GB2243924A - Silver halide photographic material - Google Patents

Abstract

A variable contrast silver halide photographic material comprises a support and a silver halide emulsion layer with two components (A) and (B): (A) a silver halide emulsion which is spectrally sensitized with a sensitizing dye of formula (l) containing a plurality of silver halides having different amounts of the dye and (B) a silver halide emulsion which is not spectrally sensitized or, if sensitized, has a spectral sensitivity maximum at a shorter wavelength than that of silver halide (A): <IMAGE> wherein R1 and R2 are alkyl, alkenyl, or aryl, L, L1 and L2 each represent CH or CR3 in which R3 is lower alkyl or aryl, Z1 is the atoms necessary to form an aryl- or aralkyl-benzoxazole ring or a napthoxazole ring, Z2 is the atoms necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring, X<-> represents an anion, I is 1 or 2, a is 0 or 1, and n is 0, 1 or 2.

Description

VER HALIDE PHOTOGRAPHIC MATERIAL BACKGROUND OF THE INVENTION The present invention relates to so-called variable contrast photographic photosensitive material from which gradation of various different tones can be produced using especially a filter.

In general, with reference to black and white photographic papers, those which are different in gradation of from the grade No. 1 to the grade No. 5 are separately produced and sold depending on gradation of negatives to be contact printed or enlargement printed.

However, for users thereof, photographic papers of such grade as of less frequency in use must also be always stocked and this is inconvenient for the users.

As an approach to solve the problem, there has been proposed and put to practical use a variable contrast photographic paper of so-called auxiliary exposure method according to which gradation can be varied by applying auxiliary exposure before and after the main exposure.

However, the photographic paper of this type cannot provide preferred variation of gradation and satisfactory finishing of photographic paper cannot be attained. As a more superior one, a variable contrast photographic paper has been known by which various gradation can be obtained in one photographic paper by changing filters. However, the variable contrast photographic paper of this type is produced by mixing a spectrally sensitized silver halide with a silver halide which is not spectrally sensitized to this sensitization region and coating the mixture on a base. Therefore, desorption or exchanging adsorption of the sensitizing dye occurs during the period of from preparation of emulsion to coating of the emulsion to damage the good tone reproducibility.

As a means for solving the above problem, it has been proposed in Japanese Patent Kokai No. 62-215943 to use a specific sensitizing dye.

Furthermore, even if the silver halide is spectrally sensitized, since the filter characteristics are obtained from composite characteristics of the characteristics of spectrally sensitized silver halide and those of spectrally nonsensitized silver halide, gradation of the grade No. 5 which is the highest contrast characteristic is the characteristic of spectrally nonsensitized silver halide and with approaching to the grade No. 0, the characteristic is more affected by spectral sensitization and it is preferred that all of the characteristic curves are linear and have tone reproducibility. However, in the conventional dye sensitizing method where amount of the dye per unit surface area of silver halide is constant, the filter characteristic curve lacks the tip portion of the toe or is curved and is not linear to reduce much the tone reproducibility.This is due to the fact that the dye sensitizing characteristics do not have the sensitivity and tone corresponding to the filter characteristics and there is needed a method by which sensitivity and tone which fit to the filter characteristics can be freely produced even when any dye or emulsion is used.

SUMMARY OF THE INVENTION The object of the present invention is to provide a variable contrast silver halide photographic material which has a wide tone reproducibility, is stable during the period from preparation of emulsion until completion of coating of the emulsion and is excellent in storage stability after production.

