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(11) | EP 0 685 759 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Photographic coating solution |
| (57) A photographic coating solution comprises gelatin and a compound represented by the
following Formula (I):
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided that when y is 1, an intramolecular salt is formed. |
FIELD OF THE INVENTION
[0001] The present invention relates to a photographic coating solution, and more particularly to a photographic coating solution wherein physical layer properties after being coated are improved due to a new hardener and no offensive odor caused by accumulation of a by-product in a photographic developing solution occurs.
BACKGROUND OF THE INVENTION
[0002] As a binder for a photographic coating solution, gelatin is commonly used. In order to adjust the degree of swelling of such gelatin layers and to enhance mechanical strength, hardening methods of gelatin using various compounds for hardening gelatin are known. For example, aldehyde compounds such as formaldehyde and glutaric aldehyde, compounds having reactive halogen described in USP. No. 3,288,775, compounds having a reactive ethylenically unsaturated compound as described in USP. No. 3,642,486 and Japanese Patent Publication No. 13563/1974, azilidine compounds described in USP. No. 3,017,280, epoxy compounds described in USP No. 3,091,537, halogencarboxylic aldehydes such as mucochlorolic acid, dioxanes such as dihydroxydioxane and dichlorodioxane and inorganic hardeners such as alum chromate and zirconium sulfate are cited.
[0003] However, the above-mentioned conventional gelatin hardeners, when used for a photographic light-sensitive material, have some shortcomings such as: hardening effect is insufficient, there is secular change of the degree of hardness called after-hardening due to slow hardening effect on gelatin, an adverse affect (increase of fogging and reduction of sensitivity) on the performance of photographic light-sensitive material, loss hardening effect due to other co-existing photographic additives and reducing the effects of other photographic additives (for example, a color developing agent).
[0004] As a hardener wherein hardening reaction on gelatin is relatively speedy and after-hardening is small, compounds having a dihydroquinoline skeleton described in Japanese Patent Publication Open to Public Inspection (hereinafter, referred to as Japanese Patent OPI Publication) No. 38540/1975, compounds having a phosphor-halogen linkage described in Japanese Patent OPI Publication No. 113929/1983, compounds having an N-sulfonyloxyimide group described in Japanese Patent OPI Publication No. 93470/1977, compounds having 2 or more N-acyloxyimino groups in a molecule described in Japanese Patent Publication No. 22089/1978, N-carbamoyl pyridium salts described in Japanese Patent Publication Nos. 12853/1981 and 32699/1983, 2-sulfonyloxy pyrydium salts described in Japanese Patent OPI Publication No. 110762/1981 and carbamoyl pyridinium compounds having an alkyl ester substituent on a pyridine ring described in Japanese Patent OPI Publication 12408/1994 are known.
[0005] Among the above, a hardener described in Japanese Patent Publication No. 32699/1983 has high hardening speed and high water-soluble property so that it does not necessitate a special organic solvent in coating gelatin layer. However, since the viscosity of the coating solution is enhanced during production so that coating becomes difficult or it becomes the cause of coating defects. In the case of a compound described in Japanese Patent Publication No. 12853/1981, an amine which is a by-product after hardening reaction is dissolved during photographic processing and accumulated in the processing solution so that offensive odor occurs. Thus, operation circumstance is damaged.
[0006] Accordingly, a gelatin hardener having minimal after-hardening, no coating defects and no offensive odor of amine which is a by-product accumulated in a developing solution has been demanded.
SUMMARY OF THE INVENTION
[0007] Accordingly, an first object of the present invention is to provide a photographic coating solution having high hardening reaction, no occurrence of coating defects and no offensive odor due to accumulation of by-product amine in a photographic processing solution.
DETAILED DESCRIPTION OF THE INVENTION
[0008] The present inventors studied diligently to discover that the above-mentioned object can be attained by the use of a compound represented by the following Formula 1.
① A photographic coating solution containing at least one kind of a compound represented
by the following Formula 1:
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group
or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted
or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino
group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided
that when y is 1, an intramolecular salt is formed.
