JP2557347B2 - Optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention records and erases information by utilizing the reversible phase transition of a recording film due to irradiation with a light beam or the like. The present invention relates to a phase change type optical recording medium that can be used.

(Prior Art) In a phase-change type optical recording medium, information is recorded by, for example, irradiating a recording film with a light beam modulated by the recording information and rapidly heating and cooling the light beam to irradiate a portion irradiated with the light beam. This is done by the phase transition of the film from the equilibrium phase to the non-equilibrium phase, for example, from the crystal as the equilibrium phase to the amorphous as the non-equilibrium phase. Further, the recording is erased by irradiating the recorded amorphous portion with a light beam for erasing, heating it, and then gradually cooling it to return it to the crystal again. further,
Information is reproduced by irradiating a reproducing light beam and reading the difference in reflectance between the amorphous part where information is recorded and the crystal part where information is not recorded.

By the way, as a conventional phase change recording medium, Te,
It is known that a chalcogenide semiconductor such as Se is laminated on a substrate to form a recording film.

However, for example, since the equilibrium phase formation temperature of Te alone exists near room temperature (around 10 ° C), a light beam containing recorded information is irradiated to change the phase of the Te alone thin film from the equilibrium phase to the non-equilibrium phase. Even if recording is performed, the non-equilibrium phase portion may return to the equilibrium phase state due to aging, and the recording may be erased spontaneously.

In order to solve this, attempts have been made to stabilize the non-equilibrium phase by adding Ge to Te to raise the equilibrium phase temperature to room temperature or higher. In particular, TeGe has a eutectic composition in the composition range of Te _1-x Ge _x , O <x ≦ 0.5 and has a high non-equilibrium phase forming ability.
TeGe eutectic alloy thin film has attracted attention as a phase change type optical recording medium.

However, TeGe eutectic alloy also has poor chemical stability when made into a thin film, and gradually corrodes and deteriorates in the atmosphere.
The record is not stable.

(Problems to be Solved by the Invention) As described above, the conventional optical recording medium has a problem that the corrosion resistance is poor and a stable recording state cannot be maintained.

The present invention has been made based on the above problems, and an object thereof is to provide an optical recording medium capable of maintaining a stable recording state without erasing the recording for a long period of time.

[Structure of the Invention] (Means and Actions for Solving Problems) In order to solve the above problems, the present invention provides a recording film laminated on a substrate, which is a mixture thin film containing Te, Ge and In as main components To be formed.

When a small amount of In is added to the TeGe eutectic alloy, a stable compound consisting of the TeGeIn ternary system is formed. Thermal analysis of the non-equilibrium TeGe eutectic alloy with a differential scanning calorimeter (DSC) reveals two exothermic peaks of equilibrium phase formation corresponding to Te and GeTe, respectively, during the heating process. On the other hand, in the non-equilibrium phase TeGeIn ternary alloy in which a small amount of In is added to the TeGe eutectic alloy, only one exothermic peak of equilibrium phase formation is observed in the temperature rising process.
In the non-equilibrium phase TeGeIn ternary alloy, a small amount of In is added, so that one compound is formed to be in the equilibrium phase.

Therefore, the recording film formed of a mixture thin film in which a small amount of In is added to the TeGe eutectic alloy has very little deterioration over time, and a stable recording state is maintained.

(Embodiment) FIG. 1 shows a cross section of an embodiment of an optical recording medium according to the present invention. The optical recording medium 1 shown in the figure has a substrate 3, a first protective film 5, a recording film 7, and a second film. Protective film 9 and UV curable resin (U
V) The films 11 are laminated in this order and formed into a disk shape.

The substrate 3 is a transparent substrate formed of a resin such as acrylic, polycarbonate or epoxy, or glass.

The first and second protective films 5 and 9 are formed of SiO or SiO ₂ with a thickness of 50Å to 5000Å by sputtering or vapor deposition. These protective films 5 and 9 prevent formation of holes due to oxidation of the recording film 7 and evaporation of the recording film 7 during recording.

The UV film 11 is formed by applying a UV resin on the second recording film 9 and curing it with ultraviolet rays. The UV film 11 prevents mechanical damage such as cracking when the optical recording medium 1 is used. To be done.

The recording film 7 is a mixture thin film containing Te, Ge, In as main components, and is formed on the first protective film 5 by sputtering or vapor deposition.
It is deposited to a thickness of ~ 5000Å.

 This mixture thin film is represented by the following general formula.

(Te _1-x Ge _x ) _1-y In _y However, the range of 0 <x ≦ 0.5 and 0 <y ≦ 0.5 is preferable. Specific examples will be described below.

Example 1 A first protective film 5 was formed by forming a 1000 Å thick SiO ₂ film on an acrylic substrate by a sputtering method using a SiO ₂ target.

Next, by using Te target, Ge target and In target to adjust the power applied to each target by the ternary co-sputtering method, Te ₈₁ Ge ₁₅ In ₄ (a
recording film 7 consisting of t%) and the first protective film 5 with a thickness of 1000 Å
Formed on top.

