JPH01114839A - Silver halide photographic sensitive material - Google Patents

Abstract

PURPOSE:To improve the photographic sensitivity of the title material without increasing a fog in a photosensitive material by allowing a silver halide emulsion layer to chemical sensitization with a specified sulfur contg. compd. CONSTITUTION:The silver halide photographic sensitive material is provided with the silver halide emulsion layer which contains the sulfur contg. compd. shown by formula I wherein R<1>-R<4> are each hydrogen atom., alkyl or aryl group, etc., X is a protonic acid, (m) is a positive integer, (n) is 0 or a positive integer. Said compd. is exemplified by a compd. shown by formula II, etc. and is added to the emulsion at time time of starting chemical aging of the emulsion. And, an another chemical sensitizer such as a gold compd. etc. may be jointly used with the sulfur contg. compd. The photographic sensitive of said photographic sensitive material can be improved without increasing a fog, and the increase of the fog and the deterioration of the photographic sensitivity of said photosensitive material are reduced even preserved under high temp. and high humidity condition.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a silver halide photographic emulsion, and particularly to a silver halide photographic emulsion chemically sensitized with a sulfur-containing compound or the like.

[Background of the Invention] Silver halide emulsions used in photography inherently have low sensitivity, and various methods have been used to increase their photographic sensitivity.

For example, U.S. Patent Nos. 2,418,689 and 3,50
No. 1,313, West German Patent No. 1,422,869,
Japanese Patent Publication No. 49-20533 and the like describe a method using sulfur sensitization. This is an attempt to achieve high sensitivity by adding a small amount of a sulfur-containing compound (for example, hydrosulfide) to a silver halide emulsion to form silver sulfide nuclei.

Also, U.S. Patent No. 2,399,083, U.S. Pat.
It is also common to sensitize a silver halide emulsion by adding a reducing agent (reduction sensitization) or an alloy compound (gold sensitization) as described in No. 446.

Furthermore, “The Theory” by T, H, Ja1m13S
Of the Photographic Process” 4th edition (H
acnillan Co., 1977) describes a sensitization method that combines these methods.

Hydrogen sensitization using hydrogen gas is also a generally well-known sensitization method.

As evidenced by the recent commercialization of Konica Color G be.

In general, high sensitivity technology can also be applied to photographic image quality.

For example, if the same sensitivity can be achieved with silver halide grains having a smaller grain size, the graininess will be improved.

By reducing the amount of silver used, thinner films can be achieved and sharpness can also be improved. Naturally, it is also advantageous in terms of cost.

Therefore, various attempts have been made to obtain higher sensitivity, but the conventional sensitization methods have the disadvantage that significant fogging occurs when the number of compound layers is increased. .

Techniques using suppressants and the like are known to suppress this, but it is difficult to completely suppress fog.

Furthermore, if the amount of inhibitor is increased in accordance with the amount of sensitizing substance, the sensitizing effect will be significantly reduced.
No. 34 discloses a method of chemical sensitization using a thiourea derivative.

However, it cannot be said that these compounds have sufficiently achieved the target, and further improvements have been desired.

[Objects of the Invention] Therefore, the objects of the present invention are (1) to provide a silver halide photographic emulsion with increased photosensitivity without causing an increase in fog which is harmful to photographic properties.

(2) To provide a silver halide photographic emulsion that exhibits little increase in fog and decrease in sensitivity even when stored at high temperatures and high humidity.

There is a particular thing.

[Means for Achieving the Object] The above object is achieved by a silver halide photographic emulsion characterized by having a silver halide photographic emulsion layer containing a compound represented by the following general formula.

In the general formula, R1, R2, R3 and R4 each represent a hydrogen atom, an optionally substituted alkyl group, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group, a heterocyclic group, and an optionally substituted alkyl group as,
Unsubstituted alkyl groups (e.g. methyl group, ethyl group, n-propyl group, n-pentyl group, n-octyl group, 1so-
propyl group, 5ec-butyl group, t-butyl group, etc.), hydroxyalkyl group (e.g. hydroxyethyl group), alkoxyalkyl group (e.g. methoxyethyl group), hydroxyalkoxyalkyl group (e.g. hydroxyethoxyethyl group), cyanoalkyl group (eg, cyanethyl group), aminoalkyl group (eg, dimethylaminoethyl group), and the like.

