JP2000348395A - Stamper for molding optical disc and substrate for manufacturing the stamper - Google Patents

Abstract

(57) [Problem] To provide a stamper for molding an optical disc and a substrate for manufacturing the stamper. An optical disk forming stamper made of polycrystalline metal having a directionally solidified structure and a substrate for manufacturing the stamper are provided.

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-processing step 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. The 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. 3C, the photoresist layer 2 is irradiated with a laser beam (Ar laser beam) corresponding to the 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 subjected to a development treatment to obtain a photoresist layer 2 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 having 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 the 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.

[0004]

In recent years, information stored on optical discs has become more and more dense, and an optical disc having high-density information built therein has more fine and precise lands and grooves. An optical disk is required. To manufacture a high-precision optical disk having finer and more precise lands and grooves, it is necessary to use a metal stamper having finer concave and convex portions formed on the surface thereof with higher dimensional accuracy. However, since the conventional stainless steel plate or Ni plate cannot form a metal stamper having fine concave portions and convex portions with sufficiently high precision, the above requirements cannot be sufficiently satisfied.

[0005]

The inventors of the present invention have conducted intensive studies to obtain a metal stamper having irregularities with higher precision than the conventional metal stamper, and as a result, the crystal orientation was aligned with the crystal growth direction. It has been found that a stamper for molding an optical disc made of a polycrystalline metal plate having a unidirectional solidification structure has higher precision than a stamper for molding an optical disc made of a normal rolled metal plate.

The present invention has been made based on such findings, and is characterized by (1) a stamper for molding an optical disk made of a polycrystalline metal having a unidirectionally solidified structure.

The polycrystalline metal having a unidirectionally solidified structure constituting the stamper for forming an optical disk has a sufficient hardness which is not easily corroded and is not deformed by high-temperature injection molding of a resin. Any metal or alloy may be used as long as the metal or alloy is small.
However, considering corrosion resistance, coefficient of thermal expansion and hardness,
It is preferable to use pure Ni or a Ni-based alloy, pure Co or a Co-based alloy, or an Fe-based alloy having excellent corrosion resistance.

Accordingly, the present invention provides (2) a stamper for molding an optical disk made of polycrystalline pure Ni or a Ni-based alloy having a unidirectionally solidified structure, and (3) polycrystalline pure Co or a Co-based alloy having a unidirectionally solidified structure. And (4) an optical disk forming stamper made of a polycrystalline Fe-based alloy having a unidirectionally solidified structure having excellent corrosion resistance.

As a material for a stamper for molding an optical disc,
Polycrystalline pure Ni having the unidirectionally solidified structure is more preferable than pure Ni having a rolled polycrystalline structure.
Further, a polycrystalline Ni-based alloy having a unidirectionally solidified structure is more preferable than a polycrystalline pure Ni having a unidirectionally solidified structure,
Among the Ni-based alloys, Mo: 10.0 to 100% by weight.
Ni-based alloy containing 30.0% and a balance of Ni and unavoidable impurities, Mo: 10.0 to 3
0.0%, Cr: 3.0 to 25.0%, the balance is a Ni-based alloy having a composition consisting of Ni and inevitable impurities, Al: 2.5 to 8.0%, the balance being Ni-based alloy having a composition consisting of Ni and unavoidable impurities, A
1: 2.5 to 8.0%, Ti: 0.5 to 5.0%, and the balance of the Ni-based alloy having the composition of Ni and unavoidable impurities is low in both thermal expansion coefficient and hardness. More preferred because it can be increased,

