JP2000345266A - Stamper for molding optical disk, and substrate for producing the stamper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of optical disks capable of being injection molded by a piece of molding stamper by producing a molding stamper with an Ni base alloy contg. a specified ratio of Al. SOLUTION: This stamper is produced by an Ni base alloy contg., be weight, 2.5 to 8.0% Al, and the balance Ni with inevitable impurities. The use of an Ni base alloy added with 0.10 to 5.0% Ti is also preferable. The molten metal obtd. by melting an Ni base alloy in a vacuum is cast into a mold and is cast into an ingot, e.g. of 300 mm height, 200 mm width and 2,000 mm length. The ingot is subjected to solution heat treatment at 1,100 deg.C for 5 hr, is thereafter hot-forget at 950 deg.C, is hot-rolled at 900 deg.C and is moreover cold-rolled at ordinary temp. to form into an Ni base alloy sheet material of 1 mm thickness. The Ni base alloy sheet material is held at 920 deg.C for 20 min, is subjected to annealing treatment under water cooling, is held at 590 deg.C for 16 hr, is thereafter cooled in a furnace at 8 deg.C/h, is subjected to heat aging treatment at 480 deg.C for 5 hr, is subsequently cut into a disk of 150 mm and is polished to obtain a substrate for a stamper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamper for manufacturing various optical disks and a substrate for manufacturing the stamper.

[0002]

2. Description of the Related Art In recent years, optical disks have been actively manufactured as optical recording media capable of storing information at high density.
These optical discs have a write-once medium, a phase change medium,
Alternatively, it is manufactured by forming a recording film such as a magneto-optical recording medium and then forming a protective film. Information is recorded on either a land or a groove of an optical disk, and an optical disk having these lands and grooves is usually made of a thermoplastic resin formed of a metal matrix (hereinafter referred to as a metal stamper) on which information signals of minute irregularities are formed. ) Is injected at a high temperature into a mold in which lands have been set, and lands and grooves are formed by transferring the fine irregularities of the metal stamper to the surface of the thermoplastic resin, followed by cooling and curing. Conventionally, the metal stamper has been manufactured by an electroforming method.However, the production of the metal stamper by this method requires a large electroforming apparatus, and further requires power distribution equipment and a large clean room for obtaining a larger power. Further, after electroforming, a post-process such as trimming, polishing, and punching of the inner and outer periphery of the stamper is required.

Therefore, in recent years, the production of metal stampers by the dry etching method of irradiating the surface of a metal substrate with Ar ions for etching has been actively performed. This dry etching method of irradiating with Ar ions is generally called an ion milling method. A method of manufacturing a metal stamper by this ion milling method is shown in FIG.
This will be described with reference to cross-sectional views (a) to (f). First, FIG.
A metal substrate 1 shown in (a) is prepared. The metal substrate 1 is a stainless steel (for example, SUS303) or Ni metal plate. On this metal substrate 1, FIG.
A photoresist is applied to form a photoresist layer 2 as shown in FIG. Next, as shown in FIG. 1 (c), the photoresist layer 2 is irradiated with a laser beam (Ar laser beam) corresponding to information to record and expose the photoresist layer 2, and the exposed resist layer 21 and the non-exposed resist are exposed. Layer 2
2 is formed. The recorded and exposed photoresist layer 2 is developed and processed as shown in FIG.
As shown in FIG. 3, the non-exposed resist layer 22 is removed, and the exposed resist layer 21 is left on the surface of the metal substrate 1 to remove the metal substrate 1.
To expose a part of the surface. When the metal substrate 1 with the partially exposed surface is irradiated with Ar ions, the portion of the metal substrate 1 where the partial surface is exposed is etched to form a concave portion 3 as shown in FIG. By removing the exposure resist layer 21, a metal stamper 5 having a convex portion 4 and a concave portion 3 as shown in FIG. Forming or cutting a concave portion by irradiating the metal substrate 1 with Ar ions for etching is generally called ion milling.

A metal plate made of stainless steel (for example, SUS303) or Ni is used as the metal substrate 1. However, a metal stamper made of a stainless steel plate is irradiated with Ar ions due to the large thermal expansion coefficient of stainless steel. When the ion milling is performed, the stainless steel plate is heated and greatly expanded, so that there is a disadvantage that a concave portion and a convex portion having accurate dimensions cannot be formed. Therefore, at present, N has a smaller coefficient of thermal expansion than the stainless steel plate.
A metal stamper made of an i-plate is often used.

