JPH0449175B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention resides in an optical recording medium. In detail, by irradiating a laser beam to locally heat the
The present invention relates to an optical recording medium in which recording is performed by forming holes or recesses in the heating section.

[Conventional technology]

It has been known to use Te as an optical recording medium in which holes are formed by irradiating a thin film formed on a substrate with a laser beam. Since Te has a low melting point and low thermal conductivity, it exhibits high sensitivity in recording by the above method. However, Te has the problem that it is easily oxidized, and when it is oxidized, it becomes transparent and cannot be recorded.

As improvements to the above problems, there are alloys of Te, low oxides of Te, and those in which Te is dispersed in an organic thin film. (For example, JP-A-53-31104
(Japanese Patent Application Publication No. 58-54338, Japanese Patent Application Publication No. 57-98394).

[Problems to be Solved by the Invention] In particular, the present inventors deposited a Te-Se alloy recording medium by sputtering using Ar gas using a Te-Se alloy as a target, and investigated its characteristics. As a result, these media
It was discovered that crystal grains with diameters ranging from several thousand Å to 1 μm exist on the entire surface of the film, and this contributes to noise during signal reproduction, resulting in an increase in C/N ratio (carrier noise).
We confirmed the fact that this decreases the ratio.

[Means to solve problems]

Based on these results, the present inventors further conducted various studies and found that by sputtering a target by mixing selenium fluoride gas such as SeF ₆ into Ar gas, it was possible to obtain an amorphous structure. The inventors have discovered that since there are no crystal grains or grain boundaries, it is possible to obtain an optical recording medium that has good sensitivity and pit shape as well as excellent stability over time, and has completed the present invention.

On the other hand, in order to improve recording sensitivity and pit shape, it is also effective to provide an undercoat layer between the substrate and the recording medium. As the undercoat layer material, CS ₂ ,
Plasma polymerized films of various monomers such as carbon fluoride gas (JP-A-57-117139, JP-A-59-90246) Sputter films of polytetrafluoroethylene resin, etc. (JP-A-59-
90246, 58-50634), etc. The present inventors paid particular attention to fluorocarbon polymerized films or sputtered films, and as a result of intensive studies on improvements to the fluorocarbon thin films and combinations with recording media made of the above-mentioned Te and Se-containing spattered films,
Reactive sputtering is performed using an alloy containing Te or Se as a target material, particularly in a mixed gas of selenium fluoride gas and Ar gas, to sputter Te and Se on a substrate coated with a fluorocarbon thin film layer.
By forming a sputtered film containing Se, it has excellent stability over time and a high C/N ratio (Carrier to noise).
ratio), an optical recording medium with high sensitivity can be obtained.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of the specific structure of the optical recording medium of the present invention, in which 1 is a substrate;
Reference numeral 2 denotes a fluorocarbon plasma polymerized film or polyfluorocarbon patter film disposed on the substrate 1, and 3 a recording layer 4 containing Te and Se formed on the film 2 by reactive sputtering, which is a groove for track servo. In the example shown in FIG. 1, the substrate 1 is made of polymethyl methacrylate resin or polycarbonate resin in which guide grooves for track servos are provided by injection molding or the like.

When forming a fluorocarbon plasma polymerized film or a polyfluorocarbon sputtered film 2 on the substrate 1, the fluorocarbon may include perfluoroalkanes such as CF ₄ and C ₂ F ₆ ;
Perfluoroalkenes such as CF ₃ CFCF ₂ , perfluorohexane, perfluorobenzene, etc.
Even if the fluorocarbon is a gas or liquid at room temperature, its vapor pressure is sufficiently high that it is difficult to store the vapor in a vacuum container.
It is desirable that the material satisfies 10 _-3 Torr or more, enables glow discharge, and has a high degree of fluorine substitution.
A plasma polymerized film is formed by using these fluorinated carbons as monomers and using capacitive or inductive discharge. As the polyfluorocarbon, polytetrafluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin, etc. are used, and these are used as targets for inert gas such as Ar, or , a sputtered film is formed by sputtering with a mixed gas of an inert gas and the monomer.
The thickness of this plasma polymerized film or sputtered film is
The thickness is 20 to 1000 Å, preferably 50 to 200 Å.

Further, on the fluorocarbon undercoat layer 2, a recording layer 3 containing Te and Se is deposited to a thickness of about 50 Å to 1 μm, preferably about 200 to 1000 Å, by a reactive sputtering method. The target material used in this reactive sputtering method is Te, or Te as a base material, Se, Pb,
Examples include alloys containing Bi, Sb, Sn, Ge, As, etc. On the other hand, selenium fluoride gas to be mixed with Ar gas includes Se ₂ F ₂ , SeF ₄ , Sef _6, etc., but SeF ₆ is common, and the ratio of selenium fluoride gas in the mixed gas is 1. ~50% (volume ratio). Se content in the recording layer 3 consisting of a stacked film containing Te and Se (this Se
is derived from selenium gas fluoride and Te-Se
(including those derived from the alloy when an alloy is used) is selected in an atomic ratio of 5 to 25%. This is because if the Se content in the film is less than 5% in atomic ratio, the stability over time will deteriorate, and if it is more than 25%, the sensitivity and pit shape will deteriorate. When other third components are included, the amount thereof is usually suitably used in an atomic ratio of about 1 to 20% based on Te.

