JPH02293737A - Recording medium and recording, erasing and reproducing method using this medium - Google Patents

Abstract

PURPOSE:To execute recording, erasing and reproducing with light exclusive of UV rays by using a recording layer contg. a benzoindoline spiropyrane compd., a phenolic compd. and a dyestuff having the absorption region exclusive of the absorption region of the benzoindoline spiropyrane compd. CONSTITUTION:The recording medium is formed by successively forming a light reflecting layer 2, a recording layer 3 and a protective layer 4 on a substrate 1. The recording layer 3 is formed by incorporating the benzoindoline spiropyrane compd., the phenolic compd. and the dyestuff having the absorption region exclusive of the absorption region of the benzoindoline spiropyrane compd. therein and is further formed by incorporating a high-polymer material therein. This recording medium is subjected to writing of information by the light of the wavelength of the absorption region of the colored benzoindoline spiropyrane compd. from the recording layer 3 side and is subjected to erasing by the light of the absorption region exclusive of the absorption region of the benzoindoline spiropyrane compd. Reproducing is executed by the light of the intensity weaker than the intensity of the writing light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium using a photochromic compound photoreceptor that can perform recording and erasing without using ultraviolet light.

Prior art> Optical recording media that have already been put into practical use include pit-forming type, phase change type recording media, and magneto-optical recording media.
All were heat mode types.

However, in the case of thermal mode, it is difficult to obtain a high-sensitivity medium due to the lag based on the principle of converting light into heat, energy loss associated with that conversion, and loss due to thermal conduction, and thermal deterioration of the medium may occur. It had many drawbacks, including being easy to use.

On the other hand, in the case of the light mode type, it is possible to avoid such drawbacks. Among optical mode type optical recording materials, photochromic compounds are attracting attention as recording materials that can be recorded and erased because their absorption spectra change reversibly when irradiated with light of different wavelengths.

Problems to be Solved by the Invention In ordinary photochromic compounds, the absorption peak in the decolorized state exists only in the ultraviolet wavelength region, so the change from the decolorized state to the colored state requires irradiation with ultraviolet light. has been used.

However, the only sources of ultraviolet light necessary for this change are large lasers such as excimer lasers or nitrogen lasers, and lamp light such as mercury lamps and deuterium lamps. This was extremely disadvantageous and unrealistic as a light source.

On the other hand, the oscillation wavelength range of semiconductor lasers, which are attracting attention as inexpensive and compact lasers, is currently dominated by the near-infrared region.
It is considered extremely difficult to reduce the oscillation wavelength to the ultraviolet region.

However, there is a need to develop an erasable recording medium made of a photoreceptor made of a photochromic compound that does not require ultraviolet light.

As a result of intensive studies to solve the above problems, we found that the above problems can be solved by using a recording medium made of a so-called reverse photochromic type benzoindoline spiropyran compound that has a stabilized color development state. The inventors have discovered that the above problems can be solved and have arrived at the present invention.

That is, the present invention provides (A) a benzoindoline spiropyran compound, (B) a phenol compound, (C) a dye having an absorption range other than the absorption range of the benzoindoline spiropyran compound, and optionally (D> A recording medium comprising a recording layer characterized by containing a polymeric substance, and a recording, erasing, and reproducing method using the same.

The present invention will be explained in detail below.

Examples of the benzoindoline spiropyran compound (A) used in the present invention include those represented by the following general formula (I).

Specifically, for example, 6-nitro-8-methoxy 1',3
',3'-}trimethylspiro[2H-1-penzopyran-2.2'-indolinco, 6-chloro-8methoxy1',3',3'-trimethylspiro[2H1-penzopyran-2.2'- indoline], 6 nitro-8-methoxy-1'-propyl-3', 3' dimethylsubiku [2H-1-penzopyran-2.2' indoline 1,6
-Hydroxyl 1',3',3'-trimethylspiro[2H-1-penzopyran-2,2'indolico6,8-dinitro-1',3',3'-}trimethylspiro[2H-1- Penzopyran-2,2'indoline]
etc.

The phenolic compound (B) used in the present invention is preferably one that has good compatibility with the spiropyran compound (A) and the polymer substance (DJ) and is highly effective in increasing the stability of the colored state of the spiropyran compound.

As such low molecular weight phenol compounds, bisphenols are particularly preferred. For example, 4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'-2-butylidene bisphenol, Bis(3-aryl-4-hydroxyphenyl)-sulfone and the like can be mentioned.

Further, from the viewpoint of coatability, etc., high molecular weight phenol compounds are particularly preferred, and examples of such compounds include poly(vinylphenol).

The spiropyran compound (A) is added in an amount of 1 to 100 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of these phenolic compounds (B).

