JPWO2010035619A1 - Optical pickup objective lens manufacturing method, optical pickup objective lens molding die, and optical pickup objective lens - Google Patents

Abstract

Provided is an objective lens for an optical pickup having a low coma aberration, which can prevent damage to a transfer surface due to pin galling, and has a high accuracy and heat resistance even when it is small, and a molding die. Therefore, the protrusion 68 protrudes from the molding surface S3 toward the movable mold 41 at a position where the fixed mold 42 is between the optical surface molding surface 52a and the molding surface S3 and faces the tip surface 54a of the protruding pin 54. Even if the molds 41 and 42 are closed and clamped while projecting on the inner surface of the movable mold 41, the distal end surface 54a of the ejector pin 54 is formed. Is pushed back by the convex portion 68, and it is possible to prevent the occurrence of pin galling that the protruding pin 54 hits the molding surface S3 and damages the molding surface S3.

Description

  The present invention relates to an optical pickup objective lens manufacturing method and a molding die, and more particularly to an optical pickup objective lens manufacturing method and a molding die that perform molding using a cavity formed by a pair of molds. The present invention also relates to an optical pickup objective lens obtained by the above manufacturing method and molding die.

  As a first manufacturing method of the optical pickup objective lens, after the resin is injected into the cavity formed by the first mold and the second mold and molded, the first mold is separated, By opening the mold and operating the core mold, which is a protruding mechanism provided in the first mold, and protruding the optical function part of the molded product remaining in the first mold to the second mold side There are those that release a molded product from a first mold (see, for example, Patent Document 1).

  Further, as a second manufacturing method, after separating the first mold from the second mold and performing mold opening, a plurality of pins which are a plurality of protruding portions provided on the first mold are projected. The mold is released from the first mold by pressing the flange formed on the outer periphery of the optical functional surface of the molded product remaining in the first mold toward the second mold. (See, for example, Patent Documents 2 and 3).

Japanese Patent Laid-Open No. 2002-200654 JP 2007-196665 A International Publication No. 2008/053692

  However, in the first manufacturing method, since the core mold is advanced and retracted to project the molded product, the core mold is displaced with respect to the outer peripheral mold side at every molding shot, and the first mold and the first mold are Since the relative shift amount and tilt amount between the optical surfaces existing in each of the two molds change for each shot, there is a problem that the shape accuracy is likely to fluctuate and the coma aberration becomes unstable. For an objective lens for optical pickup, for example, in the case of a high NA lens having an NA of 0.75 or more, coma aberration generated due to a relative shift or a relative tilt between optical surfaces becomes large. In particular, in the case of a BD (Blu-Ray Disc) objective lens with NA of 0.75 or more, it is necessary to suppress the relative shift within about ± 1.0 μm and the relative tilt within about ± 0.02 °. Such protrusions that may cause the outer peripheral mold side to be displaced are generally undesirable.

  Further, in the second manufacturing method, the return of the protruding pin that advances and retreats from the inner surface of the second mold is temporarily deteriorated due to the influence of resin debris, scratches on the sliding portion, etc., after the molded product is released from the mold. In some cases, the projecting pin protrudes from the second mold and does not return from the state during molding. In this case, when the mold is clamped, the pin tip collides with the first mold part, so-called pin galling occurs, and the transfer surface corresponding to the reference mounting surface when the objective lens is assembled is damaged by the pin tip. There is a possibility. Regarding the objective lens for optical pickup, in particular, in the case of a high NA lens with NA of 0.75 or more, it is necessary to prevent the occurrence of a tilt that causes coma when fixing the objective lens. It is necessary to prevent the occurrence of pin galling that could damage the mounting surface directly affecting the surface.

  In the second manufacturing method, it is also conceivable to avoid interference between the tip of the protrusion pin and the mounting surface of the objective lens by arranging the position of the protrusion pin on the outer peripheral side of the mounting surface of the objective lens. . However, the diameter of the objective lens including the flange portion is increased more than necessary as the position of the protruding pin is arranged on the outer peripheral side, which leads to an increase in the size of the objective lens.

  In addition, the objective lens molded by the manufacturing method as described above, particularly in the case of a high NA lens with NA of 0.75 or more, has a large thickness for a small optical surface diameter of the lens, and at least one of the optical surfaces is Since the curvature becomes very large, it is desirable to make the flange portion thick in the optical axis direction. In other words, when the flange is thickened, when resin flows from the gate into the cavity, the flow resistance is reduced in the space corresponding to the flange, and the resin pressure during molding is reduced. A highly accurate objective lens in which the shape of the transfer surface is transferred to can be obtained. In addition, when the flange is thickened, the internal pressure remaining in the molded product can be reduced due to the fact that the resin pressure during molding can be reduced as described above, and an objective lens with high heat resistance is provided. can do. Further, when the flange portion is thickened, the degree of freedom in design is increased such that the thickness of the resin introduction gate can be increased.

