JPS5862096A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide an optical information recording medium capable of reproducing information by the interference between reflected light from a written part and that from a non-written part without requiring any developing process, by providing a substrate and a recording material layer in the manner that their reflectances for a laser beam used in reproduction are in a specified ratio. CONSTITUTION:The first high polymeric binder layer 2 containing a light absorber is formed on the substrate 1 as a recording layer, and the second high polymeric binder layer 3 not containing any light absorber is formed thereon to constitute the titled recording medium. In this case, the reflectance I1 of the substrate 1 the reflectance I2 of the recording material layer, for the laser beam source used in reproduction, are set to satisfy the relationship of 0.32<I2<I1< 2.0. When the medium is irradiated with the laser beam for recording, the first layer 2 generates heat, whereby both the first layer 2 and the second layer 3 are decomposed and evaporated, and a written bit as shown is formed, resulting in that the substrate 1 is exposed at the written part. At the time of reproduction, the signal is reproduced with a high degree of modulation by the interference between the reflected light from the second layer 3 and that from the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording carrier on which information is recorded and reproduced using a laser beam, and its purpose is to form a writing section and a non-contact recording medium without requiring a developing process. An object of the present invention is to provide an optical information recording carrier that can be reproduced by mutual interference of reflected light in a writing section.

Generally, when recording and reproducing information using laser light, a heat mode recording method is known in which information is recorded by evaporating or vaporizing the recording material using laser light, and this recording method is capable of high-density recording. This is advantageous in that it is possible.

The method of using a disk using a thin metal film such as mulch as a recording material for heat mode recording has already been applied to the production of a master plate for a video disk.

However, metal thin films generally have a high melting point and require a large-scale laser for recording, making them unsuitable for users to perform recording. On the other hand, Bi film,
Heat mode recording using a low melting point metal film such as a Te-based thin film or a low melting point metal film is advantageous in that recording power can be reduced, but there is a desire for something that can perform even lower power recording. . On the other hand, carbon black.

Thin films made by mixing nitrocellulose with a light absorber such as a dye are decomposed and vaporized at low temperatures, so the energy required for recording is extremely small, making them advantageous for heat mode recording. When information is recorded on these recording materials, the non-writing area is covered with a light absorber with low reflectance, and the writing area is covered with a light absorber, leaving the substrate exposed. Therefore, in order to obtain a high degree of modulation during reproduction, it is necessary to increase the reflectance of the substrate as much as possible.
Although it has been considered to form a thin film on the substrate, these methods have the drawback that the thin heat source and good conductivity promote thermal diffusion and increase the recording energy. In addition, in order to obtain a high degree of modulation, a method has been proposed that uses mutual interference between the light reflected in the writing section and the non-writing section, but in order to realize this method, a light absorber is required. Bleaching by exposure to ultraviolet light has the disadvantage of requiring a developing process.

The present invention has been made in order to eliminate these drawbacks, and there is a gap of 0.32 (I
2/II (This is a structure that satisfies the relationship 2,0. According to this structure, the reflectance of the written area and the non-written area are made equal and the reflectance is increased due to mutual interference without going through the development process. It has the advantage of being able to perform reproduction with a modulation degree.

The present invention will be described below with reference to drawings of embodiments. FIG. 1 shows an example of an optical information recording carrier according to the present invention. In FIG. The recording layer contains the first polymer binder layer 2! The first polymer binder layer 2 is further provided with a second polymer binder layer 3 made of a polymer binder containing no light absorber. When this record carrier is irradiated with a recording laser beam, part of the light is reflected at the interface between the second polymer binder layer 3 and air, and the remaining light is absorbed by the first polymer binder layer 2 after passing through. be done.

At that time, the first polymer binder layer 2 containing the light absorber generates heat, and when it reaches a certain temperature, the first polymer binder layer 2
．． The second polymer binder layer 3 decomposes and vaporizes, and the second polymer binder layer 3 decomposes and vaporizes.
The write bit shown in the figure is formed. As a result, the surface of the substrate 1 is exposed in the writing section. At this time, the first polymer binder layer 2. The total film thickness of the second polymer binder layer 3 is
(2n+1)λ/4 (n
: integer). Therefore, during reproduction, signal reproduction is performed with a high degree of modulation due to interference between part of the light reflected by the second polymer binder layer 3 and part of the light reflected by the substrate 1. I can do it.

FIG. 4 shows the change in the degree of modulation with respect to the ratio of the reproduction light reflection intensity factor 1 from the substrate surface to the reproduction light reflection intensity factor 2 from the recording material surface. From this figure, it can be seen that for the modulation degree in an ideal case where the reproduction light reflection intensities from both the substrate surface and the recording material surface are completely equal, 0.32 < I2/II (70 inches or more in the range of 2,0). It can be seen that the modulation degree can be obtained.

