JPS63160027A - Optical recording medium - Google Patents

Abstract

PURPOSE:To execute stable annealing at a low temp. in a short period and to obtain stabilized crystal structure by executing reactive sputtering in a gaseous mixture composed of gaseous fluoride and gaseous Ar by using a Te ofr Te-contg. alloy target material to obtain a deposited film contg. Te and F and annealing said film at a prescribed temp., thereby forming a recording layer. CONSTITUTION:The inside of a vacuum vessel 1 for manufacturing optical recording media is evacuated to a prescribed atm. and the gaseous Ar is introduced from a gas introducing port 5 into the vessel 1 to maintain a prescribed internal pressure therein. A high-frequency valtage is in succession impressed between electrodes 2 to generate electric discharge and to cleans the surface of the target 3 consisting of Te or the metal contg. Fe. The inside of the vessel 1 is thereafter evacuated again to the prescribed pressure and the gaseous mixture composed of the various gaseous fluorides and gaseous Ar is introduced at a prescribed ratio into the vessel. Reactive sputtering is executed in the gaseous mixture and the deposited film contg. Te and F obtd. in such a manner is annealed at 60-130 deg.C. Then heat treatment temp. is kept at 60-100 deg.C so that the recording layer after the treatment has the polycrystal structure having <1,000Angstrom crystal grain size.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium. Specifically, it is heated locally by irradiating it with a laser beam.

The present invention relates to an optical recording medium in which recording is performed by forming holes, depressions, or projections in the heating section.

(Prior art and its problems) Te is conventionally used as an optical recording medium in which a thin film formed on a substrate is irradiated with a laser beam to form all holes, depressions, or projections. It has been known. Since Te has a large optical absorption coefficient, low melting point, and low thermal conductivity, it exhibits high sensitivity in recording by the above method.

However, Te is easily oxidized, and when it is oxidized, there is a problem that the light absorption efficiency deteriorates and the recording sensitivity deteriorates.

As an improvement on the above problem, in addition to Te, B@f
There are alloyed materials containing Te, low oxides of Te, and materials in which T@ is dispersed in an organic polymer film (for example, JP-A-Sho!).
r3-3itoi1, JP-A-5G-5-K33G, JP-A-Sho3-9G39'1).

The above-mentioned recording medium is often produced by a vacuum evaporation method or an ion plate method.

The present inventors used Ar as a sputtering gas.

kTe using Te or a metal containing Te as a target material
As a result of a study of these recording media, it was found that crystal grains of several thousand to several micrometers in size are likely to occur in these media over the entire surface of the film on the substrate. This was confirmed by microscopic images, and it was found that this resulted in poor film smoothness, poor bit shape, poor recording sensitivity, and high noise during signal reproduction using laser light. Furthermore, the crystal structure of the deposited film having crystal grains is unstable, and therefore the reflectance is low.

In accelerated tests of temperature bsc and relative humidity trots,
Within a short time, the initial reflectance increased to nearly three times,
It was also obvious that the stability over time was extremely poor. In order to solve the above problems, the structure of the recording layer is made to be amorphous or microcrystalline.

There is a method of increasing the temperature at which these crystals transform into a polycrystalline structure with a large crystal grain size, that is, the crystallization temperature, in order to stabilize the crystal structure in the chamber. Specifically, as a recording layer, T
It is recommended to use an alloy thin film containing G@, Pb, Sm, etc. using E as a base material (Special Publications Sho!?-J!, 3!r).

Furthermore, the same effect may be obtained by dispersing Te in organic matter by reactive sputtering (% open 5 k 16S 9 k, JP 5 k tr 3 ql).
I).

However, even in these media, the reflectance (transmittance) changes over time due to changes in the crystal structure.

Deterioration occurs due to long-term reproduction light irradiation. As long as Te is used as a product, it is difficult to maintain a stable crystal structure over a long period of time using the above methods.

Rather, it is preferable to stabilize it by annealing.

However, the recording layer loses its initial uniform amorphous or microcrystalline structure due to annealing.

The crystals have been transferred to crystal grains with large grain size.

Another drawback is that the temperature required for sufficient heat treatment is too high, making it impossible to use plastic substrates.

(Means for Solving the Problems) The present inventors investigated various fc Te-based recording media formed by one-reactive sputtering method, and found that the crystal grain size is sufficiently small even after annealing, and the crystal grain size is low. In this invention, we have achieved a recording medium whose crystal structure can be sufficiently stabilized by short-time annealing.

