JP3757135B2 - Lens holder for optical pickup and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lens holder for an optical pickup and a method for manufacturing the same.
[0002]
[Prior art]
As an optical information recording / reproducing apparatus, for example, a video disc player, a digital audio player, an optical disc file, and the like are known. In recent years, a digital video disc (DVD) has been developed as a device capable of recording and reproducing a large amount of information. The optical pickup for performing the focus control and tracking control of these devices is a disc for detecting information by condensing the light beam that has passed through the objective lens provided in the lens holder for the optical pickup on the disc surface. It is necessary to compensate for defocus due to surface shake and form an image of the light beam on the disk surface. Also, if there is a deviation (optical axis radial deviation) between the signal track (information bit string) on the disc and the optical axis of the objective lens, accurate reading cannot be performed. It is necessary to make the optical axis of the lens coincide with the signal track.
Such defocus compensation is performed by a focus servo, and signal track shift compensation is performed by a tracking servo.
[0003]
Conventional lens holders for optical pickups are manufactured by injection molding a resin material.
A conventional lens holder molding method will be described with reference to FIG. 4 (a) and 4 (b) are partial cross-sectional views of conventional lens holder injection molds having different gate positions. In the injection mold, a cavity 13 is formed by a fixed mold plate 11 and a movable mold plate 12. The cavity 13 includes a cavity 13a that forms a lens support portion and a cavity 13b that forms a bearing portion, and a core pin 15 is disposed through the cavity 13b.
Using this mold, the core pin 15 is disposed on the movable side mold plate 12, the end of the core pin 15 is inserted into the concave portion 16 provided on the fixed side mold plate 11, and the core pin 15 is attached to the fixed side mold plate 11. Further, molding is performed by restraining with the movable side template 12 and injecting a resin material from the gate. The resin material is usually injected depending on whether an odd number of pinpoint gates 17 are used (FIG. 4A) or side gates 18 are used (FIG. 4B).
Japanese Patent No. 2886741 describes that a gate is provided at a position where the filler is oriented in the axial direction over substantially the entire axial direction of the bearing portion.
[0004]
[Problems to be solved by the invention]
However, with the conventional molding method, it is extremely difficult to maintain the core pin 15 in a vertical state with respect to the lens receiving surface. Therefore, the lens receiving surface and the bearing surface of the optical pickup lens holder cannot be formed vertically. This has the problem that the light beam that has passed through the objective lens cannot be focused on the disk surface, making it difficult to write and detect information.
Alternatively, in an optical pickup lens holder in which the lens receiving surface and the bearing surface are not vertical, the difficulty of fixing the objective lens is increased, resulting in low workability and a high defect rate.
In particular, in the case of a lens holder corresponding to an optical pickup in which formats of different standards such as DVD and CD coexist, two or more lens receiving surfaces may be provided on the lens support portion. However, there is a problem that it cannot be maintained with high accuracy.
[0005]
In the conventional molding method, as shown in FIG. 4A, when an odd number of pinpoint gates 17 is used, a weld line is generated near the intermediate portion between the gates and the roundness of the bearing surface is poor. Since the accuracy of the bearing portion must be increased by post-processing, there is a problem that productivity is lacking and manufacturing cost increases.
Further, as shown in FIG. 4B, when the material is injected from the outer surface of the cavity 13 using the side gate, a difference in internal pressure of the material occurs between the position far from the gate 18 and the vicinity of the gate, and the accuracy of the lens receiving surface is increased. There was a problem that did not come out.
In particular, when a liquid crystalline resin is used as a resin material, there is a problem that the mechanical strength as a lens holder is not sufficiently obtained.
Further, in Japanese Patent No. 28867741, a pinpoint gate is arranged around the bearing portion. Therefore, in recent lens holders with a small and light bearing hole of 1.2 mm to 3 mm, very fine sprues and gate openings are provided. Must be used. Making the sprue and the gate opening fine has problems such as difficulty in mold production, and short shots easily occur in a resin material with a high elastic modulus.
In addition, when a pinpoint gate is arranged around the bearing portion and liquid crystal resin is injected as a resin material, when the molten resin filling the bearing portion flows into the lens support portion, the bearing portion and the lens support portion Resin turbulence tends to occur at the intersection (bridge), and there is a possibility that a lens holder with a uniform molten resin flow cannot be obtained.
