WO2009084377A1

WO2009084377A1 - Optical element manufacturing method, and optical element forming mold

Info

Publication number: WO2009084377A1
Application number: PCT/JP2008/072245
Authority: WO
Inventors: Shogo Yamamoto
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2007-12-28
Filing date: 2008-12-08
Publication date: 2009-07-09
Also published as: JPWO2009084377A1; CN101909842A

Abstract

Provided is an optical element manufacturing method, which can stably manufacture an optical element such as a high-NA lens having suppressed the occurrence or fluctuation of an aberration and which can release even the optical lens of a small size such as a small-diameter lens reliably from a forming mold. An annular movable sleeve (64a) formed around the mirror core (62) of a movable mold (42) is used to protrude the flange portion (OLb) of a lens (OL). Therefore, when this lens (OL) is released from the mirror core (62), a balanced force of a sufficient force can be applied to the entirety of the flange portion (OLb) of the lens (OL). As a result, the lens (OL) can be reliably released from the side of the movable mold (42). Thus, the lens (OL) can be stably manufactured, and a local force can be prevented from being applied to a portion of the flange portion (OLb), so that formed optical faces (LSa and LSb) can be prevented from being heterogeneously deformed.

Description

Optical element manufacturing method and optical element molding die

The present invention relates to a method of manufacturing an optical element such as a lens and an optical element molding die used in the manufacturing method.

As the first manufacturing method of the optical element, after the resin is injected into the cavity formed by the first mold and the second mold and molded, the mold is opened to retract the second mold. The second mold is operated by operating the core mold, which is an ejection mechanism provided in the second mold, and ejecting the optical function part of the molded product remaining in the second mold to the first mold side. There are those that release a molded product from a mold. (For example, refer to Patent Documents 1 and 2).

Further, as a second manufacturing method, after the mold opening for separating the second mold part from the first mold part, a plurality of pins as a plurality of protruding parts provided in the second mold part are projected. The molded product is released from the second mold by pushing the flange formed on the outer periphery of the optical functional surface of the molded product remaining in the second mold part to the first mold side. Is also present. (For example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 2002-200654 Japanese Patent Laid-Open No. 2002-200508 JP 2007-196665 A

However, in the first manufacturing method, since the core mold is advanced and retracted to project the molded product, the core mold is displaced or tilted with respect to the outer peripheral mold side for each molding shot. Since the relative shift amount and tilt amount between the optical function surfaces existing in each of the first die and the second die change from shot to shot, the shape accuracy is likely to fluctuate. There is a problem that aberrations become unstable. For example, regarding an objective lens for optical pickup, in the case of a high NA lens having an NA of 0.6 or more, coma generated due to a relative shift or a relative tilt between optical function surfaces becomes large. In particular, in the case of an objective lens for BD (Blu-Ray Disc) with NA of 0.80 or more, it is necessary to keep the relative shift within about ± 1.0μm and the relative tilt within about ± 0.02 °. Such protrusions that may be displaced or inclined with respect to the outer peripheral mold side are undesirable.

Further, in the second manufacturing method, the smaller the molded product is, the smaller the area of the flange portion with which the projecting pin comes into contact, and the smaller the diameter of each projecting pin. Therefore, the total cross-sectional area of all the pins that give the necessary release force at the time of protrusion also becomes small, and excessive pressure is applied to each pin. For example, as an objective lens for an optical pickup, a small-diameter lens having an outer diameter of 6 mm or less is frequently used. In this case, for example, in a small-diameter lens having an outer diameter of about 5 mm, the diameter of the pin is usually about 1 mm. In a small diameter lens of about 3.5 mm, the pin diameter is 0.4 mm or less. Therefore, a large force is locally applied to the contact portion of the pin in the flange portion, and there is a problem that the optical functional surface of the lens may be deformed unevenly. In addition, there is a problem that the durability of the pin is lowered, or in some cases, the pin is deformed and the lens cannot be protruded.

Therefore, the present invention can stably manufacture an optical element such as a high NA lens in which the occurrence and fluctuation of coma and other aberrations are suppressed, and even a small optical element such as a small-diameter lens can be molded. It is an object of the present invention to provide a method for manufacturing an optical element that can be reliably released from a mold and is less likely to cause deterioration in shape accuracy upon release.

