JP3207560B2 - Polishing method for backside of stamper for optical disc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a back surface of a stamper used in a copying process of an optical disk substrate used for a CD, a VD or the like.

[0002]

2. Description of the Related Art Generally, a method as shown in FIG. 1 is used to produce a duplicating stamper for an optical disk substrate.

As shown in FIG. 1A, first, a photoresist is uniformly applied to the surface of a flat glass disk 1 by a spin coating method or the like, and then dried to form a photoresist thin film 2.
Is formed. Next, the glass disk 1 carrying the photoresist film 2 is mounted on a so-called cutting device, and a laser beam 3 corresponding to a signal is irradiated onto the rotating photoresist film 2 via an objective lens 4 (FIG. 1).
(B)). In this manner, a concentric pit row carrying a predetermined signal is formed as a latent image on the photoresist film 2, and a glass master having a row of pits 5 is created by development (FIG. 1 (c)).

Next, as shown in FIG. 1D, a conductive film 7 of silver, nickel or the like is formed on the photoresist film 2 by sputtering or the like to make the pit surface of the glass master disk conductive. The glass master 1 having such a conductive film 7 is immersed in an electroforming tank to form a nickel plating film 8 having a thickness of about 0.3 mm on the conductive film 7 (FIG. 1E). The electroformed nickel plating film 8 is peeled from the glass disk 1 and the photoresist 2 remaining on the nickel plating film is washed and removed to obtain a master master (master stamper) 8 (FIG. 1 (f)).

[0005] Next, as shown in FIG. 1 (g), after forming a release film of chromic acid on the surface of the master stamper 8,
A nickel plating film 9 having a thickness of 0.3 mm is formed on the pit surface of the master stamper 8 by immersion in an electroforming tank. A backing plate 10 is provided on the back surface of the nickel plating film 9 (FIG. 1).
(H)) Then, the nickel plating film 9 is peeled off from the master stamper 8 to obtain a mother master (mother stamper) 9 (FIG. 1 (i)).

Next, as shown in FIG. 1 (j), after a release film of chromic acid is formed on the surface of such a mother stamper 9, it is immersed in an electroforming tank to form a film on the pit surface of the mother stamper 9. A nickel plating film 11 having a thickness of 0.3 mm is formed. The nickel plating film 11 is peeled from the mother stamper 9 to obtain a sun stamper 11 (FIG. 1 (h)).

Next, as shown in FIG. 1 (l), a protective film 12 is applied on the sun stamper 11 and is set in a jig for a back-surface polishing machine, and the back surface is polished to obtain a polished sun stamper 13.

However, according to the above-described backside polishing method, the polishing liquid permeates between the sun stamper 11 and the protective film 12, and water and polishing particles adhere to the pits and corrode the stamper surface. The optical disk substrate formed by using the polished stamper 13 formed in this way has a defect that normal pits are not transferred and eventually cause a signal loss of the optical disk.

Japanese Patent Application Laid-Open No. 60-251536 discloses a signal forming range of a glass master on which a photoresist film is formed in order to prevent cooling water from entering an interface between a glass substrate and a nickel film when polishing a master stamper. A method is described in which dummy pits are formed on the inner side to increase the adhesion between the glass substrate and the photoresist film and between the photoresist film and the nickel conductive film.

Japanese Patent Publication No. 60-48051 discloses a method in which a large number of concentric grooves are formed on the inner and outer circumferences of a glass substrate after forming pits. To improve the peeling prevention effect.

However, in the method using the dummy pits, it is difficult to form the pits only in the vicinity of the signal forming range, and the adhesion by the pits is weak, and the effect of preventing peeling is insufficient. Further, in the surface roughening by sanding, fine particles are generated at the time of surface roughening, so that the surface of the master is easily stained, and the method of protecting the surface of the master is difficult and impractical. Furthermore, all of them are merely those taking into account the steps up to electroforming.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of polishing the back surface of a stamper, which can improve the adhesion of a protective film to the stamper and protect the surface of the stamper from a polishing liquid. .

[0013]

According to the present invention, after a protective film is provided on the surface of a stamper (pit formation side) and then the back surface is polished, an adhesive is applied to the outer peripheral portion of the stamper surface. A method of applying and drying a protective film after or without heating and then polishing the back surface.

The adhesive is preferably an adhesive such as a photoresist or an instant adhesive.

[0015]

The present invention will be described below in detail with reference to examples.

