JP2007280582A - Metallic mold for manufacturing optical recording medium substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the conventional problem of the durability of a metallic mold while reducing quality difference in a disk by disposing components having thermal conductivities different from each other and having a heat insulating properties inside the metallic mold thereby reducing difference between transfer properties at the inner and outer circumferential parts of the metallic mold. <P>SOLUTION: The metallic mold for forming an optical disk uses the components which are characterized in that between a stamper mounting member (1) for mounting a stamper and having a groove part to be a guide groove and/or an information pit part for recording information and a temperature controlling groove (2) for cooling, a material (3) having a thermal conductivity lower than that of the stamper mounting member (1) is provided, thereby the temperature controlling groove (2) for cooling is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a molding die for an optical recording medium substrate and an optical recording medium substrate molded using the same. In particular, the present invention has a groove depth variation formed by setting a stamper having a pit or groove uneven pattern formed on one side to form a cavity and injecting molding resin into the cavity. The present invention relates to a molding die that is capable of molding a highly accurate optical recording medium substrate that is reduced in comparison with a die and that has an excellent die cooling function.

  In recent years, optical recording media have become mainstream as large-capacity and high-speed memory media. For example, a read-only type (CD-ROM, DVD-ROM), a recordable write-once optical disc, a rewritable disc (CD-RW, CD-R, DVD ± R, DVD ± RW), etc. are generally known. Recently, however, there are two-layer DVD ± R, Blue-Ray Disc, HD, DVD, etc., which have a larger capacity.

  With regard to the recordable write-once optical disc and the rewritable disc, the writable speed has been steadily increasing in recent years, and the quality required for the optical recording medium substrate has become severe as the speed increases. As a material used for these optical recording media, a light transmissive resin (polycarbonate resin, acrylic resin, or the like) is used. Such a substrate is usually formed by an injection molding method or an injection compression molding method from the viewpoint of productivity.

  Specifically, it is manufactured by attaching a mold to an injection molding machine. In the mold, a stamper made of an annular metal thin plate is disposed in a cavity formed between a fixed mold and a movable mold, and a molten resin is injected into the cavity and compressed, thereby compressing the stamper. An optical recording medium to which a concavo-convex pattern composed of pits and grooves recorded on the recording medium is transferred is formed. The optical recording medium substrate molded as described above cools and solidifies the molten resin in the cavity. An optical recording medium gives a concavo-convex pattern to a light-transmitting resin or the like by transferring a fine concavo-convex pattern onto a resin and solidifying by cooling.

Examples of conventional techniques for reducing the variation in groove depth of an optical recording medium substrate (optical disk substrate) include the following.
Mold device for forming grooves, pit patterns, and other shapes on an optical recording medium substrate (optical disc substrate) suppresses the deformation of the cavity forming surface caused by the cooling passage without reducing the cooling capacity, and is highly accurate. In the mold apparatus, a plurality of annular cooling passages are formed concentrically on the bottom surface (back surface) of the mirror surface plate, and the entire surface is substantially spiral on the bottom surface of the mirror surface plate. The one which formed the cooling channel | path of the shape connected to one so that a shape might be made is mentioned. In these mold apparatuses, the cooling water flows down the cooling passage from the central part of the mold toward the outer peripheral part.

