JPH02301034A - Information recording medium - Google Patents

Abstract

PURPOSE:To carry out recording for a long time by providing a recording film of the material which is reversibly changed by the irradiation of an electromagnetic wave, and a protective film of a carbonaceous material on a substrate. CONSTITUTION:A recording film 3 of a material which is reversibly changed by the irradiation of an electromagnetic wave is provided on a substrate 1, and a protective film 2 of a carbonaceous material is furnished thereon to form the information recording medium. The polymer of a hydrocarbon densely cross-linked, i-carbon, graphite, diamond or their composite are used as the carbonaceous material constituting the protective film 2. The carbonaceous material consists essentially of C and can be added with H, N, O, etc., and the film is formed in 10-100nm or preferably 20-500nm thickness by sputtering, etc. Since the carbon-based thin film is used as the protective film 2 for the recording film 3, the protective film 2 is not crystallized or subjected to the chemical reaction with the recording film 3 even after recording and erasing are repeated, and hence recording can be carried out for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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.

[Conventional technology]

Crystals are used as information recording media that can record, reproduce, and erase information by irradiation with electromagnetic waves, especially laser beams.
Chalcogen-based thin films that utilize crystal or crystal-amorphous phase change are well known. 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 Ge-Te, Ge-Te-3b, and Ge-Te, which are disclosed in USP 3,530,441.
Te-8, Ge-3e-8, Ge-5'e-3b, Ge
-As-3e, In-Te, 5e-Te, 5e-As, etc. are known. In addition, for the purpose of improving stability and high-speed crystallization, Au (Japanese Patent Application Laid-open No. 61-2196
No. 92), Sn and Au (Japanese Patent Application Laid-open No. 61-270190
With the aim of proposing materials containing additives such as PB (Japanese Patent Application Laid-Open No. 1989-19490), and improving the repeatability of recording and erasing,
A material with a specified composition ratio of Ge-Te-8e-8b has also been proposed (Japanese Unexamined Patent Publication No. 73438/1983). However, it cannot be said that any of these 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 methods to solve the above problems is to disperse the phase change material in a translucent matrix to prevent irreversible changes such as enlargement of the crystal grain size of the phase change material, which is the cause of unerasable residue. Proposals for recording media have been made. As the matrix, oxides of silicon, aluminum, titanium, and magnesium are proposed in Japanese Patent Laid-Open No. 57-208648. Furthermore, in JP-A No. 63-173240, SiO□, SiO, Si, which have low thermal conductivity, are used as a matrix.
,N4,Tie, ,ZnS,ZnO1AI203,AI
Metal oxides, metal nitrides, metal sulfides, and metal carbides such as N, MgOlGem, SiC, ZrO2, Nb, and O are being considered.

In addition, examples of considering heat-resistant organic materials as a matrix are JP-A-60-124038 and JP-A-63-20.
No. 5832 and JP-A No. 63-206921. However, with matrices made of inorganic materials such as metal oxides, metal nitrides, metal sulfides, and metal carbides, crystal nuclei are generated and crystals grow due to repeated recording and erasing, which is also the cause of unerased areas and grain boundaries. This resulted in a reduction in C/N due to noise. In general, the recording film in an information recording medium is not able to absorb atmospheric moisture, oxygen, etc. by itself.
It is known to form a protective film above, below, or on top of the recording film because it is deteriorated by light or the like. Further, in phase change optical recording, a protective film is essential because the recording film is heated and melted. Materials used for the protective film include SiO2, Si3N4. ZnS,AIN
, 5iC1ZrO2 and other metal oxides, metal nitrides, metal sulfides, and metal carbides are being considered. Also, ZnS
A mixture of SiOx and SiOx (x=1 to 1.8) is
-276724. However, in the above-mentioned metal compound, crystal nuclei are generated and crystal growth occurs due to repeated recording and erasing, which also causes unerased data and lowers the C/N due to grain boundary noise. Also,
When Te-based chalcogen is used in the recording film, since the chalcogen is active, it causes a chemical reaction with the protective film material to produce a fully curved chalcogenide, resulting in a decrease in recording C/N and lifetime.