Examples of the cycloalkyl group that may be substituted include a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group.

Examples of the alkenyl group that may be substituted include a vinyl group and an allyl group.

The optionally substituted aryl group includes a phenyl group (e.g., 2-chlorophenyl group, 4-nitrophenyl group, 4-nitrophenyl group,
-cyanophenyl group, 4-methoxyphenyl group, 4-(
N, N dimethylamino) phenyl group, 2゜4, G-trichlorophenyl group, 2,6-dibromophenyl group, 4-
(methylphenyl group, etc.), naphthyl group, etc.

: Optionally substituted aralkyl groups include benzyl group,
Examples include phenethyl group.

Examples of the heterocyclic group which may be substituted include a thienyl group, a furyl group, a pyrrolyl group, an imidazolyl group, a pyrazolyl group, a biverazilyl group, a morpholyl group, a piperidyl group, and a pyrrolidyl group.

X represents a protonic acid, and a wide range of organic acids and inorganic acids can be used as the protonic acid.

Preferred protonic acids include, for example, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, acetic acid, methanesulfonic acid, P-toluenesulfonic acid, viromellitic acid, trinitrophenol, and the like.

Specific examples of compounds of the present invention are shown below, but the present invention is not limited thereto.

Below margin <1) S NH H-N-CNH-CNHt C7HIS-NHCNHC-NHt (CH31a CHNHC-NHCNH2C2H=CH
-C1, -NH-C-NH-C-NH2C2H, -NH
-C-NH-C-NH-Ct H%NH* ・)(C
4 CI! Compounds of the invention are Chem, Ber, 63.208
(1930).

The compound of the present invention may be added to a silver halide photographic emulsion at any time during the emulsion manufacturing process, but generally,
It is desirable to add it at the beginning of chemical ripening after washing the emulsion with water.

The amount of the compound used in the present invention varies depending on the type of silver halide photographic emulsion, the type of compound used, etc., but is usually 3 x 10-' mol to 1 x 10-s per mol of silver halide. Preferably it is in moles.

The value of pAg (logarithm of the reciprocal of silver ion concentration) during chemical ripening is preferably 8.0 to 11.0.

Other chemical sensitizers can also be used in combination during chemical ripening. Chemical sensitizers that can be used in combination include, for example, U.S. Patent No. 2,399,083, U.S. Pat.
, 597,015, etc., U.S. Patent Nos. 2,487,850 and 2,518,6
No. 98, No. 2,521,925, No. 2,521,92
No. 6, No. 2,419,973, No. 2,694,637
No. 2,983,610, reducing substances such as amines and stannous salts;
No. 448.060, No. 2.566, No. 245, No. 2.5
Examples include salts of noble metals such as platinum, palladium, iridium, and rhodium, which are described in Patent No. 66, 263 and the like.

Sulfur sensitization using the compound of the present invention may be carried out in the presence of a silver halide solvent such as a thiocyanate (such as ammonium thiocyanate) or a tetrasubstituted thiourea (such as tetramethylurea).

In the present invention, reduction sensitization using a reducing substance, noble metal sensitization using gold or other noble metal compounds, etc. may be used in combination. Examples of reduction sensitizers include stannous salts, amines, and hydrazine. Derivatives, formamidine sulfinic acid, silane compounds, etc. can be used, and specific examples thereof can be found in U.S. Pat.
No. 74, No. 2,518,698, No. 2.983,609
No. 2,983,610, and No. 2,094,637. ,! In addition to gold complex salts, for metal sensitization,
Complex salts of metals in group I of the periodic table, such as platinum, iridium, and palladium, can be used;
, 399,083, 2.448.060, British Patent No. 818,061, etc.

In the photographic emulsion of the present invention, any of silver bromide, silver iodobromide, silver iodochlorobromide, silver chlorobromide and silver chloride may be used as the silver halide.

The average grain size of the silver halide grains in the photographic emulsion (grain diameter for spherical or approximately spherical grains, grain size for cubic grains, expressed as an average based on projected area) is not particularly limited. It is preferably 3μ or less.

The particle size distribution may be narrow or wide.

