JPS62227790A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium simple in construction, easy to produce and having favorable recording sensitivity and a high S/N of reproduction signals, by sequentially providing first and second recording layers differing in laser light absorption characteristic and hue on a base. CONSTITUTION:First and second recording layers 2, 3 differing in laser light absorption characteristic and hue are sequentially provided on a base 1. To perform recording, this optical recording medium is irradiated with recording laser light 4 capable of being selectively absorbed by the first or second recording layer to melt the first or second layer and also melt the second or first recording layer not absorbing the laser light, thereby forming a record area 6 having a hue different from those of the first and second recording layers. To perform reproduction, the recording medium is irradiated with reproducing laser beam 7 which has a wavelength different from that of the recording laser beam and is not absorbed by the first and second recording layers but absorbed by the record area 6, and difference in, for example, laser light reflectance between the record area and the other areas is detected. This recording medium is easy to produce, and is capable of achieving a higher recording sensitivity and a higher S/N of reproduction signals.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is directed to a laser beam that records information by the thermal action of laser light, which has high recording sensitivity and a good S/N ratio of the reproduced signal. Regarding recording media.

(Prior art) Optical recording media that use laser light are capable of high-density and high-sensitivity recording, and with advances in semiconductor lasers,
Since it has become possible to obtain a small, low-cost device using this semiconductor laser as a recording/reproducing light source, its use as a large-capacity file memory is being considered.

By the way, the following types of optical recording media have been proposed so far.

One known example is one in which a phthalocyanine-based recording film is formed on a substrate. In this optical recording medium, recording is performed by irradiating the recording film with a pulse modulated laser beam corresponding to information and locally heating it to form recesses.

However, in the case of such an optical recording medium, it is unavoidable that the recording film scatters or builds up around the formed recesses. Therefore, it is difficult to improve the S/N ratio of the information reproduction signal.

On the other hand, there is also known an optical recording medium in which a recording film has convex portions instead of concave portions as described above. In an optical recording medium in which convex portions are formed on the recording film in this way, the above-mentioned scattering and build-up of the recording film do not occur, so
This is advantageous for improving the S/N ratio of the information reproduction signal.

For example, the optical recording medium described in JP-A-56-127937 has a non-energy-absorbing organic intermediate layer and an energy-absorbing layer formed on a substrate. In this optical recording medium, the energy absorption layer is irradiated with laser light to locally heat it, the organic intermediate layer is indirectly heated to generate gas, and this gas forms convex portions on the energy absorption layer to record information. will be carried out.

However, since this recording medium indirectly heats the organic intermediate layer as described above, there is a problem in that the recording sensitivity is low.

Furthermore, the optical recording medium described in JP-A-56-65341 has a metallic light-reflecting film, a non-energy-absorbing gas releasing layer, and a metallic energy-absorbing layer formed on a substrate. The difference in structure from the former is that a light reflecting film is provided between the substrate and the energy non-absorbing gas release layer. In this optical recording medium as well, recording is performed by forming convex portions on the energy absorbing layer in the same manner as in the former one.

In this optical recording medium, a light reflecting film is provided between the substrate and the non-energy-absorbing gas freeing layer, so it is expected that it will be able to use light more efficiently and improve recording sensitivity than the former. . However, in order to actually increase the efficiency of light use, it is necessary to strictly set the thickness of the energy absorbing layer and the non-energy absorbing gas freeing layer to a predetermined value, which poses manufacturing difficulties. .

(Problems to be Solved by the Invention) The present invention has been made to solve the above problems, and has a simple structure and is easy to manufacture, and has good recording sensitivity and a high S/N ratio of reproduced signals. The objective is to provide an optical recording medium with high performance.

[Structure of the Invention] (Means for Solving the Problems) The optical recording medium of the present invention is provided by sequentially laminating first and second recording layers having different laser light absorption characteristics and hues on a substrate. It is characterized by:

In the optical recording medium of the present invention, recording is performed by irradiating the first or second recording layer with a recording laser beam that is selectively absorbed, melting the first or second recording layer, and then applying the recording laser beam to the first or second recording layer. This is carried out by melting the non-absorbing second or first recording layer to form a recording area having a different hue from the first and second recording layers.

In addition, in the optical recording medium of the present invention, reproduction is performed using a recording laser that is not absorbed by the first and second recording layers but is absorbed by the recording area. This is done by irradiating a reproducing laser beam with a wavelength different from that of the light and detecting the difference in reflectance of the laser beam between the recording area and other areas.

