JP4961789B2 - Optical recording medium and recording layer forming dye - Google Patents

Description

  The present invention relates to a hydrazone metal chelate complex dye used for forming a recording layer of an optical recording medium. In particular, the present invention relates to a dye used for an optical recording medium compatible with blue laser light. The present invention also relates to an optical recording medium having a recording layer using such a dye.

  In recent years, since it is possible to record / store / reproduce information at a high density, development of an optical recording medium using a laser beam, particularly an optical disk, has been underway. Among the optical disks, a writable compact disk (CD-R) is recently attracting attention. The CD-R usually has a structure in which a recording layer mainly composed of a dye, a metal reflective film, and a protective film are sequentially laminated on a circular plastic substrate having guide grooves. Information is recorded on the CD-R by irradiating the laser beam and absorbing the irradiation energy in the recording layer, so that the recording layer, the reflective layer, or the substrate of the laser beam irradiation part decomposes, evaporates, dissolves, etc. This is performed by a method of generating a general deformation (heat mode), a method of reversibly changing the structure of the dye contained in the recording layer of the laser light irradiated portion (photon mode), or the like. The recorded information is reproduced by reading the difference in reflectance with respect to the laser beam between the portion where thermal deformation or dye structure change due to laser light irradiation occurs and the portion where it does not occur. Therefore, it is necessary for the recording layer of the optical recording medium to efficiently absorb the energy of the laser beam, and a laser beam absorbing dye is generally used for the recording layer.

An optical recording medium using an organic dye as a laser light absorbing dye can form a recording layer by a simple method of applying an organic dye solution, and is expected to become increasingly popular as an inexpensive optical recording medium in the future. .
Also, in recent years, in order to increase the recording density, the wavelength of laser light used for recording has been shortened from a wavelength centered on the conventional semiconductor laser emission wavelength of 780 nm to a blue light region of about 405 nm or less. Is being considered.

Further, in recent years, in order to increase the capacity of recording media, the creation of a double-layer recording medium that doubles the storage capacity by creating two recording layers on the recording medium and the speeding up of recording have been studied. For this reason, the dye compound for recording layers is increasingly required to have high sensitivity to recording lasers.
In addition, when a dye is used for the recording layer, it is generally advantageous to apply it to a substrate using a spin coating method in terms of cost compared to the vacuum vapor deposition method. Therefore, the dye for an optical recording medium has high solubility in a coating solvent. Is essential. At present, fluoroalcohol solvents such as 2,2,3,3-tetrafluoropropanol (TFP) and 2,2,3,3,4,4,5,5-octafluoropentanol (OFP) are used on polycarbonate substrates. It is common to apply using.

  Furthermore, data recording and reading are generally performed by laser light, and the reading laser intensity is weaker than the recording laser intensity. Therefore, if the light resistance of the dye is so low that the dye forming the recording layer of the optical recording medium is decomposed by the weak laser light irradiation that is the readout light, it may cause a data error when reading the recording data. Become. In addition, since optical recording media are often exposed to sunlight or illumination on the recording surface for a long time due to their properties, if the dye is inferior in light resistance, it becomes difficult to store the recording data of the optical recording medium for a long period of time. . Accordingly, the recording layer dye is required to have high light resistance.

The imine compound is one of the compounds expected to be applied to optical recording media because of its simple synthesis and maximum absorption mainly at 300 nm or more. Has been made.
JP 2005-515914 A International Publication No. 2004-102551

However, these compounds generally have excellent solubility in coating solvents when they are not metal complexes, but are extremely inferior in light resistance. When they are metal complexes, the light resistance is improved, but the solubility in coating solvents is greatly reduced. To do. That is, the imine compounds described in Patent Documents 1 and 2 are significantly inferior in either solubility in a coating solvent or light resistance.
For example, Patent Document 1 only describes an optical recording medium using an imine compound containing no metal as an example, and it is clear that the compound of the example is extremely inferior in light resistance as a result of examination by the inventors. became. In addition, as a result of studies by the inventors, the imine metal complex compounds listed as examples in Patent Document 2 have been found to be extremely inferior in solubility in fluorine alcohol solvents. Further, when a similar study was performed on a salen complex compound, which is a general compound among imine metal complex compounds, it was also found that the solubility in a fluorine-based alcohol solvent was remarkably inferior.

  The present invention has been made in view of the above circumstances, and is excellent in both solubility in a coating solvent and light resistance, and can be used for optical recording using blue laser light. An object is to provide an imine dye for formation.

If it is not a metal complex, the light resistance is significantly inferior because the imine structure is unstable to light. If it is a metal complex, the light resistance is improved. It is considered that the reason for the large decrease is that the compound becomes rigid as a result of metal complexation, so that the stability is improved but the affinity with the solvent is decreased.
On the other hand, a hydrazone compound, which is a kind of imine compound, has a skeleton having an amino group (N—N═C skeleton) adjacent to a Schiff base, so that the compound is less rigid than the above imine compound and is soluble in metal complexes. Improvement is expected. However, in general, the NN single bond is unstable due to light and the like, and the π-conjugated system of the whole compound is interrupted by the NN single bond, so that it is difficult to increase the wavelength. Application to was thought impossible.

