JPH02137974A - Rewritable data recording medium - Google Patents

Abstract

PURPOSE:To obtain a rewritable data recording medium free from deterioration in characteristics by using a plasma-polymerized film of a pigment as a carbon film. CONSTITUTION:In a carbon film containing a substance which optically reversibly changes by an electromagnetic wave irradiation, the carbon film is a plasma- polymerized film of a pigment. The polymerized pigment film can be formed by any of film-forming methods including a plasma process, such as a reactive sputtering, a plasma-reactive vapor deposition, and a plasma CVD. The film thickness is particularly limited, but is preferably in the range of 10 to 1000nm. It is preferable that the substance which optically reversibly changes by an electromagnetic wave irradiation into the film is contained in the range of 5 to 95wt.%. If the substance which optically reversibly changes by an electromagnetic wave irradiation into the film is in fine particle form, the size of the fine particle is preferably 100nm or less. As a starting material for the plasma polymerized film, all pigments superior in heat resistance can be used, but a phthalocyanine or quinacridone pigment is suitable for a plasma polymerization because of its sublimating properties.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a rewritable information recording medium that can be used as an optical recording element, an optical disk, a document image file, an optical card, and the like. [Prior Art] Chalcogen-based thin films that utilize crystal-crystalline or crystal-amorphous phase changes are well known as information recording media that can record, reproduce, and erase information by irradiation with electromagnetic waves, especially laser beams. ing. Phase-change recording media can be overridden with a single beam, which is difficult to do with magneto-optical recording media, and the optical system on the drive side is simple, so research and development into them has recently become active. Typical materials include G e-T eSG e -Te-5b, G
e-Te-5,Ge-3e-3゜Ge-3e-8b,G
e-As-3e, In-Te, 5e-Te, 5e-As
etc. are known. In addition, for the purpose of improving stability, high-speed crystallization, etc., Au (Japanese Patent Laid-Open No. 81-219
892) Sn and Au (Japanese Patent Application Laid-Open No. 81-270190)
, Pb (Japanese Unexamined Patent Publication No. 1982-19490), etc., with the aim of improving the repeatability of recording and erasing.
A material with a specified composition ratio of e-Te-5e-Sb (Japanese Unexamined Patent Publication No. 62-73438) has also been proposed. However, it cannot be said that any of them can satisfy all of the characteristics required of a phase change type rewritable information recording medium. In particular, the most important issues to be solved are improving recording sensitivity and erasing sensitivity, preventing a decrease in erasing ratio due to unerased data during override, and extending the lifespan of recorded and unrecorded areas. One of the ways to solve the above problems is to propose an information recording medium in which the phase change material is dispersed in a transparent matrix to prevent the crystal grain size of the phase change material from becoming large, which is the cause of unerasable residue. being done. As a matrix, SiO2, Sin, 5isNn, TiO2, ZnS with low thermal conductivity are used.
, ZnO, Al2O3, AlNSMgO. Metal oxides, metal nitrides, metal sulfides, and metal carbides such as Ge01SiC, ZrO2, and Nb2O5 are being considered. However, these matrices tend to generate crystal nuclei and grow crystals due to repeated recording and erasing, resulting in unerased data and a decrease in C/N due to grain boundary noise. Attempts have also been made to use plasma polymerized membranes as a matrix. However, in general, plasma polymerized films tend to contain components that thermally decompose and vaporize at temperatures below 301)'C, and although they can be used as write-once recording media, they are not suitable as rewritable recording media.

[Problem to be solved by the invention]

