JPS5811196A - Beam recording medium - Google Patents

Abstract

PURPOSE:To balance the absorptance of recording beams and the reflectivity of regenerating beams excellently, and to form the heat mode type beam recording medium, which is superior in sensitivity and S/N ratio, by making a beam absorbent and a beam reflector contain into a recording layer. CONSTITUTION:The beam recording medium is formed in such a manner that the recording layer (approximately 1mu thickness) 42 which makes the proper quantities of the beam absorbent (such as oleosol EL blue) and the beam reflector (such as benzine yellow) contain in nitrocellulose as a principal ingredient and makes beam absorptance to the recording beams approximately 60% or higher and the beam reflectivity to the regenerating beams approximately 10% or higher is shaped onto a substrate 40, such as synthetic resin, glass, etc. A reflecting layer normally formed between the substrate and the recording layer is unnecessitated, and the recording layer may be shaped in double layer structure consisting of a layer containing the beam absorbent and a layer containing the beam reflector.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called optical recording medium in which information is optically read out by physically deforming a recording layer.

Magnetic recording media have traditionally been used as information recording media, but they have limitations in information recording density, limitations in improving noise characteristics, and problems with the state in which the media and head are in contact. However, optical recording media have recently attracted attention as an alternative to magnetic recording media.

Among optical recording media, in so-called heat mode recording that uses light as heat, the medium is selectively irradiated with coherent light such as a laser beam to melt or burn the medium to create small holes in the medium. Information is recorded depending on the presence or absence of the information. Known materials for the recording layer used in conventional heat mode recording include tellurium, tellurium-selenium compounds, and mixtures of nitrocellulose and light absorbers. In the case of each of the above-mentioned materials, the records are permanent and the records cannot be erased or rewritten.
No. 6-51160 proposes an organic polymer material such as a low polymer compound mainly composed of styrene (for example, styrene oligomer), nylon, or ABS resin, which records information by thermally deforming the recording layer.

FIG. 1 shows an example of the structure of a conventional optical recording medium, where 10 is a substrate, 1
2 is a reflective layer made of an aluminum thin film provided thereon, and 14 is a recording layer. When recording information, the recording layer 14 is selectively irradiated with a laser beam to form a focus that partially removes or deforms the recording layer, and during reproduction, the layer 14 is irradiated with a weak laser beam to form pits. The presence or absence of pits is detected based on the difference in the amount of reflected light between the areas where the pits exist and the areas where they do not exist. The reflective layer 12 functions to increase the amount of reflected light and S/N.

In FIG. 1, 20 is a recording or reproducing laser beam, 22 is a beam splitter, Sae is a photo sensor, and 26
1 is a reproduction output terminal, 1 is a 1-wavelength plate, and 30 is an objective lens. During recording, a strong laser beam is irradiated to the recording layer 14
A pit is constructed by partially erasing or deforming. During reproduction, the presence or absence of pits can be detected by irradiating the recording layer 14 with a weak laser beam and detecting its reflected light via the beam splitter 22 using individual photosensors.

By the way, in conventional optical recording media, dyes or pigments are mixed into the recording layer as a light absorbing agent in order to ensure that the recording layer sufficiently absorbs the optical energy of the laser beam during recording to perform efficient recording. For example, if nitrocellulose is used as the recording layer and oleosole EL blue is used as the light absorbing agent, He-
Light absorption efficiency during recording when using Ne laser is 90%
It is extremely efficient.

However, conventional optical recording media have the drawback that, as a reaction to the increased light absorption rate, the amount of reflected light is insufficient during reproduction, resulting in a deterioration of the S/N of the reproduced signal. In the optical recording medium in which oleosole EL blue is mixed into the above-mentioned nitrocellulose, the reflectance is only 2 to 3%. Since the intensity of the laser beam during reproduction is approximately m of the intensity of the recording laser beam, the amount of light during reproduction is extremely insufficient.

As a conventional technique for solving the above-mentioned problem, a technique is known that uses different wavelengths during recording and reproduction (for example, an Ar laser during recording and a He-Ne laser during reproduction).
This makes the device complicated and expensive.

As another conventional technique for solving the above problem, the reflective layer 12
A technique is known in which the semi-reflective layer is made into a semi-reflective layer and the semi-reflective layer itself is removed at the pit portion when recording pits are formed. It has the disadvantage of being complex.

Another known technique is to use a material for the recording layer that has a well-balanced amount of light absorption and light reflection. For example, in the case of Te, the absorption amount is 60% and the reflection amount is 4.
Approximately 0% is convenient. However, this kind of material is Te
, As, Se, and other materials that are toxic to the human body, and has the drawback that the relationship between absorption and reflectance cannot be freely designed.

