a pair of upper and lower press plates 4b and a pair of upper and lower cooling plates 5b which subject the mold 50 to heating, press molding and cooling processes, respectively. The cooling plates 5b internally have a plurality of evenly spaced cartridge heaters 5a and thermocouples disposed near the respective cartridge heaters, and furthermore the cooling plates 5b have output control means to which temperatures measured with the thermocouples are fed back to thereby independently control the outputs of the cartridge heaters one by one.

Description

  The present invention relates to a molding apparatus and a molding method capable of continuously manufacturing an optical element, and in particular, an optical element that can stably maintain a predetermined temperature by suppressing a temperature distribution of a cooling plate temperature for cooling an optical material. The present invention relates to a molding apparatus and a molding method.

  In recent years, a method for molding an optical element with high accuracy has been generalized, in which an optical material is accommodated in a molding die for an optical element, heated and softened, and press-molded. Under such circumstances, in order to reduce the manufacturing cost, there has been proposed an optical element molding apparatus that transports a molding die to each processing stage and continuously molds a plurality of optical elements.

  In these optical element molding equipment, when the optical material is softened by heating, it is heated to a high temperature condition sufficient to process the optical material, and during pressing, the pressed state is maintained and the optical material is cooled after pressing. And solidify to obtain an optical element. Therefore, in each processing stage in the molding apparatus, each stage is managed at a predetermined temperature.

  Each processing stage is generally composed of a pair of upper and lower plates each provided with a cartridge heater. The pair of upper and lower plates are usually configured by arranging a plurality of rod-shaped cartridge heaters at predetermined intervals in the horizontal direction inside a square flat plate. However, the plate temperature when arranged in this way is likely to decrease at the periphery of the plate, and the temperature at the center of the plate is likely to increase due to being surrounded by the heater. Therefore, the temperature distribution in which the heating state in the plate varies depending on the location occurs. Thus, when temperature distribution arises in a plate, it will affect even the temperature of the shaping | molding die on the plate and by extension, the molding surface which shape | molds an optical raw material.

  Therefore, in order to improve the temperature distribution on the plate, a soaking plate having a specific size in which the surface of the cemented carbide is coated with a predetermined alloy thin film is provided on the plate (see Patent Document 1), or the plate surface. In order to keep the temperature difference between the peripheral part and the inner part corresponding to the molding of the toner within a predetermined range, a technique for controlling the output of the inner and outer cartridge heaters is provided (see Patent Document 2), or a technique proposed Has been.

JP-A-8-259240 JP 2008-69019 A

  In a molding apparatus that sequentially performs processing while transporting and moving the above-mentioned mold, the mold is first taken into the apparatus, and the optical material is gradually heated at the first heating stage, and the final heating process is performed. Allow part to reach maximum temperature. Next, press molding is performed while maintaining this maximum temperature to give the optical element shape to the optical material. Finally, the temperature of the optical material is gradually lowered on the cooling stage to cool and solidify the optical material.

  However, when performing such a molding operation, the temperature gradient of the entire apparatus gradually increases from the inlet side of the mold, and the press stage for performing the press molding process is set at the apex toward the outlet side of the mold. Gradually lower.

  Therefore, each stage is affected by the temperature of the adjacent stage, and becomes higher or lower than a predetermined temperature, and a temperature difference occurs in the same plate. When a temperature difference is generated in the same plate in this way, a temperature distribution is also generated in the mold on the plate, which affects the molding of the optical material.

  For example, in the cooling stage, if the adjacent stage is a press processing stage, the temperature on the press processing stage side of the cooling stage is high, and the temperature on the opposite side is low, so the mold on the cooling plate A temperature distribution is generated inside, and the optical material cannot be uniformly cooled, and the cooling rate varies depending on the location. Therefore, there is a problem that a desired shape cannot be obtained and the yield is lowered. Such a problem becomes more apparent when the diameter of the optical element to be manufactured is increased and the distance between adjacent plates is shortened.

  The present invention has been made paying attention to such a problem, and in manufacturing an optical element, the plate temperature is made uniform so that the plate temperature of each stage is not affected by the plate temperature of the adjacent stage. An object of the present invention is to provide an optical element molding apparatus and molding method for manufacturing an optical element with high yield.

  As a result of intensive studies, the present inventors have found that the optical element molding apparatus and molding method of the present invention, which achieves uniform temperature in the plate, can solve the above problems, and have completed the present invention.

  That is, the optical element molding apparatus of the present invention sequentially conveys a molding die in which an optical material is placed between an upper die and a lower die to heating, pressing and cooling stages provided in the chamber. A molding apparatus for an optical element that molds the mold, wherein the mold is mounted at each of the heating, pressing, and cooling stages, and the heating, pressing, and cooling processes are performed on the mounted molding mold, respectively. A plurality of sets of a pair of upper and lower heating plates, a press plate and a cooling plate, a soaking plate installed on the surface of the mold mounting surface of each plate, and a pair of plates in each set are moved closer to or away from each other. Drive means for performing the heating, pressing and cooling processes, and control means for controlling the respective processes and conveyance of the mold, and the cooling plate Is composed of a plate body, a plurality of cartridge heaters embedded in the plate body at predetermined intervals, and a plurality of thermocouples installed in the vicinity of each cartridge heater, and further each of the thermocouples Output control means for independently feedback-controlling the output of each cartridge heater based on the output.

  The optical element molding method of the present invention uses the optical element molding apparatus of the present invention to store an optical material in the mold and heat the mold to soften the optical material in the mold. And a pressing process in which the softened optical material is pressed by the mold using a press plate to give an optical element shape, and after the pressing process, the mold is cooled to provide an optical material having an optical element shape. A cooling process for solidifying the optical element, wherein in the cooling process, the output control means independently feedback-controls the output of each cartridge heater based on the output of each thermocouple. It is characterized by.