Therefore, the present invention relates to (5)
And Mo: 10.0 to 30.0%, with the balance being Ni
And an optical disk molding stamper made of a polycrystalline Ni-based alloy having a composition of unavoidable impurities and having a unidirectional solidification structure, (6) by weight, Mo: 10.0 to 30.
0%, Cr: 3.0 to 25.0%, the balance being Ni
And a stamper for molding an optical disk made of a polycrystalline Ni-based alloy having a composition consisting of unavoidable impurities and having a unidirectional solidification structure, (7) wt%, Al: 2.5-8.0%
The stamper for molding an optical disk comprising a polycrystalline Ni-based alloy having a composition consisting of Ni and unavoidable impurities and having a unidirectionally solidified structure, the balance being (8) A
1: 2.5 to 8.0%, Ti: 0.5 to 5.0%, the balance being a polycrystalline Ni-based alloy having a composition consisting of Ni and unavoidable impurities and having a directionally solidified structure. The optical disk molding stamper is characterized in that:

An optical disk molding stamper made of polycrystalline pure Co having a unidirectionally solidified structure and a polycrystalline Co-based alloy having a unidirectionally solidified structure both have excellent characteristics. In particular by weight% Ni:
A Co-based alloy containing 5 to 30%, Cr: 10 to 30%, and W: 3 to 20%, and having a composition consisting of the balance Co and inevitable impurities is preferable. Therefore, the present invention
(9) Ni: 5 to 30%, Cr: 10 to 30% by weight
%, W: 3 to 20%, and has a characteristic feature of an optical disc molding stamper made of a polycrystalline Co-based alloy having a composition of Co and inevitable impurities and having a unidirectional solidification structure.

As the material of the stamper for molding an optical disc of the Fe system, a polycrystalline Fe-based alloy having a unidirectionally solidified structure having excellent corrosion resistance is preferable. Among the Fe-based alloys, Cr: 10 to 35% by weight is contained. And an Fe-based alloy having a composition comprising the balance of Fe and unavoidable impurities, Cr: 10 to 3
Fe-based alloy containing 5%, Mo: 0.2 to 10%, and having the balance of Fe and inevitable impurities, Cr:
Fe-based alloy containing 10 to 35%, Ni: 2 to 8%, and having a balance of Fe and unavoidable impurities, C
r: 10 to 35%, Ni: 2 to 8%, Mo: 0.2 to 1
More preferably, it is an Fe-based alloy containing 0% and having a composition comprising the balance of Fe and unavoidable impurities.

Therefore, the present invention provides (10) a polycrystalline Fe-based alloy containing 10 to 35% by weight of Cr, having a composition comprising the balance of Fe and unavoidable impurities and having a directionally solidified structure. Stamper for optical disk molding,
(11) For forming an optical disk comprising a polycrystalline Fe-based alloy containing Cr: 10 to 35% and Mo: 0.2 to 10%, having a composition of balance of Fe and unavoidable impurities and having a directionally solidified structure. Stamper, (12) Cr: 10-35
%, Ni: 2 to 8%, and a stamper for molding an optical disc made of a polycrystalline Fe-based alloy having a composition of balance of Fe and inevitable impurities and having a unidirectional solidification structure,
(13) Cr: 10 to 35%, Ni: 2 to 8%, Mo:
A stamper for molding an optical disk comprising a polycrystalline Fe-based alloy having a composition of 0.2 to 10%, a balance of Fe and unavoidable impurities, and having a unidirectionally solidified structure.

According to the present invention, there is provided a stamper for forming an optical disk comprising a polycrystalline metal having a unidirectionally solidified structure.
(13) It is made from a substrate made of a polycrystalline metal having a directionally solidified structure according to (13), and the present invention also includes the substrate. Therefore, the present invention is characterized by (14) a stamper manufacturing substrate made of a polycrystalline metal having a composition according to any one of the above (1) to (13) and having a directionally solidified structure. Things.

When a stamper for molding an optical disk is made of a polycrystalline metal having a unidirectionally solidified structure, a reason why a stamper having unevenness with excellent dimensional accuracy can be obtained is considered to be that the etching directionality becomes uniform. Next, the stamper for molding an optical disk made of a polycrystalline metal having a unidirectionally solidified structure of the present invention and the reason for limiting each element in the alloy composition of a substrate for manufacturing the stamper will be described in detail.

