JPWO2012043224A1 - Optical element manufacturing method - Google Patents

Abstract

It is an object of the present invention to provide a method for manufacturing an optical element that can reduce deformation and scratches on an optical surface when a molded part 100 is taken out by protruding a core part for mold release. The core portion 64a is moved to the first mold 41 side while keeping the flange portion FL, which is a part of the lens LP, in contact with the holding portion 64b, thereby separating the core portion 64a from the first optical surface OS1 of the lens LP. And the step of moving the core portion 64a again to the second mold 42 side to release the lens LP from the holding portion 64b, thereby achieving substantial release of the core portion 64a and the lens LP. In this state, the lens LP can be removed from the core portion 64a by holding the runner portion RP other than the lens LP. Thereby, deformation and scratches of the optical surfaces OS1, OS2, etc. when the molded product 100 is taken out can be reduced, and a high-quality lens LP can be provided.

Description

  The present invention relates to a method for manufacturing a resin optical element, and more particularly to a method for manufacturing an optical element with a runner portion using an injection molding apparatus.

  As a method for manufacturing a resin lens, a method called injection molding is known, but it is necessary to project the resin lens to the outside when releasing the resin lens after shape transfer from the mold surface. As such a resin lens projecting process, for example, a core mold part for optical surface transfer (hereinafter referred to as a core part) is advanced so as to protrude from the surrounding mold part, thereby enabling the resin lens to be taken out. There is a thing (patent document 1).

  However, in the case of a resin lens that has a large curvature and fits deeply into the mold surface, the molded product is removed from the mold by holding the runner and sprue parts that extend from the resin lens after the resin lens protrusion process. When taking out, a resin lens sticks to a core part and a gate part will bend. Such deformation of the gate part may cause minute deformation to the optical surface of the resin lens, or because the lens is tilted and released, an uneven release force is applied and the optical surface is minutely deformed. As a result, a desired optical surface cannot be obtained or the yield rate of the product is lowered. In particular, an objective lens for BD has a large curvature and a large projection amount, which tends to deepen the transfer surface of the core portion, and the size of the lens portion is small even though high shape accuracy is required for the lens portion. Thus, the gate portion tends to easily deform the optical surface, and it is desirable to reduce the deformation of the optical surface at the time of mold release. In addition, if the lens is tilted and released due to the deformation of the gate part, the optical surface of the lens may come into contact with the mold at the time of releasing, and the optical surface of the lens may be damaged like a crescent. Even in this case, the desired optical surface cannot be obtained as a result, or the yield rate of the product is lowered. Therefore, it is desirable to reduce scratches on the optical surface at the time of mold release.

JP 2005-288940 A

  An object of the present invention is to provide an optical element manufacturing method capable of reducing deformation and scratches on an optical surface when a molded part is taken out by protruding a core part for mold release.

  In order to solve the above problems, an optical element manufacturing method according to the present invention is a method for manufacturing an optical element with a runner portion using an injection molding apparatus, and the injection molding apparatus includes a first optical surface of the optical element. A first mold to be molded and a second mold to mold the second optical surface of the optical element, and the first mold has a core part and a holding part for holding the core part. Assuming that. Furthermore, the method for manufacturing an optical element according to the present invention includes a step of injecting a molten resin into a cavity formed by a first mold and a second mold to mold the optical element, and the first mold A step of opening the mold by relatively moving the first mold and the second mold so as to leave the optical element, and moving the core portion to the second mold side to move the optical element to the first mold The core part is moved to the first mold side while maintaining a state in which a part of the optical element is in contact with the holding part, and the first optical surface of the core part and the optical element. And the step of moving the core part to the second mold side again to project the optical element again to the second mold side, separating the optical element from the holding part, and holding the parts other than the optical element And a step of removing the optical element from the core portion.

  According to the above manufacturing method, in a state where a part of the optical element is in contact with the holding part, the core part is moved to the first mold side to separate the core part and the first optical surface of the optical element; A step of moving the core part to the second mold side again to separate the optical element from the holding part, and in a state in which substantial release of the core part and the optical element has been achieved. By holding this portion, the optical element can be removed from the core portion. Thereby, the deformation | transformation and damage | wound of an optical surface at the time of taking out a molded article can be reduced, and a high quality optical element can be provided.

