JPS62160283A - Rewriting type heat mode optical memory medium - Google Patents

Abstract

PURPOSE:To provide a rewriting type optical memory medium having high long-term recording holding stability and capable of enhancing recording contrast, by constituting said memory medium by providing a solid phase recording layer constituted of a spiropyrane compound alone on a substrate and further forming a light absorbing layer thereon. CONSTITUTION:An an information recording layer 12, 1, 3, 3-trimethylindolino-6'- hydroxybenzospiropyrane (HBPS) being a representative example of a spiropyrane compound is used and vapor-deposited on an acrylic resin substrate 11. Further, Te is vapor-deposited on the HBPS film in a thickness of 2000Angstrom to form a light absorbing layer 13. This memory medium develops a blue color under heating at 50 deg.C, and when the memory medium of this state is irradiated with ultraviolet rays, the reflectivity thereof at 600nm is reduced to 10% within 10min and saturated in this state. Herein, when the memory medium is irradiated with beam having a wavelength of 830nm from semiconductive laser, the reflectivity thereof at 600nm increases up to 40% and pit recording is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a rewritable optical storage medium, and more specifically, the coloring state of a photochromic organic material is changed by laser light irradiation, and the coloring state is changed by heat mode. This invention relates to an optical storage medium that enables recording to be rewritten by reversibly repeating the process.

BACKGROUND OF THE INVENTION With recent advances in laser technology, lasers that can focus light onto a minute spot have been developed. Recently, much research and development has been carried out on optical storage media that uses this laser light as a light source to record information on the medium.

Such optical storage media can be classified into fixed recording media, on which information can be written only once, and rewritable recording media, on which different information can be written on the same medium any number of times. Particularly well-known fixed recording media of the former type include, for example, Te thin films, Te-containing carbon disulfide, and plasma polymerized films, which are typified by hole-shaped write-once media created by the heat of semiconductor laser light, and those using lasers. There are optical recording media with holes made of organic material in which fluorescein is made into a thin film, and optical storage media for semiconductor lasers in which squarylium dye, PT, or Ni dithiolate dye is made into a thin film.

Known rewritable media include chalcogenide glass and Te oxide that utilizes amorphous-crystalline transition. In addition, organic photochromic optical storage media that utilize the photochromic properties of organic materials are also rewritable, and media in which spiropyran and fulgide compounds are dispersed and dissolved in a matrix such as a polymer are known.

There are two information recording methods: photon mode and heat mode.
There is a street. A heat mode recording method is generally used for chalcogenide glass, Te oxide, and the like. These rewritable media have the following problems.

- Due to the high transition temperature, high power lasers are required for the transition.

- There is a problem with the long-term stability of the recorded amorphous spots.

- Even if the film thickness is controlled and the interference conditions are optimized, the recording contrast is only about a few to 10%.

- Since the materials used are highly toxic substances containing As, Se, etc., there is a risk during manufacturing or public use.

This also results in increased costs for recovering waste materials.

Organic photochromic optical storage media generally use a photon mode recording method. Since the medium is dispersed in a matrix, the density of the storage medium is low and the recording contrast is low. Furthermore, recording molecules tend to move easily, resulting in poor recording pit stability.

Problems to be Solved by the Invention As explained above, various rewritable optical storage media have been developed, but they have not yet been put into practical use. A rewritable optical storage medium that has high long-term recording stability and can increase recording contrast has been a challenge for some time.

An object of the present invention is to provide a rewritable heat mode optical storage medium that solves the above problems.

Means for Solving the Problems In order to solve the above problems, the rewritable optical storage medium of the present invention includes a substrate, a solid phase recording layer provided thereon consisting of only a spiropyran compound, and an optical It consists of an absorbent layer.

According to a preferred embodiment of the present invention, the light absorption layer has a reflectance of approximately 50 to 60% for the laser light used,
Further, it is preferred that the thickness range is from 500 to 5000 angstroms, preferably from 1500 to 2000 angstroms.

In such a rewritable heat mode optical storage medium of the present invention, information can be recorded and read in heat mode, and information can be erased in photon mode.

A spin code method, a vapor deposition method, or a dipping method is used to form the recording layer.

As the substrate material, for example, various plastics well known in this type of media such as polycarbonate and acrylic resin, metals such as AI, or glass, etc. are used.

Further, as the spiropyran compound, one having a hydroxyl group in the molecule is used. Such compounds include 1.3.3-) dimethylindolino-6''-hydroxybenzopyrylospirane, 1.3.3-) dimethylindolino-6''-amino-7''-hydroxybenzopyrylospirane, Rospiran, 1゜3.3-trimethylindolino-8゛-
Bromo-5-chloro-7'-hydroxybenzopyrrillospirane, 1,3.3-)dimethylindolino-8'-furomorph'-hydroxybenzopyrrillospirane, 1,3
．． 3-) Tumethylindolino-5-chloro-6'-hydroxy-8'-methoxybenzopyrylospirane, 1.3
．． 3-) Dimethylindolino-8゛-formyl-7°-
Hydroxybenzopyrylospirane, 1,3.3-)rifthylindolino-6'-hydroxy-8'-methoxybenzopyrylospirane, 1.3.3-)samethylindolino-5-ditrophic-hydroxy Benzopyrillospiran, 1.3.3-) Limethylindolino 7'-Hydroxy-6'-nitrobenzopyrillospiran, 1.3.3
-) Limethylindolino-7'-hydroxybenzopyrylospirane, 1,3'3-trimethylindolino-8'-hydroxybenzopyrylospirane, and the like.

