JPH02283422A - Manufacture of mold for casting molding - Google Patents

Abstract

PURPOSE:To enhance the productivity of the title mold and reduce its manufacturing cost by bringing a flat plate that is softened by heating into contact with a matrix having a preformed pattern, and by transferring under pressure the preformed pattern of the matrix to the flat plate after heating the matrix up to a temperature at which the surface of the flat plate is softened. CONSTITUTION:After a matrix 1 having a preformed pattern and a mirror surface matrix 3 having a mirror surface have been mounted on a heat press 5, plate glass 2 is inserted between the matrix 1 and the mirror surface matrix 3. The plate glass 2 is then brought into contact with the matrix 1, and after the matrix 1 has been heated up to the degree of not lower than a temperature at which the surface of the plate glass 2 is softened, the preformed pattern of the matrix 1 is transferred under pressure to the plate glass 2. By this method, a mold for casting molding which has high transferability, can be manufactured in high productivity and at the reduced cost of production.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a cast molding mold used when manufacturing a substrate for an information recording medium by a cast molding method.

[Prior Art] Conventionally, substrates for optical recording media have irregularities such as guide grooves and information bits formed on their information recording surfaces. Methods for forming such a substrate include, if the substrate is made of thermoplastic resin, a method of transferring the guide grooves of the master using an injection method or a heat press method, or a method of forming a transparent resin plate made of thermosetting resin or thermoplastic resin. After applying a photocurable resin composition thereon, the master is placed in close contact with the transparent resin plate and radiation (ultraviolet rays, X-rays, etc.) is irradiated in a negative direction to cure the photocurable resin composition. A so-called 2P method is known in which a pattern on a master is transferred to a transparent resin plate.

However, thermoplastic resin substrates obtained by injection method or heat press method may cause warping or optical anisotropy of the substrate after molding due to residual stress and molecular orientation due to thermal history during molding. There are problems as a substrate for recording media. In addition, in the substrate obtained by the 2P method, unreacted polymerization initiators and monomers tend to remain in the resin after photocuring, and these often have an adverse effect on the optical recording layer of the recording medium.

Cast molding is known as a method for manufacturing substrates for optical recording media that does not cause these problems.

The conventional method for producing substrates for optical recording media using the cast molding method is to use a cast mold with a preformat pattern such as guide grooves and pits formed in an uneven shape on a substrate such as a glass plate or a metal plate. As a mirror mold, a smooth glass plate is placed facing each other via a spacer to form a cast molding device.

A substrate for an optical recording medium was obtained by pouring a resin or a prepolymer containing a solvent into this apparatus and curing it. The substrate for optical recording media obtained in this way does not have optical anisotropy or warpage because it applies almost no pressure during molding compared to the injection method, hot press method, or 2P method. It has the characteristic that it does not adversely affect the recording layer.

The conventional manufacturing method of the cast molding mold used in the above-mentioned cast molding method is to form a thin film of photoresist on a glass or metal base material, and then laser cut a guide groove for signal recording according to predetermined specifications. After etching the exposed glass or metal base with acid etc., the remaining resist is removed.
Or, after forming a thin film made of a material different from the base material on a base material, a thin film of photoresist is formed on this thin film, and the guide groove is laser cut, and the exposed thin film is used as a part of the base material. A method is known in which the resist is etched until the resist is etched, and the remaining resist is removed.

In general, cast molding requires a long time of 1 to 8 hours at a time because sufficient properties cannot be obtained by short molding. Therefore, in order to mass-produce substrates for information recording media at low cost, it is necessary to prepare a large number of inexpensive molds.

[Problem to be solved by the invention] However, in the conventional manufacturing method for cast molding molds, there are a process of forming a photoresist film on a base material, a process of laser cutting the resist, and an etching process. Since many precision steps are required, such as the step of removing the resist and the step of removing the resist, as well as complicated steps, the mass production of the mold is poor, and it is difficult to manufacture the mold at a low cost.

The present invention was made in order to improve the drawbacks of the conventional technology, and by adopting the hot press molding method as the method for manufacturing cast molding molds, mass production is facilitated and manufacturing costs are significantly reduced. The purpose is to provide an improved method.

[Means for Solving the Problems] That is, the present invention provides a method for manufacturing a cast molding mold used when manufacturing a substrate for an information recording medium by a cast molding method. A method for producing a cast molding mold, which comprises bringing a heat-softening flat plate into contact with the mother mold, heating the mother mold to a temperature at which the surface of the flat plate softens, and applying pressure to transfer the preformat pattern of the mother mold onto the flat plate. It is.

Next, the present invention will be explained in detail based on the drawings.

FIGS. 1(a) to 1(d) are process diagrams that best represent the characteristics of the method for manufacturing a cast molding mold of the present invention. First, in FIG. 1(a), after a matrix l having a preformat pattern and a mirror matrix 3 having a mirror surface are mounted on a heat press machine 5, a plate glass 2 is placed between the matrix l and the mirror matrix 3. insert. The matrix 1 and the mirror matrix 3 can withstand the softening temperature of glass,
A material with high thermal conductivity that has the durability required for hot press molding of glass, can quickly lower the temperature during molding, and has good mold releasability when releasing the mold is preferable. . Specific examples thereof include cemented carbide, mold steel, cast iron, and chrome steel. The preformat pattern can be formed on the matrix by directly etching the base material of the matrix described above, or by forming a thin film made of a material different from the base material on the base material of the matrix. There are two methods: a method of etching a preformat pattern on this thin film, and a method of electroforming a pattern formed on a glass substrate using photoresist. The material for the thin film is preferably a material that has good adhesion to the base material of the matrix, has good durability against hot press molding of glass, and has good mold releasability from glass. For example, TiN, Ti, Cr,
Examples include hard thin films of nitrides or carbides of metals such as Ta, B, and Si.

