JPH0559291A - Cyanine dye - Google Patents

Abstract

PURPOSE:To provide the title dye which is novel and useful as a sensitizing dye to be contained in a zinc oxide photoreceptor by selecting a particular cyanine dye. CONSTITUTION:A cyanine dyestuff of formula I wherein R<1> is H, an alkyl, alkoxy, (substituted) phenyl or (substituted) phenoxy; R<2> is an alkyl, alkenyl or carboxyalkyl; X<-> is CH3(CH2)nSO3<-> or CH3(CH2)nCOO<-> (wherein n is 3 or more) or an anion of formula II (wherein R<3> is an alkyl); and m is 0-3. It is prepared by reacting an indolenine derivative of formula III with an iodide R<2>I to obtain a quaternary ammonium salt of the indolenine derivative given by formula IV and reacting the salt with the dianil hydrochloride of a dialdehyde given by formula V.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel cyanine dye.

[0002]

2. Description of the Related Art A so-called zinc oxide type electrophotographic photoreceptor is prepared by mixing zinc oxide with a sensitizing dye in a binder resin and forming a photosensitive layer on a conductive substrate. Has been formed. Such a zinc oxide type electrophotographic photoreceptor is widely used in laser printers and the like. Recently, a photoconductive toner (photosensitive toner) using zinc oxide has also been proposed. Such a photoconductive toner is also formed by mixing a binder resin with zinc oxide and a sensitizing dye, like the photosensitive layer.

The sensitizing dye contained in these photoconductors or photoconductive toners is used for use in the required visible light region and near infrared light region because zinc oxide alone absorbs only in the ultraviolet region. To be done. Such a sensitizing dye needs to be uniformly dispersed in the binder resin and strongly adsorb to zinc oxide. As the sensitizing dye, a cyanine dye represented by the following general formula (3) is often used.

[0004]

[Chemical 3]

(In the formula, Z is O, S, Se, NH, -CH.
R is an alkyl group, such as = CH-. Since such a cyanine dye is ionic, it has poor dispersibility or solubility in a non-polar solvent such as toluene, and therefore the dye is nonuniformly adsorbed on zinc oxide, and a sufficient sensitizing effect cannot be obtained. There was a problem.

The main object of the present invention is to solve the above technical problems and to provide a novel cyanine dye capable of improving the photosensitivity when used as a sensitizing dye for electrophotographic photoreceptors and photoconductive toners. Is to provide.

[0007]

Means and Actions for Solving the Problems As a result of intensive studies conducted by the present inventors to improve the dispersibility or solubility of a cyanine dye in a non-polar solvent, the present inventors have found that a counter ion species specific to the cyanine dye is The present invention has been completed by discovering new knowledge that the dispersibility or solubility is improved by introducing the.

That is, the cyanine dye of the present invention has the general formula (1):

[0009]

[Chemical 4]

[Wherein R ¹ is a hydrogen atom, an alkyl group,
An alkoxy group, a phenyl group which may have a substituent or a phenoxy group which may have a substituent, R ² is an alkyl group, an alkenyl group or a carboxyalkyl group,
X ^- is _{CH 3 (CH 2) n SO} 3 -, CH 3 (CH 2) n COO
^- or

[0011]

[Chemical 5]

(In the formula, n is an integer of 3 or more, R ³ is an alkyl group), and m is an integer of 0-3. ] Is represented. The present invention improves the solubility and dispersibility of a cyanine dye in a non-polar solvent by converting the conventional counter anion, iodide ion, into a specific anion X ⁻ , thereby uniformly dispersing the cyanine dye in zinc oxide. It is adsorbed on the surface of the glass and is capable of exhibiting a high sensitizing effect.

The alkyl group includes, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group, heptyl group, octyl group and the like. Is 1-8
And branched or straight chain alkyl groups. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a t-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group and an octyloxy group. Examples thereof include branched or straight-chain alkoxy groups having 1 to 8 carbon atoms.

