JPS6063744A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain a chemically stable record with high sensitivity by providing a recording layer on one or both sides of a base plate and forming a thin org. film consisting essentially of a specific naphthoquinone dye as a recording layer which records information by a laser beam. CONSTITUTION:This optical information recording medium which is provided with a recording layer on one or borh sides of a base plate and records and reads information by a laser beam is formed with the org. thin film consisting essentially of the naphthoquinone dye expressed by the chemical structural formula I as the recording layer. The sensitivity of the medium is increased preferably by matching approximately the absorption peaks of the recording wavelength and the recording layer and therefore a substituent is added to the naphthoquinone dye. The naphthoquinone dye is stable under the environmental conditions of relatively high temp. and high humidity and does not show the deterioration by oxidation in air unlike a Te alloy. Said compd. has low heat conductivity and the value thereof is 1/10-1/100 the value of metal. The diffusion of heat in the medium during laser light recording is thus decreased and the medium temp. in the light irradiated part is efficiently elevated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light, and more particularly to an optical information recording medium in which information is recorded using changes in the state of multiple substances caused by light energy. Regarding the medium.

Conventionally, Te alloys, Te oxides, bubble-forming media, organic dyes, and the like have been used as optical recording media of this type.

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 deteriorates in many parts when left in the air. Material (Ta,
There is a problem in that the materials (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 increases light absorption through repeated reflection interference to 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 polymer resin, is mixed with polyester yellow as a pigment using a solvent, and formed on a substrate by a spin 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 medium, for example, a medium in which a squarylium dye is layered by vapor deposition is disclosed in Japanese Patent Laid-Open No. 46221/1983. Although this dye has relatively large absorption in the near-infrared wavelength region, which is the oscillation wavelength of a semiconductor laser, its recording sensitivity is lower than that of 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 information recording medium.

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 forming an organic thin film.

Naphthoquinone dye (6,2
'□ 7.2''-dithio-5,8-bisanilino-1
, 4-naphthoquinone) has large absorption in the visible to near-infrared region, and is suitable for recording and reproducing using laser light. In order to increase the sensitivity of the medium, it is necessary to use a recording layer that exhibits a large absorption rate. In order to increase the absorption rate, it is desirable that the recording wavelength and the absorption peak of the recording layer coincide with I5.

This is accomplished by adding substituents to the naphthoquinone dye. For example, by adding an electron absorbing group such as a nitrile group, nitro group, carbonyl group, carboxyl group, . can. The absorption peak growth can also be changed by adding a benzene ring dialkyl group, alkoxyl group, norogen, etc. to the naphthoquinone dye.

The naphthoquinone dye used in the present invention is synthesized as follows. 2.3-dichloronaphthazarin z6owqo
mmal) to ethanol #65mI! Heat and dissolve.

This is called liquid A. 125 KOH in 20ml ethanol
"Dissolve F (2,2 mmo/) and Oo-aminothio 7
! Add / -, &270'9 (2,2mm01) and change to salt. This is called liquid B. Add solution A to solution B and stir at room temperature for several hours (about 5 hours).

Crystals will precipitate, but add concentrated hydrochloric acid to make them weakly acidic and filter. After washing with water and drying, a crude product of 440η is obtained.

Recrystallization in chloroform yields 6.2'-
17,2″-dithio-5,8-bisanilino-1,4-
Naphthoquinone is obtained. This identification was performed by mass spectrometry, and 400 (100,0), 367 (44,7'13
Data of 36 (22,0) (the numbers in parentheses indicate relative intensity) were obtained, and it was confirmed that this was the desired product. Furthermore, the substance was identified through elemental analysis and confirmed to be the desired product.

When the absorption spectrum of this dye was measured in chloroform, an absorption peak was observed at 607,667.726-m, and 1 m (LX was 726 tLm), indicating no deterioration due to air oxidation. This means that it can withstand long-term use.

In addition, this compound has a low thermal conductivity similar to general organic dyes, and its value is , t ~ 1]0 1■ of a metal. Therefore, the heat conductivity in the medium during laser beam recording is As a result, the temperature of the medium in the light irradiation section can be increased efficiently.

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 types of Fi can be used as the substrate material, but glass, Al, and synthetic resin are generally preferred. As the synthetic resin, polymethyl methacrylic, tape shape, and sheet shape can be used. 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 1/- laser beam, the laser power, and the irradiation time, but is approximately 0.2
It is desirable that the thickness is 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 case, the thickness of the pigment film is 0.01 to 05 μm, preferably 0.02 μm.
~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 sight at that time is set to a weak energy level that does not cause any lateral shape changes to the medium, and is 5"10" as the sight during normal recording.