Another object of the present invention is to provide an optical element molding die suitable for carrying out the above-described optical element manufacturing method.

In order to solve the above-described problems, a method of manufacturing an optical element according to the present invention includes (a) a first step of molding an optical element with a pair of molds configured by a first mold and a second mold, (B) a second step of releasing the optical element from the first mold by separating the first mold and the second mold, and (c) optics of the optical element provided in the second mold. The optical element is released from the core mold by projecting the flange surface formed around the optical surface of the optical element using a projecting member having an annular tip surface provided around the core mold forming the surface. And a third step.

According to the manufacturing method described above, in the third step, the flange surface of the optical element is projected using the projecting member having an annular tip surface provided around the core mold of the second mold. When releasing the mold, it is possible to give a sufficient release force balanced to the flange portion over the outer periphery outside the optical surface of the optical element, and it is possible to increase the area where the protruding member contacts the flange surface. . As a result, the optical element can be reliably released from the second mold side, which not only enables stable production of the optical element, but also applies a local force to a part of the flange surface after molding. The optical surface can be prevented from being deformed unevenly. Further, since it is not necessary to displace the core mold when releasing the optical element from the core mold, it is possible to prevent the core mold from being displaced at every molding shot in the second mold. It is possible to reduce the cause of positional deviation such that the molding surface and the molding surface of the second mold are relatively shifted or tilted. Therefore, it is possible to manufacture a large amount of high-performance optical elements that suppress the occurrence and fluctuation of various aberrations.

In a specific aspect or viewpoint of the present invention, in the first step of the manufacturing method, an optical element is molded by injecting a resin into a cavity formed by a pair of molds. In this case, a highly accurate resin optical element can be manufactured stably.

In yet another aspect of the present invention, in the third step, the projecting member is directed from the second mold to the first mold in a state where the core mold and the outer peripheral mold provided around the projecting member are fixed to each other. Move to. In this case, the relative arrangement relationship between the core type and the outer peripheral type does not change, and the arrangement relationship between the two can be stably maintained.

In still another aspect of the present invention, the first mold is a fixed mold and the second mold is a movable mold. In this case, a core mold and a protruding member are incorporated on the movable mold side.

In yet another aspect of the present invention, the optical element is a lens. In this case, it is possible to provide a high-performance lens that suppresses occurrence and fluctuation of coma aberration. In particular, in a high-performance optical pickup objective lens, specifically, a high NA lens having an image-side numerical aperture NA of 0.75 or more using a laser beam of 380 to 420 nm, the relative shift or tilt between both surfaces of the optical surface is used. Although there is a problem that the optical performance is significantly deteriorated even if a slight amount of is generated, this can be effectively prevented.

An optical element molding die according to the present invention is (a) an optical element molding die that molds an optical element with a pair of molds, and (b) an optical surface of the optical element is formed on one mold. A core mold and (c) an annular tip surface provided over the periphery of the core mold, and directed from one mold to the other mold in order to project a flange surface formed around the optical surface of the optical element And a protruding member capable of moving back and forth in the direction.

According to the above optical element molding die, one of the molds has an annular tip surface provided around the periphery of the core mold, and can be moved forward and backward in the direction from the one mold to the other mold. And the molding surface on one mold side is formed by at least the core mold and the protruding member, so that the flange surface formed around the optical surface of the optical element is protruded by using the protruding member. The optical element can be released from the core mold. At this time, since it is possible to give a sufficient release force balanced to the flange portion over the outer periphery outside the optical surface of the optical element, it is possible to reliably release the optical element from one mold side, In addition to enabling stable production of the optical element, it is possible to prevent the optical surface after molding from being deformed unevenly due to a local force applied to a part of the flange surface. In addition, since it is not necessary to displace the core mold when releasing the optical element from the core mold, it is possible to prevent the core mold from being displaced every molding shot in one mold. Produces a large amount of high-performance optical elements that can reduce the occurrence of various aberrations and fluctuations by reducing the cause of misalignment between the molding surface and the molding surface of the other mold. can do.