  Therefore, the present invention provides an objective lens for an optical pickup having a small coma aberration, which can prevent damage to a transfer surface, particularly a transfer surface that transfers a mounting surface, due to pin galling, and is small and highly accurate. It aims at providing a manufacturing method and a shaping die.

  It is another object of the present invention to provide an objective lens for an optical pickup which is a small and highly accurate objective lens which is an objective lens with little coma aberration and does not damage the mounting surface due to pin galling.

  In order to solve the above problems, a method for manufacturing an optical pickup objective lens according to the present invention includes (a) a first step of molding a lens with the first mold and the second mold closed; b) A second step of separating the lens from the second mold by separating the first mold and the second mold, and (c) a first step using an ejection pin provided on the first mold side. A third step of releasing the lens from one mold, and (d) a first mold formed on the optical information recording medium side of the lens. (E) the second mold has a second transfer surface for transferring the second optical surface formed on the light source side of the lens, and an outer periphery than the second optical surface. A third transfer surface for transferring the mounting surface formed on the side, and a tip surface of the protrusion pin between the second transfer surface and the third transfer surface And having a convex portion than the third transfer surface provided at a position opposed to at least a portion projecting in a first mold side.

  According to the above manufacturing method, the second mold has the convex portion at a position between the second transfer surface and the third transfer surface and facing the tip surface of the protruding pin, and the convex portion is the third transfer surface. Projecting toward the first mold side, the return of the projecting pin temporarily becomes worse, and the projecting pin protrudes from the inner surface of the first mold and remains in the projecting state and does not return. Even when the mold is closed, the tip surface of the protruding pin hits the convex portion. Therefore, since the sticking pin hits the third transfer surface and can prevent the occurrence of pin galling that damages the third transfer surface, the objective lens for optical pickup after molding and releasing is a precise lens formed by the smooth third transfer surface. It has a mounting surface, and the assembly accuracy of the optical pickup objective lens can be secured. In particular, when mass-produced by repeated molding, it is possible to prevent the third transfer surface, which transfers the mounting surface, from being damaged by pinning and requiring the mold to be replaced for a long time. A pickup objective lens can be obtained.

  It should be noted that even if the convex portion hit by the protruding pin is slightly damaged, the mounting accuracy of the objective lens to the optical pickup is not hindered or the optical performance is not adversely affected. Moreover, since it is a part with little influence also on shaping | molding of an objective lens, it is also possible to eliminate a damage | wound by grind | polishing a metal mold | die.

  Moreover, since the convex part provided between the 2nd transfer surface and the 3rd transfer surface opposes the front end surface of a protrusion pin, an protrusion pin can be arrange | positioned comparatively inside a 2nd optical surface. Therefore, it is possible to avoid an unnecessarily large size of the optical pickup objective lens. In addition, since the third transfer surface is arranged at a position recessed from the convex portion on the opposite side to the first mold side, the degree of freedom of the arrangement of the third transfer surface is ensured, and the third transfer surface is arranged from the convex portion. In addition, the flange portion of the optical pickup objective lens can be made thicker by arranging it sufficiently deep. As a result, highly accurate transfer is possible with the resin pressure in the cavity during molding lowered, and an objective lens for an optical pickup having high heat resistance can be provided by reducing the residual internal stress. Further, by increasing the thickness of the flange portion, the thickness of the resin introduction gate can be increased.

  In a specific aspect or viewpoint of the present invention, in the above manufacturing method, the convex portion protrudes toward the first mold from the position of the outermost periphery of the second transfer surface. In this case, it is possible to avoid interference between the second transfer surface and the tip surface of the protrusion pin.

  In another aspect of the present invention, the third transfer surface is provided so as to be recessed on the side opposite to the first mold side from the outermost peripheral position of the second transfer surface. In this case, the thickness of the flange portion of the optical pickup objective lens can be reliably increased, and high accuracy and heat resistance can be obtained.

  In yet another aspect of the present invention, the tip surface of the protrusion pin is disposed outside the outermost circumference of the first transfer surface and the second transfer surface. In this case, it is possible to avoid interference between the second transfer surface and the tip surface of the ejection pin, and it is possible to prevent the ejection pin from affecting the central portion having the optical function of the optical pickup objective lens.

  In still another aspect of the present invention, the convex portion is provided to face a part of the tip surface of the protruding pin. In this case, since the width or size of the convex portion can be reduced, it is possible to avoid unnecessarily increasing the size of the objective lens for an optical pickup while securing the area of the mounting surface.

  In still another aspect of the present invention, the second mold includes a core mold provided with the second transfer surface and the third transfer surface, and an outer peripheral mold provided around the core mold. A step is provided in the boundary region between the first transfer surface and the third transfer surface. In this case, it is possible to prevent a burr formed between the core mold and the outer peripheral mold from protruding greatly toward the third transfer surface due to the step.

