JPS63115172A - Photoconductive composition - Google Patents

Abstract

PURPOSE:To enhance storage stability and sensitization efficiency by using a photoconductive composition containing a photoconductor, a binder resin, and a sensitizing dye represented by a specified formula. CONSTITUTION:The photoconductive composition contains as the sensitizer the dye represented by formula I in which each of n and m is 0-3; each of p and q is 0 or 1; L is an optionally substituted methine group; R1 is H or alkyl; each of R2, R3, and R4 is optionally same or different, and each is H, alkyl, or the like; each of Z1 and Z2 is O, S or the like; each of Q1 and Q2 is optionally substituted pyrane, benzopyrane, or the like; each of Y1-Y4 is optionally same or different, and each of H, an aliphatic or aromatic group; X<-> is an anion; and r is 1 or 2, and when the dye forms an intramolecular salt, r is 1.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a photoconductive composition comprising a photoconductor dispersed in a binder resin, in which the photoconductor is spectrally sensitized with a novel dye. TECHNICAL FIELD The present invention relates to photoconductive compositions.

(Prior Art) Many spectral enhancing dyes are already known in electrophotographic photosensitive layers of photoconductor-resin dispersion systems. There are various properties required of these spectral sensitizing dyes, including good adsorption to the photoconductor, high exacerbation efficiency, and not lowering the resistance of the electrophotographic photosensitive layer in the dark more than necessary. This is a particularly important point. Examples of dyes that meet these requirements are U.S. Pat. Nos. 3,052,540 and 3,110,591.
No. 3125447, No. 3128179, No. 3'
No. 132942, No. 3241959 and No. 3121
No. 008 and British Patent No. 1,093,823.

On the other hand, dyes for spectral sensitization to red light or infrared rays are described in U.S. Pat. In particular, polymethine dyes with long methine chains (eg, 5 or more) are the main focus.

(Problems that the invention seeks to solve) However, these dyes are generally easy to decompose.

However, there was a major practical drawback in that the dye was significantly decomposed during storage or during the manufacturing process and storage of the electrophotographic photosensitive layer, resulting in a decrease in performance. Harasaki et al. state that sensitizing dyes to red or infrared light are more unstable than sensitizing dyes to shorter wavelength light (visible light). (“
Industrial Chemistry Magazine, Vol. 66, No. 2, p. 26 (1963). In particular, this instability tends to increase as the methine chain in the sensitizing dye becomes longer. The appearance of pigment is desired.

Furthermore, it is desired that a dye with high exacerbation efficiency against long wavelength light as described above be developed.

Therefore, an object of the present invention is to provide a photoconductor-resin dispersion photoconductive composition containing a spectral enhancement dye that has excellent storage stability and high exacerbation efficiency.

Another object of the present invention is to provide a photoconductive composition that can be used as a photoreceptor for electrophotography using a laser as a light source.

A further object of the present invention is to provide a photoconductive composition containing, as a spectral exacerbating agent, a novel dye that is colorless and transparent, has absorption in far-infrared to near-infrared, and provides high exacerbation efficiency. .

(Means for solving the problem) The purpose of this is to provide a photoconductive composition containing a photoconductor, a sensitizing dye, and a binder resin, in which the sensitizing dye is represented by the following general formula [I]. It has been found that this can be achieved by a photoconductive composition characterized in that it is a compound of

General formula (I) In formula (I), n and m are each 0. 1. Represents 2 or 3. However, n and m never become O at the same time.

p and q each represent 0 or 1.

L represents a methine group or a substituted methine group.

R1 represents a hydrogen atom or an alkyl group.

R2, R3 and R4 are the same or different, and each represents a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, a substituted or unsubstituted amino group, or a halogen atom, and/or R2, R3, and R1 R4 and/or R2 and R form a fused 6-membered ring.

2 and Z2 each represent an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom or >NR.

However, >NR is not expressed at the same time. Here R
1 represents a substituted or unsubstituted alkyl group.

Q and Q2 each may be substituted, pyran, benzopyran, naphthopyran, thiopyran, benzothiopyran, naphthothiopyran, selenapyran, benzoselenapyran, naphthoselenapyran, ternapyran, penzoternapyran or naphthoselenapyran, or contain a nitrogen atom represents a group of atoms necessary to form an optionally substituted heterocycle. However, Ql and Q2 do not represent a nitrogen atom-containing heterocycle at the same time.

Y+, Yz, Y2 and Y4 may be the same or different, and each represents a hydrogen atom, an aliphatic group or an aromatic group.

xO represents an anion.

r represents 1 or 2. However, when the dye forms an inner salt, r is 1.

Each substituent in the compound represented by general formula (1) is preferably the substituent shown below.

That is, R1 is a hydrogen atom or an alkyl group having 4 or less carbon atoms (
For example, methyl group, ethyl group, propyl group, etc.) are preferred.

L represents a methine group or a substituted methine group, and substituents for the methine group include alkyl groups having 1 to 4 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, etc.), and 7 to 10 carbon atoms. Preferred are aryl groups up to, substituted alkyl groups (eg, benzyl group, phenethyl group, 3-phenylpropyl group, 4-phenylbutyl group, etc.), and aryl groups having 6 to 10 carbon atoms (eg, phenyl group, naphthyl group, etc.).

It is also preferable to crosslink between methylene groups with a trimethylene group to form a 6-membered carbon ring on the methylene chain.

The alkyl groups for Rz, Ri and R4 include lower alkyl groups having 1 to 4 carbon atoms (for example, methyl group, ethyl group,
isopropyl group, butyl group, etc.), and the alkoxy group is preferably an alkoxy group having 1 to 4 carbon atoms (eg, methoxy group, ethoxy group, propoxy group, butoxy group, etc.).

Rz, R3 and R4 are unsubstituted or substituted amino or may be different, hydrogen atom, lower alkyl group having 1 to 4 carbon atoms (e.g. methyl group, ethyl group, propyl group, butyl group, etc.), 2 to 4 carbon atoms; No. 8 acyl groups (eg, acetyl group, propionyl group, benzoyl group, etc.) are preferred.

It is also preferable that R6 and R1 are linked to each other to form a 5-membered ring or a 6-membered ring. Furthermore, R6 and/or R7 may be bonded to the benzene ring of the benzopyrylium ring to form a condensed ring.

