JP2008183762A - Method of molding optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of molding an optical element which can eliminate the influence of bubbles even in cases involving thermosetting resins and/or photo-curable resins and an optical element molded thereby. <P>SOLUTION: Since a convex cavity 11 is located above, bubbles BL move from the cavity 11 to the periphery and escape to a circular concave part 16. Without solidification of a resin with the bubbles BL left in contact with the cavity 11, the method thus enables control of poor molding of optical elements. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for molding an optical element, and particularly relates to a molding method for molding an optical element using a thermosetting resin or a photocurable resin, and an optical element molded thereby.

In recent years, it has been common practice to mount an imaging device on a mobile phone or the like. A general imaging device is configured to join an optical element such as a lens on a substrate and form a subject image on a light receiving surface of a solid-state imaging element via the optical element. By the way, in order to simplify the manufacturing process, there is a demand for passing through a high-temperature solder reflow bath with an optical element mounted on a substrate. However, acrylics and polycarbonates currently used as materials for optical elements have low heat resistance, and there is a problem that they easily melt and deform when passed through a high-temperature solder reflow bath. On the other hand, a thermosetting resin has a characteristic that its viscosity decreases and it flows easily by heating, but once heated and solidified, its shape is maintained even at a higher temperature. The photo-curable resin is also in a liquid state when not exposed to light, but has a characteristic of maintaining its shape even at a high temperature once solidified by exposure to light. Therefore, if a thermosetting resin or a photocurable resin is used, an optical element that can be passed through a solder reflow bath can be molded.
JP 2003-236843 A

  Here, one of the problems in molding using a thermosetting resin or a photocurable resin is that a reactive gas is easily generated during the curing reaction. There is a risk that such reaction gas may become bubbles and stay in the resin material. Especially when the resin is in a liquid with a relatively low viscosity, the bubbles will float on the optical surface and remain solidified as they are. There is a problem that a defect occurs, and normal transmission and reflection of light incident on the molded optical element is hindered.

  On the other hand, in order to prevent air bubbles from being involved in the resin filled during injection molding, for example, as shown in Patent Document 1, the inside of the molding cavity is evacuated or the shape of the resin flow path is improved. Etc. have already been done. However, in thermosetting resins or photo-curing resins, bubbles are generated from the inside of the resin, and it is essentially a countermeasure by evacuating the molding cavity or improving the shape of the resin flow path. There is a problem that you can not.

  The present invention has been made in view of such problems of the prior art, and a method for molding an optical element capable of eliminating the influence of bubbles even when a thermosetting resin or a photocurable resin is used, and the same It aims at providing the optical element shape | molded by this.

The method for molding an optical element according to claim 1 comprises:
By combining an upper mold having a transfer molding surface for transfer molding of the optical surface of the optical element and a lower mold disposed below the upper mold in the direction of gravity, the upper mold and the lower mold are Forming a molding cavity connected to the transfer molding surface and a recess disposed above the transfer molding surface in the direction of gravity;
A liquid thermosetting resin or a photocurable resin is transferred to the molding cavity, and
In the molding cavity, bubbles generated from the thermosetting resin or the photocurable resin escape to the concave portion.

  According to the present invention, since the bubbles generated from the thermosetting resin or the photocurable resin escape into the recess in the molding cavity, the bubbles remain on the transfer molding surface. This can suppress the molding defect of the optical element. Here, the “optical surface” includes both a light transmission surface and a light reflection surface.

  According to a second aspect of the present invention, there is provided the optical element molding method according to the first aspect of the invention, wherein the recess surrounds the transfer molding surface. Air bubbles can also escape in the recess.

  The method for molding an optical element according to claim 3 includes a step of interposing a plate-like insert member when the upper mold and the lower mold are combined in the invention according to claim 1 or 2. Features. An air vent or the like can be formed on the insert member.

  An optical element according to a fourth aspect is formed by the method for molding an optical element according to any one of the first to third aspects, and has at least a concave optical surface.

  Here, examples of the “thermosetting resin” include silicon resin, allyl ester, acrylic resin, epoxy resin, polyimide, and urethane resin. Examples of the “thermosetting resin or photocurable resin” include silicon resin, allyl ester, acrylic resin, epoxy resin, polyimide, and urethane resin.

  Furthermore, as the “optical element”, for example, a lens, a prism, a diffraction grating optical element (a diffraction lens, a diffraction prism, a diffraction plate), an optical filter (a spatial low-pass filter, a wavelength band-pass filter, a wavelength low-pass filter, a wavelength high-pass filter, etc.) , A polarizing filter (analyzer, optical rotator, polarization separation prism, etc.) and a phase filter (phase plate, hologram, etc.), but are not limited thereto.