  According to a specific aspect or aspect of the present invention, in the manufacturing method, the optical element is an optical element for an optical pickup device that records and / or reproduces information on an optical information recording medium. In this case, recording and / or reproduction can be performed with high accuracy by a high-performance optical element obtained by releasing the core protruding type.

  In another aspect of the present invention, the optical element is used for an objective lens of an optical pickup device. The objective lens of the optical pickup device requires particularly high optical characteristics. Therefore, if the deterioration of the optical surface can be prevented by preventing the mold release deformation, it is easy to manufacture the objective lens satisfying the optical specifications.

  In still another aspect of the present invention, when NA is a numerical aperture of an optical element necessary for recording and / or reproducing information on an optical information recording medium, 0.75 ≦ NA ≦ 0.90. is there. A high NA lens for an optical pickup device typified by an objective lens for BD is required to have extremely high optical characteristics. Therefore, it is extremely important to prevent deterioration of the optical surface by preventing mold release deformation and the like.

  In still another aspect of the present invention, when the thickness on the optical axis of a lens as an optical element is d (mm) and the focal length of the lens in a light beam having a wavelength of 500 nm or less is f (mm), 0.9. ≦ d / f ≦ 3.0. Such a lens has a center thickness that is relatively thick with respect to the focal length, and easily adheres to the mold surface. However, as in the present invention, the optical element is achieved in a state in which substantial separation between the core portion and the optical element is achieved. By removing the optical element from the core part by holding other parts, it is possible to reliably prevent mold release deformation and the like.

  In still another aspect of the present invention, when the depth of the first optical surface of the lens as an optical element is S (mm) and the surface diameter of the first optical surface is R (mm), 0.75 ≦ S / R ≦ 1.35. In such a lens, the transfer surface depth of the core portion in the first mold is increased, so that the surface area is increased, so that the lens easily adheres to the mold surface. By removing the optical element from the core part by holding the part other than the optical element in a state where the substantial release has been achieved, it is possible to reliably prevent mold release deformation and the like.

  In still another aspect of the invention, the absolute value of the radius of curvature of the first optical surface is smaller than the absolute value of the radius of curvature of the second optical surface. In this case, the core part and the optical element are easily brought into close contact with each other in the first mold. However, by achieving substantial release between the core part and the optical element in advance, it is possible to reliably prevent mold release deformation and the like. .

  In still another aspect of the present invention, the optical element is a lens having an optical function part having a first optical surface and a second optical surface, and a flange part arranged around the optical function part, and a core part Thereby, the 1st flange surface provided in the 1st optical surface side among flange parts is formed.

  In still another aspect of the present invention, the optical element is a lens having an optical function part having a first optical surface and a second optical surface, and a flange part arranged around the optical function part, and a core part Thus, an annular recess is formed between the first optical surface of the optical function unit and the first flange surface provided on the first optical surface side of the flange portion. In this case, when the optical element contracts by cooling in the first mold, the core part bites into the core part and becomes easy to adhere. However, before the optical element is taken out, the substantial release between the core part and the optical element is performed in advance. By achieving this, it is possible to reliably prevent mold release deformation and the like.

  While maintaining a state in which a part of the optical element is in contact with the holding part, the core part is moved to the second mold side, and the optical element is protruded to the second mold side. In this case, when the optical element is held by the holding unit, it is not necessary to move the holding unit, so that the holding of the optical element by the holding unit and the movement of the optical element by the core unit can be performed smoothly.

These are side sectional drawings explaining the shaping die for enforcing the manufacturing method of the optical element concerning a 1st embodiment. (A) is a figure explaining the type | mold space for shape | molding an optical element, (B) is a side view of the lens which is an optical element. It is a flowchart explaining the shaping | molding method using the shaping die shown in FIG. (A)-(F) are the conceptual diagrams which shape | mold the manufacturing process of an optical element. It is a graph explaining the movement of the core part at the time of manufacture. It is a figure explaining the type | mold space and optical element which are used with the manufacturing method of the optical element which concerns on 2nd Embodiment.

