JP2005170751A - Method and apparatus for forming glass lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus where a lens is obtained by a forming process which is not influenced by the variation of glass temperature derived from molds or device configuration and where a dent or a flaw at the mold is not caused. <P>SOLUTION: The apparatus is equipped with a barrel die 1, an upper die 3 and a lower die 4 moving up and down in the barrel die and having final lens face accuracy and a heating means 5 which can heat the upper die 3, the lower die 4 and a glass gob 11. The position and the pressure of the lower die 4 can be controlled by a load cell 6 to detect the pressure between the upper die 3 and the lower die 4 and by a pressurizing and moving means 10 which can perform a feed back motion by an instruction from the load cell. The upper die 3 is positioned with a gap of 0.1-0.3 mm approximately which may contact with the glass gob 11 at a glass transition point or higher. The glass lens is formed by moving the lower die 4 with formable timings such as a deformation point plus 20°C and the like detecting pressure generated from the thermal expansion of heated glass and the dies by the load cell 6 and grasping the glass viscosity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a glass lens molding method and a molding apparatus for heating a glass preform material and pressing it with a molding die to obtain an optical element such as a lens.

  Conventionally, as a glass lens molding method, a glass material is inserted and placed between a pair of upper and lower molding mold members, these are heated and temperature-controlled, and press molding is performed by an upper and lower mold finished to a mirror surface. Thus, a method of obtaining an optical element having a desired surface accuracy and optical function surface is implemented. In order to mold the lens, first, a glass material for molding is placed on the molding surface of the lower mold, and then the upper mold is lowered on the molding surface at an extremely low pressure. Then, with the glass material in contact with the upper and lower molds, the glass material and the molding die are heated to a temperature suitable for press molding to operate the pressurizing mechanism, and the glass material is passed through the upper mold with the pressure rod. Is pressed to mold the optical element. And it cools, applying a sufficient time pressure until a molding surface is transcribe | transferred to a glass raw material and the shape is hold | maintained with required surface precision after mold release. Then, it molds and takes out the shape | molded optical element (refer patent document 1).

  Also, a method has been proposed in which the pressure applied to the glass material is suppressed only by the weight of the upper mold in the step of bringing the glass material into contact with the upper and lower molds (see Patent Document 2).

  FIG. 3 is an explanatory view showing a conventional glass lens molding apparatus that heats a glass material in contact with an upper and lower mold.

In FIG. 3, the glass gob 11 on the molding surface of the lower mold 17 is heated by the induction heating means 5 from a temperature below the glass transition point of the glass gob 11 to a moldable temperature, and the heated glass gob 11 is molded into the upper mold 16. Press molding is performed between the surface and the molding surface of the lower die 17. In this method, the molding surface of the upper mold 16 and the glass gob 11 are brought into contact with each other without applying a substantial pressure for molding the upper mold at a temperature below the glass transition point. As shown in FIG. 5, the glass gob 11 can be brought into contact with the upper mold 16 and the lower mold 17 with a pressure about the weight of the upper mold by adopting a mold configuration in which a gap is provided at the upper end of the upper mold 16. The glass gob 11 is heated to a uniform temperature, and the possibility of cracking the glass gob 11 before ensuring molding and molding is eliminated.
JP-A-2-38329 JP-A-5-193959

  However, in the conventional configuration, the temperature of the glass gob itself is not monitored and the process is controlled, and the temperature is generally feedback controlled by looking at the temperature of the thermocouple charged in the mold. Therefore, in a system with one mold, depending on the installation state of the glass gob in the mold, when two or more molds are used, the mold temperature controlling them depends on the position of the thermocouple or the difference in the mold. The actual glass gob temperature will vary. Therefore, molding stability such as repeated shape accuracy may be deteriorated, or in severe cases, the glass may be pressed in a hard state and the mold may be damaged.

  In addition, when the glass gob is brought into contact with the upper and lower molds, pressure is applied to the mold, although it is the weight of the upper mold, so that molding of the lens may cause dents or scratches on the molding surface of the mold. There was a problem that the quality and mold life were reduced.

  The present invention solves such a conventional problem and keeps the mold molding surface scratched by maintaining a non-contact or almost no load state with the upper mold while the glass preform material is below the glass transition point. In addition, it is possible to avoid the occurrence of this phenomenon, and it is influenced by temperature variations due to mold differences, etc. by entering the final molding process while monitoring the glass viscosity in consideration of the thermal characteristics of the glass preform material. It is an object of the present invention to provide a glass lens molding method and molding apparatus that realizes stable glass lens molding.

