JPS62245545A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable reproduction of an information signal by a reproducing device for a compact disk by providing the 2nd metallic film which forms an alloy of high reflectivity with the 1st metal to reproducing light onto the 1st metallic film having low reflectivity to recording light. CONSTITUTION:A thin zinc film is stuck and formed as the metallic film 2 onto the substrate 1 made of an acrylic sheet and thereafter, a thin copper film is stuck and formed as the metallic film 3 on the film 2. A thin zinc film constituting the film 2 is heated up to alloy the zinc of the film 2 and the copper of the film 3 when the spot of laser light is focused to the film 2 by projecting a laser light beam of 780nm wavelength thereon from the substrate 1 side. The recording layer of the part irradiated with the laser light is then discolored to a golden color and the reflectivity to 780nm wavelength is increased to 85%. The reproduction of the information signal is thus executed by using the reproducing device for the compact disk.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an information recording medium.

(Conventional technology vR) As the demand for recording various information signals at high recording densities has increased, in recent years, information recording media created based on various structural and operating principles have been used to record information. It is well known that high-density recording and reproduction of signals has become possible. Recording and reproducing devices that reproduce information signals by optical means or by detecting changes in capacitance values are already in practical use for recording and reproducing video and audio signals. In addition, in order to meet the demands for high-density recording and reproduction in various technical fields, information signals can be transmitted to the recording layer of an information recording medium by irradiating the recording layer of the information recording medium with a recording beam whose intensity is modulated by the information signal. Research has also begun on information recording media that record information signals by causing physical or chemical changes in response to As the technology has become more widely available, various types of optical discs that use laser light for high-density recording and playback have already been put into practical use, or research and development is currently underway to put them into practical use. As is well known.

In other words, recorded optical discs (playback-only optical discs) that have been copied in large numbers from master discs on which information signals are recorded using bits formed as geometrical concave or convex parts are, for example, video discs, compact discs, etc. In addition, optical discs that can be added and recorded only once by the user (write-once optical discs) and erasable optical discs are being put into practical use for office file memory and other uses. Active research and development is being carried out for this purpose, and up until now, even write-once optical discs and erasable optical discs have had their recording layers exposed to various physical phenomena due to the heating action of the laser beam spot. When classified based on whether the information signal is recorded by a change in Various formats have been proposed, such as thermal transformation type (which causes changes in rate, etc.), as well as information recording media in which recording and reproducing operations are performed using energy outside the tip. Many proposals have also been made.

In the various types of information recording media described above, when the recording layer is irradiated with intensity-modulated light or other recording beam, the light reflectance of the recording layer in the portion irradiated by the recording beam is However, most of them are equipped with a recording layer having a property that the reflectance of light is higher than that of the portion not irradiated with the recording beam.

By the way, when reproducing information signals from an information recording medium on which information signals are recorded at high density, tracking control is used to ensure that the reproducing element or the reproducing beam always accurately follows the recording trace where the information signals are recorded. For example, a spot of light with a minute diameter is projected onto the signal surface of an information recording medium,
As a tracking error detection method used for tracking control in an optical information signal reproducing device that reproduces an information signal based on reflected light whose intensity is modulated by bits formed on the signal surface, there is a tracking error detection method that is used for tracking control from an information recording medium. The so-called push-pull tracking error detection method uses the fact that the intensity distribution of the reflected light is biased by the tracking error to detect the tracking error, but the optical system has a simple configuration. In addition to this, it is widely used because it is advantageous in terms of cost.In addition, it projects a first light spot for signal reading onto the signal surface of an information recording medium, and the first light spot described above is also used. On a straight line including the light spots, second and third light spots for tracking are projected at symmetrical positions with the first light spot as the center of symmetry, and the second and third light spots for tracking are projected at symmetrical positions with the first light spot as the center of symmetry. It is well known that a tracking error detection method that detects a tracking error based on the reflected light generated on the signal surface of the information recording medium by the third light spot has also been used. Even when reproducing information IF numbers recorded at high density on various types of information recording media, the reproduction operation is normally performed under tracking control operation, and the reproduction operation is normally performed under tracking control operation. When the information signal is reproduced optically, the tracking control operation is performed using a tracking control signal generated based on a tracking error signal detected by the various tracking error detection methods described above, for example. be.

Now, a compact disc is known as an information recording medium in which information signals are recorded at high density on the signal surface of the medium by an array of bits corresponding to the information signals. An information signal is recorded on the signal surface by an array of bits with a depth set in a specific relationship with respect to the signal surface, and the entire surface of the signal surface is covered with a thin film of aluminum. It is specified that the reflectance of the land portion on the signal surface for light with a wavelength of 780 nm is 70% to 90%, and the readout of information signals from the signal surface of the information recording medium is I try to do this using spots of light.

When reading an information signal from the compact disc described above, the amount of light reflected from the pit portion on the signal surface of the compact disk is greater than the amount of reflected light from the land portion as a result of light interference occurring at the pit portion. Tracking error information is also obtained by using the difference between the amount of reflected light from the recorded trace area and the amount of reflected light from the land area. It is being done.

A compact disc has an information signal recorded on the signal surface of the information recording medium by an array of pits according to the information signal, and an aluminum reflective film is coated on the entire signal surface. The reflectance of light is the highest in the part of the pit caused by the information signal, and the reflectance of light is the lowest in the pit part due to the information signal, and most of the write-once information recording media and erasable information recording media are When the recording layer is irradiated with intensity-modulated light or other recording beam, the light reflectance of the portion of the recording layer irradiated by the recording beam is the same as that of the portion not irradiated by the recording beam. As mentioned above, it is equipped with a recording layer that has a property that the reflectance of light is higher than that of light, but the compact disc described above, the write-once type information recording medium described above, and the information that is prone to erasing. For most information recording media, the light reflectance of the land portion is the highest in the former, while it is the lowest in the latter, which is an opposite relationship. ing.

