JPS6289039A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin film and to enable multiple wavelength recording with a high hole retaining property by incorporating and dispersing a photochemically reactive substance such as a photoisomerization substance only in the micro phase in a matrix system having micro phase separative power. CONSTITUTION:In the matrix system having micro phase separative power, namely the capacity of forming a micro domain, the photochemically reactive substance which is highly compatible with the first high molecule material is used to incorporate the photochemically reactive substance only into the micro domain. For example, a hydrophilic substituent such as an amino group and an ester group is used in the polymer having a polypeptide or a hydrogen bonding side chain and ether-, ester-, amide-linkage, etc., are used as a covalent bond to be deposited on the first high molecular material. One molecule of the photochemically reactive substance per one molecule of the first high molecular material is deposited, hence the inter-molecular movement of energy can be controlled, the medium layer can be uniformized and thinned and multiple wavelength recording with a high hole retaining property can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium capable of wavelength multiplexing recording using the photochemical hole burning phenomenon at extremely low temperatures.

[Conventional technology]

Conventionally, optical recording materials have been made by freezing substances such as metal-free phthalocyanine, metal-free porphine, and quinizarin that exhibit a rainbow tautomerization reaction when exposed to light in a solvent such as alcohol or an alkane, or by freezing them in a solvent such as alcohol or an alkane. It is being considered that the above guest 'f' may be dissolved in a solution of a thicker polymer and made into a difilm-like medium by casting. There are also examples of alkali halides such as sodium fluoride and sodium iodide being irradiated with electron beams or ion beams to create a color center and used as a medium, but this is based on the mechanism that excited electrons are trapped. The lifetime of the holes formed is short, making it unsuitable for use as a nonvolatile memory. In comparison, the former is suitable for non-volatile memories, but considering the principle of photochemical hole burning, its performance is extremely influenced by the properties of the matrix material.

It goes without saying that what is desired as a memory medium is that the holes formed are narrow and the multiplicity can be increased, and that writing and reading can be done at high speed.In addition, the film thickness of the medium is thin enough to ensure sufficient spatial density. In addition, it is extremely important from the point of view of memory reliability that hole retention as the temperature rises, that is, hole recovery performance when the temperature rises above the pumping temperature and then returns to the writing temperature is good.

The medium thickness is preferably at least 1 μm or less in spot diameter in order to reduce optical blurring during recording and reading, and preferably one-fourth the wavelength of the irradiated laser to prevent reflection on the medium. In order to further ensure sensitivity while satisfying these five conditions, it is necessary to increase the concentration of the original conjugated molecule.

For example, if the medium thickness is 1 μm, the total spot diameter is 1 μm, and the wavelength multiplicity is 10”, the total number of molecules per hole is 1
In order to secure 0.04 molecules, it is necessary to set the concentration of photoisomerizable molecules to i0.17 mol/l.

[Problem that the invention seeks to solve]

However, in the conventional material system simply dispersed in a polymer, when such a high concentration is carried out, there is a drawback that the PHB phenomenon itself, which is caused by condensation of photoisomerized molecules, tends to occur.

In addition, the hole retention property was insufficiently reliable with respect to temperature because the excite changed due to lattice vibration as the temperature increased.

The present invention makes full use of the microphase separation between polymers in order to increase the concentration while suppressing aggregation of guest molecules, and to suppress irreversible changes in the matrix due to temperature rise. It is an object of the present invention to provide an optical recording medium which is capable of wavelength multiplexing recording and has hole retention properties.

[Means for solving problems]

To summarize the present invention, the present invention relates to an optical recording medium, and the present invention relates to an optical recording medium, in which the matrix is made of a first polymeric material having microphase separation ability or a second polymeric material containing the iI polymeric material. , characterized in that a photochemically reactive substance is present in the microphase.

In the present invention, microphase separation ability refers to the entire ability to form microphases, such as microdomains. However, even if the first monomolecular material does not release all the microdomains by itself, it is also included in the non-invention that the first monomolecular material forms all the microdomains in the second polymeric material. Below, we will use microdomains as a representative example of microphases. Although explained, the present invention is not limited to this.

