JP2006142510A - Injection mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which enhances the mold releasability of a molded product even if no mold release agent is used and can enhance the seizing resistance, abrasion resistance, heat resistance and corrosion resistance of a mold. <P>SOLUTION: The injection mold 10 is composed of molds 10A and 10B for injection-molding a light guide member for guiding the light incident from a light source to cause surface emission and equipped with mold members 12A, 12B and 13 which demarcate the outer shape of the light guide member and can be moved between a mold clamping position and a mold opening position, the transfer members 11A and 11B provided to the mold members to transfer an optically functional surface to the light guide member and the mold release member 14 which is brought into slide contact with the mold members and the transfer members to release the molded product cured in the space surrounded by the mold members and the transfer members. A hard thin film layer with Vickers hardness of 500 Hv or above is formed to a region with which at least two members among the mold members, the transfer members and the mold release member come into slide contact. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mold for injection molding a light guide member that guides light incident from a light source to emit light and illuminate a liquid crystal display panel.

  As illustrated in FIGS. 7A and 7B, the light guide member 31 that emits surface light from the light source has the following characteristics: A fine uneven dot pattern 31c for diffusing and reflecting light is formed on at least one of the surfaces (reflection surface 31a and emission surface 31b). The dot pattern 31c includes, for example, a hemisphere, a cylinder, a rough surface, a polygonal prism, a random irregular shape, and the like as viewed from the cross section in the thickness direction shown in FIG. 7B. It is formed in a composite manner with respect to the optical member 31, or is formed by changing the size and density of the pattern.

  As shown in FIG. 7 (c), a general light guide member is manufactured by producing a transfer mold 21A (also a transfer mold 21B in some cases) having a transfer surface 21a in which the dot pattern is inverted, and this transfer surface 21a. The shape is molded by transferring it to a resin such as acrylic or polycarbonate. Known molding methods include injection molding, hot press molding, UV curing molding, thermosetting molding, and the like.

  In addition to forming the transfer surface 21a directly, a master member having the same shape as the dot pattern is manufactured, and nickel, copper, nickel alloy or the like is used by using the master member. There is a method of manufacturing by electroplating casting (electroforming).

For example, Patent Document 1 describes a technique for improving mold releasability and mold life by forming a hard film on a transfer surface of a mold. Patent Document 2 describes a technique for producing a mold by electroforming.
JP 2003-19717 A JP 2000-98383 A

  The mold is configured by combining a plurality of members, and the dimensional accuracy of each member is very high. For this reason, there is a possibility that a state where the members to be combined come into contact with each other at an inappropriate position, that is, so-called galling occurs. However, neither of Patent Documents 1 and 2 describes a technical problem of improving galling resistance and improving die life.

Further, there are the following problems. That is,
1. For example, in the case of injection molding using a mold having a V-shaped transfer surface formed by electroforming, the mold releasability between the molded product and the transfer surface is good. Required. As a countermeasure against this, there is a method in which a mold release agent such as fluorine (for example, ethylene tetrafluoride polymer) is directly applied to the mold before molding. In this case, if the coating is uneven, the coating marks are transferred to the molded product as they are, resulting in a poor appearance of the molded product. In addition, dust may be involved at the time of application, leading to poor appearance.

Furthermore, the release agent is applied by a manual operation using a spray robot or spray, but since it is necessary to apply the release agent for each injection shot or every several shots, in any case, This leads to an increase in material costs.
2. Regarding the corrosion resistance of the mold transfer surface, in particular, in the case of polycarbonate resin molding, the temperature at the time of injection from the injection molding machine to the cavity portion reaches about 300 ° C., and reaches near the oxidation point of the metal. At this time, a gas generated in a very small amount from a resin or an injection molding machine and a mold may cause a chemical reaction, and corrosion due to oxidation may occur.
3. As shown in FIG. 8, the die for injection molding is assembled after the mold dies 22A and 22B and the mold 23 which are clamped and opened by the guide post 25 are assembled. The transfer molds 21A and 21B, the push pins 24, and the like are assembled. An injection molding machine 26 is provided in a part of the mold 23 to fill the cavity of the mold with resin. The mold 23 and the transfer molds 21A and 21B are assembled with a gap of 5 μm or less. Further, since the mold 23 and the transfer molds 21A and 21B are desired to have the same thermal expansion coefficient, the same material is used. Therefore, since the flat surfaces of the same material are in contact with each other at the time of assembly, it is a condition that galling is likely to occur.