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 can be performed without being affected by dust that has landed on the medium surface, which is a more desirable form. Note that defects such as hazardous dust that has adhered to the surface of the substrate opposite to the surface on which the medium is formed and defects such as scratches on that surface will cause the beam diameter on that surface to be It is sufficiently large so that it does not adversely affect recording and playback.

Information is recorded as a series of holes. The rows of holes generally form multiple concentric or spiral trunks. When regenerating, the light beam needs to precisely track the row of holes in a particular trunk. One way to achieve this is to increase the fWJIN of the rotating mechanism by using an air bearing or the like. However, in this case, the 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 an ocean that is about the diameter of the beam, it is diffracted. If the beam-to-beam distribution is different, 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 06 to 12 μm, and the depth is set in the range of 100 to 1 μm of the recording/reproducing wavelength used. The recording layer is therefore formed on the grooved substrate surface.

The laser beam applied to the optical information recording medium of the present invention is
The dye must be selected in consideration of the absorption peak wavelength of the dye. Applicable lasers include Ar ion, He-
Examples include Ne, a semiconductor laser, and the like.

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

On an acrylic substrate on a 12mm thick disc,
A 2"-dithio-5,8-suanilino-1,4-naphthoquinone dye was vapor deposited using a resistance heating method to obtain a film with a thickness of 985X. The resistance heating boat material was MO, and the degree of vacuum during vapor deposition was The temperature was set to 9×10.
The dye melted at 30° C. and was fixed at this temperature for vapor deposition.

The deposition rate was 5 A/sec.

Note that the decomposition temperature of this dye is 310° C. or higher, which is sufficiently higher than the vapor deposition temperature. The absorption rate of this film is 6337L77 at wavelength
I measured it at 1, but it was 29 inches.

The attached figure shows a niece body formed in this way. A dye film 20 is formed on the acrylic substrate 10. l-1 with a wavelength of 633 nm from the direction of this media talk mark 30
e→e Laser light was focused and irradiated with an optical system (not shown). In this case, the power of the laser beam on the medium surface is ] 0
y71W, irradiation time 5007L, linear speed 3m/scc
It is. According to this record, about 1 ltm in the pigment film 20
Holes (bits) 40 with front and rear diameters were formed. Note that the beam diameter of the laser beam at the light body surface is approximately 1.5 μmp. When the recorded bits are reproduced using a continuous laser beam of 1 mW, a good reproduced signal is obtained, and the S/N is 1d40d1.
．． 3 (bandwidth 30KI-Jz).

As is clear from the above examples, the optical information recording medium obtained by the present invention has the excellent advantages of being highly sensitive and chemically stable, as well as being easy to form. I understand that.

Although this example shows an example in which a single layer of dye is used as the recording layer, metal,
Oxides, organic substances, etc. can be added depending on purposes such as protection and reflection amplification.

[Brief explanation of drawings]

The figure is a sectional view of an optical information recording medium according to the present invention, in which 10 is a substrate, 2o is a dye film, 3° is a light incident direction, and 40 is a hole. Procedural amendment (spontaneous) ↑1' Palace of the Commissioner of Corrections], Indication of the case 1981 Percentage Application No. 153898 2, Title of the invention Optical information recording medium 3, Person making the amendment Relationship to the case Applicant 33-1 (423) Shiba 5-chome, Minato-ku, Tokyo NEC Corporation Representative Tadahiro Sekimoto 4, Agent 108 Sumitomo SanfB Building (Renshiku Japan) 1-137-8 Shiba 5-chome, Minato-ku, Tokyo 108 (Patent Department of Denki Co., Ltd.) In Column 6 of the detailed explanation of the invention in the specification, Contents of amendment 1, page 5, line 9 of the specification, the phrase "It is necessary." has been replaced with "It is necessary." Amendment 2, Specification, page 7, No. 6
In the first line, the phrase ``Takateru'' is corrected to ``To make it high.'' 3. In the 9th shell of the specification, line 12, the word "trunk" is corrected to "truck." 4. In the 10th page of the specification, line 14, the phrase "on a disc" is corrected to "disc-shaped." 5. Details Sergeant 10th Member 20th? Replying to ``Gradually'' instead of ``Gradually''

Claims (1)

[Claims] 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, wherein the recording layer and [7] contain a naphthoquinone dye represented by the chemical structural formula. An optical information recording medium characterized by forming an organic thin film as a main component.