However, as a result of intensive studies by the present inventors to solve the above problems, the metal chelate complex compound containing a hydrazone ligand represented by the following general formula (1) is soluble in a coating solvent and in a thin film state. The present invention was completed by finding that the optical recording medium having excellent light resistance of the optical recording medium can be satisfactorily recorded with blue laser light.
That is, this invention makes the following a summary.
[1] A dye for forming a recording layer of an optical recording medium, comprising at least one hydrazone chelate complex represented by the following general formula (1).

(In general formula (1), ring A and ring C represent a nitrogen-containing heteroaromatic ring which may have a substituent, and ring B and ring D represent an aromatic ring which may have a substituent. , R ^{1 to} R ⁴ each independently represents a hydrogen atom or a monovalent substituent having 20 or less carbon atoms, X ¹ and X ² each independently represent a group 15 or 16 atom, and M represents a divalent transition metal Represents a cation, and when X ¹ and / or X ² is a Group 15 atom, the atom may further have a monovalent substituent having 20 or less carbon atoms.)
[2] The recording layer forming dye of the optical recording medium according to [1], wherein M is cobalt.
[3] A substrate and at least a recording layer formed on the substrate, wherein the recording layer is formed using the recording layer forming dye of the optical recording medium according to [1] or [2]. An optical recording medium characterized by that.
[4] A recording method for an optical recording medium, wherein the optical recording medium according to [3] is recorded using a laser beam having a wavelength of 350 to 530 nm.

  The recording layer forming dye of the optical recording medium of the present invention is excellent in solubility, light resistance and blue laser recording sensitivity. Therefore, by using this dye in the recording layer of an optical recording medium, a high-density optical recording medium having excellent recording characteristics with blue laser light and good light resistance can be provided at low cost with good film properties. It becomes possible to do.

Embodiments of the present invention will be specifically described below, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.
[Dye for recording layer formation]
The recording layer forming dye of the optical recording medium according to the present invention contains at least one hydrazone chelate complex represented by the following general formula (1).

(In general formula (1), ring A and ring C represent a nitrogen-containing heteroaromatic ring which may have a substituent, and ring B and ring D represent an aromatic ring which may have a substituent. , R ^{1 to} R ⁴ each independently represents a hydrogen atom or a monovalent substituent having 20 or less carbon atoms, X ¹ and X ² each independently represent a group 15 or 16 atom, and M represents a divalent transition metal Represents a cation, and when X ¹ and / or X ² is a Group 15 atom, the atom may further have a monovalent substituent having 20 or less carbon atoms.)
{Explanation of words}
In the present invention, the aromatic ring means a ring having aromaticity, that is, a ring having a (4n + 2) π electron system (n is a natural number). The skeleton structure is usually an aromatic ring consisting of a 5- or 6-membered monocyclic ring or a 2-6 condensed ring. The aromatic ring includes an aromatic hydrocarbon ring, an aromatic heterocyclic ring, and an anthracene ring. , Condensed rings such as a carbazole ring and an azulene ring are also included.

“(Hetero) aryl” means both “aryl” and “heteroaryl”, and “(hetero) aralkyl” means both “aralkyl” and “heteroaralkyl”.
In the present invention, “may have a substituent” means that one or more substituents may be present.

In addition, in the compound manufactured by the manufacturing method which concerns on this invention, 1 type of the hydrazone metal chelate compound which concerns on this invention may be contained independently, and 2 or more types may be mixed and contained. good.
Hereinafter, the hydrazone chelate complex represented by the general formula (1) will be described in detail.
^{R 1 ~R 4}
(1) In the formula, R ^{1 to} R ⁴ each independently represents a hydrogen atom or a monovalent substituent having 20 or less carbon atoms.

  Examples of the substituent include a chain alkyl group, a chain alkenyl group, a chain alkynyl group, a hydrocarbon ring group, a heterocyclic group, an alkoxy group, an alkylcarbonyl group, a (hetero) aryloxy group, and a (hetero) aralkyloxy group. , An optionally substituted amino group, nitro group, cyano group, ester group, optionally substituted carbamoyl group, halogen atom, hydroxyl group and the like.

Examples of chain alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, tert-butyl, hexyl, octyl, etc. Examples include 1 to 20, preferably 1 to 10 linear or branched ones.
Examples of the chain alkenyl group include a linear group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, such as a vinyl group, a propenyl group, a butenyl group, a 2-methyl-1-propenyl group, a hexenyl group, and an octenyl group. Or a branched thing is mentioned.

Examples of the chain alkynyl group include straight chain having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms such as ethynyl group, propynyl group, butynyl group, 2-methyl-1-propynyl group, hexynyl group and octynyl group. Or a branched thing is mentioned.
The hydrocarbon ring group usually has 3 to 20 carbon atoms such as a cyclopropyl group, cyclohexyl group or tetradecahydroanthranyl group, preferably 5 to 10 carbon atoms such as a cycloalkyl group or cyclohexenyl group. And preferably an aryl group having 6 to 18 carbon atoms, preferably 6 to 10 carbon atoms, such as a cycloalkenyl group, a phenyl group, an anthranyl group, a phenanthryl group, a ferrocenyl group, and the like.

The heterocycle includes a heteroaryl group consisting of a 5-6 membered monocyclic ring or a 2-6 condensed ring, 5
A heterocycloalkyl group consisting of a ˜6-membered monocyclic ring or a 2-6 condensed ring is exemplified, and examples of the heteroatom include a nitrogen atom, an oxygen atom, and a sulfur atom. Specifically, 5-membered ring such as thienyl group, 6-membered ring such as pyridyl group, 2-piperidinyl group, 2-piperazinyl group, benzothienyl group, carbazolyl group, quinolinyl group, octahydroquinolinyl group or the like 5 or A 6-membered 2-6 condensed ring is mentioned.