Generally, it is known that a heat insulating material is used for a mold for manufacturing an optical disk substrate. However, there are various places of use. For example, as a technique used between a stamper and a mold (mirror surface), an optical disk mold having a heat insulating layer and a diamond-like carbon film on the surface holding the stamper is used. Molding method (described in Patent Document 1), mold for optical disk substrate (described in Patent Document 2) provided with a low thermal conductive metal member on part of the surface of the mold cavity or on the back of the stamper, mold for molding optical disk substrate Optical disc molding die with high thermal insulation by roughening the surface of the heat insulating plate that does not contact the stamper or by inserting a foaming agent between the heat insulating plate and the mold core material (described in Patent Document 3) An optical disk injection mold in which the conductivity of the heat conduction portion of the stamper or the mold provided on the back surface thereof is changed between the outer peripheral portion to be weakly cooled and the inner peripheral portion to be strongly cooled (Patent Document 4) In addition, by placing a suction-type detachable insulation plate between the stamper support that receives the stamper and the stamper (detachment is performed off-line), the initial cooling of the stamper surface is delayed at the start of optical disk substrate injection molding. Optical disc injection molding die (described in Patent Documents 4 and 5), a fixed die having a heater located in the outer peripheral portion of the molding cavity and a temperature adjusting passage located in the inner peripheral portion, and an optical disc molding method using a movable die And an optical disk molding die apparatus used in this method (described in Patent Document 6), the surface of the metal die core member on the back side of the stamper is formed into a groove shape, and a ceramic heat insulating material is provided in the groove portion. Optical disk substrate molding die (described in Patent Document 7) whose peripheral and outer edge portions are made of metal to increase the strength of the side wall, and the initial cooling of the thermoplastic material during molding is delayed. Therefore, the heat insulating mold insert inserted between the stamper support and the stamper has an insulating mold structure for optical disk injection molding in which the density of the central region is lower than the density of the inserts of both surface regions (Patent Document) 8) are proposed.
Further, as a technique of using a heat insulating material for the stamper, a stamper substrate molding stamper in which the thermal expansion coefficient of a resin-based heat insulating material is adjusted to be substantially the same as that of a stamper or a mold, and an optical disk substrate When manufacturing a molding stamper, an optical disk substrate molding stamper cured by changing the temperature into a pre-cure after applying a heat-insulating material filled with a pigment and a post-cure after forming a metal layer, and a manufacturing method thereof (Patent Document 9 Description), a stamper in which a heat insulating material having a low thermal conductivity smaller than 94 W / m · K, such as polyimide, polyimide amide, ceramics, and bismuth, is provided on the inside and / or the back surface of the stamper, and a mold that supports the stamper Optical disc media manufacturing method and thin substrate molding stamper including specific combination with set temperature condition as content (described in Patent Document 10) Is disclosed.

Steel molds having a thermal conductivity of 20 W / m · ° C. or higher are generally used for optical disk substrate molding dies (for example, trade names: STAVAX and HPM38S). Since the mold is heated by a high temperature (about 340 ° C.) resin (usually polycarbonate), the disk is molded while circulating cooling water of 90 ° C. to 120 ° C. in the mold.
The polycarbonate resin flows from the inner periphery to the outer periphery of the disk. However, since the resin is cooled by the mold, the depth of the groove transferred from the stamper gradually decreases toward the outer periphery of the mold. For this reason, the recording characteristics change (deteriorate) in the outer peripheral portion as compared with the inner peripheral portion and the intermediate peripheral portion. In order to suppress the deterioration of the groove shape, it is better not to lower the resin temperature on the outer periphery. Specifically, there is a method of raising the temperature of the resin by raising the cooling water temperature. However, when the temperature is increased, the disk is likely to be deformed, so that the productivity tends to deteriorate, for example, the cooling time is extended.

  In addition, all of the prior arts described in these publications are provided with a separate heat insulating material layer on the back surface of the stamper material or the surface of the stamper support member, and between the grooves in the stamper material. The material or the pit itself is not provided with heat insulation.

  Although described in the above-mentioned patent documents, a method such as incorporating a heat insulating material between a part called a stamper and a stamper mounting surface (usually a mirror finish) of a mold, or a method of providing a heat insulating layer inside a stamper is mentioned. It has been. Although these methods improve the groove transferability, the following disadvantages also occur.

For example, when a heat insulating layer is provided inside the stamper, the stamper is deformed and the stamper is easily peeled off from the mold.
In addition, it takes a lot of stamper manufacturing steps, resulting in an increase in cost, and the strength of the heat insulating material is inferior to that of metal. There are adverse effects such as writing errors and reading errors that cause focusing errors.
Further, even when the heat insulating material is mounted between the stamper and the stamper mounting surface of the mold, there is a problem of shortening the service life due to wear or deformation of the heat insulating material which is basically inferior in strength and wear resistance.

JP 2005-014278 A JP 2004-195756 A JP 2004-181917 A JP 2004-181716 A JP 2002-331551 A JP 2002-192590 A JP 2001-260181 A Japanese Patent No. 3066254 JP 2002-184046 A Japanese Patent Laid-Open No. 2002-361689

  Therefore, in the present invention, by disposing heat-insulating parts having different thermal conductivities inside the mold, the difference in transferability between the inner and outer circumferences is reduced, and the quality difference in the disk is reduced. The aim is to improve the conventional durability problem.