The silver halide grains in the photographic emulsion may have a regular crystal structure such as a cube or an octahedron, or an irregular crystal structure such as a spherical or plate-like structure.
It may have a crystalline form (egular) or a composite form of these crystalline forms.

It may also consist of a mixture of particles of various crystalline forms.

The silver halide grains may have different phases inside and on the surface, or may consist of a uniform phase.

The photographic emulsion of the present invention is P, Chim by GIafkide S.
ie atPhysigue Photography
que (published by Paul Mante1.

1961), by G.F. Uffin Photoq
rapic eluls-iofl chemrst
ry (The Focal Press, 19
66) V, L, 2eliknan et at
Author Making and Co'atin
.

Photoaraphic Eilulsion (T
Published by he Focal Press.

(1964) and others. That is, any of the acidic method, neutral method, ammonia method, etc. may be used, and the methods for reacting the soluble silver salt and soluble halogen salt include one-sided mixing method, simultaneous mixing method,
Any combination of these may be used.

It is also possible to use a method in which particles are formed in an excess of silver ions (so-called back-mixing method).

As one type of simultaneous mixing method, a method in which the pAg in the liquid phase in which silver halide is produced can be kept constant, that is, a so-called Chondrald double jet method can also be used.

According to this method, a silver halide emulsion with a regular crystal shape and a nearly uniform grain size can be obtained. 2 formed separately
A mixture of more than one type of silver halide emulsion may be used.

In the process of silver halide grain formation or physical ripening,
A cadmium salt, a zinc salt, a lead salt, a thallium salt, an iridium salt or a complex salt thereof, a rhodium salt or a complex salt thereof, an iron salt or an iron complex salt, etc. may be present.

The photographic emulsion of the present invention may be spectrally sensitized with methine dyes and others. Dyes used include cyanine dyes,
Included are merothea, nin 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. Namely, viroline nucleus, oxazoline nucleus, thiazoline nucleus, pyrrole nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus, imidazole nucleus, tetrazole nucleus, pyridine nucleus, etc.; a nucleus 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 Nuclei, quinoline nuclei, etc. can be applied. These nuclei may be substituted on carbon atoms.

Merocyanine dyes and complex merocyanine dyes have a ketomethylene structure as the nucleus, such as pyrazolin-5-one nucleus, thiohydantoin nucleus, and 2-thioxazolidine-
2,4-dione nucleus, thiazolidine-2,4-dione nucleus,
A 5- to 6-membered heterocyclic nucleus such as a rhodanine nucleus or a naobarbituric acid nucleus can be applied.

Useful sensitizing dyes include, for example, German Patent No. 929,080; US Pat. No. 2,231,658;
No. 48, No. 2.503.776, No. 2,519,00
No. 1, 2,912,329 September, 3,655,394
No. 3,05G, 959, No. 3,672, 897, No. 3,694,217, British Patent No. 1.242.5
No. 88, and was described in Japanese Patent Publication No. 14030/1973.

These sensitizing dyes may be used alone or in combination, and combinations of sensitizing dyes are often used particularly for the purpose of supersensitization.

Typical examples are U.S. Patent No. 2,688,545;
No. 977.229, No. 3,397,060, No. 3,5
No. 22,052, No. 3.527,641, No. 3. f3
No. 17,293, No. 3,628,964, No. 3.00
6.480, 3,679,428, 3,703
, No. 377, No. 3.769.301, No. 3,814,
No. 609, No. 3,837.862, British patent cylinder 1, 3
44,281, Japanese Patent Publication No. 43-4936, etc.

Along with the sensitizing dye, it is a dye that itself does not have a spectral sensitizing effect or a substance that does not substantially absorb visible light,
The emulsion may contain a substance exhibiting supersensitization. For example, an aminostilbene compound substituted with a nitrogen-containing heterocyclic group (
For example, US Pat. No. 2,933,390, No. 3,653.
No. 721), aromatic acid formaldehyde condensates (such as those described in U.S. Pat. No. 3,743,510), cadmium salts, azaindene compounds, etc., U.S. Pat. No. 3,615 , No. 613,
The combinations described in No. 3,615,641, No. 3,617,295, and No. 3,635,721 are particularly useful.