When either ZI or Z2 represents ;N-RS, Q or Q2 represents a nitrogen atom-containing 5- to 6-membered heterocycle which may have a substituent, and the ring Examples include thiazole nuclei (eg, thiazole, 4-methylthiazole, 4-phenylthiazole, 5-methylthiazole, 5-phenylthiazole, 4,5-dimethylthiazole, 4,5-diphenylthiazole, 4.
(2-chenyl)thiazole, etc.), benzothiazole nuclei (e.g. benzothiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, 5-methyl Benzothiazole, 6-
Methylbenzothiazole, 5-bromobenzothiazole, 6-bromobenzothiazole, 5-trifluoromethylbenzothiazole, 5-phenylbenzothiazole,
4-methoxybenzothiazole, 5-methoxybenzothiazole, 6-methoxybenzothiazole, 5-carboxybenzothiazole, 5-cyanobenzothiazole,
5-fluorobenzothiazole, 5-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6-simethoxybenzothiazole, 5-hydroxybenzothiazole, 6-hydroxybenzothiazole, etc.), naphthothiazole nuclei (e.g. 2-d) Thiazole, naphtho[2,1-d) Thiazole, naphtho[2゜3-d]thiazole, 5-methoxynaphtho[2゜1-d
) thiazole, 5-ethoxynaphtho[2゜1-d]thiazole, 8-methoxynaphtho[1゜2-d]thiazole, 7-methoxynaphtho[1゜2-d]thiazole, etc.)
, oxazole nucleus (e.g. 4-methyloxazole, 5
-Methyloxazole, 4-phenyloxazole, 4
, 5-diphenyloxazole, 4-ethyloxazole, 4.5-dimethyloxazole, 5-phenyloxazole, etc.), benzoxazole nuclei (e.g. benzoxazole, 5-chlorobenzoxazole, 5-methylbenzoxazole, 5-phenylbenzoxazole) , 6-methylbenzoxazole, 5,6-dimethylbenzoxazole, 4.6-dimethylbenzoxazole, 5-methoxybenzoxazole, 5-ethoxybenzoxazole, 5-fluorobenzoxazole, 6-ethoxybenzoxazole, 5 -hydroxybenzoxazole, 6-hydroxybenzoxazole, etc.), naphthoxazole core (e.g. naphtho (1,2
-d) Oxazole, naphtho[2,1-d)oxazole, naphtho(2,3-d)oxazole, etc.), selenazole nucleus (e.g. selenazole, 4-methylselenazole, 4-phenylselenazole, 4,5-diphenyl selenazole, etc.), benzoselenazole core (e.g. benzoselenazole, 5-chlorobenzoselenazole, 5-methylbenzoselenazole, 5-methoxybenzoselenazole, 5-phenylbenzoselenazole, etc.), naphthoselenazole core ( For example, naphtho[1,2-d) selenazole, naphtho(2,1-d) selenazole, naphtho(2,3
-d) selenazole, etc.), imidazole core (e.g. l-
ethylimidazole, 1-benzylimidazole, etc.)
, benzimidazole core (e.g. 1.3-diethylbenzimidazole, 1.3-diethyl-5,6-dichlorobenzimidazole, 1.3-diethyl-5-trifluoromethyl-6-chlorobenzimidazole, 1.3
-diethyl-5-cyano-6-chlorobenzimidazole, etc.), naphthoimidazole core (e.g. IH-naphtho(
2,3-d) imidazole), thiazoline nucleus (e.g. thiazoline, 4-methylthiazoline, 4-phenylthiazoline, etc.), imidazoquinoline nucleus (e.g. IH-imidazo(4,5-b)quinoline, etc.), imidazo[4° 5-b]
Quinoxaline core (e.g. 1,3-diethylimidazo (
4,5-b) quinoxaline, 1°3-diallylimidazo(4,5-b)quinoxaline, 1,3-diphenylimidazo(4,5-b)quinoxaline, 6-chloro-1,3
-diethyl-imidazo(4,5-b)quinoxaline, 6
-Chloro-1,3-diallylimidazo (4,5-b)
quinoxaline, 6,7-dichloro-1,3-diphenylimidazo(4,5-b)quinoxaline, etc.), oxazoline nucleus (e.g., 5,5-dimethyloxazoline, etc.), isoxazole nucleus (e.g., 5-methylisoxazole, etc.) , benzisoxazole nucleus (e.g. benzisoxazole etc.), 3°3-dialkylindolenine nucleus (e.g. 3,3-dimethylindolenine, 3.3.5-
) Dimethylindolenine, 5-chloro-3,3-dimethylindolenine, 5-ethoxycarbonyl-3,3-dimethylindolenine, 5-carboxy-3,3-dimethylindolenine, 5-sulfo-3,3- dimethylindolenine, etc.), 2-pyridine nucleus (e.g. pyridine, 5-methylpyridine, etc.), 4-pyridine nucleus (e.g. pyridine, etc.), 2-quinoline nucleus (e.g. 6-nitoxyquinoline, 6-nitoxyquinoline, etc.)
-ethylquinoline, 6-chloroquinoline, 8-fluoroquinoline, etc.), 4-quinoline nucleus (e.g., 8-methylquinoline, 8-fluoroquinoline, 6-chloroquinoline, etc.), and 1-isoquinoline nucleus (e.g., isoquinoline, etc.) are preferred. .

R3 is an unsubstituted alkyl group having 18 or less carbon atoms (e.g., methyl group, ethyl group, propyl group, butyl group, pentyl group, octyl group, decyl group, dodecyl group, octadecyl group, vinylmethyl group, cyclohexyl group, etc.) ) or substituted alkyl group [substituents include, for example, carboxy group, sulfo group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom), hydroxy group, carbon number 8
The following alkoxycarbonyl groups (e.g. methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl group, benzyloxycarbonyl group, etc.), alkoxy groups having 8 or less carbon atoms (e.g. methoxy group, ethoxy group, benzyloxy group, phenethyloxy group, etc.) , carbon number 10
The following monocyclic aryloxy groups (e.g. phenoxy group, p-tolyloxy group, etc.), acyloxy groups having 3 or less carbon atoms (e.g. acetyloxy group, propionyloxy group, etc.), acyl groups having 8 or less carbon atoms (e.g. acetyloxy group), group, propionyl group, benzoyl group, mesyl group, etc.), carbamoyl group (e.g. carbamoyl group, N,N-dimethylcarbamoyl group, morpholinocarbonyl group, piperidinocarbonyl group, etc.), sulfamoyl group (e.g. sulfamoyl group, N,N -dimethylsulfamoyl group,
morpholinosulfonyl group, piperidinosulfonyl group, etc.), aryl group having 10 or less carbon atoms (for example, phenyl group,
An alkyl group having 18 or less carbon atoms substituted with 4-chlorophenyl group, 4-methylphenyl group, α-naphthyl group, etc.) is preferable.

