JPH0540967A - Disk substrate forming master disk - Google Patents

Abstract

(57) [Abstract] [Purpose] Disc molding master for manufacturing a stamper for molding a disc substrate, wherein the pit position can be corrected to the center of the guide groove interval when the disc substrate is molded The purpose is to provide a master. A disk substrate for manufacturing a stamper 9 for molding a disk substrate in which addresses and other information are recorded in pits 7 between adjacent guide grooves 6 formed in a concentric or spiral shape for a tracking guide. In the molding master 8, the cross-sectional shape of each of the guide grooves 6 and the pits 7 in the disk radial direction is formed into a symmetrical trapezoid, V-shape or U-shape, and between the center positions of the cross-sections of the adjacent guide grooves 6. The center position of the cross section of the pit 7 is displaced from the midpoint of the groove interval L to the center side P of the disk with respect to the groove interval L defined by.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk molding master for manufacturing a stamper for molding a disk substrate.

[0002]

2. Description of the Related Art Conventionally, a stamper for molding a disk substrate (for example, an optical disk substrate) is manufactured by a disk substrate molding master (hereinafter simply referred to as a master). Various methods of manufacturing the master are known, and as an example of the method, there is JP-A-2-149949. In the publication, a coupling plate and a photoresist are applied on a glass plate, the photoresist is selectively exposed by a laser beam, and further developed to obtain a master plate having guide grooves formed therein.

Thereafter, a metal film of nickel or the like is formed on the surface of the master, nickel is plated on the surface to a predetermined thickness, and the stamper is obtained by peeling the nickel plating. Then, this stamper is mounted on the mold of the injection molding apparatus to mold the disk substrate. It is described that a disk medium is completed by subjecting this disk substrate to film forming processing such as a protective film and a magnetic thin film. By this injection molding method, a large number of disk substrates can be repeatedly molded at low cost.

FIG. 2 is an explanatory view of a disk substrate molding process by a conventional injection molding method, and FIG. 2A is a sectional view of a main part immediately before injection in which a stamper is attached to a mold clamping cylinder,
FIG. 6B is a diagram showing the progress of the disk substrate molding process.

In FIG. 1 (a), reference numeral 1 is an injection molding apparatus, which comprises a mold clamping cylinder 11 and a mold 12, and a stamper 2 is mounted inside the mold 12 at a predetermined position and injected. It has a function of molding the molten resin 4 into a desired shape.

Reference numeral 3 denotes a heating cylinder for maintaining the melting resin 4 at a required melting temperature, and the tip of the heating cylinder is structured to be freely connectable to an injection port (a position corresponding to the center of the disk) (not shown) of the die 12. ing. Reference numeral 31 denotes a screw, which has a function of press-fitting the melted resin 4 into the mold 12 by rotationally driving it.

The progress of the diagram (b) is shown by a cross-sectional view of the stamper 2 and the direction of the initial inflow state of the press-fitted molten resin 4 by a group of small arrows. As shown in the sectional view of the stamper 2, the guide grooves 6 and the pits 7 are alternately arranged.
The cross-sectional shape of the pit 7 is formed in a symmetrical trapezoid, a V-shape, a U-shape, or the like. The center position of the cross section of the intervening pit 7 is formed so as to be the midpoint of the groove interval L with respect to the groove interval L defined between the center positions of the cross sections of the guide grooves 6 adjacent to each other.

The groove interval L is usually about 1.6 μm, and the injected molten resin 4 is usually filled at a speed of 10 μm / s. As shown in the figure, during the filling, the flow of the resin has a momentum, so that the resin does not sufficiently enter between the pit 7 and the guide groove 6 with a little diffusion. The molten resin that hits the side surface of the pit is bounced off at the side surface and launched.

In the course of the process, the repelled molten resin collides with the molten resin flowing from the center side of the disk and flows again along the stamper surface. At this time, a void is formed below the pit as shown in the figure. The temperature of the molten resin immediately before injection is 300 ° C or higher, but the surface temperature of the stamper is around 100 ° C, so the viscosity of the molten resin decreases when it flows on the surface of the stamper, and the temperature of the molten resin is lower than the pit. The voids do not collapse even though filling is in progress.

Although the mold is slightly opened by the impact at the time of injection, the mold is immediately clamped to the original position again by the mold clamping force. At this time, pressure R is applied in the plate thickness direction of the disk substrate, and the resin is pushed between the guide groove and the pit. However, since the resin does not wrap around the portion below the pit, voids remain. In the disk substrate 5 formed as shown in the course of the process, the center position of the pit cross section is not located at the midpoint of the groove interval L. That is, the illustrated dimension A ≠ B
Becomes

[0011]

Therefore, when a pit signal (address or other information) recorded in advance is read out by using the disk medium processed after molding in this way, the laser beam for reading is a groove. Since the tracking control is performed so as to seek the middle point of the interval L, when the pit is not located at the middle point of the groove interval L, a normal reflected light amount can be obtained from the reflected light of the laser beam corresponding to the shifted pit. It becomes impossible, and there is a drawback that a read error occurs in an address signal or the like.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a master for molding a disk substrate capable of correcting the pit position to the midpoint of the groove interval when molding the disk substrate.