[0005]

In recent years, information stored on an optical disk has been required to have higher density and higher accuracy, and on the other hand, there has been a demand for a reduction in the manufacturing cost of the optical disk. For this reason, it is required that the shapes of the lands and grooves of the optical disk be formed more precisely, and that more optical disks be injection-molded with one metal stamper. In response to such demands, since Ni has a relatively small coefficient of thermal expansion, a metal stamper made of a Ni plate has concaves and convexes of accurate dimensions, but Ni
Since the hardness is generally low and the hardness cannot be sufficiently increased even by processing or heat treatment, injection molding of an optical disc using a metal stamper made of a Ni plate causes an increase in the number of manufactured optical discs. The ends of the concave and convex portions of the metal stamper are worn, and the accuracy of the lands and grooves formed on the optical disc is reduced.
Therefore, it is said that the number of optical disk disks that can be injection-molded using a metal stamper made of a Ni plate is limited to 50,000. However, there is a disadvantage that the cost is increased because the number of sheets manufactured cannot be increased.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the problems of the conventional metal stamper, and as a result,
(A) Ni in which 2.5 to 8.0% by weight of Al is added to Ni
The base alloy can be increased in hardness by plastic working and heat treatment, and has a coefficient of thermal expansion almost as low as Ni,
Further, since the mold releasability is improved, when an optical disk is manufactured using a metal stamper made of the Ni-based alloy plate containing Al, the number of optical disks that can be injection-molded using one metal stamper is greatly increased. be able to,
(B) A Ni-based alloy obtained by adding 2.5 to 8.0% by weight of Al to Ni and further adding 0.10 to 5.0% by weight of Ti has high hardness, low coefficient of thermal expansion, and injection molding. It has been found that it is more preferable because the releasability of the obtained resin is improved.

The present invention has been made based on such findings, and (1) Al: 2.5 to
An optical disk molding stamper containing 8.0% and a balance of Ni-based alloy having a composition of Ni and unavoidable impurities, (2) Al: 2.5 to 8.0% by weight.
%, Ti: 0.10 to 5.0%, and the balance is characterized by an optical disk molding stamper made of a Ni-based alloy having a composition of Ni and unavoidable impurities.

The stamper for molding an optical disk according to the above (1) or (2) contains 2.5 to 8.0% of Al.
N with the balance being Ni and unavoidable impurities
i-based alloy plate, and Al: 2.5 to 8.0%, Ti:
0.10-5.0%, the balance being made from a Ni-based alloy plate having a composition consisting of Ni and unavoidable impurities,
The present invention also includes a Ni-based alloy plate having the composition described in the above (1) and (2).

Accordingly, the present invention is characterized in a stamper manufacturing substrate comprising the Ni-based alloy according to the above (1) and (2).

Next, the reasons for limiting each element in the alloy composition of the optical disk molding stamper made of the Ni-based alloy of the present invention and the substrate for manufacturing the stamper will be described in detail.

Al Al is contained because the heat treatment makes it possible to increase the hardness by uniformly dispersing very fine precipitates in the Ni alloy base material and further has the effect of improving the mold release of the resin. However, if the content is less than 2.5%, the content is insufficient, and if it exceeds 8.0%, the workability is undesirably reduced. Therefore, the content of Al is determined to be 2.5 to 8.0%. A more preferable range of the Al content is 4.0 to 5.0%.

Ti Ti acts to increase the hardness by uniformly dispersing very fine precipitates in the Ni alloy base by synergistic action with Al by heat treatment, and further to enhance the mold releasability of the injection molded resin. Is contained as necessary, but if the content is less than 0.10%, it is insufficient, while 5.0%
%, It is not preferable because the processability decreases. Therefore, the content of Ti is set to 0.10 to 5.0%.

The unavoidable impurities of the Ni-based alloy constituting the optical disk molding stamper of the present invention are Fe: 2.
Preferably, it is less than 0%, C: less than 0.01%, and S: less than 0.01%.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A Ni-based alloy having the component composition shown in Table 1 is vacuum-melted, and the obtained molten metal is cast into a mold, and the length: 300 mm, the width: 200 mm, and the length: 2000 m
m ingot and cast the resulting ingot at a temperature of:
After the solution heat treatment at 1100 ° C. for 5 hours, hot forging is further performed at a temperature of 950 ° C., and then a temperature of 900 ° C.
, And cold-rolled at room temperature to form a Ni-based alloy sheet having a thickness of 1 mm. This Ni-based alloy sheet is kept at a temperature of 920 ° C. for 20 minutes, subjected to a water-cooled annealing treatment, further kept at a temperature of 590 ° C. for 16 hours, and then cooled in a furnace at a rate of 8 ° C./h.
An aging heat treatment was performed at 480 ° C. for 5 hours.

