JP4483802B2 - Dye for recording layer formation of optical recording medium, optical recording medium using the same, and recording method of optical recording medium - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a dye for forming a recording layer of an optical recording medium, an optical recording medium using the same, and a recording method of the optical recording medium, and in particular, a recording layer formation suitably used for an optical recording medium compatible with blue laser light. The present invention relates to a dye for use, an optical recording medium using the same, and a recording method of the optical recording medium.

  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 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 reflection 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 the recording layer, the reflective layer, or the substrate of the laser beam irradiated portion is decomposed, evaporated, dissolved, etc. It is carried out by a method of causing thermal 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. Generally, a laser beam absorbing dye is used for the recording layer, and an organic dye is used as the laser beam absorbing dye. Since an optical recording medium can form a recording layer by a simple method of applying an organic dye solution, it 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 is 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. Furthermore, in recent years, in order to increase the capacity of recording media, investigations are being made on double-layer recording media in which the recording capacity is doubled by producing two recording layers on the recording medium, and speeding up of recording. Increasingly high sensitivity to recording lasers is required for dye compounds for recording layer formation.

  On the other hand, when a dye is used for the recording layer, it is generally advantageous to apply it to the substrate using a spin coating method in terms of cost compared to the vacuum evaporation method. It is essential to show high solubility in the solvent. At present, it is applied to a polycarbonate substrate using a fluorine-based alcohol solvent such as 2,2,3,3-tetrafluoropropanol or 2,2,3,3,4,4,5,5-octafluoropentanol. Is common. In general, both data recording and reading are performed by laser light. In this case, the reading laser intensity is weaker than the recording laser intensity. Therefore, if the light resistance is so low that the recording layer forming dye of the optical recording medium is decomposed by irradiation with weak laser light as readout light, it may cause a data error when recording data is read out. Furthermore, because of the nature of optical recording media, the recording surface is often exposed to sunlight, illumination, etc. for a long time, so if the dye is inferior in light resistance, it becomes difficult to store the recording data of the optical recording medium for a long time .

  In order to satisfy these requirements, as a recording layer forming dye of an optical recording medium, conventionally, a Schiff base and a complex of its derivative have a simple synthesis and a maximum absorption mainly in the vicinity of 300 to 500 nm. Application to an optical recording medium compatible with blue laser light is expected, and for example, proposals in Patent Documents 1 to 4 have been made. However, since these compounds have a rigid structure, they are generally inferior in solubility in a coating solvent, and as a result of comparative studies by the present inventors, it has been found that they are also inferior in light resistance.

On the other hand, hydrazide compounds having a skeleton [C (= O) -NH-N = C skeleton] having an amide group adjacent to the imine site of the Schiff base are generally expected to have unstable NN single bonds. In addition, since it has an amide bond unit, a decrease in solubility is expected, and application to an optical recording medium has been considered impossible.
JP 2003-266939 A JP 2005-509694 A JP 2005-515914 A International Publication No. 2004-102551

  The present invention has been made in view of the above-described conventional circumstances, and has excellent solubility in a coating solvent and light resistance, and can be used for optical recording using blue laser light. It is an object of the present invention to provide a dye for forming, an optical recording medium using the same, and a recording method for the optical recording medium.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a complex of a hydrazide compound represented by the following general formula (I) is excellent in solubility in a coating solvent, and is not a complex with a specific metal. The present inventors have found that the optical recording medium using the recording layer is excellent in light resistance and can be satisfactorily recorded with blue laser light, thereby completing the present invention. That is, a recording layer forming dye of an optical recording medium containing a complex of a hydrazide compound ligand represented by the following general formula (I) and a transition metal cation, a substrate, and a recording layer formed on the substrate An optical recording medium in which the recording layer is formed of the recording layer forming dye, and an optical recording medium for recording on the optical recording medium using a laser beam having a wavelength of 350 to 530 nm This recording method is summarized as follows.

