JPS63161549A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve recording and erasing characteristics, contrast characteristic and moistureproofness by forming a recording layer contg. Te and Ge or In on a substrate and forming an inorg. underlying layer to 2,000-5,000Angstrom film thickness between the substrate and the recording layer. CONSTITUTION:This recording medium has the recording layer contg. Te and Ge or In on the substrate and has the inorg. underlying layer having 2,000-5,000Angstrom film thickness between the substrate and the recording layer. The underlying layer contains >=1 kinds among TeO2, V2O3, TiO2, SiO2, SiO, B2O3, Sb2O2, Bi2O2, PbO, Ta2O5, Si3N4, TiN, BiF3, LiF, PbF2, MgF2, and ZnS or is glassy. Since the heat insulating effect of the underlying layer is selectively increased at 2,000-5,000Angstrom thickness, the recording and erasing characteristics are improved, the large contrast is taken and the moistureproofness is improved.

Description

Detailed Description of the Invention (1) Background Technical Field of the Invention The present invention relates to an information recording medium, particularly a heat mode information recording medium and a recording and erasing method.

Prior art heat mode information recording media have the characteristic that the recording medium does not deteriorate due to wear and tear because there is no contact between the medium and the writing or firing head.For this reason, research and development of various heat mode recording media has been conducted. It is being done.

This heat mode information recording medium can be roughly divided into pit formation type and so-called phase change type.

The phase transition type records information by causing an amorphous-crystalline phase transition in the recording layer of the irradiated area using recording light such as a laser, and detects changes in reflectance with readout light. It is used for reading data. In addition, since erasing is performed better than the bit-forming type, recording and
It is possible to perform stable playback over and over again, and directly onto the recording layer without using a so-called air sandwich structure.
There is an advantage that a protective layer etc. can be provided.

Recording media that utilize such phase transition include Te,
Most of the recording layers are made of chalcogen-based materials containing Se or the like.

However, in an information recording medium having such a chalcogen-based recording layer, if the recording layer is stored in contact with the atmosphere, it will be corroded or oxidized by oxygen and water in the atmosphere, and the recording of information, Playback becomes impossible. Furthermore, when a resin substrate, which is advantageous in practice, is used, the recording layer is oxidized by moisture and oxygen that have passed through the substrate.

Therefore, in general, many researches have been made on devices having a structure in which a protective layer is provided on the surface of the recording layer or the interface of the substrate.

Conventionally, such moisture-proof protective layers include, for example, -
Attempts to provide inorganic vacuum-deposited films or resin films of silicon oxide, silicon dioxide, A1, Ti, etc. (Japanese Unexamined Patent Publication No. 57-555
No. 45, No. 56-130394, No. 56-156
940, Publication No. 56-155940, etc.).

Moisture proofing properties can be improved by increasing the thickness of these protective layers. However, in this case, there is a disadvantage that the sensitivity deteriorates.

For this reason, conventionally, the thickness of the protective layer is approximately 1000λ.

By the way, in an information recording medium having such a chalcogen-based recording layer, during recording, the recording layer is heated to about 400° C. or higher by laser irradiation. However, resin substrates such as acrylic, polycarbonate, etc.
It is thermally deformed at 0 to 130°C.

Therefore, it has been found that the deformation of the substrate remains when erasing is performed after recording, which causes unerased areas.

Therefore, in such an information recording medium, a heat insulating layer is required between the substrate and the recording layer. It is convenient for the heat insulating layer to also serve as a protective layer due to the structure of the medium.

However, with a film thickness of around 1000λ as described above, the heat insulation effect is insufficient, and the substrate is thermally deformed during recording.
There are disadvantages in that erasing cannot be performed well, leaving unerased areas, and contrast is low.

(2) Purpose of the Invention An object of the present invention is to provide an information recording medium that has good recording and erasing characteristics, a high contrast, and is also excellent in moisture resistance.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the present invention provides Te, Ge, or I on a substrate.
An information recording medium having a recording layer containing n, characterized in that it has an inorganic underlayer with a thickness of 2,000 to 5,000 layers between the substrate and the recording layer.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The information recording medium of the present invention is formed by providing a recording layer on a substrate.

Alternatively, it may be constructed by using two such devices and integrating them with their recording layers facing each other.

Here, the base is a flat plate made of resin.

As for the base made of resin, the base itself may be made of resin, or it may have a resin film on its surface.
Therefore, the present invention is also effective when tracking groups are formed on a substrate such as glass by the so-called 22 method, and in the present invention, this case is also included in the resin substrate.

This allows writing and reading from the back side of the substrate.