  According to the optical element molding apparatus and the molding method of the present invention, the temperature distribution generated in the cooling plate can be reduced in the production of the optical element, the shape accuracy of the optical element can be improved, and the optical element can be produced stably with a high yield. .

It is a schematic block diagram of the shaping | molding apparatus of the optical element which is one Embodiment of this invention. It is (a) plane perspective view and (b) side perspective view of the cooling plate used for the shaping | molding apparatus of FIG. It is (a) plane perspective view and (b) side perspective view of the temperature distribution measuring means of a cooling plate. It is a schematic block diagram of the shaping | molding apparatus of the optical element which is embodiment provided with two or more heating stages and cooling stages of this invention. It is a plane perspective view of the cooling plate in the second embodiment of the present invention (heater heating lines are also shown). It is the figure which showed the temperature distribution of the 2nd cooling plate (upper) of Example 1-1 and Comparative Example 1. FIG. It is the figure which showed the temperature distribution of the 2nd cooling plate (lower) of Example 1-1 and Comparative Example 1. FIG. It is the figure which showed the temperature distribution of the 2nd cooling plate (upper) of Example 1-2 and Comparative Example 1. FIG. It is the figure which showed the temperature distribution of the 2nd cooling plate (lower) of Example 1-2 and Comparative Example 1. FIG. It is the figure which showed the data of the optical element shape of Example 1-1. It is the figure which showed the data of the optical element shape of Example 1-2. It is the figure which showed the data of the optical element shape of the comparative example 1. It is the figure which showed the data of the optical element shape of Example 2-1. It is the figure which showed the data of the optical element shape of Example 2-2. It is the figure which showed the data of the optical element shape of the comparative example 2.

  Hereinafter, the present invention will be described in detail.

(First embodiment)
FIG. 1 is a schematic configuration diagram of an optical element molding apparatus according to an embodiment of the present invention (only a chamber 2 is shown in cross section).

  An optical element molding apparatus 1 according to the present invention softens an optical material by heating a chamber 2 serving as a molding chamber for molding the optical element and a mold containing the optical material provided in the chamber 2. It has a heating stage 3, a press stage 4 for press-molding the heat-softened optical material, and a cooling stage 5 for cooling the optical material to which an optical element shape is given by press molding.

  Here, the chamber 2, which is a molding chamber, provides a place for performing an optical element molding operation. The chamber 2 is provided with an inlet for taking in the optical element molding die 50 and an outlet for taking out the molding die 50 after the molding of the optical element is finished. An intake shutter 6 and an extraction shutter 7 are provided. The mold 50 can be taken in and out of the chamber 2 by opening and closing these shutters as necessary, and the atmosphere in the chamber 2 is maintained. In addition, the mold inlets 8 and 9 are provided at the inlet and the outlet, respectively, on which the molding die 50 can be placed outside the chamber 2.

  Inside the chamber 2, a heating stage 3, a press stage 4 and a cooling stage 5 for molding the optical element are provided, and a molding operation is performed by each of these stages. Actually, the molding die 50 containing the optical material is taken into the chamber 2 from the intake port, moved in order while being subjected to predetermined processing in each of the above stages, and when the predetermined processing is completed, the molding die 50 is completed. Is taken out of the chamber 2 from the take-out port.

  Inside the chamber 2, the mold 50 softens the optical material and facilitates deformation, and is heated to a high temperature. Therefore, the atmosphere in the chamber is inert gas such as nitrogen so that the mold 50 is not oxidized. Can be an atmosphere. This inert gas atmosphere can be achieved by replacing the internal atmosphere with the chamber 2 as a sealed structure. However, the chamber 2 has a semi-closed structure, and the inert gas is constantly supplied into the chamber 2 so that the chamber is positively pressurized. However, an inert gas atmosphere may be maintained by preventing external air from flowing in. The intake shutter 6 and the extraction shutter 7 described above are effective for making the inside of the chamber 2 a semi-sealed state with a simple configuration. The chamber 2 and the shutters 6 and 7 are preferably made of a material that does not precipitate gas and impurities at high temperatures such as stainless steel and alloy steel.

  Next, each stage that performs the molding operation of the present invention will be described. Note that the mold 50 used to describe each stage is generally a set of molds composed of an upper mold that forms the upper optical surface of the optical element and a lower mold that forms the lower optical surface. Furthermore, it has a body mold for aligning the upper mold and the lower mold. The body mold is a hollow cylindrical inner cylinder that regulates the optical axis of the upper mold and the lower mold on the same axis during pressing, and a hollow cylindrical shape that is provided on the outer periphery of the inner cylinder and regulates the distance between the upper mold and the lower mold It is preferable that the outer shell of the present invention is constituted.

  The mold 50 is made of a material such as cemented carbide or ceramics, and the upper mold and the lower mold each have a molding surface for transferring the surface shape of the optical element to be molded. The shape of the optical element formed may be a mold that molds any lens shape of biconvex, biconcave, plano-convex, plano-concave, convex meniscus, or concave meniscus. In the case of using an outer shell, a material having durability at high temperatures, corrosion resistance, and high mechanical strength is preferable, and a material having a high thermal expansion coefficient is preferable, specifically, stainless steel such as SUS. It is preferable to do.

  The heating stage 3 of the present invention is composed of a pair of upper and lower heating plates 3b in which an optical material accommodated in a mold 50 is softened and a cartridge heater 3a is embedded therein. The heating plate 3b can heat the upper die and the lower die by bringing the pair of upper and lower heating plates 3b into contact with the upper die and the lower die of the molding die, and further the optical housed in the molding die. The material can also be heated.

  More specifically, in the heating stage 3, the lower heating plate 3b is fixed to the bottom plate of the chamber 2 by laminating the heat insulating plate 3c and the heating plate 3b having a soaking plate on the surface in this order, The heat of the lower heating plate 3 b is not transferred to the chamber 2.

