JP2008221613A - Method for producing lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly produce a lengthy optical lens by preventing deformation in the middle of the lens when the lens is released from a mold. <P>SOLUTION: The optical lens 17 which includes a lens part 17A having a cross-sectional shape in the longitudinal direction of a meniscus shape and a flange part 17B positioned outside the lens part 17A, wherein the maximum length A including the flange part 17B in the longitudinal direction and the maximum length B including the flange part 17B in the short hand direction meet the formula: 6≤A/B≤30, from the concave side of the cross-sectional shape in the longitudinal direction of the lens part 17A, is released from a mold by pushing the flange part 17B by a plurality of ejector pins 201. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lens manufacturing method for manufacturing an optical lens by filling a molten resin material into a mold.

  In recent years, plastic lenses (optical lenses) molded from resin materials are used in optical scanning devices used in laser beam printers, laser facsimiles, and the like. Since an image is written on the photosensitive drum or the like by the laser beam emitted by the optical scanning device, it is necessary to use a plastic lens manufactured with high accuracy in order to write a highly accurate image on the photosensitive drum or the like.

  In general, many plastic lenses used in optical scanning devices are long, and when a high-precision plastic lens is manufactured by molding, multiple ejectors are used to prevent the plastic lens from being deformed when released from the mold. It is necessary to release the plastic lens from the mold with a pin. Therefore, in order to secure a place where the plastic lens is pushed by a plurality of ejector pins, it is conceivable to provide a flange on the outer periphery of the plastic lens as described in Patent Document 1. Its specific configuration is shown in FIG.

  FIG. 7A is a plan view of the plastic lens, and FIG. 7B is a perspective view showing a part of the plastic lens.

  As shown in FIG. 7B, a lens portion 1001 having an optical function is provided at the center of the plastic lens 1000, and a collar portion 1002 is provided on the outer periphery of the lens portion 1001. Further, as shown in FIG. 7A, the cross-sectional shape in the longitudinal direction of the lens portion 1001 is a meniscus shape.

  FIG. 8 is a schematic view showing an example of a mold structure for molding a plastic lens.

  The outer shape of the plastic lens 1000 is basically formed by a mold 2000 and a mold 3000. The molding of the lens portion 1001 in the plastic lens 1000 will be described later. The molten resin material is filled in the cavity at a position where the mold 2000 and the mold 3000 are in contact, and when the filled resin material is cooled to some extent, the mold 2000 and the mold 3000 are separated from each other. Then, the plastic lens 1000 is released from the mold 3000 by pressing the collar portion 1002 of the plastic lens 1000 with a plurality of ejector pins 3001.

  FIG. 9 is a sectional view of a mold in the lens portion 1001 of the plastic lens 1000.

  As described with reference to FIG. 8, the outer shape of the plastic lens 1000 is formed by the mold 2000 and the mold 3000, but the lens portion 1001 of the plastic lens 1000 is formed by the mold 4000 and the mold 5000. As shown in FIG. 9, one optical surface 1001A of the lens unit 1001 is molded by a mold 4000 located in the mold 2000, and the other optical surface 1001B of the lens unit 1000 is positioned in the mold 3000. Molded with a mold 5000.

As described above with reference to FIGS. 8 and 9, the plastic lens 1000 having the highly accurate lens portion 1001 can be manufactured by pressing the collar portion 1002 of the plastic lens 1000 with the plurality of ejector pins 3001.
JP 2000-111182 A

  The central portion 1001C (see FIG. 7A) of the lens portion 1001 is used as a reference for adjusting the optical function when the plastic lens 1000 is installed in an optical scanning device or the like. This is where high-precision manufacturing is required.

  By the way, generally the periphery of the location pushed by the ejector pin is easily deformed due to the effect of being pushed by the ejector pin.

  In the example of the mold structure shown in FIG. 8, since the cross-sectional shape in the longitudinal direction of the lens unit 1001 is pressing the collar unit 1002 with a plurality of ejector pins 3001 from the convex side (the right side in FIG. 8), the lens unit 1001 The central portion 1001C of the first is closest to the ejector pin 3001. Therefore, with such a mold structure, the central portion 1001C of the lens portion 1001 that is required to be manufactured with high accuracy is deformed, resulting in trouble in adjusting the optical function. In particular, in a lens having a concave lens shape in the short direction, since the thickness of the lens portion is small and the plastic lens is easily deformed at the time of releasing, higher precision manufacturing is required.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens manufacturing method that appropriately prevents a deformation at the center of a lens that occurs at the time of releasing from a mold and manufactures a long optical lens appropriately.

