JP2001250280A - Recording medium, method for producing recording medium, method for producing master for producing recording medium, apparatus for producing recording medium, and apparatus for producing original for recording medium - Google Patents

Abstract

(57) [Problem] To provide a high-density recording medium having a multi-value recording mark having a width smaller than a spot diameter of a reproduction laser beam. SOLUTION: The present invention uses a heat-sensitive material layer 12 as a recording medium in which a recording pattern having a narrower width than an optical spot having a wavelength used for reproduction and having multi-value recording marks of two or more types is formed. A laser beam is applied to the heat-sensitive material layer of the lever.
Irradiation with two or more levels of intensity or two or more discontinuous irradiations modulated to a frequency higher than the frequency of the recording pattern, forming a deteriorated portion of the pattern corresponding to the recording pattern, and developing it A target recording pattern or a pattern for obtaining the recording pattern is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a read-only recording mark by optical reproduction, a so-called ROM (Read Only Memory).
The present invention relates to a recording medium having a mold recording mark, a method of manufacturing a recording medium, a method of manufacturing a master for manufacturing a recording medium, an apparatus for manufacturing a recording medium, and an apparatus for manufacturing a master for manufacturing a recording medium. The master used in the present invention is a stamper for forming a recording medium having recording marks by, for example, injection molding or a 2P method (Photopolymerization method). The term refers to a so-called mother master for copying and copying a plurality of masters.

[0002]

2. Description of the Related Art In order to increase the density of data recorded on an optical disk, the wavelength of a reproduction laser beam must be reduced and the optical lens system must have a higher N.D. A. (High numerical aperture) has been achieved to achieve higher density. However, in recent years, the demand for higher density has been increasing, and there is no end. Due to the demand for higher density, realization of an optical disk having multi-level, that is, multi-valued data is desired. For optical discs that record this multi-level data,
There has been reported an application example in which the width of a recording mark is multi-gradation for a phase change optical disk. However, a recording medium based on multi-level recording, that is, multi-level recording with respect to a so-called ROM (Read Only Memory) disk dedicated to reproduction has not been realized.

At present, in the process of manufacturing a recording medium, for example, in the process of manufacturing a master, a photosensitive material layer 102 is usually formed on a substrate 101, for example, a glass substrate, which constitutes the master, as schematically shown in FIG. The photosensitive material layer 102 is formed by spin coating, and a laser beam 103
Is condensed by a condenser lens 104 and irradiated according to, for example, data to be recorded.
02 by developing, for example, a region that has been photosensitive-reacted by, for example, laser beam irradiation is removed to remove the photosensitive material layer 102.
Then, etching is performed on the substrate 101 using the photosensitive material layer as a mask to form a fine uneven pattern corresponding to recording data, that is, a recording mark.

As shown in an example of a γ (gamma) curve in FIG. 11, a photosensitive material has such a characteristic that a photosensitive reaction occurs rapidly, that is, almost stepwise at an exposure amount exceeding a certain exposure amount. As compared with the case where this photosensitive material is exposed by a laser beam having a laser beam power distribution shown by a curve 201 in FIG. 12A, the laser shown by a curve 202 in FIG. When exposing with a laser beam having a light power distribution,
Substantially photosensitive reaction area 20 in photosensitive material layer 102
2a expands to a certain extent as compared with the photosensitive reaction area 201a in the case of the laser light power distribution of the curve 201, but this expansion does not expand according to the exposure power.

Therefore, in the above-described manufacturing process of a master for manufacturing a recording medium, the laser beam is scanned on the photosensitive material layer 102 by, for example, the above-mentioned rotation of the substrate 101, for example, in a spiral manner, for example, as shown in FIG. In the case of performing exposure using the light emission pattern shown by the curve 203, FIG.
3B, the photosensitive material layer 102 on the substrate 101
An exposed portion 102A corresponding to the laser beam irradiation pattern is formed on the substrate 101. The exposed portion is removed by, for example, development, and the photosensitive material layer 102 is used as an etching mask for the substrate 101.
The fine irregularities formed by etching with respect to FIG.
For example, as shown in a plan view of the concave portion 103 as a recording mark, the pattern is formed as a pattern having a stable width.

However, in this case, the fine concavo-convex pattern formed by pattern exposure of the photosensitive material layer is almost determined by the spot diameter of the laser beam used for the exposure, and the fine concavo-convex pattern exceeding the optical limit is formed. And it is difficult to form a plurality of patterns having different widths.

On the other hand, the spot diameter of the reproduction light is usually selected to be about twice the width of the recording mark so as to reliably read the recording mark. In other words, it is desirable that the recording mark formed on the recording medium be formed to be 以下 or less of the minimum spot diameter that can be formed as reproduction light. However, in the above-described method, the mark width cannot be reduced to a small width exceeding the optical limit, so that the recording mark width cannot be reduced to half or less of the spot of the reproduction laser beam.

Therefore, as a method of forming the multi-value recording for reproduction only, a method of dividing one mark into a plurality of times by using a high-resolution apparatus such as an electron beam lithography apparatus can be considered. However, according to this method, there is a problem that the device is complicated and large, such as necessity of working in a high vacuum, expensive, and maintenance is troublesome.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a high-density recording medium having a multivalued recording mark having a width smaller than the spot diameter of a reproduction laser beam, a method of manufacturing the recording medium,
Method for manufacturing master for recording medium production, apparatus for producing recording medium,
And an apparatus for producing a master for recording medium production.

