JP3232703B2 - Electroforming method for manufacturing nickel stamper for optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Optical disks are characterized by their large capacity and high recording density, compared to floppy disks and hard disks, and are being actively researched and developed. In general, a substrate for an optical disc is produced by injection molding using a stamper so that mass production is possible while maintaining the above-mentioned excellent characteristics. At this time, grooves and pits are formed on the stamper, and these are transferred to the optical disk. Therefore, the stamper is required to have high precision as a master and durability during injection molding. This durability largely depends not only on the injection conditions but also on the signal surface hardness of the stamper.

[0003] A conventional method of manufacturing a stamper for an optical disc is performed by the following method, for example.
That is, a resist is uniformly coated on a glass substrate having a polished surface to a required thickness by a spin coating method, exposed to a desired pattern by a laser cutting machine after prebaking, and then developed. To form pits and / or groups. The surface of the resist-coated glass substrate having pits and / or grooves is coated with silver, nickel, or the like by electroless plating, sputtering, or vacuum evaporation to maintain conductivity, and then electroformed. Deposit nickel of any thickness. Thereafter, the nickel is peeled off from the glass substrate, and the resist remaining on the signal surface of the stamper is removed with a solvent and washed. Then polish the back side
After cleaning, the inner and outer diameters are processed to complete the stamper.

Conventionally, as an electroforming method for depositing nickel, a current density is gradually increased with an increase in the electroforming time, and a constant current density is maintained irrespective of an increase in the electroforming time. It was a late stage of electroforming. The first stage of electroforming is performed to prevent the resist from peeling off from the glass master by heat generated during electroforming by gradually increasing the thickness of nickel. In the latter stage of electroforming, electroforming is performed at a constant current density in order to keep the physical properties of the obtained stamper constant.

[0005] However, when electroforming is performed in the two kinds of processes as described above, the reproducibility of the stamper hardness only decreases because the current density is not constant in the initial process of electroforming that governs the signal surface hardness of the stamper. Therefore, it becomes difficult to manufacture a stamper having the expected signal surface hardness. This not only causes a large change in the injection molding conditions, but also causes a problem that the number of plastic substrates obtained by molding greatly changes.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to carry out a process in which the current density is constant in order to control the hardness in the initial process of electroforming which is a dominant factor of the signal surface hardness. An object of the present invention is to provide an electroforming method for manufacturing a stamper for an optical disk which is relatively easy to control the hardness of a signal surface, has high reproducibility, and has a high yield by being provided in an initial step of electroforming.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that the current waveform and the quantity of electricity at the time of manufacturing an optical disk stamper by electroforming are improved. It has been found that a stamper having an expected signal surface hardness can be obtained by fine control, and the present invention has been completed.

That is, the present invention provides a process 1 for increasing the current density with an increase in the electroforming time, a process 2 for maintaining a constant current density for controlling the signal surface hardness, and again increasing the current density with an increase in time. An electroforming method for manufacturing a nickel stamper for an optical disc, characterized by performing electroforming using a current density waveform including a step 3 of increasing and a step 4 of maintaining a constant current density.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic example of the current density waveform of the present invention. For comparison, FIG. 2 shows a current density waveform used so far.

The rate of increase in the current density in step 1 depends on the type, thickness and electric resistance of the conductive film coated on the resist surface, but it is 2 to 100 A / dm ² / h.
r is desirable. If it is less than 2 A / dm ² / hr, the electrolyte is weakly acidic, so that the conductive film is dissolved, or the generation of hydrogen gas, which is a competitive reaction of nickel deposition, takes precedence, and the thickness of the stamper is reproducible. Is lost, or if it exceeds 100 A / dm ² / hr, the resist may peel off from the glass master due to heat generation due to electrical resistance as described above. Further, the amount of electricity in this process is desirably 0.1% to 3% with respect to the total amount of electricity. If the amount is less than 0.1%, the purpose of gradually increasing the current density is not achieved. If it exceeds 3%, the reproducibility of controlling the signal surface hardness of the stamper may be poor. In the process 1, the current density is increased with time as described above, but it is desirable that the final current density in the process 1 is equal to a value desired in the process 2.

The value of the constant current density in the process 2, that is, the signal surface hardness of the stamper is governed by this value. The value varies depending on the composition of the electroforming solution, the target signal surface hardness of the stamper, and the like. 2 to 10 A / dm ² is desirable. If it is less than 2 A / dm ² , the secondary electrolytic reaction occurs preferentially, or the internal stress increases, so that the reproducibility of the hardness may decrease or the stamper may be deformed. If it exceeds 10 A / dm ² , there will be no significant difference from the conventional current density waveform.

The amount of electricity at this time is preferably 3% to 20% of the total amount of electricity. If it is less than 3%, the signal surface hardness is preferentially controlled by the conditions of the steps 3 and 4, and not only is it difficult to obtain the expected signal surface hardness, but also its reproducibility is poor. There is no problem even if it is 20% or more, but the signal surface hardness is hardly increased, and the current density in this process is small, so that only the stamper manufacturing time is lengthened.

