JPH024579A - Draw-type laser beam recording member - Google Patents

Abstract

PURPOSE:To provide the title member with excellent preservation stability and high sensitivity by providing a thin Se film with an average film thickness in a specified range on a recording medium, in a pit-forming DRAW-type laser beam recoding member using the recording medium which comprises at least Te and a plasma-polymerized product of an organic compound. CONSTITUTION:A thin Se film having an average film thickness of 1-100Angstrom is provided on a recording medium, in a pit-forming DRAW-type laser beam recording member using the recording medium which comprises at least Te and a plasma-polymerized product of an organic compound. Namely, a Te- containing layer susceptible to deterioration by oxidation is covered by a chemically stable Se layer, whereby chemical changes of the Te-containing layer is restrained. Further, thermal properties of Se prevent the Se layer from producing adverse effects on sensitivity of recording by formation of pits. Therefore, a pit-forming DRAW-type laser beam recording member having excellent preservation stability and high sensitivity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a protective layer for preventing the recording medium from deteriorating over time in a write-once type laser beam recording member of the small hole forming type.

[Prior art]

In recent years, laser beam recording materials such as optical disks are capable of high-density recording, random access, and are portable, features that conventional information recording materials such as floppy disks, fixed magnetic disks, and magnetic tapes do not have. It is attracting attention as a recording medium in the field of information recording for computers, videos, etc.

Due to its recording and playback characteristics, optical discs are read-only type,
They can be roughly classified into write-once type and erasable type. Among these, the write-once optical disc refers to one on which recording can be performed only - times. Although this type of optical disk cannot erase information once recorded, it is expected to be used in the field of recording information that needs to be stored for a long time or that is difficult to erase.

In write-once optical discs, small holes are formed by sublimation and melting of the recording medium in the area irradiated with the writing laser pulse, and information is read out based on the difference in light reflectance and transmittance between recorded and unrecorded areas. is well known. As recording media for small hole-forming optical discs, Aβ,
It is known that single thin films of metals, semimetals, and semiconductors such as Bi, Te, Pb, and Mo can be used, but Te has particularly excellent recording and reproducing characteristics.

Furthermore, in Japanese Patent Laid-Open No. 5-1973, it was shown that recording sensitivity was improved in recording media containing plasma polymers of Te and organic compounds.
It is described in Japanese Patent No. 7-98394. However, it is known that these recording media are prone to deterioration over time and have problems with information storage stability.

The following two main types of deterioration over time of a recording film in a small hole forming type medium can be mentioned.

■ Macroscopic chemical changes in the recording film that cause changes in the optical properties of the recording film, resulting in changes in recording characteristics and reproduction signal levels; ■ Microscopic changes in the recording film. Defects such as distortion racks occur, causing signal dropouts and unnecessary signals during playback.

The most common countermeasure for the chemical change (2) is to chemically stabilize the medium itself.

For example, Japanese Patent Publication No. 60-23997 proposes a method of adding Se to a recording medium containing Te.

The present inventors also proposed providing a plasma polymerized organic compound as a protective layer. (Special application 1986-314
No. 261).

[Problem to be solved by the invention]

However, when storage stability is improved using the above method, the sensitivity decreases compared to the original recording medium, and satisfactory recording characteristics cannot necessarily be obtained unless a higher power laser beam is applied. It turned out that.

An object of the present invention is to provide a write-once type laser beam recording member having excellent storage stability and high sensitivity.

[Means for Solving the Problems] That is, the present invention provides a small hole-forming write-once laser beam recording member using a recording medium containing at least a plasma polymerized product of Te and an organic compound, in which a film is formed on the recording medium. The present invention provides a write-once type laser beam recording member characterized in that a Se thin film having an average thickness of 1 to 100 layers is provided.

The present invention suppresses chemical changes in the Te-containing layer by covering the Te-containing layer, which is prone to oxidative deterioration, with a chemically more stable Se layer. This was done based on the knowledge that recording sensitivity is unlikely to be adversely affected, but surprisingly, storage stability was achieved even when the thickness of the Se layer was on average less than one layer and less than a monolayer of Se. It turned out to be effective.

The present invention will be specifically explained below.

The recording medium used in the present invention contains at least Te and a plasma polymer of an organic compound.

