JPS60197954A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled information recording medium capable of recording and reading by a laser beam and having high sensitivity, chemical stability, and excellent durability by providing an organic thin film consisting essentially of a specified naphthoquinone pigment on the surface of a substrate as a recording layer. CONSTITUTION:Since a naphthoquinone pigment shown by the formula (5,8- bisanilino-6,2',7,2'-disulfonyl-1,4-naphthoquinone) has large absorption in the near- infrared region and is stable even in a high-temp. and high-humidity environment, the pigment is vapor-deposited under vacuum on a substrate 10 of glass, Al, plastics, etc. to form a pigment film 20 by utilizing said characteristics. A semiconductor laser is irradiated to the obtained recording medium in the direction as shown by the arrow 30 and recorded to form a bit 40 having about 1mu diameter. The recording can be carried out from the substrate 10 side in the direction shown by the arrow 50. The high-sensitivity and stable recording medium is easily obtained in this way.

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 a laser beam, and more specifically, relates to an optical recording medium that can record and reproduce information using laser light, and more specifically, it relates to an optical recording medium that uses a change in the state of a material due to light energy. The present invention relates to an optical information recording medium for recording.

(Prior Art and its Problems) Conventionally, Te alloys, Te oxides, bubble-forming media, organic dyes, and the like have been used as this type of optical recording medium.

Te alloy is used as a solid solution alloy of Te and semiconductors such as As and 8e. 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. Material (Te, A
s, 8e, etc.) are toxic.

Te oxide is more stable than Te alloys, but its optical properties1, such as absorption and reflectance, depend sensitively on the oxidation state.Therefore, the oxidation state of this medium must be strictly controlled during medium formation. It has the following drawback.

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 the absorption rate of light and achieve high sensitivity. Therefore, this medium is currently the most Although it is one of the highly sensitive media, the film thickness must be strictly controlled during film formation because the multilayer structure requires many film formations and the repeated reflection interference depends greatly on the thickness of each layer. It has the disadvantage that it cannot be used.

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. 55-16169Q, in which polyvinyl acetate, which is a polymer resin, is mixed with polyester yellow μ- as a dye using a solvent, and the mixture is coated onto a substrate by a spin coating method. However, in general, for compatible media, the media formation method is limited to solvent coating, and when using resin 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 squarylicum 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 side 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 7-toquinone dye, which is represented by white color.

(Detailed explanation of the structure) So7toquinone dye (5,8
-Bisanilino-6,2',72'! -disulfonyl2-1,4-naphthoquinone) exhibits large absorption in the near-infrared region and is suitable for recording and reproducing using semiconductor laser light.

An example of the synthesis of this dye is shown below.◎2.3-dichlorona7
26omg (1mmol) of tazarin and 65ml of ethanol
Heat and dissolve in 1 ◎ Use this as liquid A with 20 ethanol
m1! 270 mg (2.2 mmol) of 0-7 minothiophenol dissolved in 125 mg (2.2 mmol) of KOH was added to convert the mixture into salt. Use this as liquid B.
Add solution A to solution B and leave it at room temperature for several hours (about 5 hours).
Stir. Crystals will precipitate, but add concentrated hydrochloric acid to make them weakly acidic and pass. After washing with water and drying, 440 mg of crude product is obtained. Recrystallization in chloroform yields 5,8-quinone with a yield of 80ts as shown by the chemical structural formula below.
is obtained. This identification was performed by mass spectrometry, with 400 (
100,0), 367(44,7).

We obtained data of 336 (22,0) (relative intensity in parentheses) and confirmed that it was the target compound by elemental analysis. Next, 200 mg of compound [I] was added to 50 ml of glacial acetic acid! After the reaction, add 230 mg (about 4 times the mole) of 30% hydrogen peroxide solution and heat and stir under reflux for 2 hours.
The reaction solution is added to water, and the resulting precipitate is filtered, washed with water, and then dried. The product was extracted with chloroform and chloroform-
separated by silica gel column chromatography,
Naphthoquinone dye (5,8-bisani!) used in the present invention
j/-6,21゜7.211-disulfonyl-1,4-
7 toquinone) was obtained. This pigment was identified using mass spectrometry and elemental analysis, and was confirmed to be the desired product.

