JP2019131444A - Method of molding optical element - Google Patents

Abstract

To provide a method of molding an optical element capable of suppressing cracking and burning of the optical element and securing face precision of an outer peripheral part and a molding face outer peripheral part of the optical element.SOLUTION: A method of molding an optical element comprises pressing a molding blank to form the optical element to which optical faces by an upper mold and a lower mold and a side face by a side mold have been transferred, and includes: a heating process of heating the molds so that the molding blank reaches a first temperature corresponding to first viscosity at which the molding blank does not enter a gap between the upper mold and side mold and a gap between the lower mold and side mold when preset first pressing force is applied; a first pressing process of applying the first pressing force to the molding blank until a reduction speed of the inter-mold distance between the upper mold and lower mold becomes a predetermined speed or lower or until the reduction in the inter-mold distance stops; and a second pressing process of heating the surface of the molding blank so that the temperature of the surface reaches a second temperature at which second viscosity lower than the first viscosity is obtained, and applying the first pressing force to the molding blank.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for molding an optical element.

  Conventionally, by pressing a molding material placed in a cavity in a molding die composed of an upper die, a lower die and a side die, the optical surface by the upper die and the lower die and the side surface by the side die are transferred. A method for molding an optical element is known.

  For example, in Patent Document 1, when the molding material is pressed and deformed, by monitoring the approach speed of the upper mold with respect to the lower mold, it is detected that the molding material is filled in the cavity based on a decrease in the approach speed, A method of forming an optical element is disclosed in which the pressure deformation is terminated after detecting the filling and then cooled and cured.

JP 2009-249273 A

  Here, in the molding method disclosed in Patent Literature 1, after the molding material is filled into the cavity, the molding die is cooled to cure the molding material. Therefore, when the molding material is pressed and deformed, the molding material M softened in the gap between the upper die 11 and the side die 13 and the gap between the lower die 12 and the side die 13, for example, as shown in part A of FIG. 4. There was a case of getting in. As a result, the molding material M that has entered the gap becomes a burr after cooling and hardening, and the burr is caught at the time of taking out and there is a possibility that the optical element is cracked.

  Further, in the molding method disclosed in Patent Document 1, since the pressure on the outer peripheral side of the molding material M is pressed in a state lower than the temperature of the center portion, the contact position between the molding material M and the inner surface of the side mold 13 is local. Therefore, there was a possibility that the molding material M might be seized on the inner surface of the side mold 13. Further, in the molding method disclosed in Patent Document 1, although the molding material M is filled in the cavity, the contact time of the molding material M with the inner surface of the side mold 13 and the outer peripheral portion of the molding surface in the vicinity thereof is the upper mold 11. Because the contact time of the molding material M with respect to the center portion of the molding surface 11a and the center portion of the molding surface 12a of the lower mold 12 is shorter, the surface accuracy of the outer periphery of the optical element after molding and the outer periphery of the molding surface is ensured. There was a risk of not being able to.

  The present invention has been made in view of the above, and a method for molding an optical element capable of suppressing cracking and seizure of the optical element and ensuring the surface accuracy of the outer peripheral portion of the optical element and the outer peripheral portion of the molding surface. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, an optical element molding method according to the present invention presses a molding material arranged in a molding die composed of an upper die, a lower die, and a side die. By the above, a molding method of an optical element for molding an optical element in which an optical surface by the upper mold and the lower mold and a side surface by the side mold are transferred, and a preset first pressing force is applied. In this case, the temperature of the molding material is set to the first temperature at which the molding material does not enter the gap between the upper mold and the side mold and the gap between the lower mold and the side mold. A heating step of heating the molding die, and until the reduction speed of the distance between the upper mold and the lower mold becomes a predetermined speed or less, or until the reduction of the distance between the molds stops, A first pressing step for applying a first pressing force, and the first A second pressing step of heating the mold so that the surface temperature of the molding material becomes a second temperature at which the second viscosity is lower than the viscosity, and applying the first pressing force to the molding material; , Including.

  Moreover, the molding method of the optical element according to the present invention is the above invention, wherein in the second pressing step, the surface of the molding material has a second temperature lower than the first viscosity. The mold is heated so as to reach a temperature, and a second pressing force smaller than the first pressing force is applied to the molding material.

  The optical element molding method according to the present invention is the above-described invention, wherein the upper mold and the lower mold are disposed between the heating step and the first pressing step or during the first pressing step. The activity of the material surface is lowered by lowering the temperature of one or more of the side molds, and the viscosity of the surface of the molding material is made higher than the first viscosity.

