JP2007090768A - Dye for recording layer formation of optical recording medium and optical recording medium using the same - Google Patents

Abstract

（式中、Ｒ^１及びＲ^２は、それぞれ独立に、１５族又は１６族原子の１価のアニオンを有する基を表し、Ｘ^１及びＸ^２は、それぞれ独立に、それぞれ置換基を有していても良い芳香環又は非芳香族性炭化水素基を表すが、Ｘ^１又はＸ^２の少なくとも一方は、置換基を有していても良い芳香環である。Ｘ^３は、水素原子又は１価の基を表す。）
【選択図】なし
Disclosed is a Schiff base metal complex compound dye for forming a recording layer of an optical recording medium that is excellent in light resistance and extinction coefficient and is compatible with optical recording using blue laser light.
A divalent anion Schiff base represented by the following general formula (1) and a transition metal cation, and a Schiff base metal complex which may contain other anions and cations. A dye for forming a recording layer of an optical recording medium.

(In the formula, R ¹ and R ² each independently represent a group having a monovalent anion of a group 15 or group 16 atom, and X ¹ and X ² each independently have a substituent. Represents an aromatic ring or a non-aromatic hydrocarbon group, and at least one of X ^{1 and} X ² is an aromatic ring which may have a substituent, and X ³ is a hydrogen atom or a monovalent group. Represents a group of
[Selection figure] None

Description

  The present invention relates to a Schiff base metal 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. Also, in order to increase the recording density on optical disks, the wavelength of the laser light used for recording is shortened from the center of the conventional semiconductor laser emission wavelength of 780 nm to the blue light region of about 405 nm or less. Is being considered.
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 a laser beam and absorbing the irradiation energy in the recording layer, so that heat such as decomposition, evaporation, dissolution, etc. is generated in the recording layer, reflecting layer or substrate of the laser beam irradiation portion. 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 the thermal deformation or the change in the dye structure due to the laser beam irradiation occurs and the portion where the change 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. Since the information can be recorded more efficiently as the extinction coefficient of the dye with respect to the laser beam is larger, there is a demand for a dye having a larger extinction coefficient.

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. .
Information is also read out by laser light, but the laser light used for reading is weaker than the laser light used for recording. However, when the light resistance of the dye forming the recording layer of the optical recording medium is inferior, the dye is decomposed even by irradiation with weak laser light that is the readout light, which causes a data error when reading the recording data. Become. Even when the recording surface of an optical recording medium is irradiated with sunlight, illumination, or the like for a long time, since the dye is decomposed when the dye is inferior in light resistance, the recording data of the optical recording medium can be stored for a long time. It becomes difficult. Therefore, the recording layer forming dye of the optical recording medium needs to be rich in light resistance.

The Schiff base and derivatives thereof are one of the compounds expected to be applied to an optical recording medium compatible with blue laser light because of its simplicity of synthesis and maximum absorption mainly in the vicinity of 300 to 500 nm. (For example, see Patent Documents 1 to 4.) However, the Schiff base metal complexes described in these Patent Documents have insufficient light resistance.
For this reason, it has been considered that the Schiff base metal complex cannot be used as a dye for an optical recording medium while having an absorption waveform useful as an optical recording medium for blue laser light.
JP 2003-266939 A JP 2005-509694 A JP 2005-515914 A International Publication No. 2004-102551

  An object of the present invention is to provide a Schiff base metal complex-based dye for forming a recording layer of an optical recording medium having a large extinction coefficient, excellent light resistance, and compatible with optical recording using blue laser light. .

  As a result of intensive studies to solve the above problems, the inventors of the present invention consist of a divalent anion Schiff base represented by the general formula (1) and a transition metal cation, and contain other anions and cations. The Schiff base metal complex, which may be used, is remarkably excellent in the extinction coefficient and light resistance, and it has been found that an optical recording medium using this in the recording layer can be recorded well with blue laser light, thereby completing the present invention.

  That is, the gist of the present invention is a Schiff base metal comprising a divalent anion Schiff base represented by the following general formula (1) and a transition metal cation, and may contain other anions and cations. It is a dye for forming a recording layer of an optical recording medium characterized by comprising a complex.

(In the formula, R ¹ and R ² each independently represent a group having a monovalent anion of a group 15 or group 16 atom, and X ¹ and X ² each independently have a substituent. Represents an aromatic ring or a non-aromatic hydrocarbon group, and at least one of X ^{1 and} X ² is an aromatic ring which may have a substituent, and X ³ is a hydrogen atom or a monovalent group. Represents a group of

  The recording layer forming dye of the optical recording medium according to the present invention is excellent in light resistance, film forming property, 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 obtained at low cost with good film formability. It becomes possible to provide.

  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 divalent anion Schiff base that forms the recording layer forming dye of the optical recording medium according to the present invention is represented by the following general formula (1).

