JP4120340B2 - Optical recording medium and optical recording method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a write-once optical recording medium and an optical recording method using an organic dye in a recording layer, and more particularly to a write-once optical recording medium compatible with a blue laser.
[0002]
[Prior art]
In recent years, semiconductor lasers having a short oscillation wavelength have been developed, and an optical recording medium capable of high-density recording / reproduction using laser light having wavelengths shorter than 780 nm and 830 nm of conventionally used lasers has been demanded. . Conventionally proposed optical recording media include magneto-optical recording media, phase change recording media, chalcogen oxide optical recording media, organic dye-based optical recording media, etc. Among these, organic dye-based optical recording media are It is considered to be superior in that it is relatively inexpensive and can be easily manufactured.
[0003]
At present, as an organic dye-based optical recording medium, a CD-R of a type in which a highly reflective metal layer is laminated on an organic dye layer is mass-produced and widely known. A high-density organic dye-based optical recording medium (DVD-R) having a shorter wavelength than that of the laser used and recording / reproducing with a red semiconductor laser has been developed and put into practical use.
[0004]
However, as laser oscillation with a shorter wavelength such as a blue semiconductor laser becomes practical, the need for an optical recording medium capable of recording / reproducing using the laser oscillation is increasing.
[0005]
[Patent Document 1]
JP 2001-158862 A
[Patent Document 2]
JP 2001-181524 A
[0006]
[Problems to be solved by the invention]
In general, an optical recording medium used as a CD-R or a DVD-R has a problem that recording and reproduction with a so-called blue semiconductor laser have a low reflectance and cannot be recorded or reproduced.
An object of the present invention is to provide an organic dye-based optical recording medium that can be recorded and reproduced by a blue semiconductor laser.
[0007]
[Means for Solving the Problems]
As a result of various investigations on blue semiconductor lasers, in particular, organic dyes having a wavelength of 420 nm or less, which are highly sensitive to blue laser light having a relatively short wavelength, two aromatic rings are bonded with an ethylene group or a carbonyl group. The present inventors have found that the compound having a specific structure can be used for the recording layer of the optical recording medium corresponding to the blue semiconductor laser, and have reached the present invention.
[0008]
That is, the gist of the present invention is that, in an optical recording medium provided with a recording layer capable of recording or reproducing information by a laser on a substrate, the recording layer has an absorption maximum at a wavelength of 420 nm or less and has the following general formula:(5)It contains in the optical recording medium characterized by containing the compound shown by these. The wavelength of the laser is preferably 350 nm to 530 nm. More preferably, it is 350 nm-430 nm.
[0009]
[Chemical 8]
[0010]
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R₁Or R_FourEach independently represents a hydrogen atom or an optionally substituted alkyl group.
  Also R₁Or R_FourTwo or more selected from the above may combine to form a ring, R₁Or R_FourEach independently may be bonded to an atom constituting ring A or ring B to form a ring condensed with the ring.n represents 1 or 2, and m = 0. )
Another gist of the present invention is an optical recording medium in which a recording layer capable of recording or reproducing information by a laser is provided on a substrate, the recording layer having an absorption maximum at a wavelength of 420 nm or less and It exists in the optical recording medium characterized by containing the compound shown by General formula (2). The wavelength of the laser is preferably 350 nm to 530 nm. More preferably, it is 350 nm-430 nm.
[Chemical 9]
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R _Three ', R _Four ′ And R _Four ″ Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A1 represents an optionally substituted hydrocarbon ring or heterocyclic ring. L represents 0 or 1;)
Another gist of the present invention is that, in an optical recording medium provided with a recording layer capable of recording or reproducing information by a laser on a substrate, the recording layer has an absorption maximum at a wavelength of 420 nm or less and It exists in the optical recording medium characterized by containing the compound shown by General formula (4). The wavelength of the laser is preferably 350 nm to 530 nm. More preferably, it is 350 nm-430 nm.
[Chemical Formula 10]
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R ₁ , R _Three And R _Four Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A3 represents an optionally substituted hydrocarbon ring or heterocyclic ring. j represents 0 or 1; )
Another gist of the present invention is that a laser beam having a wavelength of 350 to 530 nm is used and a recording layer capable of recording or reproducing information by a laser is provided on a substrate, and the recording layer absorbs at a wavelength of 420 nm or less. An optical recording method is characterized in that information is recorded on an optical recording medium having a maximum and containing a compound represented by the following general formula (1).
Embedded image
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R ₁ Or R _Four Each independently represents a hydrogen atom or an optionally substituted alkyl group.
Also R ₁ Or R _Four Two or more selected from the above may combine to form a ring, R ₁ Or R _Four Each independently may be bonded to an atom constituting ring A or ring B to form a ring condensed with the ring. n and m each independently represents an integer of 0 to 2, and 1 ≦ n + m ≦ 2. )
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The compound used in the present invention is a dye having an absorption maximum in a blue light region of 420 nm and suitable for recording with a blue laser.
When designing a recording medium compatible with a blue semiconductor laser, the region at the bottom of the long wavelength side of the absorption spectrum peak of the dye is set to the oscillation wavelength of the laser in the same manner as the dye development in the existing CD-R and DVD-R. In order to improve the reflectance by combining them, a dye having an absorption maximum on the shorter wavelength side than the laser to be used is required. The preferred range of the absorption maximum wavelength of the dye corresponding to the oscillation wavelength (center wavelength) of the laser used varies depending on the shape of the spectrum, the absorbance value at the absorption maximum wavelength, etc., but is approximately 10 to 90 nm shorter than the oscillation wavelength. The case where it corresponds to the wavelength side is preferable.
[0012]
For example, as a dye for an optical recording medium corresponding to a blue semiconductor laser having an oscillation wavelength of 405 nm, which has been developed by Nichia and is about to be put to practical use, it is desirable that the absorption maximum wavelength is in the range of about 315 to 395 nm.
The absorption maximum may be the second absorption band or the like, but is preferably the maximum absorption wavelength.
Among such dyes, examples of the dye used in the optical recording medium of the present invention include dyes represented by the following general formula (1).