The above object has been attained by a silver halide photographic material, characterized by having a silver halide emulsion layer comprising the following two components (A) and (B): (A) a spectrally sensitized silver halide emulsion which is spectrally sensitized with a sensitizing dye represented by the following formula (I) and comprises a plurality of components prepared so that they differ in dye adsorption amount per unit surface area of silver halide and (B) a silver halide emulsion which is not spectrally sensitized or if sensitized, has a spectral sensitivity maximum in the region of wavelength shorter than the wavelength in which the silver halide (A) has a spectral sensitivity maximum::

wherein R1 and R2 which may be identical or different each represents an alkyl group, an alkenyl group or an aryl group, L, L1 and L2 each represents CH or CR3 in which R3 represents a lower alkyl group or an aryl group, Zl represents a group of atoms necessary to form a benzoxazole ring having an aryl group or an aralkyl group at 5- and/or 6-positions or represents a naphthoxazole ring, Z2 represents a group of atoms necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring, x represents an anion, Q represents 1 or 2, m represents 0 or 1, and n represents 0, 1 or 2.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 and 2 show change of characteristic curves of the conventional variable contrast photographic paper and the present variable contrast photographic paper, respectively.

DESCRIPTION OF THE INVENTION The present invention will be explained in more detail.

Preparation of silver halide emulsion (A) (hereinafter referred to as "multi-component dye sensitized emulsion") which is spectrally sensitized with a sensitizing dye so that it has an absorption maximum in 480-570 nm and so that it comprises a plurality of components which differ in dye adsorption amount per unit surface area of silver halide is carried out in the following manner. The ordinary silver halide (hereinafter referred to as "one component dye sensitized emulsion") is not constant in dye adsorption amount. Thus, the ratio of amount of the silver halide and amount of sensitizing dye is changed to prepare characteristics which differ in sensitivity and density in multi-components and dye sensitization characteristics are obtained utilizing the final composite characteristic curve.

In the multi-component dye sensitized emulsion of the present invention, the silver halide emulsion (A) which can be sensitized with dyes may be optionally divided depending on dye sensitization characteristics and divided preferably into 2-4 components. The dye sensitization is carried out by forming dye sensitization characteristics by composite characteristics obtained by changing the ratio of the amount of silver halide and that of sensitizing dye depending on the divided silver halide emulsions.With increase in the number of divided silver halide emulsions, the characteristic curve becomes more gentle and there are utilized the characteristics that under a constant addition amount of sensitizing dye, sensitivity is high, contrast is low and density is low when amount of silver halide emulsion is small, and sensitivity is low, contrast is high and density is high when amount of silver halide emulsion is large.

In preparation of the dye sensitization characteristic curve toe characteristics are formed using high sensitivity, low contrast and low density characteristics by increasing the ratio of the amount of the sensitizing dye to the amount of the silver halide.

Amount of the silver halide used in this case is preferably 30% or less of silver halide (A). Belly portion and shoulder portion of the dye sensitization characteristic curve are formed by using low sensitivity, high contrast and high density characteristics with reducing the ratio of the amount of the sensitizing dye to the amount of the silver halide and characteristic curve is prepared by utilizing shoulder characteristics of respective dye sensitization characteristics. By such method, characteristics at any densities of the characteristic curve can be freely prepared. If necessary, the sensitizing dyes may be used in combination.

The divided silver halide emulsions may be respectively dye sensitized and then mixed. Alternatively, dye sensitization may be carried out with successive addition of sensitizing dye and the silver halide emulsions. Preferably, dye ripening is carried out in order to increase dye adsorption efficiency.

The mixing ratio of the silver halide emulsion (A) to which the dye is adsorbed and another silver halide emulsion (B) in the present invention is not critical and preferably, (A) : (B) is 2 : 1 - 1 : 3. Further, the emulsions (A) and (B) may be same or different in halogen composition and grain size. Moreover, the spectral sensitizer which sensitizes, if necessary, to the wavelength shorter than wavelength maximum of (A) may be added to one of (A) and (B) or to the mixture of (A) and (B) and the wavelength maximum is preferably shorter at least 15 nm than that of (A).