Therefore, the present invention aims to provide a rewritable information recording medium with high recording sensitivity, high erasing ratio, high speed erasing, long life recording, and no characteristic deterioration due to repeated recording and erasing. [Means for Solving the Problems] As a result of repeated research to solve the above problems, the present invention provides a recording medium using a plasma polymerized film of a pigment containing a substance that optically undergoes a reversible change when irradiated with electromagnetic waves. We have discovered that it is effective to use this method, leading to the present invention. That is, the present invention provides a carbon-based thin film containing a substance that optically undergoes a reversible change upon irradiation with electromagnetic waves.
This is a rewritable information recording medium in which the carbon-based thin film is a plasma-polymerized film of pigment. Pigments are substances that inherently have excellent heat resistance and light resistance. The inventors have discovered that a plasma polymerized film, which is a crosslinked product of the same, has excellent heat resistance and light resistance, and that by using it as a matrix in a recording medium, it is possible to improve recording sensitivity, recording life, and erasing ratio. Formation of the pigment polymer film in the present invention can be performed by any of reactive sputtering, plasma reactive vapor deposition, and plasma CVD as long as it is a film forming method that involves a plasma process. Although the film thickness is not particularly limited, it is preferably in the range of 10 nm to 0 Orv, preferably 20 nm to 500 rv. The weight percent of the substance that undergoes an optically reversible change upon irradiation with electromagnetic waves in the film is 5 to 95%.
%, preferably in the range of 20 to 80%. If the substance that undergoes an optically reversible change due to electromagnetic wave irradiation in the film is a fine particle, its size is 100n.
It is desirable that the thickness be in the range of a+ or less, preferably 30 nm or less. As the starting material for the plasma polymerized film constituting the information recording medium of the present invention, any pigment with excellent heat resistance can be used. Among them, phthalocyanine or quinacridone pigments are suitable because they have sublimation properties. Suitable for plasma polymerization. The substance that optically undergoes a reversible change upon irradiation with electromagnetic waves used in the recording medium of the present invention may be any substance including organic substances, metals, semimetals, and inorganic substances, including Te,
, Se and its alloy compounds are preferred. There are no particular restrictions on the material of the substrate in the present invention, and it may be made of various plastics (eg, polymethyl methacrylate, polycarbonate, etc.), glass, ceramic, metal, or the like. Further, a preformat for address signals and a pregroove for a guide groove may be formed on the surface of the substrate. The shape of the board depends on the use and purpose, such as tape,
It may be anything such as a disk, drum, or belt. The information recording medium of the present invention basically consists of a substrate and a recording film of the above plasma polymerized film, and as shown in FIG.
Other layers may also be present depending on the purpose. That is, in FIG. 1, l is the substrate, 2 is the protective layer (Si02, Si
3N4, etc.), 3 is a recording film, 4 is a protective layer, and 5 is a protective plate. Further, a reflective layer can be provided if necessary. Various types of electromagnetic waves can be used to irradiate the information recording medium of the present invention, including electron beams, X-rays, ultraviolet rays, visible light, infrared rays, and microwaves. is optimal. Next, a method for manufacturing the information recording medium of the present invention will be specifically explained. The optimal method according to the present invention is to simultaneously form a film by plasma CVD on a substrate set in a vacuum reactor, in which a metal, an alloy, an organometallic compound or an organometallic complex containing at least chalcogen as one of the starting materials, and a pigment. This is the way to do it. Among these, the plasma CVD method using glow discharge is more preferable. Among the starting materials, examples of substances containing chalcogen include metallic tellurium, metallic selenium, and Ge-Te.
5Ge-Te-9bsGe-Te-3,% Ge-3e
-3, Ge-9e-3bs Ge-As-8e S
In-Te, 5eTeSSe-As, diisopropoxy diacetylacetone tellurium, tetraethoxy tellurium, tetrapropoxy tellurium, dimethyl tellurium, diethyl tellurium, diphenyl tellurium, diisopropoxy diacetylacetone selenium, tetraethoxy selenium, tetrapropoxy selenium, dimethyl selenium, Examples include diethylselenium and diphenylselenium. As the pigment, metal-free and metal phthalocyanine, derivatives thereof, or quinacridone pigments are used. The method of vaporizing the starting material is as follows:
A mixture of a chalcogen-containing substance and a pigment may be heated with a single heater, or a chalcogen-containing substance and a pigment may be heated with separate heaters. Typical synthesis conditions include carrier gases such as N2, Ne, Ar, N2, etc., and reaction gases such as 02,
COSC02, CH4, C2H4, etc. are used. The glow discharge device may be a direct current glow discharge device or a capacitively or inductively coupled alternating current glow discharge device. The reaction gas pressure is from 0.001 to several Torr, preferably 0.00 Torr.