[0010]

A recording medium according to the present invention has a width smaller than an optical spot having a wavelength used for reproduction, and
In addition, the recording medium is a recording medium on which a recording pattern having read-only multi-value recording marks of two or more types is formed.

Further, the method for manufacturing a recording medium according to the present invention has a width smaller than an optical spot having a wavelength used for reproduction.
And a method for manufacturing a recording medium on which a recording pattern having a multi-valued recording mark dedicated to reproduction of two or more types is formed, and a step of forming a heat-sensitive material layer on a substrate constituting the recording medium; The heat-sensitive material layer is irradiated with a laser beam with two or more levels of intensity or two or more types of discontinuous irradiation modulated at a frequency higher than the period of the recording pattern, thereby altering the pattern corresponding to the recording pattern. Forming a portion and developing the heat-sensitive material layer to pattern the heat-sensitive material layer.

Further, in the method of manufacturing a master for manufacturing a recording medium according to the present invention, a recording pattern having a read-only multivalued recording mark having a width narrower than an optical spot having a wavelength used for reproduction and having two or more widths is provided. A method for producing a master for manufacturing a recording medium to be formed, comprising: a step of forming a heat-sensitive material layer on a substrate constituting the master for a recording medium; A step of irradiating with two or more levels of intensity or two or more discontinuous irradiations to form a deteriorated portion of a pattern corresponding to a recording pattern, and developing the heat-sensitive material layer. Patterning the heat-sensitive material layer.

Further, the apparatus for manufacturing a recording medium according to the present invention has a width smaller than an optical spot having a wavelength used for reproduction.
An apparatus for manufacturing a recording medium on which a recording pattern having a read-only multi-valued recording mark having two or more types of widths is formed, wherein the recording medium has a heat-sensitive material layer formed on at least one main surface. A holding unit for holding the substrate, a laser light source unit, and a laser light modulating unit, wherein the laser light from the laser light source is formed by a recording data signal for forming the recording pattern by the modulating unit, and a period of the recording pattern. Is also modulated by a high-frequency signal to form a deteriorated portion of a pattern corresponding to the recording pattern in the heat-sensitive material layer.

Further, according to the apparatus for manufacturing a master for manufacturing a recording medium of the present invention, a recording pattern having a reproduction-only multivalued recording mark having a width narrower than an optical spot having a wavelength used for reproduction and having two or more widths is provided. An apparatus for manufacturing a master for manufacturing a recording medium to be formed, comprising: holding means for holding a substrate constituting a recording medium having a heat-sensitive material layer formed on at least one main surface thereof; a laser light source unit; Modulation means, and modulates a laser beam from a laser light source with a recording data signal for forming a recording pattern by the modulation means, and a signal having a frequency higher than the period of the recording pattern, to the heat-sensitive material layer, It is configured to form a deteriorated portion of a corresponding pattern.

As described above, the recording medium according to the present invention has a configuration in which the width of the recording mark is changed, and this configuration enables multi-value recording.

In the method for manufacturing a recording medium and the method for manufacturing a master for manufacturing the medium according to the present invention, a heat-sensitive material layer is used, a deteriorated portion is formed by irradiating a laser beam, and the deteriorated portion is developed. A recording pattern or a pattern for forming a recording pattern is formed, and the laser light to be irradiated at this time is at least two levels of intensity or two levels modulated at a frequency higher than the period of the recording pattern. Because of the discontinuous irradiation described above, recording marks of different widths, that is, two or more values, can be formed, and by high-frequency modulation, the recording marks can be formed with a desired width regardless of the length of the pattern such as the recording mark length. Can be done.

Further, in the method of manufacturing a recording medium and the method of manufacturing a master for manufacturing a recording medium according to the present invention, a heat-sensitive material layer is used to form a deteriorated portion by laser light irradiation. Since the formation is performed by forming a temperature rising portion by light irradiation, the width of the temperature rising region that rises to the temperature required for forming the altered portion can be made smaller than the laser beam spot size, so A smaller recording mark or a pattern corresponding to the recording mark can be formed as compared with the case where the material layer is used.

Further, the apparatus for manufacturing a recording medium and the apparatus for manufacturing a master for manufacturing a recording medium according to the present invention can have a simple configuration, and can be made compact and easy to handle.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A recording medium, a method for manufacturing a recording medium, a method for manufacturing a master for manufacturing a recording medium, an apparatus for manufacturing a recording medium, and an apparatus for manufacturing a master for manufacturing a recording medium according to the present invention include:
For example, in an optical pickup that performs optical reproduction on a recording medium, the distance between the recording medium and the optical lens is set to 200 nm.
The so-called near-field configuration described below and the high N.O. A. When a (high numerical aperture), blue-violet laser beam having a short wavelength is used, that is, it can be applied to a recording medium in which a spot of a reproduction laser beam is minute.

The recording medium according to the present invention is a recording medium on which a read-only recording pattern having at least a recording mark is formed. For example, as shown in FIG. 1, as described later, it is narrower than an optical spot having a wavelength used for reproduction. As shown in FIG. 1, multi-value recording using two or more types of recording marks, for example, as shown in FIG. 1, three types of widths W ₁ and W ₂ are shown. , for example concave or convex portions having a W _3, that is, the recording mark ₁ 1 by fine irregularities, 1 _2, 1 ₃ by, for example, "0",
It has a configuration in which a recording pattern in which four-level recording of “1”, “2”, and “3” is performed is formed.