In the present invention, “may have a substituent” means that one or more substituents may be present.
{R ¹ , R ² }
In General Formula (1), R ¹ and R ² each independently represent a group having a monovalent anion of a Group 15 or Group 16 atom. ^{Specifically, = N -, = P -} , 1 -valent anion of Group 15 atoms, such ^{as, -N - -R 3, -P -} -R 3,

Group containing a monovalent anion of Group 15 atoms, such ^{as, -O -, -S -, -Se} - 1 monovalent anion of Group 16 atoms such as,

And groups containing a monovalent anion of a group 16 atom such as

R ³ represents a hydrogen atom or a monovalent group.
Specifically, a chain alkyl group having 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms; a chain alkenyl group having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms; , Preferably a chain alkynyl group having 2 to 8 carbon atoms; an aryl group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, preferably 5 to 8 carbon atoms, and 3 to 3 carbon atoms. 20, preferably 5 to 8 hydrocarbon ring groups such as cycloalkenyl groups; 5- or 6-membered monocyclic rings or 2-6 condensed rings, preferably monocyclic rings or 2-3 condensed rings, and nitrogen as a hetero atom A heteroaryl group containing one selected from an atom, an oxygen atom and a sulfur atom, a 5- or 6-membered monocyclic ring or a 2-6 condensed ring, preferably a monocyclic ring or a 2-3 condensed ring, Selected from nitrogen, oxygen and sulfur atoms A heterocyclic group such as a heterocycloalkyl group; an alkylcarbonyl group having 2 to 18 carbon atoms, preferably 2 to 8 carbon atoms; an alkylsulfonyl group having 1 to 18 carbon atoms, preferably 2 to 8 carbon atoms. It is done.
Among these, as R ³ , a chain alkyl group, an alkylcarbonyl group, and an alkylsulfonyl group are preferable.

Among these, R ¹ and R ² are each independently preferably a group containing a monovalent anion of a group 16 atom or a monovalent anion of a group 16 atom because the stability of the Schiff base metal complex is improved. A group containing a monovalent anion of an oxygen atom or a monovalent anion of an oxygen atom is preferable because the synthesis of a Schiff base metal complex is easy.
When X ¹ and X ² to which R ¹ and R ² are bonded are aromatic rings, R ¹ and R ² and the C═N bond are close to each other in complex formation. It is preferable because a stable complex can be formed. The number of atoms between R ¹ , R ² and the C═N structure is preferably 2-3, and most preferably 2.
Further, when X ¹ and X ² to which R ¹ and R ² are bonded are non-aromatic hydrocarbon groups, the positional relationship between R ¹ and R ² and the C═N structure is R ¹ , number of atoms between R ² and the C = N structure is preferably 1-2.
R ¹ and R ² may be the same as or different from each other.

{X ¹ , X ² }
In the general formula (1), X ¹ and X ² each independently represent an aromatic ring which may have a substituent or a non-aromatic hydrocarbon group which may have a substituent. However, at least one of X ¹ and X ² represents an aromatic ring which may have a substituent.

The aromatic ring represented by X ¹ and X ² means a ring having aromaticity, that is, a ring having a (4q + 2) π electron system (q is a natural number). A 5- or 6-membered aromatic ring composed of a single ring or a condensed ring having 2 to 6 carbon atoms, such as an aryl group usually having 5 to 16 carbon atoms and a heteroaryl group usually having 5 to 16 carbon atoms. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom.

Examples of the aromatic ring represented by X ¹ and X ² include 6-membered rings such as a furan ring, a thiophene ring, a pyrrole ring, an imidazole ring, a thiazole ring, and an oxadiazole ring, a benzene ring, a pyridine ring, and a pyrazine ring. And 5- or 6-membered condensed rings such as a member ring, naphthalene ring, phenanthrene ring, azulene ring, pyrene ring, quinoline ring, isoquinoline ring, quinoxaline ring, benzofuran ring, carbazole ring, dibenzothiophene ring, anthracene ring, etc. . Of these, a single ring is preferable from the viewpoint of easy synthesis, a 6-membered ring is more preferable, and a benzene ring is particularly preferable.

Examples of the non-aromatic hydrocarbon group represented by X ¹ and X ² include a chain alkyl group such as a methyl group, an ethyl group, and a propyl group, a cycloalkyl group such as a cyclohexyl group, a vinyl group, and a 1-propenyl group. And the like, and the like. Moreover, the non-aromatic hydrocarbon ring which contains a hetero atom and a double bond in a ring is also mentioned.

When the non-aromatic hydrocarbon group represented by X ¹ and X ² is a non-aromatic hydrocarbon ring, the hetero atom that may be contained in the ring includes a nitrogen atom, an oxygen atom, A sulfur atom etc. are mentioned. Examples of the non-aromatic hydrocarbon ring include the following structures.