For the sensitizing dye in the region of 480 nm - 570 nm, R1 and R2 in the formula (I) may be identical or different and represent alkyl groups (e.g., lower alkyl groups such as methyl, ethyl, propyl, butyl and pentyl, hydroxyalkyl groups such as ss-hydroxyethyl and y-hydroxypropyl, acyloxyalkyl groups such as ss-acetoxyethyl, y-acetoxypropyl, and (3-benzoyloxyethyl, alkoxyalkyl groups such as ss-methoxyethyl, ss-ethoxyethyl, ss-isopropoxythyl and ss-(ss-methoxyethoxy)ethyl, carboxyalkyl groups such as carboxymethyl, ss-carboxy- ethyl, and y-carboxypropyl, alkoxycarbonylalkyl groups such as methoxycarbonylmethyl, ethoxycarbonylmethyl and ss-ethoxycarbonylethyl, sulfoalkyl groups such as ss-sulfoethyl, y-sulfopropyl and S-sulfobutyl, aralkyl groups such as benzyl and phenethyl, and sulfoaralkyl groups such as sulfobenzyl, sulfophenethyl, and others), alkenyl groups (e.g., allyl), and aryl groups (e.g., phenyl).

L, L and L2 each represents CH or CR3 (R3 represents lower alkyl groups or aryl groups as exemplified above for R1 and R2).

Zl represents a group of atoms necessary to form a benzoxazole ring having an aryl group (e.g., phenyl) or an aralkyl group (e.g., benzyl and phenethyl) at least 5- and/or 6-position or represents a naphthoxazole ring (e.g., naphtho2,l-a)oxazole, naphtho(l,2-ajoxazole, naphtho(2,3-a)oxazole, 8,9-dihydronaphthoC1,2-aloxazole).

Z2 represents a group of atoms necessary to complete a 5- or 6-membered nitrogen-containing heterocyclic ring. The heterocyclic ring is well known in the chemistry of cyanine dyes and includes, for example, oxazoline ring, oxazole ring, benzoxazole ring, naphthoxazole ring, isoxazole ring, benzisoxazole ring, oxazolopyridine ring, thiazoline ring, thiazole ring, benzothiazole ring, naphthothiazole ring, thiazolopyridine ring, thiazoloquinoline ring, 1,3,4-thiadiazole ring, selenazoline ring, selenazole ring, benzoselenazole ring, naphthoselenazole ring, pyridine ring, quinoline ring, benzo(f)quinoline ring, isoquinoline ring, acridine ring, imidazole ring, benzimidazole ring, naphthimidazole ring, indolenine ring, benzindolenine ring, imidazoloquinoxaline ring, l,8-naphthylridine ring, and pyrroline ring, X represents an acid anion (e.g., methylsulfate ion, ethylsulfate ion, thiocyanate ion, toluenesulfonate ion, chloride ion, bromide ion, indide ion and perchlorate 1 ion), Q represents 1 or 2, m represents 0 or 1, and n represents 0, 1 or 2.

Typical examples of the dyes are shown below, but the present invention is not limited thereto.

The sensitizing dyes represented by the formula (I) used in the present invention can be easily prepared by known processes. For example, they can be prepared by the processes mentioned in F.M. Homes, "The Cyanine Dyes and Related Compounds", Interscience Publisher, New York (1964) and literature cited in RESEARCH DISCLOSURE, vol.

176, page 23, paragraph N (RD-17643, Dec. 1978).

When the silver halide emulsion is subjected to spectral sensitization to shorter than 480 nm, it is preferred to add a sensitizing dye represented by the following formula (II). This is advantageous for increase of sensitivity at shorter than 480 nm and enhancement of contrast.

wherein Zl represents a group of atoms necessary to complete oxazole, benzoxazole, thiazole, benzothiazole, benzoselenazole, or pyridine ring, Z2 represents S, N-R3 (R3 represents an alkyl group or an aryl group), or 0, and R1 and R2 each represents an alkyl group, a carboxyalkyl group or a sulfoalkyl group.

Typical examples of the these sensitizing dyes are shown below.

The sensitizing dye used in the present invention can be added as a solution in water or an organic solvent miscible with water such as methanol, ethanol or methyl cellosolve to silver halide emulsion to adsorb the dye to the silver halide and then, a separate silver halide emulsion can be mixed therewith.