[In Formula (I), Ring A represents a hydrocarbon group that may have a substituent, or a heterocyclic group that may have a substituent, and R ¹ has a substituent. A hydrocarbon group that may be substituted, a heterocyclic group that may have a substituent, or a hydrogen atom; the pyridine ring may be a condensed ring. ]

  The present invention relates to a dye for forming a recording layer of an optical recording medium that is excellent in solubility in a coating solvent and light resistance, and can be used for optical recording using blue laser light, and an optical recording medium using the same, An optical recording medium recording method can be provided.

  Hereinafter, the present invention will be specifically described, 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.

  The recording layer forming dye of the optical recording medium of the present invention must contain a complex composed of a ligand of a hydrazide compound represented by the following general formula (1) and a transition metal cation.

[In Formula (I), Ring A represents a hydrocarbon group that may have a substituent, or a heterocyclic group that may have a substituent, and R ¹ has a substituent. A hydrocarbon group that may be substituted, a heterocyclic group that may have a substituent, or a hydrogen atom; the pyridine ring may be a condensed ring. ]

  In the present invention, examples of the hydrocarbon group of the ring A in the general formula (I) include aryl groups such as a phenyl group, a naphthyl group, an anthranyl group, a fluorenyl group, a phenanthryl group, an azulenyl group, and a metallocene ring group. Of these, a monocyclic or condensed bicyclic aryl group having about 6 to 12 carbon atoms is preferable. Of these, a monocyclic aryl group is particularly preferable. Examples of the heterocyclic group include thienyl group, furyl group, pyrrolyl group, pyridyl group, imidazolyl group, pyrazolyl group, indoleyl group, quinoxalinyl group, acridinyl group, thiazolyl group, and pyrazinyl group. Among these, a monocyclic 5-membered ring or 6-membered ring having about 3 to 12 carbon atoms, or a bicyclic 5-membered heterocyclic group is preferable. Particularly preferred is a monocyclic 6-membered heterocyclic group having about 3 to 12 carbon atoms.

Examples of the hydrocarbon group represented by R ^{1 in} the general formula (I) include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-butyl group, and a 2-methylbutyl group. Group, 2-ethylbutyl group, 3-methylbutyl group, neopentyl group, 3-pentyl group, cyclohexylmethyl group, cyclohexyl group and the like linear, branched or cyclic alkyl group, ethynyl group, 2-propenyl group, Examples thereof include alkenyl groups such as 2-butenyl group, 3-butenyl group and 2,4-pentadienyl group, and aliphatic hydrocarbon groups such as alkynyl group such as 2-hexyne group. An aliphatic hydrocarbon group having a certain degree, particularly preferably a branched chain aliphatic hydrocarbon group having about 3 to 12 carbon atoms. Further, examples of the hydrocarbon group for R ¹ include the same aryl groups as mentioned for the ring A hydrocarbon group. In addition, examples of the heterocyclic group represented by R ^{1 in} the general formula (I) include the same heterocyclic groups as mentioned for the heterocyclic group of the ring A.

The hydrocarbon group and heterocyclic group of ring A, and the substituent of the hydrocarbon group and heterocyclic group of R ¹ are not particularly limited as long as they do not affect the stability and performance of the dye. Although not, for example, halogen atom, hydroxyl group, nitro group, cyano group, alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, alkoxy group, aryloxy group, heteroaryloxy group, alkylthio group, arylthio group, Heteroarylthio group, amino group, acyl group, aminoacyl group, ureido group, sulfonamido group, carbamoyl group, sulfamoyl group, sulfamoylamino group, alkoxycarbonyl group, aryloxycarbonyl group, heteroaryloxycarbonyl group, alkylsulfonyl Group, arylsulfonyl group, heteroarylsulfo Group, selected from the group consisting of an imide group and a silyl group. These substituents may be further substituted with an arbitrary substituent. Specific examples of the optional substituents mentioned above are also given as the substituent in that case. In addition, the adjacent substituents may be bonded via a linking group or not to form a ring structure.