For the purpose of increasing sensitivity, increasing contrast, or accelerating development, the photographic emulsion of the present invention may contain, for example, polyalkylene oxide or its derivatives such as ethers, esters, and amines, thioether compounds, thiomorpholines, quaternary ammonium salt compounds, May contain urethane derivatives, urea derivatives, imidazole derivatives, 3-pyrazolidones, etc.6 For example, U.S. Pat.
No. 23,549, No. 2,716.062, No. 3,61
No. 7,280, No. 3,772,021, No. 3.808
, No. 003, etc. can be used.

The silver halide emulsion of the present invention contains an antifoggant (Anti
foggant) and stabilizer (5tabilizer)
may contain. As a compound, rAnti of Product Licensing Index, Volume 92, P107
f-00(lanlS and 5tabiliZQr
Those described in the SJ section can be used.

The silver halide emulsion may contain a developing agent. As a developing agent, Product Licensing Index, Volume 92 PIQ7-108 r Developinga
gents J can be used.

Silver halide can be dispersed in colloids that can be hardened by various organic or inorganic hardeners.

As a hardening agent, Product Licensing Index, Volume 92, P108 r Hardeners J
The one described in the section shall be used.

Silver halide emulsions may contain coating aids. As coating aids, those described in Product Licensing Index, Volume 92, P108, section rCoatingaids J may be used.

The silver halide emulsions of the invention can contain so-called color couplers. As a color coupler, Product Licensing Index, Volume 92, P11
0 rcOlor flat (those described in the section of 3rialS J can be used.) In the light-sensitive material produced according to the present invention, a filter dye or an irradiation prevention agent may be added to the photographic emulsion layer or other hydrophilic colloid layer. Examples of such dyes that may contain dyes for various other purposes include AbSOrbill, Product Licensing Index, Volume 92, P109.
The one described in Gand rt+terdyes J is used.

Silver halide photographic emulsions may also contain antistatic agents, plasticizers, matting agents, lubricants, ultraviolet absorbers, fluorescent brighteners, air antifoggants, and the like.

The silver halide emulsion used in the present invention includes, as a vehicle,
Product Licensing Index, Volume 92, P108, Vehicles section, (1971
(December 2013).

The silver halide emulsion is coated on a support along with other photographic layers if necessary. The application method is rCoa in 10 Duct Licensing Index, Volume 92, P109.
The methods described in the section ``Ting procedures'' can be used. Also, the support is Product Licensing Index, Volume 92, P108, '5up
Those described in the section ``ports J'' can be used.

The silver halide photographic emulsion of the present invention can be used for various purposes, such as the following.

Emulsions for color positives, emulsions for color paper, color negative emulsions, color reversal emulsions (which may or may not contain couplers), emulsions for photosensitive materials for plate making (e.g. lithium film, etc.), and emulsions for cathode ray tube displays. Emulsions used in light-sensitive materials, emulsions used in light-sensitive materials for X-ray recording (especially materials for direct and indirect photography using screens), colloid transfer process (Coll)
(e.g., described in U.S. Pat. No. 2,716.059)
The emulsion used in the silver salt diffusion transfer process (Silve
r 5alt diffusion transfer
process) (e.g. U.S. Pat. No. 2,352
, No. 014, No. 2.543.181, No. 3,020,
Emulsions used in color diffusion transfer processes (described in U.S. Patent Nos. 3,087,817, 3.185,567, and 2.983.606) No. 3,253,915, No. 3
, No. 227,550, No. 3,227,551, No. 3,
No. 227,552, No. 3,415. Ei No. 44, Ei No. 3,
No. 415,645, No. 3,415.646, Research Disclosure Vol. 151 No. 15162, P75
-87 (November 1916) etc.]
Emulsion used for dye transfer 10 cess (in
hibition transfer process
) (described in U.S. Pat. No. 2,882,156, etc.), silver dye bleaching method (Fr1ed
nan's “Old 5tOryOfColor photou
raphy” (^nerrcan photo
graprc Pudlishers Co, 1944
, especially Chapter 24) and “Br1tish Journal
of Photopg, rapy” VOL, 111
, p. 308-309 Apr, 7.1964], direct positive photosensitive materials (e.g., U.S. Pat. No. 2,491.815, U.S. Pat. No. 2,588.9)
No. 82, No. 3,367, 778, No. 3.501, 30
No. 0, No. 3,501,305, No. 3.672.900
No. 3,477.852, No. 2,717,833, No. 3,023,102, No. 3.05 (No. 1,395, No. 3.5<11,307, etc.) Emulsions used in photosensitive materials for heat development (for example, US Pat. No. 3.
152.904, 3.312.550, 3.1
48.122, British Patent No. 1.110,040), and photosensitive materials for physical development (for example, British Patent No. 920,277, British Patent No. 1,131.
238, etc.).

