JP2006124193A - Method for shaping optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for shaping an optical element capable of improving a heating efficiency and obtaining a good quality optical element with an improved eccentricity precision by properly selecting a heating method based on the outer diameter and height of the shaping mold. <P>SOLUTION: In a method for shaping an optical element by press-molding an optical element material 8 by a pair of shaping molds 1a, 1b, the method includes a selecting process for selecting a mold bottom heating method which heats the optical element material 8 from the bottom of the shaping molds 1a, 1b or a mold side heating method which heats the optical element material 8 from the side of the shaping molds 1a, 1b based on the outer diameter a and the height b of the molds 1a, 1b, a heating process for heating the optical element material 8 by the heating method selected by the selecting process, and a pressing process for press-molding the optical element material 8 heated by the heating process by the shaping molds 1a, 1b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for molding an optical element for precision press molding of a high-precision optical element such as a spherical lens, an aspherical lens, and a prism used in an optical apparatus such as a camera, a video, a microscope, or a laser. The present invention relates to an optical element molding method capable of obtaining a good quality optical element by setting the shape of a molding die and selecting a heating method according to the shape and quality of a molded product, and performing efficient molding.

As a conventional optical element molding method and molding apparatus, for example, there is one proposed in Japanese Patent Laid-Open No. 2003-95673 (see Patent Document 1). This conventional optical element molding apparatus includes a pair of upper and lower molds (molding molds), a heat equalizing member installed on the bottom surface (rear surface) of each mold, and each heat equalizing member by a compression spring. It was the structure provided with the heat_generation | fever block which each contact | adhered. In the conventional optical element molding apparatus having such a configuration, the heat generating block is driven in a state where the glass material is sandwiched between a pair of upper and lower molds, and these molds are heated via a heat equalizing member, and then these molds are used. The glass material was pressure-molded with the molds relatively close to each other.
JP 2003-95673 A

  However, in the conventional optical element molding method described above, the bottom surface of each mold is heated by the heat generating block via the heat equalizing member regardless of the size and shape of the mold. For this reason, when the outer diameter of each mold is large and the height is low, the glass material sandwiched between the molds can be efficiently heated, but when the outer diameter of each mold is small and the height is high However, it took a considerable time until the glass material was heated, and there was a problem that the production efficiency was poor.

  The present invention has been made in view of the above problems, and by appropriately selecting a heating method based on the outer diameter and height of the mold, it is possible to improve heating efficiency and to achieve eccentricity accuracy. An object of the present invention is to provide an optical element molding method capable of obtaining a high-quality optical element that is improved.

  In order to achieve the above object, the optical element molding method of the present invention is an optical element molding method in which an optical element material is press-molded by a pair of molding dies, based on the outer diameter and height of the molding die, A selection step of selecting either a mold bottom surface heating method for heating the optical element material from the bottom surface side of the mold or a mold side surface heating method for heating the optical element material from the side surface side of the molding die; A heating process for heating the optical element material by a heating method selected in the process; and a pressing process for press-molding the optical element material heated in the heating process by the molding die.

  Preferably, in the selection step, when the height is smaller than the outer diameter of the mold, the mold bottom surface heating method is selected, and when the height is larger than the outer diameter of the mold, the mold Select the side heating method.

  Preferably, when the optical element material is heated by the mold bottom surface heating method, the heating step includes a first heating step of heating the molding die to a predetermined temperature lower than a molding die temperature during the pressing step, and the predetermined heating step. And a second heating step of heating the mold heated to the temperature to the mold temperature during the pressing step.

  Preferably, in the first heating step, the mold is heated at a predetermined speed to a predetermined temperature that is 10 to 40 ° C. lower than the mold temperature during the pressing step, and in the second heating step, the predetermined temperature is increased from the predetermined temperature. The mold is heated at a slower rate than the first heating process up to the mold temperature during the pressing process.

  According to the method for molding an optical element of the present invention, heating efficiency can be improved by appropriately selecting either the mold bottom surface heating method or the mold side surface heating method based on the outer diameter and height of the mold. In addition, it is possible to obtain a high-quality optical element with improved eccentricity accuracy.