  The upper heating plate 3b can be moved up and down, and it also has a soaking plate on the surface, and the shaft 3d is provided via the heat insulating plate 3c so as not to transmit the heat of the upper heating plate 3b itself. The shaft 3d can move the heating plate 3b up and down by a cylinder (not shown). In this way, if the heating plate 3b can be moved up and down, contact / non-contact of the upper heating plate 3b with the upper die of the molding die 50 can be controlled, and the molding die 50 and the optical material can be heated at a desired timing. .

  In the press stage 4 of the present invention, the distance between the upper and lower press plates 4b is reduced to reduce the distance between the upper mold and the lower mold of the mold 50, and the optical material accommodated in the mold 50 is pressed in a softened state. Then, the optical element is molded by imparting molding surface shapes of the upper mold and the lower mold to the optical material. It consists of a pair of upper and lower press plates 4b in which a cartridge heater 4a is embedded. The press using the press plate 4b is performed while maintaining the previous heating temperature.

  More specifically, in this press stage 4, the lower press plate 4 b is fixed to the bottom plate of the chamber 2 by laminating a heat insulating plate 4 c and a press plate 4 b having a soaking plate on the surface in this order. The heat of the lower press plate 4 b is not transferred to the chamber 2.

  The upper press plate 4b can move up and down, and it also has a heat equalizing plate on the surface, and the shaft 4d through the heat insulating plate 4c so as not to transmit the heat of the upper press plate 4b itself. The shaft 4d can move the press plate 4b up and down by a cylinder (not shown). In this way, if the press plate 4b can be moved up and down, the upper press plate 4b can be lowered and press molding using the molding die 50 placed on the lower press plate 4b can be performed. At this time, press molding can be performed at a predetermined pressure, and the optical element shape can be imparted to the optical material with high accuracy.

  The cooling stage 5 of the present invention cools the mold 50 and also cools and solidifies the optical material to which the optical element shape has been imparted. Therefore, the cooling stage 5 includes a pair of upper and lower cooling plates 5b in which cartridge heaters 5a are embedded. Composed. The cooling plate 5b can cool the upper mold and the lower mold by bringing the soaking plates installed on the pair of upper and lower cooling plates 5b into contact with the upper mold and the lower mold of the mold, respectively. The contained optical material can also be cooled.

  More specifically, in this cooling stage 5, the lower cooling plate 5 b is fixed to the bottom plate of the chamber 2 by laminating a heat insulating plate 5 c and a cooling plate 5 b having a heat equalizing plate on the surface in this order. The heat of the lower cooling plate 5 b is not transmitted to the chamber 2.

  The upper cooling plate 5b can be moved up and down, and it also has a soaking plate on the surface, and the shaft 5d via the heat insulating plate 5c so as not to transmit the heat of the upper cooling plate 5b itself. The shaft 5d can move the cooling plate 5b up and down by a cylinder (not shown). In this way, if the cooling plate 5b can be moved up and down, contact / non-contact of the upper cooling plate 5b with the upper mold of the mold 50 can be controlled, and the mold 50 and the optical material can be cooled at a desired timing. it can.

  The solidification of the optical material here may be performed by cooling to the glass transition point or less of the material, more preferably to the strain point or less. When sufficiently cooled, the shape of the optical element of the optical material is stabilized and the deformation is suppressed. Is done. Cooling here refers to lowering to a temperature at which the optical material is solidified so as to stably impart the optical element shape, and the temperature is only about 50 to 150 ° C. lower than the press plate, and is still high. For this reason, the heater 5a is embedded in the cooling plate 5b.

  Further, the heating plate 3b, press plate 4b and cooling plate 5b on the upper side of each stage are fixed to the shaft through the heat insulating plate as described above, and this shaft is connected to the cylinder. The cylinder is not limited as long as each plate can be moved up and down. For example, an air cylinder, an electric servo cylinder, a hydraulic cylinder, an electric hydraulic cylinder, or the like is used.

  The heating plate 3b, the press plate 4b, and the cooling plate 5b described above have a horizontal contact surface with the mold, and in particular, the press plate 4b has a tilted contact surface with the press plate 4b. In such a case, the central axes of the upper mold and the lower mold of the mold 50 may not coincide with each other, and the optical element manufactured at this time may have a defective product because the optical axes thereof do not coincide with each other. Therefore, the management of the parallelism and flatness of the plates at each stage is strictly performed.

  In each of these stages, the plate is inserted into a material such as stainless steel, cemented carbide or alloy steel, and the cartridge heater is inserted and fixed. By heating the cartridge heater, the plate temperature is raised and maintained at a desired temperature. To do.

  And the cooling plate 5b used for this invention is comprised by the plate main body 5b (1) and the soaking | uniform-heating board 5b (2) installed in the shaping | molding die mounting surface surface of a plate like other plates, The plate This has a plurality of cartridge heaters 5a embedded in the horizontal direction at predetermined intervals, but the other plate is provided with only one thermocouple for managing the plate temperature. The plate 5b is provided with a thermocouple 5e installed in the vicinity of each cartridge heater for one cartridge heater (FIG. 2). Here, one thermocouple is provided for each cartridge heater, but the number of thermocouples is not limited to one as long as each cartridge heater can be controlled individually. The cartridge heater 5a is usually provided with its long axis aligned in a direction perpendicular to the inlet / outlet direction (conveying direction).

  Further, in order to independently set the temperature of each cartridge heater 5a to a predetermined temperature, an output control means for feeding back the measured output of the thermocouple 5e and adjusting the output individually for each heater ( (Not shown) is provided. This output control means determines whether or not the thermocouple 5e is within a predetermined range with respect to the set value based on the output value obtained when the thermocouple 5e receives heat from the cartridge heater 5a. Adjust the output of the cartridge heater to be within the range. The determination of the set value will be described later.

