JPS62278091A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium having excellent mass- producibility, a long useful life and a high sensitivity, by specifying the structure of a recording layer. CONSTITUTION:An optical recording medium comprises a recording layer on a base member, and information is recorded by irradiating the recording layer with light to cause a thermal deformation or formation of openings or recessed parts in the recording layer. In such an optical recording medium, the recording leyer has a composition of the formula, wherein X, Y and Z are in the ranges of 1 atom%< X < 10 atom%, 0 atom%<= Y < 10 atom% and 5 atom%< + Z + 40 atom%, and M is at least one selected from Ga and Al. Zn used in the compositional range in an alloy in the recording layer together with Sb markedly enhances oxidation resistance, and also enhances recording sensitivity of the recording layer. Al and Ga enhance the oxidation resistance of the recording layer, and stabilize the layer by, for example, preventing coarsening of crystal grains due to deterioration with time, such as oxidation, of the layer. Sb enhances the oxidation resistance of the recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium, such as an optical disk or a laser COM, in which information is recorded using light.

[Conventional technology]

Conventional optical recording media include low melting point, low heat recording media containing -B i , Sb, TD, 11°Ga, In, ZnSCd, Ge, Sn, Pb, Te, etc. on transparent substrates such as glass or plastic. There is one in which a conductive metal thin film is formed and used as a recording layer. (Japanese Unexamined Patent Publication No. 130304/1983). In these optical recording media, Te, which is relatively easily oxidized, is used.
To improve the oxidation resistance, Se is added to the recording layer by co-evaporation or sputtering using a target containing 3e to improve the oxidation resistance (Japanese Patent Publication No. 59-35356). Public bulletin).

In addition, adjacent to the Te recording layer, there is a solid film layer of cr, Tt, v, MO, or 5bS3i, Ge, Sn, AQ,
There are optical information recording media (JP-A-60-133553 and JP-A-58-224446) in which a protective layer such as Cu or AQ is provided to prevent oxidation of Te.

[Problem that the invention seeks to solve]

However, this conventional technique has the following problems. For example, B'50S'25Pb251S disclosed in Japanese Patent Publication No. 52-130304
b40Z n55G a5, S b40Z n5
A recording film having a composition ratio such as 5Aα5 has problems such as low oxidation resistance, inability to obtain a practical life span, and inability to obtain practical recording characteristics.

In addition, in the case of a Te-based alloy containing Se, forming the recording layer by vacuum evaporation or sputtering is difficult because Se sublimes, making it difficult to control the composition. It was difficult and there were problems with mass production. moreover,
In order to obtain stable recording characteristics, annealing at 60'C for about 24 hours is required, which poses a problem of poor mass productivity.

Also, Or, Ti, V, MO nato (7) Fu 111 body skin 1
When the 1a layer was provided adjacent to the recording layer, there were problems in recording characteristics such as deterioration of pit shape and decrease in recording sensitivity. Furthermore, when the above-mentioned passive layer or protective layer such as sb is provided, the process of forming the medium film becomes complicated due to the multilayer film, and there is also a problem in mass production.

An object of the present invention is to improve such problems and provide an optical recording medium that is excellent in mass productivity, has a long life, and has high sensitivity.

[Means for solving problems]

The present invention provides an optical recording medium in which information is recorded by thermally deforming the recording layer, forming openings or recesses in the recording layer by irradiating the recording layer formed on a substrate with light. It is characterized by an optical recording medium having the following formula.

However, in the formula, X, Y, and Z are each 1 atomic %<
X<10 atom% 0 atom%≦Y<10 atom% 5 atom%<Z<40 atom%, and M in the formula represents at least one selected from (3a, AD).

As the recording layer of the optical recording medium of the present invention, an alloy thin film made of an alloy of Te and Zn to which at least one selected from AQ and Ga and sb are added as component elements is used. The elemental composition in the alloy of the recording layer is expressed by the following formula.

Formula (Tol-x70x) (1-Y-7) MySbz Here, X represents the atomic percent of Zn in the alloy composed of Te and Zn. In the present invention, X is 1 atomic %<X<1
It is used as 0 atomic %. When 7n is contained in the alloy of the recording layer together with Sb in the above composition range, it is possible to significantly improve the oxidation resistance and also has the effect of improving the recording sensitivity of the recording layer. Furthermore, when performing annealing to further stabilize the recording layer after forming the recording layer, the present invention has the effect of shortening the time to several hours or less. When X is less than 1 atomic %, no significant effect on improving the oxidation resistance of the recording layer is observed, and when it is 10 atomic % or more, the pit shape during recording is significantly deteriorated, making high-density recording difficult.

