JP3079661B2 - Master for disk substrate molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a stamper for forming a disk substrate (for example, an optical disk substrate) is manufactured by a master for forming a disk substrate (hereinafter simply referred to as a master). Various methods for producing the master are known, and an example of the method is disclosed in Japanese Patent Application Laid-Open No. 2-149949. In the publication, a coupling agent and a photoresist are applied on a glass disk, the photoresist is selectively exposed by a laser beam, and further developed to obtain an original disk on which a guide groove is formed.

After that, a metal film such as nickel is formed on the surface of the master, and nickel plating is formed on the surface to a predetermined thickness, and then the stamper is obtained by removing the nickel plating. Then, the stamper is mounted on a mold of an injection molding apparatus to form a disk substrate. It is described that a disk medium is completed by forming a film of a protective film, a magnetic thin film or the like on the disk substrate. 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 molding process of a disk substrate by a conventional injection molding method. FIG. 2 (a) is a sectional view of a main part immediately before injection with a stamper mounted on a mold clamping cylinder.
(B) is a diagram showing the progress of the forming process of the disk substrate.

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

Reference numeral 3 denotes a heating cylinder for maintaining the molten resin 4 at a required melting temperature. The heating cylinder 3 has a structure which can be freely connected to an injection port (not shown) of the mold 12 (a position corresponding to the center of the disk). ing. Reference numeral 31 denotes a screw, which has a function of press-fitting the melted resin 4 into the mold 12 by being rotationally driven.

[0007] The progress of the figure (b) shows a sectional view of the stamper 2 and the direction of the initial inflow state of the melted resin 4 that has been press-fitted, 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 section of the pit 7 is formed in a symmetric trapezoidal shape, a V shape, a U shape, or the like. The center position of the cross section of the interposed pit 7 is formed at 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 drawing, during the filling, the flow of the resin has a momentum, so that the resin does not sufficiently enter the space between the pit 7 and the guide groove 6 with a slight degree of diffusion. During the process, the melted resin that has hit the side surface of the pit is bounced off the side surface and launched.

The melted resin that has bounced back and forth collides with the melted resin that has flowed from the center of the disk, and flows again along the stamper surface. At this time, a gap is formed below the pit as shown. 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. The gap does not collapse even though the filling is in progress.

Although the mold slightly opens due to the impact during injection, the mold is immediately clamped again to the original position by the clamping force. At this time, a pressure R is applied in the thickness direction of the disk substrate, and the resin is pushed into the space between the guide groove and the pit. However, the lower portion of the pit has a small amount of resin wraparound, so that a gap remains. The center position of the cross section of the pit is not located at the midpoint of the groove interval L in the disk substrate 5 formed as shown in FIG. That is, the dimensions A ≠ B shown
Becomes

[0011]

Therefore, when a pit signal (address or other information) recorded in advance is read from a disk medium processed after molding in this manner, the laser beam for reading is formed in a groove. Since tracking control is performed so as to seek the midpoint of the interval L, when the pit is not located at the midpoint 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. There is a drawback that reading becomes impossible due to an address signal or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks, and has as its object to provide a disk substrate forming master capable of correcting a pit position to a middle point of a groove interval when forming a disk substrate.

[0013]

According to the present invention, as shown in FIG. 1, a pit 7 is provided between adjacent guide grooves 6 formed concentrically or spirally for tracking guide. Stamper 9 for molding a disk substrate on which addresses and other information are recorded
In the master 8 for manufacturing the above, the guide grooves 6 and the pits 7 are each formed into a trapezoidal, V-shaped or U-shaped symmetrical cross section in the disk radial direction, and each center position of the cross section of the adjacent guide groove 6 is formed. The center position of the cross section of the pit 7 is shifted from the midpoint of the groove interval L toward 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 a conventional manufacturing method, the center of the cross section of the pit 7 which should be located at the middle point of the groove interval L (where L = A + B) is as shown in FIG. It is formed so as to be shifted to the disk outer peripheral side Q so that the dimension A> B, and the ratio of the value of A to the value of B becomes constant depending on the material, temperature, viscosity, injection pressure and the like of the molten resin. Therefore,
If the cross-sectional center position of the pit 7 is shifted to the center side of the disk in advance and the master 8 is formed so that the dimension C> D, as a result, the disk substrate injection-formed will have a groove spacing L
The center position of the cross section of the pit 7 can be corrected to the midpoint.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In order to make the description of the configuration and operation easy to understand, the same parts are denoted by the same reference numerals throughout the drawings, and the duplicate description thereof will be omitted.

FIG. 1 is a partial sectional view showing an example of a disk substrate forming master according to the present invention. This cross section shows the disk cut in the radial direction. In the figure, reference numeral 8 denotes a disk substrate forming master (original master), 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. Composed of the applied photoresist 83 and the photoresist
The surface of 83 is selectively exposed to laser light and further developed to form guide grooves 6 and pits 7.

The cross-sectional shapes of the guide grooves 6 and the pits 7 are formed in a symmetrical trapezoidal shape, a V-shape or a U-shape, respectively, as in the prior art. The center position of the cross section of the pit 7 is shifted from the midpoint of the groove interval L to the disk center side P with respect to the groove interval L.

That is, the distance between the center position of the cross section of the guide groove 6 on the disk outer peripheral side Q 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 disk center side P is The distance from the center position of the cross section is D, and a required ratio is formed in advance so as to satisfy C> D in accordance with conventional performance data.

Reference numeral 9 denotes a stamper manufactured using the master 8, which 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 formed on the surface of the metal film 91 to a predetermined thickness. After the nickel plating layer 92 is completed, the stamper 9 is obtained by peeling off the master 8. Can be

Since the laser beam irradiating the surface of the photoresist 83 forms the guide grooves 6 and the pits 7 in a symmetrical cross section, a special mask or the like is not required, and a conventional irradiation method can be used.

The procedure for irradiating the master 8 with laser light is as follows. First, the guide groove 6 is written and then the pit 7 is written. 7 may be written 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 1/1 / L of the distance L between the guide grooves.
When the distance L between the guide grooves is controlled to a normal value in a state where the distance is set to be 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. In such a state, the distance between the pit 7 and the adjacent pit 7 may be written at regular intervals.

[0023]

According to the present invention, a disk substrate formed by using a stamper in which the center of the cross section of the pit is shifted toward the disk center from the midpoint of the groove interval between the guide groove and the adjacent guide groove is transferred. There is an effect that the position of the formed pit is corrected to the midpoint of the groove interval and molding can be performed.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing an example of a disc substrate forming 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 master for disk substrate molding (master) 9 stamper L groove interval P center side of disk

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 7/26 G11B 7/007

Claims (1)

(57) [Claims] 1. A stamper for forming a disk substrate on which addresses and other information are recorded by pits (7) between adjacent guide grooves (6) formed concentrically or spirally for tracking guide. (9)
In the disk substrate forming master (8) for manufacturing the above, the cross-sectional shape of each of the guide grooves (6) and the pits (7) in the disk radial direction is formed into a symmetric trapezoidal, V-shaped or U-shaped, respectively, The center position of the cross section of the pit (7) is shifted 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 respective center positions of the cross section of the guide groove (6). A master for forming a disk substrate, which is formed by being shifted.