Among these, it is preferable that the part c is a bonding position to R ¹ or R ² and the part d is a bonding position to the C═N structure.
As the non-aromatic hydrocarbon group, those having 1 to 3 carbon atoms are preferably used in that a stable complex can be constructed upon complex formation.

<Substituent which X ¹ and X ² may have>
Examples of the group that may be substituted with the aromatic ring and non-aromatic hydrocarbon group represented by X ¹ and X ² include a chain alkyl group, a chain alkenyl group, a chain alkynyl group, and a hydrocarbon ring group A heterocyclic group, an alkoxy group, an alkylcarbonyl group, a (hetero) aryloxy group, a (hetero) aralkyloxy group, an amino group optionally having a substituent, a nitro group, a cyano group, an ester group, and a substituent. Examples thereof may include a carbamoyl group, a halogen atom, and a hydroxyl group that may be included.

As the chain alkyl group, carbon number such as methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, iso-butyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group, etc. Is usually 1-20, preferably 1-10 linear or branched.
As the chain alkenyl group, a straight chain or branched chain having usually 2 to 20, preferably 2 to 10, carbon atoms such as vinyl group, propenyl group, butenyl group, 2-methyl-1-propenyl group, hexenyl group, octenyl group, etc. The thing of the shape is mentioned.
The chain alkynyl group is a straight chain or branched chain having usually 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. The thing of the shape is mentioned.

  The hydrocarbon ring group usually has 3 to 20 carbon atoms, such as a cyclopropyl group, a cyclohexyl group, or a tetradecahydroanthranyl group, preferably 5 to 10 carbon atoms such as a cycloalkyl group or a cyclohexenyl group. An aryl group having usually 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 and a ferrocenyl group, preferably 5 to 10, is included.

  Examples of the heterocycle include a heteroaryl group composed of a 5- to 6-membered monocyclic ring or a 2-6 condensed ring, and a heterocycloalkyl group composed of a 5- to 6-membered monocyclic ring or a 2-6 condensed ring. Examples of the atom 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, octahydroquinolinyl group, quinolinyl group or the like 5 or Examples include 6-membered 2-6 condensed rings.

The alkoxy group usually has 1 carbon number such as methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, iso-butoxy group, sec-butoxy group, tert-butoxy group, hexyloxy group, octyloxy group, etc. To 9, preferably 2 to 8.
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.

As the (hetero) aryloxy group, an aryloxy group, a 2-thienyloxy group, a 2-furyloxy group, a 2-quinolyloxy group having usually 6 to 18, preferably 6 to 10 carbon atoms, such as a phenoxy group and a naphthyloxy group. Examples thereof include heteroaryloxy groups having 5 to 18 carbon atoms, preferably 5 to 10 carbon atoms, and those containing a hetero atom selected from a nitrogen atom, an oxygen atom, a sulfur atom and the like.
As the (hetero) aralkyloxy group, an aralkyloxy group, a 2-thienylmethoxy group, a 2-furylmethoxy group such as a benzyloxy group, a phenethyloxy group, or a naphthylmethoxy group, which usually has 7 to 18 carbon atoms, preferably 7 to 12 carbon atoms. A heteroaralkyloxy group having 6 to 18 carbon atoms, preferably 6 to 10 carbon atoms, such as a group, a 2-quinolylmethoxy group, and the like, including a hetero atom selected from a nitrogen atom, an oxygen atom, a sulfur atom, and the like It is done.

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, preferably 3 to 10, carbon atoms such as an ethylamino group, a dimethylamino group, a methylethylamino group, a dibutylamino group, and a piperidino group.

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

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.

As the ester group, 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 have 2 to 20, preferably 2 to 10 carbon atoms. Things.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

When the aromatic ring represented by X ¹ or X ² has two or more substituents, the substituents may be bonded to each other to form a cyclic structure that may contain a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. For example, when X ¹ or X ² is a benzene ring, the following structure is exemplified as an example in which substituents of the benzene ring are bonded to each other to form a cyclic structure that may contain a hetero atom. Especially, it is preferable that the part a is a bonding position to R ¹ or R ² and the part b is a bonding position to the C═N structure.

It is preferable that the aromatic ring or non-aromatic hydrocarbon group represented by X ¹ or X ² has a substituent since the solubility of the dye in the solvent used for forming the recording layer is improved.
In particular, when a polar solvent such as tetrafluoropropanol or methyl cellosolve is used as the solvent, the aromatic ring represented by X ¹ or X ² has a polar substituent such as an N, N-disubstituted carbamoyl group or an ester group. When a non-polar solvent such as methylene chloride, dibutyl ether or methylcyclohexane is used as the solvent, the aromatic ring or non-aromatic hydrocarbon group represented by X ¹ or X ² is an alkyl group or an alkoxy group. It preferably has a nonpolar substituent such as a group.
Moreover, when the aromatic ring or non-aromatic hydrocarbon group represented by X ¹ or X ² does not have a substituent, it is preferable in that the synthesis of the Schiff base is easy.