In order to achieve the above object, a lens manufacturing method according to the present invention includes:
A lens portion having a meniscus cross-sectional shape in the longitudinal direction and a concave cross-sectional shape in the short-side direction; and a collar portion positioned outside the lens portion, including the collar portion in the longitudinal direction. A lens manufacturing method for manufacturing an optical lens satisfying a relational expression of 6 ≦ A / B ≦ 30 in which the maximum length A and the maximum length B including the collar portion in the short direction are formed by molding,
From the side where the cross-sectional shape in the longitudinal direction of the lens part is concave, the collar part is pushed with a plurality of ejector pins, and the molded optical lens is released from the mold.

  According to the lens manufacturing method according to the present invention, it is possible to prevent the deformation at the center of the lens that occurs at the time of releasing from the mold and appropriately manufacture a long optical lens.

  First, an optical scanning device using a plastic lens (optical lens) manufactured by the lens manufacturing method according to the present invention will be described.

  FIG. 1 is a perspective view showing an optical scanning device.

  The optical scanning device 10 has a configuration in which a semiconductor laser 12, a rotary polygon mirror 15, an fθ lens 16 and the like are installed in a housing 11, and when the laser beam L is irradiated by the optical scanning device 10, A latent image is written on the photosensitive drum 1.

  The laser beam L emitted from the semiconductor laser 12 is converted into parallel light by the collimating lens 13 and is incident on the rotating polygon mirror 15 that passes through the first cylindrical lens 14 of the first imaging optical system and rotates at high speed. The laser beam L reflected by the rotary polygon mirror 15 passes through the second imaging optical system including the fθ lens 16 and the second cylindrical lens 17 and enters the reflection mirror 18, and enters the photosensitive drum 1 with a predetermined spot diameter. Irradiated. The writing of the image information on the photosensitive drum 1 is executed at a predetermined timing by detecting the laser beam L with the index sensor 19.

  The second cylindrical lens 17 may use a toroidal surface or a free-form surface, but here they are collectively referred to as a “cylindrical lens”.

  When the optical scanning device using the plastic lens (optical lens) manufactured by the lens manufacturing method according to the present invention is configured as shown in FIG. 1, the second cylindrical lens 17 has a concave shape in the lateral direction. Therefore, in order to obtain a condensing power in the short direction, that is, in the sub-scanning direction, it is necessary to add a positive refractive power in at least one of the fθ lens 16 and the reflection mirror 18 in the sub-scanning direction.

  In this embodiment, the photosensitive drum 1 is irradiated with the laser beam L. However, the irradiated body is not limited to the photosensitive drum, and may be another irradiated body such as a photosensitive film.

  A second cylindrical lens 17 in FIG. 1 is a plastic lens manufactured by the lens manufacturing method according to the present invention, and is molded by filling a molten resin material into a mold.

  The plastic lens manufactured by the lens manufacturing method according to the present invention is used for the second cylindrical lens 17 in the optical scanning device 10 shown in FIG. 1, but any other lens can be used as long as it is used in the optical scanning device. It may be used for lenses. Hereinafter, the second cylindrical lens 17 is simply referred to as a plastic lens 17.

  FIG. 2 is a detailed view of the plastic lens 17.

  2A is a perspective view of the plastic lens 17, FIG. 2B is a front view of the plastic lens 17, FIG. 2C is a cross-sectional view of the plastic lens 17 taken along the line C-C in FIG. (D) is a side view of the plastic lens 17. FIG.2 (e) is sectional drawing of D part in Fig.2 (a).

  As shown in FIG. 2B, a lens portion 17A having an optical function is provided at the center of the plastic lens 17. In addition, a flange portion 17B is provided in a box shape outside the lens portion 17A. The cross-sectional shape in the longitudinal direction of the lens portion 17A is a meniscus shape as shown in FIG. 2 (c), and is convex upward in FIG. 2 (c). Further, the cross-sectional shape in the short direction of the lens portion 17A is a concave shape as shown in FIG.

  When the plastic lens 17 is molded by a mold, the plastic lens 17 is released from the mold by pressing the flange portion 17B with an ejector pin. A lens manufacturing method for manufacturing the plastic lens 17 will be described later.