[0013]
[Chemical 6]
[0014]
(Wherein, ring A and ring B each independently represent an aromatic ring, R₁Or R_FourEach independently represents a hydrogen atom or an optionally substituted alkyl group.
  Also R₁Or R_FourTwo or more selected from the above may combine to form a ring, R₁Or R_FourEach independently may be bonded to an atom constituting ring A or ring B to form a ring condensed with the ring. n and m each independently represents an integer of 0 to 2, 1 ≦ n + m ≦2It is. )
  For convenience of explanation, in the general formula (1) showing the compound according to the present invention, when ring A and ring B are represented by benzene rings (also assumed in the following explanation),
[0015]
[Chemical 7]
[0016]
It is expressed. Here, n and m are the number of unsaturated bonds, each independently representing an integer of 0 to 2, and 1 ≦ n + m ≦2It is. Where R₁Or R_FourAre each independently a hydrogen atom or an optionally substituted alkyl group (that is, they are not involved in ring formation), the structure represented by the general formula (1) includes various direct structures as shown below. A chain structure may be mentioned. (Hereinafter, when n or m = 2, the bond extending from the unsaturated bond closer to the carbonyl is R, and the bond extending from the unsaturated bond closer to the ring A or B is R '.)
[0017]
[Chemical 8]
[0018]
  n + mIs 1~ 2.
  R₁Or R_FourIs a hydrogen atom or an optionally substituted alkyl group when not involved in ring formation. Among them, a hydrogen atom or a linear alkyl group is preferable, and a hydrogen atom or an unsubstituted linear alkyl group having 1 to 3 carbon atoms is more preferable.
[0019]
R₁Or R_FourTwo or more may be bonded to each other to form a ring. For example, in the case of n = 1 and m = 1, the mode of bonding as shown below may be mentioned.
[0020]
[Chemical 9]
[0023]
A plurality of combinations of bonds are conceivable, but considering the stability of the cyclic structure, synthesis method, steric hindrance, etc., those in which the α positions of the carbonyl group are bonded to each other, or those in which the α position and the β position are bonded are preferable Preferred are those bonded at the α-positions of the carbonyl group, that is, compounds represented by the following general formula (3).
[0024]
Embedded image
[0025]
(Wherein ring A and ring B have the same meanings as in formula (1), and R₁', R₁″ 、 R₂', R_Three', R_Four′ And R_Four"" Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A2 represents an optionally substituted hydrocarbon ring or heterocyclic ring. L = m-1, k = n-1. is there.)
R as above₁Or R_FourAre bonded to each other to form a cyclic structure, the bond indicated by a dotted line represents a cyclic structure formed by two Rs. A preferable structure as the cyclic structure formed by the dotted line, the carbon atom of the carbonyl group, and the carbon atom having an unsaturated bond is a 5- to 7-membered ring structure. In this case, it is preferable that the dotted line portion does not have an unsaturated bond, and is preferably a saturated hydrocarbon ring or a saturated heterocyclic structure containing a hetero atom and one or more carbon atoms. Further, these saturated hydrocarbon portions may have a substituent.
[0026]
R₁Or R_FourMay be independently bonded to atoms constituting ring A or ring B to form a ring condensed with the ring, and a plurality of the rings may be present in one molecule. Examples of these structures include the bonding modes as shown below.
[0027]
Embedded image
[0028]
As in the case of bonding between R, a plurality of combinations are conceivable. As a preferable structure for forming a condensed ring, the number of condensed rings is one per minute, and the α-position (R₂Or R_Three) Is preferably fused to either ring, particularly preferably n = 0 and R_ThreeIs condensed with ring A, that is, a compound represented by the following formula (2), or n = 1 and R₂Is condensed with ring A, that is, a compound represented by the following formula (4).
[0029]
Embedded image
[0030]
(Wherein ring A and ring B have the same meanings as in formula (1), and R_Three', R_Four′ And R_Four″ Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A1 represents an optionally substituted hydrocarbon ring or heterocyclic ring. L = m−1.
[0031]
Embedded image
[0032]
(Wherein ring A and ring B have the same meanings as in formula (1), and R₁, R_ThreeAnd R_FourEach independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A3 represents an optionally substituted hydrocarbon ring or heterocyclic ring. j represents 0 or 1; )
R₁Or R_FourWhen ring A or ring B forms a condensed ring, a structure preferable as a cyclic structure formed by the dotted line and the carbon atom of the carbonyl group, the carbon atom having an unsaturated bond, and ring A or ring B is 5 to 7-membered ring structure. In this case, the dotted line portion preferably has no unsaturated bond, and is preferably a saturated hydrocarbon ring or a saturated heterocyclic structure containing a hetero atom and one or more carbon atoms. Further, these saturated hydrocarbon portions may have a substituent.
[0033]
Ring A and ring B each independently represent an aromatic ring. Examples of the aromatic ring include aromatic hydrocarbon rings such as a benzene ring and a naphthyl ring, and aromatic heterocyclic rings such as a furan ring, a pyridine ring, and a quinoline ring. A preferable structure as these aromatic rings is preferably a 5- to 6-membered monocyclic ring or a 2-3 condensed ring thereof, and examples thereof include the following compounds.
[0034]
Embedded image
[0035]
Among these, a hydrocarbon ring or a heterocyclic structure, which is a 5- to 6-membered monocyclic or bicondensed ring, is particularly preferable.
In the present invention, the aromatic rings represented by ring A and ring B may have a substituent. The substituent used individually may be any and may be further substituted, but if it is too large, the basic skeleton is unexpectedly affected, so the molecular weight of the substituent is usually 1000 or less. There is no particular lower limit and it is 1 or more.