  In order to achieve the above object, the glass molding method of the present invention comprises a step of placing a glass preform material between an upper mold and a lower mold, and the upper mold, the lower mold and the glass preform material around it. A molding method comprising a step of heating with a provided heating means and a step of press-molding the glass preform material by moving at least one of the upper mold and the lower mold, and is applied to the glass preform material The molding is performed while monitoring and controlling the load and grasping the viscosity state of the glass preform material.

  The present invention also includes a step of arranging a glass preform material between an upper mold and a lower mold, a step of heating the upper mold, the lower mold and the glass preform material with a heating means provided around the upper mold, the lower mold, A molding method comprising a step of press-molding the glass preform material by moving at least one of an upper mold and a lower mold, and initially, a load due to thermal expansion is not applied to the glass preform material. Heating is performed in a state where a gap of 0.1 to 0.3 mm is left between the glass preform material and the upper mold.

  The present invention also includes a step of arranging a glass preform material between an upper mold and a lower mold, a step of heating the upper mold, the lower mold and the glass preform material with a heating means provided around the upper mold, the lower mold, A molding method comprising a step of press molding the glass preform material by moving at least one of an upper mold and a lower mold, and a load due to thermal expansion is applied until the glass preform material reaches a glass transition point or higher. The glass preform material and the upper mold are heated so as to leave a gap of 0.1 to 0.3 mm.

  The present invention also includes a step of arranging a glass preform material between an upper mold and a lower mold, a step of heating the upper mold, the lower mold and the glass preform material with a heating means provided around the upper mold, the lower mold, A molding method comprising a step of press-molding the glass preform material by moving at least one of an upper mold or a lower mold, and the upper mold or the lower mold until the glass preform material reaches a glass transition point or higher. The position of the upper mold or the lower mold is controlled and moved so that the load applied to the glass preform material is no load or a load of 10 N or less.

  Further, the present invention is characterized in that press molding is carried out after detecting that the glass preform material has reached the moldable temperature beyond the yield point by the temperature measuring means.

  By this configuration, until the glass preform material to be molded reaches a temperature above the glass transition point, the temperature is raised without contacting the molding surface of the upper mold and contacts the molding surface when it reaches the glass transition point or higher. It is possible to know the yield point of the glass preform material by monitoring the viscosity of the glass preform material while controlling the gap with the glass preform material with almost no load on the upper mold. And, by controlling the timing of the press by temperature or time, etc., it is possible to realize a stable reproduction of the molding process, and the glass gob contact with the molding surface of the upper mold is carried out at a temperature above the glass transition point, so There is no generation of scratches and scratches, and the life of the upper mold can be extended.

  Furthermore, the glass molding apparatus of the present invention includes a molding die having an upper die and a lower die, heating means provided around the molding die and the glass preform material, means for measuring the temperature of the molding die, It has pressurizing means for moving the mold and press-molding the glass preform material, and means for monitoring and controlling a load applied to the glass preform material.

  With this configuration, the temperature can be increased without contacting the molding surface of the upper mold until the glass preform material to be molded reaches a temperature above the glass transition point, and when the glass preform material exceeds the glass transition point. It is possible to know the yield point of the glass preform material by monitoring the viscosity of the glass preform material while controlling the gap with the glass preform material in contact with the molding surface and then with almost no load on the upper mold. And, it is possible to achieve stable reproduction of the molding process by controlling the timing of the press according to the temperature of the mold or the time after the yield point, and the contact of the glass preform material with the molding surface of the mold is the glass transition point. Since it is carried out at the above temperature, there is no occurrence of dents or scratches, and the life of the mold can be extended.

  As described above, according to the present invention, the press timing can be managed while grasping not only the temperature of the upper mold and the lower mold but also the viscosity state of the glass preform material to be molded, so that a stable molding process can be reproduced. It becomes possible.

  Moreover, the contact between the upper mold forming surface and the glass preform material is carried out when the glass preform material is at the transition point or higher, preventing the formation of dents and scratches caused by the glass preform material, and extending the life of the upper mold and the lower mold. It can also be extended.

