JPH0327101B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a silver halide photographic light-sensitive material (hereinafter referred to as
(referred to as "photosensitive materials"),
In particular, it relates to photographic materials that have improved antistatic properties, roller marks, and residual color at the same time. (Prior art) Photographic materials generally consist of an electrically insulating support and a photographic layer, so they are subject to contact friction or peeling with surfaces of the same or different materials during the manufacturing process and during use. This often results in the accumulation of electrostatic charges. This accumulated electrostatic charge causes many problems, but
The most serious problem is that the photosensitive emulsion layer becomes sensitized due to the discharge of electrostatic charges accumulated before processing, resulting in dots or resin-like or feather-like streaks when the photographic film is processed. It is something that happens. This is what is called a static mark, and it significantly reduces the commercial value of the photographic film, or in some cases completely destroys it. For example, if it appears in medical or industrial X-ray film, it will be easily recognized that it will lead to a very dangerous judgment. This phenomenon becomes apparent only after development, and is one of the most troublesome problems. Further, these accumulated electrostatic charges may cause secondary failures such as dust adhesion to the film surface or uneven coating. As mentioned above, such electrostatic charges are often accumulated during the production and use of photographic materials. This occurs due to peeling between the support surface and the emulsion surface, etc. Or, it may occur due to contact peeling between the X-ray film and a mechanical part in an automatic photographing machine or a fluorescent intensifying screen. It can also occur due to contact with other packaging materials. Static marks on photographic materials induced by such electrostatic charge accumulation become more noticeable as the sensitivity of photographic materials increases and the processing speed increases. Particularly in recent years, static marks are more likely to occur due to the increased sensitivity of photographic materials and the increased exposure to harsh handling such as high-speed coating, high-speed photography, and high-speed automatic processing. There is. In order to eliminate these problems caused by static electricity, it is preferable to add an antistatic agent to the photographic material. However, the antistatic agents that can be used in photographic light-sensitive materials cannot be the same as those commonly used in other fields, and are subject to various restrictions specific to photographic light-sensitive materials. That is, in addition to having excellent antistatic properties, antistatic agents that can be used in photographic light-sensitive materials must not have any adverse effect on photographic properties such as sensitivity, fog, graininess, sharpness, etc. of photographic light-sensitive materials; It should not adversely affect the film strength of the photosensitive material (that is, it should not be easily damaged by friction or scratching), and it should not have an adverse effect on the adhesion resistance (i.e., the surface of the photographic material or the surface of other materials should not be affected adversely. Antistatic agents are required to be used in photographic materials, such as not causing the photographic materials to become easily pocked), not accelerating the fatigue of processing solutions for photographic materials, and not reducing the adhesive strength between the constituent layers of photographic materials. application is subject to numerous constraints. One way to eliminate the problems caused by static electricity is to increase the electrical conductivity of the surface of the photosensitive material so that the static charges can be dissipated in a short period of time before the accumulated charges are discharged. Therefore, methods have been considered to improve the conductivity of supports and various coated surface layers of photographic materials, including the use of various hygroscopic substances, water-soluble inorganic salts, certain surfactants, and polymers. It has been tried. For example, US Patent No. 2882157, US Patent No. 2972535,
No. 3062785, No. 3262807, No. 3514291, No. 3514291, No.
Polymers such as those described in US Pat. No. 3,615,531, US Pat.
No. 2982651, No. 3428456, No. 3457076, No.
Surfactants such as those described in US Pat. No. 3,454,625, US Pat.