  As shown in FIG. 2D, lens positioning portions 17C to 17E are formed on the outer peripheral surface of the plastic lens 17 on the same surface. The lens positioning portion 17C has a protruding shape and serves as a reference when the plastic lens 17 is installed on the installation base 20 (see FIG. 1) of the optical scanning device 1 (that is, a positioning reference).

The lens positioning portions 17D and 17E also serve as a reference when the plastic lens 17 is placed on the installation base 20, and the lens positioning portions 17D and 17E have a surface substantially parallel to the scanning direction of the plastic lens 17 (the optical axis of the optical lens). Have. It can be said that it has a surface substantially perpendicular to the bottom surface of the buttock. In order to facilitate the installation of the plastic lens 17 on the installation base 20, it is preferable that the relationship between the length α of the lens positioning portions 17D and 17E and the height β of the plastic lens 17 satisfies the following relational expression.
1/3 ≦ α / β ≦ 2/3 (1)
More preferably, the following relational expression is satisfied.
1/2 ≦ α / β ≦ 2/3 (1) ′
Three lens positioning portions are provided on the outer peripheral surface of the plastic lens 17, but the plastic lens 17 can be satisfactorily installed on the installation table 20 if there are at least two lens positioning portions. When the optical lens is viewed from the short side (the state shown in FIG. 2D), the lens positioning unit is located at a position intermediate between the longitudinal center of the optical lens (position 17C) and the end of the optical lens. However, it is preferable that the symmetry is provided at a position closer to the end of the optical lens. The length γ of the lens positioning portion in the longitudinal direction of the optical lens is preferably 1 mm or more and 15 mm or less.

The plastic lens 17 is a long lens, and as shown in FIG. 2B, the maximum length A including the flange portion 17B in the longitudinal direction of the plastic lens 17 and the maximum including the flange portion 17B in the short direction. The relationship with the length B satisfies the following formula (2).
6 ≦ A / B ≦ 30 (2)
In order to reduce the length in the sub-scanning direction, a shape satisfying the following expression (2) ′ is preferable, and a shape satisfying the following expression (2) ″ is more preferable.
10 ≦ A / B ≦ 30 (2) ′
20 ≦ A / B ≦ 30 (2) ”
Moreover, it is preferable that the concave curvature does not become too large. More specifically, the distance in the optical axis direction (Y in FIG. 2E) at the center in the short direction of the lens portion and the distance in the optical axis direction at the end portion in the short direction of the lens portion (Y in FIG. 2E). It is preferable that ') and the following relational expression are satisfied.
0.9 ≦ Y / Y ′ <1 (3)
Next, a method for manufacturing the plastic lens 17 using a mold will be described in detail.

  3 and 4 are sectional views of the mold in the longitudinal direction of the plastic lens 17.

  The outer shape of the plastic lens 17 is basically formed by the first mold 100 and the second mold 200. The molding of the lens portion 17A in the plastic lens 17 will be described later.

  The molten resin material is injected from the gate 401 into the cavity 300 and filled at the position where the first mold 100 and the second mold 200 are in contact with each other. The filling of the molten resin material is performed using the runner 400 and the gate 401 as a route. As shown in FIG. 3, the molten resin material is filled into the mold from a position corresponding to the longitudinal end portion of the plastic lens 17, and the resin material is filled from the lens portion of the plastic lens 17.

  When the filled resin material is cooled to some extent, the second mold 200 moves in the direction a with respect to the first mold 100, and the first mold 100 and the second mold 200 are moved as shown in FIG. Separate. Reference numeral 500 denotes a third mold for molding the lens portion 17A of the plastic lens 17, and when the first mold 100 and the second mold 200 are separated from each other, a state as shown in FIG. 4 is obtained.

  In a state where the first mold 100 and the second mold 200 are separated from each other, the plastic lens 17 remains on the second mold 200 side. Thereafter, the plurality of ejector pins 201 presses the flange portion 17 </ b> B of the plastic lens 17 in the direction b shown in FIG. 4, whereby the plastic lens 17 is released from the second mold 200.

  The molding of the lens portion 17A in the plastic lens 17 will be described with reference to FIGS.

  FIG. 5 is a cross-sectional view of the mold in the lens portion 17A of the plastic lens 17. As shown in FIG.