  Specifically, those substituents have about 1 to 6 carbon atoms such as a methyl group, an ethyl group, an i-propyl group, an n-butyl group, a t-butyl group, a 2-pentyl group, and an n-hexyl group. Alkenyl groups having about 2 to 6 carbon atoms such as alkyl groups, ethynyl groups, and propylenyl groups, alkynyl groups having about 2 to 6 carbon atoms such as acetylenyl groups, phenyl groups, naphthyl groups, anthranyl groups, phenanthryl groups, ferrocene ring groups, etc. An aryl group having about 6 to 20 carbon atoms, a thienyl group, a furyl group, a pyridyl group, an imidazolyl group, a pyrazolyl group and the like, a heteroaryl group having about 3 to 20 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, and t-butoxy Group, an alkoxy group having about 1 to 6 carbon atoms such as n-butoxy group, an aryloxy group having about 6 to 20 carbon atoms such as phenoxy group and naphthoxy group, and thienyl C1-C20 heteroaryloxy group such as xyl group, pyridyloxy group, methylthio group, ethylthio group, isopropylthio group, n-butylthio group, s-butylthio group, 3-pentylthio group, etc. A heteroarylthio group having about 3 to 20 carbon atoms such as an arylthio group having about 6 to 20 carbon atoms such as about 6 alkylthio groups, a phenylthio group, a naphthylthio group, a thienylthio group, a pyridylthio group, an imidazolylthio group, and a pyrazolylthio group; An acyl group having about 2 to 20 carbon atoms such as dimethylamino group, diethylamino group, diphenylamino group and the like, which may have a substituent having about 1 to 20 carbon atoms, acetyl group, pivaloyl group, acetylamino Group, acylamino group having about 2 to 20 carbon atoms such as propionylamino group, 3-methylureido group Carbamoyl having about 1 to 20 carbon atoms such as ureido group having about 2 to 20 carbon atoms, sulfonamido group having about 1 to 20 carbon atoms such as methanesulfonamide group and benzenesulfonamide group, dimethylcarbamoyl group and ethylcarbamoyl group , Sulfamoyl groups having about 1 to 20 carbon atoms such as ethylsulfamoyl groups, sulfamoylamide groups having about 1 to 20 carbon atoms such as dimethylsulfamoylamide groups, methoxycarbonyl groups, ethoxycarbonyl groups, etc. A heteroaryloxycarbonyl group having about 5 to 20 carbon atoms such as an aryloxycarbonyl group having about 7 to 20 carbon atoms such as an alkoxycarbonyl group having about 2 to 6 carbon atoms, a phenoxycarbonyl group, and a naphthoxycarbonyl group, and a pyridylcarbonyl group; Methanesulfonyl group, ethanesulfonyl group, trifluoro An alkylsulfonyl group having about 1 to 6 carbon atoms such as a methanesulfonyl group, an arylsulfonyl group having about 6 to 20 carbon atoms such as a benzenesulfonyl group and a monofluorobenzenesulfonyl group, and an about 3 to 20 carbon atoms such as a thienylsulfonyl group Examples thereof include an imide group having about 4 to 20 carbon atoms such as a heteroarylsulfonyl group and a phthalimide group, or a silyl group trisubstituted with a substituent selected from an alkyl group and an aryl group.

  Specific examples of the hydrazide compound represented by the general formula (I) are shown below.

  The hydrazide compound represented by the general formula (1) is usually preferably insoluble in water from the viewpoint of improving the storage stability of the optical recording medium. Here, “water-insoluble” means that the solubility in water at 25 ° C. and 1 atmosphere is usually 0.01% by weight or less, preferably 0.001% by weight or less.

  The hydrazide compound represented by the general formula (I) in the present invention can be easily synthesized by, for example, the following method.

  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 methanol 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.

  The recording layer forming dye of the optical recording medium of the present invention contains a complex composed of a ligand of the hydrazide compound represented by the general formula (I) and a transition metal cation, and the transition metal includes the hydrazide compound. As long as it can form a complex with a ligand as a ligand, specific examples include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru, Rh, Pd, Ag, Pt, Au, Er, etc. are mentioned. In the present invention, among these, the fourth periodic element is preferable, and Mn, Fe, Co, Ni, and Cu are more preferable, and Co is particularly preferable. Further, the valence of the transition metal cation is not particularly limited, but it is particularly preferably divalent or trivalent from the stability of the complex.