Furthermore, the dye can also be dissolved in a water-insoluble solvent and added in the form of a dispersion to a silver halide emulsion.

Addition amount of the sensitizing dye varies depending on kind of the sensitizing dye or kind of the emulsion, but usually the optimum amount can be optionally selected within the range of 3-500 mg per 1 mol of silver halide.

Any of silver bromide, silver iodobromide, silver iodochlorobromide, silver chlorobromide and silver chloride may be used as silver halide in the photographic emulsion layer of the photographic material of the present invention. Preferred one is silver iodochlorobromide containing 5 mol% or less of silver iodide. Grain size of silver halide used may be optional, but is preferably 0.8 p or less. These silver halide emulsions can be prepared by known methods such as ammonia method, neutral method, and acidic method. Formation and growth of crystal can be carried out by the well known single jet method, multi-jet method and the like.

The emulsions according to the present invention can contain various additives. For example, when chemical sensitization is carried out with a gold compound, other chemical sensitizers (e.g., sulfur sensitizers such as thiourea and hypo, noble metal sensitizers other than gold, and reduction sensitizers) may be used in combination. Furthermore, the emulsions can contain the above spectral sensitizers which sensitize the emulsion to the wavelength shoter than the wavelength maximum of the silver halide spectrally sensitized with the dye of the formula (I), stabilizers, antifoggants, surface active agents, developing agents, development accelerators, hardeners, hardening accelerators, couplers, silver removal accelerators, dye removal accelerators, fluorescent brighteners, thickening agents and the like.

As protective colloid for the silver halide emulsion used in the present invention, mention may be made of, for example, natural substances such as gelatin, modified gelatin, albumin, agar, gum arabic and alginic acid and water-soluble synthetic resins such as polyvinyl alcohol, polyvinyl pyrrolidone, and copolymer of acrylamide, acrylic acid and vinyl imidazole.

The emulsion of the present invention is coated on a suitable support such as glass, a cellulose acetate film, a polyethylene terephthalate film, a paper, a baryta paper, a polyolefin (e.g., polyethylene and polypropylene) coated paper. These supports may be subjected to corona discharge treatment and besides, if necessary, they may be subjected to subbing treatment by known method.

The silver halide photographic emulsion of the present invention is coated, if necessary, together with protective layer, intermediate layer, ultraviolet absorbing layer, undercoat layer or other silver halide emulsion.

The photosensitive material produced using the silver halide emulsion according to the present invention can be exposed and then developed by usually employed known methods. Black and white developer is an alkali solution containing a developing agent such as a hydroxybenzene, an aminophenol, or aminobenzene which is normally used for photography. Besides, the developer can contain sulfites, carbonates, hydrogensulfites, bromides, and iodides of alkali metals.

The photosensitive materials of the present invention are good in tone reproducibility of filter characteristics due to multi-component type dye sensitization and stable during the period of from preparation of emulsion to completion of coating and are superior in storage stability after production of the photosensitive materials by using a specific cyanine dye.

The present invention will be explained in more detail by the following nonlimiting examples.

Example 1 An emulsion of the present invention subjected to multi-component dye sensitization and a conventional one-component dye sensitized emulsion were prepared by adding sensitizing dye (13) stable in dye adsorbability to chemically sensitized silver iodochloroboromide emulsion (silver iodide: 0.4 mol%, silver bromide: 60 mol%, average grain size: 0.35 ). The one-component dye sensitized emulsion was prepared by adding the sensitizing dye in an amount of 10 mg/l0 g silver halide and leaving it at 500C for 30 minutes until it reached 400C and then adding thereto the same emulsion which had not been dye sensitized in an equal amount based on silver halide.

The multi-component dye sensitized emulsion was prepared in the following manner, 10 g of the silver halide was divided at a ratio of 2 : 4 : 4 before subjected to dye sensitization and similarly, 10 mg of the sensitizing dye was divided at a ratio of 1.5 : 4 : 4.5.