FIG. 1 and FIG. S are schematic diagrams showing the basic structure of the medium of the present invention, and FIG. 2 is a partially enlarged view of FIG. It consists of a first polymeric material directly included in the domain, or the first polymeric material and a second polymeric material having a microdomain structure. Examples of photochemically reactive substances include metal-free phthalocyanine, metal-free porphine,
Metal-free chlorin and its derivatives, groton transfer tautomerized substances, intramolecular and intermolecular hydrogen bond conversion substances such as quinizarine and its derivatives, and photosensitive substances such as dimethyl-〇-tetrazine and diethyl-〇-tetrazine. Examples include decomposition-reactive substances. On the other hand, the matrix material, which is the main focus of the present invention, has two types of polymer materials that form a microdomain structure, and due to compatibility, the above-mentioned chemical anti-IC substance is in the first polymer material that forms microdomains. Any structure can be used as long as it has a structure that disperses only in the light, and the absorption wavelength range and light absorption range for photochemically reactive substances are different. In addition, in order to maximize the light absorption efficiency, it is desirable that the material does not turn white when cooled or frozen, as well as at room temperature.

These microdomains can have various structures such as random coils, α-helices, lamellas, and spherical shapes, but in the present invention, the photochemically reactive 913 substance is completely isolated in a strong microstructure through hydrogen bonds, etc. 9 Achieved the following two objectives.

In other words, it has become possible to suppress irreversible changes in the microscopic state of the matrix and improve hole retention, and to effectively disperse photochemically reactive substances at high concentrations while suppressing their aggregation, thereby making it possible to thin the medium.

Specifically, polypeptide molecular chains, block copolymers,
A matrix can be used that is a complete mixture of a first polymeric material capable of forming microdomains, such as a water-soluble polymer, and a respective hammered polymer in which it can be dispersed. In addition, as a method for fully containing the photochemically reactive substance only in the microdomains, gold is used as the first polymer material having good compatibility with the photochemically reactive substance, or gold is directly supported on the first polymer material by covalent bonding. There is a way.

The polypeptide is not particularly limited, but for example, γ-
Polymers obtained by homopolymerizing or copolymerizing L-amino acids such as methyl-L-glutamate and γ-benzyl-L-glutamate can be used as the first polymer material. Cast films made of these polymeric materials have sufficient mechanical strength, so a second polymeric material is not necessarily required. It can be used as a material.

Examples of block comonomers include, but are not limited to, vinyl monomers such as butadiene, isoprene, styrene, γ-methyl-L-glumemate, γ-benzyl-L-
AB type or ABA type block combinations having L-amino acids as basic units such as glutanaute can be used as the first polymer material. As the second polymer material for such a first polymer material, it is not necessarily necessary as in the case of the second polymer material for the polypeptide described above, but
For example, a polymer such as polymethacrylate that is soluble in a casting solvent such as chloroform can be used.

Examples of water-soluble polymers that can be used include, but are not particularly limited to, polyvinyl alcohol, polyoxyethylene, polyoxyethylene, polyacrylic acid, polymethacrylic acid, polyacrylamide, poly-2-hydroxyethyl methacrylate, and the like. Since these water-soluble polymers alone do not release all the microdomains, a suitable second polymeric material is required. The second polymer material may be any cylindrical material, such as polyvinyl acetate or polymethyl methacrylate, which has relatively low compatibility with the first polymer material and has the same M medium as the first polymer material.

On the other hand, methods for containing a photochemically reactive substance only in microdomains include using a photochemically reactive substance that has good compatibility with the first polymeric material, or having it supported by a covalent bond on the first polymeric material. There is. Photochemically reactive substances with good compatibility vary somewhat depending on the first polymer material used, but for example, for polypeptides or polymers with all hydrogen-bonding side chains, amino groups, hydroxyl groups, carboxyl groups, and amide groups are preferred. , as long as it has a hydrophilic substituent such as an ester group. Further, the covalent bond supported on the first polymer material is not particularly limited, but for example, ether, ester, amide, etc. can be used. In this case, if one molecule of the photochemically reactive substance is supported per molecule of the first polymer material, intermolecular energy transfer can be suppressed and a film with a uniform and thin medium layer, which is one of the objects of the present invention, can be produced. becomes.

