EP0530827A2

EP0530827A2 - Image forming process

Info

Publication number: EP0530827A2
Application number: EP92115175A
Authority: EP
Inventors: Yasuo c/o Fuji Photo Film Co. Ltd. Aotsuka; Masahiro C/O Fuji Photo Film Co. Ltd. Asami; Yoshiharu c/o Fuji Photo Film Co. Ltd. Okino
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1991-09-06
Filing date: 1992-09-04
Publication date: 1993-03-10
Also published as: JPH05113629A; JP2881055B2; EP0530827A3

Abstract

An image is formed in a silver halide photosensitive material by imagewise exposing it using a semiconductor laser or LD of the longitudinal single mode. The photosensitive layer has a γ value of at least 1.5 and optionally, a dynamic range of up to 2.0 as expressed in logE unit. The emission wavelength during exposure is in such a range that the Δlog(spectral sensitivity) of the photosensitive layer per nm is within ±0.015 and/or in a range of ±10 nm from the maximum spectral sensitivity wavelength (nm) of the photosensitive layer. An image of quality is obtained without image unevenness.

Description

TECHNICAL FIELD

This invention generally relates to a process for forming images in a silver halide photosensitive material, and more particularly, to a process for exposing a silver halide photosensitive material in accordance with image signals in the form of electrical signals through the use of a semiconductor laser light emitting element.

BACKGROUND OF THE INVENTION

For recording outputs of LED, LD and similar light sources adapted for scanning exposure, silver halide photosensitive materials are widely employed whether images are black-and-white or color images and whether images are of halftone or continuous tone. This is because the high sensitivity, gradation and sharpness of silver halide photosensitive material allows for the design of a high image quality system. Particularly as the processing procedure of silver halide photosensitive material is simplified and accelerated, a high quality image forming system of the scanning exposure type utilizing silver halide photosensitive material is currently under consistent development.
With the advance of such a system, the output stability of a scanning exposure light source becomes of concern. It is well known for LED, for example, that as the temperature increases, the light emission wavelength shifts to a longer side and the power lowers continuously, resulting in uneven image density. It was found in Japanese Patent Application Kokai (JP-A) No. 52642/1986 that this problem could be overcome by setting the peak wavelength of the spectral sensitivity of photosensitive material longer than the wavelength of the light source. This technique is also effective for reducing image unevenness caused by the droop of semiconductor laser.
Semiconductor lasers, especially of the longitudinal single mode are accompanied by the hopping phenomenon that the emission wavelength varies discontinuously, which causes undesirable image variations.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an image forming process of the scanning exposure type for forming an image of high quality in a silver halide photosensitive material through even exposure using a semiconductor laser of the longitudinal single mode
According to the present invention, there is provided a process for forming an image in a photosensitive material having at least one photosensitive layer containing a photosensitive silver halide on a support, by imagewise exposing the at least one photosensitive layer using a modulatable light source. The light source is a semiconductor laser of the longitudinal single mode capable of emitting light at a wavelength which discontinuously varies in accordance with a variation in temperature or luminous quantity. The photosensitive layer has a gamma (γ) value of at least 1.5. In a first aspect, the emission wavelength during exposure is in such a range that the variation of the logarithm of the spectral sensitivity of the photosensitive layer per nm, Δlog(spectral sensitivity)/nm, is within ±0.015. In a second aspect, the emission wavelength during exposure is within a range of ±10 nm from the maximum spectral sensitivity wavelength (nm) of the photosensitive layer. In a preferred embodiment, the photosensitive layer has a dynamic range of exposure quantity (E) of up to 2.0 as expressed in logE unit.
JP-A 35445/1990 discloses "a silver halide photosensitive material adapted to be exposed to light from a light source in which the maximum wavelength of emission spectrum varies with temperature and manufacturing parameters, characterized in that the spectral sensitivity distribution of said silver halide photosensitive material is within 0.2 (logE) relative to the rated wavelength of the light source ±25 nm."
In contrast, the present invention is distinguished over JP-A 35445/1990 in that a semiconductor laser of the longitudinal single mode is selectively utilized as the light source for exposure. The cited publication refers nowhere to the mode hopping phenomenon inherent to a semiconductor laser of the longitudinal single mode or to the γ and dynamic range (DR) of the photosensitive layer. We have found that the unevenness of exposure caused by the mode hopping phenomenon depends on the γ of the photosensitive layer and hence, the DR thereof as will be described later. Based on this finding, the present invention provides the great benefit of minimizing the unevenness of exposure, which is unexpected from the cited publication.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will be more fully understood by reading the following description taken in conjunction with the accompanying drawings.
FIG. 1 is a graph illustrating the mode hopping phenomenon depending on temperature change.
FIG. 2 is a graph illustrating gamma (γ) used in the present invention.
FIG. 3 is a graph illustrating the dynamic range (DR) used in the present invention.
FIG. 4 is a graph showing the spectral sensitivity of a heat developable color photosensitive material in Example 1.
FIG. 5 is a graph showing the spectral sensitivity of a color print paper in Example 2.