(A) Ni-based alloy Mo Mo forms a solid solution in a Ni base material and lowers the coefficient of thermal expansion.
Further, it is contained because it has an effect of improving the mold release of the resin, but if the content is less than 10.0%, it is insufficient.
On the other hand, if it exceeds 30.0%, the hardness of the alloy becomes non-uniform, and as a result, the etching shape by ion milling becomes non-uniform, which is not preferable. Therefore, M
The content of o was set to 10.0 to 30.0%. A more preferred range of the Mo content is 23.0 to 28.0%.

Cr Cr has the effect of making the hardness distribution of a Ni-based alloy containing Mo: 10.0 to 30.0% more uniform, so that Cr is contained as necessary. If it is less than 0%, it is insufficient. On the other hand, if it exceeds 25.0%, the toughness is reduced, and the edges (corners) of the irregularities of the stamper may be chipped at the time of injection molding of the resin. It is not preferable because it causes a change. Therefore, the content of Cr is set to 3.0 to 25.0%.

Al Al is contained because it has the effect of uniformly dispersing very fine precipitates in a Ni-base alloy base material by heat treatment to increase the hardness and has the effect of improving the mold release of the resin. However, if the content is less than 2.5%, it is not sufficient. On the other hand, if it is added more than 8.0%, flaws called peeling are likely to occur when the surface is polished, which is not preferable. Therefore, the content of Al is 2.5 to
It was set to 8.0%. A more preferable range of the Al content is 4.
0 to 5.0%.

Ti Ti increases the hardness by uniformly dispersing very fine precipitates in the Ni-based alloy base material by a synergistic effect with Al by heat treatment, and further increases the releasability of the injection-molded resin. Since it has an effect, it is contained as needed, but if its content is less than 0.5%, it is insufficient, while 5.0%
%, It is not preferable because flaws called peeling tend to occur when the surface is polished. Therefore, the content of Ti is set to 0.5 to 8.0%.

(B) Co-base alloy Ni Ni is dissolved in the base material of the Co-base alloy to reduce the coefficient of thermal expansion and to improve the ion milling property. If it is less than 5.0%, it is not sufficient. On the other hand, if it exceeds 30.0%, the hardness is lowered, and the life of the stamper is undesirably shortened. Therefore, the content of Ni is 5.0 to 30.0.
%. A more preferred range of the Ni content is 21.
0 to 23.0%.

Cr Cr is contained because it has a function of making the hardness distribution of the Co-based alloy more uniform, but if the content is less than 10.0%, it is insufficient. If added, the toughness is reduced, and the ends (corners) of the irregularities of the stamper may be chipped during the resin injection molding, which may change the shape of the stamper, which is not preferable. Therefore,
The content of Cr was set to 10.0 to 30.0%. A more preferable range of the Cr content is 21.0 to 23.0%.

WW has the effect of forming a solid solution in the Co-based alloy base material, lowering the coefficient of thermal expansion, reducing the dimensional change of the stamper during ion milling, and improving the mold release of the injection molded resin. It is contained because it has % Is insufficient, while adding more than 20.0% is not preferable because the hardness distribution in the alloy becomes non-uniform, and as a result, the etched shape by ion milling becomes non-uniform. Therefore, the content of W is set to 3.0 to 20.0%. A more preferred range of the W content is 13.0 to 1
6.0%

(C) Fe-based alloy Cr Cr is added because it has an effect of lowering the coefficient of thermal expansion of the Fe-based alloy, but if its content is less than 10.0%, it is insufficient. Addition of more than 0% is not preferable because the toughness is reduced and ends (corners) of the irregularities of the stamper may be chipped at the time of injection molding of the resin, causing a change in the shape of the stamper. Therefore, Cr
Was set to 10.0 to 35.0%. A more preferable range of the Cr content is 15.0 to 20.0%.

Mo Mo has a function of improving the thermal expansion coefficient by dissolving in the Fe-based alloy base material and further improving the mold release of the injection-molded resin. 0.2
% Is insufficient, while if added over 10.0%, the toughness is reduced, and the edges (corners) of the irregularities of the stamper may be chipped during resin injection molding, resulting in a change in the shape of the stamper. This is not desirable because it causes Therefore, the content of Mo is set to 0.2 to 10.0%.