  In the present invention, the complex consisting of the ligand of the hydrazide compound represented by the general formula (I) and the transition metal cation is not particularly limited as long as it is neutral, but the hydrazide compound ligand of the transition metal cation 1 is not limited. It is preferable that the number of components is 1 to 2, and the number of components of the anion is the valence of the transition metal cation. Particularly preferred complexes are those represented by the following general formula (II).

[In the formula (II), the ring A, R ¹ and the pyridine ring are the same as those in the formula (I), and the plurality of rings A and the plurality of R ¹ may be the same or different. , M represents a transition metal, and the complex of the formula (II) may further have a counter anion. ]

In formula (II), ring A, and R ^1, ring A in Formula (I), and is R ^1, a plurality of ring A, and a plurality of R ¹ may be the same or different However, they are preferably the same from the viewpoint of synthesis. Here, as the hydrazide compound of the general formula (I), one kind may be contained alone, or two or more kinds may be mixed and contained. Further, the molecular weights of R ¹ and R ² are preferably 300 or less in total from the viewpoint of preventing a decrease in extinction coefficient accompanying an increase in molecular weight.

In addition, the complex in the present invention may further have a counter anion. In that case, the composition ratio of the hydrazide compound, the transition metal cation and the counter anion is preferably 2: 1: 1. The counter anion preferably has 20 or less carbon atoms. Specific examples thereof include alcohol, phenol, carboxylic acid, phosphonic acid, halogen, perchloric acid, periodic acid, cyanic acid, isocyanic acid and isothiocyanic acid. , Azide, nitric acid, carbonic acid, hydrogencarbonate, substituted or unsubstituted sulfuric acid (sulfuric acid, hydrogensulfuric acid, methylsulfuric acid, etc.), methanesulfonic acid, trifluoromethanesulfonic acid, tosylic acid, substituted or unsubstituted phosphoric acid (phosphorus) Acid, hydrogen phosphate, dihydrogen phosphate, phenyl phosphate, etc.), phosphorus hexafluoride, antimony hexafluoride, substituted or unsubstituted phosphinic acid (phosphinic acid, methylphosphinic acid, etc.), substituted or unsubstituted Boronic acid (tetraphenylboronic acid, etc.), anionized benzenesulfonic acid, acetic acid, trifluoroacetic acid, etc. It is below. Among these, those having a molecular weight of 300 or less are preferable from the viewpoint of preventing a decrease in recording sensitivity due to a decrease in absorbance, and ClO ₄ ⁻ , PF ₆ ⁻ , BF ₄ ⁻ , NO ₃ ⁻ , SbF ₆ ⁻ are used in order to make them insoluble in water. It is particularly preferable that a trifluoromethanesulfonate anion or the like is included.

When any of the constituent numbers of the hydrazide compound ligand, the transition metal cation, and the counter anion is 2 or more, the hydrazide compound ligand, the transition metal cation, and the counter anion may be the same or different. For example, when two transition metal cations are contained in one molecule of the complex, the transition metal cations may be Cr ³⁺ and Cu ²⁺ .

  The complex in the present invention preferably has a molecular weight of 2,500 or less, including transition metal cations and counter anions, particularly preferably 2,000 or less, from the viewpoint of preventing sensitivity from being reduced due to a decrease in absorbance.

  The complex in the present invention can be obtained by reacting the hydrazide compound and the transition metal salt in the presence or absence of a solvent at a temperature at which the solvent is refluxed. When a reaction solvent is used, a polar solvent such as water, methanol, acetonitrile, or tetrahydrofuran, or a nonpolar solvent such as chloroform, toluene, or xylene can be used as the solvent. In addition, the counter anion contained in the produced | generated complex can be changed by adding another salt in a solvent.