  The outer shape of the plastic lens 17 is formed by the first mold 100 and the second mold 200 as described with reference to FIGS. 3 and 4, and the lens portion 17A of the plastic lens 17 is formed by the third mold 500 and the fourth mold. Molded by the mold 600. As shown in FIG. 5, one optical surface 171A of the lens portion 17A is molded by a third mold 500 located in the first mold 100, and the other optical surface 172A of the lens portion 17A is a second mold. 200 is molded by a fourth mold 600 located in 200.

  FIG. 6 is a cross-sectional view of the mold in the short direction of the plastic lens 17.

  The plastic lens 17 has a shape in which the cross-sectional shape of the lens portion 17A in the short direction (the direction B shown in FIG. 2B) has a negative refractive power.

  As can be seen in FIG. 6, the flange portion 17 </ b> B of the plastic lens 17 is molded by the first mold 100 and the second mold 200, and the lens portion 17 </ b> A of the plastic lens 17 is molded by the third mold 500 and the fourth mold 600. Is done. In addition, a plurality of ejector pins 201 press the flange portion 17B of the plastic lens 17. The thickness t of the flange portion 17B pushed by the ejector pin 201 is 1.5 mm or more and 3.0 mm or less.

  Since the plastic lens 17 is projected by the plurality of ejector pins 201, the second mold 200 is provided with a punch taper T at a location in contact with the plastic lens 17. The draft taper T is preferably 3 ° or more and 10 ° or less, particularly preferably 5 ° or more and 9 ° or less, from the viewpoint of releasability from the second mold 200, weld of the lens portion 17A, and the like.

  Returning to FIG. 4, the positional relationship between the central portion 173A of the lens portion 17A and the ejector pin 201 will be described.

  Since the central portion 173A of the lens portion 17A is used as a reference for adjusting the optical function when the plastic lens 17 is installed in the optical scanning device 10 or the like, it is required to be manufactured with particularly high accuracy among the lens portion 17A. It is a place. In particular, when the lens shape in the short direction is a concave shape, the thickness of the lens portion is small, and the plastic lens is easily deformed at the time of releasing, so that higher accuracy is required. In addition, the periphery of the portion pushed by the plurality of ejector pins 201 is likely to be deformed due to the effect of being pushed by the plurality of ejector pins 201.

  Therefore, the flange portion 17B is pushed with a plurality of ejector pins 201 from the concave side of the lens portion 17A in the longitudinal direction (the right side in FIG. 4), and the molded plastic lens 17 is released from the second mold 200 and the like. . In this way, if the flange portion 17B is pushed by the plurality of ejector pins 201 from the concave side of the lens portion 17A, the plastic lens 17 is released in a state where the central portion 173A is away from the ejector pin 201. Therefore, it is possible to prevent the deformation of the central portion 173A that is required to be manufactured and to manufacture the long plastic lens 17 appropriately.

  Although the embodiment of the present invention has been described with reference to the drawings, the present invention is not limited to the embodiment, and changes and additions within the scope not departing from the gist of the present invention are included in the present invention. .

It is a perspective view which shows an optical scanning device. It is detail drawing of a plastic lens. It is sectional drawing of the metal mold | die in the longitudinal direction of a plastic lens. It is sectional drawing of the metal mold | die in the longitudinal direction of a plastic lens. It is sectional drawing of the metal mold | die in the lens part of a plastic lens. It is sectional drawing of the metal mold | die in the transversal direction of a plastic lens. It is explanatory drawing of the plastic lens which provided the collar part on the outer periphery. It is the schematic which showed the structure of the metal mold | die which shape | molds a plastic lens. It is sectional drawing of the metal mold | die in the lens part of a plastic lens.

Explanation of symbols

17 plastic lens 17A lens part 17B collar part 17C, 17D, 17E positioning part 100 first mold 200 second mold 201 ejector pin 500 third mold 600 fourth mold

Claims (2)

The lens section has a meniscus cross-sectional shape in the longitudinal direction and a concave cross-sectional shape in the short-side direction, and a collar portion located outside the lens section, including the collar portion in the longitudinal direction. A lens manufacturing method for manufacturing an optical lens satisfying a relational expression of 6 ≦ A / B ≦ 30 in which the maximum length A and the maximum length B including the collar portion in the short direction are formed by molding,
A lens manufacturing method, comprising: pressing the flange portion with a plurality of ejector pins from a concave side in the longitudinal direction of the lens portion to release the molded optical lens from the mold. The lens manufacturing method according to claim 1, wherein a molten resin material is filled into the mold from a position corresponding to an end in the longitudinal direction of the optical lens.

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