Examples of the phenyl group which may have a substituent include, for example, a phenyl group, a 2-methylphenyl group, a 2,6-diethylphenyl group, a 2-t-butylphenyl group and a 2,6-dit- group. Examples thereof include a phenyl group which may have a branched or linear alkyl group having 1 to 6 carbon atoms such as a butylphenyl group, a 4-methylphenyl group, a 4-n-butylphenyl group and a 4-hexylphenyl group. ..

The phenoxy group which may have a substituent includes, for example, a phenoxy group, a 2-methylphenoxy group, a 2,6-diethylphenoxy group, a 2-t-butylphenoxy group and a 2,6-dit- group. Butylphenoxy group,
Examples thereof include a phenoxy group which may have a branched or linear alkyl group having 1 to 6 carbon atoms such as a 4-methylphenoxy group, a 4-n-butylphenoxy group and a 4-hexylphenoxy group.

Examples of the alkenyl group include a vinyl group,
Allyl group, 3-butenyl group, 1-methylallyl group, 2-
Examples thereof include alkenyl groups having 2 to 6 carbon atoms such as pentenyl and 2-hexenyl. As a carboxyalkyl group,
For example, carboxymethyl group, carboxyethyl group, 3-
Examples thereof include a carboxyalkyl group having an alkyl moiety having 1 to 6 carbon atoms such as a carboxypropyl group and a 4-carboxybutyl group.

As the substituent which may be substituted on the phenyl group or the phenoxy group, in addition to the above alkyl group, a halogen atom, an amino group, a hydroxyl group, an optionally esterified carboxyl group, a cyano group, an alkoxy group. Group, aryl group, alkenyl group and the like. Two or more substituents may be substituted. The anion X ^-
As CH ₃ (CH ₂ ) _n SO ₃ ^— or CH ₃ (CH ₂ ) _n
When COO ⁻ is used, n is 3 or more, preferably 3 to
A value of 9 is suitable.

It is preferable to use a relatively bulky substituent as the substituent R ¹ . This is to prevent the cyanine dyes, which are planar molecules, from molecularly associating with each other to reduce solubility and dispersibility. Such a substituent R ¹ has a carbon number of 4 such as n-butyl group and t-butyl group.
Examples thereof include the above-mentioned alkyl groups, phenyl groups and phenoxy groups which may have a substituent.

The cyanine dye represented by the general formula (1) can be produced, for example, by a series of reaction formulas shown below. Reaction formula 1:

[0020]

[Chemical 6]

(In the formula, R ¹ , R ² and m are the same as above, and q is an integer of 0 to 2.) This reaction formula 1 is for synthesizing a basic dye. That is, the formula
An aniline derivative represented by (a) is dispersed in an aqueous hydrochloric acid solution,
Add nitrous acid or sodium nitrite to diazotize,
Then, it is reduced with tin chloride to give a phenylhydrazine derivative.
Get (b). This phenylhydrazine derivative (b) is dissolved in a solvent such as acetic acid, and methyl isopropyl ketone is added to react with it to produce an indolenine derivative as an intermediate.
Get (c). The reaction is carried out by heating at a temperature of about 90 to 110 ° C. for about 1 to 2 hours.

Then, the obtained indolenine derivative (c)
Is dissolved in a solvent such as dimethyl ether, and the iodide (d) is reacted under reflux to react with the above indolenine derivative.
The quaternary ammonium salt (e) of (c) is obtained. A compound having an iodide ion as a counter anion by reacting this ammonium salt (e) with the dialdehyde dianyl hydrochloride (f).
Get (g). In the reaction, quaternary ammonium salt
(e) and dianyl hydrochloride of dialdehyde (f) were dissolved in acetic anhydride together with potassium acetate, and then dissolved at about 80 to 100 ° C. to about 0.1.
The reaction may be performed for 5 to 1 hour. As the dianyl hydrochloride (f) of the dialdehyde, for example, a dianyl hydrochloride having a carbon number corresponding to the above-mentioned number of m such as glutaconaldehyde dianyl hydrochloride is used. Reaction formula 2:

[0023]

[Chemical 7]

The compound obtained in the above reaction formula 1 (g), the counter anion in solvent X ^- by causing the silver salt AgX and anion exchange, to obtain a cyanine dye (1) of the present invention. The reaction is completed in about 5 to 6 hours at room temperature to 30 ° C. Instead of silver salt AgX, sodium salt NaX or potassium salt
It is also possible to use KX, but in certain solvents such as methanol it may not be possible to perform ion exchange at all,
Be careful.

