JPH02289932A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium having good recording sensitivity by a simple method by providing recording films having the two-layered structure formed by a high-frequency sputtering method and a DC sputtering method. CONSTITUTION:This recording medium is constituted of two layers of the recording films consisting of the recording layer (1st recording layer) formed by the high-frequency sputtering method on a substrate and further, the recording layer (2nd recording layer) formed by the DC sputtering method thereon. The media having the enhanced sensitivity are mainly the media which are provided with the state change at the boundary between the substrate and the recording film. Namely, the recording film is stuck at the boundary between the substrate and the recording film by the high-frequency sputtering method advantageous for enhancing the sensitivity and thereafter, the film is formed by the DC sputtering method advantageous for the film forming speed and the uniformity of the film. The recording medium having the high productivity and characteristics is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium on which information can be recorded and reproduced using laser light.

[Conventional technology and its problems]

Conventionally, low melting point metals such as Te and Bi, and their alloy compounds or Dispersions thereof have been used.

Among these, Te-Se alloy is a typical material used in recording media of the so-called punching type recording method, in which recording is performed by forming pits by laser beam irradiation, and has high recording sensitivity.
It has also been known as a recording material with excellent oxidation resistance, long-term storage, and high practical value.

However, in applications such as computer databases that require high-speed writing to recording media, conventional media do not reach the required performance in terms of recording sensitivity, and various attempts have been made to improve the recording sensitivity of the media. It has been.

For example, in the case of perforated recording media, a proposal is to provide an additional layer of material between the substrate and the recording film that is decomposed by the light energy applied to the recording film, thereby promoting the formation of holes in the recording film. is disclosed in Japanese Patent Application Laid-Open No. 58-166548.

However, these known examples have a problem in that the substrate is deformed by the light energy irradiated during reproduction, and the C/N ratio of the recorded signal gradually decreases when repeated reproduction is performed. Furthermore, the layer between the substrate and the recording film is a layer formed of a material different from that of the recording film, and when the recording film is formed in a vacuum chamber, another process device, such as a spinner coating, is required to form the underlayer. There are also problems in that a device is required or, if the underlayer is formed by a sputtering method, a target layer for the underlayer components is required.

According to research conducted by the present inventors, when forming a recording film on a substrate, a recording film formed by sputtering using a high frequency sputtering method has better recording sensitivity than a recording film formed by a direct current sputtering method. However, the high frequency sputtering method has problems such as a slower film formation rate and difficulty in controlling the film thickness than the direct current sputtering method.

[Means to solve the problem]

The present inventors have studied various ways to create a highly sensitive optical information recording medium that does not reduce the C/N ratio due to optical energy during reproduction and that is as simple as possible. The present inventors have discovered that the above object can be achieved by providing a recording layer thereon by a high frequency sputtering method, and further providing a recording layer thereon by a DC sputtering method, and have completed the present invention.

That is, in the present invention, a recording layer (hereinafter this recording layer will be referred to as a first recording layer) is formed on a substrate by a high frequency sputtering method, and a recording layer (hereinafter this recording layer will be referred to as a second recording layer) is formed on the substrate by a DC sputtering method. The present invention provides an optical information recording medium characterized in that it is constituted by a two-layer recording film.

The mainstream of high-sensitivity media is one that causes a state change at the substrate-recording film interface, and the present invention also belongs to the category that adopts this method. That is, according to the present invention, the recording film is deposited at the substrate-recording film interface by high-frequency sputtering, which is advantageous for increasing sensitivity, and then by the DC sputtering method, which is advantageous for film-forming speed and film uniformity. By this, a recording medium with high productivity and characteristics can be obtained.

The constituent elements of the recording film of the optical information recording medium of the present invention are metal-based elements that have good absorption of laser light and have a low melting point. Applicable. Further, the elements constituting the first recording layer and the second recording layer may be the same or different.