<Molecular weight of ^{X 1} and ^{X 2>}
The molecular weight of the aromatic ring which may have a substituent represented by X ¹ and X ² or the non-aromatic hydrocarbon group which may have a substituent is preferably 700 or less. If the molecular weights of the groups represented by X ¹ and X ² are too large, there is a risk that the recording sensitivity will decrease due to a decrease in absorbance.

<Preferred combinations of ^{X 1} and ^{X 2>}
At least one of X ¹ and X ² needs to be an aromatic ring which may have a substituent, for the reason that the absorption maximum wavelength is adjusted to an appropriate position as an optical recording dye. It is preferable from the viewpoint of synthesis that both X ¹ and X ² are aromatic rings, and when either ^one of X ¹ and X ^{2 is} a non-aromatic hydrocarbon group which may have a substituent, This is preferable because the absorption maximum wavelength of the obtained dye is easily shifted to the short wavelength side.

{X ³ }
In general formula (1), X ³ represents a hydrogen atom or a monovalent group.
Examples of the monovalent group represented by X ³ include an aryl group having 6 to 12 carbon atoms which may have a substituent, a 5- to 6-membered monocyclic ring or a 2 to 6 condensed ring, and nitrogen as a hetero atom. An aromatic ring group which may have a substituent such as a heteroaryl group which may have a substituent, including those selected from atoms, oxygen atoms and sulfur atoms; A linear alkyl group having 1 to 20 carbon atoms, preferably 2 to 8 carbon atoms; a chain alkenyl group having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms; 2 to 20 carbon atoms, preferably 2 carbon atoms A non-aromatic group such as a cycloalkyl group having 3 to 20 carbon atoms, preferably a cycloalkyl group having 5 to 16 carbon atoms, and a cycloalkenyl group having 3 to 20 carbon atoms, preferably 5 to 10 carbon atoms. Hydrocarbon ring group: 5-6 membered monocyclic ring or 2-6 condensed ring, preferably Or a heterocycloalkyl group containing a monocyclic ring or a condensed ring having 2 to 3 heteroatoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, etc .; an alkoxy having usually 1 to 9, preferably 2 to 6 carbon atoms A group; an alkylcarbonyl group having usually 2 to 18 carbon atoms, preferably 2 to 10 carbon atoms; one having 5 to 18 carbon atoms, preferably 5 to 10 carbon atoms, and a hetero atom selected from a nitrogen atom, an oxygen atom and a sulfur atom A (hetero) aryloxy group which may contain any one of carbon atoms of 5 to 18, preferably 6 to 10, and a hetero atom selected from a nitrogen atom, an oxygen atom and a sulfur atom. (Hetero) aralkyloxy group; an amino group, usually an alkylamino group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, usually 5 to 30 carbon atoms, preferably 6 to 15 (he B) An amino group which may have a substituent such as an arylamino group; a carbamoyl group, which may have a substituent such as an alkylcarbamoyl group usually having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms. A carbamoyl group; an ester group usually having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms; a nitro group; a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom;

When X ³ is an aromatic ring which may have a substituent, the aromatic ring represented by X ¹ or X ² may have as the substituent that the aromatic ring may have. The same thing as a substituent is mentioned.
Also, when X ³ is an aromatic ring which may have a substituent group, when the aromatic ring represented by X ³ has two or more substituents, the substituents are bonded to each other heteroatom An annular structure that may be included may be formed. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. For example, when X ³ is a benzene ring, the following structure is exemplified as an example in which substituents of the benzene ring are bonded to each other to form a cyclic structure that may contain a hetero atom. Especially, it is preferable that the part of e is a coupling | bonding position to a C = N structure.

When X ³ is a hydrogen atom, a Schiff base can be easily synthesized, and a dye obtained when X ³ is a monovalent group tends to improve the film formability. The molecular weight of X ³ is preferably 500 or less, in particular 100 or less. If the molecular weight of X ³ is too large, there is a risk that lowering of recording sensitivity due to the decrease in absorbance occurs. Among these, X ³ is particularly preferably a hydrogen atom, a halogen atom, a methyl group, a trifluoromethyl group, or the like.

  A typical Schiff base according to the present invention is represented by the following general formula (2) or general formula (3).

In the formula, ring A and ring B each independently represent an aromatic ring which may have a substituent, but at least one of ring A and ring B is a benzene ring which may have a substituent. is there. Preferably, one of ring A and ring B represents a benzene ring which may have a substituent, and the other represents a benzene ring, a pyridine ring, a thiophene ring or a quinone ring which may have a substituent.
R ¹ and ^{R 2} has the same meaning as ^R 1, ^{R 2} in the general formula (1), ^{R 1} is the o- (ortho) position of Ring A, ^{R 2} is in o- (ortho) position of Ring B Are connected.
X ³ has the same meaning as ^{X 3} in the general formula (1).

