JPH0252329B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an information recording member in which convex portions are formed by irradiation with an energy beam such as a laser beam, and more specifically, to a master disc or information recording member for producing an information recording medium. The present invention relates to an information recording member used as a recording medium itself.

[Technical background of the invention and its problems]

Writable optical information recording media, that is, disc-shaped recording media called optical discs in which information signals are recorded and reproduced by laser beam irradiation, are used for stable tracking during recording and reproduction, and for stable tracking during recording and reproduction. Because of the need to increase the density (track density), media in which optically distinguishable continuous spiral protrusions or depressions are formed on the recording layer are often used on the substrate (disk substrate). A disk substrate with such continuous spiral protrusions or depressions is
Conventionally, a stamper on which the convex or concave portions are transferred by a method such as electroforming is produced from a master disk on which continuous spiral convex or concave portions are formed, and this stamper is used to perform injection molding, compression molding, casting, etc. It is manufactured by transferring the convex portions or concave portions onto the disk substrate using a method.

On the other hand, a master disc having concave or convex portions is generally manufactured by the following method. That is, a Cr film is deposited on a flat substrate such as glass, and a photoresist is applied thereon using a spinner. Next, while rotating this substrate, a laser beam focused to about 1 μmφ is irradiated onto the photoresist while moving in the substrate radial direction at a predetermined feed rate, thereby performing continuous spiral exposure. Then, further development and baking are performed to obtain a master disc.

However, with this master disk manufacturing method, it is difficult to form uniformly shaped convex portions or concave portions over the entire surface of the substrate. The shape of the convex or concave portions to be formed on the substrate is approximately 1000 Å, which is 1/8 of the wavelength of the semiconductor laser normally used, which is approximately 8000 Å, in order to enable stable tracking.
The width is required to be approximately 1 μm. Also,
The size of the substrate needs to be approximately 30 cmφ or more from the viewpoint of recording capacity. However, the spinner coating method is a technique that is normally used for coating films with a thickness of 1 to 2 μm or more, and it is extremely difficult to form a uniform coating film of 1000 Å on the entire surface of a large-area substrate such as 30 cm diameter using this method. Therefore, partial peeling is unavoidable. Furthermore, even a slight amount of dust in the atmosphere that adheres to the substrate surface can cause serious coating unevenness. Furthermore, it is extremely difficult to uniformly develop such a thin photoresist over the entire area. Therefore, it is difficult to produce a master disc with well-formed continuous spiral protrusions or depressions for tracking using the photoresist method using spinner coating.
It was an almost impossible goal.

[Purpose of the invention]

An object of the present invention is to provide an information recording member that is suitable as a master material for manufacturing a master in which continuous spiral convex portions are uniformly and well-controlled over the entire surface.

[Summary of the invention]

The information recording member according to the present invention forms a convex portion by irradiation with an energy beam such as a laser beam, and includes a first layer having an energy absorbing property and a gas releasing property on a substrate, and a thermal expansion coefficient. It is characterized by sequentially forming a second layer made of a metal with a large coefficient of thermal expansion and a third layer made of a metal with a small coefficient of thermal expansion and high extensibility.

When an information recording member with this structure is irradiated with an energy beam, such as a laser beam,
Part of the laser beam is reflected, and the rest is reflected in the third layer.
It is absorbed by the second layer and the first layer, locally heating these layers. Since the first layer has energy absorbing properties and gas liberating properties, it liberates and releases gas when irradiated with a laser beam. The pressure of this released gas acts to push up the second and third layers, forming a convex portion in the laser beam irradiation area.

Here, since the second layer has a large coefficient of thermal expansion, the first layer
The large thermal expansion of the layer together with the emitted gas pressure causes the third layer to form a large convex deformation. Since the third layer has a low coefficient of thermal expansion but is highly stretchable, the formed convex portions are permanent.

