JPH0355293A - Optical recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To extend the life of an optical recording film and to enlarge a recording margin by forming the recording film from a thin film based on Te and containing Cr, C and H and specifying the containing ratio of Cr and C contained in the recording film. CONSTITUTION:A recording film is composed of a thin film based on Te and containing Cr, C and H and the containing ratio of Cr and C in the recording film is set so that Cr is 0.1-40 atomic% to the total number of atoms constituting the recording film and C is 5below 50 atomic%. By this method, the oxidation resistance and durability of the recording film are enhanced and the life of an optical recording medium is extended and excellent recording sensitivity is obtained and a recording margin is enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an optical recording device in which t, 'f information is recorded by forming bits on a recording film on a substrate by irradiating energy beams such as light or heat. It relates to a medium and its manufacturing method.

Technical Background of the Invention and Problems There are two types of optical recording media: one in which a physical change such as a hole or a groove is formed in a part of the recording film by irradiation with an energy beam, and the other in which a part of the recording film is physically changed by irradiation with an energy beam. There is a method in which an optical property changing part is formed by changing the optical properties (refractive index, reflectance, etc.) in the part.

As a recording film for any type of optical recording medium, a recording film mainly composed of a low melting point metal such as tellurium (Tθ) has been known (Japanese Patent Application Laid-open No. 71195/1983,
(Japanese Unexamined Patent Publication No. 58-9234). Tell [, a typical low melting point metal film, is a material that can produce desired physical changes or optical property changes with very low energy (hereinafter collectively referred to as
It is extremely promising as a highly sensitive material. Sensitivity here is defined in terms of bits per unit area or required energy (sJ/cj).

However, when To is left in the atmosphere, it is oxidized by oxygen or moisture, increasing its light transmittance and becoming transparent. When such Te is used as a recording film, the film thickness is extremely thin, on the order of several hundred λ, so if the light transmittance increases due to oxidation of the film, the sensitivity will drop significantly. That is, when the film is oxidized, its melting temperature and evaporation temperature rise, and because it becomes transparent, it absorbs less energy such as light, so the energy required to form a bit increases, resulting in a significant decrease in sensitivity.

For example, when a Te film is left in an atmosphere with a temperature of 70° C. and a relative humidity of 85%, the sensitivity decreases by about 20% in about 5 hours and by about 50% in about 15 hours.

In order to solve these problems, various measures have been taken to prevent oxidation of the T e film. One known method is to coat Tell% with a stable inorganic substance, but although this coating is effective in preventing oxidation of the Tθ film, it reduces sensitivity and is expensive. Not put into practical use. On the other hand, a method of coating Te@ with plastic is also known, but this method is advantageous because the thermal conductivity of plastic is low, so it does not impair sensitivity to a small extent, but it allows oxygen and water to pass through relatively easily. , Tell[ is not very useful in preventing oxidation.

In addition, C and H are included in the Te film (Japanese Patent Publication No. 1983-
33320), Tel as a recording layer.
A technique to prevent oxidation of ljl has also been proposed, but this technique still has insufficient oxidation resistance when the C content is low. When increasing the C/N during information reproduction,
This has the disadvantage that the ratio decreases.

In addition, in order to solve the above-mentioned problems,
No. 63,038 discloses an optical recording medium having a recording film containing Te as a main component and Cr.

As disclosed in this publication, when Cr is contained in a recording film whose main component is Te, the oxidation resistance of the recording film improves in proportion to the content, extending the life of the optical recording medium. It is known that this can be achieved.

However, an optical recording medium having a recording film containing To as a main component and Cr has the disadvantage that recording sensitivity decreases if a large amount of Cr is contained. Therefore, Cr contained in the recording film whose main component is Te.
From the viewpoint of improving oxidation resistance and recording sensitivity, the content of
Generally, Cr was determined to be 5 to 15% by weight relative to Te in the recording film 11.

However, the recording sensitivity of an optical recording medium equipped with a Te-based recording film containing 5 to 15% by weight of Cr is
The inventors have found that this is still lower than that of a recording film containing only l. The inventors have proposed that such T
After intensive study on optical recording media having a recording film containing e as a main component and Cr, it was found that an optical recording medium having a recording film mainly containing Te containing a specific amount of Cr and containing C and H was found. It has been found that although the medium has improved oxidation resistance, the recording sensitivity is significantly improved compared to a To-based recording film containing a large amount of Cr, and the recording margin is widened. In addition, the present inventors have found that if a heat treatment is performed after forming a recording film containing Cr, C, and H and mainly composed of Te on the substrate, the recording sensitivity can be further improved. It was found that the recording margin was widened.