  Hereinafter, a method for molding an optical element according to an embodiment of the present invention will be described with reference to the drawings. First, based on FIG.1 and FIG.2, the shaping | molding apparatus for implementing the shaping | molding method of this optical element is demonstrated. FIG. 1 is a schematic cross-sectional view showing an optical element molding apparatus for carrying out a mold bottom surface heating method in the optical element molding method according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing an optical element molding apparatus for carrying out the mold side surface heating method in the optical element molding method according to the present embodiment.

  In FIG. 1, the optical element molding apparatus for carrying out the mold bottom surface heating method is divided into three stages: a heating stage, a press stage, and a cooling stage. A mold set consisting of a pair of molds, upper mold 1a, lower mold 1b, sleeve 2, and glass material (optical element material) 8 is sequentially conveyed, and a heating process → press process → cooling process is performed at each stage. Like to do.

  Above and below the heating stage and the press stage, there are disposed an upper plate 3a and a lower plate 3b that are in contact with the bottom surfaces (rear surfaces) of the upper mold 1a and the lower mold 1b, respectively. An upper infrared heater 4a as a mold bottom surface heating means is disposed on the upper plate 3a, and similarly, a lower infrared heater 4b as a mold bottom surface heating means is disposed on the lower plate 3b.

  The upper infrared heater 4a for heating the upper mold 1a is provided with a thermocouple 10 as temperature detecting means, and a temperature regulator (not shown) is set to a set temperature based on the temperature detected by the thermocouple 10. The output of the upper infrared heater 4a is controlled. Similarly, the lower infrared heater 4b for heating the lower mold 1b is provided with a thermocouple 10 as temperature detecting means, and the temperature regulator is set to a set temperature based on the temperature detected by the thermocouple 10. The output of the lower infrared heater 4b is controlled. Each thermocouple 10 passes through the upper block 6a or the lower block 6b and detects the temperature of the upper plate 3a or the lower plate 3b.

  The upper and lower infrared heaters 4a and 4b are arranged in parallel and in a straight line so as to cross the upper plate 3a and the lower plate 3b. In this embodiment, the output of the upper and lower infrared heaters 4a and 4b is set to 200 V of 2000 W. Furthermore, the upper and lower infrared heaters 4a and 4b are respectively supported by the upper mirror 3a or the lower plate 3b by the reflecting mirror 5, and the reflecting mirror 5 reflects the light of the upper and lower infrared heaters 4a and 4b to improve the heating efficiency. I am letting.

  Here, the pair of upper mold 1a and lower mold 1b are inserted into a substantially cylindrical sleeve 2, and are slidable in the vertical direction while contacting the sleeve 2 with the side surface of the mold. As a pressurizing means for sliding the upper die 1a downward, a push rod 7 is provided on the upper block 6a. The push rod 7 is lowered to transmit a force from the upper block 6a to the upper die 1a to perform pressing. Both sides of the upper block 6a are mounted on the hooks 11, and the upper block 6a and the upper plate 3a are moved up and down by driving the hooks 11 up and down.

  A feed 9 is provided on the lower plate 3b to move and convey the upper mold 1a, the lower mold 1b and the sleeve 2 to the next process. By moving the feed 9 in the left-right direction in the figure, the upper mold 1a, the lower mold 1b and the sleeve 2 are conveyed to the position of the next process.

  In FIG. 2, the optical element molding apparatus for carrying out the mold side surface heating method is divided into three stages: a heating stage, a press stage, and a cooling stage, as in the optical element molding apparatus of FIG. The mold set in which the upper mold 1 a and the lower mold 1 b are inserted into the sleeve 2 is sequentially conveyed by the feed 9.

  The upper plate 3a and the lower plate 3b are arranged above and below the heating stage and the press stage in the same manner as the optical element molding apparatus of FIG. 1 described above. A substantially cylindrical furnace bed 12 is attached. The furnace table 12 is provided with one infrared heater 4c as a mold side surface heating means, and the temperature of the upper portion thereof is detected by the thermocouple 10. Based on the temperature detected by the thermocouple 10, the output of the infrared heater 4 c is controlled so that a temperature regulator (not shown) reaches a set temperature. A reflecting mirror 5 for condensing infrared light is fixed to the back surface of the infrared heater 4c.

