JPH09223337A - Production of stamper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the polishing cost by simplifying a polishing stage for the rear surface of a stamper. SOLUTION: The stamper is produced by subjecting a master disk, on which information is formed by ruggedness, to electroforming to form a metallic sheet transferred with the patterns of this master disk, then polishing the surface of this metallic sheet on the side opposite to its information-transferred surface. In such a case, the current of the direction reverse to the energization direction at the time of the electroforming is supplied to the electroforming product (metallic sheet) within an electroforming bath after the end of the electroforming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a stamper for an optical disc.

[0002]

2. Description of the Related Art One of the characteristics of an optical disk master (hereinafter referred to as a stamper) that affects an optical disk is flatness of the stamper. Specifically, there are two types of roughness and warpage on the back surface (the surface opposite to the information transfer surface).
The former back surface roughness is transferred to the optical disk substrate via the groove surface and affects the base material of the information area. The warp of the latter is
This causes mechanical characteristics of the optical disk substrate and double transfer.

Stampers are usually manufactured by the following steps. That is, resist coating on a glass substrate, baking of a fine pattern by a cutting device,
The steps are development processing, electroconductivity processing, electroforming, back surface (electroformed surface) polishing, stamper peeling, and inner and outer diameter processing. Of these steps, the back surface polishing step is usually achieved by mechanically polishing the back surface of the electroformed product that has undergone the electroforming step to smooth the roughness of the back surface. A tape polishing machine or the like is often used as the mechanical polishing method.

[0004]

Since such mechanical polishing tends to cause warping of the stamper, the occurrence of warping can be prevented by performing multi-step polishing such as rough polishing, intermediate finish polishing and finish polishing. Need to reduce. Therefore, mechanical polishing causes problems such as complication of the polishing apparatus and extension of the polishing tact, which imposes a burden on the stamper manufacturing cost. Further, even in the case of performing the multi-step polishing as described above, it is difficult to completely control the warp of the stamper, which is a cause of deteriorating the injection molding performance of the stamper. As a method of omitting such mechanical polishing, it has been considered to produce an electroformed product by adding a leveling agent to an electroforming bath and performing electroforming to thereby obtain an electroformed product whose back surface is close to a mirror surface. However, this method has a problem that impurities such as sulfur are easily mixed in the electroformed product, and the corrosion resistance of the stamper is lowered.

[0005]

In view of the above problems, the present inventor has made earnest studies, and as a result, adopted electrolytic polishing as a means for polishing the back surface of a stamper, and further used this electrolytic polishing in an electroforming tank. The present invention has been completed, paying attention to what is done. That is, the present invention, electroforming is performed on a master plate on which information is formed in a concavo-convex pattern to form a metal plate on which the pattern of the master plate is transferred, and then the surface opposite to the information transfer surface of the metal plate is polished. In the method for producing a stamper, after the electroforming, a current in a direction opposite to the energizing direction during electroforming is applied to the electroformed product (metal plate) in the electroforming bath. Is the gist.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION This will be described in detail below. The principle of electrolytic polishing will be briefly described. When a metal (object to be treated) is energized as an anode in an electrolytic solution, metal ions are eluted from the metal surface. Therefore, the metal ion concentration of the electrolytic solution becomes high on the metal surface. Here, when the metal surface is uneven, the concave portion has a higher metal ion concentration than the convex portion. From an equilibrium perspective, metal elution is less likely to occur in areas where the metal ion concentration is high, and conversely, in areas where the metal ion concentration is low,
Elution of metal is likely to occur. Therefore, the elution progresses more selectively in the convex portion having a lower metal ion concentration, and as a result, the metal surface is smoothed.

Usually, the metal used for the stamper is nickel, but to manufacture the stamper by electroforming, a nickel sulfamate bath is used, which is easy to obtain an electroformed product with low stress. The nickel sulfamate bath is
For example, nickel sulfamate is added in an amount of 300 to 600 g / liter and boric acid in an amount of 20 to 50 g / liter, and additives such as a surfactant are added as necessary.