Purpose of the Invention The present invention was made based on such new knowledge, and aims to improve the oxidation resistance of the recording film, especially under high temperature and high humidity conditions, to extend the life of the optical recording film, and to reduce the size of the optical recording film. An object of the present invention is to provide an optical recording medium on which information can be recorded using energy, high sensitivity, and a wide recording margin, and a method for manufacturing the same.

Summary of the Invention In order to achieve the above object, an optical recording medium according to the present invention includes a substrate and a recording film formed on the substrate, and by irradiating the recording film with an energy beam, In an optical recording medium in which information is recorded by forming bits in this recording film, the recording film is a thin film containing Te as a main component and CrSC and H, and Cr and C contained in the recording film. The content ratio of Cr is 0.1 to the total number of atoms forming grooves in the recording film.
The content of C is in the range of 5 to 40 atomic %, and the content of C is 5 to 40 atomic %.

Further, the optical recording medium according to the present invention is composed of a substrate and a recording film formed on the substrate, and by irradiating the recording film with an energy beam, bits are formed in the recording area to form information. In an optical recording medium for recording, the recording film is a thin film containing To as a main component and Cr, C, and H, and the content ratio of Cr contained in the recording film is higher than the T in the recording film.
The content ratio of C contained in the recording film is in the range of 0.1 to 40 at% with respect to the total number of atoms of Te, Cr and C in the recording film. It is characterized by being in the range of 5 to 40 atomic %.

According to the optical recording medium according to the present invention, since the recording film containing Te as a main component contains CrSC and H, the oxidation resistance of the recording film is improved and the length of the optical recording medium is increased. You can expect a longer lifespan.

Moreover, in the present invention, the content of C is set in the range of 5 to 40 atomic % based on the total number of atoms in the recording film or the total number of atoms of Te, Cr, and C in the recording film. In particular, oxidation resistance under high temperature and high humidity conditions can be significantly improved. In addition, in the present invention, the content of Cr in the recording film is
0.1 to 40 atomic %, especially 0.5 to 40 atomic %, based on the total number of atoms in the recording film or the total number of Te and Cr atoms in the recording film.
If the value is set to 10 atomic %, which is lower than the conventional value, the recording sensitivity will be superior to that of the conventional TO film with a high Cr content.

Further, in order to achieve the above object, the method for manufacturing an optical recording medium according to the present invention is characterized in that after the above-described recording film is formed on the substrate, the recording film is heat-treated.

The heat treatment is preferably performed at a temperature of 70 to 300°C for 5 seconds or more.

According to the method for manufacturing an optical recording medium according to the present invention, since the formed recording film is heat-treated, the bit shape formed on the recording film can be made uniform even by minute fluctuations in the recording energy output. The recording margin is widened, the C/N ratio is improved, and the recording sensitivity of the resulting optical recording medium is improved.

In the present invention, a narrow recording margin means that the C/N ratio changes in accordance with fluctuations in the recording energy output (hereinafter used with the same meaning).

In other words, when the recording margin is narrow, there is a decrease in the C/N ratio when the recording energy output is increased, and a constant C/N ratio is observed.
This means that the range of recording energy output that indicates the N ratio is narrow. Further, the C/N ratio indicates the amount of noise during information reproduction, and the higher the C/N ratio, the better.

DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described in detail based on embodiments shown in the drawings.

FIG. 1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention.

As shown in FIG. 1, the optical recording medium 10 according to the present invention includes:
It consists of a substrate 11 and a record @12 formed on the surface of this substrate.

In addition to inorganic materials such as glass or aluminum, the substrate 11 may also be made of polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, such as ethylene and 1,4,5,8-dimethanol t,2,! 1,4.4a. 5,8.8a-Copolymer of octahyde-naphthalene (tetracyclododecene), ethylene and 2-methyl-1.4.5.8-dimethano-1.2.3.4.4a,5.8. Copolymer of 8a-octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1.4,5.8-dimethanol-l, 2.3,4,4a. U.S. Patent No. 46147, such as a copolymer with 5,8.8a-octahydronaphthalene.
Amorphous polyolefin as shown in No. 78 specification,
Organic materials such as poly4-methyl-1-bentene, epoxy resin, polyethersulfone, polysulfone, polyetherimide, and ethylene/tetracyclododecene copolymer can be used. The thickness of this substrate 11 is sufficient as long as it provides appropriate rigidity to the entire recording medium 10, and is preferably 0.25 mm thick. 5-2.
5 mm, particularly preferably about 1 to 1.5 mm.