Specifically, a transparent acrylic substrate with an outer diameter of 120 mm was ultrasonically cleaned with ethyl alcohol for about 1 hour, and then dried by spinning with a high-speed spinner. . Next, the disk was held in a high-speed spinner and rotated, and a solution of 1.5y-methylene blue and 2y-nitrocellulose dissolved in 100 m5 of a solvent was used for spin coating. Further, the rotation speed of the high-speed spinner was doubled, and a solution of 1y-nitrocellulose dissolved in 100 ml of the solvent was used for spin coating. At this time, the thickness of the coated film was approximately 6000 mm in total for the first layer and the second layer.

This thickness is based on the semiconductor laser wavelength 8100 used for reproduction.
This is approximately the V4 wavelength of humans. Furthermore, the reflectance of the surface of the acrylic substrate at the semiconductor laser wavelength was actually measured to be 4.8 inches. On the other hand, the reflectance of the prepared coating film was 4.0%. The disk produced in this way was heated to 1100O
While rotating at RP, an H81'ie laser with an output of smW was focused to a diameter of about 1.2 μm, and as a result of one round recording, a groove of about 1 μm was formed over the entire circumference. Next, using a semiconductor laser with an output of 04 mW focused to a beam diameter of about 2.6 μm, the intensity of reflected light was measured using the optical system shown in FIG.

In FIG. 3, 4 is a semiconductor laser, 5, 8.degree. 10 is a condenser lens, 6 is a polarizing beam splitter, 7 is a quarter wavelength plate, 9 is an optical disk, and 11 is a light receiver. the result,
The reflected light intensity when the playback beam was positioned above the recorded groove was 0.6 μW, while the light intensity when the playback beam was removed from the recorded groove was 1.8 μW. A disk similar to the disk described above was prepared using a glass substrate having an outer diameter of 120 mm, polymethyl methacrylate as a polymer binder, and methylene blue as a dye. In this disc, 20
Recording and reproduction were carried out in the same manner as in the reproduction optical system shown in FIG. 3, except that a mW H6N laser was used, and as a result, similar reproduction results were obtained.

In the above embodiment, methylene blue was used as the light absorber and aeNe laser was used as the recording light source, but the present invention uses methylene blue as the light absorber and aeNe light as the recording light source. It is effective for dyes with Still, the present invention has light absorption property for the wavelength of the recording light source,
It is effective for pigments that have good dispersibility in solvents that dissolve polymeric binders. +1 In the above embodiment, a two-layer structure was used in order to equalize the reflectance of the reflected light from the written part and the reflected light from the non-written part in order to cause interference between the reflected light from the written part and the reflected light from the non-written part during reproduction. This is effective even in a single layer structure, a multilayer structure, or a structure with continuous distribution by making the reflectance uniform.

As described above, according to the present invention, with respect to the laser light source used during reproduction, there is a difference of 0.3 between the reflection strength 1 of the substrate and the reflection strength 2 of the recording layer made of a polymer binder and a light absorber.
2 (In order to satisfy the relationship I2/I+ < 2.0, the development process can be improved by aligning the reflectance on the recording layer surface and the reflectance on the substrate surface, such as by creating a two-layer film structure. It is possible to realize an interference-based heat mode recording medium that does not require the use of interference.Therefore, it has the advantage of not only simplifying the recording apparatus but also allowing additional writing to be easily performed on the user's side.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the optical information recording carrier according to the present invention in an unrecorded state, FIG. 2 is a block diagram showing the same record carrier in a recorded state, and FIG. 3 is a block diagram showing the optical information recording carrier according to the present invention. FIG. 4 is a block diagram showing the reproduction optical system of the carrier, and a characteristic diagram showing the degree of modulation with respect to the reflection intensity ratio of the optical information recording carrier. 1... Substrate, 2... One layer of first polymer binder, 3... One layer of second polymer binder. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 h /(t

Claims (2)

[Claims] (1) A substrate that reflects a portion of light, and a recording material formed in the form of a thin film on this substrate, consisting of a light absorber and a polymer binder, which evaporates or vaporizes when irradiated with laser light to record information. 0.32<I2/L<
2. An optical information recording carrier characterized in that the substrate and the recording material layer have the same reflectance so as to satisfy the following relationship. (2) The recording material layer has a laminated structure of one layer of a polymer binder containing a light absorber and one layer of a polymer binder not containing a light absorber from the substrate side. Information record carrier.