〔Effect of the invention〕

According to the present invention, unlike a photoresist applied by a spinner, all of the first layer, second layer, and third layer can be formed by a normal thin film forming method such as sputtering or vapor deposition. In a clean condition free of impurities such as dust in the atmosphere, and without the occurrence of peeling parts,
It can be formed to have a uniform thickness. Furthermore, since the convex portion is formed using the pressure of the gas released from the first layer by heating with a laser beam etc. and the difference in the characteristics of the second layer and the third layer, the desired shape (height,
A convex portion of width) can be easily obtained.

In other words, when a highly extensible metal film is directly formed on the first layer, the height of the convex portion depends almost only on the magnitude of the gas pressure because such a metal film generally has a small coefficient of thermal expansion. If there is a second layer made of a metal with a large coefficient of thermal expansion below this, deformation with a large height of the convex portion can be obtained. Furthermore, if only the second layer is formed on the first layer without forming the third layer made of a highly extensible metal, the height of the convex portion will temporarily deform to a large extent when irradiated with a laser beam or the like. If irradiation with a laser beam or the like is stopped, the material will shrink, whereas if a third layer is provided thereon, a large deformation in the height of the convex portion will be permanently formed due to its stretchability.

Therefore, according to the present invention, it is possible to form a convex portion having a uniform and good shape over the entire surface of the substrate.

[Embodiments of the invention]

FIG. 1 is a sectional view of an information recording member according to the present invention. A first layer 12 having energy absorbing properties and gas releasing properties is formed on a glass substrate 11, and a second layer 13 made of a metal having a large coefficient of thermal expansion is formed thereon.
is formed, and a third layer 14 made of a metal having a low coefficient of thermal expansion and high extensibility is further formed thereon. The first layer 12 is made of so-called low melting point metals such as Te and Bi whose melting points are below 600°C, and C, N,
A material containing at least one of H and O is suitable, and this can be achieved by sputtering the above-mentioned low melting point metal target in a vacuum with a plasma of a gas such as CH ₃ , NH ₃ , CO ₂ or H ₂ . can be formed. For example, a 1000 Å thick film was formed by sputtering a Te target with CH ₄ gas plasma.
A thin film with a component ratio of Te ₅₀ C ₃₀ H ₂₀ absorbs 40% of light energy at a wavelength of 8300 Å, and when heated in air to 150°C or higher, it releases gas with a weight loss of 30%.

The second layer 13 includes Zn, Sb, Cd, Tl, Mg, Al,
A thin film containing at least one of Mn and Ag is suitable, and a target of these metals can be sputtered with Ar gas plasma in a vacuum, or
It can be formed by vacuum deposition.

The third layer 14 is Au, Pd, Pt, Ti, Cr, Ta,
A thin film containing at least one of Mo and Zr is suitable, and like the second layer, this can also be formed by a normal thin film forming method such as sputtering or vacuum deposition.

Next, an embodiment of the master disc production process using the information recording member having the structure shown in FIG. 1 will be described. First, 35
thickness as the first layer 12 on the glass substrate 11 of cmφ
A 4000 Å Te ₅₀ C ₃₀ H ₂₀ film was formed. Next, as the second layer 13, Zn has a high coefficient of thermal expansion of 40×10 ^-6 deg ^-1 .
A film was formed to a thickness of 200 Å, and then an Au film having a small thermal expansion coefficient of 14×10 ⁻⁶ deg ⁻¹ but highly stretchable was formed to a thickness of 200 Å as the third layer 14. T ₅₀ C ₃₀ H ₂₀
The film was formed by sputtering a Te target with CH ₄ gas plasma, and the Zn film and Au film were formed by sputtering a Te target with CH 4 gas plasma.
The Au target was formed by sputtering with Ar gas plasma. In this case, it is desirable to immediately form the second layer 13 and the third layer 14 in succession in the same vacuum container after forming the first layer 12 in order to avoid being affected by dust in the atmosphere. .

Next, as shown in FIG. 2a, three types of layers 12, 1
The substrate 11 on which the patterns 3 and 14 are formed is taken out from the vacuum container, placed and fixed on the rotating support base 21, and set at a linear speed of 6.
The third layer 14 was irradiated with a semiconductor laser beam 23 rotated at m/sec and focused to 1 μmφ by a lens 22 while moving in the radial direction at a predetermined speed.
However, the laser beam 23 was a continuously modulated beam with a power of 10 mW.