The above-mentioned galling occurs at the time of assembling work or disassembling work of the mold 23 and the transfer molds 21A and 21B, and the galling part may not come off at all, or the mold may be defective due to breakage.
4). FIG. 9 is a schematic diagram of an injection molding process using the injection mold shown in FIG. 8 regarding the wear resistance and sliding property of the push pin .

  In FIG. 9A, the molten resin 27A injected from the injection molding machine 26 is filled in the cavity 28, and the transfer surfaces of the transfer molds 21A and 21B are cured while being transferred.

  Next, in FIG. 9B, in order to smoothly separate the molded product 27B cured at the cavity portion 28 from the transfer molds 21A and 21B, the molded product 27B and the molded product 27B are transferred by extruding the molded product 27B with the push pin 24 when the mold is opened. A gap is formed between the molds 21A and 21B, and the molded product 27B can be smoothly released and taken out.

  In the case of molding in which injection shots are continuously performed several times, the transfer molds 21A and 21B, the mold 23 and the push pin 23 are slid and worn, and when the wear amount increases, the push pin 24 is straightened. In some cases, the degree of separation decreases and an accurate mold release operation cannot be performed, and the push pin 24 is broken and becomes defective.

  The present invention has been made in view of the above problems, and its object is to improve the mold release of a molded product without using a mold release agent, and to prevent mold galling, abrasion resistance, heat resistance, and resistance. It is to provide a technology that can improve the corrosivity.

  In order to solve the above-mentioned problems and achieve the object, an injection mold according to the present invention is a mold for injection-molding a light guide member 4 that guides light incident from a light source 7 and emits surface light. The molds 10A and 10B, which define the outer shape of the light guide member, are movable between a mold clamping position and a mold opening position, and are provided on the mold member. The transfer members 11A and 11B for transferring the optical functional surface 4e to the member, the mold member and the transfer member are in sliding contact with each other, and the molded product cured in the space surrounded by the mold member and the transfer member is separated. A mold release member 14 is provided, and a hard thin film layer having a Vickers hardness of 500 Hv or more is formed at a site where at least two of the mold member, the transfer member, and the mold release member are in sliding contact.

  In the above mold, the hard thin film layer is formed by vacuum deposition of any of DLC, TiCN, TiN, TiAlN, TiCrN, and CrN.

  Further, in the above mold, the transfer member is formed by electroplating casting.

  The mold for injection molding of the present invention forms a hard thin film layer having a Vickers hardness of 500 Hv or more at a site where at least two members of the mold member, the transfer member, and the release member are in sliding contact, It is created by assembling a transfer member and a release member.

  As described above, according to the present invention, the mold releasability of a molded product can be improved without using a mold release agent, and the galling resistance, wear resistance, heat resistance, and corrosion resistance of the mold can be improved. There is an effect that can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.

  FIG. 1 is an exploded perspective view of an injection mold according to an embodiment of the present invention, and FIG. 2 is a side sectional view of the injection mold according to an embodiment of the present invention.

  As shown in FIGS. 1 and 2, the injection mold 10 according to the present embodiment is used, for example, to form a light guide member that emits surface light from light incident from a light source. The fixed mold 10A is connected to the movable mold 10B via a guide post 15 that is movable in the vertical direction. The guide post 15 is driven up and down by a cylinder mechanism (not shown) or the like, and moves the movable mold 10B between a mold clamping position and a mold opening position.