X○ represents an anion, and specifically preferred are chloride, bromide, iosito, thiocyanate, perchlorate, paratoluenesulfonate, and tetrafluoroborade.

2, and 2. further represents an oxygen atom, a sulfur atom, a selenium atom or a tellurium atom. Q and Q2 may each be substituted, pyran, benzopyran, naphthopyran,
Represents the atomic group necessary to form thiopyran, benzothiopyran, naphthothiopyran, selenapyran, benzoselenapyran, naphthoselenapyran, telnaviran, benzoylnapyran or naphthoselenapyran.

Substituents that Ql and Q2 can have include halogen atoms (for example, chlorine atoms, bromine atoms, etc.), carbon atoms with 1
-22 optionally substituted alkyl groups (e.g. methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, chloromethyl group, cyanomethyl group, hydroxyethyl group, etc.), carbon number 1 - 20 alkoxy groups (e.g. methoxy group, ethoxy group, propioxy group, butyloxy group, hexyloxy group, decyloxy group, etc.), optionally substituted aralkyl groups having 7 to 22 carbon atoms (e.g. benzyl group, phenethyl group, etc.), Carbon number 6-2
2 optionally substituted aryl groups (e.g. phenyl group,
Tolyl group, naphthyl group, chlorophenyl group, dichlorophenyl group, butylphenyl group, methoxyphenyl group, ethoxyphenyl group, hydroxyphenyl group, N, N-
dimethylaminophenyl group, methoxycarbonylphenyl group, ethoxycarbonylphenyl group, cyanophenyl group, methanesulfonylphenyl group, etc.), hydroxyl group, cyano group, alkyloxycarbonyl group having 1 to 22 carbon atoms (e.g. methoxycarbonyl group, ethoxycarbonyl group) group, propoxycarbonyl group, butoxycarbonyl group, etc.), aryloxycarbonyl group having 6 to 22 carbon atoms (
For example, phenyloxycarbonyl group, chlorophenyloxycarbonyl group, tolyloxycarbonyl group, butylphenyloxycarbonyl group, methoxyphenyloxycarbonyl group, etc.), C1-C22 alkanesulfonyl group (for example, methanesulfonyl group, ethanesulfonyl group, propane sulfonyl group, butanesulfonyl group, hexylsulfonyl group, etc.), arylsulfonyl group having 6 to 22 carbon atoms (e.g. benzenesulfonyl group, etc.), carbon number 1 to
28 optionally substituted amino groups (e.g. amino group, N
-methylamino group, N,N-dimethylamino group, N-ethylamino group, N,N-diethylamino group, N, N
-propylamino group, N, N-dibutylamino group, N-
methyl-N-phenylamino group, N-phenylamino group, N-benzylamino group, etc.).

Y+, Yz, '/I and Y4 may be the same or different, and each represents a hydrogen atom, an optionally substituted alkyl group having 1 to 22 carbon atoms (e.g., methyl group, ethyl group, propyl group, butyl group). group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, tetrodecyl group, etc.)
, optionally substituted cycloalkyl group having 5 to 22 carbon atoms (e.g., cyclopentyl group, cyclohexyl group, etc.), optionally substituted aralkyl group having 7 to 22 carbon atoms (e.g., benzyl group, phenethyl group, etc.), substituted Aryl group having 6 to 22 carbon atoms (for example, phenyl group, tolyl group, butylphenyl group, chlorophenyl group, dichlorophenyl group, methoxyphenyl group, naphthyl group, bromophenyl group, cyanophenyl group, methanesulfonylphenyl group) N, N-dimethylaminophenyl group, N, N-
dibutylaminophenyl group, methoxycarbonylphenyl group, ethoxycarbonylphenyl group, etc.).

X○ represents an anion, and preferred examples include chloride, bromide, iosito, perchlorate, paratofrenesulfonate, methylsulfate, ethylsulfate, and tetrachloroborade. r represents 1 or 2, and r is 1 when the compound forms an inner salt.

Specific examples of the compound represented by the general formula (1) according to the present invention are described below, but the present invention is not limited thereto.

Compound-4 Compound-5 Compound-6 Compound-8 Compound-11 Compound-12 Compound-13 Compound-15 Compound-16 Compound-17 Compound-18 Compound-20 Compound-21 Compound-22 Compound-23 Compound-24 Compound- 26 Compound-28 Compound-30 Compound-31 Compound-33 Compound-34 Compound-35 O Compound-37 B F aθ Compound-38 The polymethine dye of the present invention can be produced using a conventionally known method. That is, substituted pyrylium salts include, for example, J-uthan, Advncesin
Heterocyclic Chemistry No. 34
Vol. 146 (1983), U.S. Patent No. 42837
No. 5 or R-J-Murry+j・org,
Chem, 47. 5235 (1982) and the like.

Further, quaternary salts of heterocycles containing a nitrogen atom include, for example, G
-F jDuffin Advances in
Heterocyclic chemistry volume 3,
1 (1964), etc., according to the synthesis method described.

The compound represented by general formula CI) can be synthesized by various synthetic methods, but for example, as shown in reaction formula A or B below, a heterocyclic tetracyclic compound having an active methyl group synthesized as described above can be used. Intermediate (A) or intermediate (
It can be synthesized by reaction of intermediate (P) with B) or intermediate (Q).