Examples of the alkoxy group include methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, iso-butoxy group, sec-butoxy group, tert-butoxy group, hexyloxy group, octyloxy group and the like. Usually, 1 to 9, preferably 2 to 8 are mentioned.
Examples of the alkylcarbonyl group include those having 2 to 18 carbon atoms, preferably 2 to 8 carbon atoms, such as a methylcarbonyl group, an ethylcarbonyl group, an isopropylcarbonyl group, a tert-butylcarbonyl group, and a cyclohexylcarbonyl group.

  Examples of (hetero) aryloxy groups include aryloxy groups having 6 to 18, preferably 6 to 10 carbon atoms, such as phenoxy groups and naphthyloxy groups, 2-thienyloxy groups, 2-furyloxy groups, Examples thereof include heteroaryloxy groups having 2 to 18 carbon atoms such as 2-quinolyloxy group, preferably 5 to 10, preferably including nitrogen atom, oxygen atom, sulfur atom and the like as a hetero atom.

  Examples of (hetero) aralkyloxy groups include aralkyloxy groups such as benzyloxy group, phenethyloxy group, naphthylmethoxy group and the like, which usually have 7 to 18, preferably 7 to 12 carbon atoms, 2-thienylmethoxy group, 2 -Heteroaralkyloxy groups having 6 to 18, preferably 6 to 10 carbon atoms, such as a furylmethoxy group and a 2-quinolylmethoxy group, and those containing a heteroatom selected from a nitrogen atom, an oxygen atom, a sulfur atom and the like Etc.

Examples of the amino group which may have a substituent include an amino group, an alkylamino group, and a (hetero) arylamino group.
Examples of the alkylamino group include those having 2 to 20 carbon atoms, preferably 3 to 10 carbon atoms, such as an ethylamino group, a dimethylamino group, a methylethylamino group, a dibutylamino group, and a piperidyl group.

  Examples of (hetero) arylamino groups include arylamino groups having 6 to 30, preferably 6 to 15 carbon atoms such as diphenylamino group, dinaphthylamino group, naphthylphenylamino group, and ditolylamino group, and di (2 -Thienyl) amino group, di (2-furyl) amino group and the like having 5-30 carbon atoms, preferably 6-15, and heteroaryls including heteroatoms selected from nitrogen atoms, oxygen atoms, sulfur atoms, etc. Examples thereof include arylheteroarylamino groups having 11 to 30, preferably 12 to 16, carbon atoms such as an amino group and a phenyl (2-thienyl) amino group.

Examples of the carbamoyl group which may have a substituent include a carbamoyl group and an alkylcarbamoyl group.
Examples of the alkylcarbamoyl group include those having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms such as an N-methylcarbamoyl group, an N, N-dimethylcarbamoyl group, and an N-ethyl-N-cyclohexylcarbamoyl group.

Examples of the ester group include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, an isopropoxycarbonyl group, a tert-butoxycarbonyl group, an acetyloxy group, a benzoyloxy group and the like having 2 to 20, preferably 2 to 10 are listed.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In addition, it is preferable that R ¹ and R ² contain 4 or more carbon atoms in total for improving the heat and moisture resistance of the compound.
<Molecular weight of R ^{1 to} R ⁴ >
The molecular weights of R ^{1 to} R ⁴ are preferably 600 or less in total from the viewpoint of preventing a decrease in extinction coefficient accompanying an increase in molecular weight.
{Ring A and Ring C}
Ring A and ring C each represent a nitrogen-containing heteroaromatic ring which may have a substituent. Specific examples of ring A and ring C include imidazole ring, thiazole ring, oxadiazole ring as 5-membered monocycle, pyridine ring, pyrazine ring as 6-membered monocycle, quinoline ring, isoquinoline ring, quinoxaline as condensed ring Benzimidazole ring, benzoxazole ring, benzothiazole ring and the like. Among these, it is preferable that either ring A or ring C is a 6-membered monocyclic ring for the reason of synthesis of the compound.

In addition, the specific example of the substituent which the rings A and C may have corresponds to the specific example of the substituent which the above-described R ^{1 to} R ⁴ may have.
{Ring B and Ring D}
Ring B and ring D each represent an aromatic ring which may have a substituent. Specific examples of ring B and ring D include a furan ring, a thiophene ring, a pyrrole ring, an imidazole ring, a thiazole ring, an oxadiazole ring as a 5-membered monocyclic ring, a benzene ring, a pyridine ring, and a pyrazine as a 6-membered monocyclic ring. Examples of the condensed ring of 5 or 6-membered ring include naphthalene ring, phenanthrene ring, azulene ring, pyrene ring, quinoline ring, isoquinoline ring, quinoxaline ring, benzofuran ring, carbazole ring, dibenzothiophene ring and anthracene ring. Of these, a monocyclic ring is preferred for reasons of synthesis, a 6-membered monocyclic ring is more preferred, and a benzene ring is particularly preferred.

In addition, the specific example of the substituent which the rings B and D may have corresponds to the specific example of the substituent which the above R ^{1 to} R ⁴ may have.
In addition, when any of the ring A to the ring D has two or more substituents, the substituents may be bonded to each other to form a cyclic structure that may include a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. For example, when ring A and / or ring C is a group derived from a pyridine ring, examples in which substituents of the pyridine ring are bonded to each other to form a ring structure that may contain a hetero atom are shown below. The structure shown is mentioned. In the following, a is the bonding position to the hydrazone skeleton.