[Problem to be solved by the invention]

The purpose of the present invention is to solve all of the above-mentioned problems in the prior art, to have high recording sensitivity and erasure ratio, and therefore to be able to perform high-speed recording and erasing, and to provide C/A by repeating recording and erasing.
It is an object of the present invention to provide a rewritable information recording medium that allows long-life recording without N deterioration and does not require a complicated system.

[Structure of the invention]

The information recording medium of the present invention basically has a recording film made of a material that optically undergoes reversible change when irradiated with electromagnetic waves on a substrate, and a protective film made of a carbon-based material is further provided on the recording film. It is something.

In the information recording medium of the present invention, the carbon-based material constituting the protective film is a highly crosslinked hydrocarbon polymer, i-
Examples include carbon, graphite, diamond and composites thereof.

These carbonaceous materials mainly contain C and H as necessary.
, N, O, etc. can be contained.

The thermal decomposition temperature of the carbonaceous material is 600°C or higher, preferably 8°C.
The temperature is 00°C or higher, more preferably 1000°C or higher.

The carbonized thin film can be formed by sputtering, reactive sputtering, reactive vapor deposition, plasma CVD, photo-CVD, or a combination thereof. Although the film thickness is not particularly limited, it is usually in the range of 10 to 1000 nmfi, preferably 20 to 500 nm.

This carbon-based thin film is produced using a plasma CVD method, preferably using glow discharge, on a substrate set in a vacuum reactor in the presence of a carrier gas or a reaction gas if necessary, using a hydrocarbon compound as a starting material. The film is formed by CVD method.

The film forming conditions are gas pressure during reaction of 0.001 to several torr, preferably 0.002 to 2 torr; glow discharge power of 1
~3OOW, preferably 5~100W; discharge 1 hour 1
~180 minutes, preferably 2-120 minutes; substrate temperature 0-3
50℃.

Preferably it is 20-200°C.

Examples of starting materials include hydrocarbons such as methane, ethane and propane, alcohols such as methanol, ethanol and propatool, and aromatic compounds such as benzene, styrene and xylene. As the carrier gas, for example, an inert gas such as He, Ne, Ar, or Nz is used, and as the reaction gas, for example, H2,0□, C◯, CO2, etc. are used. The glow discharge device may be a direct current glow discharge device or a capacitively coupled or inductively coupled alternating current glow discharge device.

- Substances that undergo optical reversible changes when irradiated with magnetic waves (hereinafter referred to as optically reversible substances) are substances that can reversibly change two or more structures depending on the power or wavelength of the irradiated electromagnetic waves. The two or more structures have different optical properties such as reflectance, absorption, transmittance, and refractive index.

To give specific examples, any organic substance, inorganic substance, metal, or metalloid having the above-mentioned properties may be used, and usually chalcogens such as Te and Se and their alloys, Zn
- Substances that undergo martensitic transformation such as Ag and Cu-Al-Ni, substances that change crystal form such as phthalocyanine pigments, diphenyl tellurium, diphenyl selenium, dimethyl tellurium, dimethyl selenium, tellurium diisopropoxy diacetylacetonate, Plasma CV of organic chalcogen substances such as selenium diisopropoxy diacetylacetonate
D thin film is used.

There are no particular restrictions on the material of the substrate on which the recording film is formed, and various plastics (for example, polymethyl methacrylate,
(polycarbonate, etc.), glass, ceramic, metal, etc.

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 substrate may be arbitrary, such as a tape, a disk, a drum, or a belt, depending on the intended use.

Depending on the purpose, other layers (for example, an adhesive layer such as an ultraviolet curable resin; a protective plate such as polymethyl methacrylate or polycarbonate; a reflective layer such as An, Cr, or Au) may be disposed on the recording medium of the present invention. I can do it. Furthermore, a layered structure in which the recording film is sandwiched between carbon-based thin films is also possible. For example, FIG. 1 shows an example of use as an optical disc. In the figure, 1 is a substrate, 2 is a film of carbon-based material, 3 is a recording film, and 4 is a protection plate.