Examples of the optional substituent include the following. A straight chain or branched chain having 1 to 18 carbon atoms which may be substituted such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-heptyl group, etc. An alkyl group; a C3-C18 cyclic alkyl group such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, and an adamantyl group; an optionally substituted carbon number such as a vinyl group, a propenyl group, and a hexenyl group To 18 linear or branched alkenyl groups; such as cyclopentenyl group, cyclohexenyl group, etc.ReplaceA cyclic alkenyl group having 3 to 18 carbon atoms which may be substituted; 2-thienyl group, 2-pyridyl group, 4-piperidyl group, furfuryl group, morpholino group, etc.ReplaceA heterocyclic group which may be substituted; an aryl group having 6 to 18 carbon atoms which may be substituted such as phenyl group, tolyl group, xylyl group and mesityl group; and 7 carbon atoms which may be substituted such as benzyl group and phenethyl group -20 aralkyl groups; methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, etc. Or a branched alkoxy group; a linear or branched alkenyloxy group having 3 to 18 carbon atoms which may be substituted such as propenyloxy group, butenyloxy group, pentenyloxy group; phenoxy group tolyloxy group, xylyloxy group, naphthyloxy group, etc. An optionally substituted aryloxy group having 6 to 12 carbon atoms; methylthio group, ethylthio group, n-propylthio group, n- Chiruchio group, sec- butylthio group, such as tert- butylthio groupReplacedA linear or branched alkylthio group having 1 to 18 carbon atoms; halogen atom such as fluorine atom, chlorine atom, bromine atom, iodine atom; nitro group; nitroso group; cyano group; isocyano group; cyanato group; isocyanato Group: thiocyanato group; isothiocyanato group; mercapto group; hydroxy group; hydroxyamino group; formyl group; sulfonic acid group; carboxyl group;_FiveR₆An amino group represented by the formula: —NHCOR₇An acylamino group represented by -NHCOOR₈A carbamate group represented by: -COR₉An acyl group represented by -COOR_TenA carboxylic acid ester group represented by -CONR₁₁R₁₂A carbamoyl group represented by the formula: —OCOR₁₃An acyloxy group represented by formula: -SOR₁₄A sulfinyl group represented by -SO₂R₁₅A sulfonyl group represented by -SO₂NR₁₆R₁₇A sulfamoyl group represented by -SO_ThreeR₁₈A sulfonic acid ester group represented by: -NHSO₂R₁₉The sulfonamide group etc. which are represented by these are mentioned. A plurality of these substituents may be present in one ring regardless of the type of ring A or ring B. When it has a plurality of substituents, it may be the same or different. Also, the coupling position is not specified. Among these, an alkyl group, an alkoxy group, and a thioalkyl group may be substituted with a substituent described later.
[0036]
Where R₇, R₈, R₉, R_Ten, R₁₃, R₁₄, R₁₅, R₁₈, R₁₉Represents a hydrocarbon group which may be substituted or a heterocyclic group which may be substituted;_Five, R₆, R₁₁, R₁₂, R₁₆, R₁₇Represents a hydrogen atom, a hydrocarbon group which may be substituted, or a heterocyclic group which may be substituted.
This R_Five~ R₁₉Is a linear or branched alkyl group, a cyclic alkyl group, a linear or branched alkenyl group, a cyclic alkenyl group, an aralkyl group, or an aryl group. Among these, linear or branched alkyl having 1 to 18 carbon atoms such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group and n-heptyl group is preferable. Group, cyclopropyl group, cyclopentyl group, cyclohexyl group, adamantyl group, etc., cyclic alkyl group having 3-18 carbon atoms, vinyl group, propenyl group, hexenyl group, etc., linear or branched alkenyl group having 2-18 carbon atoms, C3-C18 cyclic alkenyl group such as cyclopentenyl group and cyclohexenyl group, C7-C20 aralkyl group such as benzyl group and phenethyl group, carbon number such as phenyl group, tolyl group, xylyl group and mesityl group 6-18 aryl groups are mentioned.
[0037]
The aryl group portion of these groups may be further substituted with the same substituents as those described above for ring A and ring B. Moreover, the alkyl chain part of these groups may be further substituted with the substituent mentioned later.
Also R_Five~ R₁₉The heterocyclic group represented by the formula can be a 4-piperidyl group, a morpholino group, a 2-morpholinyl group, a piperazyl group, or a saturated heterocyclic ring, a 2-furyl group, a 2-pyridyl group, a 2-thiazolyl group, or a 2-quinolyl group. An aromatic heterocyclic ring such as These may contain a plurality of heteroatoms, may further have a substituent, and may have any bonding position. Preferred structures for the heterocyclic ring are a 5- or 6-membered saturated heterocyclic ring, a 5- or 6-membered monocyclic ring, and an aromatic heterocyclic ring thereof.
[0038]
Specifically, -NR_FiveR₆An optionally substituted amino group represented by -NHCOR₇An optionally substituted acylamino group represented by -NHCOOR₈An optionally substituted carbamate group, -COR₉An optionally substituted acyl group represented by -COOR_TenAn optionally substituted carboxylic acid ester group represented by -CONR₁₁R₁₂An optionally substituted carbamoyl group represented by the formula: -OCOR₁₃An optionally substituted acyloxy group, -SOR₁₄An optionally substituted sulfinyl group represented by -SO₂R₁₅An optionally substituted sulfonyl group represented by -SO₂NR₁₆R₁₇An optionally substituted sulfamoyl group represented by -SO_ThreeR₁₈An optionally substituted sulfonic acid ester group represented by -NHSO₂R₁₉And an optionally substituted sulfonamide group and the like.
Amino group (-NR_FiveR₆)
[0039]
Embedded image
[0040]
Acylamino group (-NHCOR₇)
[0041]
Embedded image
[0042]
Carbamate group (-NHCOOR₈)
[0043]
Embedded image
[0044]
Acyl group (-COR₉)
[0045]
Embedded image
[0046]
Carboxylic acid ester group (-COOR_Ten)
[0047]
Embedded image
[0048]
Carbamoyl group (-CONR₁₁R₁₂)
[0049]
Embedded image
[0050]
Acyloxy group (-OCOR₁₃)
[0051]
Embedded image
[0052]
Sulfinyl group (-SOR₁₄)
[0053]
Embedded image
[0054]
Sulfonyl group (-SO₂R₁₅)
[0055]
Embedded image
[0056]
Sulfamoyl group (-SO₂NR₁₆R₁₇)
[0057]
Embedded image
[0058]
Sulfonic acid ester group (-SO_ThreeR₁₈)
[0059]
Embedded image
[0060]
Sulfonamide group (-NHSO₂R₁₉)
[0061]
Embedded image
[0062]
Ring A, Ring B may have a linear or branched alkyl group, a cyclic alkyl group, a linear or branched alkenyl group, a cyclic alkenyl group, a linear or branched alkoxy group, a straight or branched alkylthio group, and R_Five~ R₁₉The alkyl chain portion of the alkyl group represented by can further have a substituent, and examples of the substituent include the following.