Wherein, ^{X 3} has the same meaning as ^{X 3} in the general formula (1).
One of X ⁴ and X ⁵ represents a benzene ring which may have a substituent, and the other represents a chain hydrocarbon group which may have a substituent or a non-aromatic which may have a substituent. Represents an aromatic cyclic hydrocarbon group. The cyclic hydrocarbon group may contain a hetero atom in the ring.
R ¹ and ^{R 2} has the same meaning as ^R 1, ^{R 2} in the general formula (1), ^{R 1} or ^{R 2} bonded to the benzene ring is attached to o- (ortho) position of the benzene ring . R ¹ or R ² bonded to the chain hydrocarbon or cyclic hydrocarbon group is bonded to the C═N structure via 1 to 2 atoms.

{Transition metal cations}
Any transition metal cation that can form a Schiff base metal complex according to the present invention by binding with a Schiff base can be used as long as it can form a metal complex with a Schiff base. Specific examples include Ti, V, Cr, Mn, Examples include cations such as Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, Pt, Au, and Er.
The transition metal cation forming the Schiff base metal complex is preferably a cation of a transition metal element in the fourth period from the economical viewpoint, more preferably a cation of Ti, Mn, Fe, Co, Ni, Cu, Ti, Ni Cu cations are particularly preferred.

The Schiff base metal complex according to the present invention may contain an anion other than the Schiff base and a cation other than a transition metal cation.
Anions other than the Schiff base include alcohols, phenols, carboxylic acids, phosphonic acids, halogens, perchloric acids, periodic acids, cyanic acids, isocyanic acids, isothiocyanic acids, azides, nitric acids, carbonic acids, bicarbonates, sulfuric acids, sulfuric acids. Substituted or unsubstituted sulfuric acid such as hydrogen acid and methylsulfuric acid; methanesulfonic acid; trifluoromethanesulfonic acid; tosylic acid: substituted or unsubstituted such as phosphoric acid, hydrogen phosphate, dihydrogen phosphate, and phenyl phosphate Phosphoric acid, phosphorous hexafluoride, antimony hexafluoride; substituted or unsubstituted phosphinic acids such as phosphinic acid and methylphosphinic acid; substituted or unsubstituted boronic acids such as tetraphenylboronic acid; benzenesulfonic acid; acetic acid; Examples include anionized fluoroacetic acid and the like.
As anions other than the Schiff base, those having a molecular weight of 300 or less are preferable. If the molecular weight is too large, the absorbance of the resulting dye may be reduced and the recording sensitivity may be reduced. Of these, a perchlorate anion and a phosphorus hexafluoride anion are preferred because the laser sensitivity of the resulting dye is improved.

Examples of the cation other than the transition metal cation include a hydrogen cation, an alkali metal cation, an alkaline earth metal cation, a substituted or unsubstituted ammonium cation (such as methylammonium cation and tetraethylammonium cation), and a substituted or unsubstituted phosphonium cation ( Phosphonium cations, methylisopropylphosphonium cations, etc.), N-substituted pyridinium cations, and the like.
Cations other than transition metals are also preferably those having a molecular weight of 300 or less. If the molecular weight is too large, the absorbance of the resulting dye may be reduced and the recording sensitivity may be reduced. Of these, a substituted or unsubstituted ammonium cation and N-substituted pyridinium cation are preferable because the laser sensitivity of the resulting dye is improved.
The Schiff base metal complex according to the present invention is zero when the cation valence and the anion valence are summed.

{Molecular weight}
An optical recording medium comprising a Schiff base metal complex composed of a divalent anion Schiff base represented by the general formula (1) according to the present invention and a transition metal cation, and may contain other anions and cations. The molecular weight of the recording layer forming dye is usually 1,500 or less, preferably 1,000 or less. If the molecular weight is too large, the absorbance of the dye is lowered, and the recording sensitivity may be lowered.
The recording layer forming dye according to the invention is preferably insoluble in water.

{Concrete example}
Specific examples of the recording layer forming dye according to the present invention are shown below.

  The recording layer forming dye according to the invention may be used alone or in combination of two or more.

{Synthesis method}
The recording layer forming dye of the optical recording medium according to the present invention can be easily synthesized, for example, by the following method.
In other words, a Schiff base is synthesized by stirring a compound having a carbonyl group and a compound having an amino group from room temperature in the presence or absence of a solvent under heating conditions, and further, the metal salt acts in the presence or absence of a solvent. The desired Schiff base metal complex can be obtained.

  The reason why the recording layer forming dye of the optical recording medium according to the present invention is excellent in light resistance is not clear, but the Schiff base anion in the compound is a divalent anion and is ionically bonded to the metal at two points. This is presumably due to the fact that the nitrogen atom having the C = N structure is coordinated to the metal.

