JPS6220152A - Stamper for molding optical disk and its manufacture - Google Patents

Abstract

PURPOSE:To form a stamper for molding an optical disk made of plastics which forms a conductive layer on an original board without depending upon a silver mirror reaction by providing an electrocast nickel layer on the electroless nickel plating layer. CONSTITUTION:The stamper for molding the optical disk made of plastics is composed of a conductive layer formed by executing the electroless nickel plating onto the original board for electrocasting to have the irregular information of the submicron order and the track, and the electrocast nickel layer formed by electrocasting on the conductive layer. The thickness of the conductive layer of the electroless nickel plating is generally 800-1,500Angstrom and the thickness of the electrocast nickel layer is amount 300mum. The electrocast nickel layer and the electroless nickel plating layer are mutually strongly linked, it is not necessary to remove the conductive layer after electrocasting, different from the conductive film of Ag due to the conventional silver mirror reaction, and the film can be used as the stamper for molding the plastics as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION (Prior Art) Electroless plating is a well-known method used to form a metal film on an insulator. However, conventional electroless plating is mainly intended to metalize or conductive the surface of an insulating material, and no strict requirements have been placed on the uniformity of the resulting electroless plating film.

However, what about the plastic plates of optical (magnetic) disks that have been attracting attention recently? 2. Description of the Related Art Replica molds, so-called smembers, used in manufacturing by molding, for example casting, injection molding, compression molding, etc., are required to have extremely high surface precision. This stamper is generally produced by electroforming from a master disc that is produced by applying a resist master cloth to a glass master disc, exposing it to a predetermined pattern, curing it, and removing the uncured parts. However, since this resist master disc is an insulator, , it is necessary to form a conductive layer before the electroforming operation. Conventionally, this conductive layer has been formed by a silver mirror reaction, but the silver mirror surface is chemically unstable, oxidizes with oxygen in the air and becomes rough, and its physical strength is weak, so it cannot be used after electroforming. The silver mirror layer had to be removed, resulting in a disadvantage that the surface precision of the stamper surface was reduced. Therefore, there is a strong demand to form a conductive film on the master by electroless plating, which does not need to be removed even after electroforming, due to chemical and physical properties (other than stable silver mirror reaction).

(Object of the Invention) Therefore, an object of the present invention is to provide a stamper for molding a plastic optical disk in which a conductive layer is entirely formed on a master without using a silver mirror reaction.

Still another object of the present invention is to provide a method for forming a conductive layer by electroless nickel plating that does not need to be removed after plating.

(Structure of the Invention) The stamper for molding a plastic optical disk according to the present invention includes a conductive layer formed by electroless nickel plating on an electroforming master having submicron-order unevenness information and tracks, and a conductive layer formed on the conductive layer by electroless nickel plating. It is composed of an electroformed nickel layer formed by electroforming.

The thickness of the conductive layer of the above electroless nickel plating is generally so
o to 1500X, and the thickness of the electroformed nickel layer is about 3
00μ.

The electroformed nickel layer according to the present invention and the electroless nickel plating layer formed thereon are strongly bonded to each other, and unlike the conventional Ag conductive film formed by silver mirror reaction, the conductive layer is removed after electroforming. There is no need to do this, and the stamper can be used as it is as a stamper for plastic molding.

Furthermore, the stamper according to the present invention has excellent stamper transferability to molded products, and the hardness of the surface of the electroless nickel plating layer is much superior to that when silver mirror reaction is used, so the durability of the stamper is improved. Sexuality is greatly improved. The reason for this is unknown, but it is thought that it has something to do with the fact that phosphite is used as a reducing agent in electroless plating.

In other words, the nickel film formed by electroless plating is different from a simple electroformed layer of nickel alone, and is a dense film containing phosphorus. It is thought that the high temperature during this process results in an extremely hard film. Furthermore, since the stamper is a dense film as mentioned above, the surface smoothness of the stamper is excellent, so the C/N of an optical disc made by forming a recording film on a plastic substrate molded from this stamper can be improved. The ratio also improves greatly.

The present invention further relates to a method for manufacturing the stamper.

Conventionally, the plating solution used for electroless nickel plating mainly consists of soluble nickel salt, hypophosphite, and pH buffer solution, and is usually heated to 60°C or higher, for example, 80°C to deposit. Used to increase speed. In order to completely prevent decomposition of the plating solution and obtain a dense plating layer, it is effective to subject the plating solution to acidic conditions.

However, if the plating solution is made under acidic conditions, the deposition rate is slow and the deposition does not start uniformly, making it impossible to form a complete plating layer without uneven plating.

