JP2940176B2 - Optical recording medium and recording / reproducing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium and a recording / reproducing method therefor, and more particularly to an optical recording medium such as an optical disk and an optical card capable of recording / reproducing information at a high density and a large capacity by a laser beam or the like, and its recording. Reproduction method.

[0002]

2. Description of the Related Art An optical recording memory such as an optical disk for recording and reproducing information on and from a medium by a laser beam or the like includes:
Because of its high recording density, it has excellent characteristics as a large-capacity recording device. Tantalum and lead were first used as this optical recording medium.
154, 1550, (1966)}. Thereafter, optical recording media of various materials and various configurations were developed. FIG. 2 shows a typical optical recording medium as a conventional example.

The optical recording medium shown in FIG. 2 has a reflective film 22 of AlCr provided on a substrate 1, a transparent interference film 23 of SiO ₂ , a trigger film 24 of a plasma polymerized film,
r pit forming films 25 are sequentially stacked. The recording / reproducing light beam 6 is irradiated with a laser beam having a wavelength of about 830 nm, which is focused on the recording film from the recording film side to about 1.4 μm without passing through the substrate 1. As the substrate 1, a polycarbonate resin plate, an acrylic plate with a photopolymer, a glass plate with a photopolymer, or the like is used, and a guide groove is usually provided.

When recording information, high-power light irradiation is performed in accordance with the information to be recorded, so that the pit forming film 25 absorbs light energy, converts the light energy into heat energy, and raises the temperature. At this time, the temperature of the lower trigger film 24 also rises, and is decomposed to form pits in the upper pit forming film 25. Therefore, the portions where the pits are formed by irradiating the high power light are formed on the reflection film 22.
Since the reflected light from the mirror returns as it is, the reflectance becomes high. Reading (reproduction) of information is based on detecting that reflected light due to irradiation with low-power light increases in the recording unit.

[0005] Such an optical recording medium and its recording / reproducing method can increase the change in absorptance before recording, and can also increase the change in reflectivity before and after recording. It also has the advantage that the read signal amplitude can be increased.

[0006]

However, in the above-described conventional optical recording medium and the recording / reproducing method thereof, if floating dust adheres to the optical recording medium, the portion becomes defective in recording or reading, resulting in a problem. Disadvantage.

In the optical recording medium and the recording / reproducing method of the present invention, light can be irradiated through the substrate while maintaining the recording / reproducing method in which the reflectivity of the recording section is increased. It is an object of the present invention to provide a device which does not have a problem of read error or read failure.

[0008]

An optical recording medium according to the present invention is an optical recording medium for recording / reproducing information by irradiating a recording film formed on a substrate with light, wherein the recording film has At least a first transparent interference film, a phase change film, a second transparent interference film, and a reflection film are provided, and the first transparent interference film and the second transparent interference film are a mixture of ZnS and SiO _2. The abundance of SiO ₂ in the mixture is at least 10 mol% and less than 20 mol%, and the phase change film is made of Ge ₂ Sb
₂ Te ₅ , and the reflective film is made of AlT
The thickness of each film is 55 nm to 75 nm for the first transparent interference film, and 4 nm to 15 nm for the phase change film.
nm, the second transparent interference film is 80 nm to 100 nm
And the reflection film is set in the range of 35 nm to 85 nm.

According to the recording / reproducing method for an optical recording medium of the present invention, a mixture of ZnS and SiO ₂
A first transparent interference film having an O ₂ abundance of 10 mol% or more and less than 20 mol% and a thickness of 55 nm to 75 nm, and Ge ₂ Sb ₂
Phase change in the thickness in the alloy composition of Te ₅ is 4nm~15nm film and ZnS and SiO ₂ in the mixture with a mixture of SiO ₂
And the thickness is 80% or more and less than 20% by mole.
an optical recording medium wherein at least a second transparent interference film having a thickness of 100 nm and a reflection film having a thickness of 35 nm to 85 nm made of an AlTi alloy are laminated, and a phase change film in an area to be recorded is in a crystalline state in advance. By applying high power light irradiation through the substrate corresponding to the information to be recorded, the reflectance of the high power light irradiation part is made higher than the reflectivity before high power light recording. Is done.

[0010]

The optical recording medium of the present invention comprises a substrate, ZnS and S
The mixture with iO ₂ has a SiO ₂ abundance of 10 in the mixture.
At least 55 mol% and less than 20 mol% and a thickness of 55 nm to 75 nm
A first transparent interference film, a phase change film having a compound composition of Ge ₂ Sb ₂ Tb ₅ and a thickness of 4 nm to 15 nm, ZnS and S
The mixture with iO ₂ has a SiO ₂ abundance of 10 in the mixture.
At least 80 mol% and less than 20 mol% and a thickness of 80 nm to 100 n
m, a second transparent interference film having a thickness of 35 n
and a reflective film of m to 85 nm.