The complex in the present invention is characterized by excellent solubility in a coating solvent and light resistance, and excellent film properties and recording sensitivity when used as a recording layer forming dye of an optical recording medium. The solubility in the coating solvent is preferably 1.0% by weight or more in 2,2,3,3-tetrafluoropropanol at 20 ° C. and normal pressure, and the light resistance is A layer formed to a thickness of 50 nm on a substrate has a dye residual ratio of 80% or more after being irradiated with a xenon lamp for 40 hours at an irradiation intensity of 0.55 W / m ² under conditions of a temperature of 50 ° C. and a relative humidity of 50. Is preferred.

  The recording layer of the optical recording medium of the present invention is formed using a dye containing at least one complex composed of a ligand of the hydrazide compound represented by the general formula (I) and the transition metal cation. Here, as the dye used for forming the recording layer of the optical recording medium of the present invention, only one type of the complex of the present invention may be used, or two or more types may be used in any combination and ratio. . Furthermore, in addition to the 1 type, or 2 or more types of complex of this invention, the other pigment | dye may be used together 1 type, or 2 or more types. However, when a dye other than the complex of the present invention is used in combination, the ratio of the complex of the present invention to the total of all the dyes is usually 50% by weight from the viewpoint of sufficiently exhibiting the excellent characteristics of the complex of the present invention. Above, preferably 70% by weight or more.

  Other dyes that can be used in combination with the complex of the present invention have absorption in the laser light wavelength region for recording, absorb the energy of the irradiated laser light, and irradiate the recording layer, reflective layer or substrate of the irradiated portion. Those that can form pits accompanied by thermal deformation such as decomposition, evaporation, and dissolution are preferred. 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. Of these, 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. A suitable dye can be used in combination to provide an optical recording material that supports recording with laser light in a plurality of wavelength regions.

  The recording layer may further contain binders and various additives which will be described later, but the proportion of the dye in the recording layer is usually 10% by weight or more, preferably 50% by weight or more, particularly preferably 90% by weight. % Or more. When the proportion of the dye is too small, the recording sensitivity tends to be remarkably lowered.

  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, polycarbonate and the like can be used alone or in admixture of two or more.

  The recording layer may contain a singlet oxygen quencher, a recording sensitivity improver, etc. for improving stability and light resistance. Examples of the singlet oxygen quencher include acetylacetonate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone and the like and a transition metal chelate compound, and these may be used alone. Two or more kinds may be used in combination. The recording sensitivity improver is preferably a metal compound in which a metal such as a transition metal is included in the compound in the form of atoms, ions, clusters, etc., specifically, for example, an ethylenediamine complex, an azomethine complex, Organometallic compounds such as phenylhydroxyamine complex, phenanthroline complex, dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex, etc. These may be used alone or in combination of two or more. 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.

  In order to form a recording layer of an optical recording medium using the complex of the present invention, generally used thin film forming methods such as a vacuum deposition method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method are used. Used to form a layer on the substrate. Of these, spin coating is preferred from the standpoints of mass productivity and cost. When the recording layer is formed by the spin coating method, the rotation speed is preferably 500 to 5000 rpm, and after spin coating, a treatment such as heating or exposure to solvent vapor may be performed as necessary. The film 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. By setting the film thickness within this range, the influence of thermal diffusion can be suppressed, good recording can be easily performed, and the signal amplitude can be easily increased because distortion is hardly generated in the recording signal. Furthermore, 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 of the present invention and other dyes, a binder, a singlet oxygen quencher, a recording A sensitivity improving agent or the like is dissolved in a solvent to prepare a coating solution. As the solvent at that time, it is particularly preferable in terms of industrial use to use 2,2,3,3-tetrafluoropropanol, but other solvents such as diacetone alcohol, 3-hydroxy, and the like can be used as long as they do not attack the substrate. Ketone alcohol solvents such as -3-methyl-2-butanone, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, chain hydrocarbon solvents such as n-hexane and n-octane, cyclohexane, methylcyclohexane, ethylcyclohexane, Alicyclic hydrocarbon solvents such as dimethylcyclohexane, n-butylcyclohexane, t-butylcyclohexane and cyclooctane, ether solvents such as diisopropyl ether and dibutyl ether, 2,2,3,3,4,4,5, 5-octafluoropentanol, hexafluorobutanol, etc. Perfluoroalkyl alcohol solvents, methyl lactate, ethyl lactate, alone one such as hydroxyethyl ester solvents such as methyl isobutyrate, or may be a mixture of two or more.