Alkoxy groups having 1 to 10 carbon atoms such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group; methoxymethoxy group, ethoxymethoxy group, propoxymethoxy Groups, ethoxyethoxy groups, propoxyethoxy groups, methoxybutoxy groups, etc., alkoxyalkoxy groups having 2 to 12 carbon atoms; methoxymethoxymethoxy groups, methoxymethoxyethoxy groups, methoxyethoxymethoxy groups, methoxymethoxyethoxy groups, ethoxyethoxymethoxy groups, etc. An alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms; an aryl group having 6 to 12 carbon atoms such as a phenyl group, a tolyl group, and a xylyl group (these may be further substituted with any substituent); a phenoxy group , Tolyloxy group, xylylo Shi group, an aryloxy group having 6 to 12 carbon atoms such as naphthyloxy group; allyloxy group, an alkenyloxy group having 2 to 12 carbon atoms such as vinyloxy groups.
[0063]
Further, as other substituents, heterocyclic groups such as 2-thienyl group, 2-pyridyl group, 4-piperidyl group, morpholino group; cyano group; nitro group; hydroxyl group; amino group; N, N-dimethylamino group An alkylamino group having 1 to 10 carbon atoms such as N, N-diethylamino group; an alkylsulfonylamino group having 1 to 6 carbon atoms such as methylsulfonylamino group, ethylsulfonylamino group and n-propylsulfonylamino group; fluorine atom A halogen atom such as a chlorine atom or a bromine atom; an alkoxycarbonyl group having 2 to 7 carbon atoms such as a carboxyl group, a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, an isopropoxycarbonyl group, or n-butoxycarbonyl; Carbonyloxy group, ethylcarbonyloxy group, n-propylcarbonyl group An alkylcarbonyloxy group having 2 to 7 carbon atoms such as a cis group, an isopropylcarbonyloxy group, an n-butylcarbonyloxy group; a methoxycarbonyloxy group, an ethoxycarbonyloxy group, an n-propoxycarbonyloxy group, an isopropoxycarbonyloxy group, Examples thereof include an alkoxycarbonyloxy group having 2 to 7 carbon atoms such as an n-butoxycarbonyloxy group.
[0064]
Ring A and ring B have an alkoxy group, an alkylthio group, or —NR_FiveR₆In the case of a group, these may be bonded to each other to form a cyclic structure, or may be bonded to an atom constituting ring A or ring B to form a ring condensed with the ring. Moreover, you may form the heterocyclic ring containing a hetero atom by passing a hetero atom in a coupling | bond part. The heterocyclic ring formed by these is preferably a 5- to 7-membered saturated heterocyclic ring, and examples thereof include the ring structures shown below.
[0065]
Embedded image
[0066]
(Wherein X and X ′ represent a hydrogen atom or a group similar to the substituent which ring A and ring B may have. The condensed ring to ring A has a substituent other than X and X ′. It may be done, but it is omitted in the figure.)
If these condensation positions are between adjacent substituents, their positions and numbers are not specified. Further, these condensed ring hydrocarbons may have a substituent as described above as a group that the ring A and the ring B may have.
[0067]
Preferred examples of the substituent for ring A or ring B include an optionally substituted linear or branched alkyl group, a halogen atom, a nitro group, a cyano group, a hydroxy group, a mercapto group, an optionally substituted alkylthio group, An optionally substituted alkoxy group, a cyclic structure formed by bonding of the substituents together, a condensed ring formed by bonding to the atoms constituting the ring A or ring B, the ring A or ring B, substitution And an amino group, an acylamino group, a carbamate group, a carboxylic acid ester group, and a carbamoyl group.
[0068]
Among them, particularly preferred substituents include linear or branched alkyl groups, hydroxy groups, mercapto groups, optionally substituted alkylthio groups, optionally substituted alkoxy groups, and substituents that may be substituted. A cyclic structure to be formed, a condensed group formed by combining a substituent with an atom constituting ring A or ring B, a condensed ring to ring A or ring B, an optionally substituted amino group, or an acylamino group.
[0069]
As the bonding position of the substituent, when ring A or ring B is a benzene ring, the para position with respect to the main chain of the compound represented by the general formula (1) is preferable.
Although the following are mentioned as a preferable example of a compound represented by General formula (1), It is not limited to these.
[0070]
Embedded image
[0071]
Embedded image
[0072]
Embedded image
[0073]
Embedded image
[0074]
Embedded image
[0075]
Embedded image
[0076]
Embedded image
[0077]
Most of the compounds represented by the general formula (1) have a maximum absorption wavelength (λmax) of 420 nm or less, particularly in the relatively short wavelength region of about 320 to 400 nm when formed into a thin film, It has excellent optical characteristics for recording and reproduction using a blue semiconductor laser, such as a relatively sharp peak shape of the spectrum and a molar extinction coefficient ε of 20,000 or more. Here, the maximum absorption wavelength usually refers to the maximum absorption wavelength at a wavelength of 300 nm or more. In addition, since it is excellent in thin film formation in a state dissolved or dispersed in a solvent, it also satisfies the chemical characteristics required when manufacturing an optical recording medium. Therefore, the compound represented by the general formula (1) can be used very suitably for a recording layer of an optical recording medium for recording / reproducing using a blue semiconductor laser.
[0078]
The compound that can be used in the recording layer of the optical recording medium of the present invention has an optical density OD of 80 or more in a solution state, high solubility in a generally harmless and inexpensive solvent, and a thin film. It is more preferable that a high-quality film is formed (not crystallized at the time of film formation) and that storage stability in a solution state and a thin film state is good.
The recording layer of the optical recording medium of the present invention preferably has an extinction coefficient (imaginary part of complex refractive index) k of 0 to 0.20 at the recording and reproducing light wavelengths. Further, the refractive index (real part of the complex refractive index) n is preferably 1.8 or more.
[0079]
Next, the optical recording medium of the present invention will be described.
