JPH01191796A - Method for reproducing information recording disk - Google Patents

Abstract

PURPOSE:To obtain a metal master for forming faithful reproduced disks causing no deformation to the information signal by plating the surface of a photoresist layer having recorded information with an electroless plating bath satisfying prescribed conditions at a low temp. CONSTITUTION:An electroless plating bath of 5-7pH contg. a required amt. of a reducing agent including hypophosphite or dimethylaminoborane, 0.05-0.15mol/l Ni salt and tartrate and/or glycine as a complexing agent is prepd. The molar concn. of the chelating agent is >=1.5 times the concn. of the Ni salt. An information signal is recorded on a photoresist layer formed on a discoid substrate, the layer is developed and the resulting surface having the recorded information is subjected to electroless plating with the plating bath at 30-60 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a method for obtaining a metal master for producing a duplicate disc from a master disc such as an information recording disc, particularly an optical disc.

To create information recording discs such as the Saramai Zakya Goko disc, for example, a layer of photoresist is formed on a flat glass substrate, information is recorded using light, etc., and then developed to form an uneven signal pattern. form a recorded master disc. Next, a metal layer is formed on the surface of this recording master, for example, by electroless plating, and a backing metal layer of an appropriate thickness is further provided by electrolytic plating, and then separated from the master to obtain a metal master. Furthermore, using such a metal master, a molding mold is created by electroplating in the same manner as described above, and a synthetic resin is molded using this molding mold, thereby producing a duplicate disc having a signal pattern on its surface. is being created.

In manufacturing a duplicate disc from an original disc in this way, electroless plating is applied to the surface of the photoresist layer, but since such plating needs to faithfully reproduce the uneven shape of the information signal, nickel plating is usually used. used. However, discs for recording optical information need to increase the information density, so positive photoresists are used to record minute and precise information, and thus were conventionally used for duplicating lacquer discs. Known alkaline electroless nickel plating baths have the problem of corroding the photoresist layer and impairing the fidelity of information.

Therefore, we attempted to form an electroless nickel plating layer using an acidic bath, but even if we used a conventionally known acidic nickel plating bath using hypophosphite as a reducing agent, Good plating cannot be achieved unless the temperature is high, e.g. 70°C or higher.
It is not possible to prevent accuracy from being impaired due to deformation of the information recording surface.

When the plating temperature is low, the adhesion of the nickel film to the photoresist surface decreases, causing fine cracks and cracks in the plating layer, as well as partial peeling, resulting in the problem that the nickel plating layer cannot be replaced to withstand subsequent operations. there were.

Under these circumstances, the inventor of the present invention has developed a method for faithfully reproducing information signals recorded on a positive photoresist layer.
We conducted intensive research on electroless nickel plating baths that can obtain nickel coating layers with good adhesion at low temperatures, and as a result, we manufactured reproduction discs that were faithful to the information recording master discs using the newly discovered electroless nickel plating baths. The aim is to provide a method to do so.

[Structure of the invention]

The method for duplicating information recording disks of the present invention for accomplishing the above-mentioned problems involves recording an information signal on a photoresist layer provided on a disk substrate, developing it, applying electroless metal plating to the information recording surface, and then applying electroless metal plating to the information recording surface. Furthermore, when forming a metal reinforcing layer and manufacturing a reproduction disc, the electroless plating is performed using a nickel salt of 0.05 to 0.15 M/I!, at least 1.5 times the concentration of the nickel salt. containing a molar concentration of chelating agent selected from tartrate, glycine, and mixtures thereof, and the required amount of reducing agent, either chlorine hypophosphite or dimethylaminoborane, in pJ (5 , o to 7.0, and is characterized in that it is carried out at a temperature of 30 to 60°C.

In the present invention, the plating bath used for electroless plating on the surface of the photoresist on which information signals are recorded contains a nickel salt, and examples of such nickel salt include nickel sulfate, nickel chloride, and nickel nitrate. . If the concentration of nickel salt is too low, the plating speed will be slow and inefficient, and if it is too high, the plating efficiency will reach a plateau, the life will not be long, and it will warp, making it uneconomical. as 0
．． It is desirable that it be within the range of 0.05 to 0.15 M/l.

Further, the chelating agent used in combination with the nickel salt is preferably tartrate or glycine, and a mixture thereof may be used. These chelating agents meet the desirable plating bath conditions for performing nickel plating without deforming the information signals recorded on the photoresist layer, especially the positive photoresist layer, namely non-alkalinity and low temperature plating. It is suitable for providing a nickel film that satisfies the following two conditions, has good adhesion to the photoresist layer, and does not cause stress cracks or the like.

If the plating bath is alkaline, the photoresist layer will erode and swell, making it impossible to expect a faithful reproduction of the recorded signal shape.If plating is performed at high temperatures as in the past, the photoresist layer will soften and swell. Swelling tends to proceed, and the signal shape cannot be accurately reproduced. In contrast, with conventional acidic electroless nickel plating baths, adhesion to the photoresist layer could not be satisfied when plating was attempted at low temperatures, but with the use of the chelating agent of the present invention, It was discovered that a film with excellent adhesion could be obtained under plating conditions of acidic acidity and low temperature.