In a specific aspect of the present invention, in the optical element molding die, one of the molds has an outer peripheral mold provided around the protruding member. In this case, the optical element can be released from the core mold while preventing the optical element from falling by the outer peripheral guide.

In another aspect of the present invention, the clearance between the core mold and the protruding member and the clearance between the protruding member and the outer peripheral mold are different in size, and the position of the leading portion of the larger clearance is the leading edge of the smaller clearance. It is comprised so that it may protrude in the other metal mold | die side rather than the position of the part. In this case, the molding burr corresponding to the larger clearance can be arranged on the other mold side, and the position where the molding burr occurs can be recessed to suppress the projection of the molding burr from the optical element.

Note that the clearance head has the following meaning. That is, the clearance is a gap generated between two molds, and the tip is the portion located on the other mold side. Therefore, for example, in FIG. 4, it corresponds to the edge LSb1 and the edge F11.

In yet another aspect of the present invention, the clearance between the core mold and the protruding member is larger than the clearance between the protruding member and the outer peripheral mold. In this case, the expensive core mold can be prevented from being damaged by advancing and retracting the protruding member, and the lifetime can be extended.

In yet another aspect of the present invention, the clearance between the core mold and the protruding member is smaller than the clearance between the protruding member and the outer peripheral mold, and the shape of the annular front end surface of the protruding member is the outer peripheral mold side than the core mold side. It protrudes toward the other mold. In this case, a molding burr is relatively difficult to be formed around the molding surface corresponding to the clearance between the core mold and the protruding member, or the molding burr corresponding to the clearance between the protruding member and the outer peripheral mold can be reduced. The position where the molding burr occurs is recessed by being arranged on the side, and the projection of the molding burr from the optical element can be suppressed.

In yet another aspect of the present invention, the annular tip surface of the protruding member is a molding surface for transferring and forming at least a part of the flange surface of the optical element. In this case, a molding surface for forming the flange surface is constituted by at least the annular tip surface of the protruding member.

It is a sectional side view explaining the structure of the fixed metal mold | die of 1st Embodiment, and a movable metal mold | die. It is a partially expanded sectional view of the metal mold | die of FIG. FIG. 2 is a partially enlarged end view of the movable mold in FIG. 1. It is the elements on larger scale of the lens shape | molded by the metal mold | die of FIG. It is a front view explaining the manufacturing method etc. of 2nd Embodiment. It is a front view explaining the manufacturing method etc. of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 41 ... Fixed mold 42 ... Movable mold 51 ... Peripheral mold 52 ... Mirror surface core 53 ... Fixed lid 56 ... Molding mirror surface 56a ... Optical surface molding surface 56b ... Molding surface 61 ... Outer peripheral mold 62 ... Mirror surface core 64 ... Movable sleeve 64d ... Core insertion hole 65 ... Core / sleeve insertion hole 66a ... Optical surface molding surface 66b ... Molding surface 66c ... Molding surface 67 ... Advance mechanism 68 ... Retraction mechanism 69 ... Spacer 73 ... Sleeve ejecting pin 74 ... Pin drive plate 76 ... Shoulder bolt 77 ... Spring AX ... Shaft CV ... Cavity LSa, LSb ... Optical surface OL ... Molded product OA ... Optical axis OL ... Lens OLa ... Center part OLb ... Flange part PL ... Parting line

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

FIG. 1 is a partial side sectional view for explaining the structure of a mold composed of a fixed mold 41 and a movable mold 42, and FIG. 2 is an enlarged sectional view of a P1 portion in FIG. These are the arrow views which looked at the movable metal mold | die 42 from the A direction. FIG. 4 is a partially enlarged view of a lens that is injection-molded by the mold shown in FIG. Although a case where a horizontal molding machine is used will be described here, a vertical molding machine may be used.