  According to the present invention, during the molding of the molding material, the activity of the material surface is lowered to suppress the seizure between the molding die and the gap between the upper die and the side die and the gap between the lower die and the side die. Since the molding material can be prevented from entering, the ease of cracking of the optical element due to the occurrence of burrs due to the molding material entering can be suppressed. Moreover, according to this invention, the surface precision of the outer peripheral part of the optical element after shaping | molding and a molding surface outer peripheral part is securable.

FIG. 1 is a cross-sectional view schematically showing a configuration of a molding die used in the method for molding an optical element according to the embodiment of the present invention. FIG. 2 is a flowchart showing the procedure of the optical element molding method according to the embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a molding material after pressing in the optical element molding method according to the embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing a molding material after pressing in the conventional optical element molding method.

  Embodiments of a method for molding an optical element according to the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  The optical element molding method according to the present embodiment presses a molding material arranged in a molding die composed of an upper die, a lower die, and a side die, thereby providing an optical surface by the upper die and the lower die, This is a method of molding an optical element having a side surface transferred by a side mold. In the optical element molding method according to the present embodiment, as shown in FIG. 1, a molding die 1, a position gauge 2, a timer 3, and a control unit 4 are used.

  The molding die 1 includes an upper die 11 having a molding surface 11a formed at one end, a lower die 12 having a molding surface 12a formed at one end, and a side die (sleeve) 13. A cavity Ca that is a space surrounded by the upper mold 11, the lower mold 12, and the side mold 13 is formed inside the mold 1, and the molding material M is disposed in the cavity Ca.

  The upper mold 11 and the lower mold 12 are arranged such that their molding surfaces 11a and 12a face each other with the molding material M in between. The side mold 13 is for sliding and guiding the upper mold 11 and the lower mold 12. The side mold 13 is formed in a cylindrical shape as a whole, and holds the upper mold 11 and the lower mold 12 so as to be freely inserted and removed. Note that gaps necessary for sliding during mold operation are formed between the upper mold 11 and the side mold 13 and between the lower mold 12 and the side mold 13.

  Moreover, each type | mold which comprises the shaping | molding die 1 is comprised so that heating is possible by the heater unit which is not shown in figure, and it is possible to indirectly heat the shaping | molding raw material M arrange | positioned inside the shaping | molding die 1. FIG. As will be described later, the molding material M heated and softened by the molding die 1 is deformed by the approaching action of the upper die 11 and the lower die 12, and is shaped into the shape of the optical element.

  The position gauge 2, the timer 3, and the control unit 4 are for monitoring the speed at which the distance between the upper mold 11 and the lower mold 12 is reduced when the molding material M is pressed. The position gauge 2 measures the relative distance of the upper mold 11 relative to the lower mold 12 when the upper mold 11 is approaching the lower mold 12, and outputs the information to the control unit 4. The timer 3 measures the time when the upper mold 11 is approaching the lower mold 12 and outputs the information to the control unit 4. Then, the control unit 4 calculates the speed at which the distance between the molds is reduced based on these pieces of information, and whether or not the reduction speed of the distance between the molds of the upper mold 11 and the lower mold 12 is equal to or lower than a predetermined speed, or Detects whether the reduction of the distance between the molds has stopped.

  Hereinafter, a method for molding an optical element according to the present embodiment will be described with reference to FIGS. In the optical element molding method, a heating process, a first pressing process, a second pressing process, a cooling process, and a mold releasing process are performed. In the optical element molding method, a surface temperature (viscosity) adjusting step is performed between the heating step and the first pressing step, or during the first pressing step, as necessary.

(Heating process)
In the heating process, when a preset first pressing force is applied, the temperature of the molding material M is set to a first temperature at which the molding material M has a first viscosity that does not enter the gap between the molds 1. The mold 1 is heated so that (see step S1 in FIG. 2). The above-mentioned “gap between the molds of the mold 1” specifically means a gap between the upper mold 11 and the side mold 13 and a gap between the lower mold 12 and the side mold 13.