DETAILED DESCRIPTION OF THE INVENTION

The image forming process according to the present invention is to form an image in a photosensitive material having at least one photosensitive layer containing a photosensitive silver halide on a support. The photosensitive layer is imagewise exposed to light from a light source in the form of a modulatable semiconductor laser.
The image forming process of the invention is effective for both black-and-white and color systems. It is also effective for both dot printing and continuous tone photographic systems. Therefore, the invention is applicable to a wide variety of silver halide photosensitive materials which are of negative type.
The light source for exposure is comprised of a light-emitting element in the form of a semiconductor laser or laser diode (LD). The LD which is a semiconductor element emits light the intensity of which is controllable by controlling the current conducted across the light emitting element without a need for an external modulator, and it is an inexpensive compact light-emitting element capable of high efficiency exposure. The LD has the advantage of an increased exposure quantity since the light emanating therefrom can be effectively condensed through a collimator lens.
Since the light output vs current of the LD is highly temperature dependent, it is essential to control the LD so as to deliver a consistent luminous quantity in order to ensure exposure of images of quality. This is generally solved by using a light quantity detecting photodiode (PD) which has been built in the LD package and carrying out automatic power control (APC) to control current across the LD so as to make constant the quantity of light emitting from the LD. The light quantity detecting element used herein may also be a photodiode mounted outside the LD package.
In the semiconductor light-emitting element, the light emission or luminous wavelength is dependent on temperature. For example, an AlGaAs laser diode has a temperature coefficient of 0.23 to 0.27 nm/°C.
For digital exposure at a single wavelength in the practice of the invention, it is preferred to use a LD of the longitudinal single mode which is characterized in that the wavelength changes discontinuously. This is known as the mode hopping phenomenon.
The term "single mode" used herein refers to the oscillating wavelength which may have one or more peaks and implies that the intensity of one or more subpeaks is up to 1/5, preferably up to 1/10 of the intensity of the main peak.
When an image whose density varies continuously in the raster scanning direction is recorded, the mode hopping is visually perceivable on the image. This is because the mode hopping occurs when the luminous intensity of the LD varies continuously, with concomitant fluctuations of luminous intensity and wavelength. The location at which these fluctuations occur changes for every raster, resulting in a variable density stripe pattern being visually perceivable.
The mode hopping also occurs when the light emitting LD experiences a temperature change. Then the mode hopping can occur during exposure of one raster due to the heat release of the LD itself, resulting in an unevenness on the image.
It is to be noted that the LD is usually temperature controlled from outside the LD package using a heater, Peltier element or the like. It is still difficult to maintain the light emitting or active layer of the LD at a constant temperature, and a temperature change over a few degrees in centigrade cannot be eliminated. This temperature change over a few °C causes a variation of the oscillating wavelength over 1 nm.
FIG. 1 illustrates the mode hopping caused by temperature changes. The oscillating wavelength on the ordinate is plotted relative to the temperature of the LD package on the abscissa.
