JP2530400B2 - Information recording medium - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly sensitive information recording medium suitable for application to a high density optical memory device for optically recording and reproducing information.

[0002]

2. Description of the Related Art Conventionally, as an optical information recording medium for optically recording and reproducing information, as a recording layer on a transparent substrate such as glass or plastic, a low melting point metal thin film such as bismuth or tellurium, or a compound thin film thereof is used. The recording layer is formed by depositing and irradiating the recording layer with laser light modulated according to the recorded information to melt and evaporate the thin film to form an information pit and record the information. Is common.

However, such a metal thin film recording layer generally has a high reflectance, and although a low melting point metal is used, in practice, its melting point is relatively high, so that the recording sensitivity is low. is there.

Further, the metal thin film having excellent recording sensitivity is highly toxic and has a serious difficulty in manufacturing or handling thereof.

On the other hand, a recording medium in which an organic dye layer which absorbs a recording laser beam is attached instead of the above-mentioned metal thin film as the recording layer is disclosed in, for example, JP-A-56-16948.

This information recording medium has a reflective film and an organic dye layer on a substrate and records information on it. In this case, although it is improved in terms of toxicity, it is stored for a long time. Those which endure the above have a problem that the recording sensitivity is low. Further, since it is necessary to irradiate the recording laser beam from the surface of this recording layer, there is a problem that the read signal is greatly affected by the presence of dust, scratches, etc. adhering to this surface, and the quality of the signal is deteriorated. .

Further, as another information recording medium, a recording medium which uses an auxiliary layer containing an organic dye or the like in combination with the above-mentioned metal thin film to improve the recording sensitivity is disclosed in, for example, JP-A-54-89605. It is disclosed in the official gazette.

A recording medium having this structure includes a transparent substrate,
The information recording layer comprises an auxiliary layer provided on the transparent substrate and an information recording layer having reflection characteristics provided on the auxiliary layer, and the recording laser beam is applied to the information recording layer through the transparent substrate. The information pits are formed by melting and evaporating this in accordance with the recorded information. The auxiliary layer in this case is
Because it contains organic dye that absorbs laser light, so as to improve the low thermal conversion of laser light generated due but highly reflective metal thin film as described above, occurs exothermic effects in the auxiliary layer Has been done.

However, even in the information recording medium having such a structure, since the recording layer uses a metal thin film having a low melting point, the problem of its toxicity has not been solved.

Furthermore, as another information recording medium, a high melting point thin film and an organic material are used together without relying on the melting and evaporation of the low melting point metal thin film, and the foaming phenomenon due to decomposition and sublimation of the organic material is utilized. The method of recording the data is disclosed in JP-A-56-65340.
No. 6,086,045.

This information recording medium, as shown in FIG.
A light-reflecting material layer 2 was formed on a transparent substrate 1, a light-transmitting material layer 3 was deposited on this light-reflecting material layer 2, and a light absorber layer 4 was deposited on this light-transmitting material layer 3. It has a three-layer structure.
In this case, the light absorber layer 4 includes titanium, platinum, rhodium,
The light transmitting material layer 3 is made of a material having a high melting point, such as gold, nickel, chromium, or vanadium.
It is made of an organic material which is melted, decomposed or sublimated at a temperature lower than at least 300 ° C. to reduce the light energy required for recording and which is transparent to the recording / reading laser light.

Recording on such an information recording medium is
The laser light modulated by the information recording is applied to the light absorber layer 4
It is irradiated from the side and converted into heat energy here,
This heat heats the light-transmitting material layer 3 to generate a decomposition gas therein, and bubbles generated thereby generate a cavity 5 under the light-absorbing agent layer 4 to form a layer 4 for information recording as shown in FIG. Correspondingly, the bulged pit 6 is formed to record the information. In this case, although the above-mentioned problem of toxicity is solved, 1) Since the light absorber layer 4 has high reflectance, the efficiency is poor and the recording sensitivity is not improved so much. 2) Since recording / reading is performed from the side of the light absorber layer 4,
Signal defects increase due to dust and scratches on the surface. 3) Since the recording mode depends on the bulging state in which the thin film light absorber layer 4 is floated by foaming, the light absorber layer 4 is a thin film, and the foamed information recording portion, that is, a pit. The part 6 is mechanically weak and the reliability is low. And the like.

A protective film may be further provided on the light absorbent layer 4 in order to prevent signal defects due to dust, scratches, etc. on the surface of the above item 2). In the case where the protective layer is provided, if it is thick, the bulging deformation due to foaming of the light absorber layer may be suppressed, so that the protective film surface is thick enough to be located outside the focal depth of the focused beam system objective lens. Can not do it.

[0014]

DISCLOSURE OF THE INVENTION The present invention provides an information recording medium which has solved the above-mentioned problems, that is, has no toxicity and is highly sensitive.