The optical recording medium of the present invention comprises at least a substrate and a recording layer containing the compound represented by the general formula (1). Furthermore, you may provide an undercoat layer, a reflection layer, a protective layer, etc. as needed.
As an example of a preferred layer structure, a high reflectance medium in which a recording layer is provided on a substrate, and a reflective layer and a protective layer are further laminated in this order on the substrate. In this case, information is recorded / reproduced by irradiating a laser beam from the substrate side (medium structure example 1).
Hereinafter, the optical recording medium of the present invention will be described using the medium having such a structure (medium structure example 1) as an example. In the following description, for convenience of explanation, the side on which the protective layer is present and the side on which the substrate is present at the time of stacking are regarded as upper and lower, respectively, and each surface of each layer corresponding to these directions is defined as the upper surface of each layer. And the lower surface.
[0080]
As the substrate in the optical recording medium of the present invention, substrates using various materials can be used as long as they are basically transparent at the wavelength of recording light and reproducing light. Specifically, for example, an acrylic resin, a methacrylic resin, a polycarbonate resin, a polyolefin resin (particularly amorphous polyolefin), a polyester resin, a polystyrene resin, an epoxy resin or the like, a glass substrate, glass Examples thereof include a substrate on which a resin layer made of a radiation curable resin such as a photocurable resin is provided.
Of these, an injection-molded polycarbonate substrate is preferred from the viewpoints of high productivity, cost, moisture absorption resistance, and the like. Further, from the viewpoint of chemical resistance, moisture absorption resistance, etc., an amorphous polyolefin substrate is preferred. Furthermore, a glass substrate is preferable from the viewpoint of high-speed response.
[0081]
When a resin substrate is used, or when a substrate provided with a resin layer on the side in contact with the recording layer (upper side) is used, a guide groove for recording / reproducing light is formed on the upper surface of the resin substrate or resin layer. Or pits may be formed. Examples of the shape of the guide groove include a concentric shape and a spiral shape based on the center of the optical recording medium. When the spiral guide groove is formed, the groove pitch is preferably about 0.2 to 1.2 μm.
A recording layer containing the compound represented by the general formula (1) is formed directly on the upper side of the substrate or on the upper side of an undercoat layer or the like provided on the substrate as necessary. As a method for forming the recording layer, various commonly 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 exemplified. From the viewpoint of mass productivity and cost, the spin coating method is preferable, and from the viewpoint of obtaining a recording layer having a uniform thickness, the vacuum evaporation method or the like is more preferable than the coating method. In the case of film formation by spin coating, the rotation speed is preferably 500 to 15000 rpm. In some cases, after spin coating, a treatment such as heating or solvent vapor may be applied.
[0082]
Coating used to dissolve and apply the compound represented by the general formula (1) to the substrate when the recording layer is formed by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method. The solvent is not particularly limited as long as it does not erode the substrate. Specifically, for example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chains such as n-hexane and n-octane Cyclic hydrocarbon solvents: Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane, cyclooctane; tetrafluoropropanol, octafluoropentanol, hexafluorobutanol, etc. Perfluoroalkyl alcohol solvents; hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.
[0083]
When using the vacuum evaporation method, for example, the compound represented by the general formula (1) and, if necessary, recording layer components such as other dyes and various additives are placed in a vacuum container. Place in a crucible and place in the vacuum vessel with a suitable vacuum pump.^-2-10^-FiveAfter evacuating to about Pa, the crucible is heated to evaporate the recording layer components and vapor deposited on a substrate placed facing the crucible to form a recording layer.
In addition to the compound represented by the general formula (1), the recording layer has a transition metal chelate compound (for example, acetylacetonate chelate) as a singlet oxygen quencher in order to improve stability and light resistance. Bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) or a recording sensitivity improver such as a metal compound may be added to improve recording sensitivity. Here, the metal compound refers to a compound 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 complex. Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex, and porphyrin complex. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.
[0084]
In the recording layer, a plurality of types of compounds represented by the general formula (1) may be used in combination as necessary.
Further, in the recording layer, in addition to the compound represented by the general formula (1), other types of dyes may be used in combination as necessary. Other dyes are not particularly limited as long as they have appropriate absorption mainly in the oscillation wavelength region of the recording laser. Further, it is used for CD-R and the like, and is used for dyes suitable for recording and reproduction using a near-infrared laser having an oscillation wavelength in a wavelength band of 770 to 830 nm, a DVD-R and the like, and a wavelength of 620 to 690 nm. A dye suitable for recording / reproduction using a red laser having an oscillation wavelength in the band is used in combination with the compound represented by the general formula (1) in the recording layer, whereby a plurality of dyes belonging to different wavelength bands It is also possible to manufacture an optical recording medium that supports recording / reproduction using various types of laser light.
[0085]
Examples of dyes other than the compound represented by the general formula (1) include metal-containing azo dyes, benzophenone dyes, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes. Metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes, etc. .
Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can also be used together as needed. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
[0086]
The film thickness of the recording layer is not particularly limited because the suitable film thickness varies depending on the recording method and the like, but since a certain film thickness is required to enable recording, it is usually at least 1 nm. Above, preferably 5 nm or more. However, even if it is too thick, there is a possibility that recording cannot be performed satisfactorily.
A reflective layer is formed on the recording layer. The film thickness is preferably 50 to 300 nm.
As a material of the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, alone or in an alloy Can be used. Among these, Au, Al, and Ag have high reflectivity and are suitable as a material for the reflective layer. In addition to these metals as main components, other materials may be added. Here, the main component means one having a content of 50% or more. Examples of materials other than the main component include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, and Ge. , Te, Pb, Po, Sn, Bi, Ta, Ti, Pt, Pd, Nd, and other metals and metalloids. Among them, those containing Ag as a main component are particularly preferable because they are low in cost, easily produce high reflectivity, and obtain a beautiful white background when a print receiving layer described later is provided. For example, an alloy containing about 0.1 to 5 atomic% of one or more selected from Au, Pd, Pt, Cu, and Nd in Ag is preferable because of high reflectivity, high durability, high sensitivity, and low cost. . Specifically, for example, an AgPdCu alloy, an AgCuAu alloy, an AgCuAuNd alloy, an AgAuNd alloy, an AgCuNd alloy, or the like. As a material other than the metal, a low refractive index thin film and a high refractive index thin film can be alternately stacked to form a multilayer film, which can be used as a reflective layer.
