JPS5916156A - Optical memory medium - Google Patents

Abstract

PURPOSE:To record and reproduce information with a high S/N by a laser beam having a low energy density, by utilizing the property of a low-melting point alloy layer whose peripheral part of a recessed part of a fused part becomes round easily by flocculation and contraction due to the surface tension when this layer is fused and evaporated by the irradiation of a laser beam. CONSTITUTION:An aluminum thin film having about 800nm thickness is formed as a reflective film 2 on one face of a plastic disc 1 having 20cm diameter by vacuum deposition, and a low-melting point alloy layer 3 having a thickness of 10-100nm is formed on the film 2 by sputtering, and a recording layer 4 consisting of a coloring matter thin film having a thickness of 10-100nm is formed on the layer 3 by the vacuum deposition method or the ion plating method, and layers 3 and 4 are laminated plural times, and a coloring matter thin film recording layer 4 is formed as the top layer. Since this layer 4 has a reflection factor lower than that of the low-melting point alloy layer and has a heat conductivity lower than that of the low-melting point alloy layer, a low laser output can be used when the layer 4 is formed as the top layer. It is necessary that the melting point of the low-melting point alloy layer is equal to or lower than that of the coloring matter thin film recording layer. Since a medium is formed with a laminated composite film, information is recorded with a low laser output, and the S/N for reproducing is improved to enhance the sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly sensitive optical memory medium that is effective when applied to an optical memory device that optically records and reproduces information.

Conventionally, optical memory media of this type have been prepared using a glass or plastic substrate as a recording layer such as Bi,
Forming a metal thin film layer such as To or an organic dye thin film layer,
A method of recording information by forming recesses (bits) based on the principle of melting and evaporation using focused laser light has been used. however.

Such a metal thin film recording layer generally has a high reflectance.

For example, in the case of Bi, it reaches about 65% in visible light, and its melting point is relatively high, for example, 271°C, T
This was caused by the fact that the temperature was 450'C at o, and the recording sensitivity was low, so a high output laser device was required for recording. On the other hand, organic dye thin film recording layers generally have low reflectance, low thermal conductivity, and relatively low melting points, so they have relatively high sensitivity and can therefore be recorded with low output lasers. As with many metal thin films, the shape of the periphery of the recesses generated by laser beam irradiation tends to be jagged or mortar-shaped, which reduces the symbol-to-noise ratio (S/N ratio) during information reproduction. There were drawbacks.

The present invention was made in view of the current situation, and
The aim is to provide a highly sensitive optical memory medium that overcomes the drawbacks of the prior art.

The optical memory medium of the present invention is composed of a thin film low melting point alloy layer and a dye thin film recording layer that are alternately formed in a laminated manner on a glass or plastic substrate on which a reflective film layer has been formed in advance, and the outermost layer is a dye thin film recording layer. It consists of a thin film recording layer, and can record and reproduce information by simultaneously forming recesses in the laminated portion of the dye thin film recording layer and the thin low melting point alloy layer by irradiating it with a laser beam. A feature of the present invention is that information recording and reproduction with a high S/N ratio can be obtained using a laser beam with a low energy density. In other words, when the low melting point alloy layer is melted and evaporated by laser beam irradiation, the molten part aggregates and evaporates due to surface tension.
By taking advantage of the property that the periphery of the recess tends to become circular when it contracts.

Even if the shape of the four parts of the dye thin film recording layer melted and evaporated at the same time is an imperfect shape such as a jagged shape or a mortar shape, it is corrected into a perfect circular shape by the above-mentioned properties of this low melting point alloy layer, so the S is high. /N ratio can be obtained. Furthermore, when the low melting point alloy layer and the dye recording layer are laminated as thin films, the above effect becomes even greater. The reason why the outermost layer of the laminated portion is a dye thin film recording layer is that it has a lower reflectance and a lower thermal conductivity than a low melting point alloy layer, so that a lower laser output can be used. The melting point of the low melting point alloy layer in the present invention needs to be on the same level as or lower than the melting point of the dye thin film recording layer used. For example, if this relationship is reversed, a dye thin film can be formed by a laser beam with a low energy density. Even if a recess is formed in the recording layer, the low melting point alloy layer does not change, so that one object of the present invention cannot be achieved. The composition of the low melting point alloy layer in the present invention is Sn, Bi, Pb.
, Cd, the composition of component 1 can be appropriately selected depending on the required melting temperature, for example, 12.5%Sn-50.0%B1-26.0
%pb-12,5%cd alloy has a melting temperature of 60-7
2°C, 1e, o%5n-52.0%B1-32.0
%Pt) alloy has a melting temperature of 96°C94s, o%5n-
s, o%B1-52. The o%Pb-1s, o%Ca alloy has a melting temperature of 132-139°C, 43.0% Sn -
14.0%B1-43.0%pb alloy has a melting temperature of 14
These low melting point alloys can be easily formed by vacuum deposition or sputtering on a substrate on which a thin aluminum film or the like is vacuum deposited as a reflective film. Note that this low melting point alloy is not alloyed because its melting point is significantly different from that of a reflective film such as aluminum. The dye thin film recording layer is not limited to 14% of the dye, but oxazine dyes, aniline dyes, naphthol dyes, etc. can be applied, and vacuum evaporation method, ion blating method, etc. are used.