When electrolysis is performed in such an electrolytic solution using nickel as an anode for electropolishing, the nickel surface is passivated, and normal electropolishing may not be performed. In the present invention, in order to prevent such passivation, at least one kind of metal chloride or metal bromide is added to the electrolytic solution as an anode dissolving agent. Examples of these metal chlorides or bromides include, for example, nickel salts, among which NiCl ₂ .6H ₂ O and N
It is preferred to use iBr ₂ .

The amount of these metal chlorides or bromides added to the electrolytic solution may be such an amount that inhibits passivation. In the case of NiCl ₂ .6H ₂ O, 0.05 to ₂ g / liter, N 2
In the case of iBr2, the range of 0.05 to ₅ g / liter is preferable. If the amount is less than 0.05 g / liter, the electropolishing is difficult to proceed due to the passivation of nickel, and if the amount exceeds 2 g / liter or 5 g / liter, the nickel surface is locally eroded to cause unevenness. is there. It should be noted that these two kinds of anode dissolving agents may be used in combination.

The electropolishing apparatus used in the manufacturing method of the present invention may be a known electroforming apparatus. The energization conditions during electropolishing depend on the composition of the electroforming bath, the temperature, and the surface roughness of the electroformed product, but are preferably ² to 20 A / dm ² and about 5 to 20 minutes. After the electroforming is completed, the current is applied in the opposite direction and the current is applied to carry out electrolytic polishing under the above conditions.

[0011]

Next, an embodiment of the present invention will be described. Example 1 Outer diameter 140 mm obtained by transferring a fine pattern to glass
A thin nickel film was deposited to a thickness of 1500 to 2000 Å on the glass master disk of No. 1 by the sputtering film forming method, and was subjected to a conductive treatment. Set this electroconductive master to the cathode of the electroforming machine,
It was electroformed. The thickness of the electroformed film produced was about 300 μm. The energization conditions during electroforming were a current density of 15 A / dm ² and an energization amount of 6600 A
・ Min and electroforming temperature were 55 ° C. The electrolytic solution for electroforming is nickel sulfamate 450 g / l, boric acid 30 g / l, sodium lauryl sulfate 0.5 g / l.
A solution obtained by adding 0 to 5 g / liter of nickel chloride to a liter solution was used. After the electroforming was completed, the energization direction was reversed with the master set on the electrode, and electrolytic polishing was performed at 4 A / dm ² for 15 minutes. The surface roughness Ra of the back surface of the stamper after electrolytic polishing was measured. Ra is a numerical value obtained by obtaining the uneven shape of a linear arbitrary position on the back surface of the stamper and averaging the deviation from the center line. FIG. 1 shows the amount of nickel chloride added and the surface roughness Ra after electrolytic polishing of the back surface of the stamper.
Shows the relationship with.

Example 2 Nickel bromide was added to the electrolytic solution in an amount of 0 to 6 instead of nickel chloride.
electroforming in the same manner as in Example 1 except that g / liter was added,
Electrolytic polishing was performed. The measurement results are also shown in FIG.

From FIG. 1, it was confirmed that the surface roughness Ra of the back surface of the stamper was smoothed to about 0.02 μm by electrolytic polishing, which was effective as a polishing method replacing mechanical polishing. It was also found that both nickel chloride and nickel bromide enhance the effect of electrolytic polishing.

[0014]

According to the present invention, there is no need to separately provide equipment as a polishing device for the back surface of the stamper, and the equipment cost can be reduced. Further, warping of the stamper due to mechanical polishing does not occur, and the stamper can be manufactured without impairing corrosion resistance.

[Brief description of drawings]

FIG. 1 shows nickel chloride (□) in an example of the present invention.
5 is a graph showing the relationship between the amount of nickel bromide (■) added and the surface roughness Ra of the stamper back surface after electrolytic polishing.

Claims (2)

[Claims] 1. A master plate on which information is formed in a concavo-convex pattern is electroformed to form a metal plate on which the pattern of the master plate is transferred, and then the surface of the metal plate opposite to the information transfer surface is polished. In the method for producing a stamper, after the electroforming, a current in a direction opposite to the energizing direction during electroforming is applied to the electroformed product (metal plate) in the electroforming bath. . 2. The electrolytic solution for electroforming used in the electroforming step is mainly composed of nickel sulfamate and further contains at least one kind of metal chloride or metal bromide as an anode dissolving agent. A method for manufacturing the described stamper.