JPH04151142A - Optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To form a homogeneous recording layer by incorporating a compd. in which a photochromic material and a cationic surfactant forms an ion complex into the recording layer. CONSTITUTION:The ion complex formation of the photochromic material having an anionic group and the cationic surfactant is executed. The impartation of surface activity to the photochromic material intrinsically not having the surface activity is, therefore, possible and the monomolecular film of the photochromic compd. stable at the gas-water boundary is formed. Then, the optical density possessed by the applied compd. is effectively utilized. The formation of the homogeneous recording layer by utilizing an LB method is allowed in this way. In addition, the formation of the recording layer even from the compd. to which the LB method is not applicable heretofore as the photochromic material is soluble in water or has no long chains is possible, insofar as this compd. has the anionic group.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording medium used for optical disks and the like on which information such as data or images is recorded with high density.

Conventional Technology Conventional rewritable optical recording media using photochromic compounds are known, but the operating principle of this optical recording medium is to reversibly change color using two types of light sources with different wavelengths. When the photochromic substance is an organic substance, an organic photochromic compound is used as the recording layer of the optical recording medium. As methods for forming on a substrate, cast method, polymer dispersion cast a, vacuum evaporation method, and Langmuir-Blodgett method (hereinafter abbreviated as LB method) are known, but the problems to be solved by the invention have been proposed in the past. Cast L When a recording layer is formed using a polymer dispersion casting method or a vacuum evaporation method, a photochromic compound that showed a good photochromic reaction in a solution may no longer show a stable photochromic reaction in the thin recording layer. .

Although it is thought that the cause of this is that photochromic compounds crystallize with each other in the recording layer or form a certain association state that makes it difficult for photochromic reactions to occur, it is also possible that such crystallization or association state may occur partially. In many cases, the photochromic reaction of the recording layer is not uniformly dispersed due to the occurrence of photochromic reactions in the recording layer. It has excellent properties such as controllability and stability of film quality and film thickness during film formation.

However, for photochromic compounds to which the LLB method can be applied (in order to form a monomolecular film at the air-water interface), it is necessary to impart surface activity to the photochromic compound itself. Therefore, when using the LB method as a method for manufacturing the recording layer of an optical recording medium, it is necessary to bond a long hydrocarbon chain as a substituent. However, it was not possible to form a stable monomolecular film at the air-water interface with photochromic compounds. As a means of forming a film of a compound to which the supplementary & LB method cannot be applied, a method of forming a mixed film of matrix molecules and a photochromic compound that forms a stable monomolecular film has also been proposed.

However, in such a mixed film (because the photochromic compound is diluted by the matrix molecules, the optical density per unit area becomes small), which is not efficient for manufacturing optical recording media that require a large optical density. With this mixed film method, the problem of aggregation still remains because the photochromic compound does not have long chains, and phase separation between the photochromic compound phase and the matrix phase may occur, resulting in a homogeneous film. The problem may be that it is difficult to form a recording layer.

In addition, in the case of water-soluble photochromic compounds, they dissolve from the mixed egg molecular membrane (X) Even if a thin film is formed, the important photochromic compound is not present in the thin film. The present invention was made in order to overcome the conventional problem that the LB method could not solve the material limitations as an optical recording medium. An object of the present invention is to provide a recording medium on which a recording layer is formed and a method for manufacturing the same.

Means for Solving the Problems The present invention is an optical recording medium containing a compound in a recording layer in which a photochromic substance having an anionic group and a cationic surfactant form an ionic complex, which solves the problems of the related art. By forming an ionic complex between a photochromic substance having an anionic group and a cationic surfactant, it is possible to impart surface activity to a photochromic substance that does not originally have surface activity. Therefore, a stable monomolecular film of the photochromic compound can be formed at the air-water interface. Thereby, the optical density of the applied compound can be effectively utilized, and a homogeneous recording layer can be formed using the LB method.

In addition, in the optical recording medium ζ of the present invention, it is possible to form a recording layer with a compound to which the LB method cannot be applied because the photochromic substance is water-soluble or does not have a long chain, but has an L anionic group. Therefore, the types of photochromic compounds that can be used as optical recording media that can be manufactured by the LB method can be increased, and the surface-active substance and the photochromic substance form an ionic complex. Even with the vapor deposition method, a homogeneous recording medium can be formed without causing aggregation.