A light beam for recording and reproduction is incident through the substrate, and is condensed to about 1.4 μm on the recording film. As a light source for the light beam, a semiconductor laser having a wavelength of about 830 nm is usually used. Since the phase change film is usually in an amorphous state immediately after the film is formed, the state before recording is changed to a crystalline state in advance by performing an annealing process.

When binary information consisting of an arbitrary sequence of "1" and "0" is recorded on the optical recording medium as described above, high-power light irradiation corresponding to "1" is performed. The phase change film at the portion where "1" is to be recorded is rapidly cooled after melting to be in an amorphous state. In order to change from the crystalline state before recording to the amorphous state after recording as described above, the thermal conductivity, specific heat, density, and film thickness of the first and second transparent interference films and the thermal conductivity, specific heat, This cannot be realized unless the density / film thickness and the material composition and film thickness of the phase change film are optimized.

In order to increase the reflectivity of the medium by changing the phase change film from a crystalline state before recording to an amorphous state after recording, the refractive indices of the first and second transparent interference films are required. -Refractive index and extinction coefficient of film thickness and reflective film-Refractive index of crystalline state of film and phase change film-Refractive index of amorphous state and amorphous state Can not.

Further, the quality of the recording / reproducing signal greatly depends not only on the physical properties of the phase-change film but also on the physical properties of the transparent interference film and the reflective film. Therefore, optimization is necessary from this viewpoint.

Further, from the viewpoint of long-term storage in a high-temperature, high-humidity environment, the materials of the transparent interference film, the phase change film, and the reflection film must be optimized.

Although the optical recording medium of the present invention does not have a clear guiding principle, it has been achieved through various experiments.

When the phase change film is Ge ₁ Sb ₂ Te ₄ , the storage characteristics in a high temperature state are not better than that of Ge ₂ Sb ₂ Te ₅ , and an optical recording medium having the same characteristics cannot be manufactured stably. And a phase change film of Ge ₂ Sb ₂ Te ₅ .

The first and second transparent interference films are made of Zn.
Abundance of SiO ₂ in the mixture with a mixture of S and SiO ₂ is desirably less than 10 mole% to 20 mole%. When the abundance of SiO ₂ in the mixture is less than 10 mol%, the flatness of the film surface is poor, and the noise is large, which is not desirable. on the other hand,
In the case of 20 mol% or more, the film surface is flat and good,
Since the refractive index becomes as small as 2.0 or less, it is not desirable.

As a reflection film, an AlTi alloy (containing Ti)
The amount is 1% by weight . When the Al film is stored in a high-temperature, high-humidity environment for a long time, corrosion occurs, which is a problem.

The problem of corrosion does not occur in alloy films such as Au and AuPd, but the problem is that the adhesive strength of the film is not sufficient.

The recording mechanism of the optical recording medium of the present invention is mainly that the phase change film changes from a crystalline state to an amorphous state, but the second transparent interference film and the reflection film slightly deform. It doesn't matter how much you do.

[0022]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

The optical recording medium shown in Figure 1, was placed diameter 300mm which guide grooves are formed by a photopolymer, a substrate 1 of a glass disc having a thickness of 1.18mm into the sputtering apparatus, 1 × 10 ^- After evacuation to ⁶ Torr or less, the photopolymer layer is reverse-sputtered by about 5 nm, and then ZnS and S are deposited using a composite sputter target in which an SiO ₂ chip is placed on the ZnS sputter target.
A transparent interference film 2 having a thickness of 65 nm was formed from a mixture with iO ₂ . The abundance ratio of SiO _{2 in} the transparent interference film 2 was determined by RBS (Rutherford Back Scattering).
It was 15 mol% as measured by the method.

Next, a phase change film 3 having a thickness of 10 nm was formed using a Ge ₂ Sb ₂ Te ₅ sputter target. When the composition of the phase change film 3 was measured by an ICP method later,
The composition was almost the same as the sputter target composition.

Next, a transparent interference film 4 having a thickness of 90 nm is formed in the same manner as when the transparent interference film 2 is formed.
After forming a reflective film 5 having a thickness of 40 nm using a Ti sparter target (the content of Ti was 1% by weight), the film was taken out of the sputtering apparatus into the atmosphere.