  In the heating step, specifically, the molding die 1 is heated by a heater unit (not shown), thereby heating the molding material M disposed in the cavity Ca of the molding die 1 to the first temperature, Soften to one viscosity. This first temperature is in the range from the TG point (glass transition point) to the SP point (softening point) of the molding material M, and with respect to the first pressing force in the first pressing step described later, the mold 1 Is a temperature at which the softened molding material M cannot enter the gap between the molds (first viscosity). In the heating process, by changing the set temperature of the heater unit provided in the upper mold 11 and the lower mold 12, the vertical difference in formability due to the shape factor and the shape of the mold can be adjusted.

  Here, the first temperature (first viscosity) is determined by experimentally calculating in advance in consideration of the heating temperature of the molding material M and the tendency of viscosity change with respect to the first pressing force. The combination of the first temperature (first viscosity) and the first pressing force used in the present embodiment is that the molding material M enters the gap between the molds of the molding die 1 in the first pressing step described later. It is a combination that does not. For example, at a certain temperature (viscosity), when the intrusion of the molding material M occurs at a certain pressing force, the intrusion of the molding material M can be suppressed by lowering the pressing force. Conversely, when the molding material M enters at a certain pressure (viscosity) at a certain pressing force, the penetration of the molding material M can be suppressed by lowering the temperature (increasing the viscosity). In the present embodiment, in consideration of these tendencies, the combination of the first temperature (first viscosity) and the first pressing force is determined according to the molding purpose.

(Surface viscosity adjustment process)
In the surface viscosity adjusting step, the temperature of the molding die 1, that is, the temperature of one or more of the upper die 11, the lower die 12, and the side die 13 is lowered to reduce the viscosity of the surface of the molding material M to the first viscosity. (See step S2 in FIG. 2). The “surface” of the molding material M includes not only the surface of the molding material M but also a surface layer having a predetermined depth from the surface.

  In the surface viscosity adjusting step, specifically, after the molding material M is softened by heating in the heating step, the temperature of the molding material M in contact with the molding die 1 is slightly lowered by slightly lowering the temperature of the molding die 1. Increase slightly. By performing this surface viscosity adjustment step, the possibility of the molding material M entering the gaps between the molds 1 can be further reduced. Note that the value of the temperature decrease of the mold 1 in the surface viscosity adjusting step is determined by experimentally obtaining in advance. Further, the surface viscosity adjusting step may be performed as an independent step after the heating step, or may be performed while the molding material M is being pressed in the first pressing step which is a subsequent step.

(First pressing step)
In the first pressing step, the molding material is used until the reduction speed of the distance between the upper mold 11 and the lower mold 12 is equal to or lower than a predetermined speed or until the reduction of the distance between the upper mold 11 and the lower mold 12 is stopped. A first pressing force is applied to M (see step S3 in FIG. 2).

  Specifically, in the first pressing step, the upper die 11 is relatively moved closer to the lower die 12 and a first pressing force is applied to the molding material M in the molding die 1. At that time, the position gauge 2, the timer 3 and the control unit 4 monitor the reduction speed of the distance between the upper mold 11 and the lower mold 12, and the reduction speed of the distance between the molds becomes a predetermined speed or less. The molding material M is pressed until the approaching action of the mold 12 is rapidly decelerated or the reduction of the distance between the molds is stopped and the approaching action of the upper mold 11 and the lower mold 12 is stopped.

  Here, the rapid deceleration and stop of the approaching action of the upper die 11 and the lower die 12 is that the molding material M is filled in the cavity Ca of the molding die 1, that is, the molding material M is the molding surface 11 a of the upper die 11. This means that the molding surface 12a of the lower mold 12 and the inner surface of the side mold 13 are in contact with each other. In this state, the molding material M cannot be pushed further. Further, since the viscosity of the molding material M is adjusted in the heating step and the surface viscosity adjusting step, the molding material M does not enter the gap between the molds 1 as shown in FIG.

(Second pressing step)
In the second pressing step, the molding die 1 is heated so that the surface temperature of the molding material M becomes the second temperature at which the second viscosity is lower than the first viscosity. Pressure is applied (see step S4 in FIG. 2).

  Specifically, in the second pressing step, the molding is in contact with the molding surface 11a of the upper die 11, the molding surface 12a of the lower die 12, and the inner surface of the side die 13 by slightly raising the temperature of the molding die 1. The surface of the material M is reheated, and the viscosity of the surface of the molding material M is slightly lowered from the first viscosity. And by pressing the molding material M in this state, the adhesion between the molding surface 11a of the upper mold 11, the molding surface 12a of the lower mold 12 and the inner surface of the side mold 13, and the molding material M is improved. The surface accuracy of the upper and lower optical surfaces and side surfaces of the optical element can be ensured. In the second pressing step, only the surface of the molding material M is heated, and no significant deformation of the entire molding material M occurs, so that the molding material M may enter a gap between the molds 1. Absent.