  As feedback control, a known control method may be used, and for example, a control method such as PID control may be used. More specifically, in the present invention, it is only necessary to stably control the output of the heater, and SSR control, SCR control, and the like are preferable.

  In setting the output for each cartridge heater, first, the temperature distribution measuring means for measuring the temperature distribution of the plate is attached instead of the soaking plate 5b (2) of the cooling plate 5b before the molding is started to know the heating state. It starts from here. An example of a specific configuration of the temperature distribution measuring means is shown in FIG. The temperature distribution measuring plate 10 is composed of a flat plate plate on which thermocouples 10a and 10b are arranged corresponding to the position where the mold is placed.

  The thermocouple 10a is provided at a position corresponding to the center portion of the molding die to be placed, and the thermocouple 10b is provided to the outer peripheral portion of the molding die. The thermocouple 10b provided on the outer peripheral portion is preferably provided at a plurality of locations along a circle centering on the central portion. For example, the thermocouples 10b in the outer peripheral portion may be provided at least at four locations on the inlet side and the outlet side in the conveyance direction of the mold and on the left side and the right side in the conveyance direction so that they are equally spaced. At this time, the temperature distribution measuring means uses a material such as stainless steel, cemented carbide, alloy steel or the like. The material of the temperature distribution measuring means may be the same as or different from the soaking plate. The thickness may be the same as that of the soaking plate, 3 to 15 mm, and the thermocouple is provided at a depth of 0.5 to 1.5 mm from the surface in contact with the mold.

  Further, more than four thermocouples may be arranged on the circumference, and additional thermocouples may be arranged on a circle concentric with the circle. In FIG. 3, thermocouples are added between the central portion and the entrance side in the transport direction, and between the center portion and the exit side in the transport direction, respectively, and the temperature distribution can be finely examined along the transport direction.

  Moreover, the heat insulating plates 3c, 4c, 5c of each stage may be a known heat insulating plate such as ceramics, stainless steel, die steel, high-speed steel, etc., which has high hardness and is difficult to be deformed by pressure during press molding. Ceramics that do not generate a large amount are preferred. The soaking plate of each stage has a well-known heat resistance such as cemented carbide or stainless steel, and a material having high hardness and good heat conduction can be used. It is preferable to coat the surface of the soaking plate with an anti-oxidation film, and specifically, a coating treatment of CrN, TiN, TiAlN, or the like can be given.

  The heating stage 3, the press stage 4, and the cooling stage 5 described above form a place (stage) where predetermined processing is performed, and the molding die 50 is provided with a conveying means so that the processing by each stage can be performed sequentially and smoothly. (Not shown) is controlled by the control means so as to be transferred to and mounted on each stage at a predetermined timing.

  More specifically, the processing by the heating plate 3b, the press plate 4b, and the cooling plate 5b is performed while the mold 50 is sequentially transported and moved onto each plate in the above order. Then, since the mold 50 is moved to the next stage, the processed stage is vacant, and further, the mold 50 containing another optical material is transported there, and a plurality of optical elements are continuously provided. It is efficient to perform the molding operation.

  Although the conveying means for performing this processing is not shown in the figure, for example, a robot arm or the like can be cited, and thereby, a press from the mold mounting table 8 to the heating plate 3b, and from the heating plate 3b to the press plate 4b is performed. The plate 4b is moved to the cooling plate 5b, and the cooling plate 5b is moved to the mold mounting table 9.

  This control means also controls the temperature of the pair of upper and lower plates at each stage of heating, pressing, and cooling, the timing of vertical movement, etc., so that a series of molding operations can be performed smoothly and continuously. Control to do. At this time, the opening and closing of the taking-in shutter and the taking-out shutter are also controlled. Furthermore, it is preferable to control the supply amount and timing of nitrogen so that the atmosphere in the chamber 2 is filled with an inert gas.

  In other words, the optical element molding apparatus 1 is an optical element molding apparatus that carries out a predetermined process while raising and lowering the temperature at one or more positions, by conveying a molding die.

  Next, an optical element molding method using the optical element molding apparatus 1 will be described.

  First, prior to the molding operation, the heating plate, the press plate, and the cooling plate are set as temperature conditions in the molding operation. And the temperature distribution of the cooling plate 5b is measured using the temperature distribution measuring plate 10 shown in FIG. The temperature distribution measuring plate 10 is used in place of the soaking plate 5b (2) of the cooling plate 5b, and the difference in temperature within the plate can be determined by looking at the output difference from each thermocouple. I can understand the situation. The temperature distribution may be measured by superimposing the temperature distribution measuring plate 10 on the soaking plate 5b (2) without replacing the temperature soaking plate 5b (2).

  In the optical element molding apparatus 1 of FIG. 1, a press plate 4b is adjacent to the mold entrance side of the cooling plate 5b. Since this press plate 4b is hotter than the cooling plate 5b, the entrance side is heated. easy. On the other hand, there is no heating source on the mold exit side of the cooling plate 5b, and there is only a mold exit, so that it is difficult to be heated. Therefore, in general, in the cooling plate, the temperature tends to decrease from the press plate side toward the outlet side. This also applies to some extent when a plurality of cooling plates as will be described later are provided to cool the optical element in stages.

  Next, the set value of the cartridge heater is independently determined for each one so that the temperature distribution of the temperature distribution measuring plate 10 is symmetric. In order to make the temperature distribution symmetric, as described above, the temperature is high at the mold inlet side of the cooling plate and the temperature is low at the mold outlet side. To increase the output of the cartridge heater on the outlet side. Since only the temperature distribution in the inlet / outlet direction (conveyance direction) can be adjusted by this method, the temperature distribution in the direction perpendicular to the inlet / outlet direction (left / right direction) is measured in advance, and the same temperature distribution as that temperature distribution. The temperature distribution in the inlet / outlet direction is adjusted (see measured values in Example 1-1 described later, see FIGS. 6 and 7).