After that, an ultraviolet-curing resin is
A fat (not shown; also referred to as a UV- curable resin) was spin-coated, and the UV- curable resin was cured by UV irradiation to form a protective film having a thickness of about 9 μm.

Thereafter, the two discs were bonded by hot melt so that the recording film was on the inside.

This was initialized by irradiating an elliptical beam at a constant medium linear velocity of 5.65 m / sec to align the phase change film 3 over the entire area of the disk in a crystalline state, thereby producing an optical recording medium.

The optical recording medium thus manufactured as shown in FIG.
The recording film was irradiated with a 0-nm semiconductor laser beam through the substrate 1 to a diameter of about 1.4 μm. The reproduction beam power used for the tracking servo and the focusing servo was 1.5 mW.

At a linear velocity of 8.01 m / sec, a signal having a recording frequency of 6.28 MHz is applied for 10 m at a pulse width of 50 nsec.
When recording was performed with a recording power of W, the C / N ratio as high as 58 dB was obtained in a recording mode in which the reflectance after recording increased.
was gotten. Even when a signal having a recording frequency of 3.14 MHz was recorded in the same manner, a good value of 61 dB was obtained for the C / N in the recording mode in which the reflectance after recording increased.

Even after storing this optical recording medium in a high temperature and high humidity environment of 80 ° C. and 90% for 500 hours, there is no corrosion or peeling.
The signal quality such as C / N was also good and it was confirmed that it could be put to practical use.

The optical recording media shown in Comparative Examples 1 to 7 were manufactured by comparing the optical recording media shown in FIG. 1 with the same material for each film and changing only the film thickness as shown in Table 1. When the recording / reproducing characteristics were measured in the same manner as in the example shown in Table 1, the optical recording medium was not a practically usable optical recording medium, as described in the reason for failure described in the right column of Table 1.

[0034]

In the above embodiment, AlTi ( including Ti) was used.
An example was shown in which the thickness of the reflective film consisting of 1% by weight) was set to 40 nm, but only this was changed to 80 nm, and the others were the same as in the embodiment shown in FIG. Was evaluated.

As a result, except that the value of the optimum recording power is increased by about 1 mW as compared with the embodiment shown in FIG.
Other properties were almost the same and good.

[0037]

The optical recording medium and the recording / reproducing method of the present invention can be used in a reflectance-enhanced mode recording in which the recording sensitivity is good and the readout signal amplitude is large. This has the effect of enabling optical recording with excellent long-term storage properties in a humidity environment.

[0038]

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2,4,23 Transparent interference film 3 Phase change film 5,22 Reflection film 6 Light beam for recording / reproduction 24 Trigger film 25 Pit formation film

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) G11B 7/24 G11B 7/00

Claims (2)

(57) [Claims] 1. An optical recording medium for recording / reproducing information by irradiating a recording film formed on a substrate with light, wherein the recording film comprises at least a first transparent interference film, a phase change film, and a second And the first transparent interference film and the second transparent interference film are made of ZnS and S
The mixture with iO ₂ has a SiO ₂ abundance of 10 in the mixture.
Mol% or more and less than 20 mol%, the phase change film is a compound composition of Ge ₂ Sb ₂ Te ₅ , and the reflection film is an AlTi alloy, and the thickness of each film is the first transparent interference. The film is in the range of 55 nm to 75 nm, and the phase change film is 4
nm to 15 nm, the second transparent interference film is 80 nm to
An optical recording medium having a range of 100 nm and a reflective film set in a range of 35 nm to 85 nm. _2. A first transparent interference film comprising a mixture of ZnS and SiO ₂ on a substrate, wherein the content of SiO ₂ in the mixture is at least 10 mol% and less than 20 mol% and the thickness is 55 nm to 75 nm, and Ge _2. Compound composition of Sb ₂ Te ₅ with thickness of 4 nm to 1
A phase change film having a thickness of 5 nm, a mixture of ZnS and SiO ₂ , a second transparent interference film having a thickness of 80 nm to 100 nm with an abundance of SiO ₂ in the mixture of 10 mol% or more and less than 20 mol%, and a thickness of AlTi alloy; A reflective film having a thickness of 35 nm to 85 nm is laminated at least, and a phase change film in an area to be recorded is formed of an optical recording medium in a crystalline state in advance.
Optical recording characterized in that high-power light irradiation is performed through the substrate in accordance with the information to be recorded, so that the reflectivity of the high-power light irradiation part is higher than that before the high-power light irradiation. A recording / reproducing method for a recording medium.