Reaction formula (A:) (XρLx-+ R" Intermediate (A) Intermediate CP) Reaction formula (B:) (Xp)B-t " (Xp)-z-+ " Intermediate CB) □ Dye [General Formula (1) In the above formula, Y represents a leaving group that is often used when synthesizing a dye, such as a halogen atom (such as a chlorine atom).
, substituted amino groups (e.g. N-acetylanilino group, dimethylamino group, etc.), substituted mercapto groups (e.g. methylthio group, ethylthio group, 3-sulfopropylthio group, 4
-sulfobutylthio group, etc.), sulfonate group, alkoxy group (eg, methoxy group, ethoxy group, phenoxy group, etc.).

X10 and Xp represent anions.

rlsr! , represents 1 or 2, and is 1 when the molecule forms an inner salt.

R2, R4, R4, R6, Z3, Z2, Yl, Y2, Y
l, Y4, n, mSp, and q have the same meanings as explained in general formula (1).

The synthesis of the dyes of the present invention is described, for example, in U.S. Pat.
00 or U.S. Pat. No. 2,756,227, as well as various other methods.
ames wlrThe Theory of the
・Photographic Process J No. 4
Edition (Macmillan Publishing Company N
ew York, 1977) and F.M.

The Cyanine Dyes by Harmen
and Re1ated Com-poundsJ (
John Wikey & 5ans, New Y
ork, published in 1964).

The polymethine dyes of formula (1) of the present invention are used as aggravating agents for inorganic and organic photoconductive materials to improve the photoconductivity and sensitivity properties of various photoconductive materials.

As the inorganic photoconductive substance, zinc oxide, titanium oxide, zinc sulfide, cadmium sulfide, etc. can be used. Examples of organic photoconductive substances include polymeric substances.
The following (1) to (5) can be mentioned.

(1) Polyvinylcarbazole and its derivatives described in Japanese Patent Publication No. 34-10966, (2) Japanese Patent Publication No. 43-1
Polyvinylpyrene, polyvinylanthracene, poly-2 described in JP-A No. 8674 and Japanese Patent Publication No. 43-19192
-vinyl-4-(4'-dimethylaminophenyl)-5
-vinyl polymers such as phenyl-oxazole and poly-3-vinyl-N-ethylcarbazole; (3) polyacenaphthylene, polyindene, and copolymers of acenaphthylene and styrene described in Japanese Patent Publication No. 19193-1973; (4) Condensation resins such as pyrene-formaldehyde resin, brompyrene-formaldehyde resin, and ethylcarbazole-formaldehyde resin described in Japanese Patent Publication No. 56-13940, (5) Japanese Patent Publication No. 56-90833, 56-16155
Various triphenylmethane polymers described in Publication No. 0.

Examples of low molecular weight compounds include the following (6) to (18).

(6) Triazole derivatives described in US Pat. No. 3,112,197, etc.; (7) Oxadiazole derivatives, described in US Pat. No. 3,189,447, etc.;
Imidazole derivatives described in Publication No. 16096, etc. (9) U.S. Patent No. 3615402, U.S. Patent No. 382098
No. 9, No. 3542544, Special Publication No. 45-555, No. 10983-1983, Japanese Patent Publication No. 93224-1971,
JP-A-55-17105, JP-A-56-4148,
JP-A-55-108667, JP-A-55-15695
No. 3, polyarylalkane derivatives described in JP-A-56-36656, publications, etc. (10) U.S. Pat. No. 3180729, U.S. Pat. No. 42787
No. 46, JP-A-55-88064, JP-A-55-88
No. 065, JP-A-49-105537, JP-A-55-
No. 51086, JP-A-56-80051, JP-A-56
-88141, JP-A-57-45545, JP-A-5
Pyrazoline derivatives and pyrazolone derivatives described in No. 4-112637, JP-A-55-74546, publications, etc.

(11) U.S. Patent No. 3,615,404, Japanese Patent Publication No. 5
1-10105, JP-A-54-83435, JP-A-54-110836, JP-A-54-119925,
Phenyldiamine derivatives described in Japanese Patent Publication No. 46-3712, Japanese Patent Publication No. 47-28336, publications, etc. (12) U.S. Patent No. 3567450, Japanese Patent Publication No. 49-3
No. 5702, West German Patent (DAS) No. 1110518,
U.S. Patent No. 3180703, U.S. Patent No. 324059
No. 7, U.S. Patent No. 3,658,520, U.S. Patent No. 423
No. 2103, U.S. Patent No. 4175961, U.S. Patent No. 4012376, JP 55-144250, JP 56-119132, JP 39-27577,
Arylamine derivatives described in Japanese Patent Publication No. 56-22437, gazettes, etc. (13) Amino-substituted chalcone derivatives described in U.S. Patent No. 3,526,501, (14) Described in U.S. Pat. No. 3,542,546, etc. (15) Oxazole derivatives described in US Pat. No. 3,257,203, etc., (16) Styryl anthracene derivatives described in JP-A-56-46234, etc., (17) JP-A-Sho 56-46234, etc. Fluorenone derivatives described in Publication No. 54-110837 etc., (18) U.S. Patent No. 3717462, JP-A-54-54
9143 (corresponding to U.S. Patent No. 415098), JP 55-52063, JP 55-52064, JP 55-46760, JP 55-85495, JP 57-11350 No., Japanese Patent Publication No. 57-14874
Vidrazone derivatives disclosed in Patent No. 9, Publication No. 1, etc.

Two or more of these photoconductive substances may be used in combination depending on the case.

Among these photoconductive materials are triarylamines such as poly-N-vinylcarbazole; tri-p-)lylamine and triphenylamine; Boarylmethane such as methane; and 3-(4
-dimethylaminophenyl)-1,5-diphenyl-2
-Unsaturated heterocycle-containing compounds represented by pyrazoline derivatives such as pyrazoline are preferably used.

The photoconductive composition of the present invention containing the polymethine dye of formula (1) of the present invention as a sensitizer can be obtained by dissolving these dyes, a photoconductive substance, and a binder resin in an organic solvent.

This can be applied and dried on a conductive support by a commonly used method such as spin coating, blade coating, knife coating, reverse roll coating, dip coating, rod bar coating or spray coating, and used as a photoreceptor. In addition to being usable as a photosensitive layer (photoconductive layer) in a single-stone type electrophotographic photosensitive material, it can also be used as a charge carrier generation layer in a functionally separated electrophotographic photosensitive material having two layers: a charge carrier generation layer and a charge carrier transport layer. It can be used as

The photoconductive composition of the present invention can also be used in photoelectrophoresis by producing particles from the organic solvent solution using a mini-spray device or the like, and dispersing the particles in an insulating solution. .

