JP6678345B2 - Convex stamper and molding method using the same - Google Patents

Description

  The present invention relates to a stamper used in an injection molding device.

  In a molding apparatus for molding a molded article by injecting a resin material into a cavity formed by a first mold and a second mold that can be opened in a thickness direction of the molded article to be molded, the surface of the molded article has irregularities. Is mounted on the second mold, and the irregularities of the stamper are transferred to the resin material injected into the cavity. Specific examples of the molded article include a light guide plate on which irregularities of a prism are formed, and an optical disk on which irregularities on which information is recorded are formed.

  Patent Document 1 discloses an optical disk molding device. A general stamper forms a thick Ni film having a thickness equal to or greater than the finished thickness of the molded product on the surface of the mold master by electroforming, and after machining the mold, releases the mold from the mold master. A stamper to be nested in the mold has been created.

JP-A-10-302328

  This stamper is manufactured in the same manner as the stamper used for manufacturing the light guide plate. FIGS. 8A to 8D show a general manufacturing process of the stamper 1 used for producing the light guide plate.

  FIG. 8A shows a cross section of the mold master 5. Fine irregularities (not shown) are formed on the inner surface 6 of the concave portion of the mold master 5.

  In FIG. 8B, a thick electrodeposited layer 23 of a Ni film is formed on the surface of the mold master 5 by electroforming. When the finished thickness of the molded product is 10 mm, it is necessary to form the electrodeposited layer 23 with a thickness of about 12 mm or more, and the electroforming process of this thick wall requires a long time of about 120 days. I need.

  In FIG. 8C, only the electrodeposition layer 23 on the upper surface 5A of the mold master 5 is removed by machining.

  In FIG. 8D, the mass of the thick electrodeposition layer 23 remaining in the concave portion 6 of the mold master 5 is released from the mold master 5 to complete the stamper 1B.

  FIG. 9 shows a molding apparatus in which the stamper 1B is set in the second mold 12.

  A cavity 13 is formed between the first mold 11 and the second mold 12. FIG. 10 shows a rough appearance of a molded article 17 obtained by operating this molding apparatus. The molded product 17 of the light guide plate has a hat-shaped convex shape in which the center protrudes from the outer periphery, and minute irregularities (not shown) for a prism are transferred to the inner surface 17A.

  However, when the molding operation is repeated for about 30,000 shots, powder which seems to be generated due to friction at the contact surface between the stamper 1B and the second mold 12 moves between the stamper 1B and the second mold 12. When the molding pressure is applied to the stamper 1B while the powder is sandwiched between the stamper 1B and the second mold 12, the stamper 1B partially swells, and a convex shape called a bump is formed on the stamper 1B. Is generated, and a molding defect in which the convex shape is transferred to the molded product 17 occurs. Therefore, the stamper 1B is required for every predetermined number of moldings.

  An object of the present invention is to provide a stamper which can be produced in a short time without requiring a thick electroforming process and has a long life.

  The convex stamper according to the present invention is provided with a heat conductive core having a shape in which the center protrudes from the outer periphery, and an electrodeposition layer having an uneven surface formed on the surface and disposed on the surface of the core. Is fixed to the core.

  Further, the molding method of the present invention is characterized in that a resin material is injected into a cavity formed by a first mold and a second mold that can be opened in a thickness direction of a molded product to be molded. An electrodeposition layer in which a concave / convex shape to be transferred is formed and the outer periphery is fixed to a lower portion of the core is disposed on a surface of the heat conductive core having a shape in which the center protrudes from the outer periphery on the first mold side. A convex stamper is mounted on the second mold, the first mold and the second mold are closed, and the convex stamper is inserted into the cavity. During the period from injecting the molten resin material between the electrodeposition layers and increasing the internal pressure of the cavity, the heat of the resin material causes the electrodeposition layer to expand and the core and the electrodeposition layer to expand. A gap is generated between the layers, and the resin material is injected to increase the internal pressure of the cavity. Between the heat of the resin material becomes smaller pressed by the gap the electrodeposited layer by the resin material during the injection, characterized in that the dissipating through the core.

  According to this configuration, since the convex stamper of the present invention has a two-layer structure of the core and the electrodeposition layer, the electrodeposition layer can be made thinner, and compared with a conventional stamper that requires thick electroforming. And can be created in a short time.

  Further, the outer periphery of the electrodeposition layer is connected to a lower portion of the core. In the initial stage of injection until the internal pressure of the cavity of the molding device becomes high, the electrodeposited layer expands due to the heat of the resin material, and a gap is generated between the core and the electrodeposited layer. Since this gap acts as a heat insulating layer, the temperature drop of the resin material is reduced, and the resin material quickly spreads to the end of the cavity.

  In the latter stage of the injection in which the internal pressure of the resin material in the cavity is increased, the electrodeposition layer is pressed by the resin material being injected, the gap is reduced, and the heat of the resin material passes through the core. The heat is dissipated, and the irregularities recorded on the electrodeposited layer can be accurately transferred, and the transfer rate is improved.