That is, one aspect of the present invention is an optical recording medium comprising a recording layer provided on a substrate, in which the recording layer uses Te or a Te-containing alloy as a target material.

A deposited film containing Te and F obtained by reactive sputtering in a mixed gas of fluoride gas and Ar gas was
An optical recording medium characterized in that it is annealed at a temperature of 0° C. to i, yoc.

(Structure of the invention) The present invention will be explained in detail below.

First, the substrate of the recording medium according to the present invention.

Plastics such as acrylic resin and polycarbonate resin, metals such as aluminum, or glass.

Further examples include substrates coated with thermosetting or photocurable resins. especially.

Glasstic has the advantages of being inexpensive, easy to process, and having excellent optical properties.

In optical signal reproducing systems that are commonly used, in which laser light is incident through a substrate and reproduced by detecting the reflected light from the recording medium, the birefringence of the substrate affects the intensity of the reproduced light. Because it is a factor of fluctuation,
Changes in birefringence over time are undesirable.

In the present invention, the birefringence value of the plastic substrate can be stabilized by annealing. especially,
The birefringence in the direction perpendicular to the substrate surface after annealing is J Onm
If a plastic substrate as described below is used, noise due to fluctuations in the reproduced light due to birefringence can be reduced to a negligible level by the method of detecting the reproduced light through the substrate.

Although it is suitable for the recording medium of the present invention to use a plastic substrate, stabilization of the crystal structure of the recording medium by annealing is
It is also effective for other substrates.

In the present invention, a deposited film containing Te and F is formed on this substrate by a single-reactive sputtering method.

In the present invention, glow discharge is performed in a vacuum vessel into which a mixed gas of argon (Ar) gas and a reactive gas consisting of one or more of fluoride gases is introduced, using Te or an alloy containing Tef as a target material. T on the board
A deposited film containing e and Fi is formed. The discharge can be carried out by a conventional method such as a high frequency method or a direct current method.

The substrate temperature during sputtering is room temperature or sufficiently lower than the softening point of the substrate, for example 11Q in the case of polycarbonate.
-! It is maintained at about OC level. The thickness of the sputtering deposited film is desirably about 10Q to 1000X.

The target material is Te or TI as the base material.
8e, Pb, B1. Sb, S! 1. In,
Go.

Examples include alloys containing As and the like.

In the present invention, the fluoride gas to be mixed with Ar is a gas containing one or more organic or inorganic fluorides, such as tetrafluoromethane, tetrafluoroethylene, and chlorotrifluoroethylene.

Fluorocarbon gases such as trifluoroethylene, hexafluoropropylene, vinyl fluoride, vinylidene fluoride, fluorinated hydrocarbon gases, fluorochlorinated carbon gases, fluorinated chalcogens such as sulfur hexafluoride, tellurium hexafluoride, etc. Gases, nitrogen fluoride gases such as nitrogen trifluoride, and metal fluoride gases such as silicon tetrafluoride and germanium tetrafluoride are used.

/a or one or more of the above fluoride-reactive gases;
In a mixed gas with Ar gas.

The proportion of the reactive gas is selected so that the resulting sputter-deposited film is amorphous and does not cause significant damage to the substrate. discharge conditions.

The range varies depending on the type of reactive gas.

generally between 1-ro%c volume ratio). As a result, after annealing 0. It is desirable to contain fluorine atoms of /~30 atoms. Furthermore, in order to include S@ into the deposited film, a film using a TeSe alloy as a target was used.
A mixed gas of S@Fb and Ar may be used as the reactive gas.

After a sputtering deposited film containing Te and fluorine is formed on a substrate as described above, it is sufficiently stabilized by annealing. Annealing may be performed in vacuum, or in any atmosphere such as dry air or nitrogen atmosphere, but dry air or nitrogen atmosphere is preferable in order to maintain a uniform annealing atmosphere. Annealing is over 60℃
less than 30°C, preferably 60°C or more io.

It is carried out in an atmosphere of less than 0.degree. C., more preferably 60.degree. C. or more and 90.degree. C. or less. When using a plastic substrate, the temperature is preferably sufficiently lower than its softening point.

For example, 90C or less is desirable for a polycarbonate resin substrate.

Annealing must be performed until the crystal structure of the recording medium is sufficiently stabilized, but 10 minutes of hardness is sufficient for the recording medium of the present invention. However, in order to remove the garlic odor peculiar to Te-based recording media.

It is effective to perform annealing for about one hour.