In order to obtain the above-mentioned silver salt, the corresponding sodium salt or potassium salt, which is relatively easily available, is converted into a free acid by an ion exchange column, and then silver oxide is added. The cyanine dye of the present invention is useful as a sensitizing dye for electrophotographic photoreceptors and photoconductive toners, as well as a dye for laser, a dye for LB film, a dye for measuring membrane potential and the like.

[0026]

The present invention will be described in detail below with reference to examples. Example 1 1,3,3-trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium.n-decanesul
Synthesis of phonate

[0027]

[Chemical 8]

Silver n-decanesulfonate 0.153 g
(0.000466 mol) was dissolved in 15 ml of methanol, and 1,3,3-trimethyl-2- [7-iodide was added thereto.
(1,3,3-Trimethyl-2-indolinylidene)-
1,01,3,5-Heptatrienyl] -3H-indolium (0.201 g, 0.000376 mol) was added, and the mixture was stirred at room temperature overnight. The precipitated silver iodide was removed and the solvent was evaporated to dryness under reduced pressure. The residue was dissolved in chloroform, washed with water, and then dried under reduced pressure to give 0.178 g of the title compound (yield 76%).

The product has an IR spectrum of 1150 cm.
A peak derived from a sulfonate was found at ^-1 . The NMR spectrum (CDCl ₃ , TMS) of this product is shown in FIG.
Shown in. Example 2 1,3,3-trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium.n-butanesul
Synthesis of phonate The title compound was obtained in the same manner as in Example 1 except that silver n-butane sulfonate was used instead of silver n-decane sulfonate (yield 77%). Example 3 1,3,3-trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium.n-hexanes
Synthesis of Ruphonate The title compound was obtained in the same manner as in Example 1 except that silver n-hexanesulfonate was used in place of silver n-decanesulfonate (yield 77%). Example 4 1,3,3-trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium ・ n-octance
Synthesis of Ruphonate The title compound was obtained in the same manner as in Example 1 except that silver n-octanesulfonate was used instead of silver n- decanesulfonate (yield 77%).

For all the products of Examples 2 to 4, a peak derived from a sulfonate was observed at 1150 cm ^-1 in the IR spectrum, as in Example 1. Further, it was confirmed by the NMR spectrum that it was the title compound. Example 5 1,3,3-Trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium p-toluene
Synthesis of Ruphonate The title compound was obtained in the same manner as in Example 1 except that silver p-toluenesulfonate was used instead of silver n- decanesulfonate .

As with the product of Example 1, the product showed a peak at 1180 cm ^-1 in the IR spectrum, which was derived from the sulfonate. Further, it was confirmed by the NMR spectrum that it was the title compound. Example 6 1,3,3-trimethyl-2- [7- (1,3,3-to
Limethyl-2-indolinylidene) -1,3,5-hep
Tatrienyl] -3H-indolium / n-hexaneca
Synthesis of Rubonate The title compound was obtained in the same manner as in Example 1 except that silver n-hexanecarboxylate was used instead of silver n- decanesulfonate .

As for the product, as in Example 1, a peak derived from a carboxylic acid was found at 1710 cm ^-1 in the IR spectrum. Further, it was confirmed by the NMR spectrum that it was the title compound. Reference Example 1 5-t-butyl-1,3,3-trimethyl-2-iodide
[7- (5-t-butyl-1,3,3-trimethyl-2
-Indolinylidene) -1,3,5-heptatrieni
] -3H-Indolium Synthesis 2.1 g of p-t-butylphenylhydrazine hydrochloride
(0.00105 mol) was dispersed in 50 ml of acetic acid, 1.5 g (0.00174 mol) of methyl isopropyl ketone was added thereto, and the mixture was reacted at about 100 ° C. for 2 hours to obtain a uniform red reaction liquid. After the reaction, acetic acid was distilled off under reduced pressure. The residue was dissolved in 30 ml of methylene chloride to remove the insoluble matter, and then methylene chloride was distilled off under reduced pressure to give an oily compound, 5-t-butyl-2,3,3-trimethylindolenin 2. 14 g was obtained.