  The molding die for an optical pickup objective lens according to the present invention has (a) a first transfer surface for transferring a first optical surface formed on the optical information recording medium side of the lens, and the lens is released. A first mold provided with a projecting pin, (b) a second transfer surface for transferring a second optical surface formed on the light source side of the lens, and an outer peripheral side of the second optical surface. Between the second transfer surface and the third transfer surface, and at least a part of the tip end surface of the protrusion pin, and is located at a position opposite to the third transfer surface. It has the 2nd metal mold | die which has the convex part protruded on the 1 metal mold | die side, It is characterized by the above-mentioned.

  According to the above molding die, the second die has a convex portion at a position between the second transfer surface and the third transfer surface and facing the tip surface of the protruding pin, and this convex portion is the third transfer surface. Since the protrusion protrudes to the first mold side from the surface, it is possible to prevent the pin pin from hitting the third transfer surface and damaging the third transfer surface. Therefore, the objective lens for optical pickup after molding and release has a precise mounting surface formed by the smooth third transfer surface, and the assembly accuracy of the objective lens for optical pickup can be ensured.

  The objective lens for an optical pickup according to the present invention includes (a) a first optical surface formed on the optical information recording medium side, and (b) an optical information recording medium side provided on the outer peripheral side with respect to the first optical surface. An abutting surface having an abutting trace of the ejecting pin, (c) a second optical surface formed on the light source side, and (d) formed on the light source side and on the outer peripheral side with respect to the second optical surface. Between the mounting surface and (e) the second optical surface and the mounting surface, the back surface position of the abutting surface and a position that overlaps at least a part of the abutting surface when the abutting trace is projected in the optical axis direction It is provided, and it has a crevice which recedes to the butting surface side rather than a mounting surface.

  The objective lens for an optical pickup is formed by a molding die that prevents the occurrence of pin galling that hits and damages the protruding pin against the third transfer surface. Therefore, the objective lens for optical pickup after molding and release is smooth. It has a precise mounting surface formed by the third transfer surface, and can be assembled with high accuracy.

  In a specific aspect or viewpoint of the present invention, in the objective lens for an optical pickup, the concave portion is depressed closer to the abutting surface side than the position of the outermost periphery of the second optical surface. In this case, when the objective lens is molded, it is possible to avoid interference between the second transfer surface and the tip surface of the protrusion pin.

  In another embodiment of the present invention, NA is 0.75 or more and 0.9 or less. Further, when d is the thickness on the optical axis of the objective lens and f is the focal length at the working wavelength of the objective lens, 0.9 ≦ d / f ≦ 1.8 is satisfied. In this case, the optical pickup objective lens can reduce coma aberration while having a high NA, and can be incorporated into the optical pickup device with high accuracy.

It is a figure explaining the shaping | molding apparatus for enforcing the manufacturing method of 1st Embodiment. (A) is an end view of a fixed mold, and (B) is an end view of a movable mold. It is a side view of the objective lens shape | molded by the shaping | molding apparatus of FIG. (A) is a front view of the objective lens, and (B) is a back view of the objective lens. It is sectional drawing of an objective lens. It is a flowchart explaining a manufacturing process. It is sectional drawing of the shaping die for enforcing the manufacturing method of 2nd Embodiment. (A) is a front view of the objective lens, and (B) is a back view of the objective lens. It is sectional drawing of the objective lens shape | molded by the shaping die of FIG.

[First Embodiment]
Hereinafter, a method for manufacturing an optical pickup objective lens according to a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a view for explaining a molding apparatus for carrying out this manufacturing method, and FIG. 2A is a fixed mold as a second mold among the molding dies 40 constituting the molding apparatus of FIG. FIG. 2B is an end view of the mold 42 viewed from the A direction, and FIG. 2B is an end view of the movable mold 41 as the first mold among the molding dies viewed from the B direction. 3 is a side view of the objective lens OL as a molded product, FIGS. 4A and 4B are a front view and a back view of the objective lens OL, and FIG. 5 is a view of the objective lens OL. It is CC sectional drawing.

  The movable mold 41 and the fixed mold 42 constituting the molding mold 40 can be opened and closed with the parting line PL as a boundary. A cavity CV, which is a space formed between both molds 41 and 42 in the mold closed state shown in FIG. 1, corresponds to the shape of the objective lens OL as a molded product. The objective lens OL is made of plastic and includes a circular center portion OLa having an optical function and an annular flange portion OLb extending in the outer diameter direction from the periphery of the center portion OLa. This objective lens OL is a BD objective lens with NA of 0.85.

  The movable mold 41 is a first mold, and has a structure that enables the mirror core 52 as a movable-side core mold, and the mirror core 52 to be supported around the mirror core 52 and fixed integrally. An outer peripheral mold 51 having a plurality of projecting pins 54 that are released by projecting an objective lens OL as a molded product; and an advancing / retreating drive device 71 that moves the projecting pins 54 forward and backward from the outer peripheral mold 51 toward the fixed mold 42. With.