The emulsion of the present invention is particularly suitable for internal color in a multilayer structure, especially for reversal color or negative color, and for black-and-white negative (
It is advantageously used as an emulsion for black-and-white high-sensitivity negatives, micronegatives, etc.), an emulsion for color diffusion transfer processes, an emulsion for direct positive light-sensitive materials, and a core/shell type internal latent image type emulsion.

Exposure to obtain photographic images may be carried out using conventional methods, i.e. natural light (sunlight), tungsten lamps, fluorescent lamps, mercury lamps, xenon arc lamps, carbon arc lamps, xenon flash lamps, cathode ray tube flying spots, etc. Any of a wide variety of known light sources can be used. The exposure time ranges from 1/1000 second to 1
Not only exposure times of seconds, but also exposures shorter than 1/1000 seconds, such as 1/10 using xenon flash lamps or cathode ray tubes.
Exposures longer than 4 to 1/106 seconds can also be used.

If necessary, the spectral composition of the light used for exposure can be adjusted using a color filter. Laser light can also be used for exposure. Alternatively, exposure may be performed using light emitted from a fluorescent substance excited by electron beams, X-rays, γ-rays, α-rays, or the like.

Any known method can be used for photographic processing of the light-sensitive material produced using the present invention.

For example, the photo processing described in Product Licensing Index, Volume 92, P110, Processing J may be used.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

The compounds shown in Table 1 were added to a silver iodobromide gelatin emulsion (average grain size 1.0 μm) containing 13 mol% of silver iodide in 1. Next, a stabilizer (4-hydroxy-6-methyl-1,3,3
a, '7-titrazaindene), a surfactant and a hardening agent were added, and the mixture was coated on a cellulose triacetate film base and dried to obtain samples 1 to NQ9. These samples were exposed to light (1/100 second exposure) through a wedge,
Development was performed at 20° C. for 5 minutes using the following black and white developer.

Black and white developer composition Hydroquinone 9.0 g Phenidone 0.5 g Potassium bromide 4.0 g Sodium sulfite 80 g After adding water to 1.01, adjust the pH to 10 using KOH.
,0 to lIm.

After that, it was fixed, washed with water, and dried according to the usual method, and the photographic characteristics were measured.The results are shown in Table 1.
It is expressed as a relative value with the reciprocal of the exposure amount required to obtain an optical density of 1 and the sensitivity of the sample NQI as 100.

Margin table below - 1 Mine Soft Compound (A) Nag s20s ・5H
* From Table 1, it can be seen that the sample using the compound of the present invention achieves higher sensitivity with lower capri than the sample using the comparative compounds (^) and (B).

A silver iodobromide gelatin emulsion (average grain size 0.45 μm) containing 6 mol % of silver iodide was mixed with the compounds shown in Table 2 and 10 μm of potassium chloroaurate per mol of silver halide. was added and heated and aged at 55°C for 60 minutes. The obtained emulsion was coated on a base and dried in the same manner as in Example 1 with the addition of a stabilizer, a surfactant, and a hardening agent.
I got a 7.

A portion of these samples was stored for 3 days at a temperature of 50°C and a relative humidity of 80%, and another portion was stored for 3 days under normal indoor conditions, and then exposed to light in the same manner as in Example-1.・Perform 4 development processes, evaluate the photographic performance, and report the results in the table.
The sensitivity shown in 2 is the same sample as in Example-1! The relative sensitivity is expressed as 100, which is the sensitivity when left for 3 days under +Q10 indoor conditions.

