JP2008229889A - Injection mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold an optical element having a desired shape by preventing a fine flaw from being produced in an optical function surface. <P>SOLUTION: The movable mold 4 of this injection mold 2 for injection-molding the optical element 10 has a mold main body 42 and the ejection mold 41 arranged in the hole part 42b in a slidable state. The ejection mold 41 has a central molding surface 41b for forming the optical function surface 12a and an outer peripheral molding surface 41c for forming an outer peripheral surface. The central molding surface 41b has a plurality of diffraction patterns DP and the pitch of the diffraction pattern DP of at least the outermost periphery is 10 μm or below. The outer peripheral molding surface 41c has an annular protruded part 41d protruded so as to surround the central molding surface 41b. An annular taper surface 41e becoming small in its outer diameter as approaching a fixed mold 3 is formed to the outer peripheral surface of the leading end part of the annular protruded part 41d and the angle of the annular taper surface 41e with respect to the approaching and separating direction of the fixed mold 3 and the movable mold 4 is 15-45° and the width thereof is 0.05-2 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection mold for forming an optical element.

  2. Description of the Related Art Conventionally, an optical element such as an objective lens has a flange on the outer peripheral side of an optical functional surface provided with a fine diffractive structure, and is gripped by this flange.

  As shown in FIG. 4, an injection mold for injection molding such an optical element has a fixed mold 101 and a movable mold 102 that can be moved toward and away from the fixed mold 101 in the X direction. The fixed mold 101 and the movable mold 102 come into contact with each other to form a gate 103 or the like as a flow path for the plastic material and a cavity 104 for molding the plastic material.

  More specifically, the movable mold 102 is fitted into the mold main body 121 so as to be slidable in the X direction, and forms a central side part of the cavity 104 while forming the outer peripheral side portion of the cavity 104. And a protruding mold 122.

  Among these, the mold body 121 is provided with a hole 121b that penetrates in the X direction and accommodates the protruding mold 122, and a molding surface 121a that surrounds the hole 121b. An outer peripheral side portion of the flange 201 in the optical element 200 is formed.

  On the other hand, the protruding mold 122 is provided with a molding surface 122a facing the fixed mold 101. The molding surface 122a is formed by the center-side molding surface 122b and the optical functional surface 200b of the optical element 200 by the outer peripheral-side molding surface 122c. The inner peripheral side portion of the flange 201 in the optical element 200 is formed respectively.

  Here, the center side molding surface 122b is provided with a fine ring-shaped diffraction pattern DP for forming a ring zone step on the optical functional surface 200b, and the outer circumferential side molding surface 122c has an annular protrusion 122d. Is provided so as to surround the center side molding surface 122b. In addition, the outer peripheral surface of the tip of the annular protrusion 122d is parallel to the X direction, or has a tapered shape whose outer shape becomes smaller as it approaches the fixed mold 101 (see, for example, Patent Document 1). In addition, the angle with respect to the X direction of this taper surface is 25 degrees or less.

When the optical element 200 is molded using such an injection mold 100, first, as shown in FIG. 4 (a), a molten plastic material is injected from the gate 103 into the cavity 104 and is subjected to pressure molding. When the plastic material is solidified and the optical element 200 is formed, the movable mold 102 is separated from the fixed mold 101 to leave the optical element 200 on the movable mold 102 side as shown in FIG. Then, after the protruding mold 122 is protruded from the mold main body 121 and the optical element 200 is pushed out from the mold main body 121, a stick-shaped plastic material portion (hereinafter referred to as a pulling portion) 200a solidified in the gate 103 is pulled to protrude the protruding mold. The optical element 200 is released from 122. Thereby, the molding of the optical element 200 is completed.
JP-A-2005-132002

  However, when the optical element 200 is molded by the injection mold described in Patent Document 1, when the optical element 200 is released from the protruding mold 122 by pulling the pulling portion 200a as shown in FIG. Since a large mold release resistance is generated by being caught by the portion 122d, the optical element 200 is released from the projecting mold 122 at a time when the pulling force by the pulling section 200a becomes larger than the mold release resistance. An annular step formed on the optical functional surface 200b is destroyed by the diffraction pattern DP. In particular, when the pitch of the diffraction pattern DP on the outer peripheral side is 10 μm or less, this problem becomes more prominent.