[0015]

The present invention, as shown in the schematic cross-sectional view of one example thereof in FIG. 1, is formed on a substrate 11, and is formed on this substrate 11 to absorb recording light and generate thermal energy. A light absorbing layer 12 made of a thermoplastic resin layer containing a light absorbing agent to be converted and a foaming agent which is thermally decomposed to emit a substrate, and a light reflecting layer 13 formed adjacently on the light absorbing layer 12. And the recording light irradiated through the substrate 11 is efficiently absorbed by the light absorbing agent in the light absorbing layer, so that the light absorbing layer 12 itself is deformed in its light emitting portion. Record information.

[0016]

In the present invention, the information pit 15 is formed, that is, recorded by the above-mentioned deformation caused by the light irradiation.

In the present invention, the light absorbing function and the foaming function are performed by the same layer 12. Therefore, at the time of recording, the light is efficiently converted into heat by the light absorbing agent, and this is efficiently transmitted to the foaming agent, which can be foamed, and the recording with high sensitivity to the deformation is performed.

Further, since the light absorbing layer 12 itself expands and expands to form the pits 15, the pits 15 are formed under the light reflecting layer 13 as in the conventional case described with reference to FIG. The pits are formed with almost no cavities, which increases the mechanical strength of the pits. Therefore, it is possible to obtain a medium having high reliability and excellent storage stability.

Further, according to the present invention, the pit 15 is formed because the reflection layer 13 is locally lifted by the volume expansion of the light absorption layer 12 itself to form the pit 15.
Can be surely lifted, and accordingly, the protective film 14 does not deteriorate in sensitivity even if the protective film 14 is thick enough to protect it.

Further, in the information recording medium according to the present invention, since the recording and reading light can be irradiated from the side of the substrate 11, even if dust or scratches are present on the protective film 14, it causes a signal defect. It is possible to record and read information with a high S / N without any trouble.

[0021]

Embodiments of the information recording medium according to the present invention will be described in detail.

As shown in FIG. 1, the present invention is an organic material which absorbs recording light, for example recording laser light, on a substrate 11 which is transparent to recording and reading light, for example recording laser light and reading laser light. A light absorbing layer 12 made of, for example, a thermoplastic resin layer containing a light absorbing agent such as a dye or pigment and a foaming agent, and a light reflecting layer 13 having a high reflectance for laser light on the light absorbing layer 12. Further, if necessary, a protective film 14 for protecting the light reflecting layer 13 from corrosion is provided thereon.

As the light absorbing agent in the light absorbing layer 12, an organic dye or organic pigment whose light absorbing wavelength is substantially the same as the wavelength of the recording laser light is used, and the foaming agent is decomposed by heating to decompose N ₂ , A substance that generates a gas such as CO ₂ is used.

Information is recorded on and read from the information recording medium having such a structure by irradiating recording laser light and reading laser light from the side of the substrate 11 as shown by an arrow a in FIG. That is, at the time of recording, focused laser light modulated according to an information recording signal is irradiated from the side of the substrate 11 so as to be focused on the light absorbing layer 12. In this way, the light energy absorbed by the light absorbing agent such as the organic dye or pigment in the light absorbing layer 12 is converted into heat energy, and this layer is heated in a pattern according to the information recording signal. At this time, the temperature of this layer rises and the light absorption layer 1
The second base material, that is, the thermoplastic resin is locally plasticized and the foaming agent is thermally decomposed to generate a gas, so that fine bubbles are generated in the layer 12 to cause an apparent volume expansion. Here, as shown in FIG. 2, pits 15 are formed by locally bulging the light reflection layer 13 and the protective film 14 on the light reflection layer 13 to thereby perform recording. That is, in this pit 15, optical characteristics such as light reflection and interference are observed in the pit 1.
A portion different from the portion other than 5 is generated and the recording is performed.

Further, in order to read the recording from the medium on which the recording is made, that is, the recording pit 15 is formed, the light read from the substrate 11 side, for example, the reading is performed as shown by an arrow b in FIG. Irradiate with laser light,
For example, a change in optical characteristic due to a difference in thickness and density of the pit 15 from others is detected by reflection by the light reflection layer 13, interference, etc., and the information is read.

The substrate 11 is made of a disc that is transparent to both recording and reading laser beams, such as an acrylic resin or a polycarbonate resin and has a thickness of about 1 mm to 2 mm.
The light absorption layer 12 on the base 11 is made of a thermoplastic resin such as acrylic or styrene and has a coating thickness of 200 to 30.
It is applied to about 100 Å, preferably about 1000 Å. As the light absorber contained in the thermoplastic resin of the light absorbing layer 12, for example, when the recording laser is a semiconductor laser, a dithiobenzoin-based metal complex having a light absorbing property at a wavelength around 8000 Å is used. As the foaming agent, for example, azobisisobutyrodinitrile, 1,1'-azobis- (cyclohexane-1-carbonitrile), which thermally decomposes at 100 to 3000 ° C. to efficiently generate N ₂ or CO ₂ gas, etc. Can be used.