For this reason, when playing most of the above-mentioned write-once information recording media and erasable information recording media,
Generally available compact disc playback devices cannot be used as is.

When the recording layer is irradiated with intensity-modulated light or other recording beam, the reflectance of the light of the recording layer in the area irradiated by the recording beam is determined by the applicant's company Debo. By creating a special recording mode for an information recording medium that has a recording layer that has a property that the reflectance of light is higher than that of the areas that are not exposed to light, it is possible to use a generally popular compact disc playback device as it is. A recording method for information signals that can be used to obtain a recorded recording medium in a state in which the information signal can be reproduced, that is, a recording method in which the intensity is modulated by the information signal being recorded. A recording beam that forms a recording trace of the information signal on the information recording medium by the beam, and that is also non-modulated on the portion between adjacent recording traces of the information signal on the information recording medium. We proposed a method for recording information signals by irradiating light.

(Problem to be Solved by the Invention) However, as an information recording medium that can reproduce information signals by using a compact disc playback device as is, it is difficult to use the light reflectance specified for compact discs. It must have a reflectance that satisfies the standard value (light reflectance of 70% to 90% for light with a wavelength of 780 nm), but information recording media that originally have a high light reflectance On the other hand, when information signals are recorded, the light reflectivity of the information recording medium is high, so even if light is projected onto the recording layer of the information recording medium when recording information signals, the light The problem is that because of the high reflectivity of the recording layer, the amount of energy absorbed by the recording layer is small, and therefore a light beam with high energy is required during recording.

(Means for Solving the Problems) The present invention provides that the recording layer before the recording beam of the information signal is projected has a low reflectance to the light used for recording the information signal, and that A recording medium in which the light reflectivity of the recording layer is extremely high, that is, a substrate that is transparent to the light used for recording the information signal, and a substrate that is transparent to the light used for recording the information signal. A first metal film having a low reflectance is provided on the first metal film, and a film is formed between the first metal film and the metal constituting the first metal film to reflect light used during reproduction. The present invention provides an information recording medium comprising a 20th metal film that can be made into an alloy that exhibits high reflectance.

(Example) Hereinafter, detailed contents of the information recording medium of the present invention will be specifically explained with reference to the accompanying drawings. The attached drawing is a partially enlarged cross-sectional view of one embodiment of the information recording medium of the present invention. In the figure, 1 is a substrate of the information recording medium, and this substrate 1 is connected to light used for recording information signals. It is made using a transparent material. In the following explanation example, it is assumed that an acrylic plate (or a glass plate) is used as the substrate 1.

The above-described substrate 1 is provided with the first metal film 2 that exhibits a low reflectance for light used for recording information signals, and the above-described first metal film 2 is provided with the above-described first metal film 2. A second metal film is formed such that an alloy exhibiting a high reflectance to light can be formed with the metal constituting the first metal film 2.

In carrying out the present invention, it is a desirable embodiment that the first metal film 2 formed on the substrate 1 is made of a thin film of zinc, and the second metal film is made of a thin film of copper. An acrylic plate was used as the substrate 1, and after a thin film of zinc with a thickness of about 200 angstroms was deposited as the first metal film 2 on the substrate 1 by vapor deposition or sputtering, a film composed of the above-mentioned thin film of zinc was formed. Regarding the information recording medium of the present invention, which is constructed by depositing a thin copper film with a thickness of about 300 angstroms as the second metal film 3 on the first metal film 2, the wavelength is When a 780 nm laser beam is projected and the spot of the laser beam is focused on the zinc thin film that makes up the first metal film 2, the light that makes up the first metal film 2 in the recording layer is Reflectance is 6
A thin film of 5% zinc is heated by a spot of laser light projected onto it, increasing its temperature and causing the first
Zinc constituting the metal film 2 and copper forming the second metal film 3 are alloyed, and the recording layer in the area irradiated with the laser beam changes color to golden yellow as described above. , the wavelength is 78
The light reflectance for 0nrn was 85%.

(Effects) As is clear from the detailed explanation above, the information recording medium of the present invention has a substrate that is transparent to the light used for recording the information signal, and a substrate that is transparent to the light used for recording the information signal. A first metal film exhibiting a low reflectance to the light used is provided, and the first metal film described above is provided on the first metal film described above.
This is an information recording medium comprising a second metal film that can form an alloy with the metal forming the metal film that exhibits a high reflectance to the light used during reproduction. This information recording medium uses a recording beam whose intensity is modulated by the information signal to be recorded to form a recording trace by the information signal, and also forms a recording trace by the information signal on the recording medium that is adjacent to the recording trace by the information signal. If unmodulated recording beam is irradiated to the area between the two discs, the information signal can be reproduced using a commonly used compact disc reproducing device as is. According to the present invention, the above-mentioned conventional problems (12-) can be satisfactorily solved.

[Brief explanation of drawings]

The accompanying drawing is a partially enlarged vertical cross-sectional view showing a schematic configuration of an embodiment of the information recording medium of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... First metal film, 3... Second metal film,

Claims (1)

[Claims] 1. On a substrate that is transparent to the light used for recording the information signal, a first substrate that exhibits a low reflectance for the light used for recording the information signal; Along with providing a metal film,
A second metal that can form an alloy with the metal constituting the first metal film on the first metal film that exhibits a high reflectance for light used during reproduction. Information recording medium 2 comprising a film, the information recording medium according to claim 1, wherein the first metal film is a thin film of zinc and the second metal film is a thin film of copper.