Metal oxides, colloidal silica, etc., as described in No. 3062700, No. 3245833, No. 3525621, etc., are known. However, these materials exhibit specificity depending on the type of film support and photographic composition, giving good results for some film supports and photographic emulsions and other photographic components, but not for others. Vine film supports and photographic components offer no protection against static electricity, or
Although the antistatic properties are excellent, the sensitivity of the photographic emulsion
These substances may adversely affect photographic properties such as fog, graininess, and sharpness, or even if they have good antistatic properties immediately after production, their antistatic properties deteriorate over time. It has been extremely difficult to apply it to photographic materials. Nonionic surfactants having one polyoxyethylene chain in one molecule, as shown in British Patent No. 861134 and German Patent No. 1422809, are known to have excellent antistatic properties. Some of these nonionic surfactants having one polyoxyethylene chain in one molecule had the effect of suppressing changes in photographic properties due to the above-mentioned development processing conditions, but on the other hand, the following They also have several major drawbacks, which have been major obstacles to their use in photographic materials. These drawbacks greatly reduce sensitivity. In particular, when applied to X-ray sensitive materials, speckled fogs, so-called roller marks, occur after development using an automatic processor. In particular, when silver halide in an X-ray sensitive material is spectrally sensitized with a sensitizing dye, residual coloring of the dye tends to occur on the photosensitive surface after processing, so-called residual color. It is easy to understand that the commercial value of photographic materials having these drawbacks is significantly impaired. (Objective of the Invention) The first object of the present invention is to provide a photographic light-sensitive material that is well prevented from charging without adversely affecting photographic properties such as a decrease in sensitivity. A second object of the present invention is to provide a photographic material that is less likely to form roller marks when rapidly processed. A third object of the present invention is to provide a photographic material that does not leave behind color when the material containing a silver halide emulsion spectrally sensitized using a sensitizing dye is rapidly processed. be. (Structure of the Invention) As a result of intensive research to develop a photographic material that has good antistatic properties and photographic properties and is less likely to cause roller marks or residual color during rapid processing, we have found that the general formula [] or It has been surprisingly found that when a polyoxyethylene surfactant represented by [ ] and acid-treated gelatin are incorporated in a photographic material in combination, the above-mentioned problems can be solved at once and the above objects can be achieved. Ta. In the formula, R ₁ , R ₂ , R ₆ and R ₈ represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group or a halogen atom. R ₅ and R ₇ are alkyl groups, aryl groups,
Represents an alkoxy group or a halogen atom. or,
R ₅ and R ₆ or R ₇ and R ₈ may be linked to each other to form a ring. R ₃ and R ₄ represent a hydrogen atom, an alkyl group, an aryl group or an α-furyl group. R ₃ and R ₄ may be linked to each other to form a ring. n ₁ , n ₂ , n ₃
represents the average degree of polymerization of ethylene oxide and is a number from 2 to 50. In addition, m represents the average degree of polymerization, and is 2 to 50
is the number of In the general formula (), the substitutions R ₅ , R ₆ , R ₇ , and R ₈ on the left and right benzene rings may be symmetrical or asymmetrical. Preferred examples of the present invention are described below. _R1 , _R2 , _R5 , _R6 , _R7 , _R8 are preferably methyl, ethyl, i-propyl, t-butyl, t-amyl, t-hexyl, t-octyl, nonyl, decyl, dodecyl, Trichloromethyl, tribromomethyl, 1-phenylethyl, 2-phenyl-2
- Alkyl group having 1 to 20 carbon atoms such as propyl; aryl group such as phenyl group, p-chlorophenyl group,
-OR ₁₃ (herein, R ₁₃ represents an alkyl group or aryl group having 1 to 20 carbon atoms; the same applies hereinafter); a halogen atom such as a chlorine atom or _a bromine atom; R ₂ , R ₆ and R ₈ may be hydrogen atoms. Among these, R ₅ and R ₇ are preferably an alkyl group or a halogen atom,
R ₅ is particularly preferably a bulky t-butyl group,
These are tertiary alkyl groups such as t-amyl group and t-octyl group. Further, R ₅ and R ₆ or R ₇ and R ₈ may be linked to each other to form a ring, and examples of the ring include a naphthalene ring. R ₆ and R ₈ are particularly preferably hydrogen atoms. R ₃ and R ₄ are preferably a hydrogen atom, methyl group, ethyl group, n-propyl group, i-propyl group, n-heptyl group, 1-ethylamyl group, n-
Alkyl groups such as undecyl group, trichloromethyl group, tribromomethyl group; aryl groups such as phenyl group, naphthyl group, p-chlorophenyl group, p-methoxyphenyl group, m-nitrophenyl group, or α-furyl group. Furthermore, R ₃ and R ₄ may be linked to each other to form a ring, such as a dichlorohexyl ring. Among these, R ₃ and R ₄ are particularly preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an α-furyl group. n ₁ , n ₂ and n are particularly preferably numbers from 5 to 30. n and n may be the same or different. Among polyoxyethylene surfactants represented by the general formula [] or [], especially the general formula []
A polyoxyethylene surfactant having two polyoxyethylene chains in one molecule represented by is preferred. The polyoxyethylene surfactant represented by the general formula [] or [] is disclosed in, for example, US Pat.