[Optical recording medium]
The optical recording medium of the present invention comprises a substrate comprising a divalent anion Schiff base represented by the general formula (1) and a transition metal cation on the substrate, and may contain other anions and cations. A recording layer containing a recording layer forming dye composed of a base metal complex is formed. The proportion of the recording layer-forming dye according to 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.

  As the substrate, a glass or plastic that is transparent to the laser beam to be used is preferably used. Examples of the plastic include acrylic resin, methacrylic resin, polycarbonate resin, cycloolefin resin, vinyl chloride resin, vinyl acetate resin, nitrocellulose, polyester resin, polyethylene resin, polypropylene resin, polyimide resin, polystyrene resin, and epoxy resin. In view of productivity, cost, hygroscopic resistance, etc., a polycarbonate resin or cycloolefin resin injection molded is preferred.

  The recording layer may contain a binder. By containing a binder, the film formability can be improved. 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 in the recording layer is too high, the recording sensitivity is remarkably lowered. Therefore, an amount is used so that the ratio of the dye according to the present invention in the recording layer falls within the above range.

  The recording layer may contain a singlet oxygen quencher, a recording sensitivity improver, etc. in order to improve stability and light resistance.

  Examples of the singlet oxygen quencher include chelates 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 5 to 30% by weight based on the recording layer forming dye according to the present invention, and the recording sensitivity improver is usually 10 to 30% by weight based on the recording layer forming dye according to the present invention. Used in

  The recording layer may contain a dye other than the recording layer forming dye according to the present invention, if necessary. Other dyes have absorption in the laser light wavelength range for recording, absorb the energy of the irradiated laser light, and decompose, evaporate, dissolve, etc. into the recording layer, reflective layer or substrate of the irradiated part. Those that form pits with thermal deformation are preferred. 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 the other dyes include metal-containing azo dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, metal-containing indoaniline dyes, and triarylmethane dyes. , Merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes, and the like. May be used in combination.

For forming the recording layer, a generally used thin film forming method such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, or 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. If the recording layer containing the dye is too thin, the influence of thermal diffusion cannot be suppressed and good recording is difficult to obtain. Further, distortion is likely to occur in the recording signal, and it is difficult to increase the signal amplitude. On the other hand, if the recording layer is too thick, the reflectance is reduced, and the reproduction signal characteristic tends to be poor.

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 others according to the present invention are used. A coating solution is prepared by dissolving the dye and the like in a solvent.
The solvent is not particularly limited as long as it does not attack the substrate, and ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone, cellosolv solvents such as methyl cellosolve and ethyl cellosolve Chain hydrocarbon solvents such as n-hexane and n-octane, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, t-butylcyclohexane and cyclooctane, Ether solvents such as diisopropyl ether and dibutyl ether, perfluoroalkyl alcohol solvents such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol, and hydroxy solvents such as methyl lactate, ethyl lactate and methyl isobutyrate. Ether-based solvents and the like. Of these, perfluoroalkyl alcohol solvents are preferred from the industrial aspect, and TFP (tetrafluoropropanol), which is a solvent that is generally used industrially for this purpose, is particularly preferred. In addition, these solvents may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The proportion of the recording layer forming dye according to the present invention in the coating solution is appropriately determined according to the solvent solubility of the dye, but is usually 0.7% by weight or more, preferably 1.0% by weight or more, Usually, it is 10 wt% or less, preferably 3.0 wt% or less. If the proportion of the dye in the coating solution is too low, the formation efficiency of the recording layer may be deteriorated. If the ratio of the dye in the coating solution is too high, problems such as dye crystallization may occur in the film forming process.

  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 in order to improve the adhesion between the layers, or to increase 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.

  Further, two optical recording media having the above configuration may be bonded via an adhesive layer to form a double-sided recording type optical recording medium, or the recording layer may be provided on both sides of the substrate or on one side.

  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, and information is recorded. 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, the better, and laser light with a wavelength of 350 nm to 530 nm is particularly preferable. 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 piezoelectric element that lacks reflection symmetry, but KDP, ADP, BNN, KN, LBO, 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 of 430 nm of the harmonic wave, and in the case of a solid-state laser excited by a semiconductor laser, a Cr-doped LiSrAlF ₆ crystal (basic oscillation wavelength). The wavelength of the double wave from 860 nm) is 430 nm.

  Of the absorption wavelength and absorbance of the optical recording medium, the preferred one depends on the type of laser light used for recording. For example, for a blue laser having a central wavelength of 405 to 410 nm, the maximum absorption wavelength (λmax) of the absorption spectrum of the optical recording medium is 300 to 450 nm, and the molar extinction coefficient (ε) at λmax is 15,000. As described above, particularly for a blue laser having a center wavelength of 430 nm or more, the maximum absorption wavelength (λmax) of the absorption spectrum of the optical recording medium is 350 to 490 nm. The extinction coefficient (ε) is preferably 15,000 or more, particularly preferably 20,000 or more.