Annealing may be performed by raising the temperature after sputtering is completed, but normally the material is taken out of the system and brought to room temperature, then heated and processed.

The recording medium in the present invention has a uniform amorphous structure before annealing, and has a polycrystalline structure with a crystal grain size of less than 70,001 even after annealing. especially.

It is possible to reduce the crystal grain size to several hundreds of degrees or less, and with a crystal grain size of this order, there will be no adverse effects such as generation of noise in the reproduction light or disturbance of the bit shape. 5. The amorphous structure referred to in the present invention refers to a film structure in which no clear crystalline peak can be found in ordinary X-ray diffraction, and a structure in which so-called microcrystals with a grain size of about several dozen or so exist. It also includes. In addition, a polycrystalline structure with a crystal grain size of less than t000A refers to all crystal structures in which the maximum crystal grain size in the film is less than 1000A, and includes amorphous, microcrystalline, polycrystalline, or a mixture of these. This includes Betello Yangzo and others. To be precise, such a structure is created using a transmission electron microscope.

This can be confirmed by observing a transmission image, a diffraction image, or a lattice image of the film.

In order to obtain a stable and fine crystal structure as described above after annealing, the fluorine content in the film after annealing must be 0. /%, 7θ atomic strength is desirable. (preferably 1-10 atoms), and the fluorine content is 1
%, the crystals after annealing tend to be larger than 10ooX. Although fluorine atoms can be contained up to about 0 atoms, it is not desirable to include more than 3 atoms because the bit shape will be disturbed.

In addition, when the temperature exceeds 0.05 to 100%, the crystallization temperature tends to become high.

The crystal structure of the recording medium is 100° C. or higher.

It is desirable that sufficient stabilization be achieved by annealing at a temperature below c, especially below qOC. In the recording medium of the present invention, the transition temperature of the crystal structure can be controlled within the above range by controlling the mixing ratio of the reactive gas and the Ar gas.

In the recording medium of the present invention, since F terminates the dangling bonds of Te, it has the effect of preventing oxidation of Te, but in order to further increase the oxidation resistance, S@ is added in addition to Te and r! ~Ko! It is effective to dissolve the atom atoms. Stabilization of the crystal structure by annealing is also effective in sputtering deposited films containing Te, F, and S@.

In the recording medium according to the present invention, a sputtering deposited film is formed on the substrate as described above.

Further, an undercoat layer may be provided between the substrate and the sputtered film to improve recording sensitivity, improve bit shape, etc. Furthermore, a protective film may be provided on the recording medium to protect the recording medium. You can also do it. In particular, it is effective to use fluorocarbon undercoat Me as the undercoat layer.

Hereinafter, the present invention will be explained in detail with reference to Examples. In Example 1, an example of a method for controlling the refinement of the crystal structure and the crystallization temperature after annealing is given.

In Example 2, the effect of crystal structure stabilization by annealing was clarified.

(Examples 1 to r) (Comparative Example 1.) FIG. 1 is an example of an apparatus for manufacturing an optical recording medium using unexploded 8AlC. In the figure (1) is a vacuum container.

(2) is the electrode, (3) is T@ or a metal target layer containing T@), (4) is the substrate, (5) is the gas inlet, (6) is the shutter, (force is the exhaust port. , vacuum container (1
) is evacuated to / 0-@Terr level, Ar gas is introduced through the inlet (5), and the internal pressure of the vacuum vessel (1) is set to rxi.
o-”Terr.Subsequently, a high frequency voltage is applied between the electrodes (2) to cause discharge.This state is called I
Metal target (3) shown in Table 1 after being held for about 0 minutes
Clean the surface. After that, the inside of the vacuum container is again IQ'''''
After exhausting to the Terr level, various fluoride gases and Ar gas as shown in Table 7 were introduced through the inlet (5) at the flow rate ratio shown in the table, and a high frequency voltage was applied between the electrodes (2). is applied to cause discharge.

The discharge power and the pressure inside the vacuum vessel (1) are as shown in Table 1. Note that a glass substrate with a thickness of 12 m was used as the substrate. The thickness of the obtained sputtering deposited film was 300 to 0.0 degrees. The cumulative fluorine content (FA%) in the film after annealing was 9 as shown in Table 1. In order to evaluate the annealing temperature required to stabilize the crystal structure of the sputtering deposited film, a 1 degree change in the transmittance of the recording medium on the glass substrate was measured. As an example of the pattern of temperature change in transmittance, the case of Example (6) in Table 1 is shown in diagram X2. The rapid change in transmittance in a narrow temperature range as shown in the figure is due to a change in the crystal structure of the film, that is,
X is due to the increase in crystal grain size and its stabilization.
This was confirmed by ray and electron diffraction as well as transmission electron microscopy images. 5 Table 1 shows the temperature at which the transmittance changes, that is,
The crystallization temperature of the film (corresponding to the dotted line in Figure 1) and the maximum value of the crystal grain size after crystallization are shown.