  The heater set value may be adjusted only once. However, after the adjustment, the temperature distribution may be measured again, and the adjustment to reduce the temperature distribution may be repeated a plurality of times. It is preferable in that the temperature state of the cooling plate can be made more symmetric. When the set value for each cartridge heater is determined by the above adjustment, the temperature distribution measuring plate 10 is removed, a soaking plate is attached, and the optical element molding operation described below is started.

  First, the molding die 50 is placed on the molding die placing table 8 on the inlet side, and the optical material is accommodated in the molding die 50. The intake shutter 6 is opened to open the intake port, and the mold 50 is conveyed onto the heating plate 3b by the conveying means. When conveyed, the lower mold of the mold 50 is heated to the same temperature as the heating plate 3b because it contacts the lower heating plate 3b. At the same time, the upper die is brought into contact with the upper heating plate 3b from above and heated similarly.

  When the upper mold and the lower mold are heated in this way, the optical material housed therein is also heated, and when this optical material is heated above the yield point, the deformation becomes easy. Generally, the heating temperature is set to a temperature between the yield point (At) and the softening point because the lens surface becomes clouded when the temperature is raised to the softening point. At this time, the temperature rising rate is preferably about 0.5 to 2.5 ° C./sec.

  In this way, the mold 50 and the optical material sufficiently heated by the heating stage 3 are conveyed and placed on the lower press plate 4b by the conveying means.

  The press plate 4b is also heated to the same temperature as the heating plate 3b, so that the optical material is maintained in a softened state. Furthermore, by lowering the upper press plate 4b and reducing the distance between the press plates 4b, the distance between the upper die and the lower die is reduced, and pressure is applied to the optical material housed in the forming die 50, Deform optical material.

  In this pressing step, as described above, the optical material is press-molded by applying pressure from above and below the mold 50, whereby the optical forming surfaces of the upper mold and the lower mold are transferred to the optical material, and the optical element shape Is granted.

In the press in this pressing step, the heating temperature is about the same as the temperature heated in the preceding heating stage, and the pressure during pressing is 2.5 to 37.5 N / mm ² per unit area of the lens molded body. For example, 10 to 20 N / mm ² is particularly preferable.

  And by performing such a press process, the shaping | molding die 50 by which the press cut was completed is conveyed from the press plate 4b to the cooling plate 5b by a conveyance means. This transport means is the same as the transport means described above.

  Next, the mold 50 is cooled by the cooling plate 5b. This is similar to the above heating step. The lower mold is the lower cooling plate 5b, and the upper mold is the upper cooling plate 5b lowered and brought into contact. Cool by. This cools and solidifies the optical material. This cooling is preferably performed below the glass transition point (Tg) of the optical material, and more preferably to a temperature below the strain point of the optical material. At this time, the cooling rate is preferably 0.1 to 2.5 ° C./sec, more preferably 0.5 to 1.0 ° C./sec.

  The heating plate 3b, the press plate 4b, and the cooling plate 5b all have a thermocouple embedded therein, and the output from the thermocouple is fed back to control the output of the cartridge heater to maintain a predetermined plate temperature. . Unlike the other plates, the cooling plate 5b is provided with a thermocouple corresponding to each cartridge heater, and has a set value determined for each cartridge heater based on the temperature distribution measurement process described above. Thus, the output from the thermocouple is fed back to control the cartridge heater output.

  In the heating process and the cooling process described above, it is preferable to gradually increase or decrease the temperature by changing the temperature stepwise, and by providing one or more heating stages, the temperature of the optical material is increased stepwise. Is raised to reach the molding temperature in the heating stage immediately before the press stage. Also, in the cooling process, by providing one or more cooling stages, the temperature of the optical material is lowered stepwise so as to reach a temperature of 200 ° C. or lower. As described above, when heating and cooling are performed step by step, a rapid temperature change of the optical material can be suppressed, and molding can be performed without deteriorating the characteristics of the optical element such as distortion or surface cracking.

  FIG. 4 shows an example of an optical element molding apparatus having a plurality of heating stages and cooling stages in order to perform such a heating process and a cooling process. The optical element molding apparatus 11 shown in FIG. 4 includes a chamber 12, a first heating stage 13, a second heating stage 14, a third heating stage 15, a press stage 16, a first cooling stage 17, and a first cooling stage 17. 2 has a cooling stage 18 and a third cooling stage 19, and in the chamber 12, as in the optical element molding apparatus 1, an inlet for the molding die 50 and an intake shutter that can be opened and closed. 20, a take-out port and a take-out shutter 21 that can be opened and closed, and mold holders 22 and 23 are provided outside the take-in port and the take-out port. The third cooling stage 19 is water-cooled, and no heater is provided.

  The optical element molding apparatus 11 has the same configuration as the optical element molding apparatus 1 in FIG. 1 except that three heating stages and three cooling stages are provided to perform heating and cooling step by step. It is the same. The cooling plate 18b is provided with the same number of thermocouples as the number of cartridge heaters, similarly to the cooling plate 5b of FIG.

  In the first heating stage 13, preheating is performed in which the optical material is once heated to a temperature lower than the glass transition point and about 200 to 400 ° C., and in the second heating stage 14, the temperature is increased to a temperature near the glass transition point. The heating stage 15 is heated to a yield point of +10 to 30 ° C. The press stage 16 gives an optical element shape by a molding operation while maintaining the molding temperature, and the first cooling stage 17 cools the glass to the glass transition point + 20 ° C. of the optical material, and the second cooling. The stage 18 is further cooled to a strain point or lower, and the third cooling stage 19 is cooled to a temperature of 200 ° C. or lower at which the mold is not oxidized.

