JPH02187390A - Erasable optical information recording medium, and method of recording and erasing information - Google Patents

Abstract

PURPOSE:To conduct recording and erasing at every recording bit efficiently by quickly heating and quenching an irradiation spot partially by the irradiation of intense laser beams, forming a protruding section, heating and annealing bumps up to a gummous state by the irradiation of feeble laser beams and decreasing the bumps. CONSTITUTION:A recording medium 2 is shaped onto a transparent substrate 2. The medium is irradiated with laser beams oscillated by the absorption wavelength of a pigment from the substrate side or the medium surface side, thus forming a bump 3 onto the surface of the medium, then recording information. Recording written once is erased by irradiating the bump with laser beams so that the intensity of laser beams is made feeble than that at the time of writing and the temperature of an irradiating section is made slightly higher than that of the medium. Information recorded is regenerated in such a manner that the surface of the medium is irradiated with laser beams having extremely feeble intensity so that the medium is not brought to the temperature or more, and the presence of the bump and the difference of shape are detected as the difference of reflectivity. A reflecting layer may further be shaped onto the surface of a medium layer in order to increase the reflectivity of the surface of the medium as required.

Description

DETAILED DESCRIPTION OF THE INVENTION Part 1: The present invention relates to a novel optical information recording medium and a recording/erasing method thereof. More specifically, it is an organic polymer/organic dye mixed recording medium that can efficiently record optical information and erase each recorded bit by changing its shape when heated.

Conventionally, many optical recording media using organic dyes have been proposed (for example, Japanese Patent Laid-Open No. 61-163891.61-268).
487, 62-56191.62-122787.62
-39286.63-72594).

In addition, many optical recording media using a combination of organic dye and organic polymer have been proposed (for example, JP-A-62
-90291.63-62794.63-191691
).

However, the recording principle of these recording media is
It is based on an irreversible change in the shape of the recording medium (often bit formation) caused by the heat generated by the absorption of light (often laser light) by a dye, making it extremely difficult or impossible to erase the record. Met.

That is, in the case of a medium containing only dye molecules, since recording is performed by forming bits accompanied by vaporization and dispersion of the dye, it is impossible to erase the bits once formed. In addition, in the case of a mixed system of polymer and dye, recording is performed by forming bits by flowing deformation of the polymer, so in order to erase the recorded bits once formed, the entire track including the recorded bits must be heated by laser beam irradiation. After that, it was necessary to erase the information by slowly cooling it, or by heating and slowly cooling the entire surface of the recording medium. In addition, another conventional technology (
JP-A-60-69846.63-136337.63-
136338, 63-164042), a recordable/erasable medium consisting of an expansion layer that is heated and expanded by laser beam irradiation to form a dome-shaped protrusion (bump), and a retention layer that maintains this shape is disclosed. Proposed. When recording on this medium, laser light is irradiated at the absorption wavelength (input 1) of the dye mixed in the expansion layer in advance, so that the expansion layer forms bumps and the retention layer maintains this shape. do. In addition, when erasing recorded bumps, the absorption wavelength of the dye mixed in the retention layer in advance is λ.
In step 2>, laser light irradiation is performed to heat the holding layer to a temperature of 7 g or more so that it becomes difficult to maintain the bump shape. According to the disclosed method, recording and erasing can certainly be performed reversibly, but the following problems also occur. That is, there are problems such as a) the need for a two-wavelength laser for recording and erasing, b) the need for two types of dyes with different maximum absorption wavelengths, and C) the complicated layer structure of the recording medium. In response to organic optical recording media that have these problems, recording and erasable recording media that utilize phase change of inorganic crystals in a thermal mode have been proposed. However, since these are inorganic materials, simple film forming methods such as coating and casting cannot be used, and relatively complicated and expensive film forming methods such as vacuum evaporation and sputtering must be used.

In view of these circumstances, the inventors of the present invention have conducted intensive studies on optical recording media that are soluble in organic solvents, can be coated, and are recordable and erasable, and have developed a polymer with the following thermal properties. The present inventors have discovered that a medium composed of an organic dye can serve as an optical information recording medium that does not have the above-mentioned problems, and have completed the present invention.

The optical recording medium according to the present invention contains an organic medium [P] that can reversibly change into a resin state at low temperatures and a rubber state at high temperatures.
An optically homogeneous medium containing a dye [D] that exhibits high reflective properties, and the irradiation spot is irradiated with a strong laser beam that oscillates at a wavelength corresponding to the absorption wavelength of the dye [D]. Protrusions (bumps) can be formed by partially heating and cooling rapidly, and by heating and slowly cooling the bumps to a rubber state with weak laser light irradiation,
It is a medium that can reduce the bump.