1.3 g (0.00604 mol) of 5-t-butyl-2,3,3-trimethylindolenine was dissolved in 30 ml of dimethyl ether, and 8.5 g (0.0602 mol) of methyl iodide was added thereto. In addition, the mixture was reacted under reflux for 12 hours. The precipitated crystals were filtered, washed with 50 ml of dimethyl ether and dried. Dissolve this in hot water,
After treated with activated carbon, recrystallized to give 5-t-butyl iodide-1,
2,3,3-Tetramethyl-3H-indolium 1.2
g was obtained.

This 5-t-butyl iodide-1,2,3,3
1 g of 3-tetramethyl-3H-indolium (0.00
28 mol) and glutaconaldehyde dianyl hydrochloride.
4 g (0.0014 mol) and potassium acetate 0.6 g
(0.0061 mol) and dissolved in 4 ml of acetic anhydride, about 1
The reaction was carried out at 00 ° C for about 1 hour. After the reaction, the reaction solution was poured into 50 ml of water in which 5 g of potassium iodide was dissolved and crystallized. The crystals were filtered, washed with water, and further washed with diethyl ether. The crystals were recrystallized from methanol to obtain 0.52 g of the title compound (yield 57%).

The product has an IR spectrum of 1300 cm ^-1.
A peak derived from the conjugated olefin was observed in the above. The NMR spectrum (CDCl ₃ , TMS) of this product is shown in FIG.
Shown in. The product decomposed at 185 ° C. Example 7 5-t-butyl-1,3,3-trimethyl-2- [7-
(5-t-butyl-1,3,3-trimethyl-2-yne
Dolinylidene) -1,3,5-heptatrienyl] -3
Synthesis of H-indolium n-decane sulfonate 1,3,3-trimethyl-2-iodide in Example 1
[7- (1,3,3-Trimethyl-2-indolinylidene) -1,3,5-heptatrienyl] -3H-indolium was replaced with 5-t-butyl iodide obtained in Reference Example 1. 1,3,3-Trimethyl-2- [7- (5-t-butyl-1,3,3-trimethyl-2-indolinylidene)
The title compound was obtained in the same manner as in Example 1 except that -1,3,5-heptatrienyl] -3H-indolium was used.

As for the product, as in Example 1, a peak derived from a sulfonate was found at 1150 cm ^-1 in the IR spectrum. Further, it was confirmed by the NMR spectrum that it was the title compound. Reference Example 2 5-phenoxy-1,3,3-trimethyl-2-iodide
[7- (5-phenoxy-1,3,3-trimethyl-2
-Indolinylidene) -1,3,5-heptatrieni
] -3H-Indolium Synthesis p-phenoxyphenylhydrazine hydrochloride 5.5 g
(0.0232 mol) was dispersed in 20 ml of acetic acid, 4.0 g (0.046 mol) of methyl isopropyl ketone was added, and the mixture was reacted at about 100 ° C. for 2 hours. After the reaction, acetic acid was distilled off under reduced pressure, the residue was dissolved in methylene chloride to remove the insoluble matter, and methylene chloride was distilled off to give an oily compound, 5-phenoxy-2,3,3-trimethylindolenin. 4.7 g was obtained (yield 80.5%).

4.2 g (0.017 mol) of this 5-phenoxy-2,3,3-trimethylindolenine was dissolved in a mixed solvent of 25 ml of hexane and 10 ml of diethyl ether, and 20 g of methyl iodide (0. 14 mol) was added, and the mixture was stirred at about 40 ° C. for 1 day. The precipitated crystals are filtered,
It was washed with hexane. The crystals were dissolved in water, treated with activated carbon, and then recrystallized to give 5-phenoxy-1,2-, 3,3-iodide.
-4.4 g of tetramethyl-3H-indolium was obtained (yield 67%).