This becomes a serious problem especially when a thin plating layer of about 800 to 2,000× is uniformly formed. Particularly, when nickel chloride is used as the soluble nickel salt, a uniform nickel coating can be obtained from the initial stage of plating, but when disokel sulfate is used, a uniform nickel coating cannot be obtained. The reason for this is unknown, but the special grade reagent nickel sulfate used contains approximately 21)I)m or more of Co, which is thought to have an adverse effect on the formation of a uniform nickel film. It will be done.

That is, the impurity concentration (ppm) in the bath prepared from nickel sulfate and disokel chloride is as follows as a result of atomic absorption spectrometry.

A nickel sulfate bath is preferable because it is safer than a nickel chloride bath, but due to the presence of impurity CO mentioned above, when a nickel sulfate bath is used, a uniform plating layer must be formed from the time of bath construction. I can't. That is, Co f 2.
In the case of a nickel sulfate bath containing 8 ppm, only 15 to 20% of the area to be plated can be electrolessly plated at the time of bath preparation, and the CO is consumed by repeating the plating a total of 20 times, and the CO content becomes o. , s ppm or less, electroless plating can only be applied to 90% of the area to be plated, which is uneconomical.

The present invention solves the above-mentioned drawbacks, and after forming a conductive layer on a master disk for electroforming having uneven information bits and/or tracks, a nickel plating layer is formed by electroforming, and the conductive layer is removed from the master disk. In the method of manufacturing a stamper for plastic optical disc molding by peeling off the nickel electroformed layer, the conductive layer is formed by electroless nickel plating.

The above-mentioned electroless nickel plating is carried out in an electroless nickel plating bath containing soluble nickel salt, hypophosphite, and pH buffer as main components, to which 0.1 to 41) I)m of copper ions are added. Preferably, it is carried out in

The pH of the bath is preferably in the acidic range and the bath temperature is preferably 60°C or less.

As the above-mentioned soluble nickel salt, inorganic salts such as sulfate, hydrochloride, and nitrate are generally used, but it is particularly effective when used with nickel sulfate. The above-mentioned hypophosphite is a reducing agent, and IJum salt is generally used. Above p
As the H buffering agent, organic acids such as acetic acid, citric acid, and co-phosphoric acid and/or their salts, and ammonium salts of inorganic acids such as sulfuric acid and hydrochloric acid are used.As the pH adjusting agent, lactic acid,
Acid 1 and the like are used.

In the present invention, in order to maintain liquid stability, prevent environmental pollution caused by evaporation of the bath liquid, and prevent alkaline corrosion of the plated material, the pH of the bath is maintained at acidic conditions, e.g., pH=6 to 4, and maintained at a relatively low temperature, e.g. It is preferable to carry out the reaction at a temperature of 60°C or lower, preferably 50 to 30°C.

In this respect, the present invention is essentially different from conventional plating methods.

The amount of the above nickel salt is 10 to 10% in terms of metal salt per liter of bath.
609/l, preferably 20-501/l, and hypophosphite 10-30 j9/l, preferably 15-2
The pH buffer is necessary to stabilize the bath at a predetermined pH, and is generally 1 to 50 g/11.

The feature of the present invention is that a trace amount of copper ions is added to the conventional plating solution mainly composed of the above-mentioned nickel salt, phosphite, and pH buffer, and the amount of copper ions added is 0.1. ~
4 ppm, preferably 0.1 to 3 ppm. This amount is 0. If it is less than lppm, a uniform plating layer will not be formed, and if it is less than 4ppm'? Even if it exceeds the limit, a uniform adhesion layer cannot be obtained.

When performing electroless nickel plating, the pretreatment steps commonly used are sensitization, water washing, activation, and water washing. Sensitization can generally be carried out by immersion in an aqueous solution of a reducing metal salt such as stannous chloride and hydrochloric acid, and activation can be carried out by immersion in an aqueous solution of a noble metal salt such as palladium chloride and hydrochloric acid. be able to. When carrying out electroless plating using the electroless plating solution according to the present invention on the hardened resist master disc that has undergone these pre-treatments, it is preferable to perform electroless plating while stirring the bath.

The present invention will be explained below using Examples.

Example (electroless nickel plating) A test sample having a cured resist film was immersed in a known degreasing solution manufactured by Okuno Pharmaceutical Co., Ltd. at room temperature for 5 minutes, and after washing, a sensitizing solution (based mainly on 5nc72 and HCeffi, manufactured by Okuno Pharmaceutical Co., Ltd.) was added. ] for 1 minute, and after washing, soak in the activation solution (pdc4 and H
CII is mainly based on gold. (manufactured by Okuno Pharmaceutical Co., Ltd.) for 1 minute, and was washed for pretreatment.

Next, a plating bath (I) having the following composition was prepared.

Nickel sulfate (using special grade reagent) 26g/I1 Sodium hypophosphite 21 Ammonium chloride 3 Sodium acetate
5 〃Awakening 12 〃
As a result of atomic absorption spectrometry, the content of impurity metals in the bath solution with pH 5.5 immediately after preparation was as follows.