  The fixed mold 10A includes a die set 12A as a base, a mold 13 assembled to the die set 12A, a transfer mold 11A incorporated in a space surrounded by the mold 13, and a push pin 14.

  A part of the mold 13 becomes a side wall portion of the cavity that defines the side surface of the molded product. The push pin 14 slidably penetrates the die set 12A and the transfer mold 11A, and is driven up and down by a cylinder mechanism (not shown). About 4 to 10 push pins 14 are provided according to the material and size of the molded product. The die set 12A and the mold 13 are divided in the vertical direction in the through hole 12a in order to form a hard thin film layer to be described later in the through hole 12a in which the push pin 14 is in sliding contact.

  On the other hand, the movable mold 10B includes a die set 12B as a base and a transfer mold 11B assembled to the die set 12B. The transfer mold 11B has a gap corresponding to the thickness of the molded product with respect to the transfer mold 11A when the mold is clamped. It is attached to the die set 12B so as to face each other with a (cavity part).

  A nozzle 16a of an injection molding machine 16 is attached to a part of the mold 13 at a position communicating with the cavity between the transfer molds 11A and 11B when the mold is clamped.

  Molten resin (for example, polycarbonate or acrylic) injected from the injection molding machine 16 by a screw or plunger (not shown) is filled in the cavity, and the transfer surfaces of the transfer molds 11A and 11B are transferred and cured.

  Next, in order to smoothly separate the molded product cured at the cavity from the transfer molds 11A and 11B, the molded product and the transfer molds 11A and 11B are smoothly released by pushing the molded product with the push pin 3 when the mold is opened. To be taken out.

  In the present embodiment, at least one of the transfer surfaces 11a and 11b of the transfer molds 11A and 11B that are in contact with the molded product, the side surfaces 11c and 11d of the transfer molds 11A and 11B that are in sliding contact with the mold 13, and the side surface 13a of the mold 13 At least one of the die set 12A that is in sliding contact with the push pin 14, the insertion hole 12a of the transfer mold 11A, and the outer peripheral portion 14a of the push pin 14 has a surface hardness of Vickers hardness of 500 Hv or more, preferably 1000 Hv or more. The hard thin film layer which has is formed.

  For the hard thin film layer, for example, non-metallic DLC (Diamond Like Carbon) or metallic TiCN, TiN, TiAlN, TiCrN, CrN is used, and any one of them is formed by a vacuum deposition technique. Or at least two kinds of materials are combined to form a film thickness of 10 μm or less.

  3 shows the Vickers hardness representing the surface hardness of each hard thin film material, FIG. 4 shows the friction coefficient μ representing the lubricity of each hard thin film material, and FIG. 5 represents the heat resistant temperature representing the heat resistance of each hard thin film material. Each of the materials described above has physical properties such that the Vickers hardness is 1000 Hv or more, the friction coefficient μ is 0.05 or more, and the heat resistant temperature is 350 ° C. or more.

  As an example of the hard thin film layer, for example, when the hard thin film layer of the transfer mold 11A is formed by DLC, the material of the hard thin film layer formed on the outer peripheral portion 14a of the push pin 14 in contact with this is arbitrarily selected from the materials described above. It can be selected and may be omitted in some cases.

  In addition, when the hard thin film layer of the transfer mold 11A is formed of a titanium-based material or CrN, the material of the hard thin film layer formed on the push pin 14 in contact therewith is preferably DLC.

  Further, when sliding without lubrication, it is preferable to use DLC as one of the members that slide against each other, since seizure may occur and the wear of the mating material may proceed rapidly except for DLC.

  For the transfer surfaces of the transfer molds 11A and 11B, a master member having the same shape as the dot pattern corresponding to the optical function surface of the light guide member as a molded product is manufactured, and using this master member, nickel, copper, nickel alloy It is manufactured by electroplating casting.