In addition, the optical recording/erasing method according to the present invention includes: 1) irradiating the irradiated spot with a strong laser beam that oscillates at a wavelength corresponding to the absorption wavelength of the dye [D] in the medium to partially sharpen the irradiated spot; A process of recording information by heating and rapidly cooling to form a bump, and 11) heating and slowly cooling the bump to a rubber state by irradiating the formed bump with a weak laser beam. This process consists of erasing information by reducing bumps.

The principle of recording and erasing of the present invention will be explained in more detail with reference to the figures below. A recording medium (2) according to the present invention is formed on a transparent substrate (1) (FIG. 1a), and a laser beam oscillated at the absorption wavelength of the dye [D] is applied to the medium from the substrate side or the medium surface side. By irradiating it, bumps (
3) and records information (Figure 1-b).

a b C Once a record has been written, it is erased by lowering the intensity of the laser light than during writing and irradiating the bumps with the temperature of the irradiated part slightly higher than the Tg of the medium (Figure 1 -c). Reproduction of recorded information is carried out by irradiating the medium surface with a very weak laser beam that does not allow the medium to weigh more than 7g, and detecting the presence or absence of bumps and differences in shape as differences in reflectance. be exposed. Furthermore, if necessary, a reflective layer may be further provided on the surface of the medium layer in order to increase the reflectance of the medium surface.

The substrate (1) used in the present invention is not particularly limited as long as it is transparent. Specific examples include Hon 9 Liquor Binate, Hon 0 Su (ethicinte 1 futa tote), Ne 0 Su (methin methacrylate), and glass plates.

The organic medium [P] used in the present invention is one that transitions from a resin state at low temperatures to a rubber state at high temperatures, and preferably has a transition temperature [Tg] in the range of 60 to 150°C. When Tg is lower than 60° C., there is a high possibility that bumps in the recording portion will decrease during storage of the medium. Also, Tg is 15
If the temperature is higher than 0° C., it becomes difficult to slowly cool the medium during erasing records, resulting in poor recording and erasing characteristics. Further, in the medium [P] of the present invention, a crosslinked structure is introduced as necessary in order to prevent irreversible flow deformation and bit formation due to laser beam irradiation. Media exhibiting these characteristics [P
] is a medium in which soft molecular chains [or segments] that exhibit elastic properties at room temperature and hard molecular chains [or segments] that exhibit high elastic modulus are microdispersed. Specific examples of media with these characteristics include styrene-butadiene copolymers, transpolyisoprene, polynorbornene, which are known as shape memory resins,
Mention may be made of polyurethanes and crosslinked products thereof. As a film forming method for these media [P], when these media are soluble in organic solvents, a casting method or a spin coating method is used.

In addition, in the case of insolubility or sparingly soluble in organic solvents, film formation by heating and melting is possible. A suitable film thickness is 0
．． 1 to 5 μm1, more preferably 0.2 to 2 μm
m range can be adopted.

As the dye [D] used in the present invention, the above-mentioned medium [P
] Any material can be used as long as it has a high affinity for and is stable against heat and laser light. Preferred specific examples of the dye [D] include phthalocyanine, naphthalocyanine, naphthoquinone, nickel dithiol complex, and polymethine dyes represented by cyanine. Among these, particularly preferred dyes are those in which the aromatic nucleus is substituted with an alkyl group, an aryl group, or an aryloxy group having 2 to 20 carbon atoms.
Phthalocyanine derivatives and naphthalocyanine derivatives that are soluble in organic solvents and whose central metal has 2 to 20 carbon atoms.
is a naphthalocyanine derivative substituted with an alkyloxy group, an alkylsiloxy group, or an arylsiloxy group and soluble in organic solvents. These dyes are mixed with the medium [P] to constitute the recording medium of the present invention. The mixing ratio of the dye [CD] to the medium [P] is not particularly limited, but the weight ratio of [CD] to [P] is 2 to 50.
% is preferred.

