JP2656296B2 - Information recording medium and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an information recording medium capable of recording and reproducing optical information at high speed and at a high density by laser light, and a method of manufacturing the same.

(Prior Art) As a conventional information recording medium for recording / reproducing high-density information by using a laser beam, for example, as shown in FIG. 4, it is made of polycarbonate or the like in which a tracking groove is provided in advance. It is well known that a recording film 11 made of a low oxide of Te or Te and an organic compound is formed on a transparent substrate 1. In an information recording medium using the recording film 11 made of such a low oxide of Te or the like, recording is performed by evaporating a region irradiated with laser light to form pits.

Recently, an information recording medium using a recording film made of a material capable of causing a phase change by laser light irradiation has been announced.

However, with conventional evaporation / drilling type information recording media,
If the laser output is high, recording is possible, but if a low-output laser light source such as a semiconductor laser is used to reduce the size and simplification of the recording / reproducing device, sufficient sensitivity cannot be obtained. there were. In addition, handling can be facilitated if a protective substrate is bonded directly to the recording film formed on the transparent substrate via an adhesive, but the recording film is not used for the evaporation / perforated information recording medium. In order to evaporate, a so-called air sandwich type structure must be used, which is disadvantageous in terms of handling.

On the other hand, in the conventional phase-change type information recording medium, the material constituting the recording film is complicated, which is disadvantageous in terms of productivity, cost, and the like.

In particular, for an information recording medium such as an optical card, it can be said that it is essential to develop a recording film that is easy to manufacture and that allows low power writing.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned problems, and can perform recording with sufficient sensitivity even with a low-power laser beam such as a semiconductor laser, and has good productivity and low cost. The purpose of the present invention is to provide an information recording medium.

[Structure of the Invention] (Means and Action for Solving the Problems) In the information recording medium of the present invention, a low oxide of nickel represented by NiO _x (0.1 <x <0.8) is used as a recording film. It is characterized by the following.

The low oxide of nickel represented by NiO _x (where 0.1 <x <0.8) used as a recording film in the present invention shows high sensitivity to laser light irradiated at the time of recording, and has a transmittance, Optical characteristics such as reflectance change. In particular, when _x of NiO _x is 0.3 to 0.7, the sensitivity is high. Therefore, recording can be performed with sufficient sensitivity even when a laser light source having a small output such as a semiconductor laser is used. Even if a structure in which a NiO _x recording film is formed on a substrate and another substrate is bonded directly to the recording film via an adhesive layer can be used, sufficient sensitivity can be maintained without any problem. Becomes extremely easy.

Further, the method for producing an information recording medium of the present invention includes forming a recording film made of a low oxide of nickel represented by NiO _x (0.1 <x <0.8) on a substrate, at least using nickel as a target. A method of performing reactive sputtering with a mixed gas containing an argon gas and an oxygen gas, a method of performing a reactive deposition with an oxygen gas using nickel as a target, a method of performing vacuum deposition using a nickel oxide as a target, or argon using a nickel oxide as a target There is a method of performing sputtering by gas.

According to the method of the present invention, the composition range of the recording film to be formed is wide and the margin of the manufacturing condition is large, which is advantageous for improving the productivity.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, the information recording medium shown in FIG. 1 or FIG. 2 was manufactured.

The information recording medium shown in FIG. 1 has a NiO _x recording film 2 formed on a polycarbonate transparent substrate 1 having a thickness of 1.2 mm and provided with tracking grooves in advance.

The information recording medium shown in FIG.
m NiO _x recording film 2 on a transparent substrate 1 made of polycarbonate
And a 400 μm-thick protective film 4 made of polycarbonate is directly bonded on the recording film 2 via a urethane-based adhesive layer 3 and is further punched into a standard card size.

Example 1 First, the following experiment was conducted in order to investigate the optical characteristics of the low oxide of nickel itself represented by NiO _x constituting the recording film. That is, a NiO _x film was formed on a glass substrate by RF reactive sputtering using a mixed gas of argon gas and oxygen gas with nickel as a target. At this time, _x of NiO _x was changed from 0 to 1.0 by changing the flow ratio of the argon gas and the oxygen gas in the mixed gas. The applied voltage was set to 500 W and the gas pressure was set to 5 mTorr. Under these conditions, the deposition rate of the NiO _x film is 5 to 25 nm.
/ min.

The NiO _x films having different compositions were irradiated with light of 830 nm, which is one of the wavelengths of the semiconductor laser, and the light absorptance was measured. The results shown in FIG. 3 were obtained.
As is clear from FIG. 3, the NiO _x film shows a high absorptance when x is in the range of 0.1 to 0.8, and shows a particularly high absorptivity when x is in the range of 0.3 to 0.7.

Next, when the NiO _x film having x of 0.1 to 0.8 was irradiated with a laser beam having a wavelength of 830 nm, a change in transmittance of the irradiated portion was recognized, and it was found that optical recording was possible.

