JPH0251393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording system that can record and reproduce information using laser light, and more specifically, the present invention relates to an optical recording system that can record and reproduce information using a laser beam, and more specifically, an optical recording system that uses a change in the state of matter to record information using light energy at the oscillation wavelength of a semiconductor laser. Regarding the optical recording method used.

Conventionally, Te alloys, Te oxides, bubble-forming media, organic dyes, and the like have been used as optical recording media for the above-mentioned recording methods.

Te 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 for recording and reproduction compact, but it is chemically unstable and easily deteriorates when left in the air. There is a problem that (Te, As, Se, etc.) exhibit toxicity.

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 has a layered structure consisting of a reflective layer, a transmitting layer, and an absorbing layer, and uses repeated reflection interference to increase light absorption and achieve high sensitivity. Therefore, this medium is currently one of the most sensitive media, but due to its multilayer structure, the number of times the film is formed is large, and the repeated reflection interference greatly depends on the thickness of each layer. The drawback is that the film thickness must be strictly controlled.

On the other hand, organic dye media have been developed in various forms. They can be roughly divided into single dye types and compatible types in which the dye is dissolved in a polymer resin using a solvent. For example, as disclosed in JP-A-55-161690, a compatible medium is formed by dissolving polyester yellow as a pigment in a polymeric resin, polyvinyl acetate, using a solvent, and forming it on a substrate by a spin coating method. Ru. This medium has a relatively short wavelength range (400~
500 nm), but there is almost no absorption in the semiconductor laser wavelength range (~800 nm), so it cannot be used as a medium for recording devices that use semiconductor lasers. Furthermore, in general, the method for forming a compatible medium is limited to solvent coating, and when a resin is used for the substrate, there is a restriction that a solvent that does not dissolve the resin must be selected. On the other hand, as a single dye medium, for example, a medium in which squarylium dye is formed by vapor deposition method is published in Japanese Patent Application Laid-Open No.
Disclosed in No. 46221. This dye has relatively large absorption in the near-infrared wavelength region, which is the oscillation wavelength of semiconductor lasers, but its recording sensitivity is worse than Te alloy.

An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide a highly sensitive and chemically stable optical recording system in the wavelength region of semiconductor lasers.

That is, in the present invention, on one side of the substrate, the general formula (In the formula, R represents OH, NH ₂ , NHX or NX ₂ ,
(R')n represents an alkoxyl group, and n represents the number of substitutions. (Here, X represents an alkyl group.)
It is characterized in that a recording layer containing a naphthoquinone dye represented by the following as a main component is provided, and information is recorded and reproduced from the substrate side using a laser beam.

The naphthoquinone dyes represented by the above general formula are collectively called 2,3-dicyano-1,4-naphthoquinone, and the absorption peak wavelength varies from the visible region to the near-infrared region depending on the type of auxochrome at the 5 and 8 positions. Changes to All of the above-mentioned auxochromes have absorption peak wavelengths in the near-infrared region, but as R in the above general formula,
A compound to which NH ₂ is added is most compatible with the oscillation wavelength of a semiconductor laser, and a compound in which (R')n is an alkoxyl group is most preferable considering other conditions.

for example 5-amino-2,3-dicyano-8 represented by
-[(4-methoxy)phenylamino]-1,4-
When naphthoquinone was measured in acetone solvent,
The absorption maximum wavelength λmax of the spectrum of this dye is
It can be seen that the wavelength is 770 nm, which matches well with the oscillation wavelength of a semiconductor laser. The naphthoquinone dye compound is stable even under relatively high temperature and high humidity environmental conditions, and does not show deterioration due to air oxidation unlike Te alloys. This means that it can withstand long-term use without a protective film. In addition, this compound has a low thermal conductivity similar to general organic dyes, and its value is 1/10 to 1/100 of that of metals. Therefore,
Diffusion of heat in the medium during laser beam recording is reduced, and the temperature of the medium at the light irradiation part can be efficiently raised.

The recording medium is formed by depositing the above naphthoquinone dye on one side of a substrate by vapor deposition or solvent coating. Among the naphthoquinone dyes mentioned above, R is NH ₂
When (R')n is an alkoxyl group, the temperature is about 200℃~
Vapor deposition is possible at around 240℃. Various substrate materials can be used, but generally glass,
Synthetic resin is preferable. Examples of synthetic resins include polymethyl methacrylate (PMMA), polysulfone, and polycarbonate. The substrate shape can be circular, tape, or sheet.

When a naphthoquinone dye film formed on a substrate is irradiated with semiconductor laser light focused by a lens, the dye film in the irradiated area is removed and holes are formed. Although the mechanism of this pore formation is not clear, it is thought to be due to melting and aggregation accompanied by evaporation (sublimation). The size of the hole formed depends on the focused diameter of the laser beam, laser power, and irradiation time, but it is preferably about 0.2 to 3 μm. The laser energy required for such hole formation is small and therefore
Pore formation is possible in a short time. Specifically, the wavelength
830nm AlGaAs semiconductor laser beam with a beam diameter of 1.4μ
When the light is focused at m, the power on the pigment film surface is 2~
Holes can be formed with an irradiation time of 10 mW and an irradiation time of 50 to 300 nsec. Naturally, holes can be formed under conditions that exceed the upper limits of the above power or irradiation time, but the above conditions are desirable usage conditions. Information is recorded by associating binary information with the presence or absence of holes. Information is usually recorded by rotating a disk-shaped medium at a constant speed and forming holes in accordance with the recorded information. In the above case, the thickness of the pigment film is 0.01 to 0.5 μm, preferably 0.02 to 0.2 μm.