[0087]
Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. Also, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or below the reflective layer in order to improve reflectivity, recording characteristics, adhesion, and the like.
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 of the organic material include thermoplastic resins, thermosetting resins, electron beam curable resins, and UV curable resins. Examples of inorganic substances include silicon oxide, silicon nitride, and MgF.₂, SnO₂Etc.
When a thermoplastic resin, a thermosetting resin, or the like is used, a protective layer can be formed by applying a coating solution prepared by dissolving in a suitable solvent on the reflective layer and drying it. When UV curable resin is used, it is directly applied on the reflective layer, or a coating solution prepared by dissolving in a suitable solvent is applied on the reflective layer and cured by irradiating with UV light. A protective layer can be formed. As the UV curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or as a mixture of plural kinds. Further, the protective layer may be formed as a single layer or a multilayer.
[0088]
As a method for forming the protective layer, as with the recording layer, a coating method such as a spin coating method or a casting method, or a method such as a sputtering method or a chemical vapor deposition method is used. Of these, a spin coating method is preferable. The film thickness of the protective layer is generally 0.1 μm or more, preferably 3 μm or more, because a certain amount of thickness is required to fulfill its protective function. However, if it is too thick, not only the effect does not change, but also the formation of the protective layer may take time and the cost may increase, so it is usually 100 μm or less, preferably 30 μm or less.
In the above, the layer structure of the optical recording medium has been described by taking as an example the structure in which the substrate, the recording layer, the reflective layer, and the protective layer are laminated in this order. However, as described above, other layer structures may be employed. I do not care.
[0089]
For example, another substrate may be bonded to the upper surface of the protective layer in the layer structure of the above example or to the upper surface of the reflective layer by omitting the protective layer from the layer structure of the above example. The substrate at this time may be the substrate itself without any layers, or may have an arbitrary layer such as a reflective layer on the bonded surface or the opposite surface. Similarly, two optical recording media having the above-described layer structure and two optical recording media in which the protective layer is omitted from the above-described layer structure are disposed with the upper surfaces of the respective protective layers and / or reflective layers facing each other. You may stick together.
Furthermore, as an example of a preferred layer structure of the optical recording medium of the present invention, there is a medium in which a reflective layer is provided on a substrate, and a recording layer and a protective film are further laminated in this order. In this case, information is recorded / reproduced by irradiating a laser beam through the protective film (medium structure example 2).
[0090]
This protective film may be formed by bonding a film or a sheet with an adhesive, or by applying a coating liquid for film formation and curing or drying using the same material as the protective layer described above. You may do it. The thickness of the protective film is generally 0.1 μm or more, preferably 3 μm or more because a certain degree of thickness is required to fulfill the protective function. However, if it is too thick, not only the effect does not change, but also the formation of the protective layer may take time and the cost may increase, so it is usually 300 μm or less, preferably 200 μm or less.
Even in such a layer configuration, the recording layer, the reflective layer, and the like can be generally the same as those in the above-described medium structure example 1. However, in this layer structure, the substrate does not need to be transparent, and therefore, a substrate made of an opaque resin, ceramic, metal (including an alloy), or the like can be used in addition to the above-described materials.
[0091]
Even in such a layer structure, an arbitrary layer may be provided between the above-described layers as necessary as long as the characteristics of the present invention are not impaired.
Incidentally, as one means for increasing the recording density of the optical recording medium, there is a case where the numerical aperture of the objective lens is increased. Thereby, the light spot condensed on the information recording surface can be miniaturized. However, if the numerical aperture of the objective lens is increased, the light spot aberration caused by the warp of the optical recording medium is likely to increase when the laser beam is irradiated for recording / reproducing. May not be obtained stably.
Such aberration tends to increase as the film thickness of the transparent substrate or the protective film through which the laser beam is transmitted increases. Therefore, in order to reduce the aberration, it is preferable to make the substrate and the protective film as thin as possible. However, since the substrate usually requires a certain thickness in order to ensure the strength of the optical recording medium, in this case, the medium structure example 2 (substrate, reflection layer, recording layer, optical recording having a basic layer structure consisting of a thin protective film) Medium) is preferably employed. Compared with the case where the substrate of the medium structure example 1 is thinned, the protective film of the medium structure example 2 is easily thinned. Therefore, the medium structure example 2 is preferably used.
[0092]
However, even in the medium structure example 1 (optical recording medium having a basic layer structure including a transparent substrate, a recording layer, a reflective layer, and a protective layer), the thickness of the transparent substrate through which the recording / reproducing laser beam passes is 50 to 300 μm. By making it thin to the extent, it becomes possible to use with reduced aberration.
In addition, after the other layers are formed, an ultraviolet curable resin layer, an inorganic thin film, or the like is formed on the recording / reproducing laser light incident surface (usually the lower surface of the substrate) for the purpose of protecting the surface or preventing the adhesion of dust. Films may be formed and written or printed on various surfaces that are not the recording / reproducing laser light incident surface (usually the upper surface of the reflective layer or protective layer) using various printers such as inkjet and thermal transfer, or various writing tools. A possible print receptive layer may be provided.
In the optical recording medium of the present invention, the laser light used for recording / reproducing information is preferably as short as possible from the viewpoint of realizing high-density recording, but laser light having a wavelength of 350 to 530 nm is particularly preferable. Typical examples of such laser light include laser light having center wavelengths of 405 nm, 410 nm, and 515 nm.
The laser light of 350 to 530 nm can be obtained by using a high-power semiconductor laser of 405 nm, 410 nm blue or 515 nm blue-green. For example, (a) the fundamental oscillation wavelength is 740 to 960 nm continuously. Wavelength conversion is performed by a second harmonic generation element (SHG) for any of the oscillating semiconductor lasers and (b) a solid laser capable of continuous oscillation having a fundamental oscillation wavelength of 740 to 960 nm that is excited by the semiconductor laser. Can also be obtained.