The same results as described above were obtained for light having a wavelength of 700 to 900 nm, indicating that optical recording was possible.

According to X-ray diffraction, the NiO _x film shows an amorphous structure or a crystalline structure containing Ni and NiO, but recording was possible with any of the structures.

Example 2 RF reactive sputtering was performed by using a mixed gas of argon gas and oxygen gas with nickel as a target, and a NiO _x recording film 2 was formed on a 1.2 mm-thick polycarbonate transparent substrate 1 provided with a tracking groove in advance. Was formed to produce the information recording medium shown in FIG. As the film forming conditions, the applied voltage was 500 W, the gas pressure was 5 mTorr, and the argon gas flow rate was 1
The oxygen gas flow rate was set at 8.5 sccm, the flow rate of oxygen gas was set at 1.5 sccm (flow ratio of argon and oxygen = 12: 1), and the deposition rate of NiO _x was 18 nm / min. The formed NiO _x recording film 2 has a thickness of 80 nm and x =
0.5.

In this information recording medium, the transmittance of light with a wavelength of 830 nm is 20
%Met. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film 2 to a beam diameter of 5 μm, and irradiated with an output of 7 mW. As a result, the transmittance of light having a wavelength of 830 nm in the irradiated portion changed to 65%.

Example 3 Nickel oxide as a target and argon gas
RF sputtering is performed, and NiO is placed on a polycarbonate transparent substrate 1 having a thickness of 1.2 mm in which tracking grooves are provided in advance.
_{The x} recording film 2 was formed, and the information recording medium shown in FIG. 1 was manufactured. As the film forming conditions, an applied voltage of 500 W and a gas pressure of 5 m
At Torr, the deposition rate of NiO _x was 10 nm / min. The formed NiO _x recording film 2 had a thickness of 80 nm and x = 0.7.

In this information recording medium, the transmittance of light with a wavelength of 830 nm is 25
%Met. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film 2 to a beam diameter of 5 μm, and irradiated with an output of 7 mW. As a result, the transmittance of light having a wavelength of 830 nm in the irradiated portion changed to 65%.

Example 4 Vacuum evaporation was performed using nickel oxide as a target, and a NiO _x recording film 2 was formed on a 1.2 mm-thick polycarbonate transparent substrate 1 provided with tracking grooves in advance, and the information recording shown in FIG. A medium was prepared. As the film forming conditions, the degree of vacuum was set to 5 × 10 ⁻⁶ Torr, and the deposition rate of NiO _x was 30 nm.
/ min. The thickness of the formed NiO _x recording film 2 is 80 nm.
And x = 0.5.

In this information recording medium, the transmittance of light with a wavelength of 830 nm is 20
%Met. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film 2 to a beam diameter of 5 μm, and irradiated with an output of 7 mW. As a result, the transmittance of light having a wavelength of 830 nm in the irradiated portion changed to 65%.

Example 5 Reactive deposition by oxygen gas was performed using nickel as a target, and a 1.2 mm thick groove was provided in advance for tracking.
A NiO _x recording film 2 was formed on a transparent substrate 1 made of polycarbonate described above to produce an information recording medium shown in FIG. As the film forming conditions, the pressure during the gas inflow was set to 5 × 10 ⁻⁴ Torr,
The deposition rate of NiO _x was 35 nm / min. The formed NiO _x recording film 2 had a thickness of 80 nm and x = 0.7.

In this information recording medium, the transmittance of light with a wavelength of 830 nm is 25
%Met. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film 2 to a beam diameter of 5 μm, and irradiated with an output of 7 mW. As a result, the transmittance of light having a wavelength of 830 nm in the irradiated portion changed to 65%.

Example 6 A transparent transparent substrate 1 made of polycarbonate and having a thickness of 400 μm, which was pre-processed by performing RF reactive sputtering using a mixed gas of argon gas and oxygen gas with nickel as a target.
A NiO _x recording film 2 was formed thereon. As the film forming conditions, the applied voltage was 500 W, the gas pressure was 5 mTorr, and the argon gas flow rate was 18.5.
The sccm and the oxygen gas flow rate were set to 1.5 sccm (flow ratio of argon to oxygen = 12: 1), and the deposition rate of NiO _x was 18 nm / min. The formed NiO _x recording film 2 has a thickness of 80 nm and x = 0.
It was five. At this stage, the transmittance of light with a wavelength of 830 nm is 20%
Met. After bonding a protective film 4 made of polycarbonate having a thickness of 400 μm directly onto the NiO _x recording film 2 via a urethane-based adhesive 3, it is punched out to a standard card size, and the information recording medium shown in FIG. Produced.

In this information recording medium, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side was 35%. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film to a beam diameter of 5 μm from the side of the transparent substrate 1 and irradiated with an output of 10 mW. As a result, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side changed to 12%.