Ni Ni is contained as necessary because it has an effect of improving ion milling properties. However, if its content is less than 20%, it is insufficient. On the other hand, if it exceeds 8.0%, thermal expansion will occur. This has the effect of increasing the coefficient and degrades the dimensional accuracy of the stamper, which is not preferable. Therefore, the content of Ni is set to 5.0 to 30.0%.

The stamper for molding an optical disk made of a polycrystalline metal having a unidirectionally solidified structure according to the present invention is made of a substrate made of a polycrystalline metal having a unidirectionally solidified structure.
An example of a method for manufacturing a substrate made of a polycrystalline metal having a unidirectional solidification structure will be described below.

First, as shown in the sectional view of FIG. 2, the mold 10 is placed on a cooling plate 11 and a molten metal (pure metal or alloy) is poured into the mold 10. The poured molten metal starts to solidify from the part in contact with the cooling plate 11 and solidifies in the direction shown by the arrow to obtain a polycrystalline metal ingot having a unidirectional solidification structure.

The thus obtained polycrystalline metal ingot having a unidirectionally solidified structure is shown in the perspective view of FIG. In FIG. 1, reference numeral 6 denotes a polycrystalline metal ingot having a unidirectionally solidified structure, 7 denotes a slice line, and the slice line is indicated by a dotted line. Reference numeral 8 denotes a polycrystalline metal plate having a unidirectionally solidified structure obtained by slicing a polycrystalline metal ingot 6 having a unidirectionally solidified structure along a slice line 7. The polycrystalline metal plate 8 having the unidirectional solidification structure is cut into a predetermined size to prepare a substrate, which is then cut into the metal substrate 1 shown in FIG.
Then, an optical disk molding stamper 5 is manufactured by a usual method.

When the polycrystalline metal ingot 6 having the directionally solidified structure is sliced along the slicing line 7,
Although the angle of the slice with respect to the crystal growth direction is not particularly limited, it is most preferable that the slice is perpendicular to the crystal growth direction, and therefore,
Most preferred is an optical disk molding stamper made from a polycrystalline metal plate having a unidirectionally solidified structure obtained by slicing at right angles to the crystal growth direction. Accordingly, the present invention provides (15) a disk for forming a disk made of a polycrystalline metal having a composition according to any one of the above (1) to (13) and having a unidirectionally solidified structure grown in the thickness direction. A stamper, (16) a stamper manufacturing substrate made of a polycrystalline metal having a composition according to any one of the above (1) to (13) and having a unidirectionally solidified structure grown in a thickness direction. It has.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Pure Ni and a Ni-based alloy having the compositions shown in Table 1 were melted using a conventional vacuum melting furnace, and the resulting molten metal was heated to a temperature of 15 ° C.
At 70 ° C, inner diameter: 150 mm, outer diameter: 170 mm, height:
Cast into a mold 10 shown in FIG. 2 having a dimension of 250 mm to produce an ingot 6 of polycrystalline pure Ni having a unidirectionally solidified structure and a polycrystalline Ni-based alloy having a unidirectionally solidified structure of the shape shown in FIG. Then, the polycrystalline pure Ni and the Ni-based alloy ingot 6 having the unidirectionally solidified structure are sliced to obtain a polycrystalline pure Ni plate having a unidirectionally solidified structure having an outer diameter of 150 mm and a thickness of 1 mm. A polycrystalline Ni-based alloy plate having a solidified structure was produced. When the orientation of each crystal in each plate was measured by the X-ray method, it was confirmed that all the orientations were 001.

From the thus obtained polycrystalline pure Ni plate having a unidirectionally solidified structure and a polycrystalline Ni-based alloy plate having a unidirectionally solidified structure, a disk having a diameter of 150 mm is cut out. Both surfaces were wrapped with a double-sided grindstone lapping machine, and then only the surface was polished with a single-side polishing machine, and finished to a mirror surface with an Rmax of 0.02 μm or less, to produce a substrate for stamper production.