The recording film 12 according to the present invention has Te as a main component, Cr,
It is a thin film containing at least C and H, and may also contain low melting point elements other than Te or other components. Elements other than Te that can be included in the recording film 12 include TI, Mn. ．． NiZr, Nb, TasAfiSP
tSSm, BiIn. Se, Pb. CO% S[
Examples include Pd, Sn, and Zn.

The content ratio of Cr contained in such a recording film 12 is 0.1 to 40 atomic %, preferably 0.5 to 10 atomic %, particularly preferably 1 atomic %, based on the total number of atoms contained in the recording film.
~4 at%, or the content ratio of Cr to the total number of Te and Cr atoms in the recording film is 0,
It is preferably in the range of 1 to 6 atomic %, preferably 0.5 to 15 atomic %, and particularly preferably 1 to 6 atomic %.

This is because by including Cr in such a range, even though the oxidation resistance of the recording film 12 is improved, the recording sensitivity does not decrease, and in some cases, the recording sensitivity can be improved.

In addition, the content of C in the recording film 12 is determined based on the number of atoms in the entire recording film from the viewpoint of improving the life of the recording film and recording sensitivity.
5 to 40 atomic %, preferably 5 to 20 atomic %, more preferably 5 to 10 atomic %, or 5 to 40 atomic %, preferably 5 to 40 atomic %, based on the total number of atoms of Te, Cr and C in the recording film. 20 at%, more preferably 5 to 10 at%
It is desirable that By containing C in such a range, oxidation resistance, especially under high temperature and high humidity conditions, can be improved without significantly lowering recording sensitivity and recording margin.

Further, the content of H in the recording film 12 is desirably 5 to 40 atomic %, preferably 5 to 25 atomic %, based on the entire recording film 12 from the viewpoint of life span and the like. In addition, in the present invention, the content of each element contained in the record film 12 is defined as metal elements (To, C).
r, etc.) by ICP emission spectrometry (inductively coupled plasma emission spectrometry), C by X-ray photoelectron spectroscopy (XPS), (ESCA), and H by organic elemental analysis.

In order to write information on the recording film 12 having the above composition, an energy beam such as a laser beam that is modulated (on/off) depending on the information to be recorded is applied to the recording film 18112.
A bit may be formed in the irradiated area 1.1 by irradiating the area. This pin 1 may be a physically changed part such as a hole or a recess, or it may be an optical property changed part in which optical properties such as refractive index or reflectance are changed.

Such a record II! The film thickness of I12 needs to be thick enough to obtain sufficient light reflectance and thin enough not to impair sensitivity. Specifically, when forming a physically changed part such as a hole in the recording film 12, the film thickness of the recording film is 100 mm.
λ to 1 μm, preferably 100 to 5000, more preferably about 150 to 500 λ. In addition, when forming an optical characteristic change part such as reflectance or refractive index in recording@12, the film thickness of the recording film is 100λ to 1μm, preferably 1μm.
00-5000 people, preferably 200-2000 people
It is about λ.

The recording film 12 of this type can be deposited on the surface of the substrate 11 in the following manner, for example.

First, using Te and Cr as separate targets or a Te-Cr alloy as a target, magnetron sputtering was performed in a mixed gas of Ar gas and an organic gas containing C and H, such as CH or C2H2 gas. , substrate 11
, a diary film 12 made of a Te--Cr alloy thin film containing C and H is formed. It is also possible to form the recording film 12 made of a Te-Cr alloy thin film containing C and H on the substrate by forming CH4 and Te-Cr alloy vapor into plasma without using the sputtering method. A similar recording film 12 can also be formed by vapor phase epitaxy or plasma vapor phase epitaxy. As another method, some or all of the TeSCr, C, and H atoms may be ionized and deposited on the substrate in the form of a beam.

The atomic ratio of Te and Cr in the recording film 12 made of such a Te-Cr alloy thin film containing C and H is T
When sputtering e and Cr simultaneously, it can be freely controlled by the respective applied voltages, and if an alloy target is used, by the alloy composition. Further, the content of C and H in the recording film 12 made of a Te-Cr alloy thin film is CH
It can be freely controlled by the mixing ratio of 4 and Ar and the applied high frequency power. In this case, the H content at which the film is most chemically stable is determined by the C content. Here, the H content can be arbitrarily selected as long as it is not so large that hydrogen gas (H2) is generated in the film. Furthermore, since the film thickness is proportional to the sputtering time, it can be freely controlled.

Te-containing C and H formed in this way
The optical properties such as reflectance or extinction coefficient of the recording film 12 made of a Cr alloy thin film vary depending on the content of C and H, and in order to use it for information recording, it is necessary to The film thickness is determined.