The fixed mold 41 and the movable mold 42 can be opened and closed with the parting line PL as a boundary. A cavity CV (see FIG. 2), which is a space between both

molds

41 and 42, corresponds to the shape of the lens OL as an optical element that is a molded product. The lens OL is made of plastic and includes a center portion OLa having an optical function and an annular flange portion OLb extending from the center portion OLa in the outer diameter direction. Here, the outer diameter of the lens OL formed by the two

molds

41 and 42 is 6 mm or less. As for the outer diameter of the lens OL, for example, when φ3.5 mm or less, the mold according to the present embodiment increases the effect of ensuring accuracy during molding of the lens OL, and when φ2.0 mm or less, the mold according to the present embodiment. As a result, the effect of ensuring accuracy is enhanced particularly when the lens OL is molded.

The fixed mold 41 includes a mirror core 52 as a fixed-side core mold, and a fixed lid 53 that integrally fixes the outer peripheral mold 51 and the mirror core 52. In addition, the outer periphery type | mold 51 has the end surface 51a which forms the parting line PL. In addition, a core insertion hole 55 for inserting and supporting the mirror core 52 is formed in the outer peripheral mold 51.

The movable mold 42 has a mirror core 62 as a movable core mold, an outer peripheral mold 61 having a structure that supports the movable core mold and can be fixed integrally, and a lens OL. A movable sleeve 64 as a protruding member to be released from the mold, a forward movement mechanism 67 for moving the movable sleeve 64 forward to the fixed mold 41 side, and a retraction mechanism 68 for moving the movable sleeve 64 backward are provided.

The outer periphery type | mold 61 has the end surface 61a which forms the parting line PL. A core / sleeve insertion hole 65 for inserting and supporting the mirror core 62 and the movable sleeve 64 is formed in the outer peripheral die 61. The core / sleeve insertion hole 65 has a small diameter on the fixed mold 41 side, and a large diameter on the retreat mechanism 68 side. Further, the coaxiality between the small diameter portion and the large diameter portion is about 1 μm or less. Further, the coaxiality with the large-diameter portion that forms the outer peripheral molding surface 66c of the flange portion that mainly molds the outer periphery of the flange portion OLb is set to about 5 μm or less.

The mirror core 62 is inserted into the core insertion hole 64d of the movable sleeve 64 on the distal end side, and is inserted into the core / sleeve insertion hole 65 of the outer peripheral mold 61 on the root side, and is fixed to the outer peripheral mold 61 on the root side. The front end portion of the mirror core 62 has a cylindrical outer peripheral surface, and allows movement along the axis AX of the movable sleeve 64 to be described later within the core insertion hole 64d having the corresponding inner peripheral surface. . An optical surface molding surface 66a for forming a cavity CV is provided on the tip surface provided at the tip of the mirror core 62. The optical surface molding surface 66a is a concave surface and molds one optical surface LSb of the center portion OLa of the lens OL. The mirror core 62 is directly supported on the outer peripheral die 61 with screws or the like, so that the positional relationship between the optical surface molding surface 66a and the flange forming portion 63 is maintained precisely. Although omitted in the drawings, a spacer can be interposed between the front end surface of the root portion of the mirror core 62 and the rear end surface of the outer peripheral mold 61. Thereby, the space | interval of the optical surface molding surface 66a of the mirror surface core 62 and the optical surface molding surface 56a of the mirror surface core 52 which opposes this can be adjusted now.

The movable sleeve 64 is inserted into the core sleeve insertion hole 65 of the outer peripheral die 61. The distal end portion of the movable sleeve 64 has a cylindrical small-diameter outer peripheral surface, and is movable along the axis AX within the core sleeve insertion hole 65 having an inner peripheral surface of a corresponding shape. Further, the root portion of the movable sleeve 64 also has a cylindrical large-diameter outer peripheral surface, and is slidable along the axis AX in the core sleeve insertion hole 65 having the corresponding inner peripheral surface. It has become. That is, the movable sleeve 64 can move forward or backward in the fixed mold 41 side within the core sleeve insertion hole 65 of the outer peripheral die 61. At the tip of the movable sleeve 64, there is provided a molding surface 66b that forms part of the flange forming portion 63 for forming the cavity CV. The molding surface 66b molds the flange surface F1 of the flange portion OLb of the lens OL, that is, one annular end surface in cooperation with the molding surface 66c that forms a part of the flange forming portion 63 that is a part of the outer peripheral die 61. To do. A spacer 69 is inserted between the rear end surface of the movable sleeve 64 and the front end surface of the large-diameter base portion of the mirror core 62. By inserting spacers having different thicknesses, the molding surface 66b, The distance from the optical surface molding surface 56a facing this can be adjusted. The spacer 69 can be fixed to either the movable sleeve 64 or the mirror core 62.