The information (holes) recorded in this manner is read out by detecting changes in the amount of light reflected or transmitted from the medium. Generally, a method of detecting reflected light is adopted. This is because the optical system for reflected light detection is simpler. That is, this is because one optical system can project and collect light. For reading, laser light is continuously irradiated. The light intensity at that time is set to a weak energy that does not cause any shape change to the medium, and is 1/5 to 1/5 of the light intensity during normal recording.
It is 1/10.

There are two directions of incidence of light during recording and reproduction: toward the medium surface and toward the substrate surface. When incident on the substrate side,
This is a more desirable form because it allows recording and reproduction without being affected by dust attached to the surface of the medium. Note that if the substrate thickness is 1 mm or more, the beam diameter on that surface is sufficiently large to prevent dust adhering to the surface of the substrate opposite to the surface on which the medium is formed, as well as defects such as scratches on that surface. Does not adversely affect recording or playback.

Information is recorded as a series of holes. The rows of holes generally form a number of concentric or spiral tracks. When reproducing, the light beam needs to accurately track the hole rows of a specific track. One way to achieve this is to increase the precision of the rotating mechanism by using air bearings or the like. However, in this case, there would be a plurality of rotating systems and the cost would be high, so it is not practical. More desirable is a method in which light guide grooves are provided on the substrate. When light enters a groove about the diameter of a beam, it is diffracted. The spatial distribution of the diffracted light intensity changes as the beam center shifts from the groove, and a servo system can be configured to detect this and direct the beam to the center of the groove. Usually, the width of the groove is set in the range of 0.6 to 1.2 μm, and the depth is set in the range of 1/8 to 1/4 of the recording/reproducing wavelength used. The recording layer is therefore formed on the grooved substrate surface.

A thin film of 2,3-dicyano-1,4-naphthoquinone dye can be easily formed by a conventional resistance heating vapor deposition method. When a thin film is formed on a substrate kept at room temperature, its crystallinity becomes amorphous, that is, it becomes amorphous. Since the reflected light from the amorphous film does not include grain boundary noise seen in polycrystalline films, the reproduction S/N is good when using the amorphous film.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows 5-amino-2,3-dicyano-8-[(4-methoxy)] actually created on a substrate by vapor deposition.
This figure shows the absorption spectrum of a thin film of phenylamino]-1,4-naphthoquinone dye. From this, the oscillation wavelength of the AlGaAs semiconductor laser is ~
It was confirmed that the dye has an absorption maximum near 800 nm and is suitable as an optical recording medium using a semiconductor laser. The complex refractive index of the deposited film is 2.4-i0.7 at a wavelength of 830 nm.

Next, 5-
Amino-2,3-dicyano-8-[(4-methoxy)phenylamino]-1,4-naphthoquinone dye was deposited by resistance heating to obtain a film with a thickness of 935 Å.
The resistance heating port material was Mo, and the degree of vacuum during vapor deposition was 1.5×10 ^-5 Torr or less. The substrate was left to stand at room temperature, and almost no rise in substrate temperature due to vapor deposition was observed. Gradually increasing the port temperature
The dye melts at 233°C, and the deposition rate when deposited at this temperature is 5 Å/sec.

The decomposition temperature of this dye is 295°C, which is sufficiently higher than the vapor deposition temperature.

FIG. 2 shows the medium 1 thus formed. A dye film 20 is formed on a PMMA substrate 10. This medium 1 was irradiated with a semiconductor laser beam having a wavelength of 830 nm through the substrate 10 from the direction of the arrow 50, condensed by an optical system (not shown). In this case, the laser beam has a power of 2 to 10 m on the medium surface.
W, irradiation time 50-300n sec, radiation time 50-300n
sec, and the medium moving linear velocity was 1.3 m/sec. The recording sensitivity at this recording wavelength was about 40 mJ/cm ² . According to this recording, about 1μ in the pigment film 20.
A hole 40 having a diameter of approximately 1.0 m was formed.

As is clear from the above examples, it can be seen that the optical recording method obtained by the present invention has the excellent advantages of being highly sensitive, chemically stable, and durable for long-term storage. In addition, in this example, an example was shown in which methoxyl group CH ₃ O was used as the alkoxyl group (R')n, but in addition to this, ethoxyl group
Even with carbon-rich compounds such as C ₂ H ₅ O- and propoxyl group C ₃ H ₇ O-, almost the same effectiveness as in the example can be obtained.

[Brief explanation of drawings]

Figure 1 shows 5-amino-2,3-dicyano-8-
FIG. 2 is a graph showing the absorption spectrum of the [(4-methoxy)phenylamino]-1,4-naphthoquinone dye deposited film, and is a cross-sectional view of an optical recording medium according to an embodiment of the present invention, in which 10 is a substrate; 20
50 indicates a dye film, 50 indicates a light incident direction, and 40 indicates a hole.

Claims (1)

[Claims] 1. On one side of the substrate, a general formula (In the formula, R represents OH, NH ₂ , NHX or NX ₂ ,
(R')n represents an alkoxyl group, n represents the number of substitutions (here, X represents an alkyl group)) A recording layer containing a naphthoquinone dye as a main component is provided, and information is recorded using a laser beam. -An optical recording method characterized by reproduction from the substrate side.