  Here, in the second pressing step, it is desirable to press the molding material M with a second pressing force smaller than the first pressing force after the heating of the molding material M. Thereby, when the molding material M is pressed, the possibility that the molding material M enters the gap between the molds of the molding die 1 can be further reduced. Further, by making the pressure lower, surface stress can be further improved without excessive stress. Note that the value of the temperature increase width and the value of the pressing force decrease width of the mold 1 in the second pressing step are experimentally determined and determined in advance. In addition, the second pressing step is mainly performed to ensure the surface accuracy of the optical element after molding, but by performing this step, it is possible to adjust the sharpness of the ridge line of the outer peripheral portion of the optical element. .

  Further, in the optical element molding method according to the present embodiment, it is determined in the first pressing step that the approaching action of the upper mold 11 and the lower mold 12 is suddenly decelerated or the reduction in the distance between the molds is stopped. After that, it is desirable to immediately move to the second pressing step, raise the temperature of the mold 1, and lower the pressing force from the first pressing force as necessary. Moreover, it is desirable to move to the cooling process promptly even after the completion of the second pressing process.

(Cooling process)
In the cooling process, the pressing force and the temperature of the molding die 1 are lowered than in the second pressing process, and the molding material M whose shape and surface accuracy are determined is cooled and cured (see step S5 in FIG. 2). In the cooling step, the molding material M is cooled stepwise or gradually in order to prevent a sudden change in optical characteristics due to heat shock.

(Release process)
In the mold release step, the molded optical element is taken out from the mold 1 (see step S6 in FIG. 2).

  According to the optical element molding method according to the present embodiment as described above, during the molding of the molding material M, the activity of the material surface is lowered to suppress the seizure with the molding die 1 and the molding die. Since it is possible to suppress the molding material M from entering the gap between the molds 1, it is possible to suppress the fragility of the optical element caused by burrs caused by the molding material M entering. Moreover, according to the molding method of the optical element according to the present embodiment, it is possible to ensure the surface accuracy of the outer peripheral part of the optical element after molding and the outer peripheral part of the molding surface.

  The optical element molding method according to the present invention has been specifically described above by the embodiments for carrying out the invention. However, the gist of the present invention is not limited to these descriptions, and the description of the scope of claims Should be interpreted widely. Needless to say, various changes and modifications based on these descriptions are also included in the spirit of the present invention.

  For example, the optical element molding method according to the present embodiment is basically applied to a condition-variable molding method using a single axis, but can also be applied to a circulation molding method.

DESCRIPTION OF SYMBOLS 1 Molding die 11 Upper mold | type 11a, 12a Molding surface 12 Lower mold | type 13 Side mold | type 2 Position gauge 3 Timer 4 Control part Ca cavity M Molding material

Claims (3)

Optical in which an optical surface formed by the upper mold and the lower mold and a side surface formed by the side mold are transferred by pressing a molding material disposed in a molding mold including an upper mold, a lower mold, and a side mold. An optical element molding method for molding an element,
When a preset first pressing force is applied, the first viscosity becomes a first viscosity at which the molding material does not enter the gap between the upper mold and the side mold and the gap between the lower mold and the side mold. A heating step of heating the mold so that the temperature of the molding material becomes one temperature;
The first press that applies the first pressing force to the molding material until the reduction speed of the distance between the upper mold and the lower mold becomes a predetermined speed or less or until the reduction of the distance between the molds stops. Process,
The mold is heated so that the surface temperature of the molding material becomes a second temperature at which the second viscosity is lower than the first viscosity, and the second pressing force is applied to the molding material. Pressing process,
A method for forming an optical element, comprising:   In the second pressing step, the mold is heated so that the temperature of the surface of the molding material becomes a second temperature at which the second viscosity is lower than the first viscosity, and the molding material is heated to the second temperature. The method for molding an optical element according to claim 1, wherein a second pressing force smaller than the one pressing force is applied.   By reducing the temperature of one or more of the upper mold, the lower mold and the side mold during the heating process and the first pressing process or during the first pressing process. The method for molding an optical element according to claim 1 or 2, wherein the activity of the material surface is lowered and the viscosity of the surface of the molding material is made higher than the first viscosity.

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