Y represents the atomic % of at least one metal selected from AfLSGa based on the total alloy composition of the recording layer. In the present invention, Y is used as 0 atomic %≦Y<10 atomic %. 80, and (3a is in the above-mentioned -5-' composition range, and by being included in the alloy of the recording layer together with 3b and zn, it improves the oxidation resistance of the recording layer and prevents oxidation etc. of the recording layer. It has a remarkable effect of stabilizing the recording layer, such as preventing coarsening of crystal grains due to deterioration over time. When the recording layer of the present invention contains Afi and Ga, one type of these elements may be used. However, it is natural that AQ and (3a) may be used together. In this case, AQ
The relative atomic composition of Ga and Ga is such that the sum of the atomic percentages of both elements is
The value of Y may be arbitrarily selected as long as it is within the range of the above-mentioned value of Y.

If Y is 10 atomic % or more, it becomes difficult to form the recording layer and requires long annealing in order to stabilize the physical properties of the recording layer. Furthermore, when a large amount of AD, Qa is contained, the pit shape deteriorates.

Furthermore, even when Y is O at %, relatively good recording characteristics and stability of the recording layer can be obtained.

Z indicates the atomic % of sb based on the total alloy composition of the recording layer. In the present invention, Z is used in amounts of 5 atomic % to 40 atomic %. sb has the effect of improving the oxidation resistance of the recording layer within the above-mentioned composition range, and in particular has the effect of improving the oxidation resistance of the recording layer.
By including it in the alloy of the recording layer together with u, the effect of improving oxidation resistance is remarkable. When Z is 40 atomic% or more,
recording layer.

There is a tendency for the pit shape to deteriorate as the pit shape deteriorates by several tens of percent. Furthermore, if 7 is less than 5 at %, no significant effect of improving the oxidation resistance of the recording layer is observed and the pit shape deteriorates.

A preferred composition that can obtain a better carrier-to-noise ratio during recording and reproduction is approximately 3 to 7 atomic % of X and Y.
is in the range of O to 5 at%, and Z is in the range of 11 to 30 at%.

In the above composition, the recording layer 4C,,l,(3
When containing a, it is natural that one type of element selected from these may be used, or a combination of 80 and Qa may be used. The composition ratio of ΔU and Ga at this time is not particularly limited as long as the sum of the atomic percent of ΔQ and Ga is within the above Y value range, and any composition can provide good recording properties and a recording layer. Stability can be obtained.

Within the range of the alloy composition of the recording layer described above, a preferred composition that can obtain a good recording layer with particularly good oxidation resistance and stability is approximately 3 to 7 atomic % of X and 0.1 atomic % of Y. ~5 atom %, and Z is in the range of 15 to 30 atom %. In the above composition, Aff and Ga contained in the recording layer of the present invention are:
One type of element selected from these may be used, or /
L and Ga may be used together. In particular, when using 80, the effect of improving oxidation resistance and stability is remarkable. ,
Furthermore, Ti, V, and Cr may be used as the alloy components of the recording layer within a range that does not impair the characteristics of the recording layer.

Mn, Fe, Go, Ge, S +, Sr, Nb, Ta,
Mo, Rh, Pd, Cu, ΔQ, Au, B +, 3n
, Pb, MCI, and the like. The ratio of these metals to the total alloy components is preferably less than about 3.0 atomic %, although it depends on the type of metal, since recording sensitivity and stability of the recording layer do not deteriorate.

The thickness of the recording layer of the present invention is 100 to 1oooo
It can be used as a person. In particular, in order to obtain high recording sensitivity as an optical disc, it is preferable to set the number to 100 to 1000 Å, and to obtain an even better carrier-to-noise ratio of recording and reproduction signals, it is preferably 200 to 600.

The substrate in the present invention may be the same as that used in conventional recording media, such as plastic or glass.

For the purpose of avoiding the influence of dust by recording from the substrate side using convergent light, it is preferable to use a transparent material as the substrate. Examples of the above-mentioned materials include polyester resins, acrylic resins, polycarbonate resins, epoxy resins, polyolenoin resins, and styrene resins. Preferred are polymethyl methacrylate, polycarbonate, and epoxy resin because they have low birefringence and are easy to form. Although the thickness of the substrate is not particularly limited, it is practically 10 microns or more and 5 mm or less. If it is less than 10 microns, it will be easily affected by dust even when recording with convergent light from the substrate side, and if it is more than 5 mm, it will not be possible to increase the numerical aperture of the objective lens when recording with convergent light, and the pit size will become large. Therefore, it becomes difficult to increase the recording density.

The substrate may be flexible or rigid. The flexible substrate can be used in the form of a tape or a sheet. The rigid substrate can be used in the form of a card or a circular disc.

The recording layer can be provided on one or both sides of the substrate as is known. Alternatively, a protective layer may be provided adjacent to the recording layer. Furthermore, if necessary, two substrates can be used to form an air sandwich structure, an air incident structure, a closely bonded structure, or the like.