In the method of manufacturing a recording medium according to the present invention, first, a transparent resin substrate constituting the recording medium or a substrate having a silicon oxide (SiO ₂ ) layer formed on, for example, a glass substrate (hereinafter referred to as SiO ₂ substrate) ) Is prepared, and a heat-sensitive material layer is formed thereon. A laser beam is applied to this heat-sensitive material layer to obtain the desired multi-valued recording mark 1.
Pattern corresponding to the pattern of fine irregularities including (1 _1, 1 _2, 1 _3), that is, for example recording mark 1 of Fig. 1 and,
For example, irradiation is performed with a pattern corresponding to an array pattern including grooves or the like, and a deteriorated portion is formed on the heat-sensitive material layer by a temperature rise in a laser beam irradiation portion.

Now, assuming that the power distribution in the spot of the irradiation laser beam has, for example, a curve 3L in FIG. 2A and is a substantial laser spot SP _L in the heat-sensitive material layer, the temperature at which a deteriorated portion in the heat-sensitive material layer is generated width W _L of the rising area 4L is a laser spot SP _L than the narrow area. That is, this altered portion can be made smaller than the laser spot. Further, by selecting the laser power, the temperature rise region 4L, that is, the width W of the deteriorated portion is determined.
_L can be chosen smaller or larger. Then, the power distribution of the laser beam, for example, as shown by curve 3H in Figure 2B, if it is larger than the power of the curve 3L in Figure 2A, the temperature rise area 4H substantially laser spot in the heat-sensitive material layer by SP _H width W _H of the becomes larger than the width W _L of the temperature rise area 4L in Figure 2A.

In other words, by selecting the level of the laser intensity, it is possible to change the width of the temperature rising region, that is, the width of the deteriorated portion in the heat-sensitive material layer. An altered portion for forming a multi-level recording mark is formed by selecting the intensity level of the laser beam.

Incidentally, as shown in FIGS. 2A and 2B, the temperature rising regions 4L and 4H have a wider shape behind the spots SP _L and SP _{H in} the spot moving direction, because the rear side is larger than the front side. However, since the spot irradiation time is long, the temperature rise area is widened.

Now, for example, as shown in FIG. 3A, a case will be described in which data patterns of four levels of levels 0 to 3 are recorded. In this case, as shown in FIG. 3B,
Is intended to record the recording mark 1 ₁ to 1 ₃ having three widths W ₁ to _W-3, the respective marks are uniform width by each predetermined width W ₁ to _W-3 over the possible overall length, respectively It is desirable that

However, in this case, simply
When a laser beam is scanned over the heat-sensitive material layer with a laser irradiation intensity pattern corresponding to the data patterns of levels 0 to 3, an altered pattern having a width corresponding to the level is formed,
For example, the pattern of the recording mark formed by removing the deteriorated portion is not uniform over the entire length and becomes wider at the rear end side as shown in FIG. .

On the other hand, in the present invention, for example, in the recording of the data pattern shown in FIG. 3A, for levels 1 to 3 other than the 0 level, the laser irradiation pattern is changed as shown in FIG. 4A or 4B. The modulation is performed with a period of the recording pattern, that is, a constant high-frequency signal of a frequency higher than the period of the data pattern, for example, several hundred MHz. That is, each mark pattern ₁ 1 to 1 ₃
4A, for example, as shown in FIG. 4A, power modulation of a laser beam having a power of level 0 (off level) and power of levels 1 to 3 or as shown in FIG. Laser irradiation to the heat-sensitive material layer is performed by repeating power modulation of laser light with a power between a predetermined level and a predetermined level lower than these levels.

Thereafter, when the heat-sensitive material layer is developed to remove, for example, the deteriorated portion, as shown in FIG. 4C, each of the marks 11 ₁ to 11 is formed as a pattern of the heat-sensitive material layer.
In 1 _3, each of which can form a pattern of uniform width due to the respective widths W ₁ to _W-3 over its entire length. This is because laser irradiation by high-frequency modulation is performed intermittently or by repeating strong and weak, so that laser irradiation of each data when performing continuous laser irradiation on each data without such high-frequency modulation is performed. This is because a remarkable temperature rise on the rear end side of the pattern can be avoided.

In this manner, by patterning the heat-sensitive material layer, a recording pattern having a multi-valued recording mark due to fine irregularities on the heat-sensitive material layer can be formed. However, in this case, since the depth (difference in height) of the fine unevenness is restricted by the thickness of the heat-sensitive material layer, the substrate surface is subjected to an anisotropic process using the heat-sensitive material layer as an etching mask. R by reactive etching
Etching to a required depth by IE (Reactive Ion Etching) can form fine unevenness having a required depth.

The method of manufacturing a master for manufacturing a recording medium according to the present invention uses, for example, the multivalued recording mark 1 (1) shown in FIG.
_1, 1 _2, 1 recording medium having a recording pattern 2 with _3), such as injection molding, to produce a master disk for obtaining the 2P method or the like.