The rate of increase in the current density in step 3 can be made larger than in step 1 because nickel has already been deposited to a certain thickness, and the value thereof is not particularly limited. 10 to 200 A / dm ² / hr
Is desirable. It may be less than 10 A / dm ² / hr, but it only takes time. Also, 200 A / dm ² /
If the heating time exceeds hr, the temperature of the electroforming solution rapidly changes locally due to the generation of Joule heat due to the electrolytic reaction, so that the reproducibility becomes poor. In addition, there is a possibility that the glass master is cracked. The amount of electricity in this process is not particularly limited as long as reproducibility is obtained in the signal surface hardness of the stamper, but is preferably 0.5% to 10% with respect to the total amount of electricity.
If it is less than 10%, heat generation during electroforming may occur, and if it exceeds 10%, the electroforming time may be increased. In this step 3, the current density is increased with time as described above, but the final current density in step 3 is as follows.
Is desirably equal to the desired value.

The current density in step 4 can be arbitrarily determined according to the composition of the electroforming solution, the roughness of the electroformed back surface, and the like, but is preferably 8 to 30 A / dm ² . 8
When it is less than A / dm ² , the effect of the present invention is hardly obtained,
If it is larger than 30 A / dm ² , the thickness of the stamper may be different from the desired thickness due to a slight timing deviation of the end of the electroforming or a measurement error of the electric meter.

The method for imparting conductivity to the resist surface is not particularly limited, and examples thereof include ordinary methods such as a sputtering method, a vacuum deposition method, and an electroless plating method. In addition, the metal used at that time is not particularly limited, and examples thereof include silver, nickel, and alloys containing these as a main component.

[0017]

As is clear from the above description, according to the present invention, the signal surface hardness of the stamper can be controlled, the durability of the stamper can be improved, the injection molding conditions can be stabilized, and the like.
Further, there are effects such as improvement of substrate characteristics and reduction of substrate production cost.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Example 1 450 g / l nickel sulfamate tetrahydrate, 35
g / l of boric acid, 5 g / l of nickel chloride hexahydrate and an anti-pitting agent at 50 ° C. in an electroforming solution at 50 ° C., the rate of increase in current density in step 1 was 50 A / dm ² /
hr, the constant current density in step ² is 3 A / dm ² , the rate of increase in current density in step 3 is 100 A / dm ² / hr, the constant current density in step 4 is 10 A / dm ² , The nickel stamper for an optical disk having a signal surface hardness of about 260 was manufactured with the proportions of 1%, 10%, 5% and 84%.

Example 2 A nickel stamper for an optical disk having a signal surface hardness of about 250 was manufactured in the same manner as in Example 1 except that the constant current density in Step 2 was changed to 4 A / dm ² .

Example 3 A nickel stamper for an optical disk having a signal surface hardness of about 220 was manufactured in the same manner as in Example 1 except that the constant current density in Step 2 was changed to 8 A / dm ² .

Example 4 For an optical disk having a signal surface hardness of about 265 in the same manner as in Example 1, except that the ratio of the amount of electricity in Step 2 was 20% and the ratio of the amount of electricity in Step 4 was 74%. A nickel stamper was manufactured.

Example 5 For an optical disk having a signal surface hardness of about 240 in the same manner as in Example 1, except that the ratio of the amount of electricity in Step 2 was 3% and the ratio of the amount of electricity in Step 4 was 82%. A nickel stamper was manufactured.

Example 6 The rate of increase in current density in step 1 was 10 A / dm ² / hr
A nickel stamper for an optical disk having a signal surface hardness of about 265 was manufactured in the same manner as in Example 1 except that the above conditions were satisfied.

Example 7 The rate of increase in current density in step 1 was 100 A / dm ² / h
A nickel stamper for an optical disk having a signal surface hardness of about 255 was manufactured in the same manner as in Example 1 except that r was changed to r.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a current density waveform according to the present invention.

FIG. 2 is a diagram showing an example of a current density waveform conventionally used.

Claims (4)

(57) [Claims] 1. An electroforming method for manufacturing a nickel stamper for an optical disk, comprising: a step 1 for increasing the current density as the electroforming time increases, a step 2 for maintaining a constant current density, and a current again as the time increases. electrostatic Rutotomoni, in the process 1 using a current density waveform consisting of process 4 to maintain the process increasing the density 3, and a constant current density
The rate of increase of the flow density is 2 A / dm ² / hr to 100 A /
dm ² / hr, the amount of electricity corresponds to the total amount of electricity required for electroforming.
0.1% to 3%, the value of the current density in the step 2
2 A / dm ^{2 to} 10 A / dm ² , and the amount of electricity required for electroforming
3% to 20% and to electroforming electroforming process for the nickel stamper manufacturing optical disc and performs the total amount of electricity. 2. The method according to claim 2, wherein the rate of increase in current density in step 3 of increasing current density with increasing time is 10 A / dm.
^The electroforming method for manufacturing a nickel stamper for an optical disk according to claim 1, wherein the pressure is in the range of ² / hr to 200A / dm2 / hr. 3. The optical disk according to claim 1, wherein the amount of electricity in step 3 of increasing the current density with increasing time is 0.5% to 10% of the total amount of electricity required for electroforming. Electroforming method for nickel stamper production. 4. A value of the current density in the process 4 to maintain a constant current density, the nickel stamper for manufacturing the optical disc according to any one of claims 1 to 3 which is 8A / dm ² ~30A / dm ² Method for electroforming.