In addition, it is preferable that the ring A to the ring D have these substituents because the solubility of the dye in the solvent used in forming the recording layer is improved.
It is preferable not to have it because synthesis becomes easy.
Further, when ring A and ring B have these substituents, when a polar solvent such as tetrafluoropropanol or methyl cellosolve is used as a solvent, N, N-disubstituted carbamoyl groups, ester groups, etc. A polar substituent is preferably contained, and when a nonpolar solvent such as methylene chloride, dibutyl ether or methylcyclohexane is used as the solvent, a nonpolar substituent such as an alkyl group or an alkoxy group is preferably contained.
{X ¹ and X ² }
X ¹ and X ² each independently represent a group 15 or group 16 atom. Specific examples thereof include N, O, P, S, Se, and the like. Among these, it is preferably 16 group atoms from the synthetic surface, and O and S are particularly preferable.

When X ¹ and / or X ² is a 15 group atom, the 15 group atom may further have a monovalent substituent having 20 or less carbon atoms. Specific examples of the substituent correspond to specific examples of the substituent that R ^{1 to} R ⁴ may have.
{M}
M represents a divalent transition metal cation. The metal cation may be anything as long as it can form a metal complex with the hydrazone ligand. Specific examples include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, Cations such as Pt, Au, Er and the like can be mentioned.

The transition metal cation is preferably a cation of the fourth periodic element from the economical viewpoint, and particularly preferably a Co cation from the viewpoint of improving light resistance.
{Molecular weight}
The hydrazone chelate complex represented by the general formula (1) described above usually has a molecular weight of 1,500 or less, particularly 1,000 or less, including metal cations and anions, from the viewpoint of preventing sensitivity from being reduced due to a decrease in absorbance. It is preferable.
Further, the two hydrazone ligands constituting the compound represented by the general formula (1) may be the same or different, but are preferably the same for reasons of synthesis.

The compound represented by the general formula (1) is usually preferably insoluble in water for the purpose of improving the storage stability of the recording medium. Here, “water-insoluble” means that the solubility in water at 25 ° C. and 1 atm is usually 0.1% by weight or less, preferably 0.01% by weight or less.
{Concrete example}
Specific examples of the hydrazone chelate complex represented by the general formula (1) are illustrated below, but the present invention is not limited to these unless it exceeds the gist. In the following, Et represents an ethyl group, and Ac represents an acetyl group.

{Synthesis method}
The hydrazone ligand constituting the hydrazone chelate complex represented by the general formula (1) can be easily synthesized by the reaction shown below.

  At this time, a solvent may or may not be present in the reaction system. When a reaction solvent is used, a polar solvent such as ethanol or acetonitrile or a nonpolar solvent such as toluene or xylene can be used as the solvent, and an acid such as hydrochloric acid, acetic acid or sulfuric acid may be added as a catalyst. The amount of the catalyst added in this case is not particularly limited as long as the reaction proceeds, but it is preferably about 1/100 to 1 mole times the reagent. The reaction temperature is preferably such that the solvent is refluxed from room temperature, and the reaction time is preferably about 1 minute to 48 hours.

In addition, the chelate complex in the present invention can be obtained by subjecting the hydrazone ligand synthesized by the above-described method and a transition metal salt to a heating reaction in such a manner that the solvent is refluxed from room temperature in the presence or absence of the solvent. When a reaction solvent is used, a polar solvent such as water, ethanol or acetonitrile, or a nonpolar solvent such as chloroform, toluene or xylene can be used as the solvent. In this case, an inorganic base such as sodium hydroxide or potassium carbonate, or an organic base such as pyridine or triethylamine may coexist in the reaction system. In this case, the amount of the base added is not particularly defined as long as the reaction proceeds, but it is preferably about 1 to 10 mole times the reagent.
{Light resistance and solubility in coating solvent}
Among the recording layer forming dyes containing the hydrazone chelate complex of the present invention, preferred are excellent in light resistance and solubility in a coating solvent, and also excellent in film properties and recording sensitivity when used for forming a recording layer of an optical recording medium. There is a feature. In this case, excellent light resistance means that the hydrazone chelate complex thin film coated so as to have a film thickness of about 50 nm has a temperature of 58 ° C., a humidity of 50%, and a xenon lamp (intensity 0.55 W / m ² ) irradiation condition. Even when the light resistance test is conducted for 40 hours, it means that usually 70% or more, preferably 80% or more, particularly preferably 90% or more of the hydrazone chelate complex thin film remains without deterioration. Here, the degree of deterioration is determined by the absorption reduction rate of the absorption maximum at 300 to 500 nm. In such a light resistance test, first, a solution containing a dye is applied on a substrate so that the film thickness after drying is about 50 nm, and then dried to obtain a layer containing the dye. The layer containing the dye was irradiated with a xenon lamp (intensity 0.55 W / m ² ) for a predetermined time under conditions of a temperature of 58 ° C. and a humidity of 50%, and the absorbance at the absorption maximum wavelength before and after the irradiation was compared. And determine the residual ratio of the pigment. In addition, excellent solubility in a coating solvent means that 0.7% by weight or more, preferably 1.0% by weight or more, more preferably 1.5% by weight or more dissolves in TFP at 20 ° C. under normal pressure. Indicates. Determination of dissolution is performed based on whether or not a crystal residue of the compound remains in the solvent when the compound and TFP are mixed at a specific concentration. In the application of the present invention, the upper limit of the solubility is not particularly limited, but is usually 20% by weight or less, particularly about 10% by weight or less.

