JP3018470B2 - Manufacturing method of stamper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mold for manufacturing an optical disk for reproducing or recording information by using a laser beam.

[Conventional technology]

It has been considered that a stamper for manufacturing a conventional optical disc should have a uniform pit width over the entire surface from the inner periphery to the outer periphery of the preformat. In the case of a 2P molded substrate using a photopolymer, faithful transferability from a stamper was obtained using a low-viscosity photopolymer.
However, it has been found that in injection molding in which a substrate is molded using a linear polymer material and using high pressure, there is a difference in transferability between the inner periphery and the outer periphery of the substrate. In particular, when laser cutting is performed in the CAV mode, the pit length on the outer circumference is longer than that on the inner circumference. In this state, when a conventional laser is cut at a constant laser energy per unit length and a stamper is manufactured, a uniform pit width is formed from the inner periphery to the outer periphery. However, when injection molding is performed using this stamper, the outer peripheral pit of the molded substrate tends to generate a fold waveform (FIG. 3) in the signal characteristics using the pickup. This tendency is particularly remarkable when cutting is performed by increasing the laser power so as to increase the pit width in order to obtain a large VFO characteristic on the inner periphery of the substrate.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stamper in which signal characteristics of a molded substrate formed by injection molding described in the prior art, in particular, a fold waveform of an outer peripheral pit of the molded substrate hardly occurs, and a manufacturing method thereof.

[Means for solving the problem]

According to the present invention, an optical disc having a baking step of baking a resist applied on a master to form a coating film, and a cutting step of irradiating the coating film with a laser to form a latent image on the resist, A method of manufacturing a stamper for manufacturing, wherein the thermal history of the resist is changed between an inner circumference and an outer circumference in the baking step to change the sensitivity of the resist, and the laser per unit length of the master is used in the cutting step. A method of manufacturing a stamper characterized by making the energy uniform.

According to the method of the present invention, there is provided a stamper for manufacturing an optical disk, wherein a pit width for forming a preformat pit is smaller at an outer periphery than at an inner periphery. Can be obtained.

[Reference Example] A spin coater AZ1350 (positive resist made by Hoechst) is applied to a cleaned blue plate glass plate having an outer diameter of 200 mm and a thickness of 6 mm. It was a coating film. Then, using a two-beam laser cutting M / C (manufactured by Sony), the preformat of ISO 1024byte / Sector (ISO 917) in 1800RPM, CAV mode
1-2TYPEA) was cut into a plurality of sheets while changing the laser power from the inner circumference to the outer circumference to form a latent image on the resist. Thereafter, spin development was performed for 30 seconds using an AZ developer (a developer manufactured by Hoechst) to form a preformat pattern on the original plate.

Next, use a sputtering device to coat the pattern surface with nickel.
After the 500 ° conductor treatment, nickel was deposited to a thickness of about 300 μm by nickel electroforming. After that, the nickel surface was polished to a predetermined thickness, the stamper was peeled off from the glass plate,
After processing the inner and outer diameters, the resist on the surface was washed away to obtain a stamper capable of injection molding. As shown in Table 1, the mold temperature was 110
At ℃, a substrate is manufactured with an Techno-Plus injection molding machine, a magneto-optical recording layer and a protective layer with a reflectivity of 20% are formed by a sputtering device, and a preformatted pit signal is evaluated by our signal evaluation machine ODA-100. It was measured. As shown in Table 1, although the pit width was smaller on the outer periphery than on the inner periphery of the stamper, Sample E had a large inner periphery VFO characteristic and produced no fold waveform. (The values for the laser power at the inner circumference VFOγ = 30 are shown in FIG. 2.) [Example] Using a cleaned soda lime glass plate having an outer diameter of 200 mm and a thickness of 6 mm, applying AZ-1350 with a spin coater and changing the temperature distribution on the plate during baking with a hot plate.
It was a coating film of 00 °. The laser was cut so that the laser energy per unit length became uniform in the original plate, and the stamper was manufactured and evaluated by the same process as that of the above-mentioned reference example except for the above.
As shown in Table 2, the pit width was smaller on the outer circumference than on the inner circumference of the stamper, but Sample I had a large VFO characteristic and no fold waveform was generated.

The present invention is not limited to a continuous composite format stamper, and can be applied to all preformat stampers such as a CD, CDROM, CD / write once, and sampling servo format.

[Effects of the Invention] By using the stamper obtained by the present invention, it is possible to easily manufacture an optical disc having a large inner VFO characteristic of a reproduction signal of a preformat portion and a good signal characteristic without generating a fold waveform. An excellent effect is obtained.

[Brief description of the drawings]

 FIG. 1 is a schematic diagram of a pit width according to the present invention. FIG. 2 is a graph showing VFO characteristics with respect to laser power. FIG. 3 is a fold waveform diagram of a sector portion.

Claims (1)

(57) [Claims] 1. An optical disc manufacturing method comprising: a baking step of baking a resist applied on a master to form a coating film; and a cutting step of irradiating the coating film with a laser to form a latent image on the resist. A method of manufacturing a stamper for changing the sensitivity of the resist by changing the thermal history of the resist between the inner circumference and the outer circumference in the baking step, and changing the laser energy per unit length of the master in the cutting step. The method for manufacturing a stamper, wherein the stamper is made uniform.