Suitable resin materials for the substrate include polycarbonate resin, acrylic resin, epoxy resin, and olefin resin such as polymethylpentene.

In particular, the polycarbonate resin may be any of aliphatic polycarbonate, aromatic-aliphatic polycarbonate, and aromatic polycarbonate, but aromatic polycarbonate resin is particularly preferred. Among these, polycarbonate resins made from bisphenol are preferred in terms of melting point, crystallinity, handling, etc. Among them, bisphenol A type polycarbonate resin is most preferably used.

In addition, the number average molecular weight of the polycarbonate resin is 10,
It is preferable that it is about 000 to 15,000.

Further, it is preferable that tracking grooves are formed on the surface of the base where the recording layer is formed.

The grooves may be formed directly or by a so-called zP method.

The depth of the groove is about λ/8n, especially λ/7n~λ
/ 12 n (where n is the refractive index of the substrate). Further, the groove 11 is approximately the width of a track.

In general, it is preferable to use the recording layer located in the recessed portion of the groove as a recording track portion, and to irradiate the writing light and the reading light from the back side of the substrate.

With this configuration, the writing sensitivity and the reading S/N ratio are improved, and the tracking control signal is also increased.

An inorganic underlayer is formed on such a substrate. This inorganic underlayer consists of TeO2, V2O3, TiO2, 5i
n2,5iO1B203, Sb203, Biz 0
3, PbO1Ta205, Si3N4, TiN, Bi
F3, LiF, PbF2. 1 of MgF2 and ZnS
Contains more than seeds or each persimmon glass such as borosilicate glass.

The thickness of such an inorganic base layer is preferably 2000 to 5000, particularly 2000 to 3000.

If the film thickness is less than 2,000, thermal deformation of the substrate occurs during recording, the amount of unerased material increases, and erasability becomes insufficient.

Furthermore, substrate deformation causes noise and causes deterioration of the C/N ratio.

If the film thickness exceeds 5,000, the sensitivity decreases and the increase in internal stress causes deterioration of the substrate, such as warping and warping.

Such an inorganic base layer is formed by various vapor phase film forming methods such as vapor deposition, sputtering, and ion blating.

A recording layer is provided on such an inorganic underlayer.

The recording layer contains Te and Ge or In, and has Te/(Te+Ge) and In/(T
The atomic ratio of e + I n ) is 0.7 to 0, respectively.
．． 98.0.004 to 0.25.

By using such a composition and composition ratio of the recording layer, good sensitivity and C/N ratio can be obtained due to the effect of the underlayer of the present invention.

In addition, depending on the case, the recording layer may be sb, Bi, As%
Se, S, Ta, Si, O, etc. may be contained in an amount of 2 at% or less.

Such a recording layer may be formed by a vapor phase film forming method in the same manner as in the case of forming the inorganic underlayer.

The thickness of the recording layer is about 0.005 to 1 tone.

Furthermore, if necessary, a thin film made of the same material as the underlayer described above may be formed on the recording layer to serve as a protective layer.

This makes it possible to prevent deterioration of the recording layer and further improve the thermal efficiency for recording.

The thickness of such a protective layer formed on the opposite side of the recording layer to the substrate is approximately 0.01 to 1-1, and the layer may be formed by the above-mentioned seven-phase vapor deposition method.

Furthermore, various protective coats may be provided on the outer surface of the medium, such as on the other surface of the substrate.

As a protective coat, attempts have been made to provide, for example, inorganic vacuum-deposited films or resin films such as -silicon oxide, silicon dioxide, A1, Ti, etc.
No. 30394, No. 56-156940, No. 56-
155940, etc.).

To record on an information recording medium having such a recording layer on a substrate, light or thermal energy is applied.

Generally, a semiconductor laser or the like may be used as the recording light.

Irradiation of recording light usually causes amorphous -
Recording is performed by causing a crystalline phase transition. That is, recording is normally performed using a phase transition from crystalline to amorphous.

When erasing, it is sufficient to use the above-mentioned erasing light and utilize phase transition, which is the reverse process to that for recording.

In the present invention, when the phase transition from crystalline to amorphous is used for recording and the reverse process is used for erasing, the recording pulse is about 100 to 100 Onsec (recording light output 4 to 1
0mw), erasing pulse is 0.5-;10μsec (
When the erasing light output is 1 to 4 mw), the contrast is high,
Recording and erasing can be repeated extremely stably.

To read after recording, use a reading light, etc.
Detection may be performed using changes in the reflectance of the recording layer.