In addition to the above-mentioned methane and acetylene, ethane and the like may also be used as the hydrocarbon introduced into the thin film manufacturing apparatus when forming the recording film, but methane is most preferred. Such hydrocarbons are usually introduced into thin film production equipment together with an inert gas. Examples of the inert gas used at this time include helium, neon, argon, krybton, etc. Argon is preferred.

The recording film 12 formed under the above conditions has significantly improved oxidation resistance and recording sensitivity compared to a film formed from a single low-melting point metal such as To.

For example, Cr. In a Te recording film containing C and H, the change in reflectance after 100 hours under conditions of 70°C and 85% RH (relative humidity) is smaller as the Cr content increases; It has been confirmed through experiments that the oxidation resistance of the recording film according to the present invention is improved compared to the above.

Further, it has been experimentally confirmed that, for example, the recording film according to the present invention has a relatively small recording energy output and an improved recording sensitivity.

Furthermore, as shown in FIG. 2, the optical recording medium according to the present invention (curve A in the figure) is compared to the conventional optical recording medium having a Te film containing C and H (line III B in the figure). do,
It was confirmed that the C/N ratio hardly changes with respect to minute fluctuations V in the recording energy output, and the recording margin is wide.

Furthermore, as shown in FIG. 3, the optical recording medium according to the present invention (curve A in the figure) is different from the conventional Te
It was also confirmed that, compared to an optical recording medium having a film (curve B in the figure), there was almost no change in reflectance over time and the durability was improved. This is also clear from Table 2.

Further, in the present invention, as described above, the recording film 1 is placed on the substrate 11.
After forming the recording film 2, the recording film 12 or the journal film 12 and the substrate 11 can be heat-treated in an inert gas, reducing gas, or oxygen-containing gas atmosphere, if necessary. The heat treatment temperature needs to be below the melting point of Te contained in the diary film, preferably 70 to 300
℃, especially a temperature range of 90 to 150℃ is preferable. The heat treatment time is preferably 5 seconds or more, particularly preferably 5 seconds to 10 hours, and most preferably 5 minutes to 2 hours.

In this way, Record II! By heat-treating the recording film 12 or the recording film 12 and the substrate 11 after forming the recording film 12 on the substrate 11, the recording sensitivity of the recording film is improved and the recording margin is widened.

Note that the present invention is not limited to the embodiment shown in FIG. 1, and can be variously modified within the scope of the present invention.

For example, as shown in FIG.
During this time, the base layer 13 may be laminated.

As the base layer 13, for example, magnesium fluoride (M
g F2), etc., silicon oxide (S1
0, SlO) or 2 or a silicon compound film made of silicon nitride (Sl3N,), TiNICr,AN or N1-
Metal thin films made of Cr etc., thin films of fluorine-substituted hydrocarbon compounds and/or their polymers such as polytetrafluoroethylene (PTFE) thin films, Cr-C-H thin films (films containing Cr, C and H), etc. is used. The thickness of the base layer 13 varies depending on its material, but is generally 10 to 1,000 thick, preferably 50 to 500 thick.

By setting the film thickness in this manner, transparency can be maintained and various characteristics as the base layer 14 can be developed.

In order to form such an underlayer 13 on the surface of the substrate 11, as in the case of forming the recording layer 12, magnetron sputtering method, vapor phase elongation method, plasma vapor phase epitaxy method, vapor deposition method, or Subinco-1 method can be used.・This can be done by applying a method.

If such an underlayer 13 is provided between the substrate 11 and the recording film 12, the recording sensitivity will be further improved and, in some cases, the recording margin will be further expanded.

Further, according to the present invention, a surface layer may be formed on the surface of the recording film 12 in the optical recording medium 10 shown in FIG. 1 or 4. The material forming the surface layer is
Elements of the recording film, oxides such as St and T1, nitrides, metals, etc. are used. The thickness of the surface layer varies depending on the material, but is 5 to 100 mm, preferably 10 to 50 mm.

Effects of the Invention In the present invention, since Cr, C, and H are contained in the recording film mainly composed of Te, the oxidation resistance and durability of the recording film are improved, and the life of the optical recording medium is extended. can be expected. Moreover, in the present invention, the C content is determined by the total number of atoms constituting the recording film or the To, Cr, and C content in the recording film.
Since the amount is in the range of 5 to 40 atomic % based on the total number of atoms, the oxidation resistance can be significantly improved, especially under high temperature and high humidity. In particular, the content of Cr in the recording film is set to 0.1 to 40 at%, especially 0.1 to 10 at%, or the total number of Te and Cr atoms in the recording film, based on the total number of atoms constituting the recording film. On the other hand, excellent recording sensitivity can be obtained by setting it to a value lower than conventional values, such as 0.1 to 60 atomic %, especially 0.1 to 15 atomic %.