(A) Perspective view and (b) sectional view of a stamper according to an embodiment of the present invention. (A) A bottom view of the stamper and (b) a bottom view of a stamper of another embodiment. (A)-(f) Manufacturing process diagram of the stamper (A) (b) Enlarged view of main parts Sectional view of a molding machine equipped with the stamper (A)-(c) Molding process diagram of molding device (A) An enlarged sectional view showing a transfer state of an example and (b) an enlarged sectional view showing a transfer state of a comparative example. (A) to (d) Manufacturing process diagrams of a conventional stamper Sectional view of a molding device equipped with a conventional stamper Perspective view of molded product

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1)
1A and 1B show a stamper 1 according to the present invention. Here, a stamper used to create the convex light guide plate shown in FIG. 10 is shown. One example of the optical component is a light guide plate.

  The electrodeposition layer 3 is disposed on the surface of the core 2, and the entire periphery of the end of the electrodeposition layer 3 is connected to the core 2 at the bottom as shown in FIG. I have. The core 2 is made of, for example, a steel material, and is, for example, stainless steel. The electrodeposition layer 3 is, for example, a Ni film. The electrodeposition layer 3 is as thin as about 0.5 to 2.0 mm. As a specific example of the connection and fixing between the electrodeposition layer 3 and the core 2, welding can be given. Reference numeral 4 in FIG. 1B and FIG. 2A indicates a joint between the electrodeposition layer 3 and the core 2.

  FIGS. 3A to 3F show a manufacturing process of the stamper 1.

  FIG. 3A shows a cross section of the mold master 5. The material of the mold master 5 is a steel material or an acrylic resin (PMMA or the like). Fine irregularities (not shown) are formed on the inner surface of the concave portion 6 of the mold master 5. The fine irregularities have, for example, a pitch of 0.07 mm and a depth of 0.007 mm.

  In FIG. 3B, a 1.1 mm thin electrodeposited layer 3A is formed on the surface of the mold master 5 by electroforming when the material of the mold master 5 is steel. When the material of the mold master 5 is made of an acrylic resin, the electrodeposition layer 3 is formed by electroless plating.

  In FIG. 3C, first, a part of the electrodeposited layer 3A formed on the upper surface 5A of the mold master 5 and the concave portion 6 is removed and machined to a thickness of 1.0 mm to form an electrodeposited layer 3B. I do. Further, the core 2 is inserted into the concave portion 6, and the core 2 is pressed against the inner electrodeposition layer 3B as shown in FIG. Then, a groove 8 is formed at the boundary 7 between the bottom surface 2A of the core 2 and the electrodeposition layer 3B. FIG. 4A shows an enlarged view.

  In FIG. 3E, the entire periphery of the electrodeposition layer 3 is welded to the core 2 at the groove 8 at the joint 4 to remove the electrodeposition layer 3B on the upper surface 2A of the core 2. FIG. 4B shows an enlarged view.

  In FIG. 3F, the electrodeposited layer 3B remaining on the upper surface 5A of the mold master 5 is removed, and the stamper 1 is released from the recess 6 of the mold master 5.

  The stamper 1 is mounted on a second mold 12 of a molding apparatus 10 including a first mold 11 and a second mold 12 as shown in FIG. FIG. 6A shows a state before the resin material 15 is injected into the cavity 13. Here, a sprue 14 for putting a resin material 15 in the center of the cavity 13 is formed in the first mold 11.

  As shown in FIG. 6B, during the period from the start of the injection of the resin material 15 at 270 to 300 ° C. from the sprue 14 of the first mold 11 into the cavity 13 until the internal pressure of the cavity 13 increases. When the hot resin material 15 contacts the electrodeposited layer 3 of the stamper 1, the electrodeposited layer 3 expands.

  In this embodiment, since the outer periphery of the electrodeposition layer 3 is fixedly connected to the core 2, a gap 16 is generated between the electrodeposition layer 3 and the core 2 when the electrodeposition layer 3 expands.

  Then, when the internal pressure of the cavity 13 increases to 50 MPa to 1000 MPa as approaching the latter stage of the injection, the thickness of the gap 16 decreases due to the pressure of the resin material 15, and finally, as shown in FIG. As described above, the entire electrodeposition layer 3 is in close contact with the core 2. As a result, the heat of the resin material 15 is radiated to the core 2 to lower the temperature. The molded article 17 can be obtained by opening the mold after the resin material 15 is solidified.

  In this molding step, the electrodeposition layer 3 expands immediately after the injection of the resin material 15 is started to form a gap 16, so that the friction between the stamper 1 and the second mold 12 generated by the injection of the resin material 15 is caused. Even when the molding operation is repeated about 30,000 shots, powder generated due to friction at the contact surface between the stamper 1 and the second mold 12 is generated using the conventional stamper 1B. And the molding operation can be repeatedly performed over a long period of time. Therefore, the single stamper 1 can be used repeatedly over a long period of time, and the number of times of replacement of the stamper 1 can be reduced.

  Further, since the thickness of the electrodeposited layer 3 at the time of forming the stamper 1 is as thin as about 1 mm, the electrodeposited layer 3 is formed in a shorter time as compared with the conventional one requiring the formation of the thick electrodeposited layer 23. it can.