  FIG. 6 is an exploded perspective view (a) and a side sectional view (b) of a liquid crystal display device including a light guide member that is injection-molded by using the injection mold according to the present embodiment.

  As shown in FIG. 6, the light guide member 4 is a plate-like optical component made of a translucent material such as transparent polycarbonate resin, and receives light from a plurality of point light sources (white LEDs, etc.) 7. An incident surface 4a for reflection, a reflection surface 4b on which a dot pattern 4e for scattering and reflecting the incident light beam is formed, and a light beam that is disposed opposite to the reflection surface 4b and scattered and reflected by the reflection surface 4b. And an end surface 4d that is parallel to the incident surface 4a and faces the incident surface 4a, and the light incident from the light source 7 is substantially orthogonal to the incident surface 4a. It is a side light type light guide member which radiates from.

  The light incident from the incident surface 4a travels toward the end surface 4d while being totally reflected by the reflecting surface 4b and the emitting surface 4c, and its direction is changed by the uneven dot pattern 4e formed on the reflecting surface 4b. The light is emitted directly from the emission surface 4c, or is reflected from the reflection member 5 disposed so as to face the reflection surface 4b and then emitted from the emission surface 4c. The light beam emitted from the emission surface 4c passes through the optical sheet 3 such as a diffusion sheet or a prism sheet, and illuminates the liquid crystal display panel 2 from the back side.

  In the liquid crystal display device 1, a surface light source device including an optical sheet 3, a light guide member 4, a reflection member 5, a reflection frame 6, and a light source 7 is a transmissive or semi-transmissive electric device in which a plurality of pixels are formed in a matrix. The optical (liquid crystal, LCD) panel 2 is arranged on the back surface.

1 is an exploded perspective view of an injection mold according to an embodiment of the present invention. It is a sectional side view of the injection mold of embodiment which concerns on this invention. It is a figure which shows the Vickers hardness showing the surface hardness of each hard thin film material illustrated as this embodiment. It is a figure which shows the friction coefficient (mu) showing the lubricity of each hard thin film material illustrated as this embodiment. It is a figure which shows the heat resistant temperature showing the heat resistance of each hard thin film material illustrated as this embodiment. It is the disassembled perspective view (a) and side sectional view (b) of the liquid crystal display device containing the light guide member injection-molded using the injection mold of this embodiment. It is the perspective view (a) of a general light guide member, II partial sectional view (b) of (a), and partial sectional view (c) of a transfer type. It is sectional drawing of a common injection mold. It is the schematic of the injection molding process using the general injection mold.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Electro-optical panel 3 Optical sheet 4 Light guide member 4a Incident surface 4b Reflective surface 4c Output surface 4d End surface 4e Dot pattern 5 Reflective member 6 Reflective frame 7 Light source 10A Fixed type 10B Movable type 11A, 11B Transfer type 12A , 12B Die set 13 Mold 14 Push pin 15 Guide post 16 Injection molding machine 11a-11d, 12a, 13a, 14a Hard thin film layer

Claims (3)

A mold for injection-molding a light guide member that guides light incident from a light source to emit surface light,
A mold member that defines an outer shape of the light guide member and is movable between a mold clamping position and a mold opening position;
A transfer member provided on the mold member for transferring an optical function surface to the light guide member;
A mold release member that slidably contacts the mold member and the transfer member, and that releases the molded product cured in a space surrounded by the mold member and the transfer member;
A mold, wherein a hard thin film layer having a Vickers hardness of 500 Hv or more is formed at a site where at least two members of the mold member, the transfer member, and the release member are in sliding contact.   2. The mold according to claim 1, wherein the hard thin film layer is formed by vacuum deposition of any one of DLC, TiCN, TiN, TiAlN, TiCrN, and CrN.   The mold according to claim 1 or 2, wherein the transfer member is formed by electroplating casting.

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