EP0405985A1

EP0405985A1 - Process for manufacturing silver halide photographic paper

Info

Publication number: EP0405985A1
Application number: EP90307102A
Authority: EP
Inventors: Isamu Morimoto; Kaoru Hattori; Koichi Ueda; Hiroyuki Ushiroyama
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 1989-06-28
Filing date: 1990-06-28
Publication date: 1991-01-02
Also published as: JPH0329942A

Abstract

A process for manufacturing a silver halide photographic paper is disclosed. The process comprises the steps of
preparing a silver halide emulsion,
preparing a hydrophilic colloid solution,
coating the silver halide emulsion on the surface paper support, and
coating the hydrophilic colloid solution on the same surface of the paper support,
wherein an emulsified dispersion of a specific high-boiling solvent containing an oil soluble fluorescent brightening agent dissolved therein is added into the silver halide emulsion or the hydrophilic colloid solution; and a calcium salt, in an amount so as to be not less than 1 mg per square meter after coating, is added into the silver halide emulsion or the hydrophilic colloid solution. A silver halide photographic paper manufactured by the process of the invention has a superior whiteness and may causes little aging deterioration of whiteness.

Description

FIELD OF THE INVENTION

The present invention relates to a process for manufacturing a silver halide photographic paper. More particularly, it relates to a process for manufacturing a silver halide photographic paper that has a superior whiteness and may cause little aging deterioration of the whiteness.

BACKGROUND OF THE INVENTION

In recent years, silver halide photographic papers have been more and more rapidly processed, and it is now prevailing to complete washing within 30 minutes.
However, the shorter the washing time becomes, the more insufficiently a spectral sensitizer dissolves out. This may bring about the problem that a white background of a photographic paper having been processed is colored and its whiteness is deteriorated. To cope with such a problem, it is an effective means to carry out fluorescent brightening to improve apparent whiteness.
As the fluorescent brightening, it is known to use a method in which a fluorescent brightening agent is added in a paper support or a polyethylene laminate layer thereof, and also a method in which a water-soluble fluorescent brightening agent or an oil-soluble fluorescent brightening agent is added in a silver halide emulsion layer or other photographic coating layers, or a method in which a fluorescent brightening agent is previously added in a developing solution. However, in the case of a polyethylene-laminated paper particularly suited for rapid processing, an attempt to incorporate a fluorescent brightening agent in the laminate layer may be accompanied with the disadvantage that the fluorescent brightening agent tends to be decomposed because of its poor thermal stability in the course of hot extrusion when the laminate layer is formed. An attempt to impart a fluorescent brightening agent in the course of developing may also cause a difficulty that the uniformity of finished goods can not be retained unless it is designed for the fluorescent brightening agent to be always kept in a given concentration throughout a run of processing. Thus, it is most preferred to previously add a fluorescent brightening agent in a photographic layer. In particular, among methods of adding a fluorescent brightening agent in a photographic layer, it is effective to add in a photographic layer an oil-soluble fluorescent brightening agent rather than a water-soluble one, from the viewpoint that the fluorescent brightening agent may not be flowed out during the processing. For such purpose, as disclosed, for example, in U.S. Patent No. 1,072,915, a method is known in which an emulsified dispersion obtained by dissolving a water-insoluble fluorescent brightening agent in an organic solvent is added in a gelatin layer.
There, however, is the problem that, even when the fluorescent brightening agent dissolved in an organic solvent and emulsifyingly dispersed is used, no sufficient whiteness can be obtained or, if obtained, the whiteness is deteriorated with time. Then, it has been noted as a great subject to select the organic solvent. Namely, even if a relatively good whiteness is attained after processing, some high-boiling organic solvents used have caused deterioration of the whiteness as time lapses after a sample has been coated and until processing therefor is carried out. If no such aging deterioration is caused, a high-boiling organic solvent has dissolved out in a little amount at the time of processing, resulting in a little poor whiteness after processing. These problems have been involved in the prior art.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a silver halide photographic paper hat has a superior whiteness and may cause little aging deterioration of the whiteness.
The above objects of the present invention can be achieved by a process for manufacturing a silver halide photographic paper, comprising the steps of
preparing a silver halide emulsion,
preparing a hydrophilic colloid solution,
coating the silver halide emulsion on the surface of a paper support, and
coating the hydrophilic colloid solution on the same surface of the paper support,
in which an emulsified dispersion of a high-boiling solvent represented by the following Formula I or II containing an oil-soluble fluorescent brightening agent dissolved therein is added into the silver halide emulsion or hydrophilic colloid solution; and a calcium salt in an amount so as to be not less than 1 mg per square meter after coating is added into the silver halide emulsion or hydrophilic colloid solution;

