JP2000048365A - Master disk of optical disk and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the output of a reading signal by applying a photosensitive resin contg. a coloring material that absorbs light of a wavelength used for pit exposure and irradiating the resin with laser light corresponding to a pit signal and laser light for groove formation. SOLUTION: A glass master disk 11 is polished to have a prescribed thickness and a prescribed surface roughness and cleaning is carried out by primer treatment or other method. A photoresist is applied so as to have a uniform thickness and hardened by prebaking to form a photoresist layer 12. A metallic film 14 that imparts electric conductivity is formed on the photoresist layer 12 and the rear side of the resultant stamper 16 is polished to obtain a completed stamper. The photoresist is a photosensitive resin contg. a coloring material that absorbs light of a wavelength used for pit and groove exposure and the photoresist is used as a coating fluid. The photosensitive resin consists, e.g. of phenol and a diazonium salt or an azido compd. as a sensitizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a master optical disc and a method for manufacturing the same. More specifically, the present invention relates to an optical disk master capable of manufacturing an optical disk capable of obtaining a read signal faithful to an input signal, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Exposure of a master optical disc is performed by irradiating a glass plate coated with a photosensitive material with a laser beam for recording a pit signal and a laser beam for forming a groove, and then developing the light. The melted portion is dissolved, and pits and grooves are formed as depressions. The presence / absence and size of this pit and groove
It is determined by modulating a laser beam by an acousto-optic modulator or an electro-optic modulator. It is required that pits and grooves be formed with high precision due to the recent increase in the density of optical disks.

However, in the production of an optical disc master,
When exposing the pit and the groove, at the position where the pit and the groove are adjacent, the groove (groove) is formed due to the overlap of the pit forming exposure light and the groove forming exposure light at the time of exposure.
However, there is a problem that the depth of the groove is deeper than the depth of the groove where the pits are not adjacent. For example, as shown in FIG. 1A, at a position A where the pit 1 and the groove 2 are adjacent to each other, the width of the groove 2 is larger than that of the portion B without the pit 1 and FIG. b), (c)
As is clear from FIG. This phenomenon is more likely to occur when the pits are longer. When a disc is created using a master disk that has this phenomenon, when the signal is reproduced, even if pits have the same size, if there is a pit in the adjacent land, the adjacent groove is deep, so the read signal is Is lower than the normal value.

[0004] To explain this further, FIG.
FIG. 2C shows the pit 1 and the groove 2 when the size of the groove 2 is affected by the adjacent pits (FIG. 7A) and when the size is not affected (FIG. 9C). ),
(D) shows a read signal when each is read. As shown in FIG. 2A, the pit 1b in which the pit 1 exists in the adjacent land portion is different from the pits 1a and 1c because the groove portion 2a adjacent to the pit 1b is deep due to the pit 1. FIG. 2 shows the read signal.
It becomes smaller as shown in FIG. As a result, the reproduced signal is degraded, and the jitter is degraded.

On the other hand, the portion adjacent to the pit is also shown in FIG.
When the groove shape is uniform as in (c), the size of the reproduced signal is the same if the pits have the same size. In this case, no deterioration in the jitter of the reproduced signal is observed. As a method for solving such a problem, there has been proposed a method in which a groove having pits and adjacent to the pits is formed in a narrower groove than a groove in a portion having no pits (JP-A-1-133234). . However, the method of changing the width of the groove in the above proposed method can be relatively easily formed in the case of a rectangular groove. In particular, in the case of forming a V-shaped groove used in the land recording method, the V-shaped groove is used. Is determined uniquely by the exposure optical system, the sensitivity of the photoresist film, and the developing conditions. Therefore, it is very difficult to change the groove width depending on whether or not the portion is adjacent to the pit.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disk in which grooves having a constant width and depth are formed irrespective of whether pits are adjacent to each other, and therefore the output of read signals by the pits is uniform. The present invention provides an optical disk master and a method of manufacturing the same.

[0007]

The inventor of the present invention has conducted intensive studies to improve the above-mentioned problems in the preparation of the master optical disc, and as a result, the phenomenon that the groove shape changes beside the pits is as follows.
This is caused by the overlap of the light exposing the pit and the light exposing the groove.For example, the light exposing the pit leaks to the position of the light exposing the groove. It has been found that this is due to the fact that the exposure power becomes larger than the exposure power (exposure light fogging). In order to minimize the leakage of pit exposure light, the photosensitive material used in the exposure process is exposed It was found that by using a dye mixed with a dye that easily absorbs, it is possible to absorb pit exposure light leakage light up to the position of the groove exposure light and eliminate fog of the exposure light. Was completed.