  Here, the third cooling stage can efficiently cool the plate to be used as a water-cooled plate provided with piping so that cooling water circulates instead of the heater in the other stages.

  In the optical element molding apparatus 11, the influence between adjacent plates is large when the temperature of the adjacent plates is high in the cooling stage for cooling the optical elements, and the cooling of a part of the optical elements is delayed. If the cooling becomes non-uniform in this way, distortion occurs in the optical element due to the difference in the cooling rate, or the mold release cannot be performed well, which adversely affects the characteristics of the obtained optical element. In particular, in the second cooling plate 18b, the adjacent third cooling plate 19b has a large influence because of water cooling, and thus independent control is preferable. In addition, since the influence between the press plate 16b and the first cooling plate 17b may adversely affect the shape accuracy of the optical element, the cartridge heaters 17a of the first cooling plate 17b are controlled independently for each one. It is preferable to do this.

  Also, between the heating stage and between the heating stage and the press stage, the effect of causing a problem is smaller than that of the cooling stage, but the cartridge heaters in the same plate are also independent so that the predetermined processing can be performed at a uniform temperature. It is preferable to control automatically.

  The optical element obtained by cooling is then subjected to centering of the surplus portion to form an optical element shape, or subjected to an annealing process to remove distortion, etc., in order to obtain an optical element shape. The final product is processed.

  Thus, by controlling each cartridge heater independently, the temperature difference produced in the conveyance direction by being influenced by the temperature of the adjacent plate can be reduced, and the temperature distribution in the plate can be improved.

(Second Embodiment)
The present embodiment has the same configuration as that of the first embodiment except that the configuration of the cartridge heater disposed in the cooling plate is different. Therefore, only this difference will be described below.

  The cooling plate used in this embodiment is shown in FIG. The cooling plate 25b is the same as the cooling plate 5b in that three cartridge heaters are arranged in the horizontal direction with a certain interval in the horizontal direction. Although not shown, it is the same as the cooling plate 5b in that one thermocouple is provided for one cartridge heater.

  However, of the cartridge heaters embedded in the cooling plate 5b, the two heater cartridges 25a arranged on the outside are ordinary cartridge heaters that are the same as those in the first embodiment. The feature of the invention in this embodiment is the cartridge heater 25c in the middle.

  That is, a normal cartridge heater is configured to be able to generate heat evenly in all rod shapes, but in this embodiment, even in the heater cartridge, by providing a portion with a high watt density and a small portion, it is non-uniform. Use one that can generate heat.

  More specifically, as shown in FIG. 5, the portion corresponding to the outer periphery of the plate of the middle cartridge heater has a high watt density in the same manner as a normal cartridge heater, and the watt density is low at the center of the plate. To do. FIG. 5 schematically shows a heating wire inside the heater (shown by a solid line), but shows a cartridge heater having a watt density of 0 at the center. In addition, even if the watt density of the central part is not 0, it may be 0 to 40% lower than the outer peripheral part. Hereinafter, the cartridge heater is referred to as a countermeasure heater.

  By setting it as the cooling plate which has such a specific structure, the temperature of the plate center part which is easy to be heated is not made high temperature more than necessary. Further, by adopting such a configuration, it is possible to adjust the plate temperature in the transport direction by independently controlling the cartridge heaters in accordance with the temperature of the central portion, similarly to the first embodiment, and by the cartridge heater 25c. The plate temperature in the left-right direction with respect to the transport direction can also be adjusted to the center of the plate by adjusting the output of the cartridge heater. That is, the above embodiment is extremely effective for improving the temperature distribution on the plate.

  In this regard, in the first embodiment, although the temperature distribution in the transport direction can be improved, it is difficult to improve the temperature distribution in the left-right direction with respect to the transport direction, and the temperature at the center of the plate tends to increase. However, in the present embodiment, the temperature distribution improving effect further extends in the left-right direction with respect to the conveying direction, and the temperature of the entire plate can be equalized. In other words, the temperature distribution in the left-right direction can be reduced by the countermeasure heater, and the temperature distribution in the conveyance direction can be matched to the temperature distribution in the left-right direction by individual control of the heater, so that the overall temperature distribution can be reduced (described later). (Measured values of Examples 1-1 and 2-1, see FIGS. 6 to 9).

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Example 1-1)
The optical element was molded as follows using the optical element molding apparatus 11 of FIG.

  The optical element molding apparatus 11 used here uses, as a heat plate, a heat plate, a press plate, and a cooling plate, a stainless steel plate of 100 × 78 × 18 mm and three 500 W cartridge heaters inside. 100 × 78 × 9 mm plate made of SUS304 and 100 × 78 × 9 mm plate made of zirconia are superposed, and 100 × 78 made of cemented carbide made of tungsten carbide as a soaking plate. A × 5 mm plate was used. In addition, one thermocouple is embedded in one cartridge heater only in the second cooling plate 18b, and one thermocouple is embedded in the center of the plate for the other cooling plates as before. The temperature was controlled. The embedded position of the thermocouple is a position of 1.5 mm from the cartridge heater to the contact surface side with the mold.

  The cylinder that moves the upper plate up and down uses an air cylinder, and a shaft having a shaft diameter of 40 mm is connected and fixed to the upper plate. The chamber was a 440 × 592 × 240 mm box made of SS400, and the lower plate of this chamber was 440 × 592 × 20 mm.

  The mold 50 is composed of an upper mold, a lower mold, and a trunk mold having an inner cylinder and an outer cylinder. The upper mold, the lower mold, and the inner cylinder are made of cemented carbide made of tungsten carbide, and the outer cylinder is made of SUS. Thus, by press molding, a biconvex molded product having a diameter of 40 mm, a center thickness of 7.5 mm, a peripheral thickness of 3 mm and an aspherical surface with approximate curvature radii of 100 mm and 85 mm, respectively, is obtained, and the post-processing is centered. Thus, an optical element having a diameter of 35 mm was obtained.