(Function) According to the optical recording medium as described above, the first and second recording layers may be any material as long as a recording area having a different hue from the first and second recording layers is formed by the recording operation. For example, #14 can be formed by a vapor-deposited film of a dye or pigment, or a film coated with a dye or pigment dissolved or dispersed in a resin matrix. These films can be easily formed using dry processes such as vacuum evaporation or knitting processes such as spin-coding.
It is extremely easy to manufacture.

Furthermore, if the melting temperature of the second or first recording layer that does not absorb the recording laser beam is equal to or lower than the melting temperature of the first or second recording layer that absorbs the recording laser beam, ,
Recording can be performed using low-energy laser light, and high recording sensitivity can be achieved.

Furthermore, since the recording area is not made up of four parts, there is of course no scattering or build-up of the recording film, and the shape of the recording area is sharp because the organic material with low thermal conductivity is evaporated. Compared to the case where a convex portion is formed, the S/N ratio of the reproduced signal can be further improved.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

First, mirror polished diameter 12511111% thickness 1°2
Carmine BS, which is magenta, is placed on the glass substrate 1 of M.
A first recording layer 2 having a thickness of 14 was formed by spin coating a solution of polymethyl methacrylate in methyl isobutyl ketone. Note that the melting temperature of the first recording layer 2 is 180°C. Next, cyan-colored phthalocyanine blue was vacuum-deposited to form a second recording layer 3 having a thickness of 0.14 mm.

Note that the melting temperature of the second recording layer 3 is 250°C. An optical recording medium according to the present invention was manufactured in the following manner (as shown in FIG. 1).

Next, from the second recording layer 3 side, Ar laser light (wavelength 4
Recording was performed by focusing irradiation through lens 5 with 880 people, power 10 mW). As a result, the second recording layer 3 melts in the laser beam irradiation area, and the first recording layer 2, which has a lower melting temperature than the second recording layer 3, also melts, and has a purple hue due to subtractive color mixing. A recording area 6 was formed (as shown in FIG. 2).

Next, He-Ne laser light (wavelength 63
28 people, output 4 mW) was focused and irradiated through the lens 5, and reproduction was performed by detecting the difference in reflectance of the laser beam between the recording area 6 and other areas (as shown in Figure 3).
. As a result, the S/N ratio of the reproduced signal was 45 dB.

As described above, the optical recording medium according to the present invention can be easily manufactured, and can achieve high recording sensitivity and improvement in the S/N ratio of reproduced signals.

In the above embodiment, the laser beam absorbed by the upper second recording layer 3 of the first and second recording layers 2.3 formed by sequentially laminating on the substrate 1 is used as the recording laser beam 4. However, the present invention is not limited to this, and a laser beam absorbed by the lower first recording layer 2 may be used as the recording laser beam. However, in any case, it is desirable that the melting temperature of the recording layer that does not absorb the recording laser beam be equal to or lower than the melting temperature of the recording layer that absorbs the recording laser beam.

Further, in the above embodiment, the recording laser beam and the reproducing laser beam are irradiated from the second recording layer side, but the invention is not limited to this, and the recording and reproducing laser beams may be irradiated from the substrate side.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide an optical recording medium that is easy to manufacture and can achieve high recording sensitivity and improvement in the S/N ratio of reproduced signals. Its industrial value is extremely high.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an optical recording medium in an embodiment of the present invention;
FIG. 2 is a sectional view showing a recording method on the same optical recording medium, and FIG. 3 is a sectional view showing a reproducing method on the same optical recording medium. DESCRIPTION OF SYMBOLS 1... Substrate, 2... First recording layer, 3... Second recording layer, 4... Recording laser beam, 5... Lens, 6
... Recording area, 7... Laser light for reproduction.

Claims (5)

[Claims] (1) An optical recording medium characterized in that first and second recording layers having different laser light absorption characteristics and hues are sequentially laminated on a substrate. (2) A patent claim characterized in that the first and second recording layers are composed of vapor-deposited films of dyes or pigments, or films coated with dyes or pigments dissolved or dispersed in a resin matrix. The optical recording medium according to item 1. (3) Melting the first or second recording layer by irradiating the first or second recording layer with a recording laser beam that is selectively absorbed; and a second or first recording layer that does not absorb the recording laser beam; 2. The optical recording medium according to claim 1, wherein the recording layer is melted to form a recording area having a hue different from that of the first and second recording layers. (4) A patent characterized in that the melting temperature of the second or first recording layer that does not absorb recording laser light is lower than the melting temperature of the first or second recording layer that absorbs recording laser light. The optical recording medium according to claim 3. (5) Reproduction is performed by irradiating a reproduction laser beam with a wavelength different from that of the recording laser beam, which is absorbed by the recording area without being absorbed by the first and second recording layers. The optical recording medium according to item 3.