As the recording material of the write-once optical information recording medium, Te-based alloys such as Te-Se, Te-^s, Te-Sb, T
e-1r++ Te-Sr++ Te-Pb, Te-
Bit Te-Se-TiTe-Se-Pb Te-
Se-Sb, Te-Se-In, Te-Se-Bi
, Te-Se-Ti-Ag and Te dispersion, e.g.
TeC+Te-CSz, TeaX, etc. can be mentioned.

The recording material for the rewritable optical information recording medium is T.
e-based alloys, such as Te-0-Sn-GeSn-
Te-Se, In-Sb-Te, Ga-Te-S
e, Ge-Te, etc., and other phase change alloys, e.g.
In-Sb, In-Sb-Se, Si-Sn,
Examples include Ge-Sn, Cu-AI+, and 8g-Zn.

Among the above-mentioned recording materials, a thin film containing Te of a Te-based alloy is preferable, and in particular, a thin film containing Te and Se as main components, Ti + 8g
+cr+8], at least one element selected from the group consisting of Sb, Pb, As, In, Ga, Ge, and Cu.
Thin films containing more than one species are preferred.

The thickness of the first recording layer and the second recording layer of the recording medium of the present invention varies depending on the use, but in order to obtain a good CZN ratio and provide a practical recording discrepancy, the thickness of each layer should be 1.
It is preferable that the total thickness of the first recording layer and the second recording layer is in the range of 0 to 1000.
The thickness of the first recording layer is preferably in the range of 10 to 200 people.

As the substrate material used in the present invention, glass or plastics such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin can be used.

(Examples) The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A target made of Te-Se-Ti-Ag was deposited on a polycarbonate resin spiral grooved disk substrate with a diameter of 1.30 arms by high-frequency sputtering method (Ar pressure ~ 0).
．． 5Pa, high frequency power 200W) with a thickness of 150 people.
A recording layer was formed, and a DC sputtering method (Ar pressure ~ 0.5 Pa, DC power 7) was applied using the same targen 1.
A second recording layer was formed to a thickness of 150 layers at a temperature of 0.0 mm) to obtain a recording medium.

This recording medium was heated to a frequency of 5.8 MIIz. using an 830 nm semiconductor laser. 1 repetition signal with duty 30%
Under the condition of 80 rpm, writing was performed at a position of 120 mm of lZl while changing the laser output, and reading was performed at a distance of 1 m to measure the recording sensitivity and C/N ratio.

The recording sensitivity was evaluated by observing the recording laser output when the C/N ratio reached 45 dB.

The results are shown in Table-1.

Comparative Example 1 Using the same target on the same disk substrate as in Example 1, a recording film with a thickness of 300 mm was formed using only the DC sputtering method (Ar pressure ~0.5 Pa, DC power 70 W), and a recording film was formed on the recording medium. I got it.

The recording sensitivity and C/N ratio of this recording medium were measured in the same manner as in Example 1.

The results are shown in Table-1.

Keiji, Ama The optical information recording medium having a two-layer structure recording film formed by high-frequency sputtering method and DC sputtering method in Example I is different from the conventional single-layer structure optical information recording medium used in Comparative Example 1. It can be seen that the recording sensitivity has increased.

〔Effect of the invention〕

According to the present invention, an optical information recording medium with good recording sensitivity can be obtained by a simple method.

Claims (1)

[Claims] 1. A recording layer (
A two-layer recording film is formed by forming a recording layer (hereinafter referred to as the first recording layer) and further forming a recording layer (hereinafter this recording layer will be referred to as the second recording layer) by direct current sputtering. An optical information recording medium comprising: 2. The constituent elements of the first or second recording layer are mainly composed of Te and Se, and include Ti, Ag, Cr, Al, Sb, Pb, and A.
2. The optical information recording medium according to claim 1, wherein the optical information recording medium contains at least one element selected from the group consisting of S, In, Ga, Ge, and Cu.