The light used for recording on the optical recording medium of the present invention is light such as a laser beam or a strobe light. In particular, the use of a semiconductor laser allows for a small light source, low power consumption, and easy modulation. That's very good.

Thermal deformation, openings, or recesses formed in the recording layer by light irradiation are based on optical properties such as transmittance,
Any deformation, opening, or recess that has an easily detectable difference from the non-irradiated area in terms of reflectance, light scattering, etc. may be sufficient, but the opening or recess may be preferable.

As a method for forming the recording layer of the optical recording medium of the present invention on a substrate, various thin film forming methods in vacuum can be used. Specifically, a method of forming by sputtering using a target having an alloy composition of the recording layer or a composite target consisting of a single element or an alloy of elements contained in the alloy composition of the recording layer, an alloy of the recording layer, Alternatively, examples include methods of vacuum evaporation or ion blating using single elements constituting the element and compounds thereof. The sputtering method is preferable because it can reduce defects in the recording film and has good in-plane uniformity of composition and film thickness. The sputtering method is not particularly limited;
Either DC sputtering method or high frequency sputtering method may be used.
A bias may be applied roughly.

As the gas used for sputtering, a low active gas such as Ar1Ne gas can be used. Further, a mixture of these low active gases may be used. Further, gases such as nitrogen, oxygen, carbon dioxide, etc. may be mixed with these low active gases to the extent that the characteristics of the recording layer to be formed are not impaired.

The degree of vacuum during sputtering is not particularly limited, but
Usually, the vacuum level is about 1×10 to 5×10 Torr.

The power applied to the target during sputtering is not particularly limited, but for example, sputtering is performed with an input of about 50 W to 300 W to a circular target with a diameter of 6 inches.

Since the recording layer of the present invention does not contain highly sublimable components such as Se, abnormal phenomena such as selective sublimation of Se and the like due to overheating of the target are unlikely to occur on the target surface during sputtering. Therefore, it is possible to increase the sputtering speed, and it is excellent in mass productivity.

[Application]

The thus produced optical recording medium of the present invention includes an optical disk, an optical tape, an optical card, an optical floppy disk, a microfiche, a laser com medium, and the like.

The following will explain based on examples.

(Method for evaluating characteristics and evaluation of effects) (1) An optical disc was prepared by forming a recording layer on a transparent resin disc substrate with a diameter of 13 cm, a thickness of 1.2 mm, and a group of 1.6 μm pitch as a sample for evaluation. The evaluation was carried out.The recording layer was formed using a Δ
Using a composite target in which ff, Ga and sb are arranged according to the composition of the recording layer, the vacuum level is 2 x 10-2 Torr.
Planar magnetron high frequency sputtering was performed using Ar gas as the sputtering gas. The high frequency power source for sputtering uses a frequency of 13.56MH2,
The input power applied to the target during sputtering is 10
It was set to 0W.

(2) Method for evaluating recording characteristics The above-mentioned optical disk was rotated at a laser scanning speed of 4.0 m/s or 9.0 m/s, and a laser scan with a wavelength of 830 mm converged to a spot diameter of 2 μm was performed. Recording was performed by modulating the semiconductor laser light with IMI (2 to 3 M1-12 pulses) and irradiating the recording layer through the substrate.The recorded signal was then reproduced with the laser output set to 0.7 mW at the film surface. The carrier-to-noise ratio of the signal was measured.

(3) Recording layer life evaluation method The sample from (1) was placed in a constant temperature and humidity layer at 60°C and 90% relative humidity for 40 days. The occurrence of pinholes was investigated.

Example 1 On a polycarbonate resin disk substrate (Te
A recording layer having an atomic composition ratio of Zn6)B4AfiI5b15 and a film thickness of 400 layers was formed. Thereafter, annealing was performed at 60° C. for 3 hours. This optical disc has a film surface of 4 m.
Linear velocity 4.0m with laser light modulated to W, 2M1-12
The carrier-to-noise ratio was measured at 45 dB when the data was recorded and reproduced at a scanning speed of 10 seconds. Also, 7.5
linear velocity of 9.0 m/mW with laser light modulated at 3 MHz.
When recorded at a scanning speed of 1 second, the carrier-to-noise ratio of the reproduced signal was 50 dB.

This optical recording medium was placed in an environment of 60°C and 90% relative humidity.
When the above signals were reproduced after 0 days, the deterioration of the carrier-to-noise ratio was less than 3 dB in all cases. Further, almost no decrease in the intensity of the reproduced signal was observed. Furthermore, almost no pinholes were observed in the recording layer.

