JPH07176085A - Production of optical disk molded substrate excellent in transfer property - Google Patents

Abstract

PURPOSE:To obtain an optical disk substrate having excellent transfer property with small warpage by injection compression molding a polycarbonate resin under specified molding conditions. CONSTITUTION:A polycarbonate resin is subjected to injection compression molding with an injection molding machine under the conditions of 370-390 deg.C molding temp., 120-140 deg.C die temp., and 20-50 ton pressure to form a substrate. By this method, an optical disk substrate excellent in transfer property with little warpage cap be obtd. by using a transparent polycarbonate resin, and thereby, increase in the massproductivity and decrease in the cost are realized. Further, high-density input of picture images is possible and the recording amt. is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polycarbonate resin optical disk molded substrate by injection compression molding.

[0002]

2. Description of the Related Art Optical discs have been rapidly spreading since the market of compact discs (CDs) and laser discs (LDs) in the early 1980's. Nowadays, however, optical discs of CD size are comparable to those of LDs. Is desired to be recorded digitally, and various studies have been made on development of a thin and high-density one. (Lecture 17p-T-11 at "The Society of Applied Physics", Autumn 1992,
17p-T-13, lecture at "Applied Physics Society" in the spring of 1993, 29a-B-8, 29a-B-5, etc.) Conventionally, the 2P method, which is one of the transfer methods, has been used as a method for manufacturing a thin high-density disk. By applying or injecting a curable resin on a glass substrate or a resin plate, and stacking the masters on which the pits or grooves have been formed, and then curing the curable resin, or by the etching method, the pits or grooves on the substrate. Had formed. However, these methods cannot be said to be excellent in terms of mass productivity and cost.

Under such circumstances, as a manufacturing method excellent in mass productivity and cost, a method of obtaining a thin high-density disk molded substrate by injection molding or injection compression molding of a transparent thermoplastic resin has been strongly developed. Is desired.

[0004]

The object of the present invention is to obtain an optical disk molding substrate having excellent transferability and small warpage by injection compression molding using a transparent polycarbonate resin, which has hitherto not been obtained. To provide a molding method therefor.

[0005]

The gist of the present invention is to use a polycarbonate resin at a molding temperature of 370-39.
A method for producing an optical disk molded substrate having excellent transferability is characterized by performing injection compression molding under molding conditions of 0 ° C., mold temperature of 120 to 140 ° C., and mold clamping pressure of 20 to 50 tons.

Examples of the polycarbonate resin used in the present invention include those obtained from bisphenol A and phosgene, or bisphenol A and diphenyl carbonate.

In the present invention, the thickness of the optical disk molding substrate obtained is preferably 1.0 mm or less.
That is, “Optical Technology Contact” 23 , No. 7,198
As described in the equation (4) on page 451 of No. 5, coma aberration having a magnitude proportional to the plate thickness and the cube of the numerical aperture is generated on the inclined optical disk molding substrate. Therefore, the thickness is 1.
If it exceeds 0 mm, when an objective lens with a high numerical aperture is used to densify the optical disc, coma aberration becomes large, and as a result, crosstalk becomes large when the disc substrate is tilted, and at the same time, the disc from the disc becomes larger. Since the amount of returning light decreases, the S / N ratio deteriorates and the jitter increases too much, which is not preferable.

In the present invention, the optical disk substrate is molded by the injection compression molding method.
It is necessary that the molding temperature is 370 to 390 ° C, the mold temperature is 120 to 140 ° C, and the mold clamping pressure is 20 to 50 tons.

Molding temperature less than 370 ° C, mold temperature 120 ° C
When the mold clamping pressure is less than 20 tons or the mold clamping pressure is less than 20 tons, the transferability is deteriorated.
In particular, it is not preferable when obtaining a thin disk substrate having a thickness of 1 mm or less. If the molding temperature exceeds 390 ° C., the molding material is likely to decompose, which is not preferable. Also, the mold temperature is 140 ℃
If it exceeds, the warp of the molded substrate increases, which is not preferable. Further, when the mold clamping pressure exceeds 50 tons, the warp of the disk substrate becomes large, which is not preferable.

By performing injection compression molding under the above conditions,
The warp of the obtained optical disk molded substrate is as small as 200 μm or less, and the excellent transferability that the pits or grooves on the surface of the obtained optical disk molded substrate is 1.0 μm or less is obtained.

[0011]

The present invention will be described in more detail with reference to the following examples.

In the present invention, an injection molding machine (Dynamelter M-70A-DM manufactured by Meiki Seisakusho Co., Ltd.) is used.
Using a mold equipped with a stamper having pits and grooves having a pitch of 6 μm, an optical disk molding substrate having an outer diameter of 120 mm and a thickness of 0.6 or 1.2 mm was injection compression molded, and transferability and The warpage was evaluated.

As an evaluation method, a conductive film of about 20 n is formed on the surface of the optical disk substrate on which the pits or grooves are transferred.
Gold was sputtered to a thickness of m, and the pit or groove shape of the injection compression molded substrate was measured using a scanning tunneling microscope (hereinafter abbreviated as STM). The depth was obtained from these cross-sectional shapes, and the value obtained by dividing the depth by the pits or grooves of the stamper was defined as the transfer rate, which was used as the transferability evaluation standard.

With respect to the warp of the optical disk, the amount of vertical displacement of the outermost circumference with respect to the central portion of the disk substrate was measured as the warp amount of the substrate which was left at room temperature for one day or more after molding.

[Examples 1 to 10 and Comparative Examples 1 to 5] Polycarbonate resin AD9000TG manufactured by Teijin Chemicals Ltd. was used as the transparent thermoplastic resin, and the molding conditions of cylinder temperature, mold temperature and mold clamping pressure shown in Table 1 were used. Various optical disk molded substrates were molded by using to obtain substrates having the thicknesses shown in Table 1. Table 1 shows the evaluation results of transferability and warpage of this substrate.

[0016]

[Table 1]

[0017]

According to the molding method of the present invention, it is possible to obtain an optical disk molding substrate having excellent transferability and small warpage, which has not been obtained in the past, by using a transparent polycarbonate resin. The cost is very good, the transferability of the obtained disk-molded substrate is good, and the warp is small, which enables high-density image input, and its effect as a next-generation optical disk substrate. It is extremely large.

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Claims (1)

[Claims] 1. A polycarbonate resin is molded at a molding temperature of 37.
0-390 ° C, mold temperature 120-140 ° C, mold clamping pressure 20-5
A method of manufacturing an optical disk molded substrate having excellent transferability, characterized by performing injection compression molding under a molding condition of 0 ton.