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

The stamper substrate having a part of the substrate surface exposed and having a remaining photoresist layer on the surface of the substrate is irradiated with Ar ions, and ion milling is performed using the remaining photoresist layer as a mask. A polycrystalline metal stamper having a unidirectionally solidified structure of the present invention (hereinafter, referred to as a polycrystalline metal stamper of the present invention) 1 is formed by forming a concave portion having a depth of 0.1 μm on the surface and then removing the remaining photoresist layer. ~ 9 were produced.

Conventional Example 1 For comparison, the pure Ni melt prepared in Example 1 was heated at the following temperature:
Length: 250 mm, width: 1550 ° C by a normal casting method
Pure Ni with dimensions of 200 mm, height: 2000 mm
An ingot is produced, this ingot is rolled, and a thickness of the obtained ingot is rolled. A disk having a diameter of 150 mm is cut out from a rolled plate having a dimension of 1 mm. After lapping, only the surface is polished with a single-side polishing machine, and Rmax: 0.0
A substrate for manufacturing a stamper was manufactured by finishing the mirror surface to 2 μm or less. A conventional stamper 1 was manufactured in the same manner as in Example 1 using this stamper manufacturing substrate.

The polycrystalline metal stampers 1 to 9 of the present invention prepared in Example 1 and the conventional stamper 1 prepared in Conventional Example 1 were set in a mold of an injection molding machine, and a polycarbonate resin was injection molded to form an optical disk. Produced. Silicon nitride (Si ₃ N ₄ ) was applied on the surface of the obtained optical disc, respectively.
An optical disk was manufactured by forming a dielectric layer, a TbFeCo magneto-optical recording layer, and a silicon nitride (Si ₃ N ₄ ) dielectric layer in this order.

The optical disk manufactured as described above is guided under the following conditions: wavelength: 830 nm, NA: 0.55, vignetting coefficient: 0.1, wavefront aberration: 0.03λ (rms value), and 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.

[0037]

[Table 1]

From the results shown in Table 1, the noise level of the land portion and groove portion of the optical disk obtained by applying the dielectric layer and the magneto-optical recording layer to the optical disk disk manufactured by using the polycrystalline metal stampers 1 to 9 of the present invention is shown. The noise level of the land portion and the groove portion of an optical disk obtained by applying a dielectric layer and a magneto-optical recording layer to an optical disk made by using a conventional stamper 1 made of a pure Ni rolled plate is lower than the noise level of the polycrystal of the present invention. It can be seen that the metal stampers 1 to 9 can manufacture an optical disk with higher precision than the conventional stamper 1.

Example 2 Pure Co and a Co-based alloy having the component compositions shown in Table 2 were prepared, and these Co-based alloys were melted and cast in the same manner as in Example 1 to obtain a polycrystal having a directionally solidified structure. An ingot of pure Co and a polycrystalline Co-based alloy having a unidirectional solidification structure was prepared, and the ingot was sliced in the same manner as in Example 1 to obtain a unidirectional solidification structure having an outer diameter of 150 mm and a thickness of 1 mm. And a polycrystalline Co-based alloy plate having a unidirectionally solidified structure. A stamper manufacturing substrate was prepared from the polycrystalline pure Co plate having a unidirectionally solidified structure and the polycrystalline Co-based alloy plate having a unidirectional solidified structure in the same manner as in Example 1. In the same manner as in the above, polycrystalline metal stampers 10 to 18 of the present invention were produced. Using these polycrystalline metal stampers 10 to 18 of the present invention, optical disks were produced in the same manner as in Example 1, and the noise levels of the lands and grooves of the obtained optical disks were measured by the same method as described above. Is shown in Table 2.

[0040]

[Table 2]

The polycrystalline metal stampers 10-1 of the present invention shown in Table 2
The noise level of the land portion and the groove portion of the optical disk prepared by applying the dielectric layer and the magneto-optical recording layer to the optical disk manufactured by using the conventional stamper 1 is shown in Table 1. Since the noise level of the land portion and the groove portion of the optical disk coated with the magneto-optical recording layer is lower than the noise level of the land portion and the groove portion, the polycrystalline metal stampers 10 to 18 of the present invention can produce an excellent optical disk with higher precision than the conventional stamper 1. I understand.

