JPH02150325A - Stamper for optical disk and optical disk base plate - Google Patents

Abstract

PURPOSE:To enable the base plate for optical disk excellent in the reliability of transferred address signal, while mold release is easy and moreover the deviation on the edge of an address pit does not occur by forming the cross sectional shape of the part corresponding to the address pit into the shape in which the corner of a trapezoid is chamfered. CONSTITUTION:The corner of the trapezoid of the part corresponding to an address pit, is chamfered. The R shape of the chamfered part 2 is preferably as large as possible, and by removing the corner perfectly, its top may be also rounded off. For instance, the sputtering in low vacuum condition or the etching in inorganic or organic acid is used. In such method, while the stamper 4 in which the corner of the trapezoid is chamfered, is used, if the base plate for the optical disk is molded by injection molding, the usual hooking action of the molded object 6 by the corner of the part corresponding to the pit does not occur, when the molded object 6 is released from the stamper 4, and then the transferring deviation does not occur easily and the reliability of the molded object is guaranteed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a stamper for molding an optical disc substrate, such as a magneto-optical disc or a DRAW disc, on which information can be recorded and reproduced by optical means, and a stamper for molding the optical disc substrate, such as a magneto-optical disc or a DRAW disc. - relates to an optical disc substrate molded using.

[Conventional technology]

Stampers conventionally used in the manufacture of optical disks and the like are formed by applying photoresist onto a glass plate, exposing it to laser light or the like, making the developed pattern surface electrically conductive, and performing electroforming or the like. At this time, the depth of the address pit of the optical disk to be transfer molded is set to λ/40 (
n: refractive index of the substrate, λ: reading laser wavelength), and in order to set the depth of the guide groove to λ/8n, the address pit corresponding portion 1 of the stamper 4 is etched as shown in FIG.
The cross-sectional shape of the guide groove corresponding portion 3 was formed into a round or bowl-like cross-sectional shape.

(Problem to be Solved by the Invention) However, when injection molding is performed using a conventional stamper, as shown in FIG. When molding, if the shrinkage speed is faster than the mold release speed, transfer misalignment occurs at the edges of the address pits.

This occurs because the address pit corresponding part 1 of the stamper 4 is higher than the guide groove corresponding part 3 and has corners 5, but if the address pit corresponding part 1 is lower than the guide groove corresponding part 3, It was impossible to form it into a bowl shape in order to maintain signal reliability.

(Means for Solving the Problems) According to the present invention, in a stamper for molding an optical disk substrate, which has address pits corresponding to address signals and guide grooves for tracking on the substrate, the cross-sectional shape of the portion corresponding to the address pit is trapezoidal. By chamfering the corners of the substrate, it is possible to mold an optical disk substrate that is easy to release from the mold, does not cause misalignment at the edges of the address pit, and has good reliability of transferred address signals. .

Normally, the part of the stamper that corresponds to the address pit has a trapezoid with a rounded top, as shown in Figure 3.
In the figure, the corners of the trapezoid of the address pit/corresponding portion 1 are chamfered. There is no particular restriction on the rounded shape of the chamfered portion, but the larger the radius, the better, and the corners may be completely rounded to give a rounded top.

Chamfering the corners of the trapezoid of the portion of the stamper corresponding to the address pits can be easily done by physical or chemical methods. Examples include sputtering under a low vacuum, etching in an inorganic acid or an organic acid, and the like.

When an optical disc substrate is molded by injection molding using a stamper with chamfered trapezoidal corners in the address pit corresponding area, as shown in Figure 2, when releasing the molded product from the stamper, it is difficult to remove the molded product from the stamper. 4th using stamper
As shown in the figure, the molded product is not caught by the corner portion 5 of the pit-corresponding portion, no transfer displacement of address pits occurs, and the reliability of the molded product is guaranteed.

〔Example) The present invention will be specifically explained below using Examples.

Example 1 External diameter: 137 mm, internal diameter: 35.4 ffu using conventional method
A Ni stamper with a thickness of 0.3 m + n was made, and it was placed in a vacuum asher device, and argon gas was applied at a flow rate of 7.
Introduced at 5 sccm, set the degree of vacuum to 3 Pa, and
Ashing was performed by DC sputtering at V and IA for about 30 minutes. As a result of observing the cross-sectional shape using a microscope, it was found that the corner of the obtained stamper corresponding to the bit was completely chamfered.

Next, an optical disc substrate was molded by injection molding using this stamper. The obtained substrate had almost no pit shift compared to conventional products.

Example 2 The DC sputtering in Example 1 was replaced with RF sputtering, the argon gas flow rate was 25 sec, and the degree of vacuum was I
The stamper was chamfered in the same manner as in Example 1, except that Pa and power were set to 200 W. As a result of observing the cross-sectional shape using a microscope, it was found that the corners of the stamper corresponding to the pits were completely chamfered. Further, the substrate molded using this stamper was free from bit misalignment.

Example 3 Using the conventional method, the outer diameter was 137 mm, the inner diameter was 35.4 mm,
A stamper made of Ni with a thickness of 0 or 1 mm was manufactured, and was immersed in a 6N nitric acid solution for approximately 30 seconds to chamfer the portion corresponding to the pit. As a result of observing the cross-sectional shape using a microscope, it was found that the corners of the stamper corresponding to the pits were completely chamfered. In addition, the substrate molded using this stamper is a substrate with no bit misalignment, and furthermore, it is 5i by vacuum evaporation.
I formed the n2 film, but no cracks were generated from the bit part.

(Effect of the invention) As explained above, by chamfering the address pit corresponding portion and injection molding using a lid stamper,
The lid makes it possible to mold an optical disk substrate without bit misalignment and without any trace of stamper contact again. Furthermore, the molded optical disk substrate has rounded corners at the bit part, so even when film is formed by sputtering, vacuum evaporation, etc., there is no cracking from the bit part, making it excellent. It became possible to manufacture optical discs with

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the stamper of the present invention and an optical disc substrate when molded using the same, and FIGS. 3 and 4 are sectional views of a conventional stamper and FIG. 3 is a cross-sectional view of the optical disc substrate at the time of mold release after molding. 1... Address pit compatible part 2... Chamfered part 3... Guide groove compatible part 4... Stamper 5... Corner of pit compatible part 6... Molded product

Claims (1)

[Claims] 1. In a stamper for molding an optical disk substrate, which has address pits corresponding to address signals and guide grooves for tracking on the substrate, the cross-sectional shape of the portion corresponding to the address pits is a trapezoid with chamfered corners. An optical disc stamper characterized by: 2. An optical disc substrate molded using the optical disc stamper according to claim 1.