[Example 1] Outer periphery of a sun stamper (Ni material, outer diameter: 160 mm, plate thickness: 0.3 mm) prepared by an ordinary method
A photoresist 2CP (OFPR-800, manufactured by Tokyo Ohka Co., Ltd.) was included in Bencotton (with a radius of 75 mm or more) and applied in a circumferential shape with a width of about 5 mm. Next, after keeping the temperature in an oven at 70 ° C. for 10 minutes, 80 ml of thinner and 60 ml of clear were prepared and spray-coated on the photoresist. After maintaining the temperature again in an oven at 70 ° C. for 10 minutes, the back surface of the stamper was polished by a conventional method (by attaching a stamper setting jig to a polishing machine). Note that CP = centi poi
Indicates se.

[Embodiment 2] A photoresist is circumferentially applied to the outer periphery of the sun stamper in the same manner as in Embodiment 1, and
About 3 mm width was placed on the inner peripheral side, and the coating was applied again to a 5 mm width. Next, heating, application of a protective film, reheating were performed in the same manner as in Example 1, and the back surface was polished.

Example 3 A 2 CP of photoresist (OFPR-800 manufactured by Tokyo Ohka Co., Ltd.) was diluted to 0.5 CP with a thinner, and the outer periphery of a sun stamper (radius 75 mm) as in Example 1 was used.
The above was applied to a width of 10 mm with a dispenser, and the photoresist was spun at 300 revolutions per minute by a spinner to scatter excess photoresist. Then in an oven at 90 ° C for 3
After keeping it warm for 0 minutes, thinner 80ml, clearer 60ml
Was spray-coated on the photoresist.
Next, after keeping the temperature in an oven at 70 ° C. for 10 minutes, the back surface was polished by an ordinary method.

[Embodiment 4] An α-cyanoacrylic resin was formed on the outer peripheral portion (with a radius of 75 mm or more) of the same sun stamper as in Embodiment 1.
2mm instant adhesive (Alteco made by Alpha Giken)
The adhesive was applied to the width with a dispenser, and excess adhesive was scattered with a spinner in the same manner as in Example 3, and the adhesive was applied in a circumferential shape. When the adhesive is in a semi-dry state, 80ml of thinner,
60 ml of clear was prepared and sprayed onto the adhesive. Next, after keeping the temperature in an oven at 70 ° C. for 10 minutes, the back surface was polished by an ordinary method.

[Embodiment 5] Instead of the adhesive used in Embodiment 4, an epoxy-based adhesive (Cemedine EP-made by Cemedine Co., Ltd.) was used.
171) was applied to the outer periphery of the sun stamper with a width of 5 mm and cured at 80 ° C. for 20 minutes. Next, in the same manner as in Example 4, a protective film was applied by spraying, and after keeping the temperature in an oven, the back surface was polished.

Table 1 shows the results of visual inspection of the sun stampers obtained in Examples 1 to 5 described above.

[0022]

[Table 1]

(Note) Visual inspection: Immediately after polishing, the protective film is peeled off and the presence or absence of intrusion of the polishing liquid (material) is observed. When the polishing liquid has penetrated, the surface of the penetrated portion looks white. Moreover, over time, it is corroded by the acid contained in the abrasive.

As is clear from Table 1, according to the examples, no intrusion of the polishing liquid occurs during polishing. In the case of the adhesives used in Examples 4 and 5, penetration of the polishing liquid between the stamper and the protective film can be prevented, but it is difficult to remove the adhesive from the stamper after polishing. However, since the coating is applied only near the outer periphery of the stamper, the stamper is eventually cut when finishing the outer diameter, so that there is no problem.

[0025]

As described above, according to the present invention, it is possible to completely prevent the penetration of the polishing liquid when polishing the back surface of the sun stamper. Further, since the photoresist is used as the adhesive, it can be shared with the photoresist used in the mastering step, and can also be used as a cleaning liquid for the resist deposit used in the mastering step, which is extremely advantageous in terms of production cost.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining a stamper forming process.

[Explanation of symbols]

 8 Master stamper 9 Mother stamper 11 Sun stamper 12 Protective film 13 Polished sun stamper

Claims (3)

(57) [Claims] 1. A method for polishing a back surface of a stamper, in which a protective film is provided on the surface of the stamper and the back surface is polished, the adhesive is applied to an outer peripheral portion of the surface of the stamper, and the protective film is heated or not. A method for polishing the back surface of an optical disk stamper, which comprises applying, drying and then polishing the back surface. 2. The method for polishing a back surface of a stamper for an optical disk according to claim 1, wherein a photoresist or an adhesive is used as the adhesive. 3. The method for polishing the back surface of an optical disk stamper according to claim 2, wherein an instant adhesive is used as the adhesive.