wherein R₁, R₂ and R₃ each represent an alkyl group having 1 to 3 carbon atoms, or a phenyl group, where R₁, R₂ and R₃ may be the same or different, and the phenyl group may be substituted with an alkyl group having 1 to 3 carbon atoms, provided that R₁, R₂ and R₃ are not alkyl-substituted phenyl groups at the same time; and R₄, R₅ and R₆ each represent an alkyl group having 1 to 4 carbon atoms.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described below in detail.
Specific exemplary compounds of the high-boiling organic solvent used in the present invention, represented by the above Formula I or II are shown below. The compounds in the present invention, however, are not limited to only these.

Exemplary Compounds:

The above exemplary compounds may be used alone or in combination of two or more kinds. The compound represented by Formula (I) and the compound reresented by Formula (II) may be used in combination of one or more kinds of each compound.
The above exemplary compounds can be readily synthesized by known methods.
The high-boiling organic solvent in the present invention may be used in any amount depending on the solubility of a fluorescent brightening agent used. It may preferably be in an amount not more than 50 % by weight based on the total amount of binder. An amount more than 50 % by weight may give the possibility of impairment of coating properties.
When the compounds represented by Formula I and II is used in combination, they can be used in any proportion.
The oil-soluble fluorescent brightening agent used in the present invention includes the compounds represented by the following Formulas III-a, III-b, III-c and III-d.
In the above Formulas III-a to III-d, Y₁ and Y₂ each represent an alkyl group; Z₁ and Z₂ each represent a hydrogen atom or an alkyl group; n represents 1 or 2; R₁′, R₂′, R₄′, and R₅′, each represent a halogen atom, an aryl group, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, an amino groupl a cyano group, a carboxyl group, an amido group, an ester group, an alkylcarbonyl group, an alkylsulfonyl or dialkylsulfonyl group, or a hydrogen atom.
R₆′ and R₇′ each represent a hydrogen atom, an alkyl group such as a methyl group or an ethyl group.
R₁₆′ represents a phenyl group, a halogen atom, or an alkyl-substituted phenyl group; and R₁₅′ represents an amino group or an organic primary or secondary amine.
Examples of the oil-soluble fluorescent brightening agent used in the present invention are the following exemplary compounds III-1 to III-15.
The oil-soluble fluorescent compounds of the present invention may be used alone or may be used in mixture of two or more kinds.
The fluorescent brightening agent may preferably be used so as to be present in an amount of from 1 to 200 mg/m² in a finished photographic paper. It may most preferably be used in an amount ranging from 5 to 50 mg/m².
The oil-soluble fluorescent brightening agent may be added by the same method as conventionally used for the addition of oil-soluble couplers or oil-soluble ultraviolet absorbents. Specifically stated, it is dissolved in a high-boiling organic solvent optionally together with a low-boiling organic solvent, the solution is mixed with an aqueous gelatin solution containing a surface active agent, the mixture is formed into an emulsified dispersion by means of an emulsifier such as a colloid mill, a homogenizer or an ultrasonic dispersion machine, and the resulting dispersion is added. The organic solvent may be used in its optimum proportion to the oil-soluble fluorescent brightening agent, which may be determined from the viewpoint of the solubility and concentration variation of the fluorescent brightening agent.
The emulsified dispersion of the fluorescent brightening agent used in the present invention may be added to one or both of the silver halide emulsion and the hydrophilic colloid solution to be coated on a support. From the viewpoint of prevention of so-called blooming, it may preferably be added to a silver halide emulsion or a hydrophilic colloid solution to be coated as near as possible to the support, e,g., a hydrophilic colloid layer such as an intermediate layer. The addition to the silver halide emulsion is most preferable.
The calcium salt used in the present invention specifically includes, for example, calcium chloride, calcium bromide, calcium iodide, calcium nitrate and calcium acetate. Among these, water-soluble calcium chloride or water-soluble calcium bromide is most preferred taking account of its influence on photographic performance. The calcium salt is required to be added in an amount of not less than 1 mg/m², and preferably from 3 to 20 mg/m².
In some instances, photographic gelatin commonly used originally contains calcium ions. The amount of the calcium salt to be added according to the present invention does not include the amount of such calcium ions as originally contained in gelatin.