  On the other hand, as a method for solving such a problem, it is conceivable to provide the outer peripheral surface of the tip of the annular protrusion 122d in a tapered shape and increase the angle of the tapered surface with respect to the X direction. If the optical element 200 is excessively contracted in the X direction and a gap is formed between the center-side molding surface 122b and the optical function surface 200b of the optical element 200, the portion of the optical function surface 200b is in the X direction. When the optical element 200 is pushed out from the die body 121 by the protruding die 122, the thermal contraction is also caused in the orthogonal direction, so that the positional relationship between the annular step of the optical function surface 200b and the diffraction pattern DP of the central molding surface 122b is shifted. In addition, the optical functional surface 200b is slightly scratched by the diffraction pattern DP (see Patent Document 1).

  The subject of this invention is providing the injection mold which can shape | mold the optical element of a desired shape.

The invention according to claim 1 is an injection mold for injection molding an optical element,
A fixed mold that forms one surface of the optical element;
A movable mold provided so as to be able to contact and separate from the fixed mold and forming the other surface of the optical element;
The movable type is
A mold body having a hole,
A protruding mold disposed in the hole in a slidable state with respect to the mold body,
The protruding mold is
A central molding surface forming an optical functional surface in the other surface;
An outer peripheral side molding surface that forms an outer peripheral side surface from the optical function surface, and
The central molding surface is
Having a plurality of ring-shaped diffraction patterns forming a ring-shaped step in the optical function surface;
Among these diffraction patterns, the pitch of at least the outermost diffraction pattern is 10 μm or less,
The outer peripheral side molding surface is
Having an annular protrusion protruding around the central molding surface;
On the outer peripheral surface of the tip of this annular protrusion,
An annular tapered surface having a smaller outer diameter as it approaches the fixed mold is formed,
This annular taper surface
The angle between the fixed mold and the movable mold with respect to the contact / separation direction is 15 to 45 °, and the width is 0.05 to 2 mm.

The invention described in claim 2 is the injection mold according to claim 1,
The hole is provided through the mold body,
The annular protrusion is provided on an outer peripheral edge of the protruding mold,
The movable mold is formed by inserting the protruding mold into the hole toward the fixed mold side.

The invention according to claim 3 is the injection mold according to claim 1 or 2,
The annular protrusion may form a base of a flange of the optical element.

  According to the first aspect of the present invention, the outer peripheral side molding surface has the annular projecting portion that projects around the central side molding surface, and the outer peripheral surface of the tip end portion of the annular projecting portion is outer as approaching the fixed mold. An annular tapered surface having a reduced diameter is formed, and this annular tapered surface has an angle with respect to the contact and separation direction of the fixed mold and the movable mold of 15 to 45 ° and a width of 0.05 to 2 mm. Of the plurality of ring-shaped diffraction patterns provided on the center-side molding surface, the outermost diffraction pattern has a pitch of 10 μm or less, and one end of the optical element is pulled to release the optical element from the protruding mold. At this time, the mold release resistance due to the surface on the outer peripheral side of the optical function surface being caught by the annular projecting portion becomes smaller than that of the conventional one. Accordingly, since the optical element can be gradually released from the protruding mold, it is possible to prevent the annular step formed on the other optical functional surface of the optical element from being destroyed by the diffraction pattern.

In addition, since the angle of the annular tapered surface with respect to the contact / separation direction of the fixed mold and the movable mold is 15 to 45 °, the optical element is thermally contracted in the contact / separation direction, and the center side molding surface and the optical surface in the other surface Even in the case where a gap is generated between the functional surface, the annular functional surface prevents the portion of the optical functional surface from being thermally contracted in a direction perpendicular to the contact / separation direction. Therefore, when the optical element is pushed out from the mold body by the protruding mold, it is possible to prevent the optical functional surface from being damaged by the diffraction pattern.
Therefore, an optical element having a desired shape can be formed.

  According to the second aspect of the present invention, the hole is provided penetrating the mold body, the annular protrusion is provided at the outer peripheral edge of the protruding mold, and the movable mold has the protruding mold in the hole toward the fixed mold side. Because it is formed by insertion, it prevents the base of the annular taper surface and the inner peripheral surface of the hole from being scratched when a protruding mold is inserted into the hole of the mold body to form a movable mold. can do. Therefore, an optical element having a desired shape can be molded more reliably.

