JPS5973996A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide a stable optical recording medium having long-term preservability, obtained by providing a layer more absorbing light with a wavelength shorter than that of laser beam used in recording regeneration to the single side or both sides of a recording layer. CONSTITUTION:A recording layer containing coloring matter more absorbing light having a wavelength shorter than that of laser (e.g., semiconductive laser) beam used in recording regeneration [e.g., 5-amino-2,3-dicyano-8-(4'-butylanilino)- 1,4-naphthoquinone coloring matter] is provided to the single side or both sides of a substrate (e.g., glass) to obtain an objective optical recording medium for recording and reading information by laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical NlyN medium on which information can be recorded and reproduced using laser light.

Conventionally, as this type of optical I1 recording medium, Te alloy, Te
Oxides, bubble-forming media and organic dyes have been used.

The 're alloy is used as a solid solution alloy of Te and semiconductors such as As and Se. This medium has relatively high writing sensitivity and is compatible with semiconductor lasers, which can make the optical system of the recorder smaller, but it is chemically unstable and easily deteriorates when left in the air, and its constituent materials (Te
, As, Sc, etc.) are toxic.

Although Te oxide is more stable than Te alloy, its optical properties, such as absorption and reflectance, depend sensitively on the oxidation state. Therefore, this medium has the disadvantage that the oxidation state must be tightly controlled during the formation of the medium.

The bubble-forming medium consists of three layers: a reflective layer, a transmitting layer, and an absorbing layer.
It has a layered structure and uses repeated reflections and interferences to increase light absorption and achieve high sensitivity. Therefore, this medium is currently one of the most highly sensitive media, but because of its multilayer structure, it requires a large number of film formations, and because the repeated reflection interference largely depends on the thickness of each layer, the film thickness at the time of film formation is The disadvantage is that strict control is required.

Organic dye media have been developed in various forms, and they can be roughly divided into simple dye types and compatible types in which the dye is dissolved in a sieve molecular resin using a solvent.

Dyes generally exhibit absorption in the visible wavelength range. On the other hand, in optical recording and reproducing devices, it is desired to use a semiconductor laser which can make the device smaller, and its oscillation wavelength is about 800 nm. There are few dyes that exhibit large absorption in such long wavelength (near infrared light) regions, but some cyanine dyes and SQUA IJ
It is known that dyes exhibit absorption in long wavelength ranges.

When optical recording and reproduction are performed using such a dye, good characteristics are obtained, and the dye medium is found to be effective as an optical recording medium. However, the biggest drawback of dye media is that they undergo photochemical reactions and decompose due to light absorption. Therefore, there is a problem that it lacks long-term shelf life.
An object of the present invention is to provide an optical recording medium that is stable and durable for long-term storage.

In other words, the present invention provides an optical recording medium in which a recording layer containing at least a dye is provided on one or both sides of a substrate, and information is recorded and read by a laser beam. It is an optical recording medium provided with at least one layer that absorbs more light with a shorter wavelength than the wavelength of light.

Pigments exhibit a unique color because they absorb specific wavelengths of visible light and reflect other wavelengths and regions. The colors of the absorbed wavelengths are called spectral colors, and the colors that are reflected and perceived by the eye are called residual colors. Therefore, red pigments have absorption on the short wavelength side, and color-producing pigments have absorption on the long wavelength side.

Due to absorption of light, common dyes exhibit a fading phenomenon. This is because the dye molecules that are electronically excited by light absorption are decomposed. This decomposition is described by a type of reaction kinetics, and the rate of fading is expressed by a rate constant. Desirable dyes for use in optical recording media are dyes that exhibit large absorption at the wavelength of recording and reproducing laser light and have a slow fading rate, that is, have high light fastness. Laser light is almost ideal monochromatic light, but
Dyes generally have a wide absorption spectrum, and also absorb ultraviolet light that does not contribute to recording and reproduction. Therefore, by suppressing the absorption of light unnecessary for recording and reproduction, the stability of the dye film is dramatically improved.

As a recording/reproducing laser, it is possible to miniaturize the device.
It is desirable to use a single-body laser. The oscillation wavelength of the semiconductor laser is approximately 8000 m in the near-infrared region. Therefore, it is necessary to use a dye that exhibits absorption in this wavelength region as a medium; for example, squarylium and naphthoquinone dyes can be used. On the other hand, many materials are known that exhibit almost no absorption in this near-infrared wavelength region, but exhibit large absorption in the T5j and ultraviolet wavelength regions. Therefore, by layering a dye medium that absorbs semiconductor laser light with a substance that exhibits little absorption in the near-infrared wavelength region, a medium with high optical fastness can be constructed.