002 to 2 Torr. The electric power is 1 to 300 W, preferably 5 to 100 W, and the discharge time is 1 to 180 minutes, preferably 2 to 120 minutes. The substrate temperature is 0 to 350°C, preferably 20 to 200°C. [Examples] Next, the present invention will be explained by specific examples. Example 1 A recording film was produced using a plasma CVD apparatus shown in FIG. In Figure 2, 6 is an RF power source, 7 is a thermocouple, 8 is an electrode, 9 is a substrate, 10 is a starting material, 11 is a heater 1
2 is a counter electrode, 13 is a vacuum gauge, 14 is a diffusion pump, 1
5 is an oil rotary pump, and 1B is a heater control unit. As the substrate 9, a glass slide, a silicon wafer,
Either polyethylene terephthalate or polycarbonate is used, and the substrate temperature is 25°C. As starting material 10, diisopropoxy diacetylacetone tellurium
Using 1001 mg, copper phthalocyanine 30a+g, high frequency cuff 0W113.56 Mz, discharge time 10
min, pressure during reaction i,. X 1O-2Torr reaction susceptor. The obtained film had a reaction rate of 20% at a wavelength of 830 nm.
The absorption rate was 50% and the film thickness was 110r+a+. FTI
R. The UV-VIS spectrum revealed that this film contained a phthalocyanine structure. Although copper phthalocyanine sublimes at 420 to 430°C under atmospheric pressure, no change in the FTIR and UV-VIS spectra of the plasma-polymerized film was observed even when heated at 500°C under a reduced pressure of 10'Torr. It can be seen that the copper phthalocyanine is crosslinked and thermally stabilized. Furthermore, X-ray diffraction of the obtained film did not show patterns of copper phthalocyanine and tellurium, indicating that it was amorphous. Next, the optical recording/erasing properties of the film synthesized as described above were evaluated. The layer structure of the disk is substrate/S i 3 N
4 (t00n+g) /Recording film/SizN4 (100
rv)/adhesive layer/protective plate. Pre-grooved polycarbonate was used for the substrate. Si3N4 was produced by sputtering. 1 disc
While rotating at 800 rpm+, a power-modulated laser beam (830 nm) was irradiated at a linear velocity of am/sec, and recording/erasing was repeated, resulting in a C/N of 52 dB.
An erasure ratio of -30 dB was obtained, and sufficient recording/erasing characteristics were obtained. Example 2 A membrane was synthesized in the same manner as in Example 1, except that metal-free phthalocyanine was used instead of copper phthalocyanine as the starting material. This film was found to have the same effect as the film obtained in Example 1. Example 3 Starting material (diisopropoxydiacetylacetonate)
It was carried out in the same manner as in Example 1 except that It was 100 mg, 2.3 quinacridone was 3 hg, and the high frequency power was 50 W and 13.58 Mz. The obtained film had a reflectance of 25%, an absorption rate of 55%, and a film thickness of 100 rv at a wavelength of 830 rvl. FTIR. The UV-VIS spectrum revealed that this film contained a quinacridone structure. Although quinacridone melts at about 400°C under atmospheric pressure, no change in the FTIR and UV-VIS spectra was observed even when the plasma-polymerized film was heated at 600°C under a reduced pressure of 10'Torr. It can be seen that it is crosslinked and further stabilized thermally. In addition, no pattern of quinacridone and tellurium was obtained from X-ray diffraction of the obtained film, indicating that it was amorphous. Next, the optical recording/erasing characteristics of the film synthesized as described above were evaluated in the same manner as in Example 1, and the C/N was 48 dB.
An erasure ratio of 0 dB was obtained, and sufficient recording/erasing characteristics were obtained. Example 4 A membrane was synthesized in the same manner as in Example 3 except that metallic tellurium was used instead of diisopropoxydiacetylacetone tellurium as the starting material. This film was found to have the same effect as the film obtained in Example 3. [Effects of the Invention] In the information recording medium of the present invention, the matrix of a substance that undergoes an optically reversible change upon irradiation with electromagnetic waves is a plasma polymerized film of pigment, which is a non-volatile amorphous film that is highly cross-linked. Therefore, crystallization does not occur even when recording/erasing is repeated. Therefore, even if recording/erasing is repeated, C/
There is no decrease in N and erasure ratio. Furthermore, since the matrix of material that undergoes optically reversible changes upon irradiation with electromagnetic waves has low thermal conductivity, recording sensitivity is improved. In addition, the plasma polymerized film of the pigment contained in the recording medium is
The recording film alone has sufficient mechanical strength, heat resistance, weather resistance, and corrosion resistance to provide three-dimensional protection for materials that undergo optical reversible changes when irradiated with electromagnetic waves, extending the lifespan of records. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an example of a disk using the rewritable information recording medium of the present invention, and FIG. 2 is a schematic diagram showing a plasma CVD apparatus. l... Substrate, 2... Protective layer, 3... Recording film, 4...
・・Protective layer, 5・Protection plate, 8・RF power source, 7・
...Thermocouple, 8...Electrode, 9...Substrate, IO...
Starting material, 11... Heater, 12... Counter electrode,
13... Vacuum gauge, 14... Oil diffusion pump, 15...
・Oil rotary pump, 1B...Heater control unit.

Claims (3)

[Claims] (1) A rewritable information recording medium characterized in that the carbon-based thin film contains a substance that optically undergoes a reversible change upon irradiation with electromagnetic waves, and the carbon-based thin film is a plasma polymerized film of pigment. (2) The rewritable information recording medium according to claim (1), wherein the pigment is phthalocyanine. (3) The rewritable information recording medium according to claim (1), wherein the pigment is a quinacridone pigment.