In the method of manufacturing the master, a substrate constituting the master is prepared, and a heat-sensitive material layer is formed thereon. Then, in the heat-sensitive material layer, a laser beam is applied to form a deteriorated portion having a pattern corresponding to a target pattern of fine irregularities, that is, a pattern corresponding to, for example, the recording mark pattern of FIG.

Also in this case, irradiation with modulated laser light is performed in the same manner as described with reference to FIG.
Thereafter, the heat-sensitive material layer is developed to remove, for example, the deteriorated portion, and the heat-sensitive material layer is patterned.

In this manner, the patterning of the heat-sensitive material layer corresponds to a recording pattern finally formed and having a multi-value recording mark due to the difference in width.
Since the fine irregularities are formed by the heat-sensitive material layer, this state can be used as a master for a recording medium having the fine irregularities. In this case, the depth of the fine irregularities (difference in height)
Is limited by the thickness of the heat-sensitive material layer, and the substrate surface is subjected to, for example, RIE by anisotropic etching using the heat-sensitive material layer as an etching mask.
By etching to a required depth, fine irregularities having a required depth can be formed to manufacture a master.
As described above, these masters refer to a stamper, a so-called master for duplicating and forming this stamper, a so-called mother master for duplicating and forming this master, and the like.

In the method of manufacturing a master according to the present invention, similarly to the above-described method of manufacturing a recording medium, a heat-sensitive material layer is used, and a deteriorated portion is formed by irradiating the layer with a laser beam. It is possible to form a fine concavo-convex pattern having a width smaller than a spot and a required width, and having a uniform width over substantially the entire length of each mark.

The method for manufacturing a recording medium according to the present invention described above,
In addition, the heat-sensitive material layer used in the method of manufacturing a master for manufacturing a recording medium may have a laminated structure of at least two or more layers made of mutually different constituent materials, that is, at least the first and second material layers. Then, the temperature rise due to the above-described laser beam irradiation causes mutual diffusion or dissolution between these constituent material layers, thereby forming a deteriorated portion due to mixing or reaction of these two or more materials.
The constituent material of the heat-sensitive material layer is preferably an inorganic material.

The specific structure of the heat-sensitive material layer is, for example, a laminated structure of an Al layer and a Cu layer, a laminated structure of an Al layer and a Ge layer,
It is not limited to a laminated structure of a Si layer and an Al layer, a laminated structure of a Ge layer and an Au layer, and these two-layer structures.
It can have a laminated structure of three or more layers. Further, it is also possible to form a heat-sensitive material layer having a one-layer film structure of a metal such as Ti, Ta or the like, which causes a thermal oxidation phenomenon, and to change the quality by reacting oxygen in the air by irradiation with a laser beam. .

The laser beam irradiated to the heat-sensitive material layer is a semiconductor laser, particularly a blue-violet laser beam having a short wavelength (for example, a wavelength of 410 nm).
It is preferable to use laser light of, for example, a GaN-based laser (nm to 390 nm). With such a short-wavelength laser, the spot diameter of the laser beam is reduced.

The development process for patterning the heat-sensitive material layer is performed, for example, with an aqueous solution of 1 to 3% of tetramethylammonium hydroxide.

Next, an embodiment of the method for manufacturing a recording medium according to the present invention will be described with reference to FIGS. 5 and 6 (FIGS. 1 and 2). The method of manufacturing the master is not limited to this example.

As shown in FIG. 5A, for example, a disk-shaped substrate 11 having an SiO ₂ layer (not shown) formed on a constituent substrate of a recording medium, for example, a glass substrate, is prepared.
_A heat-sensitive material layer 12 is formed on _two surfaces. The heat-sensitive material layer 12 has a film configuration in which the property is changed, that is, the property is changed by a rise in the temperature of the laser beam. In this example, the thermosensitive material layer 12 comprises first and second material layers 12a and 12b.
This is a case in which the configuration has a laminated structure of. These first and second material layers 12a and 12b have a material configuration in which a deteriorated portion is formed by alloying by mutual diffusion or melting due to a temperature rise by laser light irradiation. At the same time, for the altered portion, a material is selected that causes a difference in the dissolution rate between the unaltered portion and the unaltered portion with respect to a developing solution (dissolving solution) used in a later-described developing process. . The combination of the constituent material layers of the first and second material layers 12a and 12b is Al
And Cu, Al and Ge, and the like.

As shown in FIG. 5B, a laser beam 13 is applied to the heat-sensitive material layer 12 by, for example, rotating the substrate 11.
The movement of the laser spot in the radial direction of the substrate 11 causes the laser spot on the heat-sensitive material layer 12 to move in a circular or spiral shape in a relatively predetermined direction, for example, on the disk-shaped substrate 11 as shown by an arrow in FIG. Move along the shape.

Along with this relative movement, for example, the heat-sensitive material layer 12 is irradiated by laser light irradiation at three or more levels by high-frequency modulation described with reference to FIG. 4A or 4B.
In addition, forming a heating section of a required pattern of two or more widths,
In this heating section, the first and second heat-sensitive material layers 12
The material layers 12a and 12b are alloyed with each other, for example, to form two or more kinds of intended altered portions 12s having required widths. In this way, as shown in FIG. 6A, the heat-sensitive material layer 12 is formed with a deteriorated portion 12s by, for example, alloying and a non-transformed portion 12n in which the other portions are not alloyed.