The medium is constructed by attaching a recording layer (in this example, a dye film) to a substrate. As the substrate, glass, synthetic resin, aluminum alloy, etc. are usually used. The shape of the substrate used may be a disk shape, a curved shape, a sheet shape, etc., but in this ff1J, a case where a disk-shaped substrate is used will be explained. In the case of a substrate (glass, synthetic resin) that is transparent to the recording/reproducing wavelength, the recording/reproducing light can be irradiated onto the recording layer through the substrate.
This is suitable because the substrate can be used as a protective layer. This is because when the thickness of the substrate is approximately 0.5 mm or more, the diameter of the light beam on the opposite substrate surface to which the recording layer is attached is large enough to reduce the influence of dust attached to that surface. It depends. As a synthetic resin, polymethyl methacrylate (PMMA)
, polyvinyl chloride, polysulfone, polycarbonate, etc.

The present invention will be described in detail below with reference to the drawings.

Figure 1 shows that when a semiconductor laser is used as a recording/reproducing light source,
Absorption spectrum 1 of 5-amino-2,3-dicyano-8-(4'-butylalinino)-1,4-naphthoquinone dye (hereinafter abbreviated as naphthoquinone dye) film, which is one of the preferred dye recording layers, is shown below. show. The figure also shows absorption spectrum 2 of the titanium phthalocyanine film. Here, the thickness of the naphthoquinone dye film was 55 nm, and the thickness of the titanium phthalocyanine film was 14 Q nm, and these were formed by a resistance heating vapor deposition method. It can be seen that titanium phthalocyanine exhibits a larger absorption peak at 750 nm than the wavelength of 5QQ nm, and has the effect of shielding the short wavelength side of the absorption peak of the naphthoquinone dye. If an AtGaAs semiconductor laser is oscillated at a wavelength of 830 nm and used as a light source for recording and reproduction, titanium phthalocyanine is effective as a light shielding layer when a naphthoquinone dye is used as a recording layer. Note that effects similar to those of titanium phthalocyanine can also be obtained with other metal phthalocyanines, such as copper phthalocyanine. Furthermore, blue pigments other than phthalocyanine that are resistant to light, such as anthraquinone pigments, naphthoquinone pigments, and indigo thread pigments, can also be used. Furthermore, semiconductor materials such as Si and Se can also be used.

FIG. 2 shows (support) 11 of the embodiment of the medium according to the present invention. A naphthoquinone dye film 20 is formed as a recording layer on a disc-shaped substrate IO. A light shield M:30 is formed on this recording layer 20.

This structure is effective when using an opaque substrate such as an aluminum alloy. Incidentally, when a substrate with good thermal conductivity such as an aluminum alloy is used as in Shusho, a heat insulating layer of oxide or resin may be provided between the substrate and the recording layer. Furthermore, in the structure shown in FIG. 2, since the light shielding layer 30 is in close contact with the recording layer 20, the energy required to form holes in the recording layer increases. A structure that improves this is shown in FIG. A photocurable lacquer is formed on the substrate 10 and layered 11 times as a heat insulating layer 4 ( ).A recording layer 20 is laminated thereon, and then an intermediate layer 50 is formed of a C rubber-based resin. A shielding layer 30 is formed.Since the intermediate layer 50 is made of a rubber-based resin, it does not inhibit the deformation of the recording layer during hole formation, and the recording energy changes little compared to the case of a single recording layer. do not.

FIG. 4 shows a desirable media structure when using a transparent substrate (PMtMA). Transparent disk substrate 1. +
1, ](+1 are facing each other with an air layer 100 in between.

The side disc substrates +0, 1 (1') are fixed with spacers 200, 200' at their periphery and center.A light shielding layer: 10, 3
0' is formed, and recording layers 20 and 20' are laminated thereon. For recording and reproduction, use the arrow 30 for the recording layer 20.
The laser beam is applied to the recording layer 201 from the direction of arrow 300'. External light that does not contribute to recording enters through the substrates 10 and 10', but the light shield Ji
Most of it is absorbed from r(0, 30'!) and does not reach the recording layer 20, 7.0'.

As explained above, according to the present invention, the light resistance of a dye medium can be greatly improved, and a stable optical recording medium with long-term storage stability can be obtained. Note that the present invention is not limited to the above FIj2 embodiment, and changes in details within the spirit of the present invention are included in the present invention.

[Brief explanation of the drawing]

Figure 1 shows 5-amino-2,3-dicyano-8-(4'-
Graph showing absorption spectra of (butylalinino)-1,4-naphthoquinone and titanium phthalocyanine, FIG. 2 is a cross-sectional view of an optical recording medium of one embodiment according to the present invention, and FIG. 3 is a graph showing the optical recording medium of another embodiment according to the present invention. FIG. 4 is a cross-sectional view of an optical recording medium according to still another embodiment of the present invention, in which 10,1σ is the substrate, 2
0; 20' is a recording layer, 30.30' is a light shielding layer,
40 is a heat insulating layer, 50 is an intermediate layer, 300, 30 (1' indicates the direction of incidence of light. Fig. 1 Wavelength (nrrL) Fig. 2 Fig. 0 Fig. 3 Fig. 4

Claims (1)

[Claims] In an optical recording medium in which a recording layer containing at least a dye is provided on one side or both sides of a substrate, and information is recorded and read by a laser beam, one or both sides of the recording layer are provided.
111. An optical recording medium comprising at least one layer that absorbs more light having a wavelength shorter than the wavelength of the laser beam.