JPS60150243A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled optical information recording medium which is highly sensitive and chemically stable by forming an organic thin film consisting essentially of a specified naphthoquinone pigment as a recording layer. CONSTITUTION:A naphthoquinone pigment expressed by the formula (halogen- substituted 6,2'-, 7,2''-dithio-5,8-bisanilino-1,4-naphthoquinone) is deposited on one or both surfaces of a substrate by vapor deposition or solvent coating. The medium has large absorption from the visible region to the near-infrared region, and is suitably used for recording regeneration by laser light. The peak absorption wavelength can be changed, and the sensitivity of the medium can be enhanced by providing an electron absorbing group such as a nitrile group, a nitro group, a carbonyl group, a carboxyl group, and a halogen to the 2, 3 position of the naphthoquinone pigment, or by adding an alkyl group, an alkoxyl group, and a halogen to the benzene ring of the naphthoquinone pigment.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical recording medium on which information can be recorded and reproduced using the inventive laser beam, and more specifically, recording is performed using changes in the state of matter caused by light energy. Related to optical information recording media.

(Prior Art) 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 Ss. 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. (,Te,
There is a problem in that the substances (As, Se, etc.) exhibit toxicity.

Although Te oxide is stable (compared to To 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 sensitive media, but because of its multilayer structure, it requires a large number of film formations, and because the repeated reflection interference greatly depends on the thickness of each layer, The disadvantage is that the 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. A compatible medium is, for example, as disclosed in JP-A-55-161690, in which polyvinyl acetate, which is a polymeric 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 squarylium dye is formed by vapor deposition is disclosed in JP-A-56-46221. 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.

(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. Indicates halogen such as bromine and iodine, where n is 1
~10 integer. ) is characterized by the formation of an organic thin film containing naphthoquinone dye as the main component.

(Theory F!A regarding the structure of the invention) Non-dye (halogen-substituted 6.2 +, 7,2-dithio-5,8-bisanilino-1,4-su7) represented by the above general formula Non) 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 substantially match. This can be accomplished by adding a substituent to the above naphthoquinone dye. For example, by adding an electron absorbing group such as a nitrile group, nitro group, carbonyl group, carboxyl group, or halogen to the 2.3-position of the naphthoquinone dye, the absorption peak wavelength can be shifted to the longer wavelength side. . Further, the absorption peak wavelength can also be changed by adding a furkyl group, an alkoxyl group, a halogen, etc. to the above-mentioned 7 non-alcohol dyes.

A synthesis example of the naphthoquinone dye used in the present invention is shown below. 2.3-dichloronaphthazarine 260W (1m
mot) is heated and dissolved in 65 mt of ethanol. This is called liquid A. Ethanol 20mtKKOH125++
y (2.2 mmoA) is dissolved and 270 μm of O-aminothiophenol (L2 mmoL) is added to convert it into a salt.

This is called liquid B. Add solution A to solution B and stir at room temperature for several hours (about 5 hours).

Crystals precipitate, but 1clIj there! ! Add acid to make it weakly acidic. After washing with water and drying, a crude product of 440 cm is obtained. Recrystallization in chloroform gives 6 in 80% yield.
．． 2-, 7.2-dithio-5,8-bisanilino-1
, 4-naphthoquinone CI) is obtained. This identification was performed by mass spectrometry, and 400 (100,0), 367 (4
4,7), 336 (2LO) (relative intensity is shown in parentheses), and it was confirmed that they were the target products.

Furthermore, the substance was identified through elemental analysis and confirmed to be the desired product.

(6) Next, 0.6v of Cono dye CI) is placed in 120ml of glacial acetic acid, 25 times the mole of Br2 is added, and the mixture is heated under reflux for 5 hours. Add reaction water and wash the precipitated precipitate with water and dry. When the soluble content was removed with chloroform, a residue of 1.121F was obtained. Since the spectra of the chloroform F solution and the residue matched, they are considered to be the same substance. When this dye was subjected to mass spectrometry, it was found that it was a mixture of compounds in which up to six hydrogen atoms in dye [I] were replaced with Br.

When the absorption spectrum of this dye was measured in chloroform, absorption peaks were observed at 620, 678, and 740 nm, and it was found that 2mlLX was at 740 nm.