[0006]
The present invention has been made to cope with such a problem. An optical pickup in which a bearing surface can be formed perpendicular to a lens receiving surface, the bearing surface is excellent in roundness, and has excellent mechanical strength. An object of the present invention is to provide a lens holder and a manufacturing method thereof.
[0007]
[Means for Solving the Problems]
The present invention provides a lens holder for an optical pickup comprising a resin molded body having a lens support portion having a lens receiving surface and a bearing portion having a bearing surface provided vertically on the lens receiving surface. The body is a resin molded body by injection molding having a bearing surface without a weld line, and a gate mark formed at the end of the bearing section on the opposite side of the lens support section and at the inner peripheral edge. It is characterized by.
Further, the gate mark is formed in parallel with the inner peripheral edge of the bearing portion.
The resin is a liquid crystalline resin.
Further, a fibrous filler is blended in the liquid crystalline resin.
[0008]
The manufacturing method of the present invention is an optical device comprising a resin molded body by injection molding comprising a lens support portion having a lens receiving surface and a bearing portion having a bearing surface without a weld line provided vertically on the lens receiving surface. Manufacturing method of a lens holder for a pickup, wherein the bearing surface is formed by a core pin provided on a movable side mold plate, and the core pin is disposed in a vertical direction with respect to a lens receiving surface forming surface of the movable side mold plate. The core pin is disposed without being constrained in the cavity of the fixed mold plate that abuts the movable mold plate, and a gate is formed in the gap between the bearing cavity of the fixed mold plate and the core pin, Resin is injected through the gate.
[0009]
The lens holder for the optical pickup is molded by injecting resin from the gate provided in the gap between the bearing cavity and the core pin of the fixed side mold plate, so that the resin material is directed from the bearing edge to the outer periphery of the lens support. Are distributed evenly and molded. As a result, uneven thickness can be prevented and the roundness of the bearing surface is improved.
[0010]
Further, when the mechanical strength in the case of using the liquid crystalline resin was studied, in the case of the conventional gate shown in FIGS. 4A and 4B, when the liquid crystalline resin was molded, a weld was generated on the bearing surface. Further, when the resin was injected from the surface side (lens receiving surface side) of the lens support portion toward the bearing portion, the orientation of the resin or filler inside the lens holder was disturbed. However, when resin is injected from the peripheral part of the bearing part on the opposite side of the lens support part toward the lens support part, the orientation of the resin or filler is hardly disturbed, and the bearing part extends toward the lens support part outer peripheral part. Uniformly oriented. As a result, a lens holder for an optical pickup having excellent mechanical strength was obtained, in which no turbulent resin flow occurred near the weld line or bridge portion on the bearing surface.
[0011]
In the lens holder molding method, the core pin that forms the bearing surface is provided on the movable side mold plate and is disposed without being constrained by the fixed side mold plate when the mold is closed, thereby preventing the pin from being inclined.
[0012]
Further, by forming the lens receiving surface forming surface vertically on the movable side template provided with the core pin, the lens holder is formed into a molded body in which the lens receiving surface and the bearing surface are vertical.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The lens holder for an optical pickup according to the present invention will be described with reference to FIG. FIG. 1A is a plan view seen from the surface side (lens receiving surface side) of the lens support portion in the lens holder, and FIG. 1B is a cross-sectional view taken along line AA.
The lens holder 1 for optical pickup is formed of resin, and the lens support portion 2 and the bearing portion 3 are connected by a bridge portion 3b. The lens support portion 2 is provided with a bearing hole 2a and a lens receiving surface 4 on the inner periphery of the lens mounting hole 4a, and a bearing surface 3a is provided vertically on the lens receiving surface 4 at the bearing portion. Generally, the bearing portion 3 is provided at the center of the lens holder 1, and a gate is formed at the end of the bearing portion 3 on the opposite side of the lens support portion 2. One or a plurality of lens mounting holes 4 a having a lens receiving surface 4 are provided at an eccentric position with respect to the bearing portion 3 of the lens support portion 2.