Alternatively, it can be easily formed by applying, drying, and curing using a spinner method using an appropriate solvent. This is explained by:

FIG. 1 is a system diagram showing an example of the recording and reproducing process using the optical memory medium of the present invention, and FIG. 2 is an enlarged view of a part of the optical memory medium after recording in FIG. FIG. In the figure, 1 is a medium, 2 is a reflective film, 3 is a low melting point alloy thin film, 4 is a dye thin film recording layer, 3 and 4 are stacked layers of three or more layers, 5 is a rotating device, 6 is a laser, and 7 is an optical modulator , 8
is a polarizing beam splitter, and 9 is an objective lens.

Reference numeral 10 indicates a photodetector, 11 indicates a concave portion serving as a recorded portion, and 12 indicates an unrecorded portion. Said 1 is a circular plate made of glass or plastic such as polymethyl methacrylate and has a diameter of 20α, and on one side thereof is coated with a reflective film 2 of, for example, approximately somm.
A thin aluminum film is formed by vacuum evaporation, a low melting point alloy layer 3 with a thickness of 10 to 100 mm is sputtered thereon, and a recording layer 4 made of a thin dye film with a thickness of 10 to 1 oomm is further formed on it by vacuum evaporation. is formed by the ion blating method, and each layer of 3 and 4 is laminated multiple times.

The uppermost layer is a dye thin film recording layer 4.

The optical memory medium thus produced is mounted on a rotating device and recorded and reproduced while being rotated. For recording, first, a laser beam from a laser 6 is modulated by an optical modulator 7 to become light having information, and the beam diameter of the laser beam focused by a polarizing beam splitter 8 and an objective lens 9 is about 1 μm.

Due to the heat action, the dye thin film and the low melting point alloy layer 3 of the recording layer 4 are melted and evaporated, and as a result, recesses 11 as shown in FIG. 2 are formed and information is recorded.

To reproduce the recorded information, the output of the laser beam in the laser 6 is set to the same level as that at the time of recording, that is, to an output level that does not melt and evaporate the unrecorded layer 12.
Due to the difference in reflectance between the two, the photodetector 10 converts it into an electrical signal and reproduces the information.

Next, specific examples of the present invention will be described.

(Example 1: 16.0%Sn -52.0%B as low melting point alloy layer 3
1-32.0% Pb alloy (melting temperature 96°C)' (
Next, a dye thin film recording layer 4 having a molecular formula of Ca1l HI5 N3 was formed with a thickness of 10 ow' by sputtering.
Demethylaniline dye (melting temperature 115°C
) 50 by k ion brating method? KI was formed, and this process was repeated twice in total to form a 4-layer stack to produce an optical memory medium using the method explained in FIG.
Recording of color video signals using e-Ne laser light;
Played. As a result, good reproduced image quality with an S/N ratio of 45 dB or more was obtained.

(Example 2) 56.6%B1-44.6%pb as low melting point alloy layer 3
An alloy (melting temperature 124°C) was sputtered to a film thickness of 20 stripes to form the dye thin film recording layer 4 with the molecular formula 〇18H+6O.
Naphthol dye represented by N2 (melting temperature 133'C
) Formed to a film thickness of 100'n'rn by e-spinner method,
This process was repeated a total of two times to create a four-layer stack, and an optical memory medium was fabricated and subjected to recording and playback experiments in the same manner as in Example 1. Results almost the same as in Example 1 were obtained. .

(Example 3) Demethylaniline dye (f: +aH+5Ns, melting temperature 11
6'C) Ion plated to a film thickness of 10mm, and 16.0%Sn-62,0%B1-52. o%Pb
Alloy 3 (melting temperature 96°C) film thickness 10Tl? Sputtering on lt.

Furthermore, a beta naphthol dye (024N20 N40. Melting temperature 184-1
86'C) '(Ion plated to a z film thickness of 101?rl and laminated with a total of 6 layers. An optical memory medium was prepared and recording and playback experiments were conducted in the same manner as in Example 1. We were able to obtain results approximately equivalent to 1.

As explained above, the optical memory medium of the present invention is composed of a laminated composite film of a dye thin film recording layer and a low melting point alloy layer having a melting temperature equal to or lower than the melting temperature of the dye thin film recording layer. As a result, information can be recorded with low laser output, and the S/N ratio during playback is also significantly improved, resulting in high sensitivity.

As a result, it has the advantage of being able to reduce the prices of various memory devices.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a recording and reproducing process using an optical memory medium, and FIG. 2 is an enlarged cross-sectional view of a main part of the optical memory medium after recording in FIG. 1. 1... Base body, 2... Reflective film, 3...
-Low melting point alloy layer, 4... Dye thin film recording layer, 11
...Concave portion, 12...Unrecorded portion.

Claims (3)

[Claims] (1) Consisting of a substrate on which a reflective film layer is formed, thin low melting point alloy layers and the dye thin film layer that are alternately laminated on this substrate so that the outermost layer is a dye thin film layer, and is irradiated with laser light. An optical memory medium in which information is recorded by forming recesses in the dye thin film layer and the thin low melting point alloy layer. (2) The composition of the thin film low melting point alloy layer is Sn, Bi, Pb
The optical memory medium according to claim 1, wherein the optical memory medium is made of an alloy that is a combination of at least two of the following. (3) The optical memory medium 0 according to claim (1), wherein the melting temperature of the thin film low melting point alloy layer is equal to or lower than the melting evaporation temperature of the dye thin film recording layer.