  First, prior to the molding operation, the soaking plate of the second cooling plate 18b is replaced with the temperature distribution measuring plate 10 shown in FIG. 3, and the heating plate, the press plate, and the cooling plate are set as temperature conditions in the molding operation. When the temperature became stable, the temperature detected by each thermocouple of the temperature distribution measuring plate was measured. At this time, four thermocouples of the temperature distribution measuring plate are provided on the circumference having a radius of 20 mm and two on the circumference having a radius of 10 mm, centering on the thermocouple in the center portion. The material and size of the temperature distribution measuring plate are the same as the soaking plate.

  First, as the conventional example, the outputs of all the cartridge heaters of the second cooling plate 18b are made the same, and the temperature of the thermocouple corresponding to the middle cartridge heater is set as the set temperature of the plate. At this time, as a result of measuring the temperature of all the thermocouples for each of the upper and lower cooling plates, the upper plate has the highest center part, and both the inlet side and the outlet side in the transport direction are lower than the center part. However, the temperature difference between the inlet side and the outlet side was about 8 ° C. at a position 20 mm from the center and was not uniform (FIG. 6 (a) —dashed line). The lower plate has the highest temperature on the inlet side, then the lowest in the center and the outlet side, and the temperature difference between the inlet side and the outlet side is as high as 22 ° C at a position 20 mm from the center. (FIG. 7 (a) —dashed line). From this result, it was confirmed that the upper and lower cooling plates were both in a non-uniform heating state in the transport direction. On the other hand, the temperature in the left-right direction was 12 ° C. above the center and 5 ° C. below, but there was no temperature difference between the left and right, and the temperature distribution was symmetric (FIG. 6 (b) —dashed line). FIG. 7 (b) —dashed line; results at a position 20 mm from the center).

  Based on this temperature distribution measurement result, the setting value of each heater was set so that the temperature distribution in the conveyance direction matches the temperature distribution in the left and right direction, but the temperature at the center part was the same as before the improvement, The temperature difference between the inlet and outlet sides in the transport direction is improved by 1.7 ° C (Fig. 6 (a)-solid line) for the upper plate and 2.4 ° C (Fig. 7 (a)-solid line) for the lower plate. did it. Further, the temperature difference from the central portion was small in all of the transport direction and the left-right direction, and the temperature distribution was improved (FIG. 6 (b) —solid line, FIG. 7b—solid line).

  Next, a diameter φ of 36 mm, a center thickness of 8.83 mm, a peripheral thickness of 4.3 mm, and a radius of curvature of 90 mm and 60 mm, respectively, produced by grinding and polishing made of borosilicate glass on the molding surface of the lower mold of the mold 50 described above. An optical material of a biconvex spherical lens was placed. This optical material has a strain point of 495 ° C., a glass transition point (Tg) of 532 ° C., and a yield point (At) of 573 ° C.

  The molding die 50 containing the optical material is conveyed and placed on the first heating plate 13b by the conveying means, and at the same time, the upper first heating plate 13b is lowered and brought into contact with the upper die, and the molding die 50 and optical The material is heated for 300 seconds, and then transported and placed on the second heating plate 14b, and at the same time, the upper second heating plate 14b is lowered to contact the upper die, and the molding die 50 and the optical material are kept in contact for 300 seconds. Then, the upper mold third heating plate 15b is lowered and brought into contact with the upper mold, and the molding mold 50 and the optical material are heated for 300 seconds to be optical. The material was softened. The first heating plate 13b was set to 280 ° C., the second heating plate 14b was set to 500 ° C., and the third heating plate 15b was set to 600 ° C.

Next, the mold 50 was transported and placed on the press plate 16b, and the upper press plate 16b was lowered. The press pressure during the molding was 5 N / mm ² and the press time was 250 seconds. At this time, the temperature of the press plate 16b was 600 ° C.

  After pressing, the mold is conveyed and placed on the first cooling plate 17b, and at the same time, the upper cooling plate 17b is lowered to contact the upper mold and cooled for 300 seconds, and then the mold is moved to the second cooling plate. When the upper second cooling plate 18b is lowered and brought into contact with the upper mold, cooled for 300 seconds, and further, the forming mold is conveyed and placed on the third cooling plate 19b. At the same time, the upper third cooling plate 19b was lowered to contact the upper mold and cooled for 300 seconds. At this time, the first cooling plate 17b was set to 550 ° C., the second cooling plate 18b was set to 450 ° C., and the third cooling plate 19b was set to 20 ° C. (cooling water temperature).

  The optical material was cooled to room temperature, and when it was sufficiently cooled, it was removed from the mold and an optical element was obtained.

(Example 1-2)
As shown in FIG. 5 (b), the middle one of the three cartridge heaters embedded in the cooling plate 17b has a watt density of 0 in the central portion, and 30 mm on each side is 250 W. An optical element was obtained by the same operation as in Example 1-1, except that heat generation was possible.

  At this time, as for the temperature of the second cooling plate, in particular, the difference between the temperature in the left-right direction and the temperature in the central portion was smaller than before the improvement, and the temperature distribution was improved (FIGS. 8 and 9). Here, FIG. 8 shows the temperature distribution of the upper second cooling plate, and FIG. 9 shows the temperature distribution of the lower second cooling plate.

(Comparative Example 1)
An optical element was obtained by the same operation as in Example 1 except that a conventionally used cooling plate was used for the same output of the cartridge heater, and the temperature was controlled by one thermocouple (No. 1). The temperature distribution of the cooling plate 2 is as described in Example 1-1 as the conventional example, and specifically, the temperature distribution is shown by the broken lines in FIGS.

(Example 2-1)
An optical element is obtained by the same operation as in Example 1 except that a heating plate, a press plate, and a cooling plate having dimensions of 100 × 78 × 18 mm are used, and the number of cartridge heaters embedded therein is four. It was.