The advance mechanism 67 abuts the spacer 69 and applies a forward biasing force to the movable sleeve 64, and a pin drive that supports the rear end portion 73a of the sleeve protrude pin 73 and advances and retracts in the axial direction. Plate 74. The sleeve protruding pin 73 is inserted in a non-contact manner into a pin hole formed so as to penetrate the mirror core 62 and the rear plate 78 of the retracting mechanism 68, and extends parallel to the axis AX of the movable sleeve 64 and along the axis AX. It is possible to advance and retreat. Although only one sleeve protruding pin 73 is shown in the drawing, it is preferable that about 2 to 6 sleeves are arranged with the axis AX being symmetrical. The pin drive plate 74 is driven by an ejector rod of a molding machine (not shown) and is displaced along the axis AX by a distance necessary for mold release at an appropriate timing.

The retraction mechanism 68 includes a spring fixing shoulder bolt 76 fixed to the movable sleeve 64 at the tip, a return spring 77 held by the shoulder bolt 76, and a rear plate 78 for storing the shoulder bolt 76 and the like. The shoulder bolt 76 is inserted in a non-contact manner into a pin hole 79b formed so as to penetrate the mirror core 62 and the rear plate 78, extends parallel to the axis AX of the movable sleeve 64, and can advance and retreat in the direction of the axis AX. It has become. However, since the return spring 77 is sandwiched between the head portion of the shoulder bolt 76 and the rear end of the specular core 62 and urges the movable sleeve 64 rearward, the movable sleeve 64 normally faces the rear plate 78 side. The urging force that is retained in the retracted state is received, and the force from the pin drive plate 74 is received to project the necessary amount. Although omitted in the drawing, a spacer can be interposed between the mirror core 62 and the rear plate 78. Although only one retracting mechanism 68 is shown in the drawing, it is preferable that about 2 to 6 shafts AX are symmetrically arranged at positions where they do not interfere with the sleeve protruding pin 73.

Among the above molds, in the fixed mold 41, the fitting clearance (hereinafter also simply referred to as clearance) A1 of the large-diameter fitting portion between the outer peripheral mold 51 and the mirror core 52 is, for example, about 1 μm or less. To do. (Hereinafter, the clearance value indicates the difference between the outer diameter (diameter) and the inner diameter (diameter).) Further, the clearance A3 of the fitting portion on the small diameter side may be reduced to about 1 μm or less, and is attached to the lens OL. The clearance may be increased (for example, about 2 to 10 μm) as long as a molding burr that does not affect the thickness is generated. Further, in the movable mold 42, the clearance A2 of the fitting portion on the large diameter side between the outer peripheral mold 61 and the mirror core 62 is, for example, about 1 μm or less like the clearance A1.

Among the above molds, in the movable mold 42, the clearance B1 corresponding to the inter-surface distance between the outer peripheral surface of the tip end portion of the mirror core 62 and the inner peripheral surface of the core insertion hole 64d of the movable sleeve 64 is, for example, The diameter is about 3 to 10 μm. Further, in the movable mold 42, a clearance B2 corresponding to the inter-surface distance between the outer peripheral surface of the distal end portion of the movable sleeve 64 and the inner peripheral surface of the core sleeve insertion hole 65 in the flange forming portion 63 of the outer peripheral die 61. As with the clearance B1, the diameter is, for example, about 3 to 10 μm. Further, the clearance B3 corresponding to the inter-surface distance between the large-diameter base portion of the movable sleeve 64 and the inner peripheral surface of the core sleeve insertion hole 65 on the base side of the outer peripheral die 61 is the clearance between the inside and the outside of the movable sleeve 64. Within a range smaller than B1 and B2, the range is, for example, about 1 to 5 μm. By making the clearances B1 and B2 somewhat larger than the clearance B3, it is possible to prevent the small diameter portion 62a and the movable sleeve 64 from coming into contact with surrounding parts and causing scratches, thereby causing defects in the appearance due to scratches on the lens OL. Can be prevented. In addition, if the clearance is about 3 to 10 μm, even if burrs due to the clearance occur in the lens OL, it can be suppressed to a level that can be ignored.

