JPH02310833A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium which can reproduce informa tion with high reflectance by using GeTe material for the optical recording film of specified thickness and laminating a dielectric film and a reflecting film thereon. CONSTITUTION:A polycarbonate resin substrate is used as a transparent sub strate 1, on which zinc sulfide (ZnS) dielectric film 2, GeTe optical recording film 3, ZnS dielectric film 4 and gold (Au) reflecting film 5 are successively formed. In this case, Ge-Te material is used for the optical recording film and made 5 - 15 nm thick. Thereby, no large facility is needed for reproducing information which is optically recorded in the medium.

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.

[Conventional technology]

Optical discs, which are one type of optical information recording medium, can be divided into read-only optical discs and recordable optical discs.

A read-only optical disk is one in which fine irregularities are formed on a transparent substrate by a method such as injection molding using a metal master disc as a mold, and a reflective film is coated on the disc.

This method requires the following steps: coating a glass disk with a photosensitizer, recording information using a laser beam, developing, electroplating, preparing a metal master, injection molding 1 forming a reflective film, and applying a protective film. Since this method requires a large amount of cost, it is suitable for mass production of a small number of products. However, it is not suitable for small-scale production of optical discs, and in this case, one optical disc becomes expensive.

One possible method suitable for small-scale production is to use a recordable optical disc. Conventionally, as in Kochi, information was recorded by irradiating an optical recording film provided on a transparent substrate with semiconductor laser light to make holes, or by causing a crystal phase transition. Information can be reproduced. When a recordable optical disc is used in this manner, it is possible to manufacture a read-only optical disc at low cost without the need to produce a metal master disc.

However, the reflectance of read-only optical discs made using this method is less than 50%, and cannot meet the standard for general read-only optical discs, which require a reflectance of 70% or more. It cannot be played on a playback-only optical disc playback device such as an LD player or a CD player.

In order to solve this problem, Japanese Patent Laid-Open Publication No. 1983-1999 was proposed as a method for inexpensively producing small-scale optical discs with the same performance as commercially available read-only optical discs, and producing optical discs that can be played on commercially available read-only optical disc players. 119755 is shown.

This involves forming an organic dye recording film that absorbs the recording light beam on a transparent substrate, irradiating it with a light beam, making holes called pits in the recording film to record information, and then exposing the recording film to the light beam. A recording medium with sufficient reflectance can be obtained by adding a process to make the medium transparent and then coating it with a reflective film.

However, in order to make the optical recording film transparent after recording information and then cover it with a reflective film, it is necessary to
This has the drawback of requiring special equipment and complicating the manufacturing process. Therefore, general users who do not have such equipment have the problem of not being able to play back immediately after recording.

[Problem to be solved by the invention]

The present invention solves the above-mentioned drawbacks and provides an optical information recording medium that can reproduce information without the need for special operations using a large-scale device after recording information with a light beam, and has a high reflectance. It was done for that purpose.

[Means to solve the problem]

The optical information recording medium according to the present invention has a transparent dielectric film, an optical recording film, a transparent dielectric film 2 and a reflective film laminated in sequence on a transparent substrate,
The optical recording film is characterized by using a germanium telluride (GeTe) based material and having a thickness of 5 to 15 nm.

[Effect]

The GeTe thin film has a complex refractive index n in the untreated state after film formation.
0 is the wavelength λ=78 (in Lrv no=4°2-0.
7i, so if the film thickness is 5 to 15n111 and the thin film, dielectric film, and reflective film are laminated on a transparent substrate, optical information with a reflectance of 70% or more for a light beam of wavelength λ = 780 nm incident from the transparent substrate side is obtained. A recording medium can be obtained. G
When the eTe film is heated to a temperature of 170° or higher, it undergoes a phase transition from an amorphous phase to a crystalline phase, resulting in a complex refractive index n,
Since n is 5.4-2.4i, the above reflectance is 7.
The reflectance of an optical information recording medium of 0% or more can be 28% or less. That is, the optical information recording medium according to the present invention is
Information can be recorded simply by irradiating a light beam to heat the GeTe optical recording film to cause a phase transition, and moreover, the reflectance of the optical information recording medium at that time is 70% or more in the area where no information is recorded. Since the information recording section can reduce the amount to 28% or less, the information can be reproduced without requiring any operation after the information is recorded. Further, the reflectance of the optical information recording medium according to the present invention has sufficiently satisfactory performance as a read-only optical disc.