These light absorbing agent and foaming agent are mixed with a thermoplastic resin dissolved in a similar organic solvent to form a base 11
It can be applied by spin coating.

The light reflecting layer 13 is made of, for example, a vacuum evaporation method and has a thickness of 100 to 1000 Å nickel, aluminum,
It is composed of a metal thin film such as chromium having a high reflectance for at least the reading light.

The protective film 14 can be formed by depositing a metal oxide by, for example, a vacuum vapor deposition method or by coating a resin by a spin coating method.

Example 1 A light absorbing layer 12 having a coating thickness of 1400Å was coated on a substrate 11 made of a polycarbonate resin disk having a thickness of 1.5 mm. The light absorbing layer 12 is made of an acrylic resin dissolved in an organic solvent, a dithiobenzoin-based metal complex as a light absorbing agent, and azobisisobutyrodinitrile as a foaming agent.
It was formed by mixing it with 1'-azobis- (cyclohexane-1-carbonitrile) and coating it on the substrate 11 by spin coating. Then, an Al layer having a thickness of 500 Å was formed as a light reflecting layer 13 on the light absorbing layer 12 by vacuum vapor deposition. Then, a metal oxide was formed thereon as a protective film 14 by a vacuum vapor deposition method.

As described above, when the information recording medium having such a structure is irradiated with the recording laser light from the side of the substrate 11, this light is absorbed in the light absorbing layer 12 and is converted into heat, whereby the light in the layer 12 is changed. Layer 1 by blowing agent
2 expands and the light reflecting layer 13 and the protective layer 14 are locally lifted as described in FIG. 3, and the pit 15 is formed.

[0032]

In the present invention, since the light absorbing function and the foaming function are performed by the same layer 12, the light is efficiently converted into heat by the light absorbing agent during recording, and this is efficiently converted into the foaming agent. Since it is transmitted and foams, it is recorded with high sensitivity.

Further, since the light absorption layer 12 itself expands and expands to form the pits 15, the pits 15 are formed under the reflective film 13 at the portion where the pits 15 are formed, as in the conventional case described in FIG. The pits are formed with almost no occurrence, and the mechanical strength of the pits is increased. Therefore, it is possible to obtain a medium having high reliability and excellent storage stability.

Further, according to the present invention, the light reflecting layer 13 is locally lifted by the volume expansion of the light absorbing layer 12 itself to form the pit 15. Therefore, the pit 15 is formed.
The formation of the film can be surely lifted, and accordingly, the protective film 14 does not lower the sensitivity even if the protective film 14 has a thickness sufficient to protect the film.

Further, in the information recording medium according to the present invention, since the recording and reading light can be irradiated from the side of the substrate 11, even if dust or scratches are present on the protective film 14, it causes a signal defect. It is possible to record and read information with a high S / N without any trouble.

Further, according to the present invention, since the use of the low melting point metal as mentioned at the beginning can be avoided, it is possible to avoid the use of a material having toxicity, which causes problems in the manufacturing process and pollution. Etc. can be avoided, and the industrial profit becomes large.

[Brief description of drawings]

FIG. 1 is a schematic enlarged cross-sectional view of an example of an information recording medium according to the present invention.

FIG. 2 is a sectional view of an information recording medium according to the present invention in a state where information is recorded.

FIG. 3 is a schematic cross-sectional view of an example of a conventional information recording medium.

FIG. 4 is a sectional view of a conventional information recording medium in an information recording state.

[Explanation of symbols]

 11 Base 12 Light Absorbing Layer 13 Reflective Layer 14 Protective Film

Front page continued (72) Inventor Tadashi Kiyomiya 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Kenjiro Watanabe 6-35, Kitashinagawa, Shinagawa-ku, Tokyo Sony Stock In-house (56) Reference JP 57-55540 (JP, A) JP 56-127937 (JP, A) JP 56-145528 (JP, A) JP 56-37188 (JP, A) )

Claims (1)

(57) [Claims] 1. A heat containing a light-transmissive substrate, a light-absorbing agent provided on the light-transmissive substrate for absorbing recording light and converting it into heat energy, and a foaming agent for thermally decomposing to generate a gas. A light absorbing layer made of a plastic resin layer and a light reflecting layer formed adjacently on the light absorbing layer, and recording light irradiated through the light transmissive substrate is used as the light absorbing layer itself. The light absorbing effect enhanced by the light absorbing agent in (1) efficiently absorbs heat to generate heat, and foaming due to the heat causes deformation of the recording light irradiation portion of the light absorbing layer to cause information generation. An information recording medium characterized by recording.