The method of tabulating the medium is not particularly limited, but the photochemically reactive substance is dispersed in the medium to a concentration of 10-6 to 10-1 mol/l, and the medium is produced by casting onto a glass substrate or the like.

Evaluation of hole retention was performed by irradiating the zero phono/band at 4.2 with a single wavelength power density S, OmVI/cnr”CW laser source using the usual photochemical hole burning method, and measuring the absorption spectrum with a depth Dh ( After all 4.27 holes were formed, the temperature was raised to 80K and the temperature was increased to 4.2x'' again.
The depth of the recovered hole when cooling at step 1 fi-Dh (
80), the ratio Dh(80)/Dh (4,
It depends on the magnitude of the value of 2).

〔Example〕

The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

In addition, in Examples and Comparative Examples, only the preparation method of the medium sample is described, and the wavelength used for hole formation, the absorbance of the medium, and Dh (
80)/Dh(4,2) are summarized in Table 1.

Comparative Example 1 Metal-free tetraphenylporphine in a chloroform solution of polymethyl methacrylate was dried at a temperature of 10
-1 mol/l and then cast on a glass arrow substrate to obtain a film sample with a thickness of 1 μm.

Example 1 4-carboxyphenyltriphenylporphine and γ-
Tetraphenylporphine (TPP) lfi-bearing glutamate is synthesized by reacting (4-hydroxybenzyl λ-L-glutamate) in the presence of 1p-)luenesulfonic acid, and this glutamate derivative has a molecular weight of 1 per polymer chain. Engineering benzyl-glutamate and NC
A polypeptide with a molecular weight of about 10,000 was obtained by copolymerization using Method A VC. This was dissolved in chloroform and cast on a glass substrate to obtain a 1 μm thick film sample.

Example 2 4-carboxyphenyltriphenylporphine and 4-
With hydroxystyrene? The styrene monomer supported on tetraphenylporphine is completely synthesized by esterification reaction, and this styrene derivative has a molecular weight of approximately 5, containing one molecule per polymer chain.
1,000 polystyrene was obtained by living polymerization. Both terminals of the polystyrene were aminated using a conventional method, and a separately synthesized polypeptide having r-benzyl-L-glutamate as an amino acid unit was reacted with the polypeptide to obtain an ABA type block copolymer. A film sample with a thickness of 1 μm was obtained in the same manner as in Example 1.

Example 5 Tetra(4-carboxyphenyl)porphine was reacted with excess thionyl chloride to obtain tetra(4-carboxychloride phenyl)porphine, and this dimethylformamide (DMF) solution was diluted with polyvinyl alcohol (molecular weight 5,000) and DMF. It was slowly added dropwise to the bath solution to obtain tetraphenylporphine-supported polyvinyl alcohol.

The above polyvinyl alcohol and polymethyl methacrylate were mixed in a weight ratio of 1:2 in chloroform/methanol (volume/methanol).
Volume = 1/1) Thickness 1 by dissolving in mixed solvent and casting
Table 1 [Effects of the Invention] As explained above, if the present invention is applied, a photochemically reactive substance such as a photoisomerizable substance can be added to the IJTx yarn. By dispersing the spectral holes only in the microphase, the hole retention of the spectral holes formed by the photochemical hole burning method as the temperature rises is significantly improved, and at the same time, the overall uniformity of the original reactive substance is improved. Because it can be dispersed in a high concentration, a high-performance, highly reliable, and thin-film optical recording medium can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the basic structure of one example of the optical recording medium of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 6 is a schematic diagram showing another basic structure of the optical recording medium of the present invention. It is a schematic diagram.

Claims (1)

[Claims] 1. The matrix is made of a first polymeric material having microphase separation ability or a second polymeric material that includes the first polymeric material, and a photochemically reactive substance is contained in the microphase. An optical recording medium characterized by the fact that: 2. The optical recording medium according to claim 1, wherein the photochemically reactive substance is supported by a covalent bond on the first polymer material.