② The photographic coating solution described in ① above wherein R₂ in the above-mentioned Formula 1 is a sulfo alkyl group or an acylamino group.
③ The photographic coating solution of ① above, wherein the substituted alkyl group represented by said R₂ represents -(CH₂)m-SO₃⁻, -(CH₂)p-CON(R₇)(R₈), -(CH₂)qN(R₉)(R₁₀) or -(CH₂)r-OR₁₁, wherein R₇ represents a hydrogen atom or a substituted or unsubstituted alkyl group or aryl group, R₈ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a group necessary to form a 5- or 6-membered alicyclic ring with R₇, R₉ represents a hydrogen atom, a substituted or unsubstituted alkyl group or -COR₄ in which R₄ represents a substituted or unsubstituted alkyl or alkoky group or -N(R₅) (R₆) in which R₅ and R₆ independently represent a substituted or unsubstituted alkyl group, R₁₀ and R₁₁ independently represent a hydrogen atom or a substituted or unsubstituted alkyl group, m represents an integer of 2 to 4, p represents an integer of 0 to 2, q represents an integer of 1 to 3 and r represents an integer of 2 to 3, the acylamino group represented by said R₂ represents -N(R₁₂)COR₁₃, the ureido group represented by said R₂ represents -N(R₁₂)CON(R₁₂)(R₁₃), and the alkoxycarbonylamino group represented by said R₂ represents -N(R₁₂)COOR₁₄, in which R₁₂ and R₁₃ independently represent a hydrogen atom or a substituted or unsubstituted alkyl group and R₁₄ represents a substituted or unsubstituted alkyl group.
④ The photographic coating solution of ① above, wherein said substituted alkyl group represented by said R₄, R₅, R₆, R₁₀ or R₁₁ is -(CH₂)n-SO₃⁻ in which n represents an integer of 1 to 3; and said substituted alkoxy group represented by said R₄ is -O-(CH₂)n-SO₃⁻ in which n represents an integer of 1 to 3.
⑤ The photographic coating solution described in ① above wherein, in the above-mentioned Formula (1), R₁ represents a hydrogen atom or an alkyl or alkoxy group which may have a substituent and R₂ represents -(-CH₂-)m-SO₃⁻ or -NR₃COR₄.
[0009] In item 3 above, the substituted or unsubstituted alkyl group represented by R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, R₁₃ or R₁₄, includes a methyl, ethyl, n-propyl, isopropyl, n-butyl, carboxymethyl, β-sulfoethyl, γ-sulfopropyl, β-aminoethyl, β-hydroxyethyl and β-trifluoromethylehtyl group; the substituted or unsubstituted alkoxy group represented by R₄ includes a methoxy, ethoxy, n-propoxy, β-sulfoethoxy, β-methylaminoethoxy and β-hydroxyethoxy group; and the substituted or unsubstituted aryl group represented by R₇ includes a phenyl, naphthyl, p-methoxyphenyl, o-methoxyphenyl, p-hydroxyphenyl, m-nitrophenyl, m-carboxyphenyl.
[0010] Hereunder, compounds used in the present invention will be exemplified. However, the present invention is not limited thereto.
[0011] These compounds can be synthesized easily in accordance with a method described in documents. As documents, "Chem. Ber", volume 40, page 1831 (1907) and J. Phys. Chem. volume 68, page 3149 are cited.
Synthesis of illustrated compound (4)
[0013] Ten g of 4-amino pyridine were dissolved in an acetonitrile (150ml) and heated to 60°C. To the resulting solution, an acetonitrile (40ml) solution in which 15g of chloroacetyl chloride was dissolved was dropped. Following this, the resulting mixture was stirred at 90°C for 12 hours under reflux. After the resulting mixture was chilled at room temperature, crystals were filtrated and dried so that 21.5 g of 4-chloroacetoamido pyridine was obtained.