The dye (C) having an absorption range other than the absorption range of the benzoindoline spiropyran compound used in the present invention has an absorption peak in a wavelength range that does not overlap with the absorption wavelength range of the benzoindoline spiropyran compound, and is It is a dye that does not act on benzoindoline spiropyran compounds in an unexposed state, but changes the benzoindoline spiropyran compounds into a colored state when exposed to light. Further, a material having good compatibility with the spiropyran compound <A) and the polymer substance (D) is used. Specifically, soluble dyes having an absorption peak in the near-infrared region are particularly preferred. Examples of such dyes include cyanine dyes, vorimethine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthraquinone dyes, naphthoquinone dyes, nickel dithiol complex dyes, and the like. These dyes have a total solids content of 1
1 to 30 parts by weight per 00 parts by weight, preferably 10 to 30 parts by weight
30 parts by weight is added and coated.

Here, when a low molecular phenol compound is used as component (B), a polymer substance (D
Add J. Furthermore, even when a polymeric phenol compound is used, a polymeric substance (D) may be added as a binder.

The amount of the polymer substance (D) added at this time is as follows:
1 for 100 parts by weight of phenolic compound (B)
A range of 0 to 1000 parts by weight is suitable.

The polymeric substance (D) includes the subirobilane compound (A), the phenolic compound (B), and the dye (C).
Those having good compatibility with and excellent film-forming properties are preferred. For example, BORI (methyl methacrylate), etc.
alkyl acrylates), poly(styrene), poly(
vinyl acetate), poly(vinyl butyral), cellulose acetate, poly(vinyl chloride), poly(vinylidene chloride),
Vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, poly(propylene), poly(ethylene),
Examples include poly(acrylonitrile), epoxy resin, urethane resin, phenol resin, polyester, and the like.

The composition containing the above <A) component, (B) component, (C) component, and optionally +D) component may be dissolved in a solvent, applied onto a substrate, and dried to form a photosensitive layer. ,(B)
When using a low molecular weight phenol compound as a component,
Furthermore, a polymer substance (DJ) is added as a binder to form a photosensitive layer.

Here, the thickness of the photosensitive layer is 0.01 to 10 μm, preferably 0.5 to 5 μm.

The solvent used in the present invention is not particularly limited, but specifically includes alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, ethers such as methyl ether, dioxane, and tetrahydrofuran, and ethyl acetate. , esters such as butyl acetate, halogenated solvents such as chloroform and methylene chloride, various general-purpose solvents represented by benzene, toluene, acetonitrile, dimethylformamide, etc., and mixed solvents thereof.

FIG. 1 shows a basic configuration diagram of the erasable optical recording medium of the present invention. FIG. 1-a shows a medium configuration when laser light is irradiated from the recording layer side, in which a light reflecting layer (2) is provided on a substrate (1), and furthermore, (A) component, (B) A recording layer (3) made of a composition containing component (C) and optionally component (D) is provided. Then, a protective layer (4) is provided thereon to form a medium. FIG. 1-b shows a medium configuration when laser light is irradiated from the substrate side, and the stacking order of the recording layer and the reflective layer is reversed from the former. In these media, the presence or absence of recording is detected by detecting changes in optical properties using light with a weaker intensity than the light in the first wavelength range used for writing. Here, optical properties include transmittance, refractive index, reflectance, etc.
It is preferable to detect changes in reflectance.

The substrate (1) used in the present invention is not particularly limited, and various types can be used. Examples include polycarbonate, poly(methyl methacrylate), poly(ethylene terephthalate), and glass plates.

As the light-reflecting layer 2, a vapor-deposited film of metal such as aluminum, silver, or gold, or a vapor-deposited film or coating film of a highly reflective dye is used. Examples of the highly reflective dyes used at this time include cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, polymethylene dyes, naphthoquinone dyes, and anthraquinone dyes, but are not particularly limited thereto. isn't it. The thickness of these reflective films is 0.1 to 1 μm.
A range of is appropriate.

The protective layer (4) is not particularly limited as long as it has oxygen barrier properties and coating properties, and various polymers can be used.

As the light source used in the present invention, various kinds of visible light or near-infrared light can be used, for example. Specifically, examples include argon laser, helium neon laser, krypton laser, dye laser, ruby laser, semiconductor laser, neobium/yag laser, and the like.

The principle of recording and erasing of the present invention can be considered as follows.

A typical spiropyran compound has the following formula: ultraviolet rays It exhibits photochromic properties as expressed by .

In this case, the uncolored state (SP) is stable, and when it is irradiated with ultraviolet light, it changes to the colored state (PMC). However, PMC in this colored state is unstable and returns to its original decolored state not only by visible light irradiation but also by the action of heat.

Therefore, when the stability of colored PMC is increased and so-called reverse photochromic type characteristics are imparted, the characteristics are expressed as shown in the following formula for ultraviolet light or thermal visible light. That is, the change from the uncolored state (SP) to the colored state (PMC) can be caused not only by ultraviolet light but also by the action of heat.

Therefore, in such a reverse photochromic type medium,
This medium contains a dye (antenna dye) that acts as a heat generation source, and is irradiated with a laser beam of a wavelength corresponding to the absorption wavelength of the dye. By heating the medium, it becomes decolorized (without using ultraviolet light). It becomes possible to cause a change from SP) to a colored state (PMC).

The above principle will be explained using figures. FIG. 2 schematically shows the absorption spectrum of the medium of the present invention.