  As in the optical element molding apparatus of FIG. 1 described above, both sides of the upper plate 3a to which the furnace table 12 is attached are mounted on the hooks 11, respectively. The plate 3a is moved up and down.

  Further, a push bar 7 is provided on the upper part of the upper plate 3a constituting the press stage. The upper mold 1a is moved downward by pressing the upper mold 1a through the upper plate 3a. Pressure is applied to the glass material 8 heat-softened between 1a and the lower mold 1b.

  In the cooling stage, a cooling port 13 is provided in a substantially cylindrical member having substantially the same shape and the same size as the furnace stand 12 described above, and cooling nitrogen is blown to the outer periphery of the side surface of the sleeve 2 constituting the mold set. It has become.

  Next, a method for molding an optical element according to the present embodiment will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional view of a mold set used in the optical element molding method according to the present embodiment. FIGS. 4A to 4D are molding simulations using a mold bottom surface heating method in the selection process of the optical element molding method according to the present embodiment. It is a graph and explanatory drawing which show the result of having performed. FIGS. 5A to 5D are graphs and explanatory views showing the results of the molding simulation performed by the mold side surface heating method in the selection process of the molding method of the optical element according to the present embodiment.

[Selection process]
In the selection step, either the mold bottom surface heating method or the mold side surface heating method is selected based on the outer diameter (diameter) and the center height of the cylindrical mold (upper mold 1a, lower mold 1b). Although not shown, the molding surfaces of the upper mold 1a and the lower mold 1b have a convex shape or a concave shape corresponding to the optical surface shape of a desired optical element (lens).

  First, using a model composed of an upper mold 1a, a lower mold 1b, a sleeve 2 and a glass material 8 as shown in FIG. 3, a molding simulation is performed by inputting conditions of an outer diameter (diameter) a and a center height b of the mold. I do.

  For example, when the outer diameter a of the mold is 10 mm and the height b is 20 mm, when the outer diameter a of the mold is 20 mm and the height b is 30 mm, when the outer diameter a of the mold is 20 mm and the height b is 20 mm, For 5 patterns when the outer diameter a of the mold is 20 mm and the height b is 10 mm, and when the outer diameter a of the mold is 30 mm and the height b is 20 mm, the glass material 8 is heated and pressed by the mold bottom surface heating method. And a case where the glass material 8 is heated and pressed by the mold side surface heating method, respectively.

  The set temperature of the mold at the time of the molding simulation is the same molding temperature under any conditions, for example, the glass transition temperature of the glass material 8. Also, the pressing time is the same for all conditions. FIG. 4 shows the result of the molding simulation performed by the mold bottom surface heating method, and FIG. 5 shows the result of the molding simulation performed by the mold side surface heating method.

  As shown in FIG. 4, in the case of the mold bottom surface heating method, efficient heating can be performed when a mold having an outer diameter larger than the center height of the mold is used. On the other hand, as shown in FIG. 5, in the case of the mold side surface heating method, efficient heating can be performed when a mold having an outer diameter smaller than the center height of the mold is used.

  That is, when using a molding die whose outer diameter is larger than the center height of the molding die, the mold bottom heating method is selected, and a molding die whose outer diameter is smaller than the center height of the molding die is used. In this case, heating can be performed efficiently by selecting the mold side surface heating method. Note that the outer diameter of the mold corresponds to the outer diameter of the lens to be molded.

  There are also the following methods for selecting the heating method. In order to improve the decentering accuracy of the lens to be molded (the amount of deviation between the optical axis of one lens surface and the optical axis of the other lens surface), It is necessary to increase the sliding distance with the inner surface of the sleeve. For example, when molding a high-precision product having an outer diameter of the lens of 10 mm or less and an inter-surface eccentricity accuracy of 5 μm or less, it is necessary to make the center height of the molding die larger than the outer diameter of the molding die. Select the side heating method. On the other hand, when molding a non-relatively high precision product with a lens outer diameter larger than 10 mm and an inter-surface eccentricity accuracy larger than 5 μm, the center height of the molding die is made smaller than the outer diameter of the molding die. That is, the mold bottom heating method is selected.