Example 7 Using nickel oxide as a target and argon gas
An information recording medium shown in FIG. 2 was produced in the same manner as in Example 6 except that RF sputtering was performed. As the film forming conditions, the applied voltage was set to 500 W, the gas pressure was set to 5 mTorr,
The deposition rate of the O _x was 10nm / min. The formed NiO _x recording film 2 had a thickness of 80 nm and x = 0.7. At the stage after the film formation, the transmittance of light with a wavelength of 830 nm was 25%.

In this information recording medium, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side was 35%. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film to a beam diameter of 5 μm from the side of the transparent substrate 1 and irradiated with an output of 10 mW. As a result, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side changed to 12%.

Example 8 An information recording medium shown in FIG. 2 was produced in the same manner as in Example 6 except that vacuum deposition was performed using nickel oxide as a target. As a film forming condition, the degree of vacuum is set to 5 × 10 ⁻⁶ Torr.
, And the deposition rate of NiO _x was 30 nm / min. The formed NiO _x recording film 2 had a thickness of 80 nm and x = 0.5. At the stage after the film formation, the transmittance of light having a wavelength of 830 nm is 2
It was 0%.

In this information recording medium, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side was 35%. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film to a beam diameter of 5 μm from the side of the transparent substrate 1 and irradiated with an output of 10 mW. As a result, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side changed to 12%.

Example 9 An information recording medium shown in FIG. 2 was produced in the same manner as in Example 6, except that reactive deposition using oxygen gas was performed using nickel as a target. As the film forming conditions, the pressure during gas inflow was set to 5 × 10 ⁻⁴ Torr, and the deposition rate of NiO _x was 35.
nm / min. The thickness of the formed NiO _x recording film 2 is 80 nm.
And x = 0.7. At the stage after the film formation, the wavelength 830
The light transmittance of nm was 25%.

In this information recording medium, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side was 35%. Next, GaAlAs laser light having a wavelength of 830 nm was focused on the recording film to a beam diameter of 5 μm from the side of the transparent substrate 1 and irradiated with an output of 10 mW. As a result, the reflectance of light having a wavelength of 830 nm measured from the transparent substrate 1 side changed to 12%.

In addition, it was confirmed that the same results were obtained when the semiconductor laser having a wavelength of 780 nm was used for writing with respect to the information recording media of Examples 2 to 9.

[Effects of the Invention] As described above in detail, according to the present invention, recording can be performed with sufficient sensitivity even to a low-output laser beam such as a semiconductor laser, and the productivity and the reproducibility can be easily obtained. It is possible to provide an information recording medium, and thus reduce the size of the recording device,
A remarkable effect such as reduction in cost can be achieved.

[Brief description of the drawings]

Figure 1 is a sectional view of an information recording medium in Example 2-5 of the present invention, FIG. 2 is a cross-sectional view of an information recording medium in Example 6-9 of the present invention, FIG. 3 is of x NiO _x film Value and wavelength 830nm
And FIG. 4 is a cross-sectional view of a conventional information recording medium. 1 ... transparent substrate, 2 ... NiO _x recording film, 3 ... adhesive layer,
4 ... Protective film.

Continuing on the front page (72) Norio Ozawa, Inventor No. 1, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Hiroshi Ohira No. 1, Komukai Toshiba-cho, Kochi-ku, Kawasaki-shi, Kanagawa Co., Ltd. Inside Toshiba Research Institute (56) References JP-A-63-91835 (JP, A)

Claims (7)

(57) [Claims] In an information recording medium for recording information by irradiating a laser beam, NiO _x (where 0.1 <
x <0.8) An information recording medium using a low oxide of nickel represented by the formula: 2. A recording film comprising a low oxide of nickel represented by NiO _x (0.1 <x <0.8) is formed on a substrate, and another recording film is formed on the recording film directly via an adhesive layer. 2. The information recording medium according to claim 1, wherein 3. The information recording medium according to claim 1, wherein _x of NiO _x constituting the recording film is 0.3 to 0.7. 4. When manufacturing an information recording medium on which information is recorded by irradiating a laser beam, reactive sputtering is performed by using a mixed gas containing at least argon gas and oxygen gas with nickel as a target, and NiO is formed on the substrate. _A method for manufacturing an information recording medium, comprising forming a recording film made of a low oxide of nickel represented by _x (where 0.1 <x <0.8). 5. In manufacturing an information recording medium on which information is recorded by irradiating a laser beam, reactive deposition using oxygen gas is performed using nickel as a target, and NiO _x (0.1 <x <0.8 A method for manufacturing an information recording medium, comprising forming a recording film made of a low oxide of nickel represented by the formula (1). 6. When manufacturing an information recording medium for recording information by irradiating a laser beam, vacuum deposition is performed using nickel oxide as a target, and NiO _x (0.1 <x <0.8) is expressed on a substrate. Forming a recording film made of a low oxide of nickel. 7. In manufacturing an information recording medium for recording information by irradiating a laser beam, sputtering with argon gas is performed using nickel oxide as a target, and NiO _x (0.1 <x <0.8) is formed on the substrate. Forming a recording film made of a low oxide of nickel represented by the following formula: