JPS6284450A - Production of substrate for optical disk - Google Patents

Abstract

PURPOSE:To form a substrate for an additional writing type or rewriting type optical disk having pregrooves of different groove depths with high accuracy by coating 2 kinds of photoresists having different spectral sensitivities on a glass plate in two layers, exposing the same with laser beams of different irradiation energy densities and developing the photoresists. CONSTITUTION:The photoresist 2 having the low spectral sensitivity is coated on the glass plate 1 and after the solvent is evaporated, the photoresist 3 having the high spectral sensitivity is coated thereon as the 2nd layer. The photoresist 3 having the high spectral sensitivity is photodecomposed at J1 Joule/cm<2> irradiation energy density so that the developing depth is made constant. The photoresist 2 having the low spectral sensitivity is photodecomposed at J2 Joule/cm<2> irradiation energy density so that the developing depth is saturated. The laser beam is thereupon set at the intensity of J2 Joule/cm<2> in the recording bit parts and is set at the intensity of J1 Joule/cm<2> in the continuous groove parts in the stage of exposing the photoresists by using a laser beam 4. A stamper is thereafter manufactured and the pregrooves are transferred to the resin by an injection molding method, etc., by which the substrate for the optical disk is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a substrate for a write-once type, rewritable type optical disc.

[Summary of the invention]

In the method for forming pre-groups, the present invention involves applying two types of photoresists with different spectral sensitivities to a glass plate in two layers, exposing and developing them with laser beams with different irradiation energy densities. This makes it possible to manufacture substrates for write-once type and rewritable type optical disks with high precision having different pregroups.

[Conventional technology]

Currently, concentric or spiral grooves are formed in advance on optical discs as an effective method for controlling the recording position. This groove is called a pre-group, and the general &C-shaped pre-group is often used. The pre-group keel is not just a continuous groove,
Recording bits are formed in advance according to the sector format. The recording bit part and the continuous groove part have a depth ht-
In contrast, the recording pit portion is manufactured so that the depth dl is λ/4n, and the continuous groove portion is manufactured so that the depth dl is λ/8n.

Conventionally, the method of forming pre-groups with different depths is as follows:
A photoresist of 7kd+=λ/4* is coated on the glass original plate 1, and the depth of the fully exposed area is d1=λ/4n, depending on the laser beam irradiation energy density.

The exposure conditions and development conditions were selected so that the half-exposed area depth h's dlr =λ/8n.

[Problems and objects to be solved by the invention] However, with the above-mentioned conventional technology, it is difficult to maintain stable half-exposure conditions for a long time. This causes a decrease in O/NG during counting.

′+! Changes in the shape of the group cause a decrease in tracking accuracy, which has been a major problem in obtaining high-quality optical discs.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide mass-produced optical disc substrates having the same group shape.

[Means for solving problems]

A method for manufacturing an optical disc substrate according to the present invention.

In the resist master production process, a photoresist 2 with low spectral sensitivity is applied as the first layer of the glass plate IK to a predetermined thickness. Its genus is usually λ/8n. After prebaking if necessary, a second layer of high spectral sensitivity photoresist 3 is coated with VC to a predetermined thickness. Its thickness is usually λ/8n.

After prebaking, when forming a recording bit portion, exposure is performed by increasing the laser beam intensity to a high energy density. Further, when forming a continuous groove portion, exposure is performed at a laser beam intensity of 1 to low energy density. After that, development and post-bake are performed to complete the resist master. From this resist master,
An optical disk substrate is obtained by preparing a stamper and transferring it to a pregroup resin by injection molding, stamping, ultraviolet polymerization using 7 otobolimer, or the like.

[Effect]

According to the present invention, both recording bit portions and continuous groove portions having different depths can be obtained in a very stable and convex shape.

If the spectral sensitivities of the two types of photoresists are appropriately selected, the intensity of the laser beam can be increased! A pre-group having a depth of Koshin can be obtained in mass production without being affected by changes in temperature, environmental temperature, humidity, photoresist, etc.

[Appeasement example]

To specifically explain the present invention with reference to the drawings, FIG. 1 shows a resist master production process according to the present invention.

Coat a glass plate IVc (low spectral sensitivity) polished smooth to a thickness of about λ/8n using a 2% spinner. Individuals should compensate for the decrease due to baking. After the solvent is volatilized by pre-baking, a second layer of photoresist 31 with high spectral sensitivity is coated using a spinner so as to have a thickness of about λ/8n. In this case as well, the person in charge should compensate for the decrease due to baking. The development characteristics of the two types of photoresists used at this time, depending on the irradiation energy density, are shown in FIG. 2 (α). High spectral sensitivity photoresist 3 irradiation energy density hl Js joule
It is photodecomposed at a depth of L/cm", resulting in a development depth of /l".

The irradiation energy density of two photoresists with low spectral sensitivity is J! photodecomposition occurs at 3Δ−2, and the current depth is saturated. Therefore, when exposing using the laser beam 4 in FIG.
! Set the intensity to . Next, it is developed and used as a resist master.

Thereafter, a stamper is prepared, and the pregroup is transferred to a resin by injection molding or the like to obtain an optical disc substrate. According to the conventional method, a recording layer 9F having a depth of 174% is formed using a photoresist 5 having the development characteristics as shown in FIG. However, if a continuous groove with a depth of λ/an is formed with the irradiation energy density of J4 J41, it is extremely difficult to obtain a uniform and stable continuous groove depth.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to manufacture substrates for write-once and rewritable optical discs having pre-groups with different group depths with high precision.

[Brief explanation of drawings]

FIGS. 1(a) to 1(e) are process diagrams for producing a resist master, which is the main process of the method for producing an optical disc substrate of the present invention.
a) is a glass plate, d) is resist coating, (C) is pre-baking, ge) is exposure, and (g) is the process of applying fi. FIG. 2(a) is a development characteristic diagram of the photoresist used in FIG. 1. FIG. 2(b) is a development characteristic diagram of the photoresist used in the conventional resist master production process. 1...Glass plate 2...Low spectral sensitivity photoresist 3...
・High spectral sensitivity photoresist 4...Modulated laser beam 5...More than conventional photoresist

Claims (1)

[Claims] The resist master production process consists of applying photoresist to a glass plate, exposing it to a modulated laser beam, and developing it; the stamper production process consists of conductivity, electroforming, back polishing, inner and outer diameter processing; and resin molding. In the method for manufacturing an optical disc substrate, which includes a transfer process, the resist master production process includes applying a photoresist 2 with low spectral sensitivity to a predetermined thickness as the first layer on a glass plate, prebaking if necessary, and forming the second layer. A photoresist 3 with high spectral sensitivity is applied as an eye to a predetermined thickness, prebaked, exposed using a modulated laser beam 4 with different irradiation energy density, and developed to form group grooves with different depths. A method for manufacturing an optical disc substrate, which comprises producing a resist master.