This 5-iodinated iodopheno-1,2,3,3
2 g of 3-tetramethyl-3H-indolium (0.00
51 mol) and glutaconaldehyde dianyl hydrochloride.
72 g (0.00254 mol) and potassium acetate 1 g
(0.01 mol) and dissolve in 15 ml of acetic anhydride,
The reaction was carried out at 0 ° C for about 1 hour. After the reaction, the reaction solution was poured into 150 ml of water in which 10 g of potassium iodide was dissolved to crystallize. The crystals were filtered, washed with water, further washed with diethyl ether, and dried. The crystals were recrystallized from methanol to obtain 1.2 g of the title compound (yield 65%).

The product has an IR spectrum of 1300 cm ^-1.
A peak derived from the conjugated olefin was observed in the above. The NMR spectrum (CDCl ₃ , TMS) of this product is shown in FIG.
Shown in. The product decomposed at 190 ° C. Example 8 5-phenoxy-1,3,3-trimethyl-2- [7-
(5-phenoxy-1,3,3-trimethyl-2-yne
Dolinylidene) -1,3,5-heptatrienyl] -3
Synthesis of H-indolium n-decane sulfonate 1,3,3-trimethyl-2-iodide in Example 1
[7- (1,3,3-Trimethyl-2-indolinylidene) -1,3,5-heptatrienyl] -3H-indolium was replaced with 5-phenoxy-1, iodide obtained in Reference Example 2. 3,3-Trimethyl-2- [7- (5-phenoxy-1,3,3-trimethyl-2-indolinylidene)
The title compound was obtained in the same manner as in Example 1 except that -1,3,5-heptatrienyl] -3H-indolium was used.

As for the product, as in Example 1, a peak derived from a sulfonate was found at 1150 cm ^-1 in the IR spectrum. Further, it was confirmed by the NMR spectrum that it was the title compound. Reference Example 3 5-n-butyl-1,3,3-trimethyl-2-iodide
[7- (5-n-butyl-1,3,3-trimethyl-2
-Indolinylidene) -1,3,5-heptatrieni
] -3H-Indolium Synthesis pn-butylphenylhydrazine hydrochloride 4.7 g
(0.024 mol) was dispersed in 40 ml of acetic acid, 2.5 g (0.029 mol) of methyl isopropyl ketone was added thereto, and the mixture was reacted at about 100 ° C. for 2 hours. After the reaction, acetic acid was distilled off under reduced pressure, the residue was dissolved in diethyl ether, and the insoluble matter was removed. Diethyl ether was distilled off under reduced pressure to obtain 5.03 g of 5-n-butyl-2,3,3-trimethylindolenine as an oily compound (yield: about 100).
%).

5 g (0.023 mol) of this 5-n-butyl-2,3,3-trimethylindolenine was dissolved in diethyl ether, and 30 g (0.21) of methyl iodide was added thereto.
Mol) was added and reacted at room temperature for about 1 day. The precipitated crystals were filtered, washed with diethyl ether and dried under reduced pressure to give 5-n-butyl-1,2,3,3-tetramethyl-iodide.
6.2 g of 3H-indolium was obtained (yield 75%).

This 5-n-butyl iodide-1,2,3,
3-tetramethyl-3H-indolium 3 g (0.00
84 mol) and glutaconaldehyde dianyl hydrochloride 1.
2 g (0.0042 mol) and potassium acetate 1.8 g
(0.018 mol) and dissolve in 12 ml of acetic anhydride,
The reaction was carried out at 00 ° C for about 1 hour. After the reaction, the reaction solution was poured into 100 ml of water in which 5 g of potassium iodide was dissolved and crystallized. The crystals were filtered, washed with water, further washed with diethyl ether, and dried. The crystals were recrystallized from methanol to obtain 1.52 g of the title compound (yield 56%).

The product has an IR spectrum of 1300 cm ^-1.
A peak derived from the conjugated olefin was observed in the above. The NMR spectrum (CDCl ₃ , TMS) of this product is shown in FIG.
Shown in. The product decomposed at 146 ° C. Example 9 5-n-butyl-1,3,3-trimethyl-2- [7-
(5-n-butyl-1,3,3-trimethyl-2-yne
Dolinylidene) -1,3,5-heptatrienyl] -3
Synthesis of H-indolium n-decane sulfonate 1,3,3-trimethyl-2-iodide in Example 1
[7- (1,3,3-Trimethyl-2-indolinylidene) -1,3,5-heptatrienyl] -3H-indolium was replaced with 5-n-butyl iodide obtained in Reference Example 3. 1,3,3-Trimethyl-2- [7- (5-n-butyl-1,3,3-trimethyl-2-indolinylidene)
The title compound was obtained in the same manner as in Example 1 except that -1,3,5-heptatrienyl] -3H-indolium was used.