  In addition, since the gap 16 generated during the injection of the molten resin acts as a heat insulating layer, the heat radiation of the heat of the resin material 15 transmitted to the core 2 is reduced. As a result, the resin material 15 having a small temperature drop spreads rapidly toward the end of the cavity 13 while maintaining the high temperature, and the resin internal pressure becomes high at a later stage of the injection of the resin material 15 so that the electrodeposition layer 3 is increased. Closely adheres to the core 2, and the minute irregularities formed on the surface of the electrodeposition layer 3 accurately contact the molded article 17 being formed. In this state, the heat of the resin material 15 is transferred through the electrodeposition layer 3. The heat is quickly radiated to the core 2 and the temperature of the resin material 15 is rapidly lowered and hardened.

  FIG. 7A shows the transfer result of the example. The prism 18 having minute irregularities could be accurately transferred to the obtained molded article 17. Here, one angle of the prism 18 was 50 ° and the other angle was 80 °. The incident light P1 from the end face 17B of the molded product 17 is guided inside the molded product 17, reflected by the prism 18, and emitted light P2 is emitted from the outer peripheral surface 17C of the molded product 17.

  FIG. 7B shows a transfer state of the comparative example. This comparative example shows a transfer result when heat is radiated to the core 2 immediately after the start of injection of the resin material, and the transfer state of the corners 19 and 20 to be transferred at 50 ° and 80 ° shown in the drawing is a solid line. As shown by the corners 19B and 20B shown in FIG. When such transfer failure occurs, normal emission light P2 from the outer peripheral surface 17C of the molded product 17 cannot be expected.

  In the above embodiment, the entire circumference of the electrodeposition layer 3 is fixed to the core 2 as shown in FIG. 2A, but a plurality of locations on the outer circumference of the electrodeposition layer 3 are fixed as shown in FIG. Similar effects can be expected by connecting and fixing the lower part of the core 2 at a uniform pitch, for example, at the bottom.

  In the above-described embodiment, the entire circumference of the electrodeposition layer 3 is fixed to the bottom of the lower part of the core 2 by welding as shown in FIG. 2 (a). The same effect can be expected even if it is fixed by welding as shown in FIG.

  In each of the above embodiments, the electrodeposition layer 3 and the core 2 are connected and fixed at the joint 4 by welding. However, the electrodeposition layer 3 and the core 2 are bonded by electrodeposition, or the electrodeposition layer 3 and the core 2 are connected to each other. Alternatively, the electrodeposition layer 3 and the core 2 may be connected and fixed by bonding with an adhesive to the core 2 or screwing the electrodeposition layer 3 to the core 2 with a screw.

  The core 2 of the above embodiment has a single convex shape in which the surface of the core 2 on the side of the first mold 11 gradually increases from the outer periphery toward the center, but has a plurality of convex portions. The same applies to a convex shape having a single or a plurality of convex portions and a flat surface in a part thereof.

  The present invention contributes to the high performance of a molding apparatus that needs to transfer a fine uneven shape with high accuracy.

REFERENCE SIGNS LIST 1 stamper 2 core 3 electrodeposition layer 4 bonding portion 5 mold master 6 recess of mold master 8 groove 10 forming device 11 first mold 12 second mold 13 cavity 14 sprue 15 resin material 16 gap 17 molded product 17A Inner surface of molded product 17B End surface of molded product 17C Outer peripheral surface of molded product 18 Prism P1 Incident light P2 Emitted light

Claims (5)

A heat conductive core whose center is protruded from the outer periphery,
An electrodeposition layer disposed on the surface of the core, the surface having an uneven shape formed thereon, and the outer periphery of the electrodeposition layer is fixed to the core;
Convex stamper. The core is made of steel, and the electrodeposition layer is made of Ni;
The convex stamper according to claim 1. The entire circumference or a plurality of locations of the electrodeposition layer is fixed to the lower portion of the core,
The convex stamper according to claim 1. When a resin material is injected into a cavity formed by a first mold and a second mold that can be opened in the thickness direction of a molded product to be molded,
An electrodeposition layer in which a concave / convex shape to be transferred was formed and the outer periphery was fixed to a lower portion of the core was disposed on the surface of the heat conductive core having a shape in which the center protruded from the outer periphery on the first mold side. Attach a convex stamper to the second mold,
Closing the first mold and the second mold, inserting the convex stamper into the cavity,
During a period until the internal pressure of the cavity is increased by injecting the melted resin material between the concave portion of the first mold and the electrodeposited layer of the convex stamper, the heat of the resin material increases The adhesion layer expands to generate a gap between the core and the electrodeposition layer,
During the period when the internal pressure of the cavity is increased by injecting the resin material, the electrodeposition layer is pressed by the resin material during injection, the gap is reduced, and the heat of the resin material is reduced by the core. To dissipate heat,
Molding method.   In a molding apparatus for injecting a resin material into a cavity formed by a first mold and a second mold that can be opened in a thickness direction of a molded product to be molded, the second mold is charged. A molding apparatus equipped with the stamper according to item 1.

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