It is seen that the longitudinal single mode LD emits light at a wavelength which varies discontinuously in accordance with a change in temperature or luminous quantity. This mode hopping phenomenon induces a variation of image density.
Now assume that the wavelength of a light source has discontinuously varied from λ1 nm to λ2 nm and that a photosensitive layer corresponding to the light source has spectral sensitivities S1 and S2 relative to the incident beams λ1 and λ2, then the spectral sensitivity of the photosensitive layer undergoes a substantial change of ΔS = S2/S1 as a result of the discontinuous variation of the light source wavelength. Then the image density experiences a change of γxlogΔS wherein γ is the gamma value of the photosensitive layer.
As used herein, γ is defined as the gradient of a straight line connecting points a and b in the characteristic curve of FIG. 2 wherein a is a point on the curve which provides the minimum density (Dmin) plus 0.5 (a = Dmin + 0.5) and b is a point on the curve which corresponds to point b1 on log E axis which is obtained by rightward shifting by 0.5 along logE axis from point a1 on logE axis corresponding to point a (b1: logE = a1 + 0.5). Provided that a point on D axis which corresponds to point b has a value of (Dmin + 0.5 + x), then γ is equal to the gradient represented by (x/0.5).
It is understood from these relationships that as the wavelength variation due to the mode hopping of a light source is greater and in the case of an equal wavelength variation, as the spectral sensitivity wavelength dependency and γ of a photosensitive material are greater, the density difference becomes greater, resulting in images of lower quality.
According to the present invention, at least one photosensitive layer of a silver halide photosensitive material which is to be exposed to light of the LD should have a γ value of at least 1.5, preferably at least 2.0. A γ value of 1.5 or higher allows the photosensitive material to have a narrower dynamic range than the dynamic range of an exposure system, which facilitates a system design to achieve a sufficient image density. On the contrary, with a γ value of less than 1.5, it is difficult to elaborate the system design or to take full advantage of photosensitive material, resulting in images of lower density. The upper limit of γ is generally about 12.
The photosensitive layer should preferably have a dynamic range (DR) of up to 2.0, especially up to 1.8 as expressed in logE unit. The photosensitive layer having such a DR is suitable for use with LD which is an exposure light source with a narrow dynamic range. If DR is in excess of 2.0, it is difficult to utilize a photosensitive material over its entire density range. The lower limit of DR is preferably approximately 0.3 from the standpoint of minimizing an image density variation.
The term "dynamic range" (DR) used herein is defined as (B - A) in the characteristic curve shown in FIG. 3 wherein A is a point on logE axis which is obtained by shifting leftward along logE axis by 0.2 from point M on logE axis which gives a density equal to the minimum density plus 0.1 (Dmin + 0.1) (A: logE = M - 0.2), and B is a point on logE axis which gives a density equal to the maximum density minus 0.1 (Dmax - 0.1). DR is defined in this way because the actually available density range is approximately from Dmin to (Dmax - 0.1). That portion of the density range located adjacent to Dmax is not utilized in most cases since that portion is of softer gradation and the exposure unit must be designed so as to provide a greater change of luminous quantity in order to achieve only a slight density difference in that portion.
For the photosensitive layer of such nature, the emission or luminous wavelength during exposure is