  In the movable mold 41, the outer peripheral mold 51 has an end face 51c that forms the parting line PL. Further, on the center side of the outer peripheral mold 51, a molding surface 51a for defining a flange region CVb in the cavity CV is provided. The molding surface 51a forms the back surface RS and the side surface SS of the flange portion OLb of the objective lens OL by transfer. In the vicinity of the cylindrical core insertion hole 56 provided in the outer peripheral mold 51, a pin insertion hole 55 that supports the protrusion pin 54 and guides the protrusion pin 54 slidably in a direction parallel to the axis AX of the mirror core 52. Are formed at equal intervals. An optical surface molding surface 52a for defining the central region CVa of the cavity CV is provided on the distal end side of the mirror core 52 that is fixed in a state of being inserted into the core insertion hole 56. The optical surface molding surface 52a embodies the first transfer surface, and is formed to be slightly concave, and molds one optical surface LSb of the central portion OLa of the objective lens OL. The optical surface LSb functions as a first optical surface that is disposed to face the BD that is an optical information recording medium during the operation. The mirror core 52 is directly supported and fixed on the base side of the outer peripheral mold 51 by screws or the like (not shown) so that the positional relationship between the optical surface molding surface 52a and the molding surface 51a can be maintained precisely. It has become.

  A flat circular front end surface 54a that defines a part of the flange region CVb is provided on the front end side of the protruding pin 54 inserted in the pin insertion hole 55 of the outer peripheral mold 51. This front end surface 54a is a portion for molding the butting surface PS in the back surface RS of the flange portion OLb of the objective lens OL. The protrusion pin 54 is driven by the advance / retreat drive device 71 and can move along the axis AX1 in the pin insertion hole 55. After the mold 40 is opened, the objective lens OL is released from the movable mold 41. When moving, it moves forward to the fixed mold 42 side, and moves back to the back side of the movable mold 41 at an appropriate timing after such mold release until mold closing. More specifically, the protrusion pin 54 is urged in the forward direction on the distal end side by the advance / retreat drive device 71, so that the end of the protrusion pin 54 protrudes from the molding surface 51a by a necessary amount, and the objective lens OL is fixed to the fixed mold. The objective lens OL after molding can be released from the movable mold 41. Note that the position of the protruding pin 54 indicated by a dotted line in FIG. 1 indicates a state in which the movement is restricted by the fixed mold 42, and protrudes beyond this when the objective lens OL protrudes. On the other hand, when the forward and backward drive device 71 stops urging the protrusion pin 54 in the forward direction, the tip surface 54a of the protrusion pin 54 is retracted to the position of the molding surface 51a by a return spring (not shown) provided in the forward and backward drive device 71. The protruding pin 54 is accommodated in the outer peripheral mold 51.

  The molding surface 51 a of the outer peripheral mold 51 is not flat around the core insertion hole 56 and has a plurality of shallow recesses 58 and 59. These concave portions 58 and 59 serve as transfer surfaces for forming low raised portions 18 and 19 provided on the back surface RS of the flange portion OLb of the objective lens OL. These raised portions 18 and 19 prevent the burr 15 as an abutting trace that is inevitably formed on the outer periphery of the abutting surface PS from projecting to the back side from the periphery, and the objective lens OL as a product. The convenience of the handling etc. is aimed at. Two adjacent recesses 59 have a shape different from that of the other recesses 58. This is used to express the directionality of the objective lens OL by the gap between the two recesses 59. In this example, the side opposite to the direction in which the resin injection gate exists by 180 ° is shown by both concave portions 59.

  The movable mold 41 is moved forward and backward with respect to the fixed mold 42 at an appropriate timing by the mold opening / closing drive device 72. Specifically, the mold opening / closing drive device 72 moves the movable mold 41 along the axis AX so as to be close to the fixed mold 42 when the mold is closed, so that the molds 41 and 42 are brought into close contact with each other to form the cavity CV. Form. Further, the mold opening / closing drive device 72 performs mold clamping by urging the movable mold 41 to the fixed mold 42 with a necessary pressure when the resin is injected into the cavity CV. On the other hand, the mold opening / closing drive device 72 moves the movable mold 41 so as to be separated from the fixed mold 42 along the axis AX when the mold is opened, and separates the objective lens OL as a molded product from the fixed mold 42. Do the type.

  The fixed mold 42 is a second mold, and includes a mirror core 62 as a core mold on the fixed side, and an outer peripheral mold 61 having a structure that supports the mirror core 62 and can be fixed integrally. Prepare.