  According to the invention described in claim 3, the same effect as that of the invention described in claim 1 or 2 can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
First, a molding machine provided with an injection mold according to the present invention will be described.
FIG. 1 is a conceptual diagram showing a schematic configuration of a molding machine 1 for injection molding an optical element.

  As shown in this figure, the molding machine 1 includes a hopper 51, a cylinder 53, a nozzle 55, an injection mold 2 and the like according to the present invention from the upstream side to the downstream side in the conveying direction of the plastic material. I have.

  The hopper 51 is a portion to which a plastic material is supplied, and is connected to the cylinder 53. The cylinder 53 includes a screw 52 inside, and is connected to a nozzle 55 at the tip, and pushes the plastic material supplied from the hopper 51 toward the nozzle 55 by the screw 52. A heater 54 for melting the plastic material inside the cylinder 53 is provided on the side surface of the cylinder 53.

  The nozzle 55 is a portion that injects the plastic material extruded from the cylinder 53 into the injection mold 2 and communicates with a sprue 21 of the injection mold 2 described later.

  The injection mold 2 includes a fixed mold 3 fixed to the nozzle 55 and a movable mold 4 provided so as to be movable toward and away from the fixed mold 3 in the X direction. When the movable mold 4 abuts, a sprue 21, a runner 22 and a gate 23 as flow paths for the plastic material and a cavity 24 for molding the plastic material are formed.

  As shown in FIG. 2, the fixed mold 3 forms one surface 11 of the optical element 10, and includes a first member 31 that forms a central portion of the cavity 24 and a second member that forms an outer peripheral portion. Member 32.

  The first member 31 is provided with a molding surface 31a facing the movable mold 4, and the molding surface 31a forms an optical functional surface 11a in one surface 11 of the optical element 10. . The molding surface 31a may be provided with a fine ring-shaped diffraction pattern.

  On the other hand, the second member 32 is provided with an annular molding surface 32a surrounding the molding surface 31a, and the flange 15 is formed on the outer peripheral portion of the optical element 10 by the molding surface 32a.

  The first member 31 and the second member 32 described above are both formed of a single steel material and are integrally fixed to each other.

  The movable die 4 forms the other surface 12 of the optical element 10 and includes a die body 42 that forms the outer peripheral side portion of the cavity 24 and a protruding die 41 that forms the central side portion. Yes.

  The mold body 42 is provided with a hole portion 42b penetrating in the X direction and a molding surface 42a surrounding the hole portion 42b. The flange 15 is formed on the outer peripheral portion of the optical element 10 by the molding surface 42a. It is supposed to do.

  As shown in FIG. 3, the protruding die 41 is slidable in the X direction in a state of being fitted in the hole 42b. As shown in FIG. It is connected to a projecting member 43 to be slid.

  Further, as shown in FIG. 2, the protruding die 41 is provided with a molding surface 41 a facing the fixed die 3, and this molding surface 41 a is an optical functional surface in the other surface 12 of the optical element 10. It has a central molding surface 41b that forms 12a and an outer circumferential molding surface 41c that forms the base of the flange 15 on the outer circumferential side of the optical function surface 12a.

  The center-side molding surface 41b has a fine annular zone-shaped diffraction pattern DP that forms an annular zone step on the optical function surface 12a. The diffraction pattern DP has at least the outermost peripheral pitch P of 10 μm or less and a depth of about several μm. In addition, when the center side molding surface 41b is formed in a concave shape as a whole, the outermost peripheral pitch P of the diffraction pattern DP is the case where each diffraction pattern DP is projected onto a surface orthogonal to the X direction. Say the pitch.

The outer peripheral side molding surface 41c has an annular projecting portion 41d that projects around the central side molding surface 41b. The annular projecting portion 41d provides a difference in height between the optical functional surface 12a of the optical element 10 and the flange 15. When the manufactured optical element 10 is placed and transported due to the difference in height, the annular protrusion 41d is optical. The functional surface 12a is prevented from being damaged.
An annular tapered surface 41e having an outer diameter that decreases as it approaches the fixed mold 3 is formed on the outer peripheral surface of the tip of the annular projecting portion 41d. The annular tapered surface 41e is located on the outer peripheral edge of the protruding die 41, and has an angle θ with respect to the X direction of 15 to 45 ° and a width L of 0.05 to 2 mm.