■Specific effects of the invention The information recording medium of the invention has a recording layer containing Te and Ge or In, and has a film thickness of 200 mm between the substrate and the recording layer.
It is composed of an inorganic underlayer of 0 to 5000 people.

Therefore, such a medium has a high heat insulating effect of the underlayer, very good recording and erasing characteristics, high contrast, and excellent moisture resistance.

(2) Specific Examples of the Invention Hereinafter, the present invention will be explained in more detail by giving specific examples of the invention.

[Example 1] 5iQ2v underlayers having various thicknesses as shown in Table 1 below were provided on a polycarbonate substrate by sputtering.

On top of this, Te-Ge (Te95.5, Ge4.5)
A recording layer consisting of the following was deposited by sputtering to a thickness of 1000 nm.

Note that the composition of the recording layer was measured by ICP.

Furthermore, a 5 in 2 thin film was deposited on this by sputtering so as to cover 1000 people.

Furthermore, from above, the following UV
A cured resin layer was formed to a thickness of about 7 mm.

(UV curable resin composition) Multifunctional oligoester acrylate (Aronix M-8030) 100 parts by weight Photosensitizer (Bicure 55) 5 parts by weight After forming a layer of such a composition, crosslinking and curing was performed by irradiating 8017 cm ultraviolet rays for 15 seconds. I let it happen.

(1) Using each sample annealed at 120°C for 10 minutes as a recording medium, the disk was rotated at a speed of 2 m/sec, and a semiconductor laser (wavelength 830 nm) focused to approximately 1- was displayed from the substrate side. 3-10m as shown in 1
Recording was performed with irradiation at W, 1 Hz.

This signal is converted into 0.5 ml of continuous laser light (wavelength 830
n+n) to obtain a reproduced signal S.

(2) In (1), the recorded samples are 120
After erasing was performed by annealing at 100° C. for 10 minutes, the residual signal after erasing was measured to obtain S2.

The results are shown in Table 1.

In Table 1, S l−S 2 (d B )
is the difference between Sl and S2 measured above, and is 3 to 10
mW is the output at the time of recording.

The atomic ratio of the Te-In recording layer of sample No. 109 was Te92 and In8.

In Table 1, S of 25 dB or more as a practical adaptation level,
-S2 is underlined.

In addition, SI and S2 for sample No. 105
The measured C/N ratio values are shown in Figure 1.

Moreover, the difference between S and -S2 in FIG. 1 is not shown in FIG.

From the results shown in Table 1 above, the medium of the present invention has an S and -S2 value of 25 dB or more with respect to the optimum recording output, and it is clear that the medium of the present invention has an excellent effect of improving contrast erasing characteristics due to the improved heat insulation effect of the present invention. be.

More specifically, due to the effect of the base layer thickness of 2,000 to 5,000 people of the present invention, at a normal recording power of 4 to 10 mW,
Practically satisfactory S and -S2 of 25 dB or more were obtained.

On the other hand, it can be seen that S and -S2 of 25 dB or more cannot be obtained when the underlying layer thickness is less than 2,000 or more than 5,000.

This is due to the fact that at a thickness of 2,000 to 5,000 mm, the insulation effect of the underlayer is selectively increased, the amount of unerased material is reduced, and the underlayer also has the effect of improving recording sensitivity. is obtained.

Note that such effects were similarly achieved with the other inorganic underlayers listed above.

[Brief explanation of the drawing]

FIG. 1 shows the C/N ratio Sl during recording and the C/N ratio S after annealing and erasure in sample No. 105 of the present invention.
2 is a graph in which each of 2 is plotted against the recording output (mif). FIG. 2 is a graph showing the difference between Sl and S2 in FIG. 1, that is, the S, -S2 value. Applicant TDC Co., Ltd. Agent
Person Patent Attorney Yo Ishii -ffl'7T
"FIG, I S+: fi: Feng time C/N g0 power (mW) FIG, 2 word self f pre power (mW)

Claims (3)

[Claims] (1) An information recording medium having a recording layer containing Te and Ge or In on a substrate, characterized by having an inorganic underlayer with a thickness of 2000 to 5000 Å between the substrate and the recording layer. recoding media. (2) The base layer is TeO_2, V_2O_3, TiO_
2, SiO_2, SiO, B_2O_3, Sb_2O_
3, Bi_2O_3, PbO, Ta_2O_5, Si_
3N_4, TiN, BiF_3, LiF, PbF_2,
The information recording medium according to claim 1, which contains one or more of MgF_2 and ZnS, or is vitreous. (3) The information recording medium according to claim 1 or 2, wherein the substrate is made of resin.