[0014] An aqueous solution in which 21.5 g of 4-chloroacetoamidopyridine was dissolved in 200 ml of water was added dropwise to an aqueous solution in which 26 g of sodium sulfite was dissolved in 900 ml of water while heating and then stirred at 75°C for 12 hours. Thereafter, the resulting solution was mixed with 10 ml of concentrated hydrochloric acid and stirred at room temperature for one hour. The resulting crystals were filtrated, washed and dried. Thus, 20 g of 4-sulfoacetoamidopyridine were obtained.
[0015] In 50 ml of acetonitrile were dissolved while heating 20 g of 4-sulfoacetoamidopyridine and 15 g of tripropylamine. To the resulting solution were added dropwise 16 g of pyrrolidinocarbonylchloride and then stirred at 75°C for 12 hours. The resulting crystals were filtrated and dried. Thus, 14 g of hardener were obtained. The chemical structure of the hardener was identified by means of various spectrophotometric analysis and an elemental analysis.
Synthesis of illustrated compound (5)
[0016] In 60 ml of acetonitrile, 20 g of 4-pyridine ethane sulfonic acid and 17 g of tripropylamine were dissolved. To the resulting mixture, 16 g of pyrolidino carbonyl chloride was dropped. The mixture was stirred for 12 hours at room temperature. The resulting crystal was filtrated and dried to obtain 25.5 g of hardener (5). The chemical structure was identified by means of various spectrophotometric analyses and an elemental analysis.
[0017] These compounds are dissolved in water or a hydrophilic solvent such as methanol and ethanol, and then, added to the photographic coating solution of the present invention.
[0018] A gelatin layer formed by a coating solution of the present invention is a photographic structural layer containing gelatin such as a light-sensitive or non-sensitive silver halide emulsion layer, an intermediate layer, a filter layer, an anti-static layer, a development adjusting layer, a subbing layer, an anti-halation layer and a backing layer. The amount used of the compound represented by Formula 1 to the above-mentioned layer is not the same depending upon the kind of a compound or a coating solution. It is desirably 0.01 to 2.0 mmol and more desirably 0.03 to 1.0 mmol per 1 g of common dried gelatin.
[0019] A compound represented by the above-mentioned Formula 1 of the present invention may be combined with other conventional hardeners to be used. Practical examples of conventional hardener combined to be used include aldehyde type compounds such as formaline, glyoxal and succinic aldehyde, acid-releasing triazine compounds described in Japanese Patent Publication No. 6151/1972 including sodium 2,4-dichloro-6-hydroxytriazine or vinyl sulfonic compounds.
[0020] The silver halide grains used in the present invention are preferably ordinary crystal grains (including a cubic, octahedral and tetradecahedral) and more preferably tabular grains. The average grain size of silver halide grains is preferably 0.2 to 2.5 µm, and more preferably 0.4 to 2.0 µm.
[0021] The average value (referred to as the average aspect ratio) of grain diameter/thickness (referred to as the aspect ratio) in the tabular silver halide grains of the present invention is 3 or more, preferably 3 to 30, more preferably 3 to 20 and most preferably 3 to 10.
[0022] The average thickness of the tabular silver halide grains of the present invention is preferably 0.4 µm or less, more preferably 0.3 µm or less and most preferably 0.05 to 0.25 µm.
[0023] In the present invention, the diameter of silver halide grains is defined to be diameter of a circle having an area equivalent to the projected area of grains through observation of an electron microscopic photographic of a silver halide grain.
[0024] In the present invention, the thickness of silver halide grains is defined to be the minimum distance between two parallel planes constituting tabular silver halide grains. The thickness of tabular silver halide grains can be calculated by means of an electron microscopic photography provided with shadow of silver halide grains or an electron microscopic photography of the dislocation of a sample wherein a silver halide emulsion is coated on a support to be dried.
[0026] In the silver halide emulsion of the present invention, a ratio of tabular silver halide grains to the total silver halide grains is preferably 50% or more, more preferably 60% or more and most preferably 70% or more.