  The outer peripheral mold 61 has an end face 61c that forms a parting line PL. A molding surface 61a for defining the outermost periphery of the flange region CVb in the cavity CV is provided on the center side of the outer peripheral die 61, that is, the innermost periphery of the end surface 61c. On the tip side of the mirror core 62 fixed in a state of being inserted into the core insertion hole 66, a molding surface 62a for defining the central region CVa and the main portion of the flange region CVb in the cavity CV is provided. ing. The molding surface 62a includes an optical surface molding surface S2 corresponding to the optical surface LSa of the center region CVa, a molding surface S3 corresponding to the mounting surface F1 among the surface FS of the flange portion OLb, and the center region CVa and the flange portion OLb. It is comprised by the molding surface S4 corresponding to the recessed part DP formed in the boundary. Here, the optical surface molding surface S2 is a concave surface, and the optical surface LSa transferred by the optical surface molding surface S2 functions as a second optical surface arranged on the laser light source side for reading or writing during the operation. To do. The radius of curvature of the second optical surface is smaller than the radius of curvature of the first optical surface. The mirror core 62 is directly supported and fixed on the base side of the outer peripheral mold 61 by screws or the like (not shown), so that the positional relationship between the molding surface S3 and the molding surface 61a is maintained precisely. ing.

  In the mirror core 62, when the outermost peripheral position D2 of the optical surface molding surface S2 corresponding to the optical surface LSa is compared with the position D3 of the molding surface S3 corresponding to the mounting surface F1, the molding surface S3 is deeper. Is formed. That is, the outermost periphery of the optical surface molding surface S2 protrudes toward the movable mold 41 with respect to the direction of the axis AX, and the molding surface S3 is in a position depressed on the opposite side to the movable mold 41 side. Has been placed. Further, when the position D2 of the outermost periphery of the optical surface molding surface S2 for the optical surface LSa is compared with the position D4 of the molding surface S4, they are formed at the same depth position. Therefore, when the position D3 of the molding surface S3 for the mounting surface F1 is compared with the position D4 of the molding surface S4, the molding surface S3 is formed at a position recessed on the side opposite to the movable mold side 41 side. Yes. That is, the molding surface S4 protrudes toward the movable mold 41 with respect to the direction of the axis AX, and the molding surface S3 is disposed at a position recessed on the opposite side to the movable mold 41 side.

  As described above, the molding surface S4 protrudes beyond the optical surface molding surface S2 that embodies the second transfer surface, and as a result, projects beyond the molding surface S3 that embodies the third transfer surface. The molding surface S3 is sufficiently separated from the movable mold 41. Thereby, in the objective lens OL, the flange portion OLb has a sufficient thickness at the portion of the mounting surface F1, and the resin injection pressure at the time of molding can be reduced. On the other hand, a thin concave portion DP is formed between the flange portion OLb and the central portion OLa. This concave portion DP corresponds to the provision of the annular convex portion 68 on the tip side of the mirror core 62, and the convex portion The molding surface S4 which is the tip surface of 68 functions as a restricting member that prevents the tip of the protruding pin 54 from coming into contact with the molding surface S3 for the mounting surface F1 when the mold is closed. That is, even if the return of the protruding pin 54 temporarily deteriorates due to the effects of resin waste, scratches on the sliding portion, etc., a part of the tip surface 54a of the protruding pin 54 hits the molding surface S4 of the convex portion 68 and is pushed back. So-called pin galling that damages the molding surface S3 for the mounting surface F1 can be prevented. That is, in the molding after pin galling occurs, the uneven scratches are transferred onto the mounting surface F1 of all molded products, but the pin 68 of the molding surface S3 for the mounting surface F1 by the convex portion 68 as described above. By preventing the occurrence of this, it is possible to prevent a reduction in the assembly accuracy of the objective lens OL. This point is particularly important in the case of a high NA lens with NA of 0.75 or more, and it is possible to prevent the occurrence of tilt that causes coma aberration when the objective lens OL is fixed. Further, when d is the thickness on the optical axis of the objective lens and f is the focal length at the working wavelength of the objective lens, the objective lens satisfying 0.9 ≦ d / f ≦ 1.8 is caused by tilt. Since the coma aberration problem is likely to be large, the effect of preventing the occurrence of tilt is great.

  In addition, the convex part 68 cannot make the width | variety d very much on the relationship arrange | positioned between the optical surface shaping | molding surface S2 for optical surfaces LSa, and the corresponding shaping | molding surface S3 for the attachment surface F1. Therefore, in this embodiment, as shown by a dotted line in FIG. 2A, the entire front end surface 54a of the protruding pin 54 is not opposed so as to be in contact with the molding surface S4 of the convex portion 68, but the front end surface 54a. Are arranged so as to face each other so that only a part thereof can come into contact with the molding surface S4. Moreover, the front end surface 54a of the projecting pin 54 is disposed outside the innermost circumference of the molding surface S4 of the convex portion 68, and as a result, more than the outermost circumference of the optical surface molding surface S2 for the optical surface LSa. Arranged outside. Further, the protruding pin 54 is provided on the outer peripheral mold 51 of the movable mold 41 and is disposed outside the outermost outer periphery of the optical surface molding surface 52 a of the mirror core 52. Therefore, it is possible to avoid the protrusion pin 54 from interfering with the optical surfaces LSa and LSb of the objective lens OL, and to prevent the protrusion pin 54 from affecting the optical function of the central portion OLa of the objective lens OL. Yes.