That is, according to the present invention, a photosensitive resin containing a dye that absorbs light having a wavelength used for pit exposure is coated on a substrate, and a laser beam corresponding to a pit signal and a laser beam for forming a groove are applied to the photosensitive resin. An optical disc master, which is irradiated and has a pattern formed in which groove expansion due to pit formation is suppressed, and

A photosensitive resin containing a dye that absorbs light having a wavelength used for pit exposure is applied onto a substrate, and the substrate is exposed to a laser beam corresponding to a pit signal and a laser beam for forming a groove. An object of the present invention is to provide a method of manufacturing a master disc, wherein a pattern is formed in which groove expansion accompanying pit formation is suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In manufacturing an optical disk master according to the present invention, first, a photosensitive resin is applied on a substrate. The material of the substrate is not particularly limited, but a glass plate is preferable from the viewpoint of surface smoothness and touch resistance.

In manufacturing an optical disc master, a new glass master 11 is first prepared as shown in FIG. 3 showing a flow chart of the manufacturing process and FIG. 4 showing a cross-sectional view of each stage until an optical disc master is obtained. The glass master disk 11 used in step S1 is collected (step S1), and is polished to a predetermined thickness and surface roughness (step S2, FIG. 4A). The polished glass master 11 is transferred to a cleaning step to remove dirt (step S3), and is subjected to, for example, a primer treatment.

Subsequently, the glass master 11 is supported on a rotary support, and a photoresist is applied by spin coating so as to have a uniform thickness (step S4). The photoresist is cured by a pre-bake process, and the photoresist layer 1 is cured.
2 (FIG. 4B). Next, in the laser cutting step, a portion of the photoresist layer 12 where pits and grooves are to be formed is selectively irradiated with laser light 13 (step S5, FIG. 4C). By this step, the photosensitive portion of the photoresist layer 12 is more easily dissolved in the alkaline developer than the non-photosensitive portion. By utilizing this, an alkaline developer is applied to the photoresist layer 12 and development is performed (step S6), so that the photoresist layer 20 at the portion irradiated with the laser beam 21 is selectively located at positions corresponding to the pits and grooves. (FIG. 4D).

Thereafter, a metal film 14 for imparting conductivity is formed on the photoresist layer 12 (step S7).
FIG. 4 (e). Here, examples of the metal constituting the metal film 14 include silver (Ag), nickel (Ni), and the like. Next, for example, a nickel (Ni) electroformed body 15 is formed on the metal film 14 by electroforming.
(F)). The nickel (Ni) electroformed body 15 is formed on the photoresist layer 12 and the glass substrate 1 together with the metal film 14.
The metal master (stamper) 16 as shown in FIG.

Subsequently, the back surface (inner surface) of the stamper 16
Is polished (step S9), and the inner and outer diameters of the stamper are processed in accordance with the molding die (step S10), and then inspected to obtain a finished stamper (step S11). A photosensitive resin is used as a photoresist and used as a photosensitive resin coating solution. The photosensitive resin coating solution generally comprises a photosensitive resin, a photosensitive agent, and a solvent, and in the present invention, a dye that absorbs light having a wavelength used for pit and groove exposure is added.

As the photosensitive resin, a resin which becomes soluble upon exposure to light is used, for example, phenol, cresol, ethylphenol, t-butylphenol, xylenol, naphthol, 1,4-dihydroxybenzene,
A so-called novolak resin obtained by condensation polymerization of a hydroxy aromatic compound such as 1,3-dihydroxybenzene with an aldehyde such as formaldehyde, acetaldehyde, benzaldehyde, and furfural, and polyhydroxystyrene and its derivatives are used. If necessary, an alkali-insoluble resin, for example, polymethyl methacrylate, styrene, or the like may be blended with the resin to make the whole alkali-soluble.

As the photosensitizer, diazonium salts, azide compounds and quinonediazide compounds are generally used. For example, quinonediazide-based photosensitizers include 1,2
-Benzoquinonediazide-4-sulfonic acid, 1,2-
Naphthoquinonediazide-5-sulfonic acid, quinonediazide-based photosensitizers of esters or amides such as 1,2-naphthoquinonediazide-4-sulfonic acid are preferable,
Specifically, polyhydroxyalkyl compounds such as glycerin and pentaerythritol and / or 1,2-benzoquinonediazide-4-polyhydroxyaromatic compounds such as bisphenol A, gallic acid ester, quercetin, morin, and polyhydroxybenzophenone Sulfonic acid, 1,2-naphthoquinonediazide-5-sulfonic acid ester or 1,2-naphthoquinonediazide-4-
Sulfonate is used, and more preferably,
2,3,4-trihydroxybenzophenone, 2,3
4,4'-tetrahydroxybenzophenone, 2,
2 ', 4,4'-tetrahydroxybenzophenone,
1,2,3,4,4'-pentahydroxybenzophenone, 2,3,3 ', 4,4', 5'-hexahydroxybenzophenone, polyhydroxybenzophenone 1, such as polycondensate of pyrogallol and acetone 2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-5-sulfonic acid ester, or 1,2-naphthoquinonediazide-4-sulfonic acid ester is used.