[0027] The tabular silver halide emulsion of the present invention is preferably mono-dispersed. Silver halide grains whose grain size is included in ± 20% of the average grain size are preferably 50 wt% or more. In addition, it is also desirable to mix mono-dispersed grains to use. In such an instance, the grain size distribution of grains in the light-sensitive material has two or more maximum values.
[0028] In the tabular silver halide emulsion of the present invention, any of halogen composition such as silver chloride, silver bromide, silver iodochloride, silver bromochloride, silver bromoiodide and silver bromochloroiodide may be used. In terms of high sensitivity, silver bromochloroiodide is preferable. The average silver iodide content is 0 to 4.0 mol% and preferably 0.2 to 3.0 mol%. The average silver chloride content is 0 to 5 mol%. In the tabular silver halide emulsion of the present invention, the halogen composition may be uniform or silver iodide may be localized in a grain, and one wherein silver iodide is localized in the central portion is preferably used.
[0029] For a production method of the tabular silver halide emulsion, it is possible to refer to Japanese Patent OPI Publication Nos. 113926/1983, 113927/1983, 113934/1983 and 1855/1987 and European Patent Nos. 219,849 and 219,850.
[0030] For a production method of a mono-dispersed tabular silver halide emulsion, it is possible to refer to Japanese Patent OPI Publication No. 6643/1986.
[0031] A tabular silver bromoiodide emulsion having high aspect ratio can be produced in a method wherein an aqueous gelatin solution whose pBr is kept at 2 or lower, an aqueous silver nitrate solution is added or an aqueous silver and an aqueous halogenized solution are added concurrently to create seed crystals, and then, grow them by means of a double jet method.
[0032] Size of a tabular silver halide grain can be controlled by temperature during formation of grains and by addition speed of silver salt and an aqueous halogenated solution.
[0033] The average silver iodide content of the tabular silver halide emulsion can be controlled by changing the composition of an aqueous halogenated substance added, i.e., the ratio between a bromide and a iodide.
[0034] In producing tabular silver halide grains, a silver halide solvent such as ammonia, thioether and thiourea can be used.
[0035] In order to remove a soluble salt from an emulsion, a water-washing methods such as a noodle water-washing method and a flocculation precipitation method are allowed to be used. As a desirable water-washing method, a method that uses an aromatic hydrocarbon aldehyde resin containing a sulfo group described in Japanese Patent OPI Publication No. 16086/1960 is cited. In addition, as a desirable desalting method, a method that uses illustrated coagulation polymers G-3 and G-8 described in Japanese Patent OPI Publication No. 7037/1990 is cited.
[0036] An emulsion used for the photographic coating solution of the present invention can be produced by a conventional method. For example, methods described in 1. Emulsion Preparation and types in Research Disclosure (RD) No. 17643 (December, 1978), pp. 22 to 23 and RD. No. 18716 (November, 1979), on page 648 can be used.
[0037] The emulsion used for the photographic coating solution of the present invention can be prepared by methods described in "The Theory of the Photographic Process" 4th Edition (1977), written by T.H. James, published by Macmillan Inc., on pp. 38 to 104, "Photographic Emulsion Chemistry" (1966) written by G.F. Dauffin, published by Focal Press Inc., "Chimie et Physique Photographique" written by P. Glafkides, published by Paul Montel (1967) and "Making and Coating Photographic Emulsion" written by V.L. Zelikman and others, published by Focal Press Inc. (1964).
[0038] Namely, under a solution condition of a neutral method, an acid method and an ammonia method, a mixing condition of an ordinary mixing method, a reverse mixing method, a double jet method and a controlled double jet method and a grain preparation condition of a conversion method and a core/shell method and their mixture can be selected for producing the emulsion. One of desirable embodiments of the present invention is a mono-dispersed emulsion wherein silver iodides are localized inside each grain.
[0039] To the emulsion of the present invention, various photographic additives can be added during a physical ripening step or before or after a chemical ripening step. As conventional additives, for example, compounds described in Research Disclosure Nos. 17643, 18716 (November, 1979) and 308119 (December, 1989) are cited. Kind of compound and place described in these three RDs are illustrated as follows:
[0040] As a support capable of being used in the light-sensitive material of the present invention, those described in the above-mentioned RD-17643, page 28 and RD-308119, page 1009 are cited.