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

  As shown in FIG. 1, an injection molding apparatus 500 for carrying out the manufacturing method of the present embodiment includes a molding die 40, and the molding die 40 includes a first die 41 and a second die 42. Prepare. Here, the 1st metal mold | die 41 is driven by the opening / closing drive device 69, and can be reciprocated to AB direction. The first mold 41 is moved toward the second mold 42, the molds 41 and 42 are matched with each other on the parting surfaces PS1 and PS2, and the mold is clamped. As shown in an enlarged manner, a mold space CV for molding a lens as an optical element and a flow path space FC for supplying resin to the mold space CV are formed.

  As shown in FIG. 2A, the mold space CV includes the main body space CV1 sandwiched between the first and second transfer surfaces S1 and S2, and the third, fourth, and fifth transfer surfaces S3, S4, and S5. And a flange space CV2 surrounded by. Here, the pair of opposing first and second transfer surfaces S1 and S2 facing the main body space CV1 are the first and second of the central optical function part OP in the lens LP shown in an enlarged view in FIG. This is a portion for forming the optical surfaces OS1 and OS2. In this case, one first transfer surface S1 is deeper and has a larger curvature than the other second transfer surface S2. On the other hand, the third, fourth, and fifth transfer surfaces S3, S4, and S5 surrounding the flange space CV2 are portions for forming a flange portion FL disposed around the optical function portion OP in the lens LP. . Here, the pair of opposed third and fourth transfer surfaces S3 and S4 facing the flange space CV2 form the first and second flange surfaces FS1 and FS2 of the lens LP shown in an enlarged view in FIG. It is a part to do. The first flange surface FS1 provided on the first optical surface OS1 side of the flange portion FL is formed by an end surface of a core portion 64a of the first mold 41 described later. The fifth transfer surface S5 facing the flange space CV2 is a portion for forming the outer peripheral side surface SS of the lens LP. The flow path space FC has a runner portion RS as a space for forming the runner portion RP in the molded product 100 shown in FIG. The runner portion RS communicates with the mold space CV through the gate portion GS. The space of the gate part GS forms a gate part GP that connects the lens LP and the runner part RP in the molded product 100.

In the molded product 100 shown in FIG. 2B, the lens LP as a main body is a thick-type objective lens for an optical pickup having a large protrusion on the first optical surface OS1 side. Specifically, the lens LP enables reading or writing of optical information corresponding to a BD (Blu-ray Disc) having a wavelength of 405 nm and NA of 0.85, for example. Here, the optical specification of the lens LP is not limited to NA 0.85, but can correspond to various objective lens standards for optical pickup devices from NA 0.75 to NA 0.90, for example. . In this case, one first optical surface OS1 is disposed on the laser light source side, protrudes larger than the other second optical surface OS2 disposed on the optical disc OD side which is an optical information recording medium, and has a large curvature. It has become. That is, the absolute value of the radius of curvature of the first optical surface OS1 is smaller than the absolute value of the radius of curvature of the second optical surface OS2. Furthermore, since the absolute value of the radius of curvature of the first optical surface OS1 is extremely small, the lens LP has a very large thickness at the center. When such a shape is specified numerically, when the thickness of the lens LP on the optical axis OA is d (mm) and the focal length of the lens LP in a light beam having a wavelength of 500 nm or less is f (mm), Conditional expression (1)
0.9 ≦ d / f ≦ 3.0 (1)
Is satisfied. In such a case, the lens LP tends to stick to the first transfer surface S1, and it is not easy to release the lens LP from the first mold 41. When the value d / f is less than 0.9, the lens becomes a relatively flat lens and can be easily released without performing the steps described below. Further, when the value d / f exceeds 3.0, the lens becomes extremely long in the axial direction, so that further contrivance regarding mold release is required.

When the lens LP having a very large thickness at the center as described above is numerically expressed by another method, the depth on the optical axis OA of the first optical surface OS1 of the lens LP is expressed as S (mm), When the surface diameter in the direction perpendicular to the optical axis OA is R (mm), the following conditional expression (2)
0.75 ≦ S / R ≦ 1.35 (2)
Is satisfied. A lens LP that satisfies the conditional expression (2) is also likely to stick to the first transfer surface S1 similarly to the lens LP that satisfies the conditional expression (1), and it is not easy to release the lens LP from the first mold 41. Therefore, a device for making it easy to release the lens LP is required. When the value S / R is less than 0.75, the depth of the first optical surface OS1 becomes shallow, and the contact area between the first transfer surface S1 on the core side and the first optical surface OS1 on the lens side decreases. Mold release is facilitated without particularly performing the steps described below. Further, when the value S / R exceeds 1.35, the first transfer surface S1 becomes extremely long in the axial direction, so that further contrivance regarding mold release is required.