In the present invention, the above calcium salt, when it is in a hydrated state, may be of any form that can be taken for various crystals.
The calcium salt used in the present invention may be added to a solution for any layer so so long as it is a photographic component layer on a support. It may particularly preferably be added to a silver halide emulsion.
As a binder or a protective colloid, used in the present invention, gelatin is usually used. Besides gelatin, it is also possible to use together with gelatin, for example, proteins such as gelatin derivativesl graft polymers of gelatin with other macromolecules, albumin, and casein; cellulose derivatives such as hydroxyethyl cellulose, and carboxymethyl cellulose; sugar derivatives such as agar-agar, sodium alginate, and starch derivatives; and various synthetic hydrophilic polymers such as homopolymers or copolymers of polyvinyl alcohol, poly-N-vinylpyrrolidone, polyacrylic acid, polyacrylamide, polyvinylimidazole, polyvinylpyrazole, etc.
The silver halide emulsion used in the present invention may be prepared by any of an acidic method, a neutral method and an ammoniacal method. As a form in which a soluble silver salt and a soluble halide are reacted, any of single-jet precipitation, double-jet precipitation (simultaneous mixing) and a combination of these may be used. It is also possible to use a method in which grains are formed in the presence of excess silver ions (i.e., so-called reverse precipitation). As one form of double-jet precipitation, it is possible to use a method in which the pAg in an aqueous phase for the formation of silver halide is controlled to a constant value, i.e., the controlled double-jet precipitation. This method enables preparation of a silver halide emulsion with a regular crystal form and almost uniform grain size. Grains may also be formed using the so-called silver halide solvent such as ammonia, a thioether or a thiol. So-called halogen substitution can also be used, which is a process comprising forming silver halide grains having a relatively low solubility as exemplified by silver chloride grains and silver bromide grains, followed by addition of a solution of a water-soluble silver halide that forms a silver halide having a relatively low solubility, as exemplified by a solution of silver bromide, silver iodide or the like, thereby forming grains.
The silver halide grains used in the present invention may have any composition such as silver chloride, silver bromide, silver chlorobromide, silver chloroiodobromide and silver iodobromide, which may be selected depending on the uses of various light-sensitive materials.
The silver halide grains may have a regular form such as cubes and octahedrons or may have a mixed crystal form. In order to obtain photographic characteristics with a high contrast or a high gradient, it is preferred to use grains having a relatively narrow grain size distribution and an average grain size ranging from 0.2 µm to 1.0 µm.
In the course of the formation of silver halide grains or the physical ripening, the silver halide emulsion used in the present invention may be in the presence of 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.
The silver halide emulsion used in the present invention may also be chemically sensitized using various sensitizers. For example, sulfur sensitizers as exemplified by sodium thiosulfate, thiourea and active gelatin, noble metal sensitizers as exemplified by a chloroaurate, gold thiocyanate, a platinum salt, a palladium salt, an iridium salt, a rhodium salt and a ruthenium salt, reducing sensitizers as exemplified by stannous chloride, thiourea dioxide and a hydrazine derivative, selenium sensitizers as disclosed in U.S. Patent No. 3,297,446, and polyalkylene polyamine compounds as disclosed in U.S. Patent No. 2,518,698 can be used alone or in combination.
When the calcium salt is added to the silver halide emulsion, it is preferable to add the calcium salt at a time during or after the chemical sensitization of the silver halide emulsion.
In the silver halide emulsion used in the present invention, various photographic additives can be added, as exemplified by optical sensitizers, stabilizers, antifoggants, hardening agents, surface active agents and color couplers.
The silver halide emulsion thus obtained by the above method may be coated on a paper support such as a baryta paper or a resin-coated paper. A photographic paper can be thus obtained. As to processing methods, the photographic paper can be processed by methods known in the present industrial field.
In regard to developing agents and developing methods, the developing agents as disclosed in T.H. James, The Theory of the Photographic Process, Fourth Edition, p.291-334 and Journal of the American Chemical Society, Vol. 73, p.3,100 (1951) can be effectively used in the present invention.

EXAMPLES

The present invention will be described below by giving Examples.