Various types of electromagnetic waves can be used for recording, reproducing, and erasing, such as laser light, electron beams, X-rays, ultraviolet rays, visible light, infrared rays, and microwaves. A laser beam is best.

〔Example〕

The present invention will be explained below by way of examples.

Example 1 In order to evaluate the recording/erasing characteristics of an information recording medium, an optical disk having a structure of substrate/protective film A/recording film/protective film B/adhesive layer/protective plate was prepared.

The thin film of carbon-based material of protective film A is formed by plasma CV in Fig. 2.
D The inside of the device is equipped with an oil diffusion pump 13 and an oil rotary pump 14.
After exhausting to lXl0''''' torr using
5SCCM (7) flow rate of methane gas from cylinder 5, H2
Gas was supplied from cylinder 6 at a flow rate of 11,005cc, and the inside of the reactor was set to IXIF2torr, then 50W.
Plasma was generated with a power of 1,100 nm thick and synthesized on the 85 mmφ pregrooved polycarbonate 1 set on the RF electrode 9.

For the recording film, after synthesizing the protective film A, the inside of the reactor is again heated to I×
Evacuate to 10-' torr and add diphenyltellurium to 6
The inside of 1 reactor was supplied with I
After setting the pressure to 10-" torr, plasma was generated with a power of 50 W, and the film was laminated to a thickness of 1100 nm on the protective film A. The recording film consisted of about 50 Te ultrafine particles dispersed in an ultra-high density cross-linked carbon film. It had a structure.

Protective film B was synthesized in the same manner as protective film A. The adhesive layer was formed by a coating method using an ultraviolet curing resin, and the protective layer was made of polycarbonate with a thickness of 0.5 mm.

As a result of thermal analysis using high-sensitivity DSC and TGA of a thin film (protective film) of carbon-based material synthesized on glass during optical disk production, no exothermic peak or weight loss, which could be considered to be thermal decomposition, was observed at ~600°C. Ta.

When the thus prepared optical disk was rotated at 90 rpm and irradiated with a power-modulated laser beam at a linear velocity of 6 m/see, recording and erasing was repeated, the result was 50 dB.
A C/N of 30 dB and an erasure ratio of 30 dB were obtained, and sufficient recording and erasing characteristics were obtained.

Example 2 An information recording medium was produced in the same manner as in Example 1 except that styrene was supplied at a flow rate of 55 CCM and H2 gas was supplied at a flow rate of 11005 cc to the raw materials when synthesizing the protective film. Similar to Example 1, good results were obtained with this product.

Example 3 An information recording medium was produced in the same manner as in Example 1 except that a 1100 nm thick Ag1nTe2 sputtered film was used as the recording film.

Similar to Example 1, good results were obtained with this product.

〔Effect of the invention〕

As explained above, according to the present invention, since a carbon-based thin film is used as the protective film of the recording film in the information recording medium,
Since crystallization of the protective film and chemical reaction with the recording film do not occur due to repeated recording and erasing, the lifetime of recording can be extended.

If the recording film is a thin film of a carbon-based material in which fine particles of a material that optically undergoes a reversible change upon irradiation with electromagnetic waves are dispersed, the protective film and the recording film are both made of carbon-based material. The adhesiveness of the recording film is good, there is no peeling due to heat, etc., and the life of the recording can be further extended.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a specific example of the information recording medium of the present invention, and FIG. 2 is an explanatory diagram of an apparatus for producing the information recording medium of the present invention. l...Substrate 2...Carbon-based material 3...
- Recording film, 4... Protective plate, 5... Methane gas cylinder 6... H2 gas cylinder (styrene container) 7... Diphenyltellurium container 8... Ar gas cylinder 9... RF electrode 10.・Counter electrode 11・
...RF power supply 12...Vacuum gauge 13...Oil diffusion pump 14...Oil rotary pump 15...Substrate temperature control unit Fig. 1 Fig. 2

Claims (1)

[Claims] 1. An information recording medium comprising, on a substrate, a recording film made of a material that undergoes optical reversible change upon irradiation with electromagnetic waves, and a protective film made of a carbon-based material.