No. 3850641, JP-A-54-89626, JP-A-57-
No. 109947, Patent Application No. 57-85764, No. 57-90909,
It can be synthesized by the method described in "New Surfactants" by Hiroshi Horiguchi (Sankyo Publishing, 1975). Next, examples of the polyoxyethylene surfactant of the present invention will be given. The acid-treated gelatin used in the present invention is a gelatin manufactured from collagen through treatment with hydrochloric acid, etc., and is different from alkali-treated gelatin, which is usually used in the photographic industry and involves treatment with lime, etc. . Details of the manufacturing method and properties of these gelatins can be found in Arthur Veis' ``The Macromolecules''.
Chemistry of Gelatin
Macromolecular Chemistry of Gelatin)” ~
It is described on pages 186 to 192 of the book published by Academic Press. The isoelectric point of acid-treated gelatin is 4.9~
9.0, preferably 6.0 to 7.5. The method for applying the polyoxyethylene surfactant of the present invention represented by the general formula [] or [] into the layer of a photographic material is as follows:
After dissolving in an organic solvent such as ethanol, acetone, or a mixed solvent of water and the above-mentioned organic solvent, the photosensitive emulsion layer, other non-photosensitive layers (e.g. bucking layer, antihalation layer, intermediate layer, The solution may be incorporated into a protective layer, etc., or may be sprayed or coated onto the surface of a support, or may be immersed in the solution and dried. Further, the decomposed gelatin of the present invention is preferably used in the protective layer and/or photosensitive emulsion layer of a photographic light-sensitive material in place of conventional alkali-processed gelatin. The polyoxyethylene surfactant of the present invention represented by the general formula [] or [] and the acid-treated gelatin of the present invention may be contained in the same layer in a photographic light-sensitive material, or may be contained in different layers. It's okay.
Moreover, these compounds of the present invention may be contained in multiple layers. The silver halide grains in the photographic emulsion used in the photographic light-sensitive material of the present invention may have a regular crystal structure such as a cube or an octahedron, or may have an irregular crystal structure such as a spherical shape or a plate shape. Irregulars can be things that have a crystalline form, or things that have a composite form of these crystalline forms. It may also consist of a mixture of particles of different crystalline forms. These photographic emulsions were published by P. Glafkides in Chimie et al.
Physique Photographique (published by Paul Montel)
1967), Photographic Emulsion by GFDuffin
Chemistry (The Focal Press, 1966), VL
Making and Coating by Zelilman et al
Photographic Emulsion (published by The Focal Press)
(1964) and others. That is, any of the acidic method, neutral method, ammonia method, etc. may be used, and the method for reacting the soluble silver salt and soluble halogen salt may be any one-sided mixing method, simultaneous mixing method, or a combination thereof. . As a binder for the photographic layer, proteins such as gelatin and casein; carboxymethyl cellulose,
Cellulose compounds such as hydroxyethyl cellulose; sugar derivatives such as agar, sodium alginate, starch derivatives; synthetic hydrophilic colloids such as polyvinyl alcohol, poly-N-vinylporolidone, polyacrylic acid copolymers, polyacrylamide or derivatives and moieties thereof A hydrolyzate or the like can also be used in combination. In addition, the photographic light-sensitive material of the present invention has a photographic constituent layer containing U.S. Pat.
The alkyl acrylate latex described in No. 5331 and the like can be included. Although the silver halide emulsion can be used as a so-called primitive emulsion without chemical sensitization, it is usually chemically sensitized. For chemical sensitization, Glafkides or
Zelikman et al.'s book or H. Frieser's Die
Grundlagen der Photographischen Prozesse
mit Silberhalogeniden
Akademische
Verlagsgesellscmaft, 1968) can be used. That is, a sulfur sensitization method using a compound containing sulfur that can react with silver ions or active gelatin, a reduction sensitization method using a reducing substance, a noble metal sensitization method using gold or other noble metal compounds, etc. are used alone or in combination. be able to. As the sulfur sensitizer, thiosulfates, thioureas, thiazoles, rhodanines, and other compounds can be used, and specific examples thereof include U.S. Pat.