A disk having a diameter of 150 mm is cut out from the Ni-based alloy plate material thus obtained, and both sides of the disk are wrapped with a double-sided grindstone lapping machine.
Polish only the surface with a single-side polishing machine, Rmax:
A stamper substrate was manufactured by finishing the mirror surface to 0.02 μm or less. Further, a stamper substrate having a mirror finish of Rmax: 0.02 μm or less was similarly manufactured from a pure Ni plate having a thickness of 1 mm.

A photoresist layer was uniformly coated on the surface of the stamper substrate to a thickness of 0.4 μm.
The photoresist layer is exposed by irradiating an Ar laser beam corresponding to information to be recorded from above the photoresist layer, and is developed to remove the photoresist layer other than the region irradiated with the Ar laser beam. After exposing a part of the film, baking was performed.

In this manner, Ar ions are irradiated from above the stamper substrate having a part of the substrate surface exposed and having the remaining photoresist layer on the substrate surface, and ion milling is performed using the remaining photoresist layer as a mask. After forming a concave portion having a depth of 0.1 μm on the surface of the substrate for use, the remaining photoresist layer was removed to manufacture Stampers 1 to 8 of the present invention and Conventional Stamper 1.

The stamper 1 of the present invention thus obtained
To 8 and the conventional stamper 1 were set in a mold of an injection molding machine for an optical disc, and 100,000 optical discs were produced by injection molding a polycarbonate resin. Forming a silicon nitride (Si ₃ N ₄ ) dielectric layer, a TbFeCo magneto-optical recording layer, and a silicon nitride (Si ₃ N ₄ ) dielectric layer in this order on the surface of the last 100,000-th optical disk; The optical disk was produced by the following.

The optical disk manufactured in this manner is guided under the following conditions: wavelength: 830 nm, NA: 0.55, vignetting coefficient: 0.1, wavefront aberration: 0.03λ (rms value), deflection state: linearly polarized light. The signal was reproduced by a pickup in a direction parallel to the groove, the reflected light amount signal output was input to a spectrum analyzer, and the noise level of the land portion and the groove portion was measured. The results are shown in Table 1.

[0020]

[Table 1]

From the results shown in Table 1, it can be seen that the land and groove portions of an optical disk in which a dielectric layer and a magneto-optical recording layer were respectively applied to the 100,000-th optical disk disk manufactured using the stampers 1 to 8 of the present invention. The noise level was lower than the noise level of the land and groove portions of the optical disk in which the dielectric layer and the magneto-optical recording layer were applied to the 100,000th optical disk manufactured using the conventional stamper 1. The stampers 1 to 8 of the present invention made of a Ni-based alloy shown in (1) can produce much more optical discs than the conventional stamper 1 made of pure Ni.

[0022]

As described above, the optical disk molding stamper of the present invention can reduce the unit price of the optical disk disk because it can manufacture optical disk disks having lands and grooves with accurate dimensions in larger quantities than before. The present invention can reduce the cost of an optical disk obtained by coating a dielectric layer and a magneto-optical recording layer on an optical disk, and can greatly contribute to the development of the optical recording medium industry.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a conventional method for manufacturing a metal stamper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal substrate 2 Photoresist layer 21 Exposed resist layer 22 Non-exposed resist layer 3 Concave part 4 Convex part 5 Metal stamper

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hironori Ueno 1230 Kamideya, Okegawa-shi, Saitama Prefecture Mitsubishi Materials Corporation (72) Inventor Kimiaki Kato 1230 Kamideya, Okegawa-shi, Saitama Mitsubishi Materials Corporation Inside the Okegawa Works (72) Inventor Takashi Sasaki 1230 Kamideya, Okegawa City, Saitama Prefecture Mitsubishi Materials Corp.Okegawa Works (72) Inventor Takumi Shibuya 1230, Kamideya, Okegawa City, Saitama Prefecture Mitsubishi Materials Corporation Terms (Reference) 5D121 AA02 CA07 GG04 GG07 GG22

Claims (3)

[Claims] 1. A stamper for molding an optical disk, characterized in that it contains 2.5 to 8.0% of Al by weight and the balance is made of a Ni-based alloy having a composition of Ni and unavoidable impurities. 2. Al: 2.5-8.0% by weight, T
i: a stamper for molding an optical disk, characterized in that it contains 0.10 to 5.0% and the balance consists of a Ni-based alloy having a composition of Ni and unavoidable impurities. 3. A stamper manufacturing substrate comprising the Ni-based alloy according to claim 1 or 2.