The 15% portion of the divided sensitizing dye was added to the 20% portion of the divided emulsion and the mixture was left to stand for 10 minutes at 500C. Subsequently, thereto was added the 40% portion of the divided emulsion and when temperature thereof reached 50 C, the 40% portion of the divided sensitizing dye was added thereto and the mixture was left to stand for 10 minutes. Then, the remainder 40% portion of the divided emulsion was added thereto and when the temperature reached 500C, the remainder 45% portion of the divided sensitizing dye was added and the mixture was left to stand for 10 minutes.

Temperature was lowered to 400C and to the thus dye sensitized emulsion was added the same emulsion which had not been sensitized with dye in equal amount based on the silver halide.

A stabilizer, a hardener and a surface active agent were added to both the multi-component dye sensitized emulsion and the one-component dye sensitized emulsion, respectively. Each of the emulsion was equally divided into two portions. One of them was coated on a photographic polyethylene laminate paper at 3 g/m2 in terms of silver halide. Another was left for 12 hours at 380C and then similarly coated.

These samples were exposed through Kodak POLYCONTRAST FILTERS and a wedge of 0.15 in density difference and then developed with a developer for photographic paper: GEKKOL (manufactured by Mitsubishi paper Mills Ltd.) at 200C for 90 seconds. Sensitivity (relative value), effective exposure range and gamma were measured and the results are shown in Table I and Figs. 1 and 2.

Table I

Just after prepara- After elapse tion of emulsion of 12 hours Filter Sensi- Effective Gamma Sensi- Effective Gamma tivity exposure tivity exposure range range No. 0 150 1.30 1.4 155 1.35 1.3 Multi-component No. 1 155 1.15 1.6 160 1.20 1.6 dye sensitized No. 2 155 1.05 1.8 160 1.10 1.8 emulsion No. 3 150 0.05 2.0 155 0.95 2.0 (The present No. 4 110 0.65 2.9 110 0.70 2.8 invention) No. 5 100 0.55 3.3 100 0.55 3.2 No. 0 155 1.40 1.3 160 1.45 1.2 One-component No. 1 160 1.25 1.5 165 1.30 1.5 dye sensitized No. 2 160 1.10 1.6 165 1.15 1.6 emulsion No. 3 155 1.00 1.9 155 1.05 1.9 (not the No. 4 110 0.70 2.9 110 0.75 2.8 present No. 5 100 0.55 3.3 100 0.55 3.2 invention) It can be seen from Table 1 that the multicomponent dye sensitized emulsions were stable like the one-component dye sensitized emulsion even after elapse of 12 hours from preparation. Furthermore, although there is substantially no difference in the values of the samples of the present invention and those which are outside the present invention, as is clear from the filter characteristic curves of Figs. 1 and 2, the curves of the multi-component dye sensitized emulsion is linear and is enlarged in tone width.

Example 2 In the same manner as in Example l,emulsions were prepared using sensitizing dye (2) which is relatively sharp in toe. The one-component dye sensitized emulsions were prepared in the same manner as in Example 1. The multi-component dye sensitized emulsions were prepared in the same manner as in Example 1 except that 10 g of the silver halide before sensitized with dye was divided at a ratio of 1.5 : 2.5 : 3 : 3 and the sensitizing dye was divided at a ratio of 2 : 2 : 3 : 3.

The results are shown in Tab e II.

Table II

Multi-component dye One-component dye sensi sensitized emulsion tized emulsion (Not (The present invention) the present invention) Filter Sensi- Effective Gamma Sensi- Effective Gamma tivity exposure tivity exposure range range No. 0 145 1.25 1.4 125 1.05 1.7 No. 1 150 1.10 1.6 130 1.00 1.9 No. 2 150 1.00 1.8 130 0.95 2.1 No. 3 145 0.90 2.0 125 0.80 2.4 No. 4 110 0.65 2.8 105 0.65 2.8 No. 5 100 0.55 3.2 100 0.55 3.1 It can be seen from Table II that by using sensitizing dye of sharp toe, the one-component dye sensitized emulsions became narrower in tone width while the multi-component dye sensitized emulsions increase in sensitivity difference and tone reproducing width. Thus, factors of sensitizing dyes can be completely eliminated by changing proportion of amount of silver halide and that of sensitizing dye.