The reason why the hydrazone metal complex compound of the present invention is excellent in light resistance and solubility in a coating solvent is that the hydrazone ligand is stabilized by metal chelation and has an octahedral coordination form. This is presumed to be due to improved performance.
[Optical recording medium]
{Recording layer}
The recording layer of the optical recording medium of the present invention comprises a dye containing at least one hydrazone chelate complex represented by the general formula (1) (this is appropriately referred to as “the recording layer forming dye of the optical recording medium of the present invention” or simply “ It is formed using the “dye of the present invention”). That is,
The recording layer of the optical recording medium of the present invention contains at least one hydrazone chelate complex of the present invention.
The recording layer of the optical recording medium of the present invention contains at least one hydrazone chelate complex represented by the present invention as a recording layer forming dye.

  As the dye used for forming the recording layer of the optical recording medium of the present invention (the dye of the present invention), only one kind of the hydrazone chelate complex of the present invention may be used, and two or more kinds of the hydrazone chelate complex of the present invention may be used. You may use together in a combination and a ratio. In addition to one or two or more hydrazone metal chelate complexes of the present invention, one or two or more other dyes may be used in combination. However, when a dye other than the hydrazone chelate complex of the present invention is used in combination, the ratio of the hydrazone chelate complex of the present invention to the total of all the dyes from the viewpoint of sufficiently exerting the excellent properties of the hydrazone chelate complex of the present invention Is usually 50% by weight or more, preferably 70% by weight or more.

  Other types of dyes that can be used in combination with the hydrazone chelate complex of the present invention have absorption in the laser light wavelength region for recording, absorb the energy of the irradiated laser light, and the recording layer and reflective layer of the irradiated portion Alternatively, it is preferable to form pits with thermal deformation such as decomposition, evaporation, and dissolution on the substrate. In addition, a dye suitable for recording with a near-infrared laser beam having a wavelength selected from the range of 770 to 830 nm for CD-R and a red laser beam selected from the range of 620 to 690 nm for DVD-R is used in combination. Thus, an optical recording material corresponding to recording with laser beams in a plurality of wavelength regions can be used. Specific examples of other dyes include metal-containing azo dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, and triarylmethane dyes. Examples include dyes, merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes, and these may be used alone. Two or more kinds may be used in combination.

Of these other dyes, a near infrared laser beam having a wavelength selected from a range of 770 to 830 nm for CD-R and a red laser beam selected from a range of 620 to 690 nm for DVD-R. In combination with a dye suitable for recording, an optical recording material corresponding to recording with laser beams in a plurality of wavelength ranges can be obtained.
The proportion of the recording layer forming dye of the present invention in the recording layer is usually 10% by weight or more, preferably 50% by weight or more, and particularly preferably 90% by weight or more.

  If the ratio of the dye is too small, the recording sensitivity is remarkably lowered, which is not preferable. When two or more kinds of dyes are used in combination as the dye of the present invention, the sum thereof satisfies the above range. In addition, when using the binder and various additives described below, the amount of the binder or additive used should be adjusted so that the ratio of the dye of the present invention in the formed recording layer is within the above range. Is preferred. In addition, it is especially preferable that a binder and an additive are not used from a viewpoint which fully exhibits the outstanding characteristic of the hydrazone metal chelate complex of this invention.

  The recording layer may contain a binder in order to improve the film formability. As the binder, known ones such as polyvinyl alcohol, polyvinyl pyrrolidone, ketone resin, nitrocellulose, cellulose acetate, polyvinyl butyral, and polycarbonate can be used singly or in combination of two or more. When the ratio of the binder occupying the recording layer is too high, the recording sensitivity is remarkably lowered. Therefore, when the binder and further various additives described below are used, the ratio of the recording layer forming dye of the present invention to the formed recording layer is The amount is within the above range.

The recording layer may contain a singlet oxygen quencher for improving stability and light resistance, a recording sensitivity improver, and the like.
Examples of the singlet oxygen quencher include chelate compounds of acetylacetonate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone and the like and transition metals, and these may be used alone. Two or more kinds may be used in combination.

  Examples of the recording sensitivity improver include metal compounds in which a metal such as a transition metal is contained in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline. And organometallic compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex, and so on. You may use, and may use 2 or more types together. The type of metal atom is not particularly limited, but a transition metal is preferable.

The singlet oxygen quencher is usually used in an amount of about 5 to 30% by weight based on the dye, and the recording sensitivity improver is usually used in an amount of about 10 to 30% by weight based on the dye.
When two or more types of singlet oxygen quenchers are used in combination, or when two or more types of recording sensitivity improvers are used in combination, the total is made to satisfy the above range.
In order to form a recording layer of an optical recording medium using the hydrazone chelate complex of the present invention, it is generally used to form a thin film such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method. Can be used. Of these, spin coating is preferred from the standpoints of mass productivity and cost. When the recording layer is formed by spin coating, the rotational speed is preferably 500 to 5000 rpm, and after spin coating, treatment such as heating or exposure to solvent vapor may be performed as necessary. The thickness of the recording layer is not particularly limited, but is usually 10 nm to 5 μm, preferably 20 nm to 2 μm, and more preferably 50 nm to 300 nm. When the film thickness of the dye layer is larger than the lower limit, the influence of thermal diffusion can be suppressed, and good recording is easy. In addition, since the recording signal is hardly distorted, the signal amplitude can be easily increased. When the film thickness of the dye layer is smaller than the above upper limit value, it is easy to increase the reflectance and to improve the reproduction signal characteristics.