Described in Nos. 2278947, 2728668, and 3656955. As the reduction sensitizer, stannous salts, amines, hydrazine derivatives, formamidine sulfinic acid, silane compounds, etc. can be used, and specific examples thereof include US Pat.
Described in Nos. 2518698, 2983609, 2983610, and 2694637. For noble metal sensitization, in addition to gold complex salts, complex salts of metals in the periodic table group such as platinum, iridium, and palladium can be used.
It is described in issues such as No. 618061. The light-sensitive material of the present invention can contain various compounds as antifoggants or stabilizers. Azoles such as benzothiazolium salts, nitroindazoles, triazoles, benzotriazoles, benzimidazoles (especially nitro- or halogen-substituted); heterocyclic mercapto compounds such as mercaptothiazoles, mercaptobenzothiazoles, mercapto. Benzimidazoles, mercaptothiadiazoles, mercaptotetrazoles (especially 1
-phenyl-5-mercaptotetrazole), mercaptopyridines; the above-mentioned heterocyclic mercapto compounds having a water-soluble group such as a carboxyl group or a sulfone group; thioketo compounds such as oxazolinthione; azaindenes such as tetraazaindene; -Hydroxy substitution (1,3,
Many compounds known as antifoggants or stabilizers can be added, such as (3a, 7) tetraazaindenes); benzenethiosulfonic acids; benzenesulfinic acid; etc. For more detailed examples of these and how to use them, see, for example, U.S. Pat. No. 3,954,474;
No. 3982947, No. 4021248, specifications or Tokkosho
The description in Publication No. 52-28660 can be referred to. Hardeners include mucochloric acid, mucobromic acid,
Mucofenoxychloric acid, mucophenoxybromic acid, formaldehyde, dimethylolurea, trimethylolmelamine, glyoxal, monomethylglyoxal, 2,3-dihydroxy-1,
Aldehyde compounds such as 4-dioxane, 2,3-dihydroxy-5-methyl-1,4-dioxane, succinaldehyde, 2,5-dimethoxytetrahydrofuran, and glutaraldehyde; divinylsulfone, methylene bismaleimide, 5-
Acetyl-1,3-diacryloyl-hexahydro-s-triazine, 1,3,5-triacryloyl-hexahydro-s-triazine, 1,3,
5-Trivinylsulfonyl-hexahydro-s-
Triazine bis(vinylsulfonylmethyl) ether, 1,3-bis(vinylsulfonylmethyl)
Active vinyl compounds such as propanol-2, bis(α-vinylsulfonylacetamido)ethane; 2,4-dichloro-6-hydroxy-s-triazine sodium salt, 2,4-dichloro-6
-methoxy-s-triazine, 2,4-dichloro-6-(4-sulfoanilino)-s-triazine.
Sodium salt, 2,4-dichloro-6-(2-sulfoethylamino)-s-triazine, N,N'-
Active halogen compounds such as bis(2-chloroethylcarbamyl)piperazine; bis(2,3-epoxypropyl)methylpropylammonium;
p-Toluenesulfonate, 1,4-bis(2',
3'-epoxypropyloxy)butane, 1,3,
5-triglycidyl isocyanurate, 1,3-
Epoxy compounds such as diglycidyl-5-(γ-acetoxy-β-oxypropyl)isocyanurate; 2,4,6-triethyleneimino-s-
triazine, 1,6-hexamethylene-N,
Ethyleneimine compounds such as N'-bisethyleneurea and bis-β-ethyleneiminoethylthioether; 1,2-di(methanesulfonoxy)ethane, 1,4-di(methanesulfonoxy)butane, 1,5- Examples include methanesulfonic acid ester compounds such as di(methanesulfoneoxy)pentane; furthermore, carbodiimide compounds; isoxazole compounds; and inorganic compounds such as chromium alum. The photographic emulsion layer or other constituent layers of the light-sensitive material of the present invention may contain various additives such as coating aids, antistatic properties, improving slipperiness, dispersing emulsions, preventing adhesion, and improving photographic properties (for example, accelerating development, increasing contrast, and sensitizing). For this purpose, surfactants other than those of the present invention may be included. For example, saponins (steroids), alkylene oxide derivatives (e.g. polyethylene glycol, polyethylene glycol/polypropylene glycol condensates, polyethylene glycol alkyl ethers or polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycols Nonionic interfaces such as alkylamines or amides, polyethylene oxide adducts of silicones), glycidol derivatives (e.g. alkenylsuccinic acid polyglycerides, alkylphenol polyglycerides), fatty acid esters of polyhydric alcohols, alkyl esters of sugars, etc. Activator: Alkyl carboxylate, alkyl sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, alkyl sulfate, alkyl phosphate, N-acyl-N-alkyl tauric acid, sulfosuccinic acid Anion interfaces