  The concentration of the recording layer forming dye in the coating solution is appropriately determined according to the solubility of the solvent. Preferably it is 3.0 weight% or less. If the dye concentration in the coating solution is too low, the formation efficiency of the recording layer tends to deteriorate. On the other hand, if the dye concentration in the coating solution is too high, problems such as dye crystallization occur in the film formation process. Tend to. In order to efficiently recover the excess dye after spin coating, the dye 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. Preferably there is.

  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 on a substrate. Examples of the substrate include glass and various plastics. Those that are transparent to the laser beam used are 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.

  On the substrate, if necessary, layers other than the recording layer such as a reflective layer, a protective layer and an undercoat layer are further provided to form 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. For example, an organic substance such as a thermoplastic resin, a thermosetting resin, an electron beam curable resin, for example, an ultraviolet curable resin such as urethane acrylate, epoxy acrylate, or polyester acrylate, and SiO ₂ , SiN ₄ , MgF ₂ , SnO ₂ Inorganic substances such as 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 is preferably an organic layer from the viewpoint of ease of handling. In addition, two optical recording media having the above-described 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.

  The complex in the present invention is excellent in film properties. Therefore, in forming the recording layer containing the complex in the present invention, the whitening phenomenon derived from the crystallization of the compound is recognized on the surface of the recording layer formed by the spin coat method. I can't.

  The preferable absorption wavelength and absorbance of the optical recording medium depend on the type of laser light used for recording. For example, as described later, 405 is suitable for an optical recording medium containing the complex of the present invention in a recording layer. For blue laser light having a central wavelength of ˜410 nm, the maximum absorption wavelength (λmax) of the absorption spectrum of the optical recording medium is preferably 350 to 450 nm, and the molar extinction coefficient (ε) at λmax is 5000 or more. Further, it is preferably 10,000 or more, particularly preferably 30,000 or more.

  The optical recording medium containing the complex in the present invention in the recording layer is excellent in recording laser sensitivity. Specifically, when the optical recording medium is irradiated with blue laser light having a center wavelength of 404 nm and NA = 0.85, good recording pits can be formed even with a laser intensity of 10 mW or less.

Further, the optical recording medium containing the complex in the present invention in the recording layer is hardly deteriorated even if it is left under high temperature and high humidity and direct light. Specifically, the recording layer has a dye residual ratio of 80% after the optical recording medium is irradiated with a xenon lamp for 40 hours at an irradiation intensity of 0.55 W / m ² at a temperature of 50 ° C. and a relative humidity of 50. More preferably, it is 90% or more, particularly 95% or more.

  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 better. In particular, the optical recording medium of the present invention contains the above-described complex of the present invention in its recording layer, so that its advantages are obtained. From the viewpoint of sufficiently exerting, a laser beam having a wavelength of 350 nm to 530 nm is preferable. Typical examples of such laser light include blue laser light with center wavelengths of 405 nm and 410 nm, blue-green high-power semiconductor laser light with center wavelength of 515 nm, and the like. 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 ), compound semiconductors and the like are preferable. Specific examples of the second harmonic, when the basic oscillation wavelength of the semiconductor laser of 860 nm, the wavelength 430nm of the frequency doubled, also in the case of solid-state laser of the semiconductor laser excitation, LiSrAlF ₆ crystal (fundamental oscillation that Cr-doped And a wavelength of 430 nm of a double wave from a wavelength of 860 nm. Among these, it is particularly preferable to use blue laser light having a center wavelength of 405 nm.