  ADVANTAGE OF THE INVENTION According to this invention, even when a thermosetting resin or a photocurable resin is used, the optical element shaping | molding method which can exclude the influence of a bubble, and the optical element shape | molded by it can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a mold and an insert member used in the optical element molding method according to the present embodiment. FIG. 2 is a cross-sectional view of the mold of the optical element and the insert member in the molded state. FIG. 3 is an enlarged view showing an arrow III part of the configuration of FIG. In the present embodiment, a plate-like insert member 30 is arranged between the block-like upper mold 10 and the lower mold 20, but the insert member 30 is not necessarily required.

  On the lower surface (partition surface) of the upper mold 10, upper cavities 11 having a circular convex shape at the center are arranged in two rows, and two are spaced apart diagonally (only one is shown in FIG. 1). The pin hole 12 is formed. On the other hand, circular concave concave cavities 21 arranged in two rows corresponding to the upper cavities 11 are formed on the upper surface (divided surface) of the lower mold 20, and alignment pins corresponding to the pin holes 12. 22 are planted. The convex optical surface of the optical element molded by the molding method of the present embodiment is molded by the lower cavity 21 that is the transfer optical surface, and the concave optical surface of the optical element is the upper cavity 11 that is the transfer optical surface. Is formed by. That is, a molding cavity for molding an optical element is formed by combining the upper mold 10 and the lower mold 20.

  In FIG. 3, an annular recess 16 is formed so as to connect to the entire periphery of the upper cavity 11. The bottom surface 16a of the annular recess 16 is located above the upper cavity 11 in the direction of gravity (upward in FIG. 3), and the inner peripheral surface 16b is provided with a draft angle that widens toward the lower mold 20. Yes.

  Further, in FIG. 1, large grooves 13 extending from the ends of the upper mold 10 are formed between the rows of the upper cavities 11 on the lower surface of the upper mold 10, and are further communicated from the large grooves 13 toward the upper cavities 11. A not-formed taper groove 14 is formed. The large groove 13 and the tapered groove 14 constitute a runner. Further, a clearance groove 15 is formed on the lower surface of the upper mold 10 on the opposite side of the large groove 13 across the upper cavities 11 of each row, and at the end opposite to the end where the large groove 13 opens. It is open.

  The insert member 30 is a copper plate, and circular openings 31 are formed in two rows corresponding to the cavities 11 and 21, and notches 37 and 38 are formed on both sides of each opening 31. Matching holes 32 are formed corresponding to the pins 22. The thermal conductivity of the insert member 30 is preferably the same as or higher than the thermal conductivity of the molds 10 and 20. The insert member 30 may be made of other metal such as phosphor copper or aluminum, glass, or resin material such as Teflon or PC.

  As shown in FIG. 2, when the insert member 30 is overlapped between the upper mold 10 and the lower mold 20, the notch 37 of the insert member 30 communicates with the tapered groove 14, and the notch 38 communicates with the escape groove 15. It becomes like this. By adjusting the overlapping area of the notch 37 and the tapered groove 14, it can function as a gate portion.

  Furthermore, in FIG. 2, the lower mold | type 20 forms the two protrusion parts 26 on both sides of the lower cavity 21 in the division | segmentation surface. In the free state, the upper surface of the insert member 30 is located higher than the upper end of the protruding portion 26.

  FIG. 4 is a schematic view showing a process of molding an optical element using the mold and insert member of the present embodiment, but shows a single cavity for easy understanding. First, as shown to Fig.4 (a), the insert member 30 is mounted on the lower mold | type 20 installed on the surface plate, and the upper mold | type 10 is set above it. At this time, since the alignment pin 22 of the lower mold 20 shown in FIG. 1 is fitted into the alignment hole 32 of the insert member 30 and the pin hole 12 of the upper mold 10, the molds 10, 20 and the insert member 30 are It will be accurately aligned in the direction.

  Here, referring to FIG. 4 (b), the upper mold 10 is pressurized by the hydraulic cylinder 40. The hydraulic cylinder 40 is provided with a pressure sensor 41 so that the press pressure can be detected. The press pressure detected by the pressure sensor 41 is input to the control device 42. The control device 42 can control the pressure of the hydraulic cylinder 40 in accordance with the detected press pressure.

  In FIG. 4B, the upper mold 10 pressurized by the hydraulic cylinder 40 applies a compressive force to the insert member 30. As a result, the insert member 30 comes into close contact between the upper mold 10 and the lower mold 20 with a predetermined surface pressure. Furthermore, since the distance between the upper mold 10 and the lower mold 20 changes by adjusting the press pressure within the elastic deformation region of the insert member 30, the axial thickness of the optical element after molding is thereby changed. Can be adjusted.