containing acidic groups such as carboxy groups, sulfo groups, phospho groups, sulfate ester groups, phosphate ester groups, etc. such as esters, sulfoalkyl polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl phosphate esters, etc. Activators; amphoteric surfactants such as amino acids, aminoalkyl sulfonic acids, aminoalkyl sulfates or phosphates, alkyl betaines, and amine oxides; alkylamine salts, aliphatic or aromatic quaternary ammonium salts, pyridinium, Cationic surfactants such as heterocyclic quaternary ammonium salts such as imidazolium, and phosphonium or sulfonium salts containing aliphatic or heterocycles can be used. The photographic emulsions of this invention may be spectrally sensitized with methine dyes and others. The dyes used include
Included are cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes, and hemioxonol dyes. Particularly useful dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes. Any of the nuclei commonly used for cyanine dyes can be used as the basic heterocyclic nucleus for these dyes. That is, pyrroline nucleus, oxazoline nucleus, thiazoline nucleus, pyrrole nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus, imidazole nucleus, tetrazole nucleus, pyridine nucleus, etc.; nuclei in which an alicyclic hydrocarbon ring is fused to these nuclei; and these A nucleus in which an aromatic hydrocarbon ring is fused to the nucleus of Nucleus, quinoline nucleus, etc. can be applied. These nuclei may be substituted on carbon atoms. The merocyanine dye or composite merocyanine dye includes a nucleus having a ketomethylene structure such as a pyrazolin-5-one nucleus, a thiohydantoin nucleus, a 2-thioxazolidine-2,4-dione nucleus, a thiazolidine-2,4-dione nucleus, a rhodanine nucleus, A 5- to 6-membered heteroartic ring nucleus such as a thiobarbituric acid nucleus can be applied. The present invention will be illustrated below with reference to Examples, but the present invention is not limited thereto. Example 1 Tests for antistatic properties, photographic properties, and roller mark residual color (1) Sample preparation: A silver halide emulsion layer having the following composition was coated on a polyethylene terephthalate film support with a thickness of 180μ that had been undercoated. Further, a protective layer having the composition shown below was coated thereon and dried to prepare a black and white silver halide photographic material. For the protective layer, the nonionic surfactant of the present invention or the nonionic surfactant for comparison, the acid-treated gelatin of the present invention, and the lime-treated gelatin for comparison were used. (Emulsion layer) Thickness: Approximately 5μ Composition and coating amount Lime-treated gelatin 2.5g/m ² Silver iodobromide (silver iodide 1.5 mol%) 5g/m ² 1-phenyl-5-mercaptotetrazole
25mg/m ² (protective layer) Thickness: approximately 1μ Composition and coating amount Acid-treated gelatin or lime-treated gelatin of the present invention 1.7g/m ² 2,6-dichloro-6-hydroxy-1,
3,5-triazine sodium salt 10 mg/m ² Sodium N-oleyl-N-methyltaurate 7 mg/m ² Nonionic surfactant of the present invention or comparative nonionic surfactant 40 mg/m ² (2) Antistatic Judgment method: Antistatic ability was determined by measuring surface resistivity and static mark occurrence. Surface resistivity is measured by placing a test piece of the sample between 10 cm long brass electrodes with an electrode spacing of 0.14 cm (the part in contact with the test piece is made of stainless steel), and measuring the value for 1 minute using a Takeda Riken insulation meter TR8651. . In the static mark generation test, an unexposed photosensitive material is placed on a rubber sheet with the antistatic agent-containing surface facing downward, and then pressed from above with a rubber roller.
A method was used in which static marks were generated by peeling. Each measurement condition is surface resistivity: 25℃, 25%RH
The static mark generation test was performed at 25℃,
Perform at 25% RH. The humidity of the sample test piece was maintained under the above conditions all day and night. To evaluate the degree of static mark generation, each sample was incubated at 20°C using a developer with the following composition.