Examples of plasma polymerized organic compounds used in the present invention include saturated hydrocarbons such as methane, ethane, propane, butane, and pentane, unsaturated hydrocarbons such as ethylene, propylene, butene, and pentene, and methanol, ethanol, and propatool. Examples include alcohols, ketones such as acetone and methyl ethyl ketone, and aromatic compounds such as benzene and toluene. In addition, sulfur-containing compounds such as carbon disulfide and mercaptan, tetrafluoroethylene,
Fluorine-containing compounds such as hexafluoropropylene and octafluorocyclobutane, methylamine, ethylamine, propylamine, dimethylamine, diethylamine,
1 to 1 organic compounds such as nitrogen-containing compounds such as pyridine
It can be obtained by polymerization using high frequency discharge or direct current discharge at a vacuum degree of about O-6 Torr.

By performing this plasma polymerization simultaneously with vacuum evaporation or sputtering of Te, a recording medium containing a plasma polymer of Te and an organic compound can be produced.

These recording medium layers are formed in the form of a thin film on a resin substrate such as a glass substrate, polycarbonate, or polymethyl methacrylate by a known method such as vacuum evaporation or the Spatzkling method.

The recording medium layer may be formed directly on the substrate, or may be formed on the substrate via an organic material layer such as a polymer formed in the form of a thin film.

As described above, by providing a thin film of Se on a recording medium prepared using the conventional technique, it is possible to obtain a small hole-forming write-once laser beam recording member that has excellent storage stability and high sensitivity, which is the object of the present invention. .

The Se thin film can be formed on the recording medium by a known method such as vacuum evaporation or spun sputtering.

Generally, as the thickness of the Se layer increases, storage stability improves, but recording sensitivity slightly decreases.

If the number of Se layers is less than one person on average, the effect of improving storage stability will be small, while if it exceeds 100 people, no further improvement in storage stability can be expected, and the recording sensitivity will decrease somewhat. For this reason, the Se film thickness is in the range of 1 to 100 layers on average, preferably 1 to 30 layers on average, and more preferably 3 to 20 layers on average.

Furthermore, in order to stabilize the recording/reproducing characteristics of recording media containing plasma polymerized Te and organic compounds, Te crystallization is often carried out by heating to 50 to 80°C. The heat treatment may be performed before or after forming the 5eff film.

〔Effect of the invention〕

According to the present invention, it is possible to provide a small hole-forming write-once laser beam recording member with excellent storage stability and high sensitivity.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 A polycarbonate substrate with a pregroup of 130 mm φ was set in a vacuum evaporation apparatus, C32 gas was introduced, and a plasma polymerized film was formed on the substrate using a high frequency coil. Further, while plasma polymerization was continued, Te was evaporated from a resistance heating boat to form a Te/C82 film.

The film thickness of this recording medium was about 250 people. Then, Se is evaporated from another boat to deposit about 1
A thin film of 0 Se was deposited. The laser recording member thus obtained (hereinafter abbreviated as a single disk) was taken out of the vacuum deposition apparatus and placed in an oven at a relative humidity of 40% or less to crystallize Te at 70"C for 1 hour. The recording and reproducing characteristics of the single disc were evaluated using an 830 nm laser beam and a laser power of 0.8 mW during reproduction.
Measurements were made by changing the laser power during recording. In addition,
The recording position is a radius of 40mm, a rotation speed of 180Orpm,
The laser light irradiation pulse was 50 ns at a frequency of 5 MHz. As a result, the carrier-to-noise ratio (C/N) was 50
The laser power that exceeded dB was 5.8 mW.

This disk veneer was placed in a constant temperature bath at 80° C. and 80% relative humidity for 20 days to conduct an accelerated storage stability test.

Thereafter, no difference was observed in the recording/reproducing characteristics of this single disk compared to before the accelerated test, and on the other hand, the reflectance of laser light remained at 97% of that before the accelerated test.

Comparative Example 1 A disk veneer was obtained in the same manner as in Example 1 except that a thin film of Se was not formed, and the upper layer contained a plasma polymerized product of Te and C32, and the lower layer was provided with a plasma polymerized film of C32.
Next, Te was crystallized. The recording/reproducing characteristics of this single disk were measured in the same manner as in Example 1, and an accelerated storage stability test was conducted.The laser power during recording exceeding 50 dB before the accelerated test was 5.8 mW. Further, after the accelerated test, the maximum C/N decreased by about 10 dB and the reflectance decreased to 60% of that before the accelerated test.