(Example) In Fig. 1, a polycarbonate resin substrate is used as the transparent substrate l in Fig. 0 showing an embodiment of the optical information recording medium according to the present invention. Magnetized using zinc (ZnS)
Dielectric film 2. GeTe optical recording film 3. ZnS dielectric film 4.
Gold (Au) reflective films 5 each having a film thickness of 80 nm; 5.
The layers were sequentially stacked as 5n top, 200n+, and 100n top.

The reflectance of the optical information recording medium thus prepared is 72 for a light beam of wavelength λ=780 nm incident on the substrate side.
%Met. After recording information by irradiating this medium with a semi-enveloped laser beam with a wavelength λ = 780 nm, the reflectance of the information recording section at a wavelength λ = 780 nm was measured.
%, and both the reflectance before and after recording had performance as a read-only optical disc.

In this example, a ZnS film was used as the dielectric film, but the present invention also uses other dielectric films such as SiO, S fog, etc.
, Oxides such as Tax Ox, A/N.

Nitride such as Si3N4, Sbz S, GeS, Ge5
Chalcogenides such as e, Mg F'z * Ca F
It can be used as long as it is transparent at the wavelength of the reproduction light beam, such as fluorides such as Z.

As a transparent dielectric film, GeSe film, AI! An example using an N film will be explained. GeSe film, GeTe film, An! The thickness of each of the N film and Au film was 65 nm, 1 Onm.

230rv and 100nm, and were sequentially laminated. Wavelength λ of light incident on the substrate side of the optical information recording medium according to this embodiment =
The reflectance of the 780n* light beam is 71% in the area where information is not recorded.
The reflectance of the information recording portion was 27%, and it had the performance as a read-only optical disc.

In the above embodiments, a GeTe film was used as the optical recording film, but in the present invention, GeTe1f! Ge-5n-Te film or Ge-P in which part of GeTe is replaced with Sn or PB
b-Te film, GeTe-3bZSe3 alloy film, Ge
T e -S b z S e z alloy film.

Similar effects can be obtained by using a GeTe-based film such as a Ge-Te-3e film.

Further, in this example, the reflective film is made of Au, because it has the highest reflectance at the wavelength λ=780 nm. Even if Ag, Cu, or AJ is used in addition to Au, it is possible to obtain an optical information recording medium with a reflectance of 70% or more before recording and 28% or less after recording, but the reflectance of the reflective film at λ=78On- As the value decreases, the appropriate thickness range of the GeTe-based optical recording film becomes smaller.

〔Effect of the invention〕

In the present invention, a GeTe-based material is used as the optical recording film, the film thickness is 5r++s to 15ns, and the dielectric film 9 reflective film is laminated, so that the reflectance of the unrecorded area is 70% or more and the reflectance of the recorded area is 28%. % or less, and after information has been optically recorded, it can be reproduced without the need for particularly large-scale equipment.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of an optical disc according to the present invention.

Claims (1)

[Claims] Comprising a transparent substrate, an optical recording film, a transparent dielectric film and a reflective film,
A transparent dielectric film, an optical recording film, a transparent dielectric film, and a reflective film are sequentially laminated on a transparent substrate, a germanium telluride (GeTe)-based material is used as the optical recording film, and the thickness of the optical recording film is 5 to 5. An optical information recording medium characterized by having a wavelength of 15 nm.