It was developed for 5 minutes. Developer composition N-methyl-p-aminophenol sulfate
4g Anhydrous sulfite 60g Hydroquinone 10g Soda carbonate (monohydrate) 53g Potassium bromide 25g Add water to make 1. The evaluation of static marks was based on the following five-level criteria. A: No static marks were observed. B: Some static marks occur. C: Significant static marks occur. D: Significant static marks occur. E: Static marks appear on the entire surface. (3) Photographic property testing method: The above sample was passed through Fujifilm filter SP-
After exposing to tungsten lamp light through 15, it was developed with a developer having the following composition (35℃, 30 seconds).
The photographic properties were examined after fixing and washing. Developer composition Warm water 800ml Sodium tetrapolyphosphate 2.0g Anhydrous sodium sulfite 50g Hydroquinone 10g Sodium carbonate (monohydrate) 40g 1-phenyl-3-pyrazolidone 0.3g Potassium bromide 2.0g Add water and mix to 1000ml (4) Roller Mark test method: The sample was exposed to light using a sensitometer and exposed to light for 90 seconds using Fuji
-Processed by Ray automatic machine RN. In this process, the sample is developed at 38°C for 20 seconds with a developer having the composition shown below. Developer formulation Potassium hydroxide 29g Glacial acetic acid 11g Potassium sulfite 44g Sodium bicarbonate 7.5g Boric acid 1g Diethylene glycol 29g Ethylenediaminetetraacetic acid 1.7g 5-Methylbenzotriazole 0.06g 5-nitroindazole 0.25g Hydroquinone 30g 1-phenyl-3-pyrazolidone 1.5g Sodium metabisulfite 12.6g Glutaraldehyde 1g Potassium bromide 6g Add water to make 1.0. (PH=10.25) After the treatment, roller marks formed on each sample were visually evaluated. Values A to E are given to each sample, where A indicates no roller marks and E indicates frequent roller marks. (5) Method for determining residual color: Samples that were developed in the same manner as above without being exposed to light were visually evaluated for residual color based on the residual dye. Give values A to E for each sample,
A indicates that there is no residual color at all, and E indicates that there is significant residual color. Table 1 shows the test results of (2) to (5) above.

[Table] As is clear from Table 1, the photographic material containing the polyoxyethylene surfactant represented by the general formula [] or [] of the present invention and the acid-treated gelatin of the present invention has no static marks. In addition, there is almost no decrease in photographic sensitivity, and roller marks and residual color are also good. In particular, the compound example represented by the general formula [] is better than the compound example-3 and -7 represented by the general formula [].
1, -4, and -19 show generally better performance. Example 2 A black and white silver halide photosensitive material was prepared in the same manner as in Example 1 except that only the gelatin used in the emulsion layer was changed. Similar to Example 1, the results are shown in Table 2.

【table】

[Table] As is clear from Table 2, the combination of the acid-treated gelatin of the present invention applied to the protective layer or emulsion layer and the polyoxyethylene surfactant of the present invention provides excellent antistatic performance. In addition, it is possible to provide a photosensitive material that is free from roller marks and residual color.

Claims (1)

[Scope of Claims] 1. In a photographic light-sensitive material having at least one photosensitive silver halide emulsion layer on a support, the photosensitive silver halide emulsion layer or other hydrophilic colloid layer has the following general formula [] or A silver halide photographic material comprising a polyoxyethylene surfactant represented by [ ] and acid-treated gelatin. In the formula, R ₁ , R ₂ , R ₆ and R ₈ represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, or a halogen atom. R ₅ and R ₇ represent an alkyl group, an aryl group, an alkoxy group, or a halogen atom. Furthermore, R ₅ and R ₆ or R ₇ and R ₈ may be linked to each other to form a ring. R ₃ and R ₄ represent a hydrogen atom, an alkyl group, an aryl group or an α-furyl group.
R ₃ and R ₄ may be linked to each other to form a ring.
n ₁ , n ₂ , n ₃ represent the average degree of polymerization of ethylene oxide, and are numbers from 2 to 50. Further, m represents the average degree of polymerization and is a number from 2 to 50. In the general formula [], the substituents R ₅ , R ₆ , R ₇ , and R ₈ on the left and right benzene rings may be symmetrical or asymmetrical.