Example 1

i) Preparation of emulsified dispersion of fluorescent brightening agent:

Using exemplary compounds I-2 and II-1 as high-boiling organic solvents and also the following compounds (1) and (2) as comparative compounds, emulsified dispersions A, B, C and D were prepared, respectively. An emulsified dispersion E was further prepared using exemplary compounds I-2 and II-1 as high-boiling organic solvents in a proportion of I-2:II-1 = 1:1. Comparative compound (1)
The dispersions were each prepared in the following manner.
A solution obtained by mixing and dissolving 0.7 g of exemplary compound III-2 as an oil-soluble fluorescent brightening agent, 27 g of the high-boiling organic solvent and 10 mℓ of n-butanol as a low-boiling organic solvent were added in 220 mℓ of an aqueous gelatin solution containing sodium tripropylnaphthalenesulfonate. An emulsified dispersion was thus prepared using an ultrasonic dispersion machine.

ii) Preparation of emulsion layer coating solution:

A cubic silver halide emulsion having silver halide composition of 99 mol % of silver bromide and 1 mol % of silver iodide and having an average grain size of 0.6 µm was prepared. To the resulting emulsion, 150 mg/mol.Ag (per mol of silver) of a compound of the following structural formula (X) was added as a sensitizing dye, and then gold sensitization and sulfur sensitization were carried out, followed by addition of 100 mg/mol·Ag of a sensitizing dye of the following structural formula (Y). Next, a calcium salt was added as shown in Table 1, and also 2 g/mol·Ag of 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene as a stabilizer, 60 mg/mol·Ag of 1-phenyl-5-mercaptotetrazole as an antifoggant and 1 g/mol·Ag of sodium tripropylnaphthalenesulfonate as a coating aid were added. Subsequently, the fluorescent brightening agent dispersion prepared in the manner as the above i) was added in the combination as shown in Table 1, and 16 g/mol·Ag of an ethyl acrylate/methacrylic acid copolymer latex was added as an agent for improving physical properties of the layer, followed by further addition of 0.4 g/m² of compound (Z) as an anti-molding agent, 5 g/mol·Ag of a styrene/maleic anhydride copolymer as a thickening agent, and a 1:0.25 mol reaction product of tetrakis(vinylsulfonylmethyl) methane and taurine potassium salt as a hardening agent in an amount of 30 mg per gram of gelatin. The resulting solution was adjusted to pH 5.5 with citric acid. An emulsion layer coating solution was thus prepared.

iii) Preparation of protective layer coating solution:

In a gelatin binder, 70 mg/m² of polymethyl methacrylate with an average particle diameter of 7 µm as a matting agent, 14 mg/m² of sodium salt of 2-sulfo-bis(2-ethylhexyl) succinate as a coating aid, 35 mg/m² of the following compound (a) as a fluorine-containing surface active agent, 14 mg/m² of the following compound (b) as an anti-irradiation agent, 28 mg, per gram of gelatin, of formalin as a hardening agent, and also 1 mg/m² of 1-phenyl-5-mercaptotetrazole as an antifoggant were added. A protective layer coating solution was thus prepared.
The emulsion layer coating solution and protective layer coating solution thus prepared were coated in layers on a 110 µm thick polyethylene-coated paper provided with a hydrophilic colloid backing layer and a subbing layer. Immediately before coating (within 10 minutes), 0.7 g/mol·Ag of 1-phenyl-3-pyrazolidone formed into a mixed solution with 5 g/mol·Ag of the following compound (c) was also added to the emulsion layer coating solution.
The coating weight of Ag was 1.4 g/m², and the coating weight of gelatin was 2.1 g/m² on the emulsion layer and 1.7 g/m² on the protective layer.

Samples No. 1 to No. 21 obtained in this way were divided into two groups, one of which was stored for a week at 50°C and 40 % RH and the other of which was stored for a week at room temperature and normal humidity. Subsequently, the samples, which remained unexposed to light, were processed using a developing solution (I) having the following composition, under developing conditions of 38°C for 15 seconds. Fixing, washing and drying were also carried out in conventional manners.

Developing solution (I):
Pure water (ion-exchanged water)	about 800 mℓ
Potassium sulfite	60 g
Disodium ethylenediaminetetraacetate	2 g
Potassium hydroxide	10.5 g
5-Methylbenzotriazole	300 mg
Diethylene glycol	25 g
1-Phenyl-4,4-dimethyl-3-pyrazolidinone	300 mg
1-Phenyl-5-mercaptotetrazole	60 mg
Potassium bromide	3.5 g
Hydroquinone	20 g
Potassium carbonate	15 g
Made up to 1,000 mℓ by adding pure water (ion-exchanged water).

Next, fluorescent intensity was evaluated on the samples having been processed.
Reflection density of the processed samples was measured under illumination from a xenon lamp, using Type 607 Color Analyzer, manufactured by Hitachi Ltd, and thus the fluorescent intensity was evaluated as a relative value of a decrease in reflection density at 440 nm, caused by the addition of the fluorescent brightening agent.