By irradiating this laser beam 23, as shown in FIG.
As shown in FIG.
It was observed using a scanning electron microscope that a continuous spiral convex portion 24 having a uniform height of 0.1 μm and a bottom width of 1.1 μm was formed on the surface.

As a comparative example, the thickness of the first layer is 4000Å.
A second layer with only a 200 Å Zn film and a 200 Å Au film formed on the Te ₅₀ C ₃₀ H ₂₀ film were fabricated, and laser beam exposure was performed in the same manner as above. However, no matter how we change the conditions such as linear velocity and laser beam power, the height of the convex part cannot be made more than 0.05 μm in the former case.
In the latter case, it was not possible to increase the thickness to 0.03 μm or more.

As another example, a Te ₅₀ C ₃₀ N ₅ H ₁₅ film with a thickness of 3500 Å is formed as the first layer 12 on a glass substrate 11 with a diameter of 30 cm, and a Cd film (with a thermal expansion coefficient of 30 ×10 ⁻⁶ deg ⁻¹ ), and a Ti film (thermal expansion coefficient 9×10 ⁻⁶ deg ⁻¹ ) was further formed as the third layer 14. When laser beam exposure was performed in the same manner as in the previous example, a continuous spiral convex portion with a good shape and a height of 0.09 μm and a width at the bottom of 1.1 μm was formed.

In addition, as the second layer 13, Sb (thermal expansion coefficient
37×10 ^-6 deg ^-1 ), Tl (28×10 ^-6 deg ^-1 ), Mg (same
26×10 ^-6 deg ^-1 ), Al (24×10 ^-6 deg ^-1 ), Mn (same
22×10 ^-6 deg ^-1 ), Ag (20×10 ^-6 deg ^-1 ), etc. can be used. In addition, the third layer 14 is Pd (thermal expansion coefficient 12
×10 ^-6 deg ^-1 ), Pt (9 × 10 ^-6 deg ^-1 ), Ti (9 ×
10 ^-6 deg ^-1 ), Ta (7 × 10 ^-6 deg ^-1 ), Cr (6 ×
10 ^-6 deg ^-1 ), Mo (5 × 10 ^-6 deg ^-1 ), Zr (5 ×
10 ^-6 deg ^-1 ), etc. can be used. 2nd layer 13, 3rd layer
It was confirmed that no matter which combination of these metal films was used for the layer 14, well-shaped protrusions with a height of 0.07 μm or more were formed.

Next, a process for manufacturing an information recording medium having continuous spiral convex portions or concave portions using the master disc shown in FIG. 2b will be described. The third layer 14 has a continuous spiral convex portion 24 as shown in FIG. 2b.
As shown in FIG. 3A, a polytetrafluoroethylene film with a thickness of about 100 Å is first formed as a peeling layer 31, and then an Au film with a thickness of about 300 Å is formed as an electrode 32 for electroforming. After that, a metal plate 33 made of Ni or the like was formed by electroforming. metal plate 33
The thickness is about 300 μm. Thereafter, by using the metal plate 33 as an electrode and separating the electrode 32 and the peeling layer 31 by electrolytic cleaning, the convex portion formed on the third layer 14 as shown in FIG. 3b is removed. A stamper was manufactured, which was composed of an electrode 32 having a concave portion 34 in which the shape of 24 was inverted and transferred, and a metal plate 33. At this time, the electrode 32 was in close contact with the metal plate 33 extremely firmly, and no trace of the film material of the peeling layer 31 was observed on its surface. Also, the height of the recess 34 on the surface of this stamper is 0.1 μm.
m, and the width was 1 μm.

Next, using this stamper, an acrylic disk substrate 35 as shown in FIG. 3c was manufactured by injection molding. On this substrate 35, a continuous spiral convex portion 36 having a uniform height of 0.09 μm was formed over the entire surface. This disk board 35
By forming a recording layer 37 thereon, an optical information recording medium is obtained.