  The movable mold 4 described above is formed by inserting a protruding mold 41 into the hole 42b toward the fixed mold 3 side. In this insertion, an annular tapered surface 41e is provided on the outer peripheral edge of the protruding die 41, and the annular tapered surface 41e has an angle θ of 15 to 45 ° with respect to the X direction (the sliding direction of the protruding die 41 with respect to the die body 42). Since the width L is 0.05 to 2 mm, the corner portion of the protruding die 41, that is, the base portion of the annular tapered surface 41e and the inner peripheral surface of the hole portion 42b are prevented from being damaged.

  Next, a method for molding the optical element 10 using the molding machine 1 will be described. In addition, as the optical element 10 shape | molded with this molding machine 1, the thing of the use for which transparency is requested | required is preferable.

  First, a plastic material is put into the hopper 51 and melted by the heater 54 while being conveyed in the direction of the nozzle 55 by the screw 52.

  Next, as shown in FIG. 3A, the melted plastic material is injected from the nozzle 55 and the sprue 21 into the runner 22, the gate 23, and the cavity 24 of the injection mold 2, and is pressure-molded. As a result, the plastic material in the cavity 24 is solidified to form the optical element 10, and the plastic material in the gate 23 is solidified to provide the rod-shaped pulling portion 10 d integrally with the optical element 10.

  Next, as shown in FIG. 3B, the movable die 4 is separated from the fixed die 3 to leave the optical element 10 on the movable die 4 side, and then the protruding die 41 is protruded from the die main body 42 by the protruding member 43. Then, the optical element 10 is pushed out from the mold main body 42. At this time, since the angle of the annular tapered surface 41e with respect to the X direction is 15 to 45 °, the optical element 10 is thermally contracted in the X direction, and a gap is generated between the central molding surface 41b and the optical function surface 12a. Even in this case, the annular tapered surface 41e prevents the portion of the optical function surface 12a from being thermally contracted in the direction orthogonal to the X direction. Therefore, the optical element 10 is pushed out from the mold body 42 by the protruding mold 41 in a state where the annular step of the optical function surface 12a and the position of the diffraction pattern DP of the center-side molding surface 41b coincide.

  Next, the optical element 10 is released from the protruding die 41 by pulling the pulling portion 10d. At this time, the angle θ with respect to the X direction of the annular tapered surface 41e (the sliding direction of the protruding die 41 with respect to the die main body 42) is 15 to 45 °, and the width L is 0.05 to 2 mm. Among the plurality of diffraction patterns DP provided on the center-side molding surface 41b, even when the pitch of the outermost diffraction pattern DP is 10 μm or less, the mold release resistance due to the base portion of the flange 15 being caught by the annular protrusion 41d is reduced. Smaller than before. Accordingly, the optical element 10 is gradually released from the protruding die 41.

  Then, by removing the pulling portion 10d from the optical element 10, the molding of the optical element is completed.

  According to the above injection mold 2, the optical element 10 can be gradually released from the protruding mold 41, so that when the optical element 10 is released from the protruding mold 41 by pulling the pulling portion 10 d, the optical function surface is provided. It is possible to prevent the annular zone step 12a from being destroyed by the diffraction pattern DP. In addition, since the optical element 10 can be pushed out from the die body 42 by the protruding die 41 in a state where the annular step of the optical functional surface 12a and the diffraction pattern DP of the center side molding surface 41b coincide with each other, the protruding die 41 When the optical element 10 is pushed out from the mold body 42, the optical functional surface 12a can be prevented from being damaged by the diffraction pattern DP. Therefore, an optical element having a desired shape can be molded.

  Further, when the protruding die 41 is inserted into the hole portion 42b of the die body 42 to form the movable die 4, the corner portion of the protruding die 41, that is, the base portion of the annular tapered surface 41e, and the inner peripheral surface of the hole portion 42b. It is possible to prevent the scratches on the base portion of the annular tapered surface and the inner peripheral surface of the hole from being transferred to the optical element. Therefore, an optical element having a desired shape can be molded more reliably.

  The embodiments to which the present invention can be applied are not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the annular projecting portion 41d has been described as forming the base portion of the flange 15, but it is also possible to form a portion on the outer peripheral side with respect to the base portion.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these.