  When the recording layer is formed by a doctor blade method, a cast method, a spin coating method, a dipping method, etc., first, the recording layer forming dye, binder, singlet oxygen quencher, recording sensitivity improver and other agents of the present invention are used. A pigment is dissolved in a solvent to prepare a coating solution. As the solvent, use of TFP is particularly preferable from an industrial viewpoint. However, the solvent is not limited to TFP as long as it does not attack the substrate, such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone. Ketone alcohol solvents, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, chain hydrocarbon solvents such as n-hexane and n-octane, cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, t- Alicyclic hydrocarbon solvents such as butylcyclohexane and cyclooctane, ether solvents such as diisopropyl ether and dibutyl ether, fluorine alkyl alcohol solvents such as OFP and hexafluorobutanol, methyl lactate, ethyl lactate and methyl isobutyrate Hydroxy It can also be used ester-based solvents. In addition, although these solvents may be used individually by 1 type and may be used in mixture of 2 or more types, it is preferable to use 1 type independently from an industrial surface.

  The concentration of the recording layer forming dye of the present invention in the coating solution is appropriately determined according to the solvent solubility, but is usually 0.7% by weight or more, preferably 1.0% by weight or more, and usually 10% by weight. % Or less, preferably 3.0% by weight or less. If the dye concentration in the coating solution is excessively low, the formation efficiency of the recording layer is deteriorated. If the dye concentration in the coating solution is excessively high, problems such as dye crystallization occur in the film forming process.

In addition, in order to efficiently recover the excess dye after spin coating, the dye compound can be dissolved in the coating solvent even when the concentration is usually 1.5 times or more, preferably 2 times or more the concentration of the coating solution. It is preferable that
{Optical recording medium}
The optical recording medium of the present invention has a recording layer formed as described above using the recording layer forming dye of the present invention.

  As the substrate of the optical recording medium on which the recording layer is formed, a substrate transparent to the laser beam to be used, such as glass and various plastics, is preferably used. Examples of plastics include acrylic resin, methacrylic resin, polycarbonate resin, vinyl chloride resin, vinyl acetate resin, nitrocellulose, polyester resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, epoxy resin, etc., In view of cost, moisture absorption resistance and the like, polycarbonate resin injection molded is preferable.

Usually, a layer other than the recording layer such as a reflective layer, a protective layer, and an undercoat layer is further provided on the substrate as necessary, and used as an optical recording medium.
Examples of the reflective layer include those made of a metal such as gold, silver, aluminum, or an alloy thereof, but silver is preferable to gold or aluminum because of the reflectance with respect to laser light having a wavelength of 550 nm or less. The metal reflective layer is formed on the recording layer by vapor deposition, sputtering, ion plating, or the like. Here, an intermediate layer may be provided between the metal reflective layer and the recording layer for the purpose of improving the adhesion between the layers or for increasing the reflectance. The thickness of the reflective layer is usually in the range of 50 nm to 300 nm.

The material of the protective layer formed on the reflective layer is not particularly limited as long as it protects the reflective layer from external force. Examples thereof include organic substances such as thermoplastic resins, thermosetting resins, electron beam curable resins, UV (ultraviolet) curable resins, and inorganic substances such as SiO ₂ , SiN ₄ , MgF ₂ , and SnO ₂ .
A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying.

  The UV curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiating with UV light. Examples of the UV curable resin include acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a spin coating method is preferable. The thickness of the protective layer is usually in the range of 0.1 μm or more and 100 μm or less.
An undercoat layer may be used between the layers in order to increase the adhesion between the layers. The type of the undercoat layer is not particularly limited as long as it enhances the adhesive strength of each layer and does not affect the properties of each layer, but an organic layer is preferable from the viewpoint of ease of handling.

In addition, two optical recording media having the above configuration are bonded together via an adhesive layer, or a reflective layer, a recording layer, a protective layer, etc. are provided on both sides as well as on one side of the substrate. Also good. Further, a multilayer optical recording medium may be obtained by forming two or more pairs of a reflective layer and a recording layer on a substrate via an intermediate layer and providing a protective layer thereon.
[Recording method of optical recording medium]
Information recording on the optical recording medium obtained as described above is usually performed by irradiating the recording layer with laser light focused to about 0.4 to 0.6 μm. When the recording layer absorbs the energy of the laser beam, thermal deformation such as decomposition, heat generation, and melting occurs in the laser beam irradiated portion. The recorded information is reproduced by reading the difference in reflectance between the portion where the thermal deformation is caused by the laser beam and the portion where the thermal deformation does not occur.

  For high-density recording, the shorter the wavelength of the laser beam used during recording, the more preferable, especially the optical recording medium of the present invention contains the above-described hydrazone metal chelate complex of the present invention in its recording layer. From the viewpoint of sufficiently exhibiting the advantages, a laser beam having a wavelength of 350 nm to 530 nm is preferable (hereinafter referred to as “the recording method of the optical recording medium of the present invention” or simply “the recording method of the present invention”).