  The recording layer forming dye comprising the Schiff base metal complex represented by the general formula (1) according to the present invention is suitable for an optical recording medium using these blue laser beams. Further, since the Schiff base metal complex according to the present invention is easily synthesized, an inexpensive optical recording medium can be provided.

<Light resistance>
It consists of a divalent anion Schiff base represented by the general formula (1) used in the recording layer of such an optical recording medium and a transition metal cation, and may contain other anions and cations. A dye for forming a recording layer of an optical recording medium composed of a compound in which a divalent anion having a Schiff base skeleton and a transition metal cation form a complex, represented by a good Schiff base metal complex, has a temperature of 58 ° C. and humidity Under the condition of 50%, the dye residual ratio when irradiated with a xenon lamp (intensity 0.55 W / m ² ) for 40 hours is usually 90% or more, particularly 95% or more, and is excellent in light resistance. A particularly preferable dye has a dye residual ratio of 95% or more even when irradiated with a xenon lamp (intensity 0.55 W / m ² ) for 80 hours, particularly 120 hours under the conditions of a temperature of 58 ° C. and a humidity of 50%. .
In such a light resistance test, first, a solution containing a dye is applied on a plastic substrate so that the film thickness after drying is about 50 nm, and then dried to obtain a layer containing the dye. The obtained pigment-containing layer is 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 is compared. And determine the residual ratio of the pigment.

<Recording sensitivity>
Further, an optical recording medium containing a dye composed of a Schiff base metal complex according to the present invention in a recording layer has a laser intensity of 10 mW or less, particularly 7 when irradiated with blue laser light having a center wavelength of 404 nm and NA = 0.85. Good recording pits can be formed even at 0.5 mW or less, and the recording laser sensitivity is excellent.

  Furthermore, the dye comprising the Schiff base metal complex according to the present invention is excellent in film formability since no whitening phenomenon due to 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, proton NMR analysis was performed in a deuterated chloroform solvent using a Bruker AV400M nuclear magnetic resonance spectrometer (400 MHz).
DEI-MS (desorption ionization mass spectrometry) analysis was performed using a JMS-700 MStation mass spectrometer manufactured by JEOL Ltd. under conditions of acceleration voltage: 10 kV, temperature rising condition: 0-0.9 A, 1 A / min. went.
Thermal analysis uses differential thermal thermogravimetric analyzer EXSTAR6000 TG-DTA manufactured by SII Nanotechnology, Inc., sample amount: 2.0 mg, temperature rise: 10 ° C./min, nitrogen flow rate: 0.2 L / min. Then, measurement was performed using an aluminum pan. The thermal decomposition temperature was a temperature at which the weight was reduced by 10% when thermal analysis was performed under the above conditions.

[Production of optical recording medium]
The recording layer forming dye is dissolved in methylene chloride so as to be 1.0% by weight, fine dust is removed by filtration, and the resulting solution is injected with a cycloolefin resin (Zeon Corporation "ZEONEX"). It is dropped onto a substrate having a diameter of 120 mm and a thickness of 1.2 mm obtained by molding, applied by spin coating (4900 rpm), and dried at 80 ° C. for 30 minutes to form a transparent coating film (film thickness of about 50 nm). Thus, an optical recording medium was obtained.

The obtained optical recording medium was irradiated with semiconductor laser light having a central wavelength of 404 nm and NA = 0.85, and the maximum recording sensitivity at which formation of good recording pits was confirmed was measured.
The obtained optical recording medium was subjected to a light resistance test. An optical recording medium is irradiated with a xenon lamp (intensity 0.55 W / m ² ) for 40 hours under conditions of a temperature of 58 ° C. and a humidity of 50%, and the change in absorbance at the absorption maximum wavelength before and after irradiation is measured. The pigment residual ratio was determined.

[Example 1]
<Synthesis of Compound (A-1)>
1.0 g of 3,5-di-tert-butylsalicylaldehyde (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.50 g of 2-aminophenol were heated and stirred for 1 hour under reflux conditions in 10 ml of ethanol. After adding 0.50 g of potassium hydroxide to the obtained solution and dissolving it, a saturated aqueous solution of 2.0 g of nickel (II) chloride hexahydrate was added dropwise to form a precipitate. The resulting precipitate was filtered off and purified by silica gel column chromatography to obtain yellow crystals (0.30) of compound (A-1).

The obtained compound was analyzed by proton NMR, DEI-MS analysis and thermal analysis. The results are shown below.
λmax: 407 nm
ε at λmax (number of molar absorption systems): 19,000
Thermal decomposition temperature: 430 ° C
DEI-MS: Measured value: 772 (M +), calculated value 772

<Preparation of optical recording medium>
An optical recording medium was prepared using the obtained compound (A-1). No whitening phenomenon derived from crystallization of the compound was observed in the coating film. The obtained optical recording medium was subjected to measurement of the highest recording sensitivity and a light resistance test. The results are shown in Table-1.