In the present invention, the information recording layer is a solid phase recording layer made of a single spiropyran compound. Therefore, it is possible to improve the poor contrast and instability of recording pits, which have been problems with conventional optical storage media using dispersed photochromic organic materials.

Furthermore, the optical storage medium according to the invention comprises a light absorption layer, which preferably has a reflectance of approximately 50-60% for the laser light used, so that, for example, 83%
Approximately 50 to 60 nanometers of semiconductor laser light with a wavelength of 0 nanometers
% configured to reflect.

Therefore, the light absorption layer of the optical storage medium of the present invention acts as a reflection layer and at the same time absorbs 40 to 50% of laser light.
It moderately heats the interface with the recording layer to enable information recording and reading in heat mode.

If the thickness of the light absorption layer is less than 500 angstroms, it cannot function as a reflective layer, while if it exceeds 5000 angstroms, the heat capacity becomes too large and adequate heating of the recording layer cannot be achieved. The pot becomes larger as it heats up.

The material of the light absorption layer has approximately 50% resistance to laser light with a wavelength of 750 angstroms to 1300 nanometers.
Materials with a reflectance of ˜60% are preferred, especially metallic materials such as tellurium and bismuth.

Recording and erasing of information using the medium of the present invention will be described below. When the initially transparent state is heated, the recording layer becomes colored.

When ultraviolet light is irradiated in this state, the reflectance decreases until it reaches a certain state and becomes saturated. When heated by irradiation with a focused laser beam, the reflectance increases and information is recorded. To erase the recorded information, UV light is irradiated again. The erasure of information can be seen as the reflectance decreases again. Therefore,
Using the medium of the present invention, information is recorded in heat mode and information is erased in photon mode.

EXAMPLES Hereinafter, the storage medium of the present invention will be specifically explained using examples.

Example 1 A storage medium having the configuration shown in FIG. 1 was manufactured. Information recording layer 1
2, representative examples of spiropyran compounds, 1.3.3-
) Using trimethylindolino-6°-hydroxybenzopyrylospirane (HBPS), this was applied to the acrylic substrate 11.
Vacuum level I Xl0-'Torr above.

The film was deposited at a heating temperature of 150° C. to a thickness of 2,000 yen. Further, on this HBPS film, 20% Te is added as a light absorption layer 13.
00 people were deposited.

When observed from below the acrylic substrate, this storage medium shows Te
The result was a colorless and transparent glass-like thin film with a visible metallic luster on the surface. When heated at 50℃, it becomes blue (maximum absorption wavelength: λn, ax
= 600 nm, reflectance 40%).

Ultraviolet light (wavelength 365 nm) is applied to the storage medium in this state.

When irradiated with an ultra-high pressure mercury lamp with an output of 500 W, the reflectance at 600 nm decreases to 10% in 10 minutes, and saturates in that state. Here, a beam of semiconductor laser light with a wavelength of 830 nm (beam diameter 1.6 μmφ, output 3.2 mW,
When irradiated with a pulse width of 1 μ5 ec), the reflectance at 600 nm increased to 40%, and pit recording was performed.

Next, when these pits were irradiated with ultraviolet light, the reflectance decreased again and the pits were erased.

Heat mode recording using the semiconductor laser and photon mode recording erasing using ultraviolet light could be repeated.

Example 2 HBPS was dissolved in acetone, a recording layer was provided by a spin code method, and 2000 Ni was further vapor-deposited thereon to produce a medium. As a result, a medium having the same reflectance as Example 1 was obtained. Information recording and erasing of information were also the same as in Example 1, and repeatability was observed.

Example 3 A medium was prepared by forming a film in the same manner as described in Example 1.2 using the compounds listed in Table 1 below. 2000 pieces of Te were deposited on the light absorption layer. The output and pulse width of the semiconductor laser used for information recording are also shown in Table 1. As a result, the same results as in Example 1.2 were obtained.

Table 1 Table 1 (Continued) As described in detail of the invention, the optical storage medium according to the present invention can be manufactured using a simple method and apparatus such as a spin code method and a vacuum evaporation method.

Furthermore, since heat mode can be used as the recording principle for recording pits, very highly sensitive recording can be performed. Moreover, it has rewritability as shown in the embodiment.

Since the information recording layer of this optical storage medium is a solid layer made of a single spiropyran compound, the recording medium density can be increased, and as a result, the recording contrast can be increased. Furthermore, since the recording molecules are fixed, the stability of the recording pits is also good.

As described above, the optical storage medium according to the present invention is an optical storage medium in which information can be effectively recorded in heat mode.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical storage medium according to the present invention. (Main reference numbers) 11...Substrate, 12...Recording layer, 13...Light absorption layer

Claims (5)

[Claims] (1) A rewritable heat mode optical storage medium characterized by having a substrate, a solid phase recording layer formed solely of a spiropyran compound provided thereon, and further a light absorption layer. (2) The above-mentioned light absorption layer has approximately 5
The rewritable heat mode optical storage medium according to claim 1, having a reflectance of 0 to 60%. (3) The rewritable heat mode optical storage medium according to claim 1 or 2, wherein the light absorption layer has a thickness of 500 to 5000 angstroms. (4) The rewritable heat mode optical storage medium according to any one of claims 1 to 3, wherein the spiropyran compound is selected from spiropyran compounds containing a hydroxyl group. (5) The rewritable heat mode storage medium according to any one of claims 1 to 4, characterized in that information recording and reading from the recording layer is performed in heat mode.