[Heating process in mold bottom heating method]
As described above, when molding a product having relatively low surface eccentricity accuracy (the surface eccentricity accuracy is larger than 5 μm) or a large outer diameter (larger than 10 mm), the molding is performed by the mold bottom surface heating method. . Specific examples are shown below.

  In FIG. 1, a glass material 8 (transition temperature about 500 ° C.) is sandwiched between upper and lower molds 1a and 1b, and upper and lower molds 1a and 1b are inserted into a sleeve 2 to constitute a mold set. The mold set is disposed on the lower plate 3b, and is sequentially conveyed to a heating stage, a press stage, and a cooling stage by a feed 9. Each stage is controlled to maintain a predetermined set temperature.

  The heating stage is set and maintained at a temperature lower by 10 ° C. to 40 ° C. than the temperature of 500 ° C. for forming the glass. When the mold set is transported to the heating stage by the feed 9, a feed completion signal is output to a control unit (not shown), and the control unit lowers the upper plate 3a to form the bottom surface of the upper mold 1a constituting the mold set. Contact. Thereby, the heat of the upper plate 3a heated to 460-490 degreeC is transmitted to the upper mold | type 1a, and this upper mold | type 1a is heated. On the other hand, the lower mold 1b is heated by the heat of the lower plate 3b heated by the lower infrared heater 4b.

[Pressing process in mold bottom heating method]
When the mold set is conveyed to the press stage by the feed 9 after the heating step described above, a feed completion signal is output to the control unit, and the control unit controls the upper plate 3a as in the case of the heating stage. Is brought into contact with the bottom surface of the upper mold 1a constituting the mold set. In the press stage, the heating temperature of the upper and lower infrared heaters 4a and 4b is set to the molding temperature of 500 ° C. When a sufficient time elapses to heat the upper and lower dies 1a and 1b to 500 ° C., the push rod 7 is lowered. The upper block 6a is pressed. The pressing pressure of the push rod 7 is about 0.5 to 3.0 kgf / mm ² . The upper block 6a can uniformly press the bottom surface of the upper die 1a in order to press the upper plate 3a in contact with the bottom surface of the upper die 1a.

  The press amount of the push rod 7 is managed by time. The push bar 7 is pressed for a set time and then ascends and retreats from the upper block 6a. Thereafter, the upper plate 3a immediately rises and retreats from the bottom surface of the upper mold 1a. When the retreat of the upper plate 3a is completed, the mold set is conveyed to the cooling stage by the feed 9.

[Cooling process in mold bottom heating method]
When the mold set is conveyed to the cooling stage by the feed 9 after the pressing step described above, a feed completion signal is output to the control unit, and as in the case of the heating stage and the press stage, the control unit The upper plate 3a is lowered and brought into contact with the bottom surface of the upper mold 1a constituting the mold set. The upper plate 3a and the lower plate 3b are cooled to a preset temperature in advance, and are cooled by absorbing heat from the bottom surfaces of the upper and lower molds 1a and 1b. Similar to the press stage, the push bar 7 presses the upper block 6a in the cooling stage.

[Heating process in mold side heating method]
On the other hand, when molding a product having relatively high surface eccentricity accuracy and a small outer diameter, molding is performed by a mold side surface heating method. Specific examples are shown below. In FIG. 2, a glass material 8 (a glass material having a transition temperature of about 380 ° C., a disk shape having an outer diameter of 20 mm and a thickness of 6 mm) is sandwiched between the upper and lower molds 1a and 1b, and the upper and lower molds 1a and 1b are inserted into the sleeve 2. Configure the type set. The mold set is disposed on the lower plate 3b, and is sequentially conveyed to the heating stage, the press stage, and the cooling stage by the feed 9 as in the case of the mold side surface heating method described above.