[0093]
The SHG may be any piezoelectric element that lacks inversion 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, 430 nm which is a harmonic of the fundamental oscillation wavelength, and in the case of a solid-state laser excited by a semiconductor laser, Cr-doped LiSrAlF₆430 nm of a double wave from a crystal (fundamental oscillation wavelength 860 nm) can be mentioned.
When information is recorded on the optical recording medium of the present invention, the laser beam is usually focused to about 0.4 to 0.6 μm with respect to the recording layer (usually transmitting through the substrate from the substrate side). Irradiate. The portion of the recording layer irradiated with the laser beam undergoes thermal deformation such as decomposition, heat generation, and dissolution by absorbing the energy of the laser beam, so that the optical characteristics change.
When the recorded information is reproduced, the recording layer is also irradiated with a laser beam having a lower energy (usually from the same direction as during recording). In the recording layer, information is reproduced by reading the difference between the reflectance of the portion where the optical characteristics change (that is, the portion where information is recorded) and the reflectance of the portion where the change does not occur. It is.
[0094]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples unless it exceeds the gist.
[Synthesis of compounds]
As a method for synthesizing the compound represented by n + m = 1 or 2 in the general formula (1), it can be generally synthesized by dehydration condensation of an aromatic aldehyde and a ketone (having an active methylene group at the α-position), When the rings A and B are represented by benzene rings, they are represented as follows.
[0095]
A compound (chalcone) with n = 1 and m = 0 can be synthesized by adding a base (such as an aqueous NaOH solution) as a catalyst to an ethanol solution of benzaldehyde and acetophenone.
[0096]
Embedded image
[0097]
In a similar manner, a compound with n = 2 and m = 0 can be synthesized from cinnamaldehyde and acetophenone.
[0098]
Embedded image
[0099]
A compound of n = 1 and m = 1 (dibenzylideneacetone) can be synthesized from twice as much benzaldehyde and acetone (Organic Syntheses, Col. Vol. II, 167). Similarly, it can be reacted with a cyclic ketone.
[0100]
Embedded image
[0101]
As another method, for example, it can also be synthesized by Domino-Heck aldol condensation as described in Tetrahedron Letters, Vol 37, No, 5, p619 (1996).
[0102]
Embedded image
[0103]
Thus, by using a derivative of a benzene ring, a heteroaromatic ring, or the like, a compound as shown in the exemplified compound can be synthesized.
Example 1
(A) Production example
[0104]
Embedded image
[0105]
50 g of p-methoxyacetophenone represented by the above structural formula [I] was dissolved in 200 ml of ethanol, an aqueous solution of 2 g of sodium hydroxide / 50 ml of water was added thereto while stirring and cooled to 10 ° C. or lower in a water bath. 50 g of anisaldehyde represented by the above structural formula [II] was added dropwise to the solution so that the temperature did not exceed 10 ° C.
After completion of dropping, the mixture was stirred at 10 ° C. or lower for 3 hours and left overnight. On the next day, 200 ml of water was added to the solution in which crystals were precipitated, and the mixture was further stirred and filtered.
[0106]
The obtained crude crystals are dissolved in 400 ml of THF, dehydrated by adding potassium carbonate, added with 100 ml of ethanol, heated and concentrated, cooled, filtered and dried to obtain 75.5 g of exemplary compound (1). (Yield 84%, MS; m / z = 268 confirmed). Maximum absorption wavelength of product in chloroform solution λmax = 340.5 nm, molar extinction coefficient 3.1 × 10^FourMet. The absorption spectrum in the chloroform solution is shown in FIG.
(B) Recording medium example
Exemplary compound (1) was dissolved in octafluoropentanol and adjusted to 1.0 wt%. A solution obtained by filtering this was dropped onto an injection-molded polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm, applied by a spinner method, and dried at 100 ° C. for 30 minutes after application. The maximum absorption wavelength (λmax) of this coating film was 341.5 nm. The absorption spectrum of the coating film is shown in FIG.
Example 2
[0107]
Embedded image
[0108]
200 g of ethanol was dissolved in 50 g of the above-mentioned p-methoxyacetophenone, and 2 g of sodium hydroxide / 50 ml of water was added to the solution while stirring. To this solution, 52 g of α-methylcinnamic aldehyde represented by the above structural formula [III] was dropped so that the temperature would not exceed 10 ° C. After completion of dropping, the mixture was stirred at 10 ° C. or lower for 3 hours and left overnight. On the next day, 300 ml of water was added to the solution in which crystals were precipitated, and the mixture was further stirred and filtered.
[0109]
The obtained crude crystals are dissolved in 200 ml of THF, dehydrated by adding potassium carbonate, then added with 200 ml of ethanol, heated and concentrated, cooled, filtered and dried to obtain 48.3 g of Exemplified Compound (2). (Yield 52%, MS; m / z = 278 confirmed). Λmax = 335.5 nm of product in chloroform, molar extinction coefficient is 3.8 × 10^FourMet.
(B) Recording medium example
Exemplary compound (2) was dissolved in diisobutyl ketone and adjusted to 1.0 wt%. A solution obtained by filtering this was dropped onto an injection-molded polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm, applied by a spinner method, and dried at 100 ° C. for 30 minutes after application. The maximum absorption wavelength (λmax) of this coating film was 334.5 nm.
Example 3
(A) Production example
[0110]
Embedded image
[0111]
0.89 g (5 mmol) of 4-n-butoxybenzaldehyde represented by the above compound [IV] was dissolved in 15 ml of ethanol, and 0.73 g (5 mmol) of α-tetralone represented by the above compound [V] was added dropwise thereto. While stirring this solution at room temperature, 3 ml of 25% aqueous sodium hydroxide solution was added dropwise and stirred for 10 hours.
Thereafter, this solution was filtered, and the obtained filtrate was washed with methanol and dried to obtain 1.2 g (yield 96%) of Exemplary Compound (15). Λmax = 344.5 nm of product in chloroform, molar extinction coefficient is 2.0 × 10^FourMet.
(B) Recording medium example
The compound of exemplary compound (15) was dissolved in octafluoropentanol and adjusted to 1.0 wt%. A solution obtained by filtering this was dropped onto an injection-molded polycarbonate resin substrate having a diameter of 120 mm and a thickness of 1.2 mm, applied by a spinner method, and dried at 100 ° C. for 30 minutes after application. The maximum absorption wavelength (λmax) of this coating film was 348 nm.