The chelating agent, i.e., tartrate or glycine, used in the plating bath of the present invention needs to be used at a molar concentration of 1.5 times or more relative to the nickel salt in the bath, and if it is less than this, the adhesion improving effect is insufficient. becomes. Although there is no upper limit to the concentration of these chelating agents, it is uneconomical if the concentration is too high, so for practical purposes, it is sufficient to use the concentration at most three times that of the nickel salt.

In the present invention, the reducing agent used in the electroless nickel plating bath is preferably either hypophosphorous acid or dimethylaminoborane. When a hypophosphite salt such as sodium hypophosphite is used, a coating of an alloy of nickel and phosphorus is obtained, but the amount of sodium hypophosphite used is 10 to 30 g/I! If the amount used is too small, the plating speed will be slow (and impractical), and if the amount used is too large, the plating speed will be saturated and there will be no advantage. When dimethylaminoborane is used, a coating of nickel and boron alloy is obtained, but the amount of borane used is preferably within the range of 2 to 4 g/I!.If the amount used is too small, the plating rate will be reduced. It becomes slow and impractical, and if too much is used, the plating speed becomes saturated and there is no advantage.

Such a plating bath in the present invention has a pH of 5°0 to
7.0 is preferably used. Hydrochloric acid, sodium hydroxide, etc. can be used to adjust the pH. If the pH is lower than 5.0, it is not practical because the plating rate decreases, and if the pH exceeds 7.0, the fidelity of the recording signal on the photoresist layer, which is the original purpose, decreases, which is not preferable.

In the present invention, when performing electroless plating on the signal recording surface of photoresist using such a plating bath, the bath temperature is preferably within the range of 30 to 60°C, and the bath temperature is lower than 30''C. In some cases, the rate of formation of the plating film is slow and impractical, and if the bath temperature increases, the rate of film formation becomes faster, but the life of the bath becomes shorter, making it uneconomical.
Softening deformation of the photoresist layer reduces information fidelity.

In the present invention, an optical disk master having a photoresist layer on which an optical signal is recorded is obtained according to a conventionally known method, and then subjected to a sensitization treatment and an activation treatment according to a known pretreatment method. Perform electrolytic nickel plating. The nickel plating film thus obtained has no defects such as stress cranks, has good adhesion to the photoresist layer, and does not peel off when washed under running water, so it can be used in the next step, such as electrolytic plating. No problems occur during electrolytic nickel plating, and a faithful reproduction disc can be obtained.

A disk substrate was prepared by providing a positive photoresist layer with a thickness of 0.1 μm on a smooth glass disk with a fork opening diameter of 220 mm by a spin cord method. This was irradiated with a laser signal and developed using an alkaline developer to obtain a signal recording master disc.

After washing this master disc with water, it was treated with a tin chloride sensitizer, and then thoroughly washed with water, treated with a palladium chloride activator, and washed with water. Electroless nickel plating was performed on the thus pretreated master disc using a plating solution having the composition and plating conditions shown in Table 1.

The symbols in the table have the following meanings.

NaTa r : Sodium tartrate Gly nigericin Na0Ac : Sodium acetate NaC1t : Sodium citrate NaPo : Sodium hypophosphite DMAB : Dimethylaminoborane Q Z Z Z Z OZ Z Z Z Oo, The method of the present invention as in the method of the method of the present invention The electroless nickel plating films of A-H obtained by the method did not peel off even when washed under running water, and by subsequent nickel electroplating, defect-free replica disks were obtained. On the other hand, the electroless nickel plating film of the control example FG,
Partial peeling had already occurred when it was taken out of the plating bath, and the peeled portion expanded when washed with water, making it impossible to perform electrolytic nickel plating.

(Effects of the Invention) According to the information recording disk duplication method of the present invention, electroless nickel plating with good adhesion can be performed on the photoresist layer surface in acidic or neutral conditions at low temperature, so that the information signal of the photoresist layer is transformed. This allows you to obtain a faithful copy without having to give up.

Claims (2)

[Claims] (1) When producing a copy disc by recording an information signal on a photoresist layer provided on a disc base, developing it, applying electroless metal plating to the information recording surface, and then forming a metal reinforcing layer, The electroless plating is performed at a rate of 0.05 to 0.15M/
1 of a nickel salt, a chelating agent selected from tartrate, glycine and mixtures thereof, at a molar concentration of at least 1.5 times the concentration of the nickel salt, and hypophosphite or dimethyl. An information recording disk characterized in that the plating is carried out at a temperature of 30 to 60°C using a plating bath containing the required amount of any reducing agent such as aminoborane and adjusted to pH 5.0 to 7.0. Reproduction law. (2) The method for duplicating an information recording disk according to claim 1, wherein the required amount of reducing agent is 10 to 30 g/l of sodium hypophosphite or 2 to 4 g/l of dimethylaminoborane.