  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 nuclear magnetic resonance spectrometer “AV400M” (400 MHz) manufactured by Bruker. In addition, TG analysis uses differential thermal thermogravimetric analyzer “EXSTAR6000 TG-DTA” manufactured by SII Nano Technology, sample amount 1.0 mg, temperature rise 10 ° C./min, nitrogen flow rate 0.2 L / min, aluminum Under the conditions of bread, the thermal decomposition temperature was a temperature at which the compound weight decreased by 10% under the above TG conditions.

Example 1
<Synthesis of hydrazide compound>
2.73 g of 4-methoxybenzhydrazide (manufactured by Avocado) and 1.76 g of 2-pyridinecarbaldehyde (manufactured by Wako Pure Chemical Industries, Ltd.) were refluxed with heating in 50 ml of methanol for 1 hour, and the methanol was distilled off from the reaction mixture. Crystallization was performed, and the produced solid was separated by filtration to obtain 3.0 g of the following hydrazide compound as a milky white powder (yield 72%).

<Synthesis of complex>
0.26 g of the hydrazide compound obtained above was dissolved in 10 ml of methanol, 0.11 g of triethylamine was added, 5 ml of a methanol solution of 0.12 g of cobalt (II) acetate tetrahydrate was further added, and heated under reflux for 1 hour. after, the resulting precipitate was filtered off, washed with methanol 10 ml, was filtered and dried, complexes of yellow-brown powder of Co ²⁺ and transition metal cations. 2 g was obtained (73% yield). An ultraviolet-visible absorption spectrum of the obtained complex in an acetonitrile solution is shown in FIG.
λmax (CH ₃ CN) = 376 nm (ε = 49000), weight loss starting temperature = 313 ° C.

The resulting complex was tested for solubility in the coating solvent by the following method, and as a result, it was confirmed that the complex was completely dissolved at concentrations of 1.0% by weight and 1.5% by weight. .
<Solubility test>
After 2,2,3,3-tetrafluoropropanol is used as a coating solvent, and the concentration of the complex is 1.0% by weight and 1.5% by weight, followed by ultrasonic treatment at 20 ° C. and normal pressure for 30 minutes. The solution was dropped on a filter paper (quantitative filter paper “No. 5C” manufactured by Toyo Roshi Kaisha Co., Ltd.), dried at room temperature for 24 hours, and visually observed whether crystal residues of undissolved components were present on the filter paper.

  Furthermore, after the obtained complex was dissolved in 2,2,3,3-tetrafluoropropanol at a concentration of 1.0% by weight and fine dust was removed by filtration, the resulting solution was obtained with a diameter of 120 mm and a thickness of It was dropped on a 1.2 mm injection-molded polycarbonate substrate, applied by spin coating (4900 rpm), and dried at 80 ° C. for 30 minutes to form a recording layer having a thickness of about 50 nm, thereby producing an optical recording medium.

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 5.0 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 91%.
<Light resistance test>
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 50 ° C. and a relative humidity of 50 was determined from the absorbance before and after irradiation at the absorption maximum wavelength.

Example 2
<Synthesis of hydrazide compound>
3.6 g of 4-dimethylaminobenzhydrazide (manufactured by Avocado) and 2.1 g of 2-pyridinecarbaldehyde (manufactured by Wako Pure Chemical Industries, Ltd.) are refluxed by heating in 50 ml of methanol for 1 hour, and the reaction mixture is allowed to cool to room temperature and deposited. The obtained solid was filtered off to obtain 4.2 g of the following hydrazide compound as a milky white powder (yield 78%).

<Synthesis of complex>
0.27 g of the hydrazide compound obtained above was dissolved in 20 ml of methanol, 0.11 g of triethylamine was added, 5 ml of a methanol solution of 0.12 g of cobalt acetate (II) tetrahydrate was further added, and heated under reflux for 1 hour. Then, the produced precipitate was filtered off, washed with 10 ml of methanol, and then filtered and dried to obtain 0.15 g of a brown powder complex having Co ²⁺ as a transition metal cation (yield 50%). An ultraviolet-visible absorption spectrum of the obtained complex in an acetonitrile solution is shown in FIG.
λmax (CH ₃ CN) = 408 nm (ε = 61000), weight loss starting temperature = 316 ° C.