(1) in such a range that the variation of the logarithm of the spectral sensitivity of the photosensitive layer per nm, Δlog(spectral sensitivity)/nm, is within ±0.015, preferably substantially 0, or
(2) within a range of ±10 nm, preferably ±7 nm from the maximum spectral sensitivity wavelength (nm) of the photosensitive layer. It is also contemplated that the emission wavelength during exposure is concurrently within ranges (1) and (2).

The emission wavelength within one of these ranges is effective for preventing occurrence of uneven image density when combined with the photosensitive layer having a γ of at least 1.5 and a dynamic range (DR) of up to 2.0. Then a higher image density (Dmax) is achieved and images of higher quality are obtained.
In the practice of the invention, a photosensitive layer is imagewise exposed to light from an LD using the arrangement shown in Japanese Patent Application No. 318351/1990 by the same assignee as the present invention. LD light may be focused on a photosensitive material by the following procedure.
An LD emits laser light which is collimated into substantially parallel beams through a collimator lens. Using a cylindrical lens having power only in a subordinate scanning direction, the beams are linearly focused on a polygon mirror as a polarizer. The beams are rotated at an equal angular velocity with rotation of the polygon mirror, but focused through a fϑ lens so as to provide equal velocity scanning on the photosensitive material. The fϑ lens and cylindrical mirror cooperate to correct a differential pitch between rasters due to surface tilting of the polygon mirror.
Alternatively, the optical system used herein may be of the arrangements shown in JP-A 77018/1989 and 81926/1989.
In polarizing laser beams through a polygon mirror, a jitter associated with the rotation of a motor for driving the polygon mirror and an angular error between adjacent planes of the polygon mirror cause a change in scanning start timing between respective rasters on the photosensitive material. Then the optical system is provided with a sensor for detecting the scanning start timing so that the image modulation signal of each raster may be synchronized with the timing of a detection signal of the sensor whereby a fluctuation-free image is exposed without any influence of such a timing change. The sensor for detecting the scanning start timing is disposed in the optical system at a location in front of an image exposure region on the photosensitive material.
In order to supply a modulation signal of each pixel to a LD drive circuit in synchronization with the scanning start timing detection signal, a counter is provided for starting demultiplying a clock signal of a fixed frequency corresponding to an integral multiplication of the pixel repetition period in synchronization with the scanning start timing detection signal. Using an output of the counter as a pixel synchronization signal, an image of high precision can be exposed without any influence of raster fluctuation.
For the modulation of LD light, the following method is used. The modulation method includes a method of directly modulating an LD for the imagewise exposure of a photosensitive material by changing conducting current to modulate the intensity of light for each pixel (intensity modulation) and a method of modulating an LD by controlling the luminous time for each pixel while keeping the luminous intensity constant (time modulation).
In the case of the former intensity modulation method, since the range of LD at which the light output remains linear relative to conducting current, that is, the ratio of maximum to minimum luminous quantity laser oscillated is generally as low as about 10, it is impossible for laser light alone to cover the dynamic range required by the photosensitive material. It might be contemplated to use a non-linear region of LD, that is, LED light in order to secure a wider dynamic range. However, since LD light and LED light have different beam shapes focused on a photosensitive material, the photosensitive material undergoes a density variation due to multiple exposure effect, resulting in images of poor quality.
In the case of the latter time modulation method, it is possible to modulate laser light over a wide dynamic range since the LD is capable of high speed switching.
Although mode hopping can occur in either of the modulation methods, the present invention is effective in either case. The benefits of the present invention become more noticeable in the intensity modulation method which can induce substantial mode hopping.
The negative photosensitive materials which can be used herein include black-and-white photosensitive materials such as black-and-white photographic paper, black-and-white negative film and black-and-white positive film and color photosensitive materials such as color photographic paper, color negative film and color positive film. Also included are black-and-white and color heat developable photosensitive materials.
In the case of color photosensitive materials, the present invention is applicable to at least one photosensitive layer, preferably two or more photosensitive layers thereof.
In addition to the photosensitive layer or layers, the photosensitive material which can be used herein may include various auxiliary layers such as protective, undercoating, intermediate, anti-halation and back layers. Further, there may be added various filter dyes for improving color separation and anti-irradiation dyes for improving sharpness.
Among these photosensitive materials, reference is mainly made to color photosensitive materials, especially color photographic paper and heat developable color photosensitive material in the following description although the invention is not limited thereto.
As the photosensitive material which can be used in the image forming process of the invention, conventional color paper and similar photographic materials in which color images are formed through conventional color development may be advantageously used. The photosensitive material used herein contains silver halide grains as a photosensitive element and color couplers as a dye forming element. The color couplers are those compounds which can form dyes by coupling with oxidants of aromatic primary amine developing agents which are formed upon development of the silver halide grains, and commonly used color couplers are compounds having an active methylene site. The organization of the color paper which can be used in the invention is described below.
The silver halide color photographic photosensitive material forming color paper used herein generally has three or more silver halide emulsion layers on a support. preferably at least one emulsion layer has maximum spectral sensitivity at a wavelength of 700 nm or higher. Also, photosensitive material in which at least two emulsion layers have maximum spectral sensitivity at a wavelength of 670 nm or higher is also preferred.

