JPS63166506A - Multi-stage mold for cast molding - Google Patents

Abstract

PURPOSE:To obtain a number of optical disk base plates having a uniform quality, by regulating an area where spacer is brought into contact with a mold for cast molding and a space between the molds and using a multi-stage mold clamping by connecting a plurality of the molds. CONSTITUTION:As a material of a spacer 2, longitudinal elastic coefficient and thermal expansion coefficient thereof are 1.0-2.3 kg/mm<2> and 2X10<-3>-2X10<->4/ deg.C respectively to fix surely a mold 1 for cast molding and not to deform the mold 1 for cast molding due to an excessive pressure when being cured. To give a uniform heat to the mold 1 for cast molding and to obtain an optical disk base plate free of sink mark and having a uniform quality, a spacer 2 having such a size that the area contacting with the mold 1 for cast molding is 1-15% of the area of one side of the mold 1 for cast molding and the space 3 between the molds for cast molding is 50-150% based on the thickness of the mold 1 for cast molding, is used. By pouring a resin into each mold 1 for cast molding at the same time by using this multi-stage mold for cast molding, casted optical disk base plates having little unevenness between respective base plates and in one and the same base plate, and a high quality can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multistage mold for cast molding of optical disk substrates.

More specifically, an optical disc substrate with a signal recording guide groove or a mirror surface has no cracks, the quality is uniform between the optical disc JJ boards cast at the same time, and there is no sink mark and high precision even within the same optical disc board. (This relates to a multi-stage mold for economically and easily casting a large number of sheets at the same time.

[Prior art]

Conventionally, in order to cast the optical disc M The methods used were to use a single cast mold to perform individual cast molding, or to simply knead a large number of these cast molds as they were and cast them simultaneously.

The method of casting individual cast molding molds requires curing equipment corresponding to each cast mold, and also requires the same curing conditions for each finished optical disk substrate. Since it is difficult to measure and is slightly different, it has the drawback of causing variations in dimensional accuracy and product quality.

In addition, the method of stacking many pieces and casting many pieces at the same time has the advantage of requiring less equipment for curing. In the past, the thermal history during curing differed, which caused local quality changes even within the same optical disc substrate and caused frequent sink marks.

[Purpose of the Invention] The present invention was developed as a result of intensive research into a method for improving dimensional accuracy and achieving uniform quality between simultaneously cast-molded optical disk substrates. By using a spacer with a coefficient within a certain range, regulating the contact area and gap between the spacer and the core mold, and using a multi-stage mold in which many molds for cast molding are fastened at the same time, it has excellent and uniform quality. The purpose is to obtain a large number of optical disk substrates at the same time.

[Structure of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of a multi-stage mold for cast molding. First, place the spacer 2 on the dot 8, and place the mold 1 for cast molding on it R-1! Ru. Regarding the material of spacer 2,
It has been found that the modulus of longitudinal elasticity and the coefficient of thermal expansion play a large role in firmly fixing the casting mold 1 and preventing the casting mold 1 from deforming due to excessive pressure applied during curing.

Among these, the longitudinal elastic modulus is 1.0 to 2.3 kx / 01
111”, and the coefficient of thermal expansion is 2X10~6~2Xl
Preferably O-'/”C, longitudinal elastic modulus 1.0 k
If the material is less than g/tya', the strain of the spacer 2 due to the fastening pressure will be large, making it impossible to securely fix the casting mold l, and the dimensional accuracy of the product will drop significantly. In addition, if the material has a longitudinal elastic modulus of 2.3 kg/U" or more, the spacer 2 will not be distorted when the fastening pressure is applied, resulting in an excessive reaction force being applied to the cast mold l. l causes deformation and the dimensional accuracy of the product decreases.Furthermore, +A with a thermal expansion coefficient of 2 x 10~"/"C or more
In the case of hardening, the cast molding mold 1 expands due to the temperature rise during curing, but it cannot follow this change, and the spacers 4) and -2 themselves do not expand due to heat, causing misalignment and causing the product to deteriorate. Dimensional accuracy decreases.

In addition, in the case of a material with a thermal tensile coefficient of 2 X l O'4/''C or more, the temperature rise during curing causes the spacer 2 itself to undergo significant deformation due to thermal expansion, causing the cast mold 1 to be tightened with excessive force. As a result, the casting mold 1 is deformed and the dimensional accuracy of the product is reduced.