In the present embodiment, the thickness t1 in the radial direction of the distal end portion of the movable sleeve 64 of the movable mold 42 is made narrower than the width t2 in the radial direction of the flange portion OLb of the lens OL. The outer edge of OLb is formed. Thereby, it becomes easy to ensure shape accuracy such as the thickness of the outer edge portion of the flange portion OLb. Here, the dimensional ratio t1 / t2 is preferably about 0.5 to 0.9, for example, and more preferably about 0.7 to 0.9. By setting the dimensional ratio t1 / t2 to be 0.7 or more, it is possible to ensure the effect of providing a well-balanced projecting force to the entire flange portion OLb and reducing the projecting pressure, and the lens OL can be stably ejected. The deformation due to the protrusion of the lens OL can be suppressed. Further, by setting the dimensional ratio t1 / t2 to 0.9 or less, the flange forming portion is adjacent to the outer edge side of the molding surface 66b at the tip of the movable sleeve 64 of the movable mold 42 among the molding surfaces of the outer peripheral die 61. A molding surface 66d having a sufficient size for 63 can be secured. The molding surface 66d corresponds to the end surface portion 66f that protrudes toward the disk side of the flange surface F1 of the flange portion OLb. By providing such a molding surface 66d, the movable sleeve 64 can be prevented from coming into contact with the flange forming portion 63 of the outer peripheral die 61, and the movability of the protruding operation by the movable sleeve 64 can be enhanced.

Further, depending on manufacturing errors, the front end surface of the movable sleeve 64 of the movable mold 42 is retracted from the optical surface molding surface 66a of the mirror core 62, and the leading portion of the clearance B1 between the movable sleeve 64 and the mirror core 62 is obtained. 4 moves to the left side in the drawing of FIG. 4, there is a possibility that the molding burr generated in the clearance B1 may protrude from the apex of the optical surface LSb on the disc side (intersection of the optical surface LSb and the optical axis OA). . For this reason, in the present embodiment, the distal end surface of the movable sleeve 64 is located inside the cavity CV rather than the leading portion of the clearance between the movable sleeve 64 and the outer peripheral mold 61 and the leading portion of the clearance between the movable sleeve 64 and the mirror core 62. The distance d1 is projected. Thereby, in the lens OL after molding, one of the starting points of the molding burr is on the entire circumference of the outermost edge LSb1 of the optical surface LSb and the other is on the entire circumference of the outermost edge F11 of the recessed flange surface F1. Therefore, it is possible to reliably prevent the molding burr from protruding beyond the top of the optical surface LSb on the disk side, and the molding burr affects the mounting of the lens OL, that is, the working distance of the lens OL is influenced by the molding burr. The risk of fluctuation can be reduced.

In the present embodiment, an example is shown in which the position of the leading portion of the clearance between the movable sleeve 64 and the outer peripheral mold 61 and the position of the leading portion of the clearance between the movable sleeve 64 and the mirror core 62 are the same position. However, if the positions of the heads of the clearances are different, the clearance head located closer to the other mold (fixed mold 41) side is positioned more than the position of the head of the clearance. What is necessary is just to protrude the front end surface of the movable sleeve 64 in the cavity CV by the distance d1.

An optical element is manufactured using the above molds. According to this, the flange portion OLb of the lens OL is projected using the annular tip surface, that is, the molding surface 66b provided at the tip of the annular movable sleeve 64 provided around the mirror core 62 of the movable mold 42. When releasing the lens OL from the mirror core 62, the area of the protruding portion can be increased, and a balanced release force can be applied to the entire flange portion OLb of the lens OL. Thereby, the lens OL can be reliably released from the movable mold 42 side, the lens OL can be stably manufactured, and the durability of the movable mold 42 including the movable sleeve 64 and the like is improved. Can do. Further, it is possible to prevent the optical surfaces LSa and LSb after molding from being deformed unevenly due to a local force applied to a part of the flange portion OLb. Further, since it is not necessary to displace the mirror core 62 when releasing the lens OL from the mirror core 62, it is possible to prevent the mirror core 62 from being displaced every molding shot in the movable mold 42. It is possible to reduce a factor that the optical surface molding surface 56a of the mold 41 and the optical surface molding surface 66a of the movable mold 42 are relatively shifted or tilted. Therefore, it is possible to manufacture a large number of high-performance lenses OL that suppress the occurrence and fluctuation of various aberrations.