Example 3 Fe-based alloys having the component compositions shown in Table 3 were prepared, and these Fe-based alloys were melted and cast in the same manner as in Example 1 to obtain a polycrystalline Co-based alloy having a directionally solidified structure. An ingot was prepared, and the ingot was sliced in the same manner as in Example 1 to prepare a polycrystalline Fe-based alloy plate having a unidirectionally solidified structure having an outer diameter of 150 mm and a thickness of 1 mm.
A substrate for producing a stamper was produced from the polycrystalline Fe-based alloy plate having these unidirectional solidification structures in the same manner as in Example 1, and the polycrystalline metal stampers 19 to 19 of the present invention were produced from this substrate for producing a stamper in the same manner as in Example 1. 27 were produced. Using these polycrystalline metal stampers 19 to 27 of the present invention, optical disks were produced in the same manner as in Example 1, and the noise levels of the lands and grooves of the obtained optical disks were measured by the same method as described above. Are shown in Table 3.

[0043]

[Table 3]

The noise levels of the lands and grooves of the optical disk manufactured by using the polycrystalline metal stampers 19 to 27 of the present invention shown in Table 3 are shown in Table 1. It can be seen from the fact that the polycrystalline metal stampers 19 to 27 of the present invention can produce an excellent optical disk with higher precision than the conventional stamper, because the noise level is lower than the noise level of the part.

[0045]

As described above, the optical disk molding stamper of the present invention can contribute to the development of the optical recording medium industry because it can manufacture an optical disk having lands and grooves with high precision.

[Brief description of the drawings]

FIG. 1 is a perspective view of a polycrystalline metal ingot having a directionally solidified structure and a plate obtained by slicing the ingot.

FIG. 2 is a cross-sectional view of a mold for producing a polycrystalline metal ingot having a directionally solidified structure.

FIG. 3 is a cross-sectional view for explaining a conventional method of manufacturing a metal stamper.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal substrate 2 photoresist layer 3 concave portion 4 convex portion 5 metal stamper 6 polycrystalline metal ingot having unidirectional solidification structure 7 slice line 8 polycrystalline metal plate having unidirectional solidification structure 10 mold 11 cooling plate 21 exposure resist layer 22 Non-exposed resist layer

 ──────────────────────────────────────────────────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 In Okegawa Works (72) Inventor Takashi Sasaki 1230 Kamijiya, Okegawa City, Saitama Prefecture Mitsubishi Materials Corporation (72) Inventor Takumi Shibuya 1230 Kamijiya, Okegawa City, Saitama Prefecture Mitsubishi Materials Corporation Okegawa Works ( 72) Inventor Akira Mitsuhashi 1230 Kamideya, Okegawa-shi, Saitama F-term (reference) 5D121 CA07 in Otegawa Works, Mitsubishi Materials Corporation

Claims (5)

[Claims] 1. A stamper for molding an optical disk, comprising a polycrystalline metal having a unidirectional solidification structure. 2. A stamper for molding an optical disk, comprising a polycrystalline metal having a unidirectionally solidified structure grown in a thickness direction. 3. The polycrystalline metal having a unidirectionally solidified structure is polycrystalline pure Ni having a unidirectionally solidified structure or a polycrystalline Ni-based alloy having a unidirectionally solidified structure. 2. The stamper for molding an optical disc according to 2. 4. The polycrystalline metal having a unidirectional solidification structure is polycrystalline pure Co having a unidirectional solidification structure or a polycrystalline Co-based alloy having a unidirectional solidification structure. 2. The stamper for molding an optical disc according to 2. 5. The stamper according to claim 1, wherein the polycrystalline metal having a unidirectionally solidified structure is a polycrystalline Fe-based alloy having a unidirectionally solidified structure.