JPH01124127A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To prevent the oxidation corrosion of a thin optical recording film initiated from a protective film side and to exactly record and reproduce information over a long period of time even after resting in high-temp. and high-humidity environment by setting the content of Au on the protective film side larger than the average content of Au within the optical recording film. CONSTITUTION:The thin recording film is formed as a thin film 12 essentially consisting of a Ge-Te material added with the Au. The content of the Au in the thin optical recording film is set smaller than the average content of the Au on a substrate 11 side and larger than the average content of the Au on the protective film 13 side. The oxidation corrosion in the high-temp. and high-humidity environment of the thin optical recording film starts from the protective film side and spreads gradually toward the substrate side. The content of the Au in the thin optical recording film is, therefore, set larger than the average content of the Au on the protective film side. The oxidation corrosion of the thin optical recording film which progresses from the protective film side is thereby powerfully prevented. Since the recording and reproducing characteristics depend strongly on the substrate-side properties of the thin optical recording film, the recording and reproducing characteristics are satisfactorily maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical information recording medium on which information is recorded and reproduced using a light beam.

(Prior art) Germanium telluride, germanium telluride substituted with tin or lead, kermanium tin telluride, and germanium lead telluride.

germanium tin lead telluride (hereinafter these materials will be referred to as Ge-
A Te-based material) is a suitable material as an optical recording material because it has high recording sensitivity and can increase the signal-to-noise ratio of a reproduced signal.

Now, optical information recording media are often used for the purpose of long-term storage of data, and it is necessary that the recording material does not change even if left in high-temperature, high-humidity, hyperopic conditions, and that recorded data can be read and written accurately. be.

With regard to this point, Ge--Te based materials have a phenomenon in which the thin film is gradually oxidized and corroded under hyperopic conditions of high temperature and humidity, resulting in changes in optical properties such as reflectance and transmittance. That is, Ge--Te based materials consist of crystals with a rhombohedral structure, but because the difference in atomic radius between Ge and Te is large, there are gaps in the crystal lattice through which other atoms can penetrate.

When a Ge-Te based thin film is placed under hyperopic conditions of high temperature and high humidity, oxygen atoms enter these gaps, forming Ge-Ge, Ge
-Te, cutting the Te-Te bond, G602. Te
02 to gradually oxidize the thin film.

For this reason, in the past, inorganic thin films such as oxides and nitrides were coated on Ge-Te-based thin films to serve as protective films to prevent the Ge-Te-based thin films from deteriorating under high-temperature, high-humidity conditions. There are disadvantages in that it takes a long time to produce the protective film, complicates the process for producing the optical information recording medium, and increases the cost of producing the medium.

The present applicant has solved these drawbacks and provided an optical information recording medium that can accurately record and reproduce information even when left in a high temperature, high humidity environment. A recording thin film made of this material was proposed as a patent application entitled "Optical Information Recording Medium (3)" dated October 28, 1986. Like this,
In Ge-Te based thin films doped with Au, A
Since the gaps in the Ge-Te crystal are filled in advance by u, it is difficult for oxygen to enter, and therefore, GeT
The e-based thin film is protected from deterioration due to the intrusion of oxygen, and its properties as a recording material do not change even if it is left in a high-temperature, high-humidity environment for a long period of time.

(Problems to be Solved by the Invention) However, although the optical information recording medium using the above-mentioned Au-doped Ge-Te based thin film as an optical recording film has a longer lifespan, it gradually deteriorates when the Au content becomes greater than 3 atomic percent. There was a problem in that the recording and reproducing characteristics deteriorated, and if the Au content exceeded 6 atomic percent, it was difficult to obtain reliable performance as an optical information recording medium.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides the recording thin film with:
The Ge--Te system material to which Au is added has a larger Au content than the average Au content on the main protective film side. (Operation) The operation of this means will be explained below. In general, oxidative corrosion of optical information recording media consisting of an optical recording thin film formed on a substrate and a protective film formed on the optical recording thin film under high temperature, high humidity, and far-view conditions starts from the protective film side and gradually moves toward the substrate side. It spreads.

Therefore, as in the present invention, by making the Au content in the optical recording thin film smaller than the average Au content on the substrate side and larger than the average Au content on the protective film side, it is possible to increase the Au content from the protective film side. Oxidative corrosion of optical recording thin films can be strongly prevented. Furthermore, recording and reproduction of information (Song dynasty) is normally performed by entering a light beam from the substrate side, and the recording and reproduction characteristics of an optical information recording medium strongly depend on the properties of the substrate side of the optical recording thin film. Thus, if the Au content on the substrate side of the optical recording thin film is smaller than the average Au content, good recording and reproducing characteristics can be maintained.

(Embodiment) FIG. 1 shows an embodiment of an optical information recording medium according to the present invention. That is, reference numeral 11 is a polycarbonate substrate, on which is a Ge doped with Au as an optical recording thin film.
-Te-based thin film 12 is included. Further, a resin wire retainer @13 was laminated on the optical recording thin film to prevent scratches and dust.

Here, the substrate 11 is not limited to polycarbonate; transparent resin plates such as PMMA, polyolefin, epoxy, etc., and glass plates can be used as known in the art.