Example 2 On a polycarbonate resin disk substrate, (Teg4
A recording layer having an atomic composition ratio of Zn6>84Ga25b14 and a film thickness of 7,100 layers was formed. The bond, 60'
Annealing was performed at C for 3 hours. The optical disc was heated at a linear velocity of 4.0 using a laser beam modulated to 4mW and 2MH2 on the film surface.
After recording at a scanning speed of m/sec, the data was reproduced and the carrier-to-noise ratio was measured to be 45 dB. Also, 7
．． 5mW, linear velocity 9.0 with laser light modulated to 3MH2
When recording was performed at a scanning speed of m/sec, the carrier-to-noise ratio of the reproduced signal was 48 dB.

This optical recording medium was placed in an environment of 60°C and 90% relative humidity.
When the above signals were reproduced after 0 days, the deterioration of the carrier-to-noise ratio was less than 3 dB in all cases. Further, almost no decrease in the intensity of the reproduced signal was observed. Furthermore, almost no pinholes were observed in the recording layer.

Example 3 On a polycarbonate resin disk substrate, (Teg6
Zn4) 87.5 12.51S b (
T e 94 Zn6>865b14. (Teg4 Z°6)87
A recording layer having an atomic composition of 3b13 and a thickness of 400 layers was formed respectively. Thereafter, annealing was performed at 60'C for 3 hours. These optical discs were recorded and reproduced using a laser beam modulated to 4 mW and 2 MHz at a linear scanning speed of 4.0 m/s, and the carrier-to-noise ratios were measured to be 44 dB, 45 dB, and 43 dB, respectively. Ta.

When this optical recording medium was left in an environment of 60'C and 90% relative humidity for 20 days and the above signals were reproduced, the deterioration of the carrier-to-noise ratio was less than 3 dB in all cases. Further, almost no decrease in the intensity of the reproduced signal was observed. Furthermore, almost no pinholes were observed in the recording layer.

Example 4 An optical disk similar to Example 1 was produced except that an acrylic resin substrate was used instead of the polycarbonate resin disk substrate of Example 1. After annealing at 60° C. for 3 hours, the optical disc was heated at a linear velocity of 4.0 mW with a laser beam modulated to 2 MH2 on the film surface. After recording at a scanning speed of On/second, the data was reproduced and the carrier-to-noise ratio was measured to be 45 dB.

Also, 7.0 mW, modulated to 3M1-12 t;:t,'
When recording was performed using -v light at a scanning speed of 9.0 m/sec, the carrier-to-noise ratio of the reproduced signal was 50 dB.

This optical recording medium was placed in an environment of 60°C and 90% relative humidity.
When the above signals were reproduced after 0 days, the deterioration of the carrier-to-noise ratio was less than 3 dB in all cases. Further, almost no decrease in the intensity of the reproduced signal was observed. Furthermore, almost no pinholes were observed in the recording layer.

Comparative Example 1 Te855 was placed on a polycarbonate resin disk substrate.
A recording layer having a composition of b15 and having a thickness of 400 mm was formed.

Thereafter, annealing was performed at 60° C. for 3 hours. This optical disc was heated with a laser beam modulated to 2M1-IZ at a film surface of 5mW at a linear velocity of 4. After recording at a scanning speed of 0m/sec, the data was reproduced and the carrier-to-noise ratio was measured to be 40 dB. Further, when recording was performed using a laser beam modulated to 7.5 mW and 3 Mt-1z at a scanning speed of 9.0 m/sec, the carrier-to-noise ratio of the reproduced signal was 42 dB.

This optical recording medium was placed in an environment of 60°C and 90% relative humidity.
After 0 days, pinholes were observed in the recording layer.
A majority of parties were involved, and transparency was progressing throughout.

Comparative Example 2 On a polycarbonate resin disk substrate, (Teg4
Film thickness 400 with composition Zn6)g7 Sb3
Formed a human record layer. Thereafter, annealing was performed at 60° C. for 3 hours. This optical recording medium was heated to 60°C and relative humidity to 90%.
After 20 days in this environment, the recording layer had a large number of pinholes and had become transparent overall.

(Effects of the Invention) In the present invention, since the recording layer of the optical recording medium has a specific composition as described above, the following excellent effects can be achieved.

(1) Since the recording layer does not contain highly sublimable components such as Se, a recording layer with few defects can be easily formed by sputtering with good reproducibility, resulting in an optical recording medium with excellent mass productivity.

(2) A long-life optical recording medium with high recording sensitivity and excellent carrier-to-noise ratio could be obtained.

Claims (1)

[Claims] (1) In an optical recording medium in which information is recorded by thermally deforming the recording layer, forming openings or recesses in the recording layer by irradiating the recording layer formed on the substrate with light, the recording layer is The composition is according to the formula (Te_1_-_XZn_X)_(_1_-_Y_-_
An optical recording medium characterized by being represented by Z_)M_YSb_Z. However, in the formula, X, Y, and Z are each 1 atomic %<
X<10 atom%, 0 atom%≦Y<10 atom%, 5 atom%<Z<40 atom%, and M in the formula represents at least one selected from Ga and Al.