The 7-toquinone 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. Also, this compound has a low thermal conductivity similar to general organic dyes, and its value is -i- to i of metal. 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. Although various substrate materials can be used, glass, AI, and synthetic resin are generally preferred. Examples of synthetic resins include polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyetherimide, polysulfone, polycarbonate, and epoxy resin.Substrate shapes include disk, tape, and sheet shapes. It can be applied. When laser light is focused by a lens and irradiated onto a 7-toquinone dye film formed on a substrate, the dye film in the irradiated area is removed and pores are formed. The mechanism of this pore formation is not clear. However, it is thought to be due to melting and aggregation accompanied by evaporation (sublimation).It depends on the size of the hole formed, the focused diameter of the laser beam, the laser power, and the irradiation time, but it 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 cases, the thickness of the pigment film is 0.01 to 0.5μ
m, preferably 0.02 to 0.2 μm.

The information (holes) recorded in this manner is read out by detecting a change in the amount of reflected light or transmitted light from the medium. A method of detecting general 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 amount of light at this time is set to a low energy level that does not cause any shape change to the medium, and is T~-10- of the amount of light 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 are possible without being affected by dust attached to the medium surface, which is the more desirable mode (9). In addition, defects such as dust attached to the substrate surface opposite to the surface on which the medium is formed and scratches on that surface,
If the substrate thickness is 1 square inch or more, the beam diameter on that surface is sufficiently large so that it does not cause any negative effects on recording or reproduction.

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 rotation system becomes complicated,
Also, it is expensive and therefore not practical. More desirable is
This is a method of providing a light guide structure on a substrate. When light enters a groove about the diameter of a beam, it is diffracted. As the beam center shifts from the groove, the spatial distribution of the diffracted light intensity changes.
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 0.
The depth (10) is defined as 4-1.2 μm. 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-N
e, semiconductor laser, etc.

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

(Example) 6 bromine substituted 6
．． 2'-,7,2-dithio-5,8-bisanilino-1
, 4-7toquinone dye was vapor-deposited by resistance heating method,
A gray-colored film with a human thickness of O5 was obtained. Resistance heating port material is Mo
The degree of vacuum during vapor deposition was set to 4×10 −' 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.

The deposition rate was 0.5 A/II ee. It was confirmed that the film surface flatness of this dye was better than that of the unsubstituted dye. The absorption rate at a wavelength of 630 cm was measured to be 24%.

The accompanying figures show the media thus formed. A dye film 2o is formed on an acrylic substrate 10.

He − of wavelength 633■ is applied to this medium in the direction of arrow 3o.
Ne laser light was focused and irradiated with an optical system (not shown). In this case, the laser beam has a power of 10 mW on the medium surface.
+irradiation time 500 n5ec. With this record,
Pores (pips) 40 having a diameter of about 1 μm were formed in the pigment film 2o. Note that the beam diameter i of the laser beam on the medium surface is
1: approximately x, sμmφ. When the recorded pits were reproduced using a continuous laser beam of 0.7 mW, a good reproduced signal was obtained, and the S/N was 44 dB. Further, as a result of an accelerated life test of this medium, it was confirmed that the life span was 5 years or more.

This medium therefore has sufficient practical chemical stability.

As is clear from the above examples, the optical information recording medium obtained according to the present invention has excellent properties such as high sensitivity, strong chemical properties, and easy medium formation. It turns out that it has advantages.

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 the drawing]

The figure is a cross-sectional view of an optical information recording medium according to the present invention, in which lO indicates a substrate, 20 a dye film, 30 a light incident direction, and 40 a hole. (13) Procedural amendment (voluntary) Director General of the Patent Office 1, Indication of the case 1982 Patent Application No. 240346
No. 2, Title of the invention Optical information recording medium 3, Relationship to the amended person case Applicant: 5-33-1-4, Shiba 5-chome, Minato-ku, Tokyo Agent: 5-37 Shiba, Minato-ku, Tokyo 108 No. 8 Resident Mita Building 5, Detailed explanation of the invention column 6 of the specification subject to amendment, Contents of the amendment 1) In the 8th line of page 3 of the specification, the phrase "reverse reflection interference" has been replaced with "reverse reflection interference." ” he corrected. 2) In the first line of page 9 of the specification, the phrase "corresponding" is amended to read "corresponding." 3) Change the word “diffraction” on page 10, line 15 of the specification to “
Diffraction” is corrected. 4) Correct l'-630 mJ on page 11, line 20 of the specification to [630 nmj. 5) In the 5th line of page 12 of the specification, ``633MJ'' is corrected to ``633nmJ.''

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 has a general formula (wherein X is a halogen such as fluorine, chlorine, bromine, and iodine). and n is 1 to 1
It is an integer of 0. ) An optical information recording medium comprising an organic thin film containing naphthoquinone dye as a main component.