Furthermore, the compatibility of the photochromic material with the binding polymer that has formed an L ion complex is improved by the polymer dispersion casting method in which a suspension dispersed in the binding polymer is cast.1. % Example As a photochromic substance applied to the present invention (like
For example, bi, 3', 3'-4limethylspiro[
2H-1-benzopyran-2,2′-indoline] derivative Ethyl-β-(3″, 3′-dimethyl-6-
Nitrospiro[2H-1-benzopyran-2,2'
-indoline biyl]-propenoate derivative
3,3゛-dimethyl-6-nitrospiro[2H-1
-Benzopyran-2,2benzoxazoline 1 derivative
6′-Methylthio-33°-dimethyl-8-methoxy-6-nitrospiro[2H-1-benzopyran-2,
Spiropyran derivatives such as 2'benzothiazoline] derivatives α-(2,5-dimethyl-3-furyl) α', δ
Examples include fulgide derivatives such as -dimethylfulgide derivatives.

As a method of introducing anionic groups into these photochromic substances (for example, substitution with sulfonic acid groups, carboxyl groups, phosphoric acid groups, etc. at easy-to-substitute locations) is also available.
Note that these substituents may be interposed with a spacer substance such as an alkyl group between them and the photochromic substance if necessary (
℃ Of these photochromic substances, spiropyrans are
Preferred from the viewpoint of photochromic reactivity are spiropyran compounds having the chemical structural formula shown by the general formula below (preferable from the viewpoint of stability of photochromic reaction), where X is a proton or a quaternary alkylamine. be.

R1 is hydrogen or an electron-withdrawing group, and examples of the electron-withdrawing group include a nitro group, a carboxyl group, and an acetyl group.
Among them, the nitro group is the most common because of its electron-withdrawing effect and ease of substitution reaction.R2 is hydrogen or an electron-donating group, and examples of the electron-donating group include alkyl, Examples include oxy group, amino group, hydroxyl group, etc. Among them, alkyloxy group is preferable from the point of view of electron donating property.However, this alkyl group is not introduced for the purpose of imparting amphiphilicity to the photochromic substance.The length of the carbon chain is It may be a short alkyl group, and the number of carbon atoms is not particularly limited. Cationic surfactants used in the present invention include amines having long-chain hydrocarbon groups, among which, for example, N, N-dioctadecyl-N, N
- Quaternary ammonium-containing amine having dimethylammonium, pyridinium, etc. Preferred embodiments of the present invention are shown below from the viewpoint of stability.

Example 1 The photochromic substance having an anionic group used is Spiropyran A, which is shown by the chemical structural formula below, and even if it has a sulfonic acid group at the N position (the following is a blank space), SO2F Spiropyran A This molecule (long-chain hydrocarbon Mi with chain Previously LB
Furthermore, this spiropyran A (
It is water-soluble because it has a sulfonic acid group.

In an aqueous solution, this spiropyran A is in a colored state with an absorption maximum at about 500 nm, and exhibits reverse photochromism.
, In addition, it shows a photochromic reaction in ethanol, and is colored with a maximum absorption wavelength of about 540 nm by ultraviolet irradiation as a cationic surfactant.
The use of dioctadecyl-dimethyl-ammonium ammonium is also used in molecule B.Cationic surfactants do not use amines or ammonium that have at least one long hydrocarbon chain.In particular, as in this molecule B, self-assembled 2 Surface-active substances capable of forming a molecular film can provide a high-quality recording layer because they form a homogeneous thin film. A mixed solvent of equal amounts of methyl alcohol and chloroform is used as the organic solvent, and this solution is used as a developing solution to form a monomolecular film. .) Formation of a monomolecular film at the air-water interface at a water temperature of 18°C was performed at a compression speed of 10 mm.
/min (confirmation of monomolecular film formation at surface pressure -
Figure 1 shows the surface pressure-area characteristics for the case of spiropyran A alone and the case of an ionic complex of spiropyran compound A and molecule B, which is a surfactant substance, in this example.

Spiropyran compound A alone cannot form a monomolecular film because it is water-soluble, but by forming an ionic complex with cationic surfactant B according to the present invention, it can form a stable monomolecular film at the air-water interface. Formation of the recording layer using the LB method, which has made it possible to fabricate the recording layer (with a cumulative surface pressure of 30m)
N/claw FIG. 2 shows the relationship between the wavelength and the absorbance of the recording/erasing characteristics of a recording layer produced by stacking five layers on a quartz plate substrate at a cumulative speed of 10 mm/min.

As shown in Fig. 2, immediately after fabrication, it is colorless as shown in Fig. 2a. ), Figure d (120 seconds irradiation).

As shown in Figure e (irradiation for 300 seconds), coloring with a maximum absorption wavelength of approximately 580 nm was recorded.