Specifically, the movable sleeve 64 is displaced in the movable mold 42, but the mirror core 62 is fixed. Therefore, the relative shift between the pair of optical surfaces LSa and LSb of the lens OL and the occurrence and fluctuation of the relative tilt are suppressed. And the occurrence of coma aberration in the lens OL can be suppressed. By using the

core precision molds

41 and 42 as described above, for example, an objective lens for an optical pickup having a lens OL of NA 0.65 or more (specifically, including an objective lens for HD DVD with NA 0.65) is used. In particular, in the case of an objective lens for NA of 0.75 or higher (including a BD objective lens for NA of 0.85 as a specific example), the relative shift can be suppressed within about ± 1.0 μm, and the relative tilt Can be suppressed within about ± 0.02 °, so that a high-performance objective lens with reduced coma and the like can be obtained.

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

FIG. 5 is an enlarged cross-sectional view of the mold according to the present embodiment. As is apparent from the figure, in the movable mold 42, the molding surface 66d of the outer peripheral die 61 and the distal end surface of the movable sleeve 64 are substantially matched. However, the distal end surface of the movable sleeve 64 protrudes from the distal end position of the mirror core 62 toward the mirror core 52 by a distance d1 as in the first embodiment. In this case, the molding burr formed by the clearance B2 between the outer peripheral die 61 and the movable sleeve 64 is formed at a position farther from the apex of the optical surface LSb on the disc side with respect to the direction of the optical axis OA. Become. Therefore, even when the outer clearance B2 of the movable sleeve 64 is made larger than the inner clearance B1, the molding burr affects the mounting of the lens OL, that is, the working distance of the lens OL fluctuates due to the molding burr. Can be prevented. In such a case, the clearance B3 (see FIG. 1) is also made larger than the clearance B1, so that the contact location during the ejector operation can be limited to only between the movable sleeve 64 and the mirror core 62. Compared with the case where there are a plurality of contact locations, the number of occurrences of scratches caused by contact between members can be reduced, and molding defects such as operation failures can be reduced.

[Third Embodiment]
Hereinafter, a method for manufacturing an optical element according to the third embodiment will be described. Note that the manufacturing method according to the third embodiment is a modification of the second embodiment, and parts that are not particularly described are the same as those in the second embodiment.

FIG. 6 is an enlarged cross-sectional view of the mold according to the present embodiment. In this case, in the movable mold 42, the molding surface 66d of the outer peripheral die 61 and the end surface on the outer peripheral side of the movable sleeve 64 are made to substantially coincide with each other, and the end surface on the inner peripheral side of the movable sleeve 64 is more than the end surface on the outer peripheral side. It is recessed by a distance d3. Further, the end surface on the inner peripheral side of the movable sleeve 64 protrudes from the outer peripheral end of the optical surface molding surface of the mirror core 62 toward the fixed mold 41 by a distance d2. Therefore, the flange molding surface 66 d of the outer peripheral mold 61 protrudes by a distance d 4 (> d 2) closer to the fixed mold 41 than the position of the end surface on the inner peripheral side of the mirror core 62. In the case of the third embodiment, compared to the case of the second embodiment, the molding burr formed by the clearance B2 outside the movable sleeve 64 is the optical surface LSb on the disc side with the direction of the optical axis OA as a reference. It is formed at a position further away from the apex of. Therefore, even when the outer clearance B2 of the movable sleeve 64 is made larger than the inner clearance B1, the molding burr affects the mounting of the lens OL, that is, the working distance of the lens OL fluctuates due to the molding burr. Can be prevented. In such a case, the clearance B3 (see FIG. 1) is also made larger than the clearance B1, so that the contact location during the ejector operation can be limited to only between the movable sleeve 64 and the mirror core 62. Compared with the case where there are a plurality of contact locations, the number of occurrences of scratches caused by contact between members can be reduced, and molding defects such as operation failures can be reduced.