Fe Below detection limit (0.0ppm) Zn Q, lppmco
2.8 〃 Cu Below the detection limit In this plating bath (I), Cu k CuC1z Table 1
After adding at the concentration shown in 41.
The test sample was immersed for 5 minutes while maintaining the bath temperature at ~43°C. The thickness of the obtained electroless nickel plating film was 1.200 to 1,500×0. The results are shown in Table 1.

Note that the plating efficiency and uniformity in Table 1 are based on the following evaluation method.

■] Plating efficiency Deposition rate without adding each additive ion (film thickness 400
2) Relative value when 500X) is taken as 100 2) Ratio of the area of the metallization layer to the total surface area of the uniformity test sample (76X26X1.5).

- As an example, Figure 1 shows the surface condition of the test sample when the addition amount in Table 1 is 0, and the uniformity in this case is 20.
%, and FIG. 2 is a diagram for the case where the addition of -1i in Table 1 is 10.1%, and the uniformity is 100%.

Table 1 As can be seen from Table 1, the properties of the electroless plated film are greatly improved by the addition of Cu ions according to the present invention, and a uniform plated film can be obtained immediately after bath preparation.

Furthermore, in order to investigate the relationship between the effect of the Cu ions of the present invention and the Co ion concentration, we conducted the same experiment as above by adding COCl2 at the time of bath preparation to increase the Co concentration.
By adding Cu ions according to the present invention, it was possible to achieve 100% uniformity from the time of bath construction until the Co concentration was about s ppm.

In order to investigate the reason for the effect of adding Cu ions according to the present invention, tAgcl, which is lower in the ionization series than Cu, was added to CuO, but there was almost no effect.

(Nokel electroforming) Using the same procedure as above, a diameter of 350 mm and a center hole diameter of 7.
2. Apply resist on a 6-thick polished glass plate,
An electroless nickel plating layer was formed on a resist hardened master disc on which a multi-signal focus was formed using a PCM modulated laser beam on a track with a width of 1 μm.

The master plate with the electroless nickel-plated conductive layer obtained in this way is immersed in an electroforming solution and rotated while maintaining an angle of 45° with respect to the vertical plane, so that the electrodeposited surface faces the anode box and a distance of 7 cTL is maintained. It was held and electroformed like this. The composition of the electroforming bath is as follows.

Nickel sulfamate (tetrahydrate) 400g/l
Nickel chloride (hexahydrate) 59/l! teeth
Oxic acid 3
0 i/1 Bit inhibitor 0.5
9/1 The bath temperature was 50° C., and the entire liquid was circulated through a 0.4μ membrane filter storage tank at a cycle of 10 times/hr, so that the liquid was spouted toward the center of the master. In the storage tank? i Electrolytic nickel corrugated cathode and anode bag ki61 are energized with a weak current of 063 A/dm2, impurity ions Ca+, Fe11+・z
The electroforming bath was purified by selectively electrodepositing H, Pb(+, etc.).

An electrolytic nickel pellet was used for the nickel of the anode, and the total current flow was 215 A hrs.The stamper manufactured as above was set in the mold of an injection molding machine to form an optical disc. Although the entire substrate was molded, the durability of the stamper was significantly improved compared to conventional nickel electroforming.

[Brief explanation of the drawings] Figures 1 and 2.2 are examples of the uniformity evaluation method shown in Table 11C, and Figure 1 shows the state of the electroless nickel surface when no Cu ions are added using the conventional method. This is a copy of the photograph shown, the hatched area indicates the plating layer, and the uniformity in this case is 20%.
It is. FIG. 2 is a diagram similar to FIG. 1 in the case of adding Cu ions according to the present invention, and the uniformity in this case is 100 cm. Patent applicant: Daicel Chemical Industries, Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1) An electroless nickel plating layer formed by electroless nickel plating on an electroforming master having uneven information pits and/or tracks, and an electroforming layer formed on this electroless nickel plating layer. A stamper for molding plastic optical discs, consisting of an electroformed nickel layer formed by 2) After forming a conductive layer on an electroforming master having uneven information pits and/or tracks, a nickel plating layer is formed by electroforming, and the conductive layer and nickel electroforming layer are peeled off from the master to form plastic. A method for manufacturing a stamper for molding optical discs, wherein the conductive layer is formed by electroless nickel plating. 3) The electroless nickel plating has a soluble nickel salt,
Claim 2, characterized in that the plating is carried out in an electroless nickel plating bath containing hypophosphite and a pH buffer as main components, to which 0.1 to 4 ppm of copper ions are added.
The method described in section. 4) The method according to claim 2 or 3, wherein the pH of the bath is in the acidic range and the bath temperature is 60° C. or lower. 5) A method according to claim 2, characterized in that the soluble nickel salt is nickel sulfate.