[Example 2]
<Synthesis of Compound (A-2)>
In Example 1, the yellow crystal (0.27g) of the compound (A-2) was obtained by the same method except having changed the metal salt dripped into anhydrous copper chloride 0.35g.
The obtained compound was analyzed by proton NMR, DEI-MS analysis and thermal analysis. The results are shown below.
λmax: 428 nm
ε at λmax: 24,000
Thermal decomposition temperature: 390 ° C
DEI-MS analysis: measured value 772 (M +), calculated value 772

<Preparation of optical recording medium>
An optical recording medium was prepared using the obtained compound (A-2). No whitening phenomenon derived from crystallization of the compound was observed in the coating film. The obtained optical recording medium was subjected to measurement of the highest recording sensitivity and a light resistance test. The results are shown in Table-1.

[Example 3]
<Synthesis of Compound (A-3)>
1.0 g of 3,5-di-tert-butylsalicylaldehyde and 0.50 g of 2-aminophenol were heated and stirred in 10 ml of ethanol under reflux conditions for 1 hour. To the resulting solution, 0.6 ml of tetraisopropyl orthotitanate was added dropwise to produce a precipitate. The resulting precipitate was filtered off and purified by silica gel column chromatography to obtain a red crystal (0.85 g) of compound (A-3).

The obtained compound was analyzed by proton NMR, DEI-MS analysis and thermal analysis. The results are shown below.
λmax: 330 nm
ε at λmax: 37,000
Thermal decomposition temperature: 370 ° C
DEI-MS: measured value 694 (M +), calculated value 694

<Preparation of optical recording medium>
An optical recording medium was prepared using the obtained compound (A-3). No whitening phenomenon derived from crystallization of the compound was observed in the coating film. The obtained optical recording medium was subjected to measurement of the highest recording sensitivity and a light resistance test. The results are shown in Table-1.

[Example 4]
<Synthesis of Exemplary Compound (A-4)>
0.50 g of 3,5-di-tert-butylsalicylaldehyde and 0.30 g of anthranilic acid were heated and stirred for 2 hours in 10 ml of ethanol under reflux conditions. To the obtained solution, 0.4 ml of tetraisopropyl orthotitanate was added dropwise, the solvent was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography to obtain orange crystals (0.12 g) of compound (A-4). )

The obtained compound was analyzed by proton NMR and DEI-MS analysis. The results are shown below.
λmax: 333 nm
DEI-MS analysis: measured value 750 (M +), calculated value 750

[Comparative Example 1]
The following compound (4) described in JP-T-2005-509694 was obtained by heating and mixing orthophenylenediamine (1 equivalent), salicylaldehyde (2 equivalents) and copper (II) acetate (1 equivalent) in ethanol. .
An optical recording medium was prepared using the obtained compound (4). No whitening phenomenon due to crystallization of the compound was observed in the coating film. The obtained optical recording medium was subjected to measurement of the highest recording sensitivity and a light resistance test. The results are shown in Table-1.

Claims (5)

It consists of a Schiff base metal complex which comprises a divalent anion Schiff base represented by the following general formula (1) and a transition metal cation and may contain other anions and cations. A dye for forming a recording layer of an optical recording medium.

(In the formula, R ¹ and R ² each independently represent a group having a monovalent anion of a group 15 or group 16 atom, and X ¹ and X ² each independently have a substituent. Represents an aromatic ring or a non-aromatic hydrocarbon group, and at least one of X ^{1 and} X ² is an aromatic ring which may have a substituent, and X ³ is a hydrogen atom or a monovalent group. Represents a group of The recording layer forming dye according to claim 1, wherein the divalent anion Schiff base is represented by the following general formula (2).

(In the formula, ring A and ring B each independently represent an aromatic ring which may have a substituent, but at least one of ring A and ring B may have a substituent. R ¹ and R ² each independently represent a group having a monovalent anion of a group 15 or group 16 atom, R ¹ is in the o-position of ring A, and R ² is the o-position of ring B. X ³ represents a hydrogen atom or a monovalent group.) Temperature 50 ° C., 55% humidity, according to claim 1 or 2 dye residual ratio when performing the light resistance test for 40 hours under conditions of xenon light intensity 0.55 W / m ² is equal to or less than 90% The recording layer forming dye described in 1.   An optical recording medium, wherein at least a recording layer is provided on a substrate, and the recording layer contains the recording layer forming dye according to any one of claims 1 to 3. A recording method for an optical recording medium, wherein information is recorded by irradiating the optical recording medium according to claim 4 with a laser beam having a wavelength of 350 to 530 nm.