[0041] As a suitable support, a plastic film is cited. On the surface of such a support, a subbing layer, corona discharge for UV irradiation may be provided for the better adhesion of coating layer.
[0042] The photographic coating solution wherein the present invention can be applied are used for a direct x-ray film, an indirect X-ray film, an X-ray reversal film for duplicating use, a film for a CT imager, a film for a laser imager, a graveur film for graphic arts, a line image film for graphic arts, a dot-photographing film for graphic arts, a contact-printing film for graphic arts, a black-and-white film for photography and a color film for photography.
[0043] A light-sensitive material formed by the use of the photographic coating solution of the present invention can be subjected to photographic processing by means of a conventional method. For example, various methods and various processing solutions described in Research Disclosure No. 17643 can be used.
EXAMPLE
[0044] The present invention will be explained referring to examples. It is obvious that the present invention is not limited thereto.
Example 1
[0045] While controlling at 60°C, pAg of 8.0 and pH of 2.0, mono-dispersed cubic crystal silver bromoiodide grains containing 2.0 mol% of silver iodide and having an average grain size of 0.20 µm were obtained by means of a double jet method.
[0046] A part of this emulsion was used as a seed, which was grown as follows. Namely, to a solution containing seed grains and gelatin, a solution containing an ammonia silver nitrate and potassium iodide were added at 40°C, pAg of 8.0 and pH of 9.5 by means of the double jet method so that the first layer containing 25 mol% of silver iodide was formed. Incidentally, the speed of addition was gradually accelerated as the grains grew.
[0047] The resulting emulsion was an octahedral mono-dispersed emulsion having an average grain size of 0.45 µm. To the emulsion as a core, an aqueous ammonia silver nitrate solution and an aqueous potassium bromide solution were added at pAg of 11.0 and pH of 9.0 by means of the double jet method so that the second layer was formed. The resulting emulsion was an octahedral mono-dispersed emulsion having an average grain size of 0.80 µm.
[0048] To the above-obtained emulsion, ammonium thiocyanate was added in an amount of 1.8 x 10⁻³ mol per mol of silver halide, and chloroaurate and sodium thiosulfate were added and subjected to chemical ripening. Succeedingly, an emulsion coating solution having the following composition was prepared.
(Composition of emulsion coating solution)
[0049] Per 1 liter of coating solution,
| Ossein gelatin processed with lime | 51 g |
| 5-methyl-1,3,4,7a-tetrazaindene-7-ol | 0.8 g |
| The above-mentioned silver halide emulsion | 0.6 mol |
| 1-phenyl-5-mercapto tetrazole | 0.015 g |
In addition, the following coating solution for a protective layer was prepared.
(Composition of coating solution for a protective layer)
[0051] On a polyethylene terephthalate support, the coating solutions were coated on a multilayer basis on both sides concurrently at a speed of 140 m/min. in such a manner that the amount of gelatin on the emulsion layer was 2.1 g/m² on one side and the amount of gelatin on the protective layer was 0.98 g/m² on one side.
[0052] The resulting sample film was stored at 23°C and 50%RH. The melting times of the film stored for 4 hours, 1 day, 3 days and 7 days after coating were measured by the following method. In a 1.5% aqueous sodium hydroxide solution kept at 60°C, samples were immersed. Time required for gelatin to start dissolving was defined to be "melting time". The results of measurement are shown in Table 1.
[0053] Hundred ml of XD-SR developing solution (produced by Konica Corporation) were kept at 35°C, in which 3 sheets of 10 x 12 inch size (0.2325 m²) of sample films stored under the above-mentioned condition were immersed for 15 seconds. Following this, offensive odor of the developing solution was evaluated by the following evaluation standard. Table 1 shows the results thereof.