As for the product, as in Example 1, a peak derived from a sulfonate was found at 1150 cm ^-1 in the IR spectrum. Further, it was confirmed by the NMR spectrum that it was the title compound. (Evaluation test) 1. Solubility The solubility of each of the cyanine dyes obtained in Examples 1 to 9 was improved in a non-polar solvent as compared with a conventional cyanine dye having an iodine ion as a counter anion (hereinafter, referred to as Comparative Example). 2. Evaluation of Dye Properties Regarding the cyanine dyes obtained in Examples 1 to 4, ultraviolet rays (U
V) The maximum absorption wavelength λ _max and the molecular extinction coefficient ε of each cyanine dye were examined by the absorption spectrum. The results are shown in Table 1.

[0045]

[Table 1]

As is clear from Table 1, the cyanine dyes of Examples 1 to 4 have a molecular extinction coefficient ε as compared with that of the comparative example.
However, there was no change in the maximum absorption wavelength λ _max . From this, it is considered that the cyanine dyes of Examples 1 to 4 have the same characteristics as the dyes of the comparative example. 3. Preparation of Zinc Oxide Photoreceptor Thin Film Zinc oxide, a binder resin (styrene-acrylic copolymer) and the cyanine dye of Comparative Example were added to toluene (a small amount of methanol was added) at a weight ratio of 3: 1: 0.003. A zinc oxide photoconductor thin film for comparison was prepared by dissolving, dispersing, coating on a glass substrate and drying. On the other hand, the cyanine dye obtained in Example was blended in an equimolar amount with the cyanine dye contained in the comparative zinc oxide photoconductor thin film to prepare a zinc oxide photoconductor thin film. 4. Evaluation of sensitizing effect of cyanine dye The sensitizing effect of zinc oxide by the cyanine dye was evaluated by measuring the photocurrent value of the zinc oxide photoconductor thin film obtained as described above. That is, a comb-shaped gold electrode was vapor-deposited on the zinc oxide photoconductor thin film, set in a photocurrent measuring device, and the photocurrent value was measured after humidity adjustment. The result is shown in Figure 5.
Shown in.

From the results shown in FIG. 5, the cyanine dyes of Examples 1 to 4 all have a photoconductivity of about 10 as compared with the dyes of Comparative Examples.
It can be seen that it has improved 0 times.

[0048]

As described above, the cyanine dye of the present invention is
It is useful as a sensitizing dye in a zinc oxide type photoconductor, a photoconductive toner and the like to improve the sensitizing effect.

[Brief description of drawings]

FIG. 1 is a graph showing an NMR spectrum of the product obtained in Example 1.

2 is a graph showing an NMR spectrum of the product obtained in Reference Example 1. FIG.

FIG. 3 is a graph showing an NMR spectrum of the product obtained in Reference Example 2.

FIG. 4 is a graph showing an NMR spectrum of the product obtained in Reference Example 3.

FIG. 5 is a graph showing photocurrent measurement results of zinc oxide photoconductor thin films using the cyanine dyes obtained in Examples 1 to 4 and Comparative Example.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 5/09 101 8305-2H

Claims (1)

[Claims] 1. General formula (1): [Wherein R ¹ is a hydrogen atom, an alkyl group, an alkoxy group, a phenyl group which may have a substituent or a phenoxy group which may have a substituent, and R ² is an alkyl group,
Alkenyl group or carboxyalkyl group, X ^- is CH
_{3 (CH 2) n SO 3} -, CH 3 (CH 2) n COO - or ## STR2 ## (Wherein, n an integer of 3 or more, R ³ is an alkyl group.), M is an integer of 0 to 3. ] The cyanine dye represented by.