  Typical examples of such laser light include blue laser light having center wavelengths of 405 nm and 410 nm, and blue-green high-power semiconductor laser light having a center wavelength of 515 nm. Other than these, (a) a semiconductor laser beam capable of continuous oscillation having a fundamental oscillation wavelength of 740 to 960 nm, or (b) a solid-state laser beam capable of continuous oscillation having a fundamental oscillation wavelength of 740 to 960 nm that is excited by the semiconductor laser beam. The light etc. which are obtained by wavelength-converting either by a 2nd harmonic generation element (SHG) are also mentioned.

The SHG may be any piezo element that lacks reflection symmetry, but KDP (KH ₂ PO ₄ ), ADP (NH ₄ H ₂ PO ₄ ), BNN (Ba ₂ NaNb ₅ O ₁₅ ), KN (KNbO ₃ ), LBO (LiB ₃ O ₅ ), a compound semiconductor, and the like are preferable. As a specific example of the second harmonic, in the case of a semiconductor laser having a fundamental oscillation wavelength of 860 nm, a wavelength 430 nm of its harmonic wave, and in the case of a solid-state laser excited by a semiconductor laser, a Cr-doped LiSrAlF6 crystal (basic oscillation wavelength of 860 nm). ) Wavelength of 430 nm and the like.

Of these, it is particularly preferable to use blue laser light having a center wavelength of 405 nm.
Of the absorption wavelength and absorbance of the optical recording medium, the maximum absorption wavelength (λmax) of the absorption spectrum of the optical recording medium is 350 to 450 nm, and the molar absorption coefficient at λmax is 15,000 or more. This is preferable in terms of control of the laser and high sensitivity to the laser.
{Recording sensitivity}
The dye containing the hydrazone metal chelate complex compound according to the present invention is excellent in recording laser sensitivity. Specifically, among the optical recording media containing the hydrazone metal chelate complex compound according to the present invention in the recording layer, a laser beam is preferable when irradiated with blue laser light having a center wavelength of 404 nm and NA = 0.85. Good recording pits can be formed even when the intensity is 12 mW or less, preferably 10 mW or less, and particularly preferably 7.5 mW or less. It should be noted that good recording pit formation is possible here when the recording surface of an optical recording medium is irradiated with blue laser light having a specific laser intensity, and the formation of pits can be confirmed visually or using an optical microscope. Say.
{Film property}
Moreover, the hydrazone metal chelate complex according to the present invention is excellent in film properties. That is, it is industrially advantageous in that no whitening phenomenon derived from crystallization of the compound is observed on the disk surface after the recording layer is formed by spin coating.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In the following, DEI-MS (desorption ionization mass spectrometry) analysis uses a JMS-700 MStation mass spectrometer manufactured by JEOL Ltd., acceleration voltage: 10 kV, temperature rise condition: 0-0.9 A, 1 A / Performed under the condition of minutes.

The ultraviolet-visible absorption spectrum was analyzed with a UV-3150 ultraviolet-visible near-infrared spectrophotometer manufactured by Shimadzu Corporation.
[Example 1]
<Synthesis of hydrazone ligand (L-1)>

  N-methyl-N- (2-pyridyl) hydrazine (1.0 g) manufactured by Wako Pure Chemical Industries, Ltd. and salicylaldehyde (1.0 g) manufactured by Tokyo Chemical Industry Co., Ltd. were heated and stirred in acetonitrile (5 ml) for 1 hour. . The reaction mixture was cooled to room temperature and the resulting solid was filtered off. Washing with acetonitrile (5 ml) and drying gave the pale yellow target compound (1.5 g, yield 74%).

The obtained compound was identified by DEI-MS.
DEI-MS (actual value): 227 (M +), calculated value: 227
<Synthesis of Exemplary Compound (A-1)>
The compound (L-1) (1.0 g) was suspended in ethanol (20 ml), and further dissolved by adding an aqueous solution (5 ml) of sodium hydroxide (0.18 g). To the solution was added an aqueous solution (3 ml) of nickel (II) chloride hexahydrate (0.54 g), and the resulting precipitate was filtered off and washed with ethanol (20 ml). Further drying gave the dark yellow target compound (1.0 g, yield 88%).

λmax (MeCN): 415 nm
ε at λmax: 23,000
The ultraviolet-visible absorption spectrum in acetonitrile of the obtained hydrazone metal chelate complex is shown in FIG. From FIG. 1, it is clear that an absorption shape that is sharp and has a good bottom is confirmed, and it is clear that the obtained hydrazone metal chelate complex has a characteristic that contributes to an improvement in recording sensitivity. The obtained complex had an ultraviolet-visible absorption maximum of 365 nm and an OD coefficient of 91 g / L.
About the obtained compound (A-1), as a result of testing the solubility with respect to an application | coating solvent by the method shown below, it melt | dissolves completely in both the density | concentration of 1.0 weight% and 1.5 weight%. It was confirmed.
<Solubility test>
As a coating solvent, 2,2,3,3-tetrafluoropropanol was used, and the concentration of the compound (A-1) was 1.0% by weight and 1.5% by weight, at 20 ° C. and normal pressure for 30 minutes. After sonication, the solution was dropped on a filter paper (quantitative filter paper “No. 5C” manufactured by Toyo Roshi Kaisha Co., Ltd.) and dried at room temperature for 24 hours to visually check whether crystal residues of undissolved components were present on the filter paper. Observed.
[Example 2]
<Synthesis of Exemplary Compound (A-2)>
The compound (L-1) (0.23 g) was suspended in ethanol (10 ml), and further dissolved by adding a 1M aqueous sodium hydroxide solution (1 ml). Cobalt chloride (
II) A methanol solution (1 ml) of hexahydrate (0.24 g) was added, and the resulting precipitate was filtered off and washed with ethanol (10 ml). Further drying gave an orange target compound (0.25 g, yield 96%).