The photoconductive composition of the present invention can be applied as a photoconductive layer in the image pickup tube of a red-body or infrared-sensitive video camera, or over a one-dimensional or two-dimensional array of semiconductor circuits for known signal transfer or scanning. It can be used as a red- or infrared-sensitive photoconductive layer of a solid-state image element having a photosensitive layer (semiconductive layer).

When used as a normal electrophotographic photoreceptor in the present invention, the aggravating dye may be used according to a conventionally known method, such as a method in which the photoconductor is dispersed in a binder resin and then a dye solution is added. Alternatively, a method in which the photoconductor is placed in advance in a dye solution, the dye is adsorbed, and then dispersed in a binder resin is particularly convenient. The amount of sensitizing dye used in the present invention varies over a wide range depending on the degree of sensitization required. That is, it can be used in an amount of 0.0001 to 20.0 parts by weight per 100 parts by weight of the photoconductor, but preferably in a range of 0.001 to 1000 parts by weight.

The aggravating dye used in the present invention can be contained in the photosensitive layer singly or in combination of two or more.

Depending on the purpose, the sensitizing dye of the present invention may also be used with other conventionally known spectral sensitizing dyes (for example, rose bengal, eosin,
Needless to say, it can be used in combination with

In addition, acid anhydrides and the like are sometimes added to zinc oxide, which is one of the photoconductors, to promote spectral sensitization, but in the present invention, the stability of the sensitizing dye of the present invention is sufficient. It is advantageous in that various conventionally known additives for electrophotographic photosensitive layers can be used in combination.

As the binder that can be combined, all conventionally known binders can be used. Typical examples include vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, styrene-butyl methacrylate copolymer, polymethacrylate, polyacrylate, polyvinyl acetate, polyvinyl butyral, alkyd resin, silicone resin, and epoxy resin. , epoxy ester resin, polyester resin, etc.

It is also possible to combine it with an aqueous acrylic emulsion or an acrylic ester emulsion.

For examples of specific polymeric materials useful as binders, see Research Disclosure.
H Disclosure), Volume 109, Pages 61-67, under the title "Electrophotographic Elements, Materials and Methods".

In general, aggravating pigments are susceptible to oxidation, and therefore, it is desirable to avoid using them together with catalyst compounds that promote oxidation.

For example, among vinyl polymerization initiators, care must be taken when using peroxides such as benzoyl peroxide, and organic acid salts of noble metals that promote hardening of unsaturated fatty acids. Regarding this point, even the sensitizing dye used in the present invention requires the same level of consideration as conventional exacerbating dyes, but conventional polymethine dyes are not used in combination with these oxidation promoters. However, it also had the disadvantage that it disintegrated in a short period of time. However, if the dye of formula (1) of the present invention is used, its stability will be significantly improved.

Generally, the amount of binder present in the photoconductive compositions of the present invention can vary. Typically, useful amounts of binder range from about 10 to about 90% by weight, based on the total amount of the photoconductive material and binder mixture.

The electrophotographic photosensitive layer according to the present invention can be provided on a conventionally known support. Generally speaking, the support for the electrophotographic photosensitive layer is preferably electrically conductive, such as a metal plate or a plastic film provided with a conductive layer (for example, a thin film made of aluminum, palladium, indium oxide, tin oxide, or cuprous iodide). paper with layers), conductive treated paper, etc. are often used. Polymers containing quaternary ammonium salts (for example, polyvinylbenzyltrimethylammonium chloride, US Pat. No. 4,108,802) can be used as conductive treatment agents for paper.
No. 4118231; No. 4126467; No. 41
A polymer containing quaternary nitrogen in the main chain as described in No. 37217,
U.S. Patent No. 4,070,189; Japanese Patent Application Publication No. 54-20977
Quaternary salt polymer latex (described in sclosure #16258), polystyrene sulfonate salts, colloidal alumina, etc. are well known, and can usually be used in combination with polyvinyl alcohol, styrene-butadiene latex, gelatin, casein, etc. many.

The organic solvent used for dispersion is a volatile hydrocarbon solvent with a boiling point of 200°C or less, especially dichloromethane,
Preferred are halogenated hydrocarbons having 1 to 3 carbon atoms, such as chloroform, 1,2-dichloroethane, tetrachloroethane, dichloropropane or trichloroethane. Various solvents used in coating compositions and mixtures of the above solvents, such as other chlorobenzenes, aromatic hydrocarbons such as toluene, xylene or benzene, ketones such as acetone or 2-butanone, ethers such as tetrahydrofuran, and methylene chloride. is also available.

The solvent is added in an amount of 1 to 100 g, preferably 5 to 20 g, per 1 g of the total amount of dye, photoconductive material and other additives.

The coating thickness of the photoconductive composition of the present invention on a suitable support is:
Can vary widely. Typically, coatings can be applied within the range of about 10 microns to about 300 microns (before drying). The preferred range of coating thickness before drying is approximately 5
It was found to be in the range of 0 microns to about 150 microns. However, useful results can be obtained even outside this range. The dry thickness of this coating may range from about 1 micron to about 50 microns.

Furthermore, as another mode of use of the composition of the present invention, it is also possible to incorporate an exacerbating agent into particles used for photoelectrophoresis to obtain images by photoelectrophoresis. The particles used in the photoelectrophoresis method are produced using a mini-spray device from a solution consisting of a photoconductive substance such as the aforementioned poly-N-vinylcarbazole and the aggravating agent of the present invention. These particles can also be used in insulating liquids containing saturated hydrocarbons such as decane, dodecane, octane, paraffin, isooctane, etc.
Preferably Isopar E1 Isopar H1 Isopar G
(manufactured by Esso Chemical Co., Ltd., trade name) or the like to form a dispersion liquid, which is used for photoelectrophoresis. Isopar E, Isopar H, and
Isopar G is 99.9.9, respectively.
9.3 and 99.8% by weight of aromatic hydrocarbons, respectively. Contains 2% by weight. However, Isopar H contains 0.5% by weight or less of olefin. The boiling points of each are 115℃~142℃, 174
℃~189℃ and 158℃~177℃. The amount of particles in the dispersion is between 0.5 and 10% by weight, preferably between 1 and 3% by weight, based on the dispersion.