  Returning to FIG. 1, the first mold 41 on the movable side includes a core part 64 a as a central part that forms the mold space CV shown in FIG. 2A from the movable side, and a periphery provided around the core part 64 a. A holding part 64b as a part, a receiving plate 64c that supports the core part 64a and the holding part 64b from behind, a protruding member 64p for protruding and releasing the runner part RP of the molded product 100, a core part 64a, Movable rods 65, 66 that push the projecting member 64p from behind, and an advance / retreat mechanism 68 that moves the movable rods 65, 66 forward and backward in the axis AX direction are provided.

  The core part 64a is incorporated in a through hole 64g formed in the holding part 64b so as to be movable back and forth along the axis AX direction. The protruding member 64p is also incorporated in the through hole 64h formed in the holding portion 64b so as to be movable back and forth along the axis AX direction. Here, the core part 64a is urged rearward by a spring 64s with a certain force or more. That is, the core portion 64a is driven by the moving movable rod 65 to move forward to the second mold 42 side, and automatically retracts and returns to its original position according to the spring 64s that expands as the movable rod 65 moves backward. To do. The projecting member 64p is driven by the movable rod 66 to advance to the second mold 42 side, and retracts when an external force is applied by a holding part 74b on the second mold 42 side described later when the mold is closed. To return to the original position. In addition, the end surface 64e of the holding portion 64b is formed with a recess to be the runner portion RS shown in FIG.

  The second mold 42 on the fixed side includes a core part 74a as a central part that forms the mold space CV shown in FIG. 2A from the fixed side, and a holding part 74b as a peripheral part provided around the core part 74a. And a receiving plate 74c that supports the core portion 74a and the holding portion 74b from behind. Here, the core portion 74a is incorporated and fixed in a through hole 74g formed in the holding portion 74b. In addition, the end surface 74e of the holding portion 74b is formed with a recess to be the runner portion RS shown in FIG.

  FIG. 3 is a flowchart conceptually illustrating a method for manufacturing an optical element using the molding die 40 shown in FIG.

  First, the opening / closing drive device 69 is operated to start the mold closing by relatively moving the first mold 41 toward the second mold 42 (step S11). Note that the surfaces of both molds 41 and 42 are heated to a temperature suitable for molding.

  By continuing the closing operation of the opening / closing drive device 69, the first mold 41 and the second mold 42 are moved to the mold contact position where they are in contact with each other, the mold closing is completed, and the opening / closing drive device 69 is further closed. By continuing, the mold clamping which clamps the 1st metal mold | die 41 and the 2nd metal mold | die 42 with required pressure is performed (step S12).

  Next, an injection device (not shown) is operated to inject the molten resin into the mold space CV between the clamped first mold 41 and the second mold 42 at a necessary pressure. (Step S13). The injection device maintains the resin pressure in the mold space CV.

  After the molten resin is introduced into the mold space CV, the molten resin in the mold space CV is gradually cooled by heat dissipation, so that the molten resin is solidified with the cooling and waits for completion of molding (step S14). .

  Next, the opening / closing drive device 69 is operated to perform mold opening for moving the first mold 41 relatively backward from the second mold 42 (step S15). As the first mold 41 moves backward, the first mold 41 and the second mold 42 are separated from each other. As a result, as shown in FIG. 4A, the molded product 100, that is, the lens LP remains on the first mold 41 side. That is, the lens LP is released from the second mold 42 while being held so as to be embedded in the first mold 41.

  Next, the advance / retreat mechanism 68 is operated, and the first protrusion is performed on the molded product 100 remaining on the first mold 41 side by the movable rods 65 and 66 (step S16). Thereby, as shown in FIG.4 (B), the partial release of the molded article 100 is performed. At this time, the gate portion GP and the runner portion RP are pushed out by the projecting member 64p and separated from the end face 64e of the holding portion 64b, but the lens LP protrudes although it slightly moves to the right side of the drawing, that is, the second mold 42 side. Is supported at the tip of the core portion 64a and the like. That is, since the first transfer surface S1 of the core portion 64a is deep, the first optical surface OS1 of the lens LP is in close contact with the first transfer surface S1, and the lens LP is adsorbed and supported at the tip of the core portion 64a. It becomes. Further, by reducing the movement amount s1 of the core portion 64a by the first protrusion less than the thickness t of the flange portion FL of the lens LP, the state in which the flange portion FL is partially fitted to the holding portion 64b is maintained. The That is, the outer peripheral side surface SS of the flange portion FL and the fifth transfer surface S5 of the holding portion 64b are in close contact with each other while being displaced in the axis AX direction.