As the material of the plate glass 2, commercially available optical glass can be used, such as SF, BK, SK, LaK glass, etc., but preferably it is a material with a low melting point, which does not allow bubbles to enter during molding, and does not have the ability to fuse with the mold. The material is good.

The glass material is related to the material of the matrix, and it is difficult to specify it specifically, but low melting point glasses include PbO or S containing PbO.
Examples include lead glass such as F glass, and SK glass as a material with few pores and good mold releasability. The surface on which the preformat pattern is transferred to the plate glass is preferably a polished surface, and the surface roughness Rmax is preferably 0.5 m or less.

Next, in FIG. 1(b), the plate glass 3 is brought into contact with the matrix l, and after the matrix l is heated to a temperature above which the surface of the plate glass 3 softens, the preformat pattern of the matrix l is formed by applying pressure. Transfer to plate glass 3. The temperature profile during molding varies the maximum temperature from near the softening point of the glass to sp.
Set between +150°C and hold for 30 seconds to IO minutes. Further, the temperature increase rate is set to 10 to 100°C/min, and the temperature decrease rate is set to 2 to 50°C/win. However, if distortion remains in the formed sheet glass, the temperature drop profile is changed to match the glass material in order to remove the distortion. Also, the pressure during molding is 1 to 150 kg.
/cm2 is preferable.

Thereafter, as shown in FIG. 1(C), the plate glass 1 onto which the preformat pattern has been transferred is allowed to cool down to room temperature, and a casting mold 4 can be obtained.

In the above explanation, a case is shown in which plate glass is used as a heat-softening flat plate onto which a preformat pattern is transferred by a matrix. A thermoplastic resin having a high softening temperature such as resin can be used.

[Function] The method for manufacturing a cast molding mold according to the present invention includes placing a flat plate of glass or the like into a matrix having a preformat pattern;
By heating the mother mold to a temperature that softens the surface of a flat plate such as glass, applying pressure, and transferring the preformat pattern of the mother mold onto a flat plate such as glass, we can mass produce cast molds with good transferability. It has good properties and can be manufactured at significantly reduced manufacturing costs.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A mold for casting an optical card board was manufactured by the method shown in FIG. The maximum pressure of the hot press molding machine is 100 kg/
cm2 and a maximum temperature of 8008C was used. A mirror-polished cemented carbide is used for the mirror-surfaced mother mold side, and a TiN film with a thickness of Igm is formed on the mirror-polished cemented carbide on the side of the mother mold on which the preformat pattern is formed. A predetermined pattern is created using an etching device for 30 minutes.
A pre-format pattern was formed by trial etching up to 00 people. 5F-8 polished thickness 5■ in the cavity of the device where the mother mold is attached to the molding machine
Insert a plate glass and heat at a heating rate of 20°C/sin.
The temperature was raised to 30°C and maintained at a pressure of 80 kg/cm2 for 3 minutes.

After that, reduce the temperature at a rate of 5°C/win to 350°C, 2
The temperature was lowered to room temperature at 0°C/min, and the molded plate glass with the preformat pattern transferred thereto was taken out from the cavity.

Examples 2 and 3 Using plate glass made of the material shown in Table 1 below,
A cast molding mold was produced in the same manner as in Example 1 except that the preformat pattern was transferred under the molding conditions shown below.

Table 1 Defect rates of preformat patterns of cast molds obtained by molding plate crows obtained in Examples 1 to 3 above,
The line width accuracy and surface roughness of the pattern were evaluated. Table 2 shows the results and the characteristic values required of a mold when manufacturing an optical cart substrate by cast molding.

Table 2 (Note) The evaluation method is as follows.

(1) Pattern defect rate Calculate the area defect rate on the mold surface using an optical microscope.

(2) Pattern line l] Accuracy Based on microdimensional measurements using a scanning laser microscope.

(3) Surface roughness Rmax was calculated from the cross-sectional curve measured by a surface roughness measuring device (5E-30G manufactured by Koita Institute).

From the results in Table 2, it can be seen that the cast molding mold produced by the method of the present invention sufficiently satisfies the required characteristic values. The main effects of the present invention are significant improvements in mass productivity and manufacturing costs.

Conventionally, the production of cast molding molds required 5 to 10 steps, from inputting materials to completion of the mold, and took 1 to 3 days. However, according to the present invention, the mold can be manufactured in one step, and the period can be shortened to 1 to 2 hours. In addition, the manufacturing cost can now be reduced to about 1150 compared to the conventional method due to a significant reduction in the number of steps, material costs, auxiliary materials, equipment costs, etc.

"Effects of the Invention" As explained above, according to the method of the present invention, by adopting the hot press molding method for the manufacturing method of the casting mold,
It is possible to obtain molds for cast molding with good mass production and greatly reduced manufacturing costs.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) are process diagrams showing an example of the method for manufacturing a cast molding mold of the present invention. l...Material mold 2...Plate glass 3...Mirror surface matrix 4...Mold for cast molding 5...Heat press machine

Claims (1)

[Claims] In a method for manufacturing a cast molding mold used when manufacturing a substrate for an information recording medium by a cast molding method, a heat-softening flat plate is brought into contact with a mother mold having a preformat pattern, and the surface of the flat plate is After heating to a softening temperature,
A method for producing a cast molding mold, which comprises applying pressure to transfer a preformat pattern of a matrix onto a flat plate.