That is, the above-described problem is (1) “a member (1) for mounting a stamper having a groove part and / or an information pit part as a guide groove for recording information in an optical disk molding die” of the present invention. The cooling temperature control groove (2) is formed between the cooling temperature control groove (2) and a material (3) having a lower thermal conductivity than the stamper mounting member (1). Mold using ",
(2) “Using the component characterized in that only the cooling temperature control groove in the region located on the outer peripheral portion of the stamper is formed of the cooling temperature control groove with a material (3) having low thermal conductivity. "Mold described in (1)",
(3) “The mold according to (1) or (2) above, wherein the heat-resistant temperature of the material (3) to be used is higher than the cooling water temperature” ,
(4) The thermal conductivity of the material (3) having a low thermal conductivity is 5 W / m · ° C. or less, according to any one of (1) to (3), Mold",
(5) "The mold according to any one of (1) to (4) above, wherein the thickness of the material (3) having low thermal conductivity is 1 mm or more",
(6) "The mold according to any one of (1) to (5) above, wherein polyimide or polyamideimide is used for the material (3) having low thermal conductivity",
(7) "Any of the above items (1) to (6), wherein the material (3) having a low thermal conductivity is fixed to the member (1) with a heat-resistant adhesive. `` The mold described in Crab '',
(8) Any of the items (1) to (6), wherein the material (3) having low thermal conductivity is fixed to the member (1) by screwing. This is achieved by the "die described in the above"

  As will be apparent from the following detailed and specific explanation, the present invention reduces the difference in transferability between the inner and outer circumferences by placing heat-insulating parts with different thermal conductivities in the mold. In addition, the present invention has an extremely excellent effect that it is possible to improve the conventional problem of deterioration in durability while reducing the quality difference in the disk.

The present invention is described in detail below.
In order to slow down the conduction of heat from the cooling temperature control groove (2) provided in the mold member (1) to which the stamper (5) of Example 1 of FIG. 1 is attached, the member (1) and the temperature control groove ( The temperature drop of the mold member (1) is delayed by providing the material (3) having a low thermal conductivity during 2).
Alternatively, as shown in FIG. 2, only the cooling temperature control groove (2) at the position corresponding to the outer peripheral portion of the molding cavity is formed with a material (3) having a low thermal conductivity, thereby forming the outer peripheral member (1). Slow down the temperature drop.

In addition, use of a material having a heat resistance temperature of the material (3) having a low heat conductivity higher than the cooling water temperature ensures durability, and the material (3) having a low heat conductivity has a heat conductivity of 5 W. / M · ° C. prevents a temperature drop due to heat conduction more effectively, or prevents the temperature drop by setting the thickness of the material (3) having a low heat conductivity to 1 mm or more.
More specifically, by using polyimide or polyamideimide for the material (3) having low thermal conductivity, transferability can be improved without deteriorating the durability of the stamper mounting surface.

  Refer to Fig. 1 and Fig. 2 using a heat-resistant adhesive for the method of fixing materials with low thermal conductivity. Refer to Fig. 3 and Fig. 4 using screws for fixing. In any case, the mounting position of (3) is rotated to prevent the position of the inlet and outlet of the cooling water from shifting.

Hereinafter, the present invention will be described more specifically with reference to examples.
As a method of manufacturing a component, a method in which a heat insulating material formed by machining is bonded and screwed. Alternatively, since there is a thermosetting resin as a resin suitable for the heat insulating material, a method of applying the uncured resin (liquid resin) to the inner surface of the mold, solidifying it in an oven, finishing it, and using it can be considered.
In this example, a method in which a resin was applied to the inner surface of the mold cooling groove and solidified was used. When a sufficient thickness cannot be ensured by a single application, the application and solidification can be repeated to increase the film thickness.
The groove depth of the molded substrate was measured and compared under the same molding conditions by changing the parts using a stamper having a pit as the ROM portion on the inner periphery and having grooves on the outer periphery from the middle periphery.