  In the objective lens OL, the mounting surface F1 is formed as the upper end surface of the annular convex portion 17, and a stepped portion 17 a that is recessed backward is formed on the outermost periphery of the convex portion 17. Correspondingly, a stepped portion 67 a protruding toward the movable mold 41 is formed on the outer periphery of the mirror core 62 of the fixed mold 42. The stepped portion 17a obtained by transferring the stepped portion 67a provided on the outer edge of the mirror core 62 has a gap that inevitably exists at the position of the outer periphery 65 of the mirror core 62 because the fixed side has a divided structure of the core type and the outer peripheral type. The burr 25 formed by the resin entering (clearance) is prevented from projecting to a position higher than the surface side, that is, higher than the mounting surface F1, to facilitate the assembly of the objective lens OL as a product. ing. Note that the protrusion amount of the stepped portion 67a with respect to the molding surface S3 is smaller than the protrusion amount of the convex portion 68 as the limiting member. For this reason, the tip of the protruding pin 54 whose return has deteriorated first hits the convex portion 68 and does not hit the stepped portion 67a. Reducing the amount of protrusion of the stepped portion 67a is advantageous in that the resin injection gate formed between the movable mold 41 and the fixed mold 42 can be thickened.

  For reference, as shown in FIG. 4 (A), a trace projection unit that projects a burr 15 as an abutment trace of the projection pin 54 from the back toward the optical axis OA on the surface FS of the flange part OLb of the objective lens OL. TP was added. It can be seen that the circular region of the trace projection portion TP and the bottom surface of the recess DP partially overlap.

  FIG. 6 is a flowchart conceptually illustrating a manufacturing method using the molding apparatus shown in FIG. First, the movable mold 41 and the fixed mold 42 are heated in advance to a temperature suitable for molding by a mold temperature controller (not shown). Thereby, the temperature of the surface of the metal mold | die part which forms the cavity CV in both metal mold | dies 41 and 42, or its vicinity is made into the temperature state suitable for shaping | molding.

  Next, the mold opening / closing drive device 72 is operated to advance the movable mold 41 toward the fixed mold 42 to start mold closing (step S11). By continuing the closing operation of the mold opening / closing drive device 72, the mold closing state in which the movable mold 41 and the fixed mold 42 are brought into contact with each other, and by further continuing the closing operation of the mold opening / closing drive device 72, the movable mold is performed. Clamping is performed to clamp 41 and the fixed mold 42 with necessary pressure (step S12).

  Next, an injection device (not shown) is operated to inject the molten resin into the cavity CV between the clamped movable mold 41 and the fixed mold 42 with a necessary pressure through a gate or the like. (Step S13).

  After the molten resin is introduced into the cavity CV, the molten resin in the cavity CV is gradually cooled by heat dissipation, so that the molten resin waits for solidification to such a degree that the molten resin can be released (step S14).

  Next, the mold opening / closing drive device 72 is operated to retract the movable mold 41 and perform mold opening to separate the movable mold 41 from the fixed mold 42 (step S15). As a result, the objective lens OL that is a molded product is released from the fixed mold 42 while being held by the movable mold 41.

  Next, the advancing / retreating drive device 71 is operated to project the objective lens OL by the ejecting pin 54 (step S16). Specifically, the four protruding pins 54 are protruded simultaneously, and the flange portion OLb of the objective lens OL is pushed out along the axis AX with good balance. As a result, the objective lens OL is urged against the distal end surface of the protruding pin 54 and pushed out toward the fixed mold 42, and the objective lens OL is released from the movable mold 41.

  The objective lens OL released from both molds 41 and 42 is carried out of the molding apparatus by gripping a sprue portion or the like extending from the gate portion (not shown) of the objective lens OL (step). S17). Further, the objective lens OL after being carried out is subjected to external processing such as removal of the gate portion to be a product for shipment.

  According to the manufacturing method of the present embodiment described above, the fixed mold 42 has the convex portion 68 at a position between the optical surface molding surface 52a and the molding surface S3 and facing the tip surface 54a of the protruding pin 54. Since the convex portion 68 protrudes further toward the movable mold 41 than the molding surface S3, the molds of the two molds 41 and 42 are projected in a state where the protruding pin 54 is poorly returned and protrudes on the inner surface of the movable mold 41. Even when closing or mold clamping is performed, the tip surface 54 a of the protruding pin 54 is pushed back by the convex portion 68. Accordingly, since the pin pin can hit the molding surface S3 and damage the molding surface S3 can be prevented, the objective lens OL after molding and releasing has a precise mounting surface F1 formed by the smooth molding surface S3. Thus, the assembly accuracy of the objective lens OL for the optical pickup can be secured.