  The resulting complex was tested for solubility in the coating solvent by the method described above, and as a result, it was confirmed that the complex was completely dissolved at both concentrations of 1.0% by weight and 1.5% by weight. . Furthermore, when an optical recording medium was produced in the same manner as in Example 1, and the recording sensitivity of the obtained optical recording medium was tested by the method described above, the maximum recording sensitivity at which formation of recording pits was confirmed was 5 0.0 mW. Further, when the obtained optical recording medium was tested for light resistance by the method described above, the residual ratio of the dye was 93%.

Comparative Example 1
Using the following Schiff base compound complex having an ultraviolet-visible absorption spectrum in a chloroform solution shown in FIG. 3, 1.0% by weight of the complex was dissolved in methylene chloride, and fine dust was removed by filtration. The obtained solution was dropped onto a “ZEONEX” substrate manufactured by Nippon Zeon Co., Ltd. having a diameter of 120 mm and a thickness of 1.2 mm, applied by spin coating (4900 rpm), and dried at 80 ° C. for 30 minutes to obtain a film thickness of about 50 nm. The recording layer was formed to produce an optical recording medium.

  Regarding the solubility of the Schiff base compound complex used in the coating solvent by the above-described method, the presence of insoluble components was confirmed at both concentrations of 1.0% by weight and 1.5% by weight. Furthermore, when the recording sensitivity of the obtained optical recording medium was tested by the method described above, the maximum recording sensitivity at which formation of recording pits was confirmed was 15.0 mW. Further, when the obtained optical recording medium was tested for light resistance by the method described above, the dye residual ratio was 86%.

It is a figure which shows the ultraviolet visible absorption spectrum in the acetonitrile solution of the complex of Example 1. It is a figure which shows the ultraviolet visible absorption spectrum in the acetonitrile solution of the complex of Example 2. It is a figure which shows the ultraviolet visible absorption spectrum in the chloroform solution of the complex of the comparative example 1.

Claims (8)

A dye for forming a recording layer of an optical recording medium, comprising a complex comprising a ligand of a hydrazide compound represented by the following general formula (I) and a transition metal cation.

[In Formula (I), Ring A represents a hydrocarbon group that may have a substituent, or a heterocyclic group that may have a substituent, and R ¹ has a substituent. A hydrocarbon group that may be substituted, a heterocyclic group that may have a substituent, or a hydrogen atom; the pyridine ring may be a condensed ring. ] The dye for forming a recording layer of an optical recording medium according to claim 1, wherein the complex is represented by the following general formula (II).

[In the formula (II), the ring A, R ¹ and the pyridine ring are the same as those in the formula (I), and the plurality of rings A and the plurality of R ¹ may be the same or different. , M represents a transition metal, and the complex of the formula (II) may further have a counter anion. ]   The dye for forming a recording layer of an optical recording medium according to claim 1 or 2, wherein the transition metal cation comprises an element of the fourth period.   The dye for forming a recording layer of an optical recording medium according to any one of claims 1 to 3, wherein the transition metal is cobalt.   The recording layer formation of an optical recording medium according to any one of claims 1 to 4, wherein the solubility in 2,2,3,3-tetrafluoropropanol is 1.0% by weight or more at 20 ° C and normal pressure. Dye for use. A layer formed to a thickness of 50 nm on a substrate has a dye residual ratio of 80% after being irradiated with a xenon lamp for 40 hours at an irradiation intensity of 0.55 W / m ² under conditions of a temperature of 50 ° C. and a relative humidity of 50%. The dye for forming a recording layer of an optical recording medium according to any one of claims 1 to 5, which is as described above.   It has at least a substrate and a recording layer formed on the substrate, and the recording layer is formed by the recording layer forming dye of the optical recording medium according to any one of claims 1 to 6. An optical recording medium characterized by the above.   8. A method for recording an optical recording medium, wherein the optical recording medium according to claim 7 is recorded using a laser beam having a wavelength of 350 to 530 nm.

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