  When the mold set is transported to the heating stage by the feed 9, a feed completion signal is output to a control unit (not shown), and the control unit lowers the upper plate 3a so that the upper mold 1a constituting the mold set is Touch the bottom. Thereby, the furnace stand 12 surrounds the outer periphery of the side surface of the mold set, and the infrared heater 4c provided on the furnace stand 12 is positioned at the center height of the mold set. Then, heating control is performed by the thermocouple 10 and the temperature controller so that the temperature of the furnace 12 becomes 370 ° C to 350 ° C.

  The heating temperature and time at this time are calculated using values obtained in advance by simulation. That is, in order to heat the furnace stand 12 to a predetermined temperature, the set temperature and time are predicted. In this way, after heating the mold set for a predetermined time, the temperature control of the infrared heater 4c is finished, the upper plate 3a is raised, and the furnace bed 12 is retracted from the mold set. When the evacuation is completed, the mold set is conveyed to the next press stage by the feed 9.

[Pressing process in mold side heating method]
When the mold set is conveyed to the press stage by the feed 9 after the heating step described above, a feed completion signal is output to the control unit, and the control unit controls the upper plate 3a as in the case of the heating stage. Is brought into contact with the bottom surface of the upper mold 1a constituting the mold set. And the furnace stand 12 is heated by the output of the infrared heater 4c so that it may become 380 degreeC of preset temperature (molding temperature). It is assumed that the furnace 12 reaches a certain temperature by heating at a set temperature for a predetermined time, and the upper and lower molds 1a and 1b, the sleeve 2 and the glass material 8 are heated uniformly. When a predetermined heating time elapses, the push rod 7 descends and presses the upper plate 3a. By pressing the upper plate 3a, pressure is transmitted to the bottom surface of the upper mold 1a, and the glass material 8 is pressed. Such a press is performed for a predetermined time, and the press is terminated after a set time has elapsed. Thereafter, the upper plate 3a is raised to retract the furnace table 12 from the mold set. When the evacuation is completed, the mold set is conveyed to the next cooling stage by the feed 9.

[Cooling process in mold side heating method]
When the mold set is conveyed to the cooling stage by the feed 9 after the pressing step described above, a signal indicating completion of feeding is output to the control unit, and in the same manner as in the heating stage and the press stage, the control unit The upper plate 3a is lowered and brought into contact with the bottom surface of the upper mold 1a constituting the mold set. Thereby, the cylindrical member provided with the cooling port 13 surrounds the outer periphery of the side surface of the mold set. Thereafter, cooling nitrogen is ejected from the cooling port 13, and the cooling nitrogen is sprayed on the outer periphery of the side surface of the mold set constituting the mold set. Thereby, the sleeve 2, the upper and lower molds 1a and 1b, and the glass material 8 are cooled, and the glass material 8 is solidified. During the cooling process, the upper plate 3a is pressurized by the push rod 7. When a predetermined cooling time elapses, the control unit stops the outflow of cooling nitrogen and raises the cylindrical member provided with the upper plate 3a and the cooling port 13.

  As described above, according to the method of molding an optical element according to the present embodiment, when the outer diameter of the molding die (upper die 1a, lower die 1b) is large and the height is low (the standard for eccentricity accuracy is not strict). In the case of an optical element), as shown in FIG. 1, heating from the bottom surface of the mold can be performed to improve heating efficiency and perform molding with high production efficiency. Moreover, since the mold is heated once to a predetermined temperature equal to or lower than the molding temperature, and the molding is performed while sequentially heating at the molding temperature, the temperature of the glass material 8 is less likely to vary, so that the molding quality can be maintained.

  On the other hand, when the mold has a small outer diameter and a high height (in the case of an optical element with a strict standard for decentration accuracy), heating is performed from the side of the mold as shown in FIG. As a result, the heating efficiency can be improved and molding with good production efficiency can be performed. Moreover, since the mold is heated once to a predetermined temperature equal to or lower than the molding temperature, and the molding is performed while sequentially heating at the molding temperature, the temperature of the glass material 8 is less likely to vary, so that the molding quality can be maintained.