The photosensitive layer or layers of the silver halide color photographic photosensitive material should preferably contain at least one coupler which develops color through coupling reaction with an oxidant of an aromatic amine compound. For full color hard copies, the photosensitive material should preferably have at least three silver halide photosensitive layers with different color sensitivities on a support, each of which contains one of couplers capable of yellow, magenta and cyan color development through coupling reaction with an oxidant of an aromatic amine compound. These three different spectral sensitivities can be arbitrarily selected in terms of the wavelength of a light source used for digital exposure as long as they meet the requirement of the present invention although one spectral sensitivity maximum is preferably spaced at least 30 nm from the nearest spectral sensitivity maximum from the standpoint of color separation. The at least three photosensitive layers (λ1, λ2, λ3) having different spectral sensitivity maximums may contain any of color couplers (Y, M, C) without any limit on the relationship between a layer and a color coupler. Six combinations (3x2 = 6) are possible. No limit is imposed on the order of coating the at least three photosensitive layers having different spectral sensitivity maximums on a support. It is sometimes preferred from the standpoint of rapid processing to dispose a photosensitive layer containing silver halide grains having the largest mean particle size as the uppermost layer. There are 36 possible combinations among the three different spectral sensitivities, three color couplers and coating order of layers. The present invention is effective for all photosensitive materials of these 36 combinations. Since a semiconductor laser is used as a light source for digital exposure in accordance with the invention, at least one of the at least three silver halide photosensitive layers having different color sensitivities should preferably have spectral sensitivity maximum at a wavelength of 700 nm or longer and additionally, at least two layers thereof should preferably have spectral sensitivity maximum at a wavelength of 670 nm or longer. Also no limit is imposed on the spectral sensitivity maximum, color coupler and layer stacking order. Table 1 lists up several typical examples of the spectral sensitivity maximum and color coupler combined with a digital exposure light source in the form of a semiconductor laser although the invention is not limited thereto.

Table 1

	Digital exposure light source		Color development	Photosensitive material's spectral sensitivity maximum (nm)
	Light source	Wavelength (nm)
1	AlGaInAs (670) GaAlAs (750) GaAlAs (810)	670	C	670
		750	Y	745
		810	M	810
2	AlGaInAs (670) GaAlAs (750) GaAlAs (810)	670	Y	670
		750	M	745
		810	C	810
3	AlGaInAs (670) GaAlAs (750) GaAlAs (830)	670	M	670
		750	C	750
		830	Y	830
4	AlGaInAs (670) GaAlAs (780) GaAlAs (830)	670	Y	670
		780	M	780
		830	C	840
5	AlGaInAs (670) GaAlAs (780) GaAlAs (880)	670	C	670
		780	M	780
		880	Y	880
6	GaAlAs (780) GaAlAs (830) GaAlAs (880)	780	M	780
		830	Y	830
		880	C	880
7	GaAs (1200) + SHG* AlGaInAs (670) GaAlAs (880)	600	M	600
		670	Y	670
		750	C	750