Usually, a photoresist coating composition uses one or more of the above components, and comprises ethyl cellosolve acetate,
It can be produced by mixing and dissolving in a solvent such as ethyl lactate. For example, in the case of the above-mentioned novolak resin and quinonediazide-based photosensitizer, the photosensitizer is usually used in an amount of 5 to 100% by weight, preferably about 10 to 80% by weight based on the resin. The amount of the solvent used is not particularly limited, but it is usually preferable to use the solvent such that the total amount of the resin and the photosensitive agent is in the concentration range of 3 to 50% by weight.

In the present invention, by using a photosensitive resin mixed with a dye that absorbs light having a wavelength used for pit exposure, light leaking from the pit exposure light reaches the position of light for exposing the groove. It is characterized by the fact that light is absorbed during the period until the light overlaps. The wavelength of the light used to form the pits is not particularly limited, but is generally 500 nm or less, preferably 460 to 300 nm. Therefore, a dye that absorbs light having a wavelength of 500 nm or less is used, and for example, an azo dye can be used.

The compounding amount of the dye may be an amount which can be absorbed before the leakage light from the pit exposure light reaches the position of the light for exposing the groove, and usually varies depending on the exposure power of the pit exposure light. obtain. If the amount of the dye is too small, the light leakage from the pit exposure light cannot be absorbed, and the overlapping of the light cannot be eliminated. Generally, it is 0.01 to 10% by weight, preferably 0.1 to 8% by weight, based on the total solid content.

[0020]

Example 1 (Preparation example of photoresist solution) 10 g of cresol-based novolak resin, 2,3,4,2 ', 4'-pentahydroxybenzophenone, pyrogallol-acetone polycondensate and 1,2-naphthoquinonediazide 3.0 g of photosensitizer synthesized from -5-sulfonic acid chloride and wavelength 4
0.3 g of an azo yellow dye absorbing 58 nm light was dissolved in 30 g of a mixed solvent of ethyl lactate and propylene glycol monomethyl acetate. This has a pore size of 0.2μ
The solution was filtered through a membrane filter of m to prepare a photoresist solution, which was used as a resist A.

A photoresist B prepared in exactly the same manner except that no yellow dye was added was used as a resist B. (Manufacture of Optical Disk) The above-mentioned photoresist solution was applied on a glass substrate, prebaked, and then exposed. In the exposure, a track pitch between grooves was set to 1.1 μm, and pits were exposed at the center between the grooves. The length of the exposed pit was about 4 μm, and the exposure power of the pit was about twice the exposure power of the groove.

The effect of the dye on the groove shape was confirmed by observing the developed glass after exposure using an AFM.
The evaluation was made based on the difference between the groove depth next to the pits of the same groove and the groove depth where no pits exist. Table 1 shows the results of the groove depth. In the resist B, the difference between the groove depth between the side of the pit and the area without the pit is 20.9 n.
m is 1.6 nm in the resist A, and the effect of the dye-containing resist is seen.

[0023]

[Table 1]

Although the experiment was conducted with a specific pattern this time, the present invention is not limited to this content, and is applicable to all optical disk masters made using a photosensitive material.

[0025]

According to the present invention, the photosensitive resin photoresist used in the exposure step of preparing an optical disk master is mixed with a dye which easily absorbs the exposure light, so that the leakage light from the pit exposure light can be reduced as much as possible by the groove exposure light. By absorbing the light until it reaches the position and eliminating the overlap of light, the shape of the groove can be made uniform. When a disc is created using the master thus created, a reproduced signal with less jitter can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an enlargement of a groove by a pit (a).
Is a plan view, (b) and (c) are bb sectional views, respectively, c
-C sectional drawing.

FIG. 2 is a diagram showing the influence of pits and grooves,
(A) is a plan view when affected by pit exposure,
(B) is a diagram showing the read signal, (c) is a plan view in the case where it is not affected, and (d) is a read signal diagram.

FIG. 3 is a flowchart showing steps of a master optical disc.

FIG. 4 is a sectional view of an optical disc master in each step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Photosensitive resin (photoresist) 13 Laser beam 14 Metal film 15 Electroformed body 16 Stamper

Claims (4)

[Claims] A photosensitive resin containing a dye that absorbs light having a wavelength used for pit exposure is applied on a substrate, and a laser beam corresponding to a pit signal and a laser beam for forming a groove are applied to the photosensitive resin. An optical disc master on which a pattern is formed that suppresses the expansion of the groove accompanying the formation. 2. The method according to claim 1, wherein the dye contained in the photosensitive resin is 460 to 460.
2. A dye which absorbs a wavelength in the range of 300 nm.
The original optical disc described. 3. A substrate is coated with a photosensitive resin containing a dye that absorbs light having a wavelength used for pit exposure, and is irradiated with a laser beam corresponding to a pit signal and a laser beam for forming a groove. And forming a pattern in which groove expansion accompanying pit formation is suppressed. 4. The method according to claim 1, wherein the dye contained in the photosensitive resin is 460 to 460.
4. A dye absorbing a wavelength in the range of 300 nm.
The method for manufacturing the optical disc master described in the above.