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 number of cavities CV provided in the mold constituted by the fixed mold 41 and the movable mold 42 is not limited to one, and a plurality of cavities CV can be provided. That is, for example, a plurality of mirror cores 52 can be embedded in the outer peripheral mold 51, and a plurality of sets of units including the mirror core 62 and the movable sleeve 64 can be embedded in the movable mold 42 correspondingly. In this case, a plurality of lenses OL can be obtained by one-shot molding using both

molds

41 and 42.

Further, the shape of the optical surface molding surface 56a on the distal end side of the mirror core 52 and the shape of the optical surface molding surface 66a on the distal end side of the mirror core 62 shown in FIG. 2 and the like are merely examples, and are used for applications such as a lens OL. It can be changed accordingly. For example, it is possible to mold a lens having a surface with a large curvature on the movable mold 42 side by switching the shapes of both optical surface molding surfaces 56a and 66a.

Further, as shown in FIG. 3 and the like, the distal end portion of the movable sleeve 64 has a cylindrical outer shape, but may have a cylindrical shape having various cross-sectional shapes such as a quadrangle. However, by using a cylindrical shape with a circular cross section, the movable mold 42 can be easily manufactured, and the accuracy of the movable mold 42 can be increased.

Further, in the third embodiment, a step whose height changes along the radial direction is provided on the distal end surface of the movable sleeve 64. However, the present invention is not limited to this, and a step whose height changes along the circumferential direction is provided. It can also be provided.

Further, the lens OL is not limited to plastic, and a glass lens can be manufactured by a molding apparatus 100 in which

similar molds

41 and 42 are incorporated.

Claims

A first step of molding an optical element with a pair of molds composed of a first mold and a second mold;
A second step of releasing the optical element from the first mold by separating the first mold and the second mold;
Using a protruding member having an annular tip surface provided around the core mold that forms the optical surface of the optical element provided in the second mold, formed around the optical surface of the optical element. And a third step of releasing the optical element from the core mold by protruding a flange surface.
2. The optical element manufacturing method according to claim 1, wherein in the first step, the optical element is molded by injecting a resin into a cavity formed by the pair of molds. Method.
In the third step, the protruding member is moved in the direction from the second mold toward the first mold in a state where the core mold and the outer peripheral mold provided around the protruding member are fixed to each other. The method for manufacturing an optical element according to claim 1, wherein:
The said 1st metal mold | die is a fixed metal mold | die, The said 2nd metal mold | die is a movable metal mold | die, The any one of Claim 1 thru | or Claim 3 characterized by the above-mentioned. Of manufacturing the optical element.
The method of manufacturing an optical element according to any one of claims 1 to 4, wherein the optical element is a lens.
An optical element molding die for molding an optical element by a pair of molds,
One mold includes a core mold that forms an optical surface of the optical element, and a flange surface that is formed around the optical surface of the optical element having an annular tip surface provided around the core mold. An optical element molding die comprising: a projecting member capable of advancing and retreating in the direction from the one mold to the other mold in order to project.
The optical element molding die according to claim 6, wherein the one mold has an outer peripheral mold provided around the protruding member.
The clearance between the core mold and the protruding member is different from the clearance between the protruding member and the outer peripheral mold, and the position of the leading portion of the larger clearance is more than the position of the leading portion of the smaller clearance. The optical element molding die according to claim 7, wherein the optical element molding die is also configured to protrude toward the other mold side.
9. The clearance between the core mold and the protruding member is larger than the clearance between the protruding member and the outer peripheral mold, and is defined in any one of claims 7 and 8. Optical element molding die.
The clearance between the core mold and the protruding member is smaller than the clearance between the protruding member and the outer peripheral mold,
The shape of the annular front end surface of the protruding member protrudes toward the other mold on the outer peripheral mold side rather than the core mold side. Optical element molding die.
11. The annular surface of the projecting member is a molding surface for transferring and forming at least a part of the flange surface of the optical element. The optical element shaping | molding die as described in any one of these.