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

(Embodiment 1)
FIG. 1 is a schematic diagram of a glass forming method and a forming apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, an upper mold 3 and a lower mold 4 which are molding dies (metal molds) are configured to slide inside the body mold 1. At the time of actual pressing, the lower mold 4 is operated by the pressure moving means 10. The molding chamber 2 can be shielded from the external air atmosphere, and is filled with an inert gas such as nitrogen in order to prevent the upper mold 3, the lower mold 4 and the internal member from being oxidized at a high temperature. An induction heating coil 5 is arranged on the outer periphery of the body mold 1 as induction heating means. Heating bodies 8a and 8b are arranged around the upper mold 3 and the lower mold 4 and generate heat by induction heating. The upper mold 3 and the trunk mold 1 are fixed by a support 12 through a heat insulating material 7a, and the lower mold 4 is attached to the lower shaft 9 through a heat insulating material 7b. The lower shaft 9 is moved up and down by the pressurizing / moving means 10, thereby enabling position control of the lower mold 4 and load control during pressing and heating. A load applied between the upper die 3 and the lower die 4 is detected by a load cell 6 installed on the upper portion of the upper die 3. The temperatures of the upper mold 3 and the lower mold 4 are measured by thermocouples 19a and 19b, respectively.

  In this embodiment, the induction heating coil is used as the heating means, but infrared rays such as a resistance heater and a halogen lamp may be used as the heat source.

  In the configuration shown in FIG. 1, the position of the lower mold 4 can be controlled and moved, and the position of the lower mold 4 can be controlled so that the upper mold 3 and the glass gob 11 do not contact during heating. Further, it is possible to feed back the detection result of the load generated from the contact due to the thermal expansion of the mold and the glass gob at the time of heating by the load cell 6 and hold the low load state of 0 to 5N (Newton) level while controlling the position. .

  Next, a glass lens molding process by the glass molding method and molding apparatus of the present embodiment will be specifically described. The glass glass type is VC81 (Tg: 510 ° C., At: 549 ° C.) manufactured by Sumita Optical Co., Ltd. A glass gob 11, which is preliminarily weighed to the final shape of the lens and whose lens effective surface is polished, is placed on the lower die 4, and the pressure moving means 10 lowers the gap with the upper die 3 to a position of 0.1 mm. The mold 4 is moved. This gap is set so that the upper mold 3 and the glass gob 11 do not come into contact with each other due to thermal expansion in a state below the glass transition point. The gap needs to be adjusted appropriately depending on the upper mold 3, the lower mold 4, the glass material, and the shape of the molded lens. In this non-contact state, the body mold 1, the upper mold 3, the lower mold 4, and the glass gob 11 are heated by the induction heating coil 5.

  FIG. 4 shows the difference in temperature rise time in each gap between the glass and the upper mold when the temperature is increased by heating under predetermined conditions.

  When the gap is 0.3 mm or more, the responsiveness of the glass temperature to the mold deteriorates and the temperature rise time becomes long.

  The induction heating coil 5 heats the heating bodies 8a and 8b installed on the outer peripheries of the upper mold 3 and the lower mold 4, and the body mold 1 and the upper mold 3 and the heat transfer from the heating bodies 8a and 8b. The lower mold 4 is heated. The glass gob 11 is heated by heat conduction from the lower mold 4 and radiant heat from the upper mold 3 and the trunk mold 1.

  When the glass gob 11 is above the glass transition point, contact with the upper mold 3 starts due to thermal expansion. As the temperature rises thereafter, the load detected by the load cell 6 also starts to increase. If the load before pressing is set to 5 N in advance, the position of the lower die 4 is moved downward by the feedback to the pressurizing / moving means 10 so that the set load 5 N is maintained. In this embodiment, the set load above the glass transition point is 5N, but this load value is set to 0N in the case of molds that need to be adjusted depending on the mold material or glass material and are easily damaged. Although it is carried out, in normal cases, no scratches or dents are observed even at the 5N level. As a result of the experiment, as shown in FIG. 5, no scratches or dents were observed up to a level of 10 N or less. Furthermore, when heating is continued, it can be detected that the thermal expansion suddenly decreases when a certain temperature is exceeded. This temperature is called the yield point inherent to glass and is a characteristic of any glass, although it varies depending on the material.

  FIG. 2 shows the thermal characteristics of general glass. In the case of optical glass, pressing at a temperature 20 to 30 ° C. above the yield point is considered desirable. In the case of this embodiment, pressing was started at 580 ° C., + 21 ° C. from the yield point. The press start timing is determined by monitoring the temperature measurement and the elapsed time after detecting the yield point.