[0014]
The resin forming the lens holder 1 is, for example, nylon resin, polyphenylene sulfide resin (hereinafter abbreviated as PPS), polyacetal resin, polyether ether ketone resin, polyether nitrile resin, fluororesin, liquid crystal resin (hereinafter LCP). And a thermoplastic resin such as abbreviation). These synthetic resins can be used alone or as a mixed resin.
Among these, the PPS composition and LCP composition which mix | blended the fibrous filler which can fully satisfy the high elastic modulus request | requirement of the lens holder 1 are preferable.
In particular, LCP is desirable because it has excellent damping force characteristics in addition to high elastic modulus, excellent orientation in the lens holder 1, and can increase the roundness of the bearing surface. Even if LCP is used, welds are not generated on the bearing surface by employing the manufacturing method described later.
[0015]
Examples of the LCP include aromatic polyesters (liquid crystal polyesters), aromatic polyester imides (liquid crystal polyester imides), aromatic polyester amides (liquid crystal polyester amides), and polycarbonates (liquid crystal polycarbonates) that can form an anisotropic molten phase.
Further, the LCP is preferably an LCP composition in which a fibrous filler is blended for increasing the elastic modulus.
[0016]
As the fibrous filler, any of inorganic fibers and organic fibers can be used. For example, glass fibers, graphite fibers, carbon fibers, tungsten core wires, carbon fibers, or the like, so-called boron fibers or silicon carbide fibers, aromatic polyamide fibers, or the like obtained by vapor deposition of boron or silicon carbide can be exemplified. Moreover, the fiber which processed these fiber surfaces with the epoxy-type and amino-type silane coupling agent may be sufficient.
[0017]
A method for manufacturing the lens holder 1 will be described with reference to FIG. FIG. 2 is a partial sectional view of an injection mold of the lens holder.
In the injection mold 5, a cavity 8 is formed by a fixed mold 6 and a movable mold 7. The cavity 8 includes a cavity 8a that forms a lens support portion and a cavity 8b that forms a bearing portion. In addition, a sprue and a runner (not shown) that are resin material passage portions to the cavity 8 are formed on the fixed-side template 6, and an ejector pin (not shown) that is a mechanism for taking out a molded product is formed on the movable-side template. (Omitted) is provided. A core pin 9 penetrating the center of the cavity 8b is provided on the movable side mold plate 7. A gate 10 is formed in the gap between the bearing cavity of the fixed side template 6 and the core pin.
[0018]
When the fixed mold 6 and the movable mold 7 of the injection mold 5 are brought into contact with each other, the core pin 9 can be held in the cavity without being restricted by the fixed mold 6. A resin material is injected into the cavity 8 from the gate 10 formed by the gap between the bearing portion cavity and the core pin. Since the gate 10 is the outer peripheral portion of the end portion of the core pin 9 and the peripheral portion of the bearing portion, the injected resin material flows evenly into the cavities 8b and 8a, and the lens receiving surface 4 of the lens holder. While making the bearing surface vertical, turbulent flow of the resin material does not occur at the bridge portion.
Moreover, as shown in FIG. 5, it is preferable that the entire length of the lens holder can be managed by setting the gate portion 10a to the inner side of the end surface of the bearing portion.
Note that the size of the gate port is set so that the gate can be easily cut in the taking-out process after the injection molding and the resin material can be smoothly filled in the cavity.
[0019]
【Example】
Using LCP (Vectra A230 manufactured by Polyplastics Co., Ltd. (containing 30% by weight of carbon fiber)), the lens holder for an optical pickup having the shape shown in FIG. The obtained lens holder had a bearing surface roundness of 1 to 2 μm and a standard deviation of 0.3 μm. Further, no weld line was observed in the bearing portion. On the other hand, when the pin gate shown in FIG. 4A was used for injection molding with the same resin material, the obtained lens holder had a bearing surface roundness of 5 to 7 μm and a standard deviation of 0.8 μm. In addition, a weld line was observed between the pin gates of the bearing portion.