Furthermore, microscopic observation of this recording layer shows that the absorbance decreases when irradiated with light at 580 nm by a dye laser, and as shown in Figure 2a, it cannot be erased to the state immediately after accumulation. Example 2 The ionic complex solution of spiropyran compound A and surfactant B of Example 1 had a more homogeneous film quality than the optical recording medium in which JQ photochromic compound A was cast alone. Optical recording medium L was formed by adding a stearic acid solution in an equimolar amount to this ion complex and depositing five optical recording layers in the same manner as in Example 1.The optical recording medium L exhibited almost the same characteristics as in Example 1 and was mixed thoroughly. In addition to surfactants such as stearic acid, spacer aliphatic hydrocarbons such as octadecane are also effective for film formation. In Examples 1 and 2, the deposition of the optical recording layer was
Although the B method was used, the optical recording medium of the present invention is not limited to the LB method, and the optical recording medium of the present invention can be produced by forming a thin film on a substrate using a solution of a photochromic substance with an ion complex formed thereon by, for example, a spin coding method. A method may be used in which the solvent is evaporated, or a photochromic substance that has formed an ion complex and, for example, polyvinyl alcohol.
A film may be formed using a method such as spin coding or dip coating using a solution containing a binding polymer substance such as polymethyl methacrylate, polycarbonate, or polystyrene. Molecule E) was prepared (blank below) Spiropyran C OOH Spiropyran D Ha (CH2) + v N H2 Molecule E Example 3 Spiropyran C and molecule E were dissolved in equimolar amounts of ethyl alcohol to form an ion complex. t, :O Using this solution, a recording layer was formed on a quartz substrate using a spin coating method, and the f-island spin coating conditions (Table 1) The recording layer was coated for 20 seconds at a rotation speed of 2000 rpm, and the thickness of the recording layer was 1 μm. The recording layer is colorless immediately after being deposited, but when irradiated with ultraviolet rays it takes on a deep blue color, and the maximum absorption wavelength was able to record at approximately 610 nm.Also, it was possible to erase the recorded portion by irradiating light at 610 nm with a dye racer. ,,.

Example 4 Spiropyran D and molecule E were dissolved in equimolar amounts of methyl alcohol to form an ion complex. A recording layer was formed using this solution by spin coating in the same manner as in Example 3. Layer L Example 5 showing recording characteristics similar to Example 3 First, as in Example 1, spiropyran A and molecule B were used (
＼ Create an ion complex solution, dissolve polyvinyl alcohol in this solution so that the mixing ratio of ion complex and polyvinyl alcohol is 1:1000 by weight, and use the dip method to form a recording layer on a quartz substrate. The film thickness of the formed recording layer was about 2 μm, and the recording characteristics were almost the same as in Example 1. By forming an ion complex in this way, the compatibility with the binding polymer increased and was good. The above example describes the case of spiropyran as a photochromic substance. Compounds exhibiting photochromic properties such as fulgide derivatives and azo derivatives have similar effects if they have an anionic group. We have confirmed that there is.

Effects of the Invention The present invention is an optical recording medium containing a compound in which a photochromic substance having an anionic group and a cationic surfactant form an ionic complex in the recording layer. Does not cause agglomeration,
This has the effect of providing an optical recording medium that exhibits a good photochromic reaction.

[Brief explanation of drawings]

FIG. 1 shows the surface pressure-area characteristics graph of one embodiment of the present invention.
The figure is a diagram showing the recording/erasing characteristics of the recording layer of the optical recording medium of the present invention. Name of agent: Patent attorney Haruaki Ogata and 2 others

Claims (6)

[Claims] (1) A photochromic substance having an anionic group,
An optical recording medium characterized in that the recording layer contains a compound forming an ionic complex with a cationic surfactant. (2) The optical recording medium according to claim 1, wherein the photochromic substance is a spiropyran compound. (3) The optical recording medium according to claim 2, characterized in that the spiropyran compound has a chemical structure represented by the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Where X is a proton or a quaternary Alkylamine, R
_1 is hydrogen or an electron-withdrawing group; R_2 is hydrogen or an electron-donating group. (4) The optical recording medium according to claim 1, wherein the cationic surfactant is an amine derivative having a linear saturated hydrocarbon chain. (5) The optical recording medium according to claim 4, wherein the amine derivative is quaternary ammonium. (6) Production of an optical recording medium characterized by forming an ion complex with a photochromic substance having an anionic group and a cationic surfactant, and forming a thin film of the ion complex using the Langmuir-Blodgett method. Method.