Thereafter, the heat-sensitive material layer 12 is subjected to a developing treatment, and as shown in FIG.
s is removed, that is, selective etching is performed. This developer,
That is, as the etching solution for the altered part, for example, 1 to 3
% Of a tetramethylammonium hydroxide aqueous solution, and immersed in the aqueous solution, the altered portion 12 alloyed can be selectively etched away, and the heat-sensitive material layer 12 can be patterned.

A target recording medium having a pattern formed by the heat-sensitive material layer 12 as a recording pattern, that is, a read-only multivalued recording mark having a width narrower than at least an optical spot having a wavelength used for reproduction and having two or more widths. A recording pattern 2 having the following pattern is formed, and for example, an optical disk can be used. In this example, as shown in FIG. 6C, the heat-sensitive material layer 12 having the fine pattern is used as an etching mask, and SiO
_{The two} layers are etched to form fine irregularities 15. In this etching, fine irregularities 15 having a highly irregular cross section can be formed by RIE (reactive ion etching) using anisotropic etching.

The height difference (depth) of the fine irregularities 15 can be freely selected, for example, by selecting the SiO ₂ layer as the surface layer of the substrate. In some cases, for example, Si
By using the underlying substrate below the O ₂ surface layer as an etching stopper, the depth of the fine irregularities 15 can be defined by the thickness of the SiO ₂ surface layer.

Thereafter, the heat-sensitive material layer 12 is sequentially immersed in each solution of the second and second material layers 12b and 12a to remove them. Thus, FIG.
As shown in FIG. 1, fine irregularities 15 are formed on the surface of the substrate 11. Thereafter, the heat-sensitive material layer 12 is dissolved and removed, and the fine irregularities 15 are formed on the substrate 11 on which the recording pattern 2 is formed.
Although not shown, for example, a reflective film, a protective film, and the like are provided as necessary, and the target recording medium 16, that is, at least a width smaller than an optical spot having a wavelength used for reproduction,
In addition, a recording pattern 2 having two or more types of read-only multi-valued recording marks having a width of two or more is formed, and for example, an optical disk can be obtained.

As in the above-described method, in the case of using a tetramethylammonium hydroxide aqueous solution in the development process after the laser beam irradiation of the heat-sensitive material layer 12, that is, in the selective etching, a conventional ordinary photosensitive material layer is used. In the method, since the work is the same as the work used in the master production method using the novolak resin as the photosensitive material layer, the apparatus and process used in the conventional process can be used as it is. Has advantages.

In the above-described example, the altered portion 12s caused by the irradiation of the laser beam as the heat-sensitive material layer 12 is removed by the development process, that is, the selective etching.
A method of removing the non-altered portion 12n can also be used. In this case, the heat-sensitive material layer 12 is made of, for example, a combination of Ge and Al, a combination of Si and Al, a combination of Ge and Au, and the first and second non-altered portions.
Removal of the material of the above, a mixture of phosphoric acid, water, glycerin,
It can be removed by using a mixture of a tartaric acid solvent and hydroperoxide.

The formation of the altered part of the heat-sensitive material layer 12 is as follows.
It is possible to use a phase change, a thermal oxidation phenomenon, and the like, and is not limited to a multilayer structure. For example, a single layer structure of a metal capable of forming the altered portion 12s by the thermal oxidation phenomenon, for example, titanium, tantalum, or the like, is used. The laser beam irradiation reacts with oxygen in the air to change the quality.

As described above, in the method of the present invention,
Since the multi-layer or single-layer heat-sensitive material layer can be composed of an inorganic material, these multi-layer or single-layer heat-sensitive material layers can be formed by a sputtering method, a vacuum evaporation method, or the like. As compared with a film forming method using a spin coating method in the case of using a photosensitive material layer, a thin film thickness can be uniformly formed in each part. Therefore, it is possible to reliably form a recording pattern based on fine irregularities having at least recording marks.

Further, as described above, the substrate 11 is etched by, for example, RIE using the patterned heat-sensitive material layer 12 as a mask to form the fine irregularities 15.
By doing so, it is possible to avoid the inconvenience that depends on the depth and shape of the fine unevenness due to the thickness and cross-sectional shape of the heat-sensitive material layer 12 as in the case where the fine unevenness is formed by the heat-sensitive material layer 12 itself.

Next, an embodiment of a method for manufacturing a master according to the present invention will be described. The method for manufacturing the master can employ the same method as described with reference to FIGS. 5 and 6. In the production of the master, the substrate 11 is constituted by the substrates constituting the master. However, even in this case, for example, the above-described SiO ₂ substrate can be used.

The master 26 shown in FIG. 6D thus manufactured can be used as a stamper, the master 26 can be used as a master for inverting and duplicating the stamper, and furthermore, the master 26 can be used as a master. May be used as a mother master that reverses and duplicates the master.

Then, by using the stamper thus obtained, a recording medium substrate having fine irregularities in a recording pattern having multivalued recording marks having different target widths is formed by injection molding, 2P method or the like. A reflective film and a protective film are formed as necessary, for example, in the same manner as in the production of the recording medium described above, and a target optical disk, magneto-optical disk, etc. can be obtained.