In the medium of the present invention, the dye (C) having absorption in a wavelength range other than the absorption range of the spiropyran compound (A), specifically, the near-infrared region, is contained as an antenna dye, and the phenolic compound (B ) is stabilized in the colored state by spiropyran, so the spectrum in the colored state as shown in Figure 2-a is shown in the initial state. Do not color this medium.
Writing is performed by irradiating visible light (λ1) corresponding to the absorption wavelength of MC, and the spiropyran in the irradiated area changes to SP in a decolorized state (FIG. 2-b). The erasure of the record is then performed by irradiating near-infrared light with a wavelength of λ2 corresponding to the absorption wavelength of the antenna dye, and due to the action of the heat, the irradiated area changes from the uncolored state (SP) to the original color. Return to status (PMC).

Effects of the Invention By using the thermally stable photochromic photosensitive layer thus obtained, it has become possible to provide an inexpensive erasable optical recording medium.

Examples> Example 1 As a subiropyran compound, 6-nitro-8methoxy 1
',3',3'-}30 parts by weight of [2H-1 benzopyran-2,2'-indoline] and anthraquinone dye (LCD-109,
10 parts by weight of poly(4-vinylphenol) as a phenol compound, and 100 parts by weight of poly(methyl methacrylate) as a binder were dissolved in methyl isobutyl ketone. A photochromic photosensitive layer was formed by coating and drying on glass.

The absorption spectrum of the obtained medium is shown in FIG. The obtained medium exhibited absorption based on spiropyran in a colored state and the antenna dye, confirming that spiropyran was stabilized in a colored state (Figure 3-a).

When this medium was irradiated with 633 nm helium-neon laser light, the irradiated area was discolored and the spiropyran became a closed ring elliptical structure (FIG. 3-b). Next, apply 78 to the faded part.
When irradiated with 0 nm semiconductor laser light, the faded portion returned to the original colored body.

This confirms that this photosensitive layer can be used as an erasable recording medium that does not require ultraviolet light.

Example 2 As a spiropyran compound, 6-nitro-8methoxy-
30 parts by weight of 1',3',3'-trimethylspiro[2H1-penzopyran-2,2'-indoline], anthraquinone dye (LCD-109,
(manufactured by Nippon Kayaku) and 100 parts by weight of poly(4-vinylphenol) as a phenol compound were dissolved in methyl isobutyl ketone.

The resulting solution is applied onto a slide glass and dried to form a photochromic photosensitive layer. This medium also showed the same absorption spectrum as Example 1, and could be written with helium neon laser light and erased with semiconductor laser light.

Example 3 As a spiropyran compound, 6-nitro-8methoxy-
1',3',3'-}limethylspiro[2H-1-penzopyran-2,2'-indoline] 10 parts by weight, and 10 parts by weight of cyanine dye (NK-125, manufactured by Memoto Photosensitive Color) as an antenna dye. 1 part, 30 parts by weight of bis(3-aryl-4-hydroxyphenyl)-sulfone (TG-SA, manufactured by Nippon Kayaku) as a phenol compound, and 100 parts by weight of poly(methyl methacrylate) as a binder were dissolved in methyl ethyl getone. The obtained solution was applied onto a slide glass and dried to form a photochromic photosensitive layer.This medium also showed the same absorption spectrum as in Example 1, and could be easily written with helium neon laser light and erased with semiconductor laser light. was possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of the recording medium of the present invention, in which 1 represents a substrate, 2 represents a light reflective layer, 3 represents a recording layer, and 4 represents a protective layer. FIG. 2 schematically shows the absorption spectrum of the recording medium of the present invention. FIG. 2-a shows the absorption spectrum in the initial state, and FIG. 2-o shows the absorption spectrum after writing. FIG. 3 shows the absorption spectrum of the medium of Example 1. Figure 3-a shows the initial and post-erasure absorption spectra. Figure 3-b shows absorption after writing.

Claims (7)

[Claims] (1) (A) benzoindoline spiropyran compound,
Consisting of a recording layer characterized by containing (B) a phenolic compound, (C) a dye having an absorption range other than the absorption range of the benzoindoline spiropyran compound, and (D) a polymeric substance as necessary. recoding media. (2) The recording medium according to claim 1, wherein the phenolic compound (B) is poly(vinylphenol). (3) the dye (C) does not act on the benzindoline spiropyran compound when not exposed to light;
2. The recording medium according to claim 1, which is a dye that changes a benzoindoline spiropyran compound into a colored state when exposed to light. (4) The recording medium according to claim 1, wherein the dye (C) is a dye having an absorption peak in the near-infrared region. (5) Information is written on the recording medium according to claim 1 with light having a wavelength in the absorption range of the colored benzoindoline spiropyran compound, and information is written with light having an absorption range other than the absorption range of the benzoindoline spiropyran compound. A recording/erasing method characterized by erasing. (6) The recording/erasing method according to claim 5, wherein the light in an absorption range other than the absorption range of the benzoindoline spiropyran compound is semiconductor laser light oscillated in the near-infrared region. (7) A method for reproducing the recording medium according to claim 1, comprising detecting a change in optical properties using light having a weaker intensity than light in a wavelength range used for writing.