Note that the technique of forming the reflective layer 12 shown in FIG. 1 is also intended to increase the amount of reflected light, but has the disadvantage that the manufacturing process for forming the reflective layer is increased and the yield is lowered.

Therefore, the present invention is intended to improve the above-mentioned drawbacks of the conventional technology.The purpose of the present invention is to have a recording layer in the optical absorptivity mode plane with a simple structure, and to selectively remove or deform the recording layer using a laser beam to provide information. The recording layer includes a dye or pigment that absorbs the wavelength of recording light and a dye or pigment that reflects the wavelength of reproduction light.

FIG. 2 shows an example of the structure of an optical recording medium according to the present invention, in which 40 is a substrate made of synthetic resin or glass, and 42 is a recording layer with a thickness of about 1 μm. The recording layer 42 is made of, for example, nitrocellulose as a main component, into which a dye (for example, oleosole EL blue) as a light absorber and a dye as a light reflector are mixed. As the light reflecting agent, for example, pigments such as benzine yellow and brilliant carmine 6B can be used.

By controlling the mixing ratio of absorber and reflector, it is possible to arbitrarily design the light absorption rate and light reflectance of the optical recording medium as a whole. In the examples, it is optimal that the light absorption rate is about 80% and the light reflectance is about 20%, and practically it is preferable that the light absorption rate is about 60% or more and the light reflectance is about 10% or more. Note that in the above example, the light absorption rate is slightly lower than that of the conventional technology, but the recording layer made of nitrocellulose has extremely high sensitivity (1 nJ or less), so even if the light absorption amount decreases slightly, it is still sufficient for recording sensitivity. The reproduction sensitivity and S/N are improved by the increase in the amount of reflection.

As described above, in the present invention, by utilizing the wavelength dependence of the reflection spectral characteristics of dyes or pigments, arbitrary absorption and reflectance can be obtained by mixing two or more types of dyes. Further, a reflective layer or a semi-reflective layer made of metal, which is conventionally used to improve reflectance, is not necessary.

FIG. 3 shows another embodiment of the present invention, in which a light absorption layer and a light reflection layer are provided separately. Reference numeral 40 denotes a substrate made of synthetic resin or glass, which has a thickness of 10 to 20 μm in the case of a tape and about 1.5 μm in the case of a disk.

The first recording layer 44 has a thickness of about 1 μm and is made of nitrocellulose containing a light absorber. 46 is a second recording layer having a thickness of 1000 to 3000 A and made of nitrocellulose containing a light reflecting agent. In the configuration shown in FIG. 3, since the light absorption layer and the light reflection layer are provided separately, it is easier to control the absorption rate and the reflection rate.

In addition, it is of course possible to provide a layer containing a light absorbing agent on the outside as shown in FIG.

As explained in detail above, according to the present invention, since the recording layer contains both a light absorbing agent and a light reflecting agent, it is possible to easily obtain the desired absorption rate and reflectance, and the desired recording sensitivity, reproduction sensitivity, and... The S/N ratio can be easily obtained, and since there is no reflective layer, the manufacturing process is simplified.

[Brief explanation of the drawing]

FIG. 1 shows a structural example of a conventional optical recording medium, FIG. 2 shows a structural example of an optical recording medium according to the present invention, and FIG. 3 shows another structural example of an optical recording medium according to the present invention. 40・・・・・・・・・・・・Substrates 42, 44
, 46... Recording layer patent applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Patent application agent Megumi Yamamoto - Figure 1 Figure 2

Claims (8)

[Claims] (1) An optical recording medium that has a substrate and a recording layer on at least one surface thereof, and records information by selectively removing or deforming the recording layer with laser light, in which the recording layer is made of a dye or a dye that absorbs the wavelength of the recording light. An optical recording medium comprising a pigment and a dye or pigment that reflects the wavelength of reproduction light. (2) An optical recording medium according to claim 1, in which the recording layer is directly attached to the substrate. (3) Optical recording according to claim 1, in which the recording layer has a laminated structure of a first layer that is absorbent to the wavelength of the recording light and a second layer that is absorbent to the wavelength of the redirected light. Medium. (4) The optical recording medium according to claim 1, wherein the recording layer is a single layer and uniformly contains two types of dyes or pigments. (5) The optical recording medium according to claim 1, wherein the absorption rate of the recording light wavelength in the recording layer is 60% or more. (6) The optical recording medium according to claim 1, wherein the recording layer has a reflectance of 10% or more for the wavelength of reproduction light. (7) The optical recording medium according to claim 1, wherein the dye or pigment is selected under the condition that the wavelength of the recording light and the wavelength of the reproducing light are the same. (8) The optical recording medium according to claim 1, wherein the recording layer contains nitrocellulose as a main component.