Regarding the photoelectrophoresis method and its equipment, see 45-2 Japanese Patent Publication.
No. 0640.

Necessary additives may be appropriately added to the photoconductive layer and particles to improve the properties of the photoconductive layer and particles.

In the photoelectrophoresis method described above, for example, an electrically insulating binder component can also be present in the photoconductive composition of the present invention. Preferred binders used in making the photoconductive compositions of the present invention are film-forming, hydrophobic polymeric binders with fairly high dielectric strength and good electrical insulation properties. A typical example of such a substance is as follows. Natural resins such as vinyl resins, gelatin, cellulose ester derivatives, cellulose nitrate; Polycondensates including polyesters and polycarbonates; Silicone resins; Alkyd resins including styrene-alkyd resins; Paraffin; and various mineral waxes. .

Generally, the amount of binder in the photoconductive compositions of the present invention can vary, and typically useful amounts of binder are from about 10 to about 90% by weight, based on the total amount of the photoconductor and binder mixture. is within the range of

When producing photoconductive particles, a charge control agent and a dispersion stabilizer may also be added, especially a copolymer of lauryl methacrylate and styrene (copolymerization ratio of 4 to 4), which has the functions of both charge control and dispersion stabilization. 2:1) or a copolymer of 2-ethylhexyl methacrylate and styrene (copolymerization ratio 4:2 to 1), etc. are advantageously used.

In addition to the above-mentioned dispersion stabilizers, the photoconductive compositions of the present invention generally contain optional additives such as chlorinated diphenyl, dimethyl phthalate, and epoxy resins (trade name Epicote) to improve flexibility and strength. It is also possible to add up to 60 parts by weight, preferably from 10 to 40 parts by weight, of the agent per 10 parts by weight of photoconductive material.

In addition, in order to improve the strength, JP-A-58-65438
No., JP-A-58-65439, JP-A-58-1022
No. 39, JP-A-58-102240, JP-A-58-1
Urea compounds, thiourea compounds, carbonylamine compounds, thiocarbonylamine compounds, which are respectively described in No. 07544 and JP-A-58-129434,
A chemical aggravating agent such as a sulfonylamine compound or a dicarbonylamine compound may also be added in an amount of 1 to 100 parts by weight, preferably 3 to 50 parts by weight, based on 100 parts by weight of the photoconductive material.

Examples 1 to 6 Poly-N-vinylcarbazole (trade name Rubican 170
．． 5 g (manufactured by BASF, 18.25°C, in THF), 35 ■ of dyes of specific examples of compounds shown in Table 1, 30 ■ of 3,3'-dinitrobenzanilide, and 26 ml of methylene chloride.
was dissolved in 12ml of ethylene chloride to prepare a photosensitive solution.

This photosensitive solution was applied to a conductive transparent support (a 100 μm polyethylene terephthalate support with a surface resistance of
0'Ω) to obtain an organic thin film having a photosensitive layer of about 4μ.

This organic thin film was heated to 400V by +5kV corona discharge.
The amount of exposure required to attenuate the potential to 1/2, that is, the half-reduction exposure i['A (erg/cd) was measured.

A gallium-aluminum-arsenic semiconductor laser (oscillation wavelength: 780 nm) was used as a light source.

The results are shown in Table 1.

Table 1 Example number Compound example E 'A [erg/c
a] 1 (2) 53. 2
2 (3) 49.63
(5) 46. 54
(9) 48.15
(13) 45.86 (1
9) 49.0 Examples 7 to 21 4.4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane 5g1 Bisphenol A polycarbonate (manufactured by GE, trade name Lexan 121) as an organic photoconductive substance ) 5g, 40cm of the dye of the specific compound example shown in Table 2 below, 0°2g of the anilide compound of the following structural formula as a chemical aggravator, and 30mj of methylene chloride! and 39mj of ethylene chloride! A photosensitive solution was prepared.

An organic thin film was produced in the same manner as in Example 1.

(Anilide compound) The photoreceptor produced in this way was
P-428 (manufactured by Kawaguchi Electric Co., Ltd.) was statically charged with corona at 15 KV, and after being held in a dark place for 30 seconds, the illuminance was 2J! It was exposed to UV light and the charging characteristics were examined. The charging characteristics include the initial charging potential (Vo) and the dark charge retention rate (DRR (%)), which indicates how much the potential after 30 seconds of dark decay is maintained with respect to the initial potential (Vo) Ez was measured in the same manner as in Example 1. The results are shown in Table 2.

It has been found that the dyes of the invention give favorable results.

Table 2 Example 22 As an organic photoconductive substance, 5 g of 4,4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane and 5 g of bisphenol A polycarbonate (manufactured by GE, trade name: Lexan 121), compound Dye 40 of specific example (1)
■ As a chemical sensitizer, an anilide compound 0 of the following structural formula
．． 2 g was dissolved in 39 ml of methylene chloride and 30 ml of ethylene chloride to prepare a photosensitive solution. An organic thin film was prepared in the same manner as in Example 1, and 8% was measured.
is 54,8 (erg/cd).

(Anilide compound) Examples 23 to 26 Particulate zinc oxide (average particle size 0.5 to 1 μm, manufactured by Sakai Chemical Co., Ltd. 5azex2000) 100 parts (all parts mean parts by weight), acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd.) Dianal LROO9Q) 40% by weight toluene solution 30
1.0 parts, 60 parts of toluene, and 8 parts of a methanol solution containing 1.0XIO-'Mol/J of dyes of specific compound examples shown in Table 3 below were mixed, and the mixture was heated in a porcelain ball mill for 2 hours. A dispersion was prepared by kneading.

This dispersion was coated on aluminum foil with a dry film thickness of approximately 8 cm.
An electrophotographic photoreceptor was prepared by applying the coating to a thickness of .mu.m and then drying it in a constant temperature bath at 50.degree. C. for 2 hours.

These photoreceptors were subjected to conditions similar to those described in Example 22.
Charging characteristics: Vo, DRR, 8% were measured. The results are shown in Table 3.

Table 3 Furthermore, when these photoreceptors were stored for one week at 50° C. and 80% RH, the charging characteristics were measured, and no significant difference was observed compared to before aging.