  The glass lens thus obtained has a small variation in viscosity at the time of pressing due to temperature variations due to different molds or other causes, and thus stable repeatability can be secured.

  Further, the temperature difference between the upper and lower sides of the glass gob 11 due to non-contact is also moderated by the contact in the heating step up to the moldable temperature above the glass transition point in the gap setting range of 0.1 to 0.3 mm. 11 is heated almost uniformly. Even when the glass top and bottom temperature difference is made with a special lens shape, it can be avoided by giving the mold a top and bottom temperature difference during heating.

  Furthermore, according to the present embodiment, there is no contact of glass with the upper mold 3 in a state where the glass viscosity below the glass transition point is high, so that no dents or scratches were found on the mold. .

  The glass molding method and molding apparatus of the present invention can monitor and press the glass viscosity state, not the set value such as the mold temperature, etc., and the glass temperature varies depending on the mold and apparatus configuration. This makes it possible to realize a stable glass lens molding process. In addition, the glass that is heated and molded in a non-contact state with the upper mold is not subjected to a load in a high-viscosity state below the glass transition point, so there is no occurrence of dents or scratches on the mold. The effect of extending the life of the mold can also be expected.

Explanatory drawing which shows schematic structure of the glass forming apparatus in Embodiment 1 of this invention. Diagram showing the thermal characteristics of general glass Explanatory drawing which shows schematic structure of the conventional glass forming apparatus. Comparison of glass heating rate due to mold gap Diagram showing the state of generation of scratches, dents, cracks and bubbles

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body type | mold 2 Molding chamber 3 Upper mold | type 4 Lower mold | type 5 Heating means 6 Load cell 7 Heat insulating material 8 Heating body 9 Lower axis | shaft 10 Pressurizing / moving means 11 Glass gob 12 Support tool 13 Lower mold support tool 14 Upper mold support tool 15 Lower mold Holder 16 Upper mold 17 Lower mold 18 Gas vent hole 19 Thermocouple

Claims (6)

  Placing the glass preform material between the upper mold and the lower mold, heating the upper mold, the lower mold and the glass preform material with heating means provided around the upper mold and the lower mold; and the upper mold or the lower mold A molding method comprising a step of pressing at least one of the glass preform material and monitoring and controlling a load applied to the glass preform material to determine the viscosity state of the glass preform material. A glass lens molding method characterized by molding while grasping.   Placing the glass preform material between the upper mold and the lower mold, heating the upper mold, the lower mold and the glass preform material with heating means provided around the upper mold and the lower mold; and the upper mold or the lower mold Is a molding method comprising a step of press-molding the glass preform material by moving at least one of the glass preform material, and initially the glass preform material so that a load due to thermal expansion is not applied to the glass preform material. And heating the glass mold with a gap of 0.1 to 0.3 mm in the upper mold.   Placing the glass preform material between the upper mold and the lower mold, heating the upper mold, the lower mold and the glass preform material with heating means provided around the upper mold and the lower mold; and the upper mold or the lower mold A molding method comprising a step of press-molding the glass preform material by moving at least one of the glass preform and the glass so that a load due to thermal expansion is not applied until the glass preform material reaches a glass transition point or higher. A method for molding a glass lens, comprising heating the preform material and the upper mold with a gap of 0.1 to 0.3 mm.   Placing the glass preform material between the upper mold and the lower mold, heating the upper mold, the lower mold and the glass preform material with heating means provided around the upper mold and the lower mold; and the upper mold or the lower mold A molding method comprising a step of press-molding the glass preform material by moving at least one of the glass preform material from the upper mold or the lower mold until the glass preform material reaches a glass transition point or higher. A method of molding a glass lens, wherein the position of the upper mold or the lower mold is controlled and moved so that the load applied to the material is no load or a load of 10 N or less.   5. The method for molding a glass lens according to claim 1, wherein the glass preform material is subjected to press molding after detecting that the glass preform material has reached a moldable temperature beyond the yield point by temperature measuring means. .   A mold having an upper mold and a lower mold, a heating means provided around the mold and the glass preform material, a means for measuring the temperature of the mold, and the glass preform by moving the mold An apparatus for molding a glass lens, comprising pressurizing means for press-molding a material and means for monitoring and controlling a load applied to the glass preform material.

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