In the above embodiment, an information recording medium was manufactured from the master disk shown in FIG. 2b via a stamper, but it is also possible to use the master disk as it is as a stamper. An example thereof will be described below.

That is, first, an acrylic ultraviolet curable resin is applied onto the master disk shown in Figure 2b, then a pre-formed flat acrylic substrate and a glass substrate are layered, and ultraviolet rays with an intensity of 80 W/cm are applied for 27 seconds from the upper glass plate side.
The ultraviolet curing resin layer was cured by irradiation. Next, when the acrylic substrate was peeled off from the master, the ultraviolet curing resin layer was extremely firmly attached to the acrylic substrate, and no trace of the Au film of the third layer 14 was observed on its surface. The thickness of the ultraviolet curing resin layer on the acrylic substrate was 100 μm, and a continuous spiral recess 42 with a uniform depth of 0.1 μm was formed on its surface. The optical information recording medium shown in FIG. 4 is obtained by forming a recording layer 43 on a disk substrate 41 made of an acrylic substrate to which the ultraviolet curable resin layer thus obtained is attached.

The information recording member according to the present invention can be used not only as a master disc but also as an optical information recording medium itself. An example of this will be described below. A polycarbonate substrate with a diameter _{of 12} cm _is used as the substrate 11 in FIG.
An Al film with a thickness of 100 Å was formed as the layer 13, and a Cr film with a thickness of 200 Å was formed as the third layer 14 to obtain an optical information recording medium. Laser beam exposure was performed on this medium in the same manner as in the master production process shown in FIG. However, the rotation speed of the medium was constant at 1800 rpm, the wavelength of the laser beam was 8200 Å, and the power was 15 mW at the film surface. Further, the laser beam was pulse-modulated according to the information signal to be recorded. As a result of this laser beam exposure, discontinuous spiral convex portions (pit rows) were formed on the medium surface, the length of which varied according to the information signal. The height of the convex shape is
The width at the bottom was 1 μm.

When the medium on which information was recorded in the form of pit rows was rotated at 1800 rpm, the same speed as during recording, and the presence or absence of convex portions was detected using a 1 mW continuous laser beam to perform reproduction, the S/N of the reproduced signal was A relatively good value of 38dB was obtained.

This invention can be implemented with various other modifications.For example, instead of forming continuous spiral convex portions on the master disc, exposure may be performed with a laser beam pulse-modulated by an information signal to create pits according to the information signal. A disk substrate is formed by injection molding using this master or a stamper made from this, and a reflective film such as an Al film is formed on it to obtain a read-only optical information recording medium. You can also do that.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an information recording member according to an embodiment of the present invention, FIGS. 2a and 2b are diagrams showing the process of manufacturing a master disc from the information recording member of FIG. 1, and FIGS. b and c are diagrams showing the process of producing an information recording medium from the master disc in Fig. 2b via a stamper;
FIG. 4 is a cross-sectional view of an information recording medium manufactured using the master disc of FIG. 1b as a stamper. 11...Substrate, 12...First layer, 13...Second
Layer, 14... Third layer, 21... Rotating support base, 22
... Lens, 23 ... Laser beam, 24 ... Convex portion, 31 ... Peeling layer, 32 ... Electroforming electrode, 33
. . . Metal plate, 34 . . . Recess, 35 . . . Disk substrate, 36 .

Claims (1)

[Scope of Claims] 1. In an information recording member in which a convex portion is formed by irradiation with an energy beam, a first layer having an energy absorbing property and a gas releasing property on a substrate, and a second layer made of a metal having a large coefficient of thermal expansion. 1. An information recording member comprising a layer and a third layer made of a highly extensible metal having a small coefficient of thermal expansion. 2 The first layer is made of metal with a melting point of 600℃ or less, C, N,
The information recording member according to claim 1, characterized in that it contains at least one of H and O. 3 The second layer is Zn, Sb, Cd, Tl, Mg, Al, Mn,
The information recording member according to claim 1, characterized in that it contains one or more types of Ag. 4 The third layer is Au, Pd, Pt, Ti, Cr, Ta, Mo,
The information recording member according to claim 1, characterized in that it contains one or more of Zr.