Example 27 and Comparative Example A 100 parts of fine particulate zinc oxide (average particle size 0.5 to 1 μm, 5azex'2000Q manufactured by Sakai Chemical Co., Ltd.) (all parts mean parts by weight), acrylic resin (Diamond manufactured by Mitsubishi Rayon Co., Ltd.) Narl LROO9■) 40% by weight toluene N? a
30 parts,) 60 parts of toluene, and the compound of the present invention (1
6) was mixed with 8 parts of a dye solution in methanol of 1.0xlO-''Mol/l and kneaded for 2 hours in a porcelain ball mill to prepare a dispersion.

This dispersion was applied to a dry film of approximately 8 μm on aluminum foil.
An electrophotographic photoreceptor (1) was prepared by coating the photoreceptor so as to have a coating temperature of m and then drying it in a constant temperature bath at 50° C. for 2 hours.

On the other hand, photoreceptor A was treated in exactly the same manner as above except that Comparative Compound A below was used instead of Compound (16) above.
was created.

(Comparative Compound A) Regarding the above two types of photoreceptors, spectral reflectance measurements were performed, and spectral photographs were taken by ordinary electrophotography using a liquid developer containing carbon black as a toner.

As a result of spectral reflectance measurements, the electrophotographic photosensitive layers containing compound (16) each showed a clear absorption maximum at a wavelength of 784 nm, but the electrophotographic photosensitive layers containing the comparative compound showed no absorption at wavelengths around 800 nm. did not show.

As a result of spectrophotography, it was found that the electrophotographic photosensitive layer containing compound (16) had a response due to spectral sensitization in the wavelength range corresponding to the above-mentioned spectral reflectance, in addition to the response in the inherent photosensitive range of ZnO around a wavelength of 380 nm. showed that.

On the other hand, in the electrophotographic photosensitive layer containing the comparative compound, no response other than the response in the specific photosensitive region of ZnO was observed. In other words, it was revealed that the electrophotographic photosensitive layer containing Comparative Compound A was not spectrally sensitized.

On the other hand, this photoreceptor was heated to 140 kW by corona discharge at 16 KV.
After being charged to 0V, the exposure amount required for the potential to attenuate to A, that is, the half-reduction exposure amount E% [erg/call] was measured.

A gallium-aluminum-arsenic semiconductor laser (oscillation wavelength: 780 nm) was used as a light source.

Electrophotographic photosensitive layer (1) of the present invention using compound (16)
The EV2 was 56 [erg/cd], and photoreceptor A using comparative compound A had no photosensitivity at all.

The above results were due to the fact that Comparative Compound A disappeared due to decomposition due to its instability, and such decomposition occurred when preparing a dispersion of the composition, in which zinc oxide, etc. and a pigment were added in advance, and then the compound A was placed in a ball mill. It is presumed that because the mixture was kneaded for 2 hours, the dye decomposed during that time. In contrast, it can be seen that the sensitizing dye of the present invention remains stable even under such processing conditions and exhibits a spectral sensitizing effect.

Example 28 and Comparative Example B Regarding the two types of compounds shown in Example 27, Example 27
An electrophotographic photosensitive layer was prepared using a method different from that of the previous method.

100 parts of fine particulate zinc oxide (average particle size 0.5 to 1 μm, 5azex2000 manufactured by Sakai Chemical Co., Ltd.), styrenated alkyd resin (Styresol #42 manufactured by Nippon Reichhold Co., Ltd.)
35 parts of a 25% by weight toluene solution of 5M) and 40 parts of toluene were mixed and kneaded in a porcelain ball mill for 2 hours to prepare a white dispersion. Polyisocyanate resin (Japan Reichhold Co., Ltd., Burnock D-7509) was added to this dispersion.
15 parts of a 25% by weight butyl acetate solution was added thereto and stirred thoroughly for 3 minutes.Furthermore, 10 parts each of the two types of methanol solutions shown in Example 27 were added to this dispersion and stirred well. These two types of dispersions were applied onto aluminum foil to a dry film thickness of 10 μm, and then placed in a constant temperature bath at 50°C for 15 minutes.
Two types of electrophotographic materials were obtained by drying for a period of time. Regarding the two types of materials obtained in this way, comparative compound A
Materials having an electrophotographic photosensitive layer containing Compound (16) and Compound (16) are named Comparative Sample B and Sample (2), respectively.

Spectral reflectance and spectral sensitivity by electrophotography were measured for these two types of samples. The absorbance at the maximum absorption wavelength in the spectral reflectance wavelength range of 7QQnm to 850nm was measured for the two types of samples immediately after production and after storage for one week under conditions of 50°C and 80%RH, and the absorbance after the accelerated test was calculated. The stability was estimated by using the value divided by the absorbance immediately after as the stability value. The closer the stability value is to 1, the more stable it is. Stability values are listed in Table 4. In this example, in order to prevent the decomposition of the dye during the preparation of the photosensitive layer, a method was adopted in which zinc oxide and resin were dispersed in advance and then the dye was added. Furthermore, in order to suppress the promotion of decomposition of the dye, a resin with an acid value of zero was used.

Comparative sample B in Table 4 has a maximum reflectance at a wavelength of 800n immediately after manufacture.
It was observed in two locations: around m (corresponding to the maximum absorption wavelength of the comparison compound) and around 380 nm (corresponding to the maximum absorption wavelength of ZnO), but after the accelerated test, the wavelength was 800 nm.
The maximum reflectance near the wavelength disappeared and the spectral absorbance curve became flat, and only the maximum reflectance near the wavelength of 380 nm was observed.

This fact indicates that the comparative compound in the electrophotographic photosensitive layer disappeared under accelerated test conditions.

On the other hand, when the spectral sensitization of sample (2) was measured after production and after the acceleration test in the same manner as in Example 27, a spectral sensitization ratio almost equivalent to the above stability value was obtained. That is, it became clear that sample (2) achieved the desired spectral sensitization to almost the same extent by compound (16) immediately after production and after accelerated testing.