Using the molding die of the present invention provided with cooling water channels (temperature control grooves) shown in FIGS. 1 to 5, a substrate was injection compression molded using polycarbonate.
More specifically, after the mold temperature is set to about 70 ° C. to about 130 ° C., the movable side mold is moved to the fixed side mold provided with the stamper to perform the mold closing. A molten resin having a temperature of about 300 ° C. to about 395 ° C. is injected and injected into the cavity through the resin flow path of the sprue bush, and then the injected resin is pressurized (injection compression molding method). Further, during pressurization, the central portion is punched and formed into a donut shape, and the resin in the cavity is cooled by taking down, for example, hot water having an appropriate temperature as a temperature adjusting liquid into the temperature adjusting groove, and the disk is taken out.

Example 1 in graph 1 shows the results of measurement of the groove depth of a molded substrate molded with a mold using parts having the technical contents of claims 1, 3, 4, 5, 6, and 7 described in FIG. FIG. 2 shows the measurement results of the groove depth of the molded substrate molded with the mold using the parts having the technical contents of claim 2, 3, 4, 5, 6, 7 described in FIG. In Example 2, the groove depth of a molded plate formed by a mold using the unmeasured part shown in FIG.
The groove depth was measured using Biref126P (made by Dr. Schenk) using diffracted light.

In Example 1 (claims 1, 3, 4, 5, 6, and 7), the transferability was improved over the entire disk surface from the inner periphery to the outer periphery.
In Example 2 (claims 2, 3, 4, 5, 6, and 7), improvement in transferability was observed particularly at the outer periphery.
In the case where the difference between the inner circumference and the outer circumference is to be reduced, a more preferable result is obtained in which the heat conduction of the cooling pipe in the outer circumference portion as in Example 2 is deteriorated.

It is the figure which showed the cross section at the time of attaching a component with the adhesive material inside the member which attaches a material with low heat conductivity with the metal mold | die which uses the component in this invention to a stamper. It is the figure which showed the cross section at the time of attaching components with the adhesive material only to the outer peripheral part inside the member which attaches a material with low heat conductivity with the metal mold | die which uses the components in this invention to which a stamper is attached. It is sectional drawing of the metal mold | die of a prior art example. It is the figure which showed the cross section at the time of attaching a component with a fixing screw inside the member which attaches a material with low heat conductivity with the metal mold | die using the component in this invention to a stamper. It is the figure which showed the cross section at the time of attaching a component with a fixing screw only to the outer peripheral part inside the member which attaches a material with low heat conductivity with the metal mold | die using the component in this invention to which a stamper is attached. It is the figure which showed the measurement result of the groove depth of the shaping | molding board | substrate shape | molded with the metal mold | die which uses the components in this invention.

Explanation of symbols

1 Mold member 2 Temperature control groove 3 Low thermal conductivity material 4 Cooling water 5 Stamper 6 Fixing screw

Claims (8)

In a mold for optical disc molding, between a member (1) for attaching a stamper having a groove part and / or an information pit part as a guide groove for recording information, and a cooling temperature control groove (2), A mold using a component, wherein the cooling temperature control groove (2) is formed of a material (3) having a lower thermal conductivity than the stamper mounting member (1). 2. The component according to claim 1, wherein only the cooling temperature control groove in a region located on an outer peripheral portion of the stamper is formed with a cooling temperature control groove using a material having low thermal conductivity (3). Mold. The mold according to claim 1 or 2, wherein the heat-resistant temperature of the material (3) having a low thermal conductivity used is a material higher than the cooling water temperature. The metal mold according to any one of claims 1 to 3, wherein the material (3) having a low thermal conductivity has a thermal conductivity of 5 W / m · ° C or less. The mold according to any one of claims 1 to 4, wherein the material (3) having a low thermal conductivity has a thickness of 1 mm or more. The mold according to any one of claims 1 to 5, wherein polyimide or polyamideimide is used for the material (3) having low thermal conductivity. The mold according to any one of claims 1 to 6, wherein the material (3) having a low thermal conductivity is fixed to the member (1) with a heat-resistant adhesive. The mold according to any one of claims 1 to 6, wherein the material (3) having a low thermal conductivity is fixed to the member (1) by screwing.

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