Results obtained are shown in Table 1.

Table 1

		Calcium salt		Relative fluorescent intensity*
Sample No.	High-boiling organic solvent	Name	Amount	Storage at room temp. normal humidity	Storage at 50°C, 40 %RH	Remarks
			(mg/m²)
1	A	CaCl₂	4.0	100	98	Y
2	A	CaCl₂	7.0	101	99	Y
3	A	CaCl₂	20	99	97	Y
4	A	CaCl₂	30	98	88	Y
5	A	-	-	96	56	X
6	A	CaBr₂	0.5	99	79	X
7	A	CaBr₂	1.2	98	89	Y
8	A	CaBr₂	3.0	100	95	Y
9	A	CaBr₂	4.0	99	99	Y
10	B	CaCl₂	4.0	98	99	Y
11	B	CaBr₂	4.0	98	98	Y
12	B	-	-	97	52	X
13	C	CaCl₂	4.0	99	63	X
14	C	CaBr₂	4.0	99	68	X
15	C	-	-	98	62	X
16	D	CaCl₂	4.0	82	78	X
17	D	CaBr₂	4.0	80	77	X
18	D	-	-	77	75	X
19	E	CaCl₂	4.0	101	99	Y
20	E	CaBr₂	4.0	100	97	Y
21	E	-	-	97	60	X
X: Comparative Example; Y: Present Invention

* Relative value expressed by assuming as 100 the fluorescent intensity of Sample No. 1 after storage at room temperature and normal humidity.

As is evident from Table 1, the samples according to the present invention has retained a high relative fluorescent intensity even after storage for 7 days at 50°C and 40 % RH, showing the excellence of the present invention.
The present invention has made it possible to provide a silver halide photographic paper that has a superior whiteness and may cause little aging deterioration of the whiteness.

Claims

1. A process for manufacturing a silver halide photographic paper which comprises coating a silver halide emulsion on the surface of a paper support, and coating a hydrophilic colloid solution on the same surface of said paper support, such that an emulsified dispersion of a high-boiling solvent represented by the following formula I or II containing an oil soluble fluorescent brightening agent dissolved therein is incorporated into said silver halide emulsion or said hydrophilic colloid solution; and a calcium salt in an amount so as to be not less than 1 mg per square meter after coating is incorporated into said silver halide emulsion or said hydrophilic colloid solution.

where R₁, R₂ and R₃ each independently represents an alkyl group having 1 to 3 carbon atoms or a phenyl group which may be substituted with an alkyl group having 1 to 3 carbon atoms provided that R¹, R₂ and R₃ are not all alkyl substituted phenyl groups; and R₄, R₅ and R₆ each independently represents an alkyl group having 1 to 4 carbon atoms.

2. The process of claim 1, wherein said oil-soluble fluorescent brightening agent is represented by the following formula III-a, III-b, III-c or III-d

wherein Y₁ and Y₂ are each an alkyl group; Z₁ and Z₂ are each a hydrogen atom or an alkyl group; n is 1 or 2; R₁′, R₂′, R₄′, and R₅′ are each a halogen atom an aryl group, an alkyl group, an alkoxy group, aryloxy group, an hydroxyl group, an amino group, a carboxyl group, an amido group, an ester group, an alkylcarbonyl group, an alkyl sulfo group, dialkylsulfo group or a hydrogen atom; R₆′ and R₇′ are each a hydrogen atom, an alkyl group or a cyano group; R₁₆ is a phenyl group, halogen atom or an alkyl substituted phenyl group; and R₁₅′ is an amino group, an organic primary amino group or an organic secondary amino group.

3. The process of claim 1, wherein said emulsified dispersion is added into said silver halide emulsion or said hydrophilic colloid solution in an amount to be 1 mg to 200 mg per square meter after coating.

4. The process of claim 3, wherein said emulsified dispersion is added into said silver halide emulsion or said hydrophilic colloid solution in an amount to be 5 mg to 50 mg per square meter after coating.

5. The process of claim 1, wherein said calcium salt is calcium chloride or calcium bromide.

6. The process of claim 1, wherein the amount of said calcium salt is within the range of from 3 mg to 20 mg per square meter.

7. The process of claim 1, wherein said emulsified suspension is added into said silver halide emulsion.

8. The process of claim 1, wherein said calcium salt is added into said silver halide emulsion.

9. The process of claim 6, said calcium salt is added into said silver halde emulsion at a time during or after chemical sensitizastion of said silver halide emulsion.