  Next, the advancing / retreating mechanism 68 is operated to retract the movable rod 65 toward the first mold 41 and retract the core 64a to the original position, thereby performing the first protrusion back (step S17). ). At this time, as shown in FIG. 4C, the lens LP is separated from the tip of the core portion 64a because the flange portion FL is supported by the holding portion 64b to prevent the lens LP from moving backward. That is, the outer peripheral side surface SS of the flange portion FL and the transfer surface S5 provided on the inner periphery of the holding portion 64b are in close contact with each other, and the friction force acting between them wins and the lens LP is locked to the holding portion 64b. On the other hand, the first transfer surface S1 of the core portion 64a and the first optical surface OS1 of the lens LP are separated from each other to eliminate the close contact, so that the lens LP is separated from the core portion 64a.

  Next, the advancing / retreating mechanism 68 is operated, and the second protrusion is performed on the molded product 100 remaining on the first mold 41 side by the movable rod 65 (step S18). In this case, as shown in FIG. 4D, the lens LP is largely moved to the right side of the drawing, that is, the second mold 42 side by the advancement of the core portion 64a, so that the lens LP is completely pushed out from the holding portion 64b. Thus, substantial release of the molded product 100 is achieved. In order to achieve such substantial mold release, the movement amount s2 of the core portion 64a due to the second protrusion is larger than the thickness t of the flange portion FL of the lens LP. At this time, since the close contact between the first transfer surface S1 of the core portion 64a and the first optical surface OS1 of the lens LP has already been eliminated, the lens LP is merely in light contact with the core portion 64a. .

  In this state, a take-out device (not shown) is operated to separate the molded product 100 from the first mold 41 and carry it out to the outside as shown in FIG. 4E (step S19). When the molded product 100 is conveyed, the portion of the molded product 100 excluding the lens LP is gripped. Since the substantial release of the molded product 100 from the first mold 41 has been achieved before this unloading step, it is possible to prevent a biased force from being applied to a part of the outer periphery of the lens LP. When substantial release of the molded product 100 has not been achieved, when the runner portion RP or the like is pulled by the hand of the take-out device, the thin gate portion GP is bent and the release deformation extends to the first optical surface OS1. Is likely to occur.

  Finally, the advance / retreat mechanism 68 is operated to move the movable rod 65 back toward the first mold 41 again, thereby retracting the core 64a to the original position as shown in FIG. The second ejection is performed (step S20). After that, the process returns to step S11 to start mold closing, so that a large number of molded articles 100 can be continuously molded.

  FIG. 5 is a graph summarizing the axial movement of the core portion 64a until a single molded article 100 is obtained. The period P1 before the first protrusion corresponds to mold closing (step S11), mold clamping (step S12), resin injection (step S13), cooling (step S14), and mold opening (step S15). In the period P2 of the first projecting process, the amount of movement s1 of the core portion 64a is less than the thickness t of the flange portion FL, so that the flange portion FL is partially fitted with the holding portion 64b. It can be. By appropriately setting the return force and return speed of the movable rod 65 in the period P3 of the next first projecting return process, the lens LP can be removed from the core portion 64a without difficulty. In the period P4 of the next second protrusion process, the flange portion FL is substantially pushed out of the holding portion 64b by making the movement amount s2 of the core portion 64a larger than the thickness t of the flange portion FL. It is possible to achieve a release state. In the next holding state period P5, the molded product 100 can be carried out to the outside without being forcibly removed. In the period P6 of the last second protrusion return process, the core portion 64a is returned to the original position.