The optical recording thin film 12 is produced by a sputtering method iA or a vapor deposition method. A method of making the Au content smaller than the average Au content on the substrate side and larger than the average Au content on the protective film side in the Au-added Ge-Te based thin film will be described below.

FIG. 2 is a schematic diagram of a sputtering apparatus used when producing the optical recording thin film. The polycarbonate substrate 11 is attached to the bottom surface of the rotary substrate support table 22 provided at the upper part of the vacuum chamber 21, and the vacuum chamber 21 is arranged in an approximately 5×1
After evacuation to 0''''Pa, an inert gas such as Ar is introduced into the vacuum chamber 21 to bring the gas pressure to 5×10-'Pa. In this state, when high-frequency power is applied to the Ge-Te-based material target 23 and the Au target 24 at the same time,
A Ge--Te based thin film doped with Au is formed on the substrate 11 by the sputtering action. At this time, the third
As shown in the figure, the high frequency power applied to the target 23 made of Ge-Te based material is kept constant, the power applied to the Au target 24 is reduced at the beginning of sputtering,
When increasing near the end, Au-doped Ge-
In Te-based thin films, the Au content is on average A on the substrate side.
It is smaller than the U content, and larger than the average Au content on the protective film side.

Similarly, in the vacuum evaporation method, Ge-Te based materials and Au
In simultaneous evaporation from two types of evaporation sources, the evaporation rate of the Ge-Te system material is kept constant, and the evaporation rate of Au is decreased at the beginning of the deposition and increased near the end, the Au content increases. It is smaller than the average Au content on the side of the protective film, and larger than the average Au content on the side of the protective film.

The resin protective film 13 is formed by applying an ultraviolet curable resin liquid using a spinner, and then irradiating ultraviolet rays to cure the resin and form a film. For the resin protective film 13, not only an ultraviolet curable resin but also a moisture curable resin, a two-component reactive resin, and a solvent-based resin can be used.

An optical information recording medium for comparison was prepared by keeping the power applied to the Au target constant during the fabrication of the Au-doped Ge-Te based optical recording thin film, and the power applied to the Au target during sputtering as shown in Figure 3. The Au content of the optical information recording medium according to an embodiment of the present invention, the life of the optical information recording medium, and the signal-to-noise ratio ONR of the reproduced signal were changed to
A comparison is shown in the table.

Table 1 Here, the media life is measured by irradiating a disk-shaped optical information recording medium with a laser beam, recording a signal at a rotation speed of 180 Orpm and a frequency of IMHz, and performing a temperature-humidity accelerated test according to JIS 05024M-1, and determining whether the bit error rate is within the range. This is the media life estimated from the test time, which is three times the value before the test.

As shown in Table 1, according to the above example, the optical information recording medium has an optical recording thin film in which the Au content is smaller than the average Au content on the substrate side and lower than the average Au content on the protective film side. Since it is large, the medium life is long, and the reproduction signal CNR maintains a good value.

(Effects of the Invention) According to the present invention, in the optical recording thin film, since the Au content is larger than the average Au content on the protective film side, oxidative corrosion of the optical recording thin film starting from the protective film side can be prevented. It is possible to obtain an optical information recording medium that can prevent the above problems and accurately record and reproduce information for a long time even when left under high temperature, high humidity, and hyperopia. Furthermore, since the Au content on the substrate side of the optical recording thin film is smaller than the average Au content, the deterioration of the recording and reproducing characteristics due to the addition of Au is small, and an optical information recording medium with good recording and reproducing characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of an optical information recording medium according to the present invention, FIG. 2 is a schematic diagram of a sputtering apparatus applicable to the present invention, and FIG. 3 is a diagram for explaining its operation. 11...Substrate 12...Optical recording thin film 13...Resin protective film 21...Vacuum chamber 22...Substrate support table 23...Ge-Te target 24...Au target Patent applicant Nippon Columbia Co., Ltd. l1vl(lbBj'
f/l) Hand 3 Iε Dispute Authorization (Spontaneous) Indication of 18 Cases 1988 Patent Application No. 280931 2, Name of Invention Optical Information Recording Medium 3, Person Making Amendment Relationship with Case Address of Patent Applicant Postal code 107 4-14-1 Akasaka, Minato-ku, Tokyo
No. 4 Name (416) Representative Director of Nippon Columbia Co., Ltd. Kazuo Mochizuki 4, Agent Address: 5-1 Minato-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture, Postal Code: 210 Showa Year, Month, Day (Date of Shipping): 6, Subject of Amendment: 71, (Sa r-1) In an optical information recording medium consisting of a protective film formed on a tQ concave film of water, the main component of the optical recording thin film is Ge with 1 Au added.
- An optical information recording medium characterized in that it is made of a Te-based material and the Au content in the optical recording thin film is smaller than the average Au content on the substrate side. , Q-'US, knee? :,)

Claims (1)

[Claims] In an optical information recording medium comprising an optical recording thin film formed on a substrate and a protective film formed on the optical recording thin film, the main component of the optical recording thin film is a Ge-Te based material doped with Au, An optical information recording medium characterized in that the Au content in the optical recording thin film is greater than the average Au content on the substrate side.