Examples 2 to 5 and Comparative Example 2 A plasma polymerized film with C82 and Te
A recording member having a two-layer structure having a plasma polymerized film of and CS z was prepared. However, since the plasma polymerization conditions were changed, the composition ratio of this recording member was slightly different from that of Example 1, and the film thickness was about 300. Five of the resulting single disks were simultaneously heat-treated at 70°C for 1 hour, then one was left as is and a Se thin film was applied on top of it to the thickness shown in Table 1 by vacuum evaporation. The recording/reproducing characteristics and changes in reflectance were observed before and after an accelerated storage stability test. As shown in Table 1, the laser recording member of the present invention had high sensitivity and excellent storage stability. .

Comparative Example 3 A polycarbonate substrate was set in a vacuum evaporation device, and T
Evaporate e and Se simultaneously from separate boats, Te and S
A single disc having a recording layer containing e.g. The volume ratio of T e / S e in the recording layer is 81/19.
Met. When the recording and reproducing characteristics of this single disk were measured, even when the laser power was increased to 7 mW, the C/N was 50 dB or less, and the sensitivity was extremely low.

Example 6 A polycarbonate substrate was set in a vacuum evaporation apparatus, and hexafluoropropylene (hereinafter abbreviated as 6FP) gas was introduced.
A 6FP plasma polymerized film was formed using a high frequency coil. Next, the introduced gas was C82, and Te was evaporated from a resistance heating boat while plasma polymerization was being carried out to form Te-C3.
Two films were created. The film thickness of this recording medium was about 250 people. After stopping the plasma polymerization and Te evaporation, Se was evaporated from another boat to form a Se thin film of about 10 people.

After crystallizing Te on the obtained disk single plate in the same manner as in Example 1, accelerated recording/reproducing characteristics and storage stability tests were conducted in the same manner as in Example 1. As a result, C/N≧50
The laser power during recording, which corresponds to dB, was 5.8 mW, and the reflectance after the accelerated test remained at 97% of the original.
It showed high sensitivity and excellent storage stability.

Example 7 A disk single plate having a three-layer structure of 6FP plasma polymerized film-Te/6FP plasma polymerized film-3e film was produced in the same manner as in Example 6 except that only 6FP was used as the introduced gas. Accelerated tests on recording/reproducing characteristics and storage stability were conducted in the same manner as in Example 1, and results similar to those in Example 6 were obtained, indicating that the sample had high sensitivity and excellent storage stability.

Example A film was formed in the same manner as in Example 7 except that the introduced gas was octafluorocyclobutane (hereinafter abbreviated as PCB).
Plasma polymerized film-Te -PCB plasma polymerized film-Se
A disk veneer having a three-layer structure of membranes was fabricated. Accelerated recording/reproducing characteristics and storage stability tests were conducted in the same manner as in Example 1, and the disk single plate was found to have high sensitivity and excellent storage stability.

Example 8 A grouped polycarbonate substrate was set in a sputtering apparatus having an RF power source and a DC power source, and as a target, Te was used for the RF power source and Se was used for the DC power source. After evacuating the system, Ar containing 30% of tetrafluoroethylene (hereinafter abbreviated as TFE) was introduced, and RF
The power was turned on and sputtering was performed to create a recording medium made of Te-TFE plasma polymer. Next, the introduction of TFE was stopped, Ar gas alone was introduced, and the power source was changed to a DC power source to perform sputtering of Se.

In this way, a Te-TFE plasma polymer layer of about 200
A disk veneer having a two-layer structure of approximately 10 layers of carbon and Se layers was obtained. Accelerated recording/reproducing characteristics and storage stability tests were performed in the same manner as in Example 1, and it was confirmed that this single disk had high sensitivity and excellent storage stability.

Claims (1)

[Claims] In a small hole-forming write-once laser beam recording member using a recording medium containing at least a plasma polymer of Te and an organic compound, the average film thickness on the recording medium is 1 Å or more.
A write-once laser beam recording member characterized by being provided with a 100 Å Se thin film.