Example 3 In order to evaluate storage stability of samples just after preparation used in Example 1, these samples were left to stand at 500C and 80% RH for 6 days.

Then, these samples before and after left to stand were exposed through a wedge of 0.15 in density difference and then subjected to the same development treatment as in Example 1 and sensitivity (relative value) and fog were measured.

The results are shown in Table III.

Table III

Just after coating After 6 days at 500C, 80% RH Sample Fog Sensitivity Fog Sensitivity One-component 0.02 100 0.01 102 day sensitized ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Multi-compenent 0.02 100 0.01 101 dye sensitized As can be seen from the results in Table III, the storage stability of the sample prepared by the multi-component dye sensitizing method of the present invention showed no increase in fog and within increase no decrease in sensitivity and the sample was superior in storage stability after production.

Example 4 A multi-component dye sensitized emulsion was prepared in the same manner as in Example 1 and at the time of adding the emulsion which had not been dye sensitized, 5 mg/silver 10 g of the above sensitizing dye (16) was further added for spectral sensitization to shorter than 480 nm. Thereafter, the procedure of Example 1 was repeated. The results obtained are shown in Table IV.

Table IV

Comparative [without the Spectrally sensitized sensitizing dye (16)] to shorter than 480 nm Filter ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Sensi- Effective Gamma Sensi- Effective Gamma tivity exposure tivity exposure range range ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. 0 145 1.25 1.4 145 1.25 1.4 No. 3 145 0.90 2.0 145 0.90 2.0 No. 5 100 0.55 3.2 110 0.55 3.4 As is clear from the above table, sensitivity of spectral sensitization characteristics at shorter than 480 nm can be increased without giving influence on the spectral sensitization characteristics at 480-550 nm.

By using the multi-component dye sensitization method and the sensitizing dye according to the present invention, there is provided a variable contrast silver halide photosensitive material which is stable during the period of from preparation of emulsion to completion of coating thereof, is excellent in storage stability after production of the material and is excellent in tone reproduction width.

Claims (5)

WHAT IS CLAIMED IS:

1. A silver halide photographic material which comprises a support and a silver halide emulsion layer comprising the following two components (A) and (B): (A) a silver halide emulsion which is spectrally sensitized with a sensitizing dye represented by the following formula (I) and comprises a plurality of components prepared so that they differ in dye adsorption amount per unit surface area of silver halide and (B) a silver halide emulsion which is not spectrally sensitized or, if sensitized, has a spectral sensitivity maximum in the region of wavelength shorter than the wavelength in which the silver halide (A) has a spectral sensitivity maximum::

wherein R1 and R2 which may be identical or different each represents an alkyl group, an alkenyl group or an aryl group, L, L1 and L2 each represents CH or CR3 in which R3 represents a lower alkyl group or an aryl group, Zl represents a group of atoms necessary to form a benzoxazole ring having an aryl group or an aralkyl group at at least one of 5- and 6-positions or represents a naphthoxazole ring, Z2 represents a group of atoms necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring, X represents an anion, Q represents 1 or 2, m represents 0 or 1, and n represents 0, 1 or 2.

2. A silver halide photographic material according to claim 1, wherein mixing ratio of the silver halide emulsion (A) and the silver halide emulsion (B) is 2 : 1 1 : 3.

3. A silver halide photographic material according to claim 1, wherein amount of the sensitizing dye is 3-500 mg per 1 mol of silver halide.

4. A silver halide photographic material according to claim 1, which additionally has at least one of protective layer, intermediate layer, ultraviolet absorbing layer and undercoat layer.

5. A silver halide photographic material according to claim 1, wherein the silver halide emulsion (A) has an absorption maximum in 480-570 nm.