λmax (MeCN): 393 nm
ε at λmax: 23,000
About the obtained compound (A-2), as a result of testing the solubility with respect to a coating solvent by the method shown in Example 1, in any of density | concentration of 1.0 weight% and 1.5 weight%, it was completely. It was confirmed that it was dissolved.
[Example 3]
<Synthesis of Exemplary Compound (A-3)>
The compound (L-1) (0.23 g) was suspended in ethanol (10 ml), and further dissolved by adding a 1M aqueous sodium hydroxide solution (1 ml). To the solution was added an aqueous solution (1 ml) of manganese (II) chloride tetrahydrate (0.20 g), and the formed precipitate was filtered off and washed with ethanol (10 ml). Further drying gave an orange target compound (0.25 g, yield 96%).

λmax (MeCN): 410 nm
ε at λmax: 21,000
The obtained compound (A-3) was tested for solubility in a coating solvent by the method shown in Example 1. As a result, it was found that the compound (A-3) was completely dissolved in both the concentration of 1.0% by weight and 1.5% by weight. It was confirmed that it was dissolved.
[Comparative Example 1]
The compound (B-2) described in Patent Document 2 was tested for solubility in a coating solvent by the method shown in Example 1. As a result, the concentration was 1.0% by weight and 1.5% by weight. It was confirmed that there were many insoluble components.

[Comparative Example 2]
In the compound (B-3) which is a salen metal complex compound, the solubility in the coating solvent was tested by the method shown in Example 1. As a result, in any of the concentrations of 1.0 wt% and 1.5 wt% It was also confirmed that there were many insoluble components.

  The results of the solubility test shown in Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 1.

From Table 1, the following is clear.
The hydrazone metal chelate complexes shown in Examples 1 to 3 are completely dissolved without any undissolved components being confirmed on the filter paper even when a 1.5 wt% solution is used.
On the other hand, the solubility of the compounds shown in Comparative Examples 2 and 3 is remarkably poor, and it is clear that the compound of the present invention is excellent in solubility in a coating solvent.
[Example 4]
<Preparation of recording medium>
Further, the obtained compound (A-2) was dissolved in 2,2,3,3-tetrafluoropropanol at a concentration of 1.0% by weight and fine dust was removed by filtration. A transparent coating film (recording layer) having a film thickness of about 50 nm is formed by dropping onto an injection-molded polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm, applying by spin coating (4900 rpm), and drying at 80 ° C. for 30 minutes. Thus, an optical recording medium was produced.
When the recording sensitivity of the obtained optical recording medium was tested by the following method, the maximum recording sensitivity at which formation of recording pits was confirmed was 7.5 mW.
<Recording sensitivity test>
Semiconductor laser light having a central wavelength of 404 nm and NA = 0.85 was irradiated, and the maximum recording sensitivity at which formation of recording pits was confirmed by an optical microscope was measured.

Further, when the obtained optical recording medium was tested for light resistance by the method described below, the dye residual ratio was 94%.
<Light resistance test>
With respect to the recording layer after irradiation with a xenon lamp for 40 hours at an irradiation intensity of 0.55 W / m ² under the conditions of a temperature of 58 ° C. and a humidity of 50%, the residual ratio of the dye is determined based on the absorbance before and after irradiation at the absorption maximum wavelength. Asked.
[Comparative Example 3]
For compound (B-1) described in Patent Document 1, an optical recording medium was produced in the same manner as in Example 1, and the obtained optical recording medium was tested for light resistance by the method described above. The residual rate was less than 10%.

  Table 2 summarizes the results of the recording sensitivity test and the light resistance test shown in Example 3 and Comparative Example 3. From Table 2, it became clear that the optical recording medium prepared using the present invention is excellent in terms of sensitivity and light resistance to blue laser light.

Claims (4)

A dye for forming a recording layer of an optical recording medium, comprising at least one hydrazone chelate complex represented by the following general formula (1):

(In general formula (1), ring A and ring C represent a nitrogen-containing heteroaromatic ring which may have a substituent, and ring B and ring D represent an aromatic ring which may have a substituent. , R ^{1 to} R ⁴ each independently represents a hydrogen atom or a monovalent substituent having 20 or less carbon atoms, X ¹ and X ² each independently represent a group 15 or 16 atom, and M represents a divalent transition metal Represents a cation, and when X ¹ and / or X ² is a Group 15 atom, the atom may further have a monovalent substituent having 20 or less carbon atoms.)   The dye for forming a recording layer of an optical recording medium according to claim 1, wherein M is a cation of cobalt.   It has at least a substrate and a recording layer formed on the substrate, and the recording layer is formed using the recording layer forming dye of the optical recording medium according to claim 1 or 2. An optical recording medium characterized by the above.   4. A recording method for an optical recording medium, wherein the optical recording medium according to claim 3 is recorded using a laser beam having a wavelength of 350 to 530 nm.