JPS6141597A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain a highly sensitive and chemically stable optical information recording medium, by forming a thin org. film based on a specific naphthoquinnone dye to the single side or both sides of a substrate. CONSTITUTION:A recording medium is formed by adhering a naphthoquinone dye represented by formula to the single surface or both surfaces of a substrate by a vapor deposition or solvent coating method. As the material of the substrate, glass, A and a synthetic resin are desirable. When laser beam is converged by a lens to be allowed to irradiate a naphthoquinone dye film, the dye film at the irradiated part is removed to form a hole. The recording of information is performed by rotating disc shaped medii at an equal speed and forming holes in matching relation to binary information while the reading of recorded information (hole) is performed by detecting the change in the quantity of reflected light from the medium or transmitted light. Thus formed optical information recording medium is highly sensitive and chemically stable and, in addition thereto, the medium is easy to form.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an optical recording medium that can record and reproduce information using laser light, and more specifically, relates to an optical recording medium that uses a change in the state of matter caused by light energy to perform recording. Related to optical information recording media.

(Prior art and its problems) Conventionally, Te alloy has been used as this type of optical recording medium.

Te oxide, bubble-forming media, organic dyes, etc. were used.

A Te alloy is used as a solid solution alloy of Te and a semiconductor 1 such as As, 86, etc. 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.
It deteriorates easily when left in the air, and the constituent materials (TB
e A3 e 86, etc.) are toxic.

Although the l1le oxide is more stable than the Te alloy, its optical properties 1 such as absorption 1 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 repeats reflection interference to increase the light absorption rate 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.

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. A compatible medium is, for example, as disclosed in JP-A No. 55-161690, in which polyvinyl acetate, which is a polymeric resin, is mixed with polyester yellow as a dye using a solvent, and formed on a substrate by a single rotation coating method. be done. However, 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 type medium, for example, a medium in which a SQUARE IJIJum dye is formed by a vapor deposition method is disclosed in JP-A-56-46221. This dye has relatively large absorption in the near-infrared wavelength region, which is the oscillation wavelength of semiconductor lasers, but the recording sensitivity is T
Worse than e-alloy.

(Objective of the Invention) 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 information recording medium.

(Structure of the Invention) That is, the present invention provides an optical information recording medium in which a recording layer is provided on one or both sides of a substrate, and information is recorded and read by a laser beam. It is characterized by the formation of an organic thin film whose main component is dye.

(Detailed Description of Structure) The naphthoquinone dye represented by the above chemical structural formula exhibits large absorption in the near-infrared region, and is suitable for recording and reproduction using semiconductor laser light. An example of synthesis of this dye is shown below.

2.3-Dichloronaphthazarin in Br and glacial acetic acid,
When reacted in the presence of a catalytic amount of iodine, 2,3.6°7-
titrabromnaphthazarine 0] and 2-chloro-3,6,
7-Doribromnaphthazarine esters are obtained in approximately equal proportions. [A mixture of D and esters 1001n9 is dissolved in 10 m/p of pyridine. On the other hand, 2-aminothiophel 507129 and KOH23rn9 were dissolved in pyridine 2, this solution was added dropwise to the pyridine solution prepared above [D] at 0°C, and the mixture was reacted at 0°C for 2 hours. In addition, the pH was adjusted to 4 with hydrochloric acid, the solvent was distilled off under reduced pressure after extraction with chloroform, and the crystals were recrystallized from chloroform to obtain the desired product in a yield of 20 cm.

The dyes thus obtained (hereinafter abbreviated as naphthoquinone dyes) are the following three compounds [A].

It is a mixture of [mark] and [q.

When the absorption spectrum of this dye was measured in chloroform, absorption peaks were observed at 630, 685, and 750 nm, and the λ axis was found to be 75Q nm. The naphthoquinone dye 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 that of general organic dyes, and its value is lower than that of metals.
It's a box. Therefore, the diffusion of heat in the medium during laser beam recording is reduced, and the temperature of the medium at the light irradiation section can be efficiently raised.

The recording medium is formed by attaching the above naphthoquinone dye to one or both sides of a substrate by vapor deposition or solvent coating. Various materials can be used as the substrate material, but glass, KL, and synthetic resin are generally preferred. Examples of the synthetic resin include polymethyl methacrylate (PMMA) and polyvinyl chloride (PvC).