As shown in FIG. 7, a recording medium manufacturing apparatus according to the present invention, as shown in FIG. 7, schematically shows a recording medium on which a heat-sensitive material layer (not shown) is formed. Holding means 41 for holding the substrate 11 in a shape, a laser light source part 42, and the laser light 13 from the laser light source part 42, which is modulated in accordance with a fine uneven pattern,
A modulating means for modulating at a frequency higher than the period of the pattern of the fine irregularities, an optical system 45 having a condenser lens system 44 for condensing the laser light on the heat-sensitive material layer, and irradiation of the heat-sensitive material layer with the laser light And a moving means for moving the position.

The laser light source section 42 can be configured not to use a semiconductor laser, for example, but to provide a laser such as an Ar gas laser and a wavelength converter, for example, and to take out as a short wavelength laser. In this case, as shown in FIG. 7, the low-speed modulator 46 and the high-speed modulator 47
The laser light 13 emitted from the laser light source unit 42 is provided in the optical path of the laser light 13 toward the substrate 11 by the optical system 45. The low-speed modulator 46 modulates the laser light 13 with the recording data signal described with reference to FIG.
Reference numeral 7 modulates the laser light by the high-frequency signal described with reference to FIG.

As the low-speed modulator 46, various well-known modulators, for example, modulators utilizing various effects such as an electro-optic (EO) effect, an acousto-optic (AO) effect, and the like can be used. Further, the high-speed modulator 47 is, for example, K. Osato,
K.Yamamoto, I.Ichimura, F.Maeda, Y.Kasami, M.Yamada, Pr
oceedings of Optical Data Storage'98, Aspen, Colorad
o, 80-86, “A rewritable optical disk system with o
ver 10GB of capasity ”.

As described above, the laser light 13 extracted from the laser light source section 42 is supplied to the high-speed modulator 47 and the low-speed modulator 4.
The substrate 1 is modulated by an optical system 45 having a mirror 48 and a condenser lens system 44, for example.
The upper heat-sensitive material layer 1 is focused and irradiated. At this time, as the moving means, for example, the holding means 41 of the substrate 11 is rotated so that the laser beam 13 for the heat-sensitive material layer relatively moves on the substrate 11 so as to scan, while the optical system Is moved in the radial direction of the substrate 11,
The laser beam 13 is concentrically scanned on the heat-sensitive material layer on the substrate 11 in each circle or in a spiral shape.
By the modulation of the laser light described above, a deteriorated portion having a predetermined pattern is formed.

In the example shown in FIG. 8, the laser light source section 42 is constituted by a semiconductor laser. In FIG. 8, portions corresponding to those in FIG. Although the overlapping description is omitted here, as the modulating means 43 in this case, the injection current to the semiconductor laser is
It is modulated by the above-mentioned recording data signal and high-frequency signal.

After irradiating the heat-sensitive material layer with the laser beam by the above-described apparatus of the present invention, the heat-sensitive material layer is developed and etched according to the above-described method of the present invention to have the desired fine irregularities. Obtain a recording medium.

Further, the apparatus for manufacturing a master for producing a recording medium according to the present invention can have the same structure as that shown in FIGS. 7 and 8. 11 means.

According to the apparatus for manufacturing a recording medium and the apparatus for manufacturing a master for manufacturing a recording medium according to the present invention, a simple configuration can be achieved, so that the apparatus can be made compact and inexpensive.

In particular, in the case of the configuration shown in FIG. 8, the use of a semiconductor laser makes it possible to make the device smaller and simpler, and at the same time to reduce the cost, and also to greatly reduce the maintenance work. .

Also in this case, as a semiconductor laser,
The use of a short-wavelength blue-violet laser such as a GaN-based laser can form smaller fine irregularities and achieve higher density.

In the above-described examples of the method for manufacturing a recording medium, the method for manufacturing a master for manufacturing a recording medium, the apparatus for manufacturing a recording medium, and the apparatus for manufacturing a master for manufacturing a recording medium, a laser for forming a recording mark of each width is used. This is a case where the light is emitted by selecting the intensity level of the irradiation laser described with reference to FIG. 4A or B, but the recording marks 11 ₁ to ₁ of the respective widths W _{1 to} W _{3 in} FIG.
₃ is the width W of each recording mark as shown in FIG. 9A.
Depending on the ₁ to _W-3, it may be a laser irradiation pattern in close spacing of the laser pulse as it increases its width. In this case, as the pulse becomes denser, the temperature rise temperature in the heat-sensitive material layer can be increased, so that the width of the temperature rise region similar to that described with reference to FIG. 2 can be increased. By the same effect, recording marks having different widths can be finally formed.

Further, the present invention is not limited to a disk-shaped disk, but can be applied to a case where a recording medium having another shape, for example, a card shape is obtained. In the recording pattern according to the present invention, a groove or the like can be formed simultaneously with the multi-value recording mark. Further, the recording medium according to the present invention, together with the formation of a read-only recording pattern, for example, an area that enables recording and reproduction, a magnetic recording layer,
Various recording layers such as a magneto-optical recording layer may be formed.

[0067]

According to the recording medium of the present invention, multi-value recording is performed by changing the width of a recording mark. Therefore, according to this configuration, this recording medium can be easily manufactured.