[0020]
The orientation state of the fibrous filler in the cross-sectional view (FIG. 1B) of the lens holder obtained by the production method of the present invention was examined using a microscope. The results are shown in FIG. FIG. 3 is a diagram showing the orientation state of the fibrous filler. The fibrous filler is oriented from the end face of the bearing part in the anti-lens support part toward the lens support part direction (B direction in the figure), and then toward the outer periphery direction of the lens support part (C direction in the figure). Oriented. That is, even in the bridge portion formed of the bearing portion 3 and the lens support portion, the lens support portion is not oriented in the axial direction (B direction in the figure) of the bearing portion 3, and the lens support portion outer peripheral direction (in the figure). , C direction).
[0021]
【The invention's effect】
The lens holder for an optical pickup according to the present invention comprises a resin molded body including a lens support portion having a lens receiving surface and a bearing portion having a bearing surface provided vertically on the lens receiving surface. Since the body is a resin molded body molded by injecting resin from the gate provided at the end of the bearing portion on the opposite side of the lens support portion, the bearing surface is excellent in roundness and the lens receiving surface Parallelism can be maintained with high accuracy. As a result, even when the lens support portion has two or more lens receiving surfaces, the parallelism between the lens receiving surfaces can be maintained with high accuracy.
[0022]
Also, even if the resin molded body molded by injecting resin from the gate is a liquid crystalline resin, no weld line is generated on the bearing surface, and since a fibrous filler is blended, the mechanical strength is increased. Excellent.
[0023]
In the manufacturing method of the present invention, the bearing surface is formed by a core pin provided on the movable side mold plate, and the core pin is disposed in the vertical direction with respect to the lens receiving surface forming surface of the movable side mold plate. The core pin is disposed without being constrained in the cavity of the plate, and a gate is formed in the gap between the bearing cavity and the core pin of the fixed side mold plate, and the resin is injected through the gate. It is possible to form a bearing surface that does not occur and always maintains a vertical state relative to the lens receiving surface. As a result, the lens holder obtained by this manufacturing method can condense the light beam that has passed through the objective lens onto the disk surface, facilitates writing and detection of information, and has a sufficient function as a lens holder for optical pickups. Satisfied with.
[Brief description of the drawings]
FIG. 1 is a plan view and a sectional view of a lens holder.
FIG. 2 is a partial cross-sectional view of an injection mold for a lens holder.
FIG. 3 is a diagram showing an orientation state of a fibrous filler.
FIG. 4 is a partial cross-sectional view of a conventional lens holder injection mold.
FIG. 5 is a partial cross-sectional view of a mold in which a gate portion is provided on the inner side of a bearing portion end surface.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lens holder 2 Lens support part 3 Bearing part 4 Lens receiving surface 5 Injection mold 6 Fixed side mold plate 7 Movable side mold plate 8 Cavity 9 Core pin
10 Gate

Claims (5)

In a lens holder for an optical pickup comprising a resin molded body provided with a lens support portion having a lens receiving surface and a bearing portion having a bearing surface provided vertically on the lens receiving surface,
The resin molded body has a bearing surface having no weld line , and a resin molded body by injection molding in which a gate mark is formed at an end portion of the bearing portion on the opposite side of the lens support portion and at an inner peripheral edge portion. A lens holder for optical pickups. The lens holder for an optical pickup according to claim 1, wherein the gate mark is formed in parallel with an inner peripheral edge portion of the bearing portion.   The lens holder for an optical pickup according to claim 1 or 2, wherein the resin is a liquid crystalline resin.   The lens holder for an optical pickup according to claim 3, wherein the liquid crystalline resin is blended with a fibrous filler. Manufacture of a lens holder for an optical pickup comprising a resin molded body by injection molding provided with a lens support portion having a lens receiving surface and a bearing portion having a bearing surface without a weld line provided vertically on the lens receiving surface A method,
The bearing surface is formed by a core pin provided on the movable side mold plate, and the core pin is disposed in a vertical direction with respect to the lens receiving surface forming surface of the movable side mold plate,
The core pin is disposed without being constrained in the cavity of the fixed side mold plate that abuts on the movable side mold plate,
A method for manufacturing a lens holder for an optical pickup, comprising: forming a gate in a gap between the bearing cavity of the fixed side mold plate and the core pin; and injecting resin through the gate.

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