A: In the same level as a developing solution (blank) wherein no film has been processed
B: There is offensive odor slightly more than that of the blank (can be put to practical use)
C: There is considerable offensive odor considerably more than that of the blank (cannot be put to practical use)
[0054] When hardener (D) is used, the viscosity of the coating solution for a protective layer was increased during coating so that coating became impossible. The coating solution gelled 10 minutes after addition of the hardener.
[0055] As is apparent from the results of Table 1, the hardening speed of samples using hardeners of the present invention (2), (5), (8) and (10) and comparative hardeners (D) and (E) is high. The melting time became stable after one day, and it is not raised thereafter. The hardening speed of samples using comparative hardeners (A), (B) and (C) is so low, and it can be understood that the melting time was raised after 3 day storage (after-hardening occurred). With regard to hardener (D), the hardening speed was too fast so that raising of viscosity of the coating solution occurred in a short time. Therefore, coating was impossible. The developing solution that processed a film using hardener (E) had very strong amine odor.
1. A photographic coating solution comprising gelatin and a compound represented by the
following Formula (I):
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided that when y is 1, an intramolecular salt is formed.
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided that when y is 1, an intramolecular salt is formed.
2. The photographic coating solution of claim 1, wherein R₂ in said Formula (1) represents
a sulfoalkyl group or a substituted or unsubstituted acylamino group.
3. The photographic coating solution of claim 1, wherein the substituted alkyl group
represented by said R₂ represents -(CH₂)m-SO₃-, -(CH₂)p-CON(R₇)(R₈), -(CH₂)q-N(R₉) (R₁₀) or -(CH₂)r-OR₁₁, wherein R₇ represents a hydrogen atom or a substituted or unsubstituted alkyl
group or aryl group, R₈ represents a hydrogen atom, a substituted or unsubstituted
alkyl group or a group necessary to form a 5- or 6-membered alicyclic ring with R₇,
R₉ represents a hydrogen atom, a substituted or unsubstituted alkyl group or -COR₄
in which R₄ represents a substituted or unsubstituted alkyl or alkoky group or -N(R₅)(R₆)
in which R₅ and R₆ independently represent a substituted or unsubstituted alkyl group,
R₁₀ and R₁₁ independently represent a hydrogen atom or a substituted or unsubstituted
alkyl group, m represents an integer of 2 to 4, p represents an integer of 0 to 2,
q represents an integer of 1 to 3 and r represents an integer of 2 to 3, the acylamino
group represented by said R₂ represents -N(R₁₂)COR₁₃, the ureido group represented
by said R₂ represents -N(R₁₂)CON(R₁₂) (R₁₃), and the alkoxycarbonylamino group represented
by said R₂ represents -N(R₁₂)COOR₁₄, in which R₁₂ and R₁₃ independently represent
a hydrogen atom or a substituted or unsubstituted alkyl group and R₁₄ represents a
substituted or unsubstituted alkyl group.
4. The photographic coating solution of claim 1, wherein said substituted alkyl group
represented by said R₄, R₅, R₆, R₁₀ or R₁₁ is -(CH₂)n-SO₃⁻ in which n represents an integer of 1 to 3; and said substituted alkoxy group
represented by said R₄ is -O-(CH₂)n-SO₃⁻ in which n represents an integer of 1 to 3.
5. The photographic coating solution of claim 1, wherein the solution contains said compound
in an amount of 0.01 to 2.0 millimole per 1g of gelatin.
6. The photographic coating solution of claim 1, wherein the solution contains said compound
in an amount of 0.03 to 1.0 millimole per 1g of gelatin.
7. A silver halide photographic light-sensitive material comprising a support and provided
thereon, a silver halide emulsion layer, wherein the material comprises gelatin and
a compound represented by the following Formula (I):
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided that when y is 1, an intramolecular salt is formed.
wherein R₁ represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted alkoxy group; R₂ represents a sulfo group, a substituted or unsubstituted alkyl, acyl group, acylamino, ureido group or alkoxycarbonylamino group or an amido group; X₁ represents an anion; and y represents 1 or 2, provided that when y is 1, an intramolecular salt is formed.