Next, an SiO ₂ film having a thickness of 1000 ° was formed on the recording film 7 in the same manner as the first protective film 5 to form a second protective film 9.
Further, a UV resin was applied on the second protective film 9 and was cured by irradiating ultraviolet rays to form a UV film 11.

Since the recording film 7 formed as described above is in a non-equilibrium phase at the time of film formation, a 5 mW laser beam was continuously irradiated and gradually cooled to become an equilibrium phase. Then, a laser beam 15 having an output of 9 mW including recording information and a pulse width of 400 ns was irradiated and rapidly cooled to make the recording film 7 in a non-equilibrium phase and form a recording bit portion 13 to record information.

Further, it is possible to erase information easily and at high speed by irradiating the recording bit portion 13 in the non-equilibrium phase with a continuous laser beam having an output of about 3 mW to heat it to a temperature above the equilibrium phase forming temperature of the recording film 7 and gradually cool it. I was able to.

Figure 2 shows the results of an environmental test at a temperature of 60 ° C and relative humidity of 80% RH for a sample of a Te ₈₁ Ge ₁₅ In ₄ (at%) alloy thin film deposited on a glass substrate with a film thickness of 2000 Å by sputtering. .

In the same figure, the rate of change R / Ro with respect to the initial surface reflectance Ro is plotted, but there is almost no change in the rate of change R / Ro even after 20 days, indicating that the film is stably maintained. Recognize. As a result of X-ray diffraction, the sample immediately after film formation was in a non-equilibrium phase, and the sample 20 days later was also in a non-equilibrium phase.

(Comparative Example) As a comparative example, a Te thin film, a Ge thin film, and a Te ₈₅ Ge ₁₅ (at%) alloy thin film having a film thickness of 2000 Å are sputtered on a glass substrate.
Each of the samples formed in 1. was prepared and an environmental test was conducted at a temperature of 60 ° C. and a relative temperature of 80% RH in the same manner as in (Example-1).

As a result, the R / Ro of the conventional Te thin film was greatly reduced from the initial stage, and when the sample after 20 days was examined by X-ray diffraction, the recording film was already in the equilibrium phase. Further, R / Ro increased in the Ge thin film, and when a sample after 20 days was examined by X-ray diffraction, it was still in a non-equilibrium phase, but rust was generated on the entire surface. Furthermore, R / Ro gradually decreases in Te ₈₅ Ge ₁₅ which is a eutectic composition,
When the sample after 20 days was examined by X-ray diffraction, it was found to be partly in an equilibrium phase.

Thus, it was found that In mixing in the TeGe eutectic alloy is very effective for improving the corrosion resistance of the TeGe eutectic alloy and stabilizing the non-equilibrium phase.

[Effects of the Invention] According to the present invention as described above, since the recording film is composed of the mixture thin film containing Te, Ge and In as the main components, that is, the mixture thin film obtained by adding In to the TeGe eutectic alloy, The corrosion resistance of the eutectic alloy can be remarkably improved, and the stability of the non-equilibrium phase can be enhanced. Therefore, there is no risk of the recorded information being erased spontaneously, and the stable recording state is maintained for a long period of time. A high optical recording medium can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of the optical recording medium according to the present invention, and FIG. 2 is a diagram showing the surface reflectance change rate characteristics of the embodiment of the optical recording medium according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Optical recording medium 3 ... Substrate (base | substrate) 5 ... 1st protective film 7 ... Recording film 9 ... 2nd protective film 11 ... UV film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 61-152487 (JP, A) JP 62-208442 (JP, A) JP 62-222442 (JP, A) JP 59- 16154 (JP, A) JP 57-70694 (JP, A) JP 57-181443 (JP, A)

Claims (1)

(57) [Claims] 1. A phase-change type which records, reproduces, or erases information by utilizing reversible change between an equilibrium phase and a non-equilibrium phase by heating a recording layer by applying a light beam. In the optical recording medium of 1., a substrate, and a first protective film formed on the substrate with a thickness of 50 to 5000 Å by using either SiO or SiO ₂ by a sputtering method or an evaporation method, On the first protective film, tellurium (Te), germanium (Ge), and indium (In) are main components, and 0 <x ≦
When 0.5,0 <y ≤ 0.5, the mixture thin film represented by the general formula of (Te _1-x Ge _x ) _1-y In _y is formed with a thickness of 50 to 5000 Å by either the sputtering method or the vapor deposition method. After forming a thin film in a non-equilibrium phase state, the thin film in a non-equilibrium phase state at the time of film formation is continuously irradiated with a light beam having a first light output and gradually cooled to equilibrate. Information is recorded by forming a recording bit portion by irradiating a light beam of a second light output containing recording information higher than the first light output, rapidly cooling it, and changing to a non-equilibrium phase. The recorded information is erased by irradiating the recording bit of the non-equilibrium phase with a light beam having a third light output lower than the light output of No. A film and either SiO or SiO ₂ was formed on the recording film to a thickness of 50 to 5000 Å by either a sputtering method or an evaporation method. An optical recording medium comprising: a second protective film; and an ultraviolet curable resin layer in which an ultraviolet curable resin is applied onto the second protective film and cured by ultraviolet rays.