Next, the spacer 2 applies uniform heat to the cast molding mold 1, and in order to obtain a sink-free optical disc substrate of uniform quality, the spacer 2 has an area that is in contact with the cast molding mold I. It occupies l-15% of the area of one side, and the gap 3 between the cast molding molds is 50 to 15% of the thickness of the cast molding mold l.
Use a spacer with a size that makes it 0%.

If the area in contact with the cast mold 1 is less than 1% of the area of one side of the cast mold 1, the cast mold 1 cannot be fixed and held, and the product may deteriorate. Dimensional accuracy decreases. In addition, if it is 15% or more, the number of spacers 2 increases or the size increases, so the hot air that hits the spacers 2 generates turbulence in that part, and heat is evenly transferred to the cast mold 1. This can lead to the occurrence of heat and variations in product quality. Furthermore, if the spacer 2 is less than 50% of the thickness of the cast mold 1, the distance between the cast molds 1 becomes narrower, and heating occurs due to the curing that flows between the cast molds 1. The flow rate of the air increases and the temperature becomes lower than the predetermined temperature for curing, making it impossible to obtain a cured product sufficient for use as an optical disc substrate. In addition, the flow path of the heated air suddenly narrows on the upwind side between the cast molds l, and the flow of the heated air that hits the cast mold l becomes turbulent. , local temperature non-uniformity occurs within the casting mold l, and the quality of the product also becomes non-uniform. In addition, if the spacer 2 is 150% or more of the thickness of the cast molding mold l, the gap between the cast molding molds l is too wide, and the heated air flow that hits the spacer 2 Disturbances in the casting mold l
This results in disturbing the flow of heated air between the
causing local temperature non-uniformity in the casting mold 1;
The crystal quality of the product also becomes non-uniform.

The material used for this cast molding mold is one that transmits sufficient heat to the resin injected into the cavity 5 for curing, prevents the occurrence of sink marks, and improves the quality of the product. We have found that thermal conductivity and thermoelastic modulus play a major role in making the molding uniform and improving the dimensional accuracy of the product after molding. Of these, thermal conductivity is 0.001
= 1.05 cal/C-・S・℃ The thermal elastic modulus is 2.
The preferred range is OX 10 to 9.0×10” dyne/c.

As for the casting method using this multistage mold for cast molding, as long as the resin is injected into each cast mold l at the same time, there is no particular problem in how the cast mold l is installed. Possible methods include a method in which the mold 1 for molding is installed vertically, a method in which the mold 1 for cast molding is installed horizontally, and the like.

〔Effect of the invention〕

According to the present invention, almost no sink marks are observed during molding, and the characteristics include birefringence of less than Ions, glass transition temperature (Tg) of 130°C or more, and variation within 5°C.
In terms of accuracy, we can produce a large number of high quality and highly uniform optical disc casting substrates at the same time, with variations in board thickness of 0.03 m or less, very little variation between each board and within the same board. It is an excellent multi-stage mold for manufacturing industrial optical disc casting substrates, as it can produce a large number of discs at an excellent cost.

4. Brief Description of the Drawings FIG. 1 is a diagram showing an example of a multistage mold for cast molding of optical discs according to the present invention.

The perspective view is a diagram showing the overall outline, and the Δ-A' sectional view is a vertical sectional view along the Δ-A' line of the perspective view.

The B-4 sectional view is a lateral cross-sectional view taken along line B-4 in the AN sectional view.

Patent applicant: Sumitomo Bakelite Co., Ltd.
No change in content) Figure 1 Figure 2 (Longitudinal cross-sectional view) Figure 3 (Kan WI side view) Houkiodorimen procedure amendment (method) April 24, 1988

Claims (1)

[Claims] In multi-stage cast molding of optical disk substrates, the cast mold has a longitudinal elastic modulus of 1.0 to 2.3 x 10^3 kg/mm^.
2 and the coefficient of thermal expansion is 2×10^-^6 to 2×10
A spacer consisting of ^-^4/°C is used, and the area in contact with the spacer and the cast molding mold accounts for 1 to 15% of the area of one side of the cast molding mold, and A multi-stage mold for cast molding of an optical disk substrate, characterized in that the gap formed by the spacer and the spacer is 50 to 150% of the thickness of each mold.