When the absorption spectrum of this dye was measured in chloroform, absorption peaks were observed at 510, 685, 744, and 820 nm, and λmax was found to be 820 nm. The 7-toquinone dye is stable even under relatively high vortex and high humidity environmental conditions, and does not show deterioration due to air oxidation like Te alloys. This means that it can withstand long-term use without a protective film.Also, like general organic dyes, this compound has low heat diffusion within it, which reduces the temperature of the medium in the light irradiated area. A recording medium that can efficiently increase the 0 concentration is formed by attaching the above-mentioned 7-toquinone 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 and U9 synthetic resin are generally preferred.Synthetic resins include polymethyl methacrylate (pMMA) and polyvinyl chloride 2.
When the naphthoquinone dye film formed on the substrate is irradiated with a laser beam focused by a lens, The dye film in the irradiated area is removed and holes are formed. The mechanism of this pore formation is not clear, but it is thought to be caused by melting and aggregation accompanied by evaporation (sublimation).The size of the pores formed depends on the focused diameter of the laser beam, laser power, and irradiation time. However, it is roughly 0.
The thickness is preferably 2 to 3 μm. The laser energy required to form such a hole is small1, so 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 film thickness of the pigment film is 0.01 to 0.5 μm, preferably 0.0 μm.
It is 2 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 amount of light at that time is a weak energy that does not cause any shape change to the medium.

The direction of incidence of light during recording and playback is two directions, one on the medium surface and one on the substrate surface.For single-layer media such as this example, both directions can be used. This is a very desirable form because it allows recording and playback without being affected by the dust that has adhered to it. Defects such as scratches on the surface do not adversely affect recording and reproduction if the substrate thickness is 1 mm or more because the beam diameter on that surface is sufficiently large.

Information is recorded as a series of holes. The hole array generally forms a large number of concentric or spiral tracks. When performing reproduction, it is necessary for the light beam to accurately track the hole array of a specific track. One way to achieve this is to improve the accuracy of the rotating mechanism by using air bearings or the like. However, in this case, the rotation system is 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 about the diameter of the beam, the original is diffracted. As the beam center shifts from the groove, the spatial distribution of the intensity of the diffracted light changes.The servo system can be configured to detect this and direct the beam to the center of the groove.Normally, the width of the groove is 0. 6
Its depth is ~12 μm. 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) 1. '5.
8-bisanilino-6,2',7,211-disulfonyl-1,4-naphthoquinone dye is vapor-deposited by a resistance heating method,
The zero-resistance heating boat material from which a film with a thickness of 1000X was obtained was made of Mo, and the degree of vacuum during vapor deposition was 9 x 10 '' Torr or less, and the zero substrate was left naturally at room temperature, so that the substrate temperature did not increase due to vapor deposition. By gradually raising the robot temperature, which was barely noticeable, the dye melted at 250°C, and was fixed at this temperature for vapor deposition. The deposition rate is atX/(8) ◎The decomposition temperature of this dye is 310° C. or higher, which is sufficiently higher than the deposition temperature. The absorbance of this film was measured at a wavelength of 830 nm and was 30-.

The attached figure shows the medium formed in this manner. A dye film 2o is formed on an acrylic substrate lo.

This medium was irradiated with semiconductor laser light having a wavelength of 830 nm in the direction of arrow 3o, condensed by an optical system (not shown).

In this case, the laser beam has a power of 10 mW on the medium surface.
, irradiation time 500nac, linear velocity 3m/(5)・
According to this record, holes (pits) 40 with a diameter of about 1 μm were formed in the pigment film 20. Note that the beam diameter of the laser beam on the medium surface is approximately 15 μml.
When the recorded pits were reproduced as continuous light of 7 mW, a good reproduction signal was obtained.Even when the laser beam was incident from the direction of the arrow 50, similar recording and reproduction characteristics were obtained.

This example shows an example in which a single dye layer is used as the recording layer, but metals, oxides, organic substances, etc. may be added on top of the recording layer or between the recording layer and the substrate depending on the purpose of protection, reflection amplification, etc. can do. Furthermore, 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 is highly sensitive and chemically stable, and in addition, the medium is easy to form. It can be seen that it has excellent industrial advantages.

[Brief explanation of the drawing]

The figure is a cross-sectional view of an optical information recording medium according to the present invention. In the figure, lO indicates a substrate, 20 indicates a dye film, 30.degree. 50 indicates a light incident direction, and 40 indicates a hole.

Claims (1)

[Scope of 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 using a laser beam, the recording layer mainly containing a naphthoquinone dye represented by the chemical structural formula. An optical information recording medium comprising an organic thin film formed thereon.