Example 29 and Comparative Example C 100 parts of finely divided zinc oxide (average particle size 0.5 to 1 μm, 5azex20000 manufactured by Sakai Chemical Co., Ltd.), styrenated alkyd resin (Styresol #42 manufactured by Nippon Reichhold Co., Ltd.)
35 parts of a 25% toluene solution of No. 500) and 40 parts of toluene were mixed and kneaded in a porcelain ball mill for 2 hours to prepare a white dispersion. Add polyisocyanate resin (Barnock D-7500 manufactured by Nippon Reichhold Co., Ltd.) to this dispersion.
Add 15 parts of a 25% by weight butyl acetate solution of ) and stir well for 3 minutes, then add 10 parts each of a methanol solution of compound (31) or the following comparative compound BIXIO-II/L to this dispersion ( The two types of dispersions were applied onto aluminum foil to a dry film thickness of 10 μm, and then dried in a constant temperature bath at 5° C. for 15 hours to obtain two types of electrophotographic light-sensitive materials. Here, regarding the two types of materials, the material having an electrophotographic photosensitive layer containing Comparative Compound B and Compound (31) is named Comparative Sample C1 Sample (3), respectively.

(Comparative Compound B) Spectral reflectance and spectral sensitivity by electrophotography were measured for these two types of samples. For the two types of samples, the absorbance was measured immediately after production and at the maximum absorption wavelength in the wavelength range of 700 nm to 850 nm for spectral reflectance stored for one week under the conditions of 50 ° C and 80% RH, and the absorbance after the accelerated test was determined by the absorbance immediately after production. The stability was estimated using the divided value as the stability value. The closer the stability value is to 1, the more stable it is. Stability values are listed in Table 5.

In this example, in order to prevent the decomposition of the dye during the preparation of the photosensitive layer, a method was adopted in which zinc oxide and resin were dispersed in advance and then the dye was added. Furthermore, in order to suppress the promotion of decomposition of the dye, a resin with an acid value of zero was used.

Comparative sample C in Table 5 has a maximum reflectance at a wavelength of 800n immediately after manufacture.
It was observed in two locations: near the wavelength (corresponding to the maximum absorption wavelength of the comparison compound) and near the wavelength 380 nm (corresponding to the maximum absorption wavelength of ZnO), but after the accelerated test, the maximum reflectance around the wavelength of 800 nm disappeared. The spectral absorbance curve was flat, and only the maximum reflectance was observed around a wavelength of 380 nm.

This fact indicates that the comparative compound in the electrophotographic photosensitive layer disappeared under the accelerated test conditions.

On the other hand, for sample (3), when the spectral exacerbation degree immediately after production and after the accelerated test was measured in the same manner as in Example 27, a spectral exacerbation degree ratio almost equivalent to the above stability value was obtained. In other words, it was revealed that sample (3) achieved the desired spectral enhancement to almost the same extent by compound (31) immediately after production and after the accelerated test.

(Effects of the Invention) The photoconductive composition of the present invention is a highly sensitive photoreceptor that exhibits a sufficient exacerbation effect. In particular, the dye group of the present invention, which deteriorates in the long wavelength range of 750 nm or more, can have significantly higher sensitivity and greatly improved stability compared to conventional electrophotographic photoreceptors for lasers.

That is, the present invention overcomes the drawback that conventional electrophotographic photosensitive layers containing cyanine dyes cannot withstand long-term storage by using aggravating dyes having the above-described characteristic skeleton structure. In addition to reducing the decomposition of the exacerbating dye during the production of the photosensitive layer, the photosensitive layer can also be used under harsh test conditions such as 50°C and 80% R, H (relative humidity) compared to conventionally used cyanine dyes. It has a remarkable effect in that it shows very good stability. In particular, it has much greater stability than conventionally used red light or infrared aggravating dyes.

In the method of using the aggravating dye in the present invention, since the dye is highly stable, there is no need to set special dispersion mixing conditions or carefully select the timing of addition, which simplifies the process of manufacturing photosensitive materials. This has the advantage of stabilizing the quality and performance of photosensitive materials. Furthermore, when inorganic photoconductors such as zinc oxide, titanium oxide, zinc sulfide, and cadmium sulfide are used as photoconductors, if these photoconductors coexist with aggravating pigments, the conventionally known Sensitizing dyes tend to be easily decomposed, and in particular, when using red or infrared sensitizing dyes, restrictions such as carrying out photosensitive layer manufacturing work in a dark place are required. It is also a significant effect of the present invention that such restrictions are significantly relaxed.

Patent FFgi No. 260618 of 1985 2, Name of invention Photoconductive composition 6, Number of inventions increased by amendment 207, Pair of amendments *: “Detailed description of the invention” column of specification and amendment do.

Claims (1)

[Scope of Claims] A photoconductive composition containing a photoconductor, a sensitizing dye, and a binder resin, characterized in that the sensitizing dye is a compound represented by the following general formula [I]. Conductive composition. General formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the formula [I], n and m each represent 0, 1, 2, or 3. However, n and m never become 0 at the same time. p and q each represent 0 or 1. L represents a methyl group or a substituted methine group. R_1 represents a hydrogen atom or an alkyl group. R_2, R_3 and R_4 are each the same or different,
Each represents a hydrogen atom, an alkyl group, an alkoxy group, a hydroxy group, a substituted or unsubstituted amino group, or a halogen atom, and/or R_2 and R_3, R_3 and R_4, and/or R_2 and R_4 form a fused 6-membered ring. . Z_1 and Z_2 each represent an oxygen atom, a sulfur atom, a selenium atom, a tellurium atom, or ▲There are numerical formulas, chemical formulas, tables, etc.▼. However, at the same time, ▲mathematical formulas, chemical formulas, tables, etc.▼ cannot be expressed. Here, R_5 represents a substituted or unsubstituted alkyl group. Q_1 and Q_2 are each optionally substituted, pyran,
Necessary to form benzopyran, naphthopyran, thiopyran, benzothiopyran, naphthothiopyran, selenapyran, benzoselenapyran, naphthoselenapyran, ternapyran, benzoternapyran or naphthothernapyran or an optionally substituted heterocycle containing a nitrogen atom represents a group of atoms. However, Q_1 and Q_2 do not represent a nitrogen atom-containing heterocycle at the same time. Y_1, Y_2, Y_3 and Y_4 may be the same or different, and each represents a hydrogen atom, an aliphatic group or an aromatic group. X^■ represents an anion. r represents 1 or 2. However, when the dye forms an inner salt, r is 1.