[0112]
Examples 4-23
Hereinafter, the compounds of Exemplified compounds (3) to (14) and (49) to (56) were synthesized by the same method as the synthesis method described above, and Examples 1 to 1 were used except that the solvents shown in Table-1 were used. A coating film was formed in the same manner as in 3.
The maximum absorption wavelength, molar extinction coefficient, and maximum absorption wavelength in the coating film of the synthesized compound in chloroform are shown in Table 1 together with the results of Examples 1 to 3.
[0113]
[Table 1]
[0114]
On these coating films, for example, Ag or the like is formed by a sputtering method or the like to form a reflective layer, and then an ultraviolet curable resin is applied by a spin coating method or the like and then irradiated with ultraviolet rays to be cured. An optical recording medium can be obtained by forming a protective layer. It is apparent that these optical recording media can be recorded and reproduced by a semiconductor laser having a central wavelength of 405 nm, for example, from the value of the maximum absorption wavelength (λmax) of the coating film.
[0115]
【The invention's effect】
The solution containing the compound of the present invention can form a coating film having an absorption suitable for recording / reproduction with a laser beam having a short wavelength and is excellent in film formability. Therefore, a recording layer using the compound of the present invention Is useful as an optical recording medium for recording and reproduction corresponding to a short wavelength laser.
Therefore, if information is recorded on this optical recording medium using a short-wavelength laser beam having a wavelength of 350 nm to 530 nm, it is possible to record / reproduce information with higher density and larger capacity.
[Brief description of the drawings]
FIG. 1 is an absorption spectrum of exemplary compound (1) in a chloroform solution in Example 1 of the present invention.
FIG. 2 is an absorption spectrum of a coating film of exemplary compound (1) in Example 1 of the present invention.

Claims (11)

In an optical recording medium provided with a recording layer capable of recording or reproducing information by a laser on a substrate, the recording layer has a compound represented by the following general formula (5) having an absorption maximum at a wavelength of 420 nm or less. An optical recording medium comprising:
(In the formula, each of ring A and ring B independently represents an optionally substituted aromatic ring, and R ₁ to R ₄ each independently represents a hydrogen atom or an optionally substituted alkyl group.
Two or more selected from R ₁ to R ₄ may be bonded to form a ring, and R ₁ to R ₄ are each independently bonded to the atoms constituting Ring A or Ring B and bonded to the ring. A ring to be condensed may be formed. n represents 1 or 2, and m = 0. ) In the general formula (1), R ₁ to independently R ₄ are each an alkyl group which may optionally be a hydrogen atom or a substitution, an optical recording medium according to claim 1. In an optical recording medium provided with a recording layer capable of recording or reproducing information by a laser on a substrate, the recording layer has a compound having an absorption maximum at a wavelength of 420 nm or less and represented by the following general formula (2): An optical recording medium comprising:
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R ₃ ′, R ₄ ′ and R ₄ ″ each independently represent a hydrogen atom or a substituted atom. Represents an alkyl group, ring A1 represents an optionally substituted hydrocarbon ring or heterocyclic ring, l represents 0 or 1 ) In an optical recording medium provided with a recording layer capable of recording or reproducing information by a laser on a substrate, the recording layer has a compound having an absorption maximum at a wavelength of 420 nm or less and represented by the following general formula (4): An optical recording medium comprising:
(In the formula, ring A and ring B each independently represent an optionally substituted aromatic ring, and R ₁ , R _Three And R _Four Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A3 represents an optionally substituted hydrocarbon ring or heterocyclic ring. j represents 0 or 1; ) In the general formulas (5), (2) and (4) , the ring A and the ring B each independently represent a 5- to 6-membered monocyclic ring or a 2-3 condensed ring, The optical recording medium according to any one of claims 1 to 4 . Wavelength using a laser over light 350～530Nm, recording or reproducing information by laser on the substrate capable recording layer is provided, the recording layer has an absorption maximum below a wavelength 420nm and the following general formula ( An optical recording method comprising recording information on an optical recording medium containing the compound represented by 1) .
(In the formula, each of ring A and ring B independently represents an optionally substituted aromatic ring, and R ₁ to R ₄ each independently represents a hydrogen atom or an optionally substituted alkyl group.
Two or more selected from R ₁ to R ₄ may be bonded to form a ring, and R ₁ to R ₄ are each independently bonded to the atoms constituting Ring A or Ring B and bonded to the ring. A ring to be condensed may be formed. n and m each independently represents an integer of 0 to 2, and 1 ≦ n + m ≦ 2. ) In the general formula (1), R ₁ Or R _Four The optical recording method according to claim 6, wherein each independently represents a hydrogen atom or an optionally substituted alkyl group. The optical recording method according to claim 6, wherein the compound represented by the general formula (1) is represented by the following general formula (2).
(Wherein ring A and ring B have the same meanings as in formula (1), and R _Three ', R _Four ′ And R _Four ″ Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A1 represents an optionally substituted hydrocarbon ring or heterocyclic ring. L = m−1. The optical recording method according to claim 6, wherein the compound represented by the general formula (1) is represented by the following general formula (3).
(Wherein ring A and ring B have the same meanings as in formula (1), and R ₁ ', R ₁ ″ 、 R ₂ ', R _Three ', R _Four ′ And R _Four ″ Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A2 represents an optionally substituted hydrocarbon ring or heterocyclic ring. L = m−1, k = n−1. Represents.) The optical recording method according to claim 6, wherein the compound represented by the general formula (1) is represented by the following general formula (4).
(Wherein ring A and ring B have the same meanings as in formula (1), and R ₁ , R _Three And R _Four Each independently represents a hydrogen atom or an optionally substituted alkyl group. Ring A3 represents an optionally substituted hydrocarbon ring or heterocyclic ring. j represents 0 or 1; ) In the general formulas (1) to (4), the ring A and the ring B each independently represent a 5- to 6-membered monocyclic ring or a 2-3 condensed ring, which may be substituted, The optical recording method according to claim 6.