* SHG: second harmonic generator using a non-linear optical element

Photographic component layers of the color paper used herein (e.g., emulsion, intermediate and surface layers) each preferably have a thickness of 6 to 20 µm, more preferably 7 to 12 µm. The process of the invention is particularly effective to color photosensitive material of multilayer structure.
The silver halide emulsion used herein is preferably one containing silver chlorobromide or silver chloride, but substantially free of silver iodide. By the term "substantially free of silver iodide" it is meant that the silver iodide content is less than 1 mol%, especially less than 0.2 mol%. The halogen composition of the emulsion may be either identical or different among grains although the use of an emulsion having an identical halogen composition among grains facilitates to homogenize the properties of grains. With respect to the halogen composition distribution within silver halide emulsion grains, a choice may be made among grains of the uniform structure in which the composition is identical throughout silver halide grains, grains of the multilayer structure in which the halogen composition is different between a core and a surrounding shell (including one or more layers) of each silver halide grain, and grains of the structure which has portions of a different halogen composition in the interior or at the surface of each grain in a non-layer arrangement (where different halogen composition portions are at the grain surface, these portions are joined to grains at edges, corners or faces thereof). The use of the latter two grains is advantageous rather than the uniform structure grains in order to provide high sensitivity and also from the standpoint of pressure resistance. Where silver halide grains have such a structure, adjoining portions of different halogen compositions may define either a definite interface or an indefinite interface in which mixed crystals are formed due to differential composition. Alternatively, grains may be intentionally provided with a continuous structural change.
For the photosensitive material adapted for rapid processing, emulsions having a high silver chloride content known as high silver chloride emulsions are preferably used. The high silver chloride emulsions should preferably have a silver chloride content of at least 90 mol%, especially at least 95 mol%. Preferably, the high silver chloride emulsions are of the structure in which silver bromide phase portions are localized in the interior and/or at the surface of silver halide grains in a layer or non-layer arrangement. Such localized phases are preferably of halogen compositions having a silver bromide content of at least 10 mol%, especially in excess of 20 mol%. These localized phases may be present in the interior of grains or at edges, corners or surfaces of grains. In one preferred example, a localized phase is epitaxially grown on corners of grains.
For the purpose of minimizing a sensitivity drop of photosensitive material upon application of pressure thereto, it is also preferred to use grains of the uniform structure having a narrow distribution of halogen composition within the grains even in the case of high silver chloride emulsions having a silver chloride content of at least 90 mol%.
Also, for the purpose of reducing the amount of a developer solution replenished, it is effective to further increase the silver chloride content of silver halide emulsions. In this regard, substantially pure silver chloride emulsions such as having a silver chloride content of 98 to 100 mol% are also advantageously used.
The silver halide grains contained in the silver halide emulsion used herein preferably have a mean grain size of 0.1 to 2 µm. The mean grain size used herein is a number average of grain sizes each of which is the diameter of a circle equivalent to the projected area of a grain. Moreover, the grain size distribution is preferably monodispersed, that is, has a coefficient of variation of up to 20%, especially up to 15%. The coefficient of variation is a standard deviation of the grain size distribution divided by the mean grain size. In this regard, it is also preferred to blend monodispersed emulsions in a single layer or to coat such emulsions in an overlapping manner for the purpose of providing a wide latitude.
The silver halide grains in the photographic emulsion may have a regular crystal form such as cube, octahedron, and tetradecahedron (14 sided), an irregular crystal form such as spherical and plate forms or a composite form of these crystal forms, or a mixture of different crystal form grains. The preferred emulsion contains at least 50%, more preferably at least 70%, most preferably at least 90% of grains of regular crystal form.
Also preferred is an emulsion in which plate grains having an average aspect ratio (equivalent circle diameter/thickness) of at least 5, especially at least 8 occupy at least 50% of the entire projected area of grains.
The photographic, typically silver chlorobromide, emulsion used herein may be prepared by any conventional technique as disclosed in P. Grafkides, "Chimie et Physique Photographique", Paul Montel (1967), G.F. Duffin, "Photographic Emulsion Chemistry", Focal Press (1966), and V.L, Zelikman et al., "Making and Coating Photographic Emulsion", Focal Press (1964). More particularly, acidic, neutral and ammonia methods may be used. The mode of reacting a soluble silver salt with a soluble halide may be single jet, double jet or a combination thereof. It is also employable to form grains in the presence of excess silver, which is known as reverse mixing method. One special type of the double jet technique is by maintaining constant the pAg of a liquid phase in which silver halide is created, which is known as a controlled double jet technique. This technique results in a silver halide emulsion of grains having a regular crystalline form and a nearly uniform particle side.