Further, according to the method for manufacturing an optical recording medium according to the present invention, since the heat treatment is performed after the recording film is formed, the bit shape formed on the recording film can be made uniform and small, and the recording film can be made uniform and small. This has excellent effects such as widening the range of energy output (widening the recording margin) and improving the recording sensitivity of the resulting optical recording medium.

[Examples] The present invention will be described below based on more specific examples, but the present invention is not limited to these examples.

Example 1 After evacuating the vacuum container, Ar gas and CH4 gas were introduced, and the internal pressure was set to 6 X 10""'Tnrr (7
Ar/CH4-2/8: gas flow rate ratio). Next, simultaneous sputtering was performed using To and Cr as targets. At that time, by controlling the voltage applied to each target and controlling the spatter time, the recording film of Te53Cr2C15H3o was formed to a thickness of 2.
50 pieces were obtained on a non-quality polyolefin substrate.

Example 2 The gas flow rate ratio is A r / C H i, - 8 /
T (3 go
A recording film of C r 3C e H t t and a film thickness of 240 mm was obtained on an amorphous polyolefin substrate.

Example 3 T +3 82C r x C e in the same manner as in Example 1 except that the gas flow ratio was Ar /CH, -8/2
A recording film with a thickness of 220 mm was obtained on an amorphous polyolefin substrate.

Comparative Example 1 Gas flow rate ratio A r / C H 4-9 / 1
A recording film having a thickness of 250 mm was obtained on an amorphous 8947 polyolefin substrate in the same manner as in Example 1 using a target of To C H .

Reference Example 1 In the same manner as in Example 1, only Ar was introduced, and
A recording film made of Cr and having a film thickness of 250 mm was obtained on an amorphous 973 polyolefin substrate.

The recording media (recording films) of Examples 1 to 3 were each subjected to heat treatment at a temperature of 100°C for 20 minutes in an N2 atmosphere.

Reference example 2 Gas flow rate ratio is A r / C H i, - 9 /
Te 88Cr was prepared in the same manner as in Example 1 except that
, C, H7, a recording film having a film thickness of 220 mm was obtained on a non-quality polyolefin substrate, and the recording medium (recording film) was heat-treated in the same manner as in Examples 4-6.

[Test results] (1) Rotate the disk at 1800 r and generate 3.7 Mll
The recording characteristics were examined by irradiating laser light at a frequency of z.

Here, C/Nmax is the C when changing the laser power.
/N ratio maximum value. Recording sensitivity is C/N>C/N I
laxXO. 9, and the margin represents the range of laser power where C/N>C/Nmax X0.9. The results are shown in Table 1.

Table 1 (2) Table 2 shows the test results when the reflection f$R was compared with the initial reflectance Ro after being left in an environment with a temperature of 70° C. and a relative humidity of 85% for 500 hours.

table 2

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an optical recording medium according to an embodiment of the present invention, and FIGS. 2 and 3 are graphs showing differences in function and effect between the optical recording medium according to the present invention and a conventional optical recording medium. FIG. 4 is a schematic cross-sectional view of an optical recording medium according to another embodiment of the present invention.

Claims (1)

[Scope of Claims] 1) Consisting of a substrate and a recording film formed on the substrate, the recording film is irradiated with an energy beam to form pits in the recording film and record information. In the optical recording medium made of On the other hand, an optical recording medium characterized in that Cr is in the range of 0.1 to 40 atomic % and C is in the range of 5 to 40 atomic %. 2) In an optical recording medium consisting of a substrate and a recording film formed on the substrate, information is recorded by forming pits in the recording film by irradiating the recording film with an energy beam. , the recording film is a thin film containing Te as a main component and Cr, C, and H, and the content ratio of Cr contained in the recording film is greater than the Te and C in the recording film.
The content ratio of C contained in the recording film is in the range of 0.1 to 60 at% with respect to the total number of atoms of r, 5-40
An optical recording medium characterized by being in the atomic percent range. 3) A method for manufacturing an optical recording medium, which comprises forming the recording film according to claim 1 or 2 on the substrate and then subjecting the recording film to heat treatment. 4) The method for manufacturing an optical recording medium according to claim 3, wherein the heat treatment is performed at a temperature of 70 to 300°C for 5 seconds or more.