Since the optical recording medium of the present invention having the above structure contains Se derived from selenium gas fluoride, the recording layer has an amorphous structure and has excellent sensitivity and pit shape. In addition, as a function of Se, the stability of the recording layer over time is extremely good.
Even after 30 days of accelerated testing at 85% relative humidity.
There is also the effect that the opposition rate does not change at all.
Furthermore, by using an undercoat layer as described above,
In particular, pits with a uniform shape and well-defined rim are formed, thus achieving a high C/N ratio, and
A highly sensitive recording medium can be obtained.

FIG. 2 is an example of an apparatus for manufacturing an optical recording medium according to the present invention. 1 in the figure is a vacuum container,
2 is a polytetrafluoroethylene resin target, 3 is Te or an alloy target containing Te, 4 is a counter electrode on which a substrate 5 is arranged, 6 is a gas inlet, and 7
is the shutter, 8 is the exhaust port, 9 is the RF power supply, 10
is a toggle switch. The electrode 4 is movable, and is placed directly above the polytetrafluoroethylene resin target 2 and coated with an undercoat layer made of a sputtered film of fluorocarbon, and then moved directly above the target 3 without breaking the vacuum.
Formation of the recording layer can then be performed. Second
In the case of the apparatus shown in the figure, Ar gas is introduced from the gas inlet 6 to generate a high frequency glow discharge between the target 2 and the electrode 4, and a sputtered film of fluorocarbon is formed on the substrate 5. A mixed gas of Ar and selenium fluoride is introduced from the inlet to generate a high-frequency glow discharge between the alloy target 3 containing Te or Te and the electrode 4, and reactive sputtering is performed to form a deposited film containing Te and Se. Form a recording layer consisting of: The Se content in the recording layer can also be controlled by the Se content in the target when an alloy containing Te and Se is used as the target. The amount of Se mixed into the film from the gas phase due to decomposition can be controlled by the mixing ratio of selenium fluoride gas and Ar gas or by the discharge conditions (discharge power, total pressure, etc.). , it is possible to control the Se content over a wide range and continuously, and it is also possible to give a desired distribution to the composition in the depth direction in the recording layer thin film.

The present invention will be explained in more detail with reference to Examples below.

〔Example〕

After evacuating the vacuum container to 3×10 ^-6 Torr, Ar
Gas was introduced to 1×10 ^-2 Torr, a glow discharge was generated with a high frequency power of 100 W at 13.56 MHz, and a sputtered polytetrafluoroethylene film of about 15 nm was deposited on the polycarbonate resin substrate. After this, the substrate side electrode was moved directly above the alloy target of 88% Te and 12% Se, and after pre-sputtering, SeF ₆ gas was introduced at a volume ratio of about 10%, and the total pressure was increased to 5 × 10 ^-3
Torr. Again 13.56MHz high frequency power 50W
to produce a glow discharge, which causes the Te Se bulk film to ca.
45nm deposited. The Se content was 12% in terms of atomic mass ratio (atomic%).

Next, this optical recording medium is exposed to a wavelength of 830 nm.
When recording and reproducing with a GaAlAs semiconductor laser, a C/N ratio of 57 dB was obtained. The recording sensitivity is
The laser power on the recording medium was 4 mW and the beam diameter was 1.6 μm, and the time was 160 nsec.

[Example 2] Tetrafluoroethylene monomer and Ar
50 CCM and 15 CCM were respectively flowed through mass blow controllers calibrated to fill the vacuum vessel with a reactive gas of 5×10 ⁻³ Torr. A high frequency voltage of 13.56 MHz was applied to a high frequency electrode using capacitive coupling, and a discharge was performed for 5 minutes at a discharge power of 100 W to form a plasma polymerized film of about 100 Å. Thereafter, a TeSe deposited film of about 45 nm was deposited in the same manner as in Example 1.

Then, when recording and reproduction were performed on this optical recording medium in the same manner as in Example 1, the C/N ratio was
56dB was obtained. The recording sensitivity was 170nesc.

[Comparative example]

In a medium in which the TeSe deposited film was formed directly on a polycarbonate resin substrate without providing a fluorocarbon undercoat film, a C/N ratio of only 52 dB was obtained. Furthermore, the recording sensitivity was 200 nsec.

On the other hand, on an undercoat film made of a sputtered fluorocarbon film formed in the same manner as in Example 1,
When a TeSe deposited film was formed by sputtering only with Ar gas, a C/N ratio of only 45 dB was obtained. Furthermore, the recording sensitivity was 230 nsec.

〔Effect of the invention〕

By containing Se derived from selenium gas fluoride, the optical recording medium of the present invention can obtain a recording layer with a uniform amorphous structure in which no crystals or grain boundaries are present, and therefore the sensitivity can be improved. A recording medium with excellent pit shape can be obtained. Further, if an undercoat layer made of a plasma polymerized film of fluorocarbon or a sputtered film of polyfluorocarbon is provided, this effect will be further improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of an embodiment of the recording medium of the present invention. FIG. 2 shows an example of an optical recording medium apparatus according to the present invention. In the figure, 1 represents a substrate, 2 represents a fluorocarbon film, and 3 represents a recording layer.

Claims (1)

[Claims] 1 By reactive sputtering using Te or an alloy containing Te as a target material in a mixed gas of selenium fluoride gas and Ar gas,
An optical recording medium comprising a deposited film containing Te and Se formed on a substrate. 2. The optical system according to claim 1, characterized in that an undercoat layer consisting of a plasma polymerized film of fluorocarbon or a sputtered film of polyfluorocarbon is provided between the substrate and the deposited film containing Te and Se. Recording medium.