  Further, in the case of the conventional configuration in which the push bar 7 and the upper plate 3a are fixed, the upper mold 1a is inclined by the glass material 8 such as a glass gob and cannot be heated efficiently. As described above, by separating the push bar 7 and the upper plate 3a, the upper plate 3a can be brought into close contact with the bottom surface of the upper die 1a even when the upper die 1a is inclined by the glass material 8, so that the heating can be efficiently performed. It can be carried out. In addition to this, even when the upper plate 3a is tilted in units of several microns due to manufacturing errors or the like, the push rod 7 is separated, so that smooth sliding can be performed when molding pressure is applied. it can.

  In addition, the shaping | molding method of the optical element which concerns on this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the optical element material is the glass material 8, but the present invention is not limited to this, and a resin material such as optical plastic can also be used.

It is a schematic sectional drawing which shows the shaping | molding apparatus of the optical element for implementing the die bottom heating system in the shaping | molding method of the optical element which concerns on this embodiment. It is a schematic sectional drawing which shows the shaping | molding apparatus of the optical element for implementing the type | mold side surface heating system in the shaping | molding method of the optical element which concerns on this embodiment. It is a schematic sectional drawing of the type | mold set used for the shaping | molding method of the optical element which concerns on this embodiment. It is a graph which shows the result of having performed the shaping | molding simulation by the mold bottom face heating system in the selection process of the shaping | molding method of the optical element which concerns on this embodiment. It is explanatory drawing which shows the said type | mold bottom surface heating system. It is explanatory drawing which shows the case where the outer diameter <height of the shaping | molding die in the said mold bottom face heating system. It is explanatory drawing which shows the case where the outer diameter> height of the shaping | molding die in the said mold bottom face heating system. It is a graph which shows the result of having performed the shaping | molding simulation by the type | mold side surface heating system in the selection process of the shaping | molding method of the optical element which concerns on this embodiment. It is explanatory drawing which shows the said type | mold side surface heating system. It is explanatory drawing which shows the case where the outer diameter> height of the shaping | molding die in the said type | mold side surface heating system. It is explanatory drawing which shows the case where the outer diameter <height of the shaping | molding die in the said type | mold side surface heating system.

Explanation of symbols

1a Upper mold (molding mold)
1b Lower mold (molding mold)
2 Sleeve 3a Upper plate 3b Lower plate 4a Upper infrared heater 4b Lower infrared heater 4c Infrared heater 5 Reflector 6a Upper block 6b Lower block 7 Push rod 8 Glass material (optical element material)
9 Feed 10 Thermocouple 11 Hook 12 Furnace 13 Cooling port a Mold diameter b Mold center height

Claims (4)

  In a molding method of an optical element in which an optical element material is press-molded by a pair of molding dies, a mold bottom surface heating method in which the optical element material is heated from the bottom surface side of the molding die based on an outer diameter and a height of the molding die Or a selection step of selecting one of the mold side surface heating methods for heating the optical element material from the side surface side of the mold, and a heating step of heating the optical element material by the heating method selected in the selection step, And a pressing step of press-molding the optical element material heated in the heating step with the molding die.   In the selecting step, when the height is smaller than the outer diameter of the mold, the mold bottom surface heating method is selected, and when the height is larger than the outer diameter of the mold, the mold side surface heating method is selected. The method for molding an optical element according to claim 1, wherein:   When heating the optical element material by the mold bottom surface heating method, the heating process heats the mold to a predetermined temperature lower than the mold temperature during the pressing process, and the heating to the predetermined temperature. The method for molding an optical element according to claim 1, further comprising a second heating step of heating the molded die to a molding die temperature during the pressing step. In the first heating step, the mold is heated at a predetermined speed to a predetermined temperature that is 10 to 40 ° C. lower than the mold temperature during the pressing step. In the second heating step, the predetermined temperature is increased from the predetermined temperature during the pressing step. The method for molding an optical element according to claim 3, wherein the mold is heated at a speed slower than that of the first heating step up to the mold temperature of 5.