(1) Preparation of Sample As shown in Table 1 below, as an example of the injection mold 2 and a comparative example, a material (1) in which the width L of the annular tapered surface 41e and the angle θ with respect to the X direction are changed. -(64) was created. Of these materials (1) to (64), materials (18) to (23), (26) to (31), (34) to (39), and (42) to (47) are examples of the present invention. Other than these are comparative examples. In any of the materials, the diffraction pattern DP is provided on the central molding surface 41b of the protruding die 41 at a pitch of 10 μm.

(2) Evaluation of molded optical element For each optical element molded by the injection molds of the above-mentioned materials (1) to (64), whether or not the annular zone step is deformed and the optical function surface 12a. It was observed whether or not minute scratches were attached.

  Further, in order to investigate the destruction state of the annular zone step, the astigmatism of each optical element was measured in the region on the pulling portion 10d side and the region on the opposite side, and the astigmatism variation σ was calculated.

  Then, based on the results of these observations and measurements, it was evaluated whether or not an optical element having a desired shape could be molded with the injection molds of materials (1) to (64). The evaluation results are shown in Table 1 above. However, in Table 1, the criteria of “◎”, “◯”, “×”, “●”, “▲” are as follows.

A: Deformation does not occur in the annular zone step, and the astigmatism variation σ is 0.0005 or less.
A: Deformation occurs in the annular zone step, but the astigmatism variation σ is 0.001 or less.
X: Astigmatism cannot be measured as a result of deformation of the annular zone step.
● Although the optical functional surface 12a is finely scratched, it is practically usable.
... Small scratches are attached to the optical function surface 12a, which is not practical.

  As shown in Table 1, materials (18) to (23), (26) to (26) having an angle θ with respect to the X direction of the annular tapered surface 41e of 15 to 45 ° and a width L of 0.05 to 2 mm. In 31), (34) to (39), and (42) to (47), it was found that an optical element having a desired shape can be formed, unlike materials other than these.

It is a conceptual diagram which shows schematic structure of a molding machine. It is sectional drawing of the injection mold which concerns on this invention. It is a figure explaining the method to shape | mold an optical element with the injection mold which concerns on this invention, (a) is a figure which shows the state before mold opening at the time of shaping | molding, (b) is a figure which shows the state which protruded the optical element It is. It is sectional drawing of the conventional injection molding die. It is a figure which shows the state which the diffraction structure of an optical element deform | transforms with the conventional injection molding die.

Explanation of symbols

2 Injection mold 3 Fixed mold 4 Movable mold 10 Optical element 11 One surface 12 The other surface 15 Flange 42 Mold body 41 Extrusion die 41b Center side molding surface 41c Outer peripheral side molding surface 41d Annular protrusion 41e Annular taper surface DP Diffraction pattern

Claims (3)

An injection mold for injection molding an optical element,
A fixed mold that forms one surface of the optical element;
A movable mold provided so as to be able to contact and separate from the fixed mold and forming the other surface of the optical element;
The movable type is
A mold body having a hole,
A protruding mold disposed in the hole in a slidable state with respect to the mold body,
The protruding mold is
A central molding surface forming an optical functional surface in the other surface;
An outer peripheral side molding surface that forms an outer peripheral side surface from the optical function surface, and
The central molding surface is
Having a plurality of ring-shaped diffraction patterns forming a ring-shaped step in the optical function surface;
Among these diffraction patterns, the pitch of at least the outermost diffraction pattern is 10 μm or less,
The outer peripheral side molding surface is
Having an annular protrusion protruding around the central molding surface;
On the outer peripheral surface of the tip of this annular protrusion,
An annular tapered surface having a smaller outer diameter as it approaches the fixed mold is formed,
This annular taper surface
An injection mold characterized in that an angle with respect to the contact / separation direction of the fixed mold and the movable mold is 15 to 45 ° and a width is 0.05 to 2 mm. The injection mold according to claim 1,
The hole is provided through the mold body,
The annular protrusion is provided on an outer peripheral edge of the protruding mold,
The movable mold is formed by inserting the protruding mold into the hole toward the fixed mold side. The injection mold according to claim 1 or 2,
The injection mold according to claim 1, wherein the annular protrusion forms a base of a flange of the optical element.

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