  In FIG. 4C, the molds 10 and 20 and the insert member 30 are heated by the heater 50 while maintaining the pressing pressure, and the heated thermosetting resin (or photocurable resin) having a low viscosity is further obtained. It inject | pours into the inside through the large groove | channel 13 (FIG. 1) of the upper mold | type 10 from the outside. Since the insert member 30 is in close contact with the dividing surface of the upper die 10 and the lower die 20, the resin flow path formed by the large groove 13 and the tapered groove 14 (including the gate portion) is shielded by the insert member 30 itself. Since it is sealed, there is no leakage of the heated thermosetting resin (or photocurable resin) having a low viscosity. The resin injected from the outside passes through the large groove 13, the tapered groove 14, and the notch 37 and reaches the cavities 11 and 21. At this time, the air pushed out by the resin flowing into the cavities 11 and 12 escapes from the notch 38 to the outside through the escape portion 15. Thereby, the highly accurate shape of the optical element to be molded can be ensured.

  In the case of a thermosetting resin, it is further heated. In the case of a photocurable resin, the upper mold 10 is moved upward after the resin is solidified by irradiating ultraviolet rays through a mold made of a transparent material. When moved, the optical element OE molded so that the flange portion is in close contact with the insert member 30 is exposed. Therefore, as shown in FIG. 4D, all the optical elements OE attached to the insert member 30 can be removed at once by removing the insert member 30 from the lower mold 20. Thereafter, another insert member 30 can be arranged between the upper mold 10 and the lower mold 20 to prepare for molding again (see FIG. 4A). In parallel with this, the optical element OE can be separated from the removed insert member 30. Thereby, the molding cycle time can be shortened. The intermediate member 30 from which the optical element OE has been removed can be reused.

  FIG. 5 is a diagram showing the effect of the present embodiment. When the thermosetting resin is heated or the photocurable resin is irradiated with ultraviolet rays to solidify, bubbles are generated from the inside of the resin. At this time, since the viscosity of the resin is low, the generated bubbles move upward in the direction of gravity. Here, as shown in FIG. 5A, when the concave cavity 21 of the lower mold 20 is positioned upward, the bubble BL is trapped at the center of the cavity 21. When the resin is solidified in this state, hole defects due to bubbles are generated on the optical surface of the optical element, which may deteriorate optical characteristics.

  On the other hand, according to the present embodiment, as shown in FIG. 5B, since the convex cavity 11 is located above, the bubbles BL wrap around the outer periphery along the surface of the cavity 11 to form an annular recess. Escape to 16. Therefore, the resin does not solidify while the bubbles BL are in contact with the cavity 11, and the molding failure of the optical element can be suppressed. The resin solidified in the annular recess 16 becomes a part of the flange part and is often used as a reference surface for attaching the optical element to other parts. There is no problem in installation.

  Furthermore, when the recess 16 is provided around the cavity 11, there is an advantage that interference with the tool is suppressed when the upper die 10 is cut.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate.

It is a perspective view of the metal mold | die and insert member of the optical element by this Embodiment. It is sectional drawing of the metal mold | die and insert member of an optical element in a shaping | molding state. It is a figure which expands and shows the arrow III part of the structure of FIG. It is the schematic which shows the process of shape | molding an optical element using the metal mold | die and insert member of this Embodiment. Fig.5 (a) is sectional drawing of the metal mold | die concerning a comparative example, FIG.5 (b) is sectional drawing of the metal mold | die concerning this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Upper mold | type 11 Upper cavity 12 Pin hole 20 Lower mold | type 21 Lower cavity 22 Alignment pin 13 Large groove 14 Tapered groove 15 Escape groove 26 Projection part 30 Insert member 40 Hydraulic cylinder 41 Pressure sensor 42 Control apparatus 50 Heater OE Optical element

Claims (4)

By combining an upper mold having a transfer molding surface for transfer molding of the optical surface of the optical element and a lower mold disposed below the upper mold in the direction of gravity, the upper mold and the lower mold are Forming a molding cavity connected to the transfer molding surface and a recess disposed above the transfer molding surface in the direction of gravity;
A liquid thermosetting resin or a photocurable resin is transferred to the molding cavity, and
A method for molding an optical element, characterized in that air bubbles generated from the thermosetting resin or the photocurable resin escape into the recess in the molding cavity.   The method for molding an optical element according to claim 1, wherein the concave portion surrounds the transfer molding surface.   The method for molding an optical element according to claim 1, further comprising a step of interposing a plate-like insert member when the upper mold and the lower mold are combined. An optical element formed by the method for forming an optical element according to claim 1, and having at least a concave optical surface.