Examples include polysulfone and polycarbonate. The substrate shape can be a disk shape, a tape shape, or a sheet shape. When the naphthoquinone dye film formed on the substrate is irradiated with 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 and the laser power.

Although it depends on the irradiation time, it is preferably about 0.2 to 3 μm. The laser energy required to form such a hole is small, and therefore the hole can be formed in a short time. 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 addition.

In the above cases, the thickness of the pigment film is 0.01 to 0.5μ
m, preferably 0.02 to 0.2 μm.

To read out the information (holes) recorded in this way.

This is done 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 is simpler when detecting one reflected light. That is, this is because one optical system can project and collect light. For reading, laser light is continuously irradiated. The amount of light at that time is set to a weak energy that does not cause any shape change to the medium.
It is.

There are two directions of incidence of light during recording and reproduction: toward the medium surface and toward the substrate surface. Both orientations can be used with single layer media such as the present example. When the light is incident on the substrate surface side, recording and reproduction are possible without being affected by dust attached to the medium surface, which is a more desirable form. Note that defects such as dust and scratches on the substrate surface opposite to the surface on which the medium is formed will cause the beam diameter on that surface to be sufficiently large if the substrate thickness is 1 kat or more. Therefore, it does not adversely affect recording and 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 array 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, the 5-rotation system becomes complicated and expensive, so it is not practical. A more desirable method is to provide a light guide groove on the substrate. When light enters a groove with the same diameter as the beam, the light is diffracted.As the beam center shifts from the groove, the spatial distribution of the intensity of the diffracted light changes.This is detected and the servo is set to direct the beam to the center of the groove. system can be constructed. Normal groove width is 0.6
~1.2 μm, its depth is i- of the recording/reproducing wavelength used.
The range is set to 7. The recording layer is therefore formed on the grooved substrate surface.

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

(Example) A naphthoquinone dye was deposited on a disk-shaped acrylic substrate with a thickness of 1.2rnvt by a resistance heating method to obtain a film with a thickness of 800A. The resistance heating boat material was Mo, and the degree of vacuum at the time of vapor deposition was 9×10−6 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 boat temperature 2
Sublimation started at 55°C, and the vapor deposition was carried out by fixing this temperature.

The deposition rate is IA/sc.

The decomposition temperature of this dye is 300°C or higher, which is sufficiently higher than the vapor deposition temperature.The absorption rate of this film is 35 cm when measured from the substrate side at a wavelength of 780 nm, and 29 cm when measured from the film surface side.
It was Chi.

The accompanying figures show the media thus formed. A dye film 20 is formed on the acrylic substrate 10.

This medium was irradiated with semiconductor laser light with a wavelength of 780 nm in the direction of arrow 30, condensed by an optical system (not shown). In this case, the laser beam power was 10 mW on the medium surface, the irradiation time was 500 nsec, and the linear velocity was 3 m/type. According to this record, holes (bits) with a diameter of approximately 1 μm are formed in one pigment film 20.
40 were formed. In addition.

The beam diameter of the laser beam on the medium surface is approximately 1.5 μmg. When the recorded bits were reproduced using a continuous laser beam of Q and 7 mW, a good reproduced signal was obtained.

Even when laser light was incident from the direction of arrow 50, similar recording and reproducing characteristics were obtained.

In this example, an example was shown in which a single layer of dye was used as the recording layer, but it could be used on the recording layer or between the recording layer and the substrate.

Metals, oxides, organic substances, etc. can be added depending on the purpose such as the protection 17 anti-reflection width. As a result of life tests conducted on the media of the present invention at high temperatures and high humidity, it was predicted that the media would have a lifespan of several years or more.

(Effects of the Invention) As is clear from the above examples, the optical information recording medium obtained by the present invention has high sensitivity.

It can be seen that it has excellent industrial advantages in that it is chemically stable and, in addition, it is easy to form a medium.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an optical information medium according to the present invention. In the figure, 10 indicates a substrate, 20 indicates a dye film, 30.50 indicates a light incident direction, and 40 indicates a hole.

Claims (1)

[Claims] In an optical information recording medium in which a recording layer is provided on one or both sides of a substrate and information is recorded and read by a laser beam, the recording layer includes a chemical structural formula, a mathematical formula, a chemical formula, a table, etc. An optical information recording medium characterized by forming an organic thin film mainly composed of naphthoquinone dyes represented by ▼ and ▲numeric formulas, chemical formulas, tables, etc.▼.