(Example 2-2)
As shown in FIG. 5 (b), in the middle of the four cartridge heaters embedded in the cooling plate 17b, the central portion 20mm is set to have a watt density of 0, and both sides 30mm are 250W. An optical element was obtained by the same operation as in Example 2-1, except that heat generation was possible.

(Comparative Example 2)
An optical element was obtained by the same operation as in Example 2-1, except that a conventionally used plate heater output was the same as the cooling plate, and the temperature was controlled by one thermocouple. .

(Test example)
About the shape of the optical element obtained by the Example and the comparative example, the difference | error with a design value was investigated by UA3P (the Panasonic Corporation make, brand name). FIG. 10 (Example 1-1), FIG. 11 (Example 1-2), FIG. 12 (Comparative Example 1), FIG. 13 (Example 2-1), The results are shown in FIG. 14 (Example 2-2) and FIG. 15 (Comparative Example 2), respectively. The error from the design value here refers to an error obtained by removing the spherical (curvature) component from the design value, and is data measured in the cross direction with the lens center as a reference. The cross direction measured at this time was measured so as to match the conveyance direction of the mold and the left-right direction (the direction perpendicular to the conveyance direction in the horizontal plane) in the molding operation of the optical element. Incidentally, the conveyance direction and the left-right direction here correspond to the conveyance direction and the left-right direction in the temperature distribution measurement plate described above.

  From these results, in Examples 1-1 and 2-1, in which the cartridge heater is independently controlled with respect to Comparative Examples 1 and 2 as the conventional example, the shape asymmetry is improved in the transport direction of the optical element. Further, in Examples 1-2 and 2-2 in which the watt density of the cartridge heater near the center of the plate is changed, the shape error between the transport direction and the left-right direction is further different from those in Examples 1-1 and 2-1. It was confirmed that the shape accuracy of the obtained optical element was greatly improved. In the above embodiment, the number of cartridge heaters to be independently controlled is three and four. However, the present invention is not limited to this, and the effect of the present invention can be obtained as long as the number is three or more.

  As described above, the optical element molding apparatus and molding method of the present invention eliminates the factor that makes the temperature of the molding die unstable in the production of the optical element, and reduces the temperature distribution in the molding die. The shape of the optical element is stabilized, and the yield can be improved.

  The optical element molding apparatus of the present invention is used when manufacturing optical elements continuously by press molding while sequentially moving a mold.

  DESCRIPTION OF SYMBOLS 1 ... Optical element shaping | molding apparatus, 2 ... Chamber, 3 ... Heating stage, 4 ... Press stage, 5 ... Cooling stage, 6 ... Taking-in shutter, 7 ... Taking out shutter, 8, 9 ... Mold mounting base, 10 ... Temperature distribution Measurement plate 50 ... mold, 3a, 4a, 5a ... heater, 3b ... heating plate, 4b ... press plate, 5b ... cooling plate, 3c, 4c, 5c ... insulation plate, 3d, 4d, 5d ... shaft, 5e ... thermocouple

Claims (8)

An optical element molding apparatus for sequentially molding a mold having an optical material placed between an upper mold and a lower mold to heating, press molding and cooling stages provided in a chamber to mold the optical element. ,
A pair of upper and lower heating plates, a press plate, and a cooling plate are mounted on each of the heating, press forming, and cooling stages, and the heating, press forming, and cooling processes are performed on the mounted forming dies, respectively. A plurality of sets of plates, a soaking plate installed on the surface of the mold mounting surface of each plate, and a process of heating, press forming and cooling by bringing a pair of plates in each set close to or apart from each other And a control means for controlling each process and the conveyance of the mold, and
The cooling plate is composed of a plate body, a plurality of cartridge heaters embedded in the plate body at predetermined intervals, and a plurality of thermocouples installed in the vicinity of each cartridge heater,
The optical element molding apparatus further comprises output control means for independently feedback controlling the output of each cartridge heater based on the output of each thermocouple. Prior to molding of the optical element, it is placed on the surface of the cooling plate and has a temperature distribution measuring means for measuring the temperature distribution on the plate,
The optical element molding apparatus according to claim 1, wherein the output control means controls the output of each cartridge heater based on a set value determined by measurement of the temperature distribution measuring means.   The temperature distribution measuring means is provided with thermocouples corresponding to positions where the mold is placed, and the thermocouple has a central portion of the mold and a plurality of locations on a circle centering on the central portion. The optical element molding apparatus according to claim 2, wherein the optical element molding plate is a flat plate.   The apparatus for molding an optical element according to claim 1, wherein the number of the cartridge heaters is three or more.   The cartridge heater provided inside the plate among the plurality of cartridge heaters has a watt density at a central portion lower than a watt density at both ends thereof. Optical element molding apparatus.   The optical element molding apparatus according to claim 5, wherein a watt density at a central portion of the cartridge heater provided inside the plate among the cartridge heaters is zero. A heating step of using the optical element molding apparatus according to any one of claims 1 to 6 to store an optical material in the mold and heating the mold to soften the optical material in the mold. Pressing the softened optical material with the mold using a pressing means to give an optical element shape; after the pressing process, cooling the mold and solidifying the optical material with the optical element shape A method of forming an optical element having a cooling step,
In the cooling step, the output control means independently feedback-controls the output of each cartridge heater based on the output of each thermocouple. Prior to the heating step, a temperature distribution measuring step of measuring the temperature distribution of the cooling plate by placing a temperature distribution measuring means on the surface of the cooling plate;
A set value determining step for independently determining the output of each cartridge heater so as to reduce the temperature distribution of the cooling plate based on the measurement result of the temperature distribution;
The optical element molding method according to claim 7, wherein the output of the cartridge heater in the cooling step is controlled so as to be the set value determined in the set value determining step.

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