When recording optical information using the above-mentioned recording medium of the present invention, laser light irradiation is performed so that the temperature is higher than the resin→rubber transition temperature of the medium [P] constituting the recording medium, as described above. , a bump is created on the surface of the medium, and the shape of the bump is maintained by the subsequent rapid cooling process. In addition, when erasing the bumps (information) formed by the above method, laser light irradiation is performed at a temperature slightly higher than the resin→rubber transition temperature of the medium [P] constituting the medium, and then reducing the bumps by a slow cooling process;
Erase information. The laser light source used for recording information depends on the dye [D] used, but when using a near-infrared dye, for example, a gallium/substrate semiconductor laser can be used, and when using a visible light-absorbing dye, a , helium neon lasers, argon lasers, ruby lasers and dye lasers can be used. When recording information, these lasers have an output of 5 to 30 mW, preferably 7 to 20 mW.
Irradiate for 5-0, 1H seconds. If the laser irradiation conditions are milder than the above range, recording will be insufficient, and if the laser irradiation conditions are more severe than the above range, the medium will undergo flow deformation, making subsequent erasing impossible. On the other hand, when deleting information,
The above laser beam is used with an output of 1 to 10 mW, preferably 3 to 7 mW, and a power of 0.5 mW. Irradiate for 1 to 20 microseconds.

As described above, the basic principle of the recording method of the present invention is to utilize the unique thermal properties of the polymer [P] to read changes in reflectance due to the formation and disappearance of bumps at the light irradiated area. Therefore, the recording medium of the present invention is reversible and erasable because the dye in the recording area does not evaporate or disperse. Furthermore, since the recording medium of the present invention can be easily formed into a film by any of spin coating, casting, and heating and melting, it also has an industrial advantage of being inexpensive. Hereinafter, the present invention will be explained in more detail according to examples.

Example 1 Shape-memory resin consisting of sugeton-futashiniji copolymer [trade name: Asmar (manufactured by Asahi Kasei Corporation)]
] 11g Tertiary-butyl group-substituted vanadium phthalocyanine [Product name: NIR-12 (Sansui Synthetic Chemical! Ri) 0.
3 g and 26 g of toluene were mixed to form a homogeneous solution.

After this solution was applied onto a glass substrate, the solvent was evaporated in a dry chamber to form a film. The film was coated with 830n
When a semiconductor laser beam with an oscillation wavelength of m and an output of 10 mW at the substrate surface was irradiated as a pulse signal of I MHz, the formation of a clear bump with a diameter of 1.5 μm was observed on the medium surface. . Subsequently, when this recording spot was irradiated with the same laser beam as a pulse signal of 0.2 Hz with an output power of mW, the above-mentioned bump disappeared. From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

Instead of using anine [NIR-12],
A recording medium was prepared in the same manner using -meta-7crystalline oxidyloxyfluoroxyfluorinated cyanine. When this medium was irradiated with semiconductor laser light under the same conditions as in Example 1, the formation of clear bumps with a diameter of 1.5 μm was observed. When this recording spot was irradiated with the same laser beam as an IMHz pulse signal with an output of 10 mW, the bumps mentioned above disappeared.

From this result, it was found that the above-mentioned recording medium could be an optical information recording medium capable of recording and erasing information.

Example 2

Claims (4)

[Claims] (1) A pigment [P] that exhibits high reflective properties is contained in an organic medium [P] that can reversibly change from a resin state at low temperatures to a rubber state at high temperatures.
An optically homogeneous optical recording medium containing dye [D], in which the irradiation spot is partially rapidly heated by irradiation with strong laser light that oscillates at a wavelength corresponding to the absorption wavelength of the dye [D]. - An optical recording medium that can form protrusions (bumps) by rapid cooling, and can reduce the bumps by heating and slowly cooling the bumps to a rubber state by irradiating weak laser light. (2) The organic medium [P] described in item 1 above shows no flow deformation upon heating, and has a transition temperature from a resin state to a rubber state [glass transition point (Tg)] in the range of 60 to 150°C. An optical recording medium according to claim 1, characterized in that: (3) The organic medium [P] described in item 1 above is styrene-
The optical information recording medium according to claim 1, wherein the optical information recording medium is selected from butadiene copolymer, transpolyisoprene, polynorbornene, polyurethane, and crosslinked products thereof. (4) When recording information by irradiating the recording medium described in item 1 above with a laser beam, i) using a strong laser beam that oscillates at a wavelength corresponding to the absorption wavelength of the dye [D] in the recording medium; By irradiating the irradiation spot, the irradiation spot is partially heated and cooled rapidly, and information is recorded by forming a bump (bump), and ii) By irradiating the formed bump with a weak laser beam, A method for recording and erasing optical information, which comprises the steps of heating and slowly cooling the bumps to a rubber state, and erasing information by reducing the number of bumps.