In the method for producing a recording medium or a method for producing a master for producing a recording medium according to the present invention, a heat-sensitive material layer is used instead of a conventional photosensitive material.
This is irradiated with a laser beam to form a thermally altered portion, and the altered or unaltered portion is removed by development to form a pattern. The deteriorated portion is formed in the heating region, and based on this, it can be formed as a fine pattern smaller than the optical limit of the laser beam spot. Therefore, a high-density, high-resolution recording medium can be configured.

As described above, the recording medium of the present invention employs a mode in which the multi-value recording is recorded as a change in the width of the recording mark, whereby the above-described method for producing a recording medium or a master for producing a recording medium is performed. In the manufacturing method of
By selecting the intensity of the laser beam irradiation or the discontinuous interval of the discontinuous irradiation on the heat-sensitive material layer, it is easy to form the deteriorated portion in the heat-sensitive material layer having different widths,
It is possible to easily and reliably form a multi-valued recording mark dedicated to reproduction.

In the method of the present invention, the laser irradiation on the heat-sensitive material layer is simultaneously modulated with the recording data signal, and simultaneously with the high-frequency signal having a higher frequency, whereby the recording mark of each width can be substantially changed. The desired required width can be obtained over the entire length. Therefore, it is possible to form a recording medium that can effectively avoid generation of noise and generation of error in reproduction.

Further, according to the apparatus for producing a recording medium and a master for producing a medium according to the present invention, there is no need to provide a high vacuum chamber or the like, so that the apparatus is simple, compact, inexpensive, and easy to maintain. Can be configured.

[Brief description of the drawings]

FIG. 1 is a plan view of an example of a recording pattern having a recording mark of a recording medium according to the present invention.

FIGS. 2A and 2B are diagrams showing a relationship between a power distribution of a laser beam used in the method of the present invention and a temperature rising region.

3A and 3B are explanatory diagrams of a method of manufacturing a recording medium and a method of manufacturing a master for manufacturing a recording medium according to the present invention, wherein A is a data pattern diagram, B is a target recording mark pattern diagram, C is a laser beam irradiation pattern, and D FIG. 4 is a diagram of a recording mark pattern or a pattern of a deteriorated portion of a heat-sensitive material layer.

4A and 4B are explanatory diagrams of a modulation method as an example of a method of manufacturing a recording medium and a method of manufacturing a master for manufacturing a recording medium according to the present invention, wherein A and B are laser irradiation pattern diagrams, and C is a recording mark pattern or a heat-sensitive material layer. FIG. 5 is a pattern diagram of a deteriorated portion.

FIGS. 5A and 5B are process diagrams (part 1) of each example of a method for manufacturing a recording medium and a method for manufacturing a master for manufacturing a recording medium according to the present invention.

FIGS. 6A to 6D are process diagrams (part 2) of each example of the method for manufacturing a recording medium and the method for manufacturing a master for manufacturing a recording medium according to the present invention.

FIG. 7 is a configuration diagram of an example of an apparatus for manufacturing a recording medium and an apparatus for manufacturing a master for manufacturing a recording medium according to the present invention.

FIG. 8 is a configuration diagram of another example of the apparatus for manufacturing a recording medium and the apparatus for manufacturing a master for manufacturing a recording medium according to the present invention.

FIG. 9 is an explanatory view of a modulation method of another example of a method of manufacturing a recording medium and a method of manufacturing a master for manufacturing a recording medium according to the present invention, wherein A is a laser irradiation pattern diagram, and B is a recording mark pattern or a heat-sensitive material layer. FIG. 5 is a pattern diagram of a deteriorated portion.

FIG. 10 is a schematic cross-sectional view for explaining a method for manufacturing, for example, a master using a conventional photosensitive material.

FIG. 11 is a γ (gamma) curve diagram of a photosensitive material.

FIGS. 12A and 12B are views for explaining a conventional method, and FIGS. 12A and 12B show the relationship between the power distribution of the laser beam and the photosensitive reaction area, respectively.

FIGS. 13A and 13B are diagrams for explaining a conventional method, in which A is a laser beam pattern diagram, B is an exposure pattern diagram, and C is a concave portion pattern diagram.

[Explanation of symbols]

1 ... recording mark, 2 ... recording pattern, 3L, 3
H: laser light power distribution curve, 4L, 4H: temperature rise area, 11: recording medium or master disk constituting substrate, 12: heat-sensitive material layer, 12a: first material layer, 12b ... 2nd material layer, 12s ... Transformed part,
13 ... laser beam, 15 ... fine irregularities, 16 ...
Master, 41 ... holding means, 42 ... laser light source unit,
43 ... modulation means, 44 ... condensing lens system, 45 ...
..Optical system, 46 ... low-speed modulator, 47 ... high-speed modulator, 48 ... mirror, 101 ... substrate, 102 ...
..Photosensitive material layer, 103 laser light, 104
・ Condenser lens, 201, 202 ・ ・ ・ Laser light power distribution curve

Claims (23)