[0013]

In order to achieve the above object, the present invention, as shown in FIG. 1, has a pit 7 between adjacent guide grooves 6 formed for tracking guides in a concentric or spiral shape. Stamper 9 for molding a disk substrate on which addresses and other information are recorded
In the master 8 for manufacturing, the guide grooves 6 and the pits 7 are formed in a symmetrical trapezoidal, V-shaped or U-shaped cross-sectional shape in the radial direction of the disk, and the central positions of the cross-sections of the adjacent guide grooves 6 are formed. The center position of the cross section of the pit 7 is displaced from the midpoint of the groove interval L to the center side P of the disk with respect to the groove interval L defined between them.

[0014]

When injection molding is performed using a stamper according to the conventional manufacturing method, the cross-sectional center position of the pit 7 which should be located at the midpoint of the groove interval L (where L = A + B) is as shown in FIG. 2B. It is formed so as to be displaced on the disk outer peripheral side Q so that the dimension A> B, and the ratio of the values of A and B becomes a constant value depending on the material of the melted resin, temperature, viscosity, injection pressure and the like. Therefore,
If the master 8 is formed in advance by shifting the cross-sectional center position of the pits 7 toward the center of the disk and the dimension C> D is established, the disk substrate formed by injection as a result has a groove interval L.
The center position of the cross section of the pit 7 can be corrected to the midpoint.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. In addition, in order to make the description of the configuration and the operation easy to understand, the same reference numerals are given to the same portions throughout the drawings, and the duplicated description will be omitted.

FIG. 1 is a partial sectional view showing an example of a disk substrate molding master according to the present invention. This cross section shows a disc cut in the radial direction. In the figure, reference numeral 8 denotes a disk substrate molding master (master), which has a glass plate 81 having a smooth surface, a coupling agent 82 applied to the surface of the glass plate 81, and a surface of the coupling agent 82. It is composed of the applied photoresist 83 and the photoresist.
The surface of 83 is selectively exposed by laser light and further developed to form guide grooves 6 and pits 7.

The cross-sectional shapes of the guide groove 6 and the pit 7 are formed in a symmetrical symmetrical trapezoidal shape, a V-shape or a U-shape as in the conventional case, but are defined between the center positions of the cross-sections of the adjacent guide grooves 6. The center position of the cross section of the pit 7 with respect to the groove interval L is formed so as to be displaced from the midpoint of the groove interval L to the disk center side P.

That is, the distance between the center position of the cross section of the guide groove 6 on the outer peripheral side Q of the disk and the center position of the cross section of the pit 7 is C, and the center position of the cross section of the guide groove 6 on the center side P of the disk and the pit 7. The distance from the center position of the cross section is set to D, and it is formed in advance so that C> D is set to a required ratio corresponding to the conventional actual result data.

Reference numeral 9 is a stamper manufactured by using the master 8 and is a metal film formed on the surface of the photoresist 83.
(For example, a nickel thin film) 91 and a nickel plating layer 92 having a predetermined thickness formed on the surface of the metal film 91. After the nickel plating layer 92 is completed, the stamper 9 is obtained by peeling from the master 8. Be done.

Since the laser beam for irradiating the surface of the photoresist 83 forms the guide grooves 6 and the pits 7 in a cross-sectional symmetrical shape, no special mask or the like is required, and the conventional irradiation method can be used.

The procedure for irradiating the master 8 with laser light is as follows: first writing the guide groove 6 and then writing the pit 7, and vice versa. You may write 7 at the same time.

When writing the guide groove 6 and the pit 7 at the same time,
The distance D between the guide groove 6 and the pit 7 is 1 / the distance L between the guide grooves.
When the distance L between the guide grooves is controlled to be a normal value while being set to a distance shorter than 2, and the distance D between the guide groove 6 and the pit 7 is set to a distance shorter than 1/2 of the distance L between the guide grooves. There is a case where the distance between the pit 7 and the adjacent pit 7 is written with a regular interval in this state.

[0023]

According to the present invention, a disc substrate molded using a stamper in which the center of the pit cross section is shifted from the midpoint of the groove spacing between the guide groove and the adjacent guide groove to the center of the disc, is transferred. The position of the pit is corrected to the midpoint of the groove interval, and there is an effect that molding can be performed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing an example of a disk substrate molding master according to the present invention.

FIG. 2 is an explanatory diagram of a molding process of a disk substrate by a conventional injection molding method.

[Explanation of symbols]

 6 Guide groove 7 Pit 8 Disc substrate molding master (master) 9 Stamper L Groove spacing P Disk center side

Claims (1)

[Claims] 1. A stamper for molding a disk substrate in which an address and other information are recorded in pits (7) between guide grooves (6) which are concentrically or spirally formed for a tracking guide and which are adjacent to each other. (9)
In the disk substrate molding master (8) for manufacturing, the cross-sectional shapes of the guide grooves (6) and the pits (7) in the disk radial direction are formed into a symmetrical trapezoid, a V-shape or a U-shape, respectively, and adjacent to each other. The center position of the cross section of the pit (7) is located from the midpoint of the groove interval L to the center side (P) of the disk with respect to the groove interval L defined between the center positions of the guide groove (6). A disc substrate molding master, which is formed by shifting.