As can be seen from Color Nutrient Table 2, samples using the compounds of the present invention not only have excellent fog-sensitivity relationships, but also suppress the increase in fog even when stored under high-temperature conditions. and the fluctuations in photographic performance are small.

A silver iodobromide gelatin emulsion (average grain size 0.8 μm) containing 6 mol % of silver iodide was added with the compounds shown in Table 3 and 6 mol of potassium chloride per mol of silver halide. The mixture was heated and aged at 50° C. for 70 minutes. Further, during ripening, the following green-sensitive sensitizing dye (a) was added to each emulsion in an amount of 3.8 x 10 -4 mol per mol of silver halide, and color sensitization was carried out in accordance with a conventional method.

The emulsion subjected to the above chemical sensitization and color sensitization contains 4-droxy-6-methyl-1,3,3a as a stabilizer.

7-chitrazaindene was added.

To 1.8 tons of the emulsion thus obtained, 1.9 tons of gelatin was added.
g, and the following magenta coupler [A) 0°20g,
A dispersion of 0.06 g of ditertiary nonylphenol in which colored magenta coupler (B) o, os was dissolved, a surfactant, and a hardening agent were added, and the mixture was coated and dried to prepare samples NQ18-25.

The following margin magenta coupler (A) Colored magenta coupler CB) Some of the samples were stored at a temperature of 50°C and relative humidity of 80% for 3 days, and some were stored under normal indoor conditions for 3 days, and then the color turned green. The photographic performance was evaluated by subjecting it to light exposure and the following development process.

Processing process: Color development 3 minutes 15 seconds bleaching
Wash with water for 6 minutes and 30 seconds
Fixed for 3 minutes and 15 seconds
Wash with water for 6 minutes and 30 seconds
3 minutes 15 seconds stabilization 1 minute 3
0 second drying The composition of the treatment liquid used in each treatment step is shown below.

[Color developer]

4-amino-3-methylto (β-droxyethyl)
- Aniline sulfate 4.57 anhydrous sodium sulfite 4.25° Hydroxylamine 1/2 [Acid acid 2.0g anhydrous potassium carbonate
37.5゜Sodium Bromide
1.3g Nitrilotri#, acid trisodium salt (monohydrate) 2.5g potassium hydroxide 1.0g Add water to make 1p.

[Bleach solution]

Ethylenediaminetetraacetic acid iron ammonium salt 100.0g Ethylenediaminetetraacetic acid diammonium salt 10.0g Ammonium bromide 150. Add Og glacial acetic acid 10.0 m f water to make 11, and adjust to pH 6.0 using aqueous ammonia.

[Fixer]

Ammonium 1000sulfate 175.0g Anhydrous sodium sulfite 8.6g Sodium metasulfite 2.3g Add water to make 11, and adjust to pH 6 using acetic acid.

[Stabilizing liquid]

Formalin (37% aqueous solution) 1.5m
(1 Konidax (manufactured by Konishiroku Photo Industry Co., Ltd.)7.
Add 5 m n water to make 11.

The measurement results of photographic performance are shown in Table-3, and the sensitivity is shown in Example-1.
The relative sensitivity is expressed as 100, which is the sensitivity when the same sample NQ18 was stored for 3 days under indoor conditions.

From Table 3 below, it can be seen that the compounds of the present invention have excellent fog sensitivity characteristics even when color sensitized emulsions are evaluated using a color development system. Furthermore, the results of samples stored at a temperature of 50° C. and a relative humidity of 80% indicate that the product has excellent storage stability under high temperature and high humidity conditions.

[Effects of the Invention] According to the present invention, photosensitivity can be increased without increasing fog, and even when stored under high temperature and high humidity, there is little increase in fog or decrease in photosensitivity. play.

Claims (1)

[Scope of Claims] A silver halide photographic material comprising a silver halide emulsion layer containing a compound represented by the following general formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R^1, R^2, R^3 and R^4 are each a hydrogen atom, an optionally substituted alkyl group, a cycloalkyl group, an alkenyl group, an aryl group It represents an aralkyl group or a heterocyclic group, and may be the same or different from each other. Furthermore, R^1 and R^2, R^3 and R^4 may each form a 5- or 6-membered ring. X represents protonic acid, m represents a positive integer, and n represents zero or a positive integer. ]