  In the present embodiment, since the convex portion 68 provided between the optical surface molding surface 52a and the molding surface S3 faces at least a part of the tip surface 54a of the ejection pin 54, the ejection pin 54 is used as the optical surface molding surface. It can be arranged relatively inside 52a. Therefore, it is possible to avoid the objective lens OL from becoming unnecessarily large. In addition, since the molding surface S3 is arranged at a position that is sufficiently retracted from the convex portion 68, the degree of freedom of arrangement of the molding surface S3 is ensured, and the flange portion OLb of the objective lens OL can be made thick. As a result, high-precision transfer is possible with the resin pressure in the cavity CV being molded low, and the objective lens OL with high heat resistance can be provided by reducing the residual internal stress. Further, by increasing the thickness of the flange portion OLb, the thickness of the resin introduction gate (not shown) in the molding die 40 can be increased, and the degree of freedom of the shape can be increased.

[Second Embodiment]
Hereinafter, a method for manufacturing the optical pickup objective lens according to the second embodiment will be described. The manufacturing method of the second embodiment is a modification of the first embodiment, and parts that are not particularly described are the same as those of the first embodiment.

  FIG. 7 is a view for explaining a molding die 40 for carrying out this manufacturing method. 8A and 8B are a front view and a back view of the objective lens OL, and FIG. 9 is a CC cross-sectional view of the objective lens OL that is a molded product.

  In the present embodiment, the radial width of the flange portion OLb of the objective lens OL is wider than that in the first embodiment. However, there is no particular change in the arrangement of the protruding pins 54 and the shape of the convex portions 68. That is, the molding surface S4 that is the top surface of the convex portion 68 functions as a limiting member that prevents the tip surface 54a of the protruding pin 54 from coming into contact with the molding surface S3 for the mounting surface F1 when the mold is closed. However, the entire tip surface 54a of the protruding pin 54 is not opposed so as to be in contact with the molding surface S4 of the convex portion 68, but is disposed so as to be opposed so that a part of the tip surface 54a can be in contact with the molding surface S4. Has been. Moreover, the front end surface 54a of the protrusion pin 54 is disposed outside the innermost periphery of the molding surface S4 of the convex portion 68, and is disposed outside the outermost periphery of the optical surface molding surface S2 for the optical surface LSa. ing. Furthermore, the protruding pin 54 itself is disposed outside the outermost periphery of the optical surface molding surface 52 a of the mirror core 52. Therefore, the protrusion pin 54 is configured to avoid interference with the optical surfaces LSa and LSb of the objective lens OL.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications are possible. For example, the shape of the convex portion 68 formed on the fixed mold 42 is not limited to the illustrated embodiment, and can be various shapes. For example, the molding surface S4 which is the top surface of the convex portion 68 is not limited to a flat surface perpendicular to the axis AX, but may be a plane slightly inclined or curved with respect to a surface perpendicular to the axis AX. it can.

  Moreover, in the said embodiment, although the molding surface S4 which is the top surface of the convex part 68 is made the same height as the outermost periphery of the optical surface molding surface S2, as long as the molding surface S4 protrudes rather than the molding surface S3, a molding surface S4 can be made higher or lower than the outermost periphery of the optical surface molding surface S2.

  Further, the number of cavities CV provided in the molding die 40 constituted by the fixed die 42 and the movable die 41 is not limited to one, and a plurality of cavities CV can be provided. That is, for example, a plurality of mirror cores 62 can be embedded in the outer peripheral mold 61, and a plurality of sets of units including the mirror core 52 and the protruding pins 54 can be embedded in the movable mold 41 correspondingly. In this case, a plurality of objective lenses OL can be obtained by one-shot molding using both molds 41 and 42.

  Further, the shapes of the optical surface molding surfaces 52a, S2 and the molding surfaces 51a, 62a, S3 on the tip side of the mirror cores 52, 62 shown in FIG. 1 and the like are merely examples, and are appropriately determined according to the use of the objective lens OL. Can be changed.

  Further, the cross-sectional shape, arrangement, the number of components, etc. of the protruding pins 54 described in the above embodiment are merely examples, and can be changed as appropriate.