Here, the movement amounts s1 and s2 in the projecting process of the core portion 64a will be considered. As for the movement amount s1 at the time of the first protrusion, the following range is usually set based on the thickness t of the flange portion FL: 0.1 mm ≦ s1 ≦ t−0.1 mm (3)
And More preferably, the following range 0.5t−0.2 mm ≦ s1 ≦ 0.5t + 0.2 mm (3 ′)
And In addition, by making s1 0.1 mm or more, the stroke amount of the core part 64a in the first protrusion return process can be secured, and the certainty of peeling the lens LP from the core part 64a can be improved. . Further, by setting s1 to t−0.1 mm or less, it is possible to increase the holding power of the lens LP by the holding portion 64b in the first protrusion return process, and it is possible to reliably remove the lens LP from the core portion 64a. Can be increased.

On the other hand, the movement amount s2 at the time of the second protrusion is usually in the following range t <s2 (4).
And More preferably, the following range t + 0.2 mm ≦ s2 ≦ t + 0.6 mm (4 ′)
And

  In a specific example, the thickness t of the flange portion FL was 0.6 mm, the first movement amount s1 was 0.3 mm, and the second movement amount s2 was 1.0 mm. In this case, the lens LP could be reliably peeled off from the core portion 64a in the first protruding back step, and the molded product 100 could be smoothly carried out of the mold.

  Here, the advance / retreat speed of the core portion 64a will be described. From the viewpoint of achieving reliable release of the lens LP, the control of the protruding speed V1 of the core portion 64a in the first and second protruding steps and the return speed V2 of the core portion 64a in the first protruding return step. This is an important factor. In general, it is desirable that | V1 |> | V2 |. This is because if | V2 | is large, the lens LP does not stop in the holding state when returning, and comes to the core portion 64a.

Here, the return force of the core part 64a will be described. From the viewpoint of achieving reliable mold release of the lens LP, control of the return force of the core portion 64a is an important factor. In the first projecting and returning process, the force (sticking force) that the core portion 64a pulls the lens LP is F0, the force that the lens LP pulls the core portion 64a (sticking force) is F0 ′, and the holding portion 64b and the lens LP F1 = F0 ′ by the law of action and reaction, and the following condition | F2 |> | F0 ′ |
| F1 | >> | F0 |
Need to be met. First, unless | F2 |> | F0 ′ |, the core portion 64a cannot be returned, and as a result, it becomes impossible to avoid a mold release failure. If | F1 |> | F0 | is not satisfied, the lens LP returns together with the core portion 64a, and as a result, it becomes impossible to avoid a mold release failure. The frictional force F1 is determined by the protruding movement amount s2 of the core portion 64a, the thickness t of the flange portion FL, the friction coefficient between the holding portion 64b and the lens LP, and the return force F2 is the first time. The amount of protrusion s1 is determined by the spring constant of the spring 64s.

  According to the optical element manufacturing method of the present embodiment described above, the core portion 64a is moved to the first mold 41 side while keeping the flange portion FL, which is a part of the lens LP, in contact with the holding portion 64b. A step of separating the core portion 64a from the first optical surface OS1 of the lens LP, and a step of moving the core portion 64a again to the second mold 42 side to separate the lens LP from the holding portion 64b. The lens LP can be removed from the core portion 64a by holding the runner portion RP other than the lens LP in a state where the substantial release between the core portion 64a and the lens LP is achieved. Thereby, deformation and scratches of the optical surfaces OS1, OS2, etc. when the molded product 100 is taken out can be reduced, and a high-quality lens LP can be provided.

[Second Embodiment]
Hereinafter, a method for manufacturing an optical element according to the second embodiment will be described. Note that the optical element 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.

  As shown in FIG. 6, the end surface of the core portion 164a is provided with a transfer surface S8 for forming the surface of the annular recess RE at the boundary between the flange portion FL and the optical function portion OP. A third transfer surface S3 for forming the first flange surface FS1 of the flange portion FL is provided on the end surface of 64b.

  In the case of the second embodiment, since the transfer surface S8 of the core portion 164a is deeply fitted into the lens LP, the lens LP is likely to be in close contact with the core portion 164a. Thus, the lens LP can be reliably released from the core portion 164a and taken out of the mold, so that deformation and scratches of the optical surfaces OS1, OS2, etc. when the molded product 100 is taken out can be reduced, and the high-quality lens LP Can be provided.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment. For example, the first mold 41 can be fixed and the second mold 42 can be moved.