In Examples (1) to (8), a stable, uniform, and fine crystal structure is formed by annealing, and there is no adverse effect such as noise on the reproduction light. Further, there was almost no local unevenness in the laser light energy required for bit formation, that is, the sensitivity, and uniform pits were formed. Comparative example (IL
(2) shows the case where fluoride gas was not used and the case where CB or gas was used instead of fluoride gas. In the case of Comparative Examples (1) and (2), since the crystal grain size was large, the reproduction light noise was high and the pit shape was non-uniform.

As can be seen from the above examples, the crystal grain size of the recording medium of the present invention after annealing is sufficiently small.

It is possible to control the crystallization temperature, and in particular, it is possible to keep it below qo°C.

(Example 9) The recording medium of Example (6) was formed into a film on a disc-shaped polycarbonate resin substrate with guide grooves (tracks) for tracking, and changes in disk characteristics before and after annealing were examined. However, the annealing was performed in the air at 0° C. for 1 hour.

With the formation of a fine crystal structure due to clearing.

The reflectance of the recording medium becomes about 1.1 times the initial value and stabilizes. This allows the total signal strength to be increased without increasing the reproduced optical noise, resulting in an overall
3dB C/N ratio
ratio) was improved. The optical properties of the recording medium were completely stable in the 4jC110%RH accelerated test. Furthermore, when we examined the deterioration of the recording medium due to repeated irradiation of the same track with the reproducing light, we found that the deterioration of the medium began at a reproducing light power of 83 mm before annealing.

While accurate reproduction was no longer possible, it was completely stable after annealing.

It is clear from the above that the structure of the recording medium is sufficiently stabilized by cyanyl.

Similar effects were observed for all the media of Examples (1) to (7). Example (8) requires annealing at a temperature of 90° C. or higher in order to obtain the same effect as above, and is not suitable for use with a polycarbonate resin substrate.

In addition, when we examined the effect on the reproduction light noise when the birefringence after annealing of the polycarbonate resin substrate is at a speed of 'I Onm and when it is around Q nm, we found that when the birefringence is around Q nm, it is approximately λ~, 7 d
A decrease in the noise level of B was observed, and it was effective in improving the C/N ratio.

(Effects of the Invention) According to the present invention, an optical recording medium having a uniform, fine, and stable crystal structure can be obtained.

This has made it possible to record and reproduce stable, high-quality information over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an apparatus used in manufacturing the recording medium of the present invention, and FIG. 2 is a graph showing changes in transmittance due to temperature changes of an example of the recording medium of the present invention. In the figure, l is a vacuum container, C is 'IIL &, J is Tagera)
, II is the substrate, j is the gas inlet, 6 is the shutter, 7
indicates the exhaust port. Applicant Sanbin Kasei Kogyo Co., Ltd. Agent Patent attorney Hase Yo - 〇 and 1 other person)

Claims (7)

[Claims] (1) In an optical recording medium having a recording layer provided on a substrate, the recording layer is formed by reactive sputtering in a mixed gas of fluoride gas and Ar gas using Te or a Te-containing alloy as a target material. An optical recording medium characterized in that the obtained deposited film containing Te and F is annealed at a temperature of 60°C to 130°C. (2) The optical recording medium according to claim 1, wherein the recording layer after heat treatment has a polycrystalline structure with a crystal grain size of less than 1,000 Å. (3) The optical recording medium according to claim 1, wherein the heat treatment is performed at a temperature of 60°C or more and less than 100°C. (4) Fluorine content in the recording layer is 0.1 to 30 at%
An optical recording medium according to claim 1, characterized in that: (5) The optical recording medium according to claim 1, wherein the recording layer further contains 5 to 25 atom % of Se. (6) Claims characterized in that the substrate is transparent at least at the wavelength of light used for optical recording and reproduction, and has birefringence in the direction perpendicular to the substrate surface after annealing of 30 nm or less The optical recording medium according to item 1. (7) The optical recording medium according to claim 1, further comprising a pull-down layer made of a fluorocarbon film between the recording layer and the substrate.