DESCRIPTION OF SYMBOLS 15 Burr 17 Convex part 17a Step part 25 Burr 40 Molding die 41 Movable mold 42 Fixed mold 51 Peripheral type 51a Molding surface 52 Mirror surface core 52a Optical surface molding surface 54 Pin 54a Tip surface 55 Pin insertion hole 56 Core insertion hole 61 Peripheral die 61a Molding surface 62 Mirror surface core 62a Molding surface 66 Core insertion hole 67a Stepped portion 68 Convex portion 71 Advance / retreat drive device 72 Mold opening / closing drive device AX, AX1 Shaft CV Cavity CVa Central region CVb Flange region DP Concave F1 Mounting surface LSa, LSb Optical surface OA Optical axis OL Objective lens OLa Center portion OLb Flange portion PS Abutting surface S2 Optical surface molding surface S3, S4 Molding surface TP Trace projection portion

Claims (16)

A first step of molding the lens with the first mold and the second mold closed;
A second step of releasing the lens from the second mold by separating the first mold and the second mold;
A third step of releasing the lens from the first mold using a protruding pin provided on the first mold side, and a manufacturing method of an objective lens for an optical pickup,
The first mold has a first transfer surface for transferring a first optical surface formed on the optical information recording medium side of the lens,
The second mold transfers a second transfer surface that transfers a second optical surface formed on the light source side of the lens, and a third transfer that transfers a mounting surface formed on the outer peripheral side of the second optical surface. Between the second transfer surface and the third transfer surface, at a position facing at least a part of the tip surface of the protrusion pin, and closer to the first mold than the third transfer surface. A method for producing an objective lens for an optical pickup, comprising: a protruding convex portion.   2. The method of manufacturing an objective lens for an optical pickup according to claim 1, wherein the convex portion protrudes toward the first mold from the position of the outermost periphery of the second transfer surface.   3. The optical pickup according to claim 2, wherein the third transfer surface is provided so as to be depressed on a side opposite to the first mold side from an outermost peripheral position of the second transfer surface. Method for manufacturing an objective lens.   4. The front end surface of the protruding pin is disposed outside the outermost periphery of the first transfer surface and the second transfer surface. 5. Of manufacturing an objective lens for optical pickup.   The said convex part is provided facing a part of front end surface of the said protrusion pin, The manufacture of the objective lens for optical pick-ups as described in any one of Claim 1- Claim 4 characterized by the above-mentioned. Method.   The second mold includes a core mold provided with the second transfer surface and the third transfer surface, and an outer peripheral mold provided around the core mold, and is provided between the core mold and the outer peripheral mold. The objective for an optical pickup according to any one of claims 1 to 4, wherein a step projecting from the third transfer surface to the first mold side is provided in the boundary region. Lens manufacturing method. A first mold having a first transfer surface for transferring a first optical surface formed on the optical information recording medium side of the lens and provided with an ejection pin for releasing the lens;
A second transfer surface for transferring a second optical surface formed on the light source side of the lens; a third transfer surface for transferring an attachment surface formed on the outer peripheral side of the second optical surface; A convex portion provided between the second transfer surface and the third transfer surface at a position facing at least a part of the tip end surface of the protrusion pin and protruding toward the first mold from the third transfer surface; A second mold having
A mold for forming an objective lens for an optical pickup.   8. The molding die for an optical pickup objective lens according to claim 7, wherein the convex portion protrudes closer to the first die than the position of the outermost periphery of the second transfer surface. 9.   9. The optical pickup according to claim 8, wherein the third transfer surface is provided so as to be recessed on a side opposite to the first mold side with respect to an outermost peripheral position of the second transfer surface. Mold for objective lens.   10. The front end surface of the protrusion pin is disposed outside the outermost periphery of the first transfer surface and the second transfer surface, according to claim 7. Mold for objective lens for optical pickup.   The said convex part is provided facing a part of front-end | tip surface of the said protrusion pin, The shaping | molding of the objective lens for optical pick-ups as described in any one of Claim 7-10 characterized by the above-mentioned. Mold.   The second mold includes a core mold provided with the second transfer surface and the third transfer surface, and an outer peripheral mold provided around the core mold, and is provided between the core mold and the outer peripheral mold. 12. The step according to claim 7, wherein a step is provided on the outer peripheral mold side so as to protrude from the third transfer surface to the first mold side in the boundary region. Mold for objective lens for optical pickup. A first optical surface formed on the optical information recording medium side;
An abutting surface provided on the outer peripheral side of the first optical surface on the optical information recording medium side and having an abutting trace of the projecting pin;
A second optical surface formed on the light source side;
A mounting surface formed on the light source side and on the outer peripheral side of the second optical surface;
Between the second optical surface and the mounting surface, the back surface position of the abutting surface is provided at a position that overlaps at least a part of the abutting surface when the abutting trace is projected in the optical axis direction. And a recess that recedes to the abutment surface side from the mounting surface;
An objective lens for an optical pickup comprising:   The objective lens for an optical pickup according to claim 13, wherein the recess is depressed closer to the abutting surface than the position of the outermost periphery of the second optical surface.   The objective lens for an optical pickup according to claim 13 or 14, wherein NA is 0.75 or more and 0.9 or less. The objective lens for an optical pickup according to any one of claims 13 to 15, wherein the following conditional expression is satisfied.
0.9 ≦ d / f ≦ 1.8
Here, d represents the thickness of the objective lens on the optical axis, and f represents the focal length of the objective lens at the used wavelength.