  Moreover, it is not necessary to arrange | position the 1st metal mold | die 41 and the 2nd metal mold | die 42 horizontally, and it can also be set as the vertical molding metal mold | die which arrange | positions the 1st metal mold | die 41 and the 2nd metal mold | die 42 up and down. it can.

  In the above embodiment, the molded product 100 is separated from the first mold 41 and carried outside in step S19, and the core portion 64a is returned to the original position in step S20. However, this order can be changed. . That is, before the molded product 100 is carried outside, the core part 64a is returned to the original position while the take-out device holds the proper position of the molded product 100, and then the molded product 100 is removed from the first mold 41. It can also be removed and carried outside.

  In the above embodiment, the lens LP is an objective lens for an optical pickup device. However, a small lens having a similar shape and a large central wall thickness can be manufactured by the same method as in this embodiment. Surface deformation and scratches can be reduced, and it is possible to cope with a case where required accuracy is high.

  In the above embodiment, the return force of the core portion 64a is given by the spring, but the core portion 64a can be returned by means other than the spring.

  In the above embodiment, the outer peripheral side surface SS of the lens LP is a cylindrical surface. However, the outer peripheral side surface SS may not have a shape symmetrical to the optical axis OA. That is, the outer peripheral side surface SS may be a substantially prismatic surface, or a surface obtained by combining a cylindrical surface and a prismatic surface. Further, a slight taper can be formed on the outer peripheral side surface SS, and a slight taper can also be formed on the fifth transfer surface S5 of the holding portion 64b.

  In the above embodiment, the optical surface of the lens LP is not limited to a smooth one, and the optical surface may have a fine diffractive shape.

Claims (10)

A method of manufacturing an optical element with a runner using an injection molding device,
The injection molding apparatus includes a first mold that molds a first optical surface of an optical element, and a second mold that molds a second optical surface of the optical element, and the first mold Has a core part and a holding part for holding the core part,
Injecting molten resin into a cavity formed by the first mold and the second mold, and molding the optical element;
Opening the mold by relatively moving the first mold and the second mold so as to leave the optical element in the first mold;
Moving the core part to the second mold side and projecting the optical element to the second mold side;
A step of moving the core part to the first mold side while keeping a part of the optical element in contact with the holding part to separate the core part from the first optical surface of the optical element. When,
Moving the core part again to the second mold side, projecting the optical element again to the second mold side, and separating the optical element from the holding part;
Holding the part other than the optical element, and removing the optical element from the core part.   The method of manufacturing an optical element according to claim 1, wherein the optical element is an optical element for an optical pickup device that records and / or reproduces information on an optical information recording medium.   The method of manufacturing an optical element according to claim 2, wherein the optical element is used for an objective lens of the optical pickup device.   4. The relationship according to claim 3, wherein NA is 0.75 ≦ NA ≦ 0.90, where NA is a numerical aperture of the optical element necessary for recording and / or reproducing information with respect to the optical information recording medium. Of manufacturing the optical element.   When the thickness on the optical axis of the lens as the optical element is d (mm) and the focal length of the lens in a light beam having a wavelength of 500 nm or less is f (mm), 0.9 ≦ d / f ≦ 3. The method for producing an optical element according to claim 1, wherein the optical element is zero.   When the depth of the first optical surface of the lens as the optical element is S (mm) and the surface diameter of the first optical surface is R (mm), 0.75 ≦ S / R ≦ 1.35. The manufacturing method of the optical element of Claim 1 which exists.   2. The method of manufacturing an optical element according to claim 1, wherein an absolute value of a radius of curvature of the first optical surface is smaller than an absolute value of the radius of curvature of the second optical surface. The optical element is a lens having an optical function part having the first optical surface and the second optical surface, and a flange part arranged around the optical function part,
The method of manufacturing an optical element according to claim 1, wherein a first flange surface provided on the first optical surface side of the flange portion is formed by the core portion. The optical element is a lens having an optical function part having the first optical surface and the second optical surface, and a flange part arranged around the optical function part,
The annular recess is formed between the first optical surface of the optical function unit and a first flange surface provided on the first optical surface side of the flange portion by the core portion. The manufacturing method of the optical element of description.   The core part is moved to the second mold side while keeping a part of the optical element in contact with the holding part, and the optical element is projected to the second mold side. 2. A method for producing an optical element according to 1.

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