[Claims] 1. A recording medium comprising a recording pattern having a narrower width than an optical spot having a wavelength used for reproduction and having a multi-level recording mark dedicated to reproduction of two or more widths. 2. A method for manufacturing a recording medium in which a recording pattern having a narrower width than an optical spot having a wavelength used for reproduction and having a multi-level recording mark dedicated to reproduction of two or more widths is formed. Forming a heat-sensitive material layer on a substrate constituting a medium; and applying a laser beam to the heat-sensitive material layer at two or more levels of intensity or intensity modulated at a frequency higher than the period of the recording pattern. Irradiating with at least one kind of discontinuous irradiation to form a deteriorated portion of a pattern corresponding to the recording pattern; and developing the heat-sensitive material layer to pattern the heat-sensitive material layer. Manufacturing method of recording medium. 3. The heat-sensitive material layer has a laminated structure of at least a first material layer and a second material layer made of mutually different constituent materials. The constituent material of the first and second material layers is interdiffused or dissolved to form the altered portion by mixing or reacting the constituent materials of the at least first and second material layers. 3. The method for manufacturing a recording medium according to item 2. 4. The method according to claim 2, wherein the laser light is a semiconductor laser light. 5. The method according to claim 2, wherein the laser light is a blue-violet laser light. 6. The method according to claim 2, wherein a constituent material of the heat-sensitive material layer is an inorganic material. 7. The method according to claim 2, wherein fine irregularities including the recording mark are formed on the substrate using the patterned heat-sensitive material layer as a mask. 8. The method of manufacturing a recording medium according to claim 2, wherein fine irregularities including the recording marks are formed on the substrate by reactive ion etching using the patterned heat-sensitive material layer as a mask. Method. 9. The method according to claim 2, wherein the development in the patterning step of the heat-sensitive material layer is performed using an aqueous solution of tetramethylammonium hydroxide. 10. A method for producing a master for producing a recording medium, in which a recording pattern having a narrower width than an optical spot having a wavelength used for reproduction and having a multi-level recording mark dedicated to reproduction of two or more widths is formed. Forming a heat-sensitive material layer on a substrate constituting a master for a recording medium; and applying two or more types of laser light to the heat-sensitive material layer, the laser light being modulated to a frequency higher than the period of the recording pattern. Irradiating with a level of intensity or two or more types of discontinuous irradiation to form a deteriorated portion of a pattern corresponding to the recording pattern; and developing the heat-sensitive material layer to pattern the heat-sensitive material layer. A method for producing a master for producing a recording medium, comprising: 11. The heat-sensitive material layer has a laminated structure of at least first and second material layers made of mutually different constituent materials, and the temperature rise due to the laser beam irradiation causes mutual diffusion or melting to produce the at least first heat-sensitive material layer. 11. The modified material according to claim 10, wherein the constituent materials of the first and second material layers are mutually diffused or dissolved to form the altered portion by mixing or reacting the constituent materials of the first and second material layers. A method for producing a master for producing a recording medium according to the above. 12. The method according to claim 10, wherein the laser beam is a semiconductor laser beam. 13. The method according to claim 10, wherein the laser beam is a blue-violet laser beam. 14. The method according to claim 10, wherein a constituent material of the heat-sensitive material layer is an inorganic material. 15. The master for producing a recording medium according to claim 10, wherein a pattern corresponding to the fine irregularities including the recording marks is formed on the substrate using the patterned heat-sensitive material layer as a mask. Production method. 16. The recording medium according to claim 10, wherein fine irregularities including the recording marks are formed on the substrate by reactive ion etching using the patterned heat-sensitive material layer as a mask. Master disc manufacturing method. 17. The method according to claim 10, wherein the development of the heat-sensitive material layer in the patterning step is performed with an aqueous solution of tetramethylammonium hydroxide. 18. An apparatus for manufacturing a recording medium on which a recording pattern having a width narrower than an optical spot having a wavelength used for reproduction and having a multi-level recording mark dedicated to reproduction of two or more widths is formed. A holding unit for holding a substrate constituting a recording medium having a heat-sensitive material layer adhered to one main surface; a laser light source unit; and a laser light modulation unit. A recording data signal for forming the recording pattern by the modulating means and a signal having a frequency higher than the period of the recording pattern, and modulating the recording material signal to form a deteriorated portion of a pattern corresponding to the recording pattern on the heat-sensitive material layer. An apparatus for manufacturing a recording medium, comprising: 19. The apparatus according to claim 18, wherein said modulating means comprises a high-speed modulator and a low-speed modulator. 20. The manufacturing method of a recording medium according to claim 18, wherein said laser light source section is made of a semiconductor laser, and said modulating means is configured to modulate an injection current to said semiconductor laser. apparatus. 21. An apparatus for manufacturing a master for manufacturing a recording medium on which a recording pattern having a width narrower than an optical spot having a wavelength used for reproduction and having a multi-level recording mark dedicated to reproduction of two or more widths is formed. Holding means for holding a substrate constituting a recording medium having at least one main surface on which a heat-sensitive material layer is adhered, a laser light source section, and laser light modulation means; and a laser from the laser light source. The light is modulated by a recording data signal that forms the recording pattern by the modulating means, and a signal having a frequency higher than the period of the recording pattern, and the heat-sensitive material layer has a deteriorated portion of a pattern corresponding to the recording pattern. An apparatus for producing a master for producing a recording medium, wherein the apparatus is formed. 22. An apparatus according to claim 21, wherein said modulating means comprises a high-speed modulator and a low-speed modulator. 23. The recording medium manufacturing method according to claim 21, wherein said laser light source section is composed of a semiconductor laser, and said modulating means is configured to modulate an injection current to said semiconductor laser. Master production equipment.