It is possible to introduce various polyvalent metal ion impurities into the silver halide emulsion at the stage of emulsion grain formation or physical ripening. The compounds used herein include salts of cadmium, zinc, lead, copper and thallium, and salts or complex salts of Group VIII elements such as iron, ruthenium, rhodium, palladium, osmium, iridium, and platinum, with the Group VIII elements being preferred. These compounds are preferably added in amounts of 10⁻⁹ to 10⁻² mol per mol of the silver halide although the exact amount may vary over a wider range depending on a particular purpose.
For chemical sensitization, sulfur sensitization as typified by the addition of unstable sulfur compounds, noble metal sensitization as represented by gold sensitization, or reduction sensitization may be used alone or in combination. At to the compounds used in chemical sensitization, reference is made to JP-A 215272/1987, pages 18-22.
The emulsion of each layer of photosensitive material is subject to spectral sensitization for the purpose of imparting spectral sensitivity in a desired light wavelength region to the emulsion. In the present invention, spectral sensitization is preferably carried out by adding a dye which absorbs light in a wavelength region corresponding to the desired spectral sensitivity, that is, a spectrally sensitizing dye. The spectrally sensitizing dyes used herein are described, for example, in F.M. Harmer, Heterocyclic compounds-Cyanine dyes and related compounds, John Wiley & Sons New York, London, 1964. Exemplary compounds and spectrally sensitizing procedure are described, for example, in the above-referred JP-A 215272/1987, pages 22-38.
The silver halide emulsion used herein is preferably subject to gold sensitization as is well known in the art. The gold sensitization minimizes a variation of photographic properties upon scanning exposure to laser light. Gold sensitization may be effected using gold compounds such as chloroauric acid or salts thereof, gold thiocyanates and gold thiosulfates. These gold compounds are preferably added in amounts of 5x10⁻⁷ to 5x10⁻³ mol, more preferably 1x10⁻⁶ to 1x10⁻⁴ mol per mol of silver halide although the exact amount may vary over a wider range as the case may be. The gold compounds may be added before chemical sensitization has been complete.
In the practice of the invention, gold sensitization may be combined with another sensitization method, for example, sulfur sensitization, selenium sensitization, reduction sensitization or noble metal sensitization using noble metal compounds other than gold.
In the silver halide emulsion used herein, various compounds or precursors thereof may be added for the purpose of preventing fogging or stabilizing photographic properties during preparation, storage or photographic processing of photosensitive material. Examples of the antifogging and stabilizing compounds are described, for example, in the above-referred JP-A 215272/1987, pages 39-72.
The emulsion used herein is of the surface latent image type wherein latent images are predominantly formed at the surface of grains.
Since a semiconductor laser is used as a light source for digital exposure according to the present invention, the emulsion should undergo effective spectral sensitization in the infrared region. Especially for spectral sensitization in a region of 700 nm or longer, sensitizing dyes represented by general formulae (Q-I), (Q-II) and (Q-III) are useful. These sensitizing dyes are relatively stable chemically, relatively strongly adsorb to the surface of silver halide grains, and are resistant to detachment by a dispersion of a coexisting coupler.
The sensitizing dyes of general formulae (Q-I), (Q-II) and (Q-III) are described in detail.
In formula (Q-I), Z₆₁ and Z₆₂ each are a group of atoms necessary to form a heterocyclic nucleus. The heterocyclic nucleus is preferably a five- or six-membered ring containing a nitrogen atom or atoms and optionally, another atom such as a sulfur, oxygen, selenium and tellurium atom as hetero atoms, which ring may have another ring fused thereto or a substituent attached thereto. Examples of the heterocyclic nucleus include thiazole, benzothiazole, naphthothiazole, selenazole, benzoselenazole, naphthoselenazole, oxazole, benzoxazole, naphthoxazole, imidazole, benzimidazole, naphthoimidazole, 4-quinoline, pyrroline, pyridine, tetrazole, indolenine, benzindolenine, indole, tellurazole, benzotellurazole, and naphthotellurazole nuclei.
R₆₁ and R₆₂ each are an alkyl, alkenyl, alkynyl or aralkyl radical. These radicals and radicals to be described later are used in a sense that they may have a substituent. For example, the alkyl radicals include substituted and unsubstituted alkyl radicals which may be linear, branched or cyclic. Preferably, the alkyl radicals have 1 to 8 carbon atoms. Exemplary substituents of the substituted alkyl radical are halogen atoms (e.g., chloro, bromo and fluoro), cyano, alkoxy, substituted or unsubstituted amino, carboxylate, sulfonate, and hydroxyl radicals. The alkyl radical may have such substituents alone or in admixture of two or more. An exemplary alkenyl radical is a vinylmethyl radical. Exemplary aralkyl radicals are benzyl and phenethyl radicals.
R₆₃ is a hydrogen atom, and R₆₄ is a hydrogen atom, lower alkyl radical or aralkyl radical or forms a five- or six-membered ring with R₆₂. Where R₆₄ is a hydrogen atom, R₆₃ may form a hydrocarbon ring or heterocyclic ring with another R₆₃. This ring is preferably five- or six-membered.
Letter m61 and is a positive number of 1, 2 or 3, and j61 and k61 are equal to 0 or 1. X₆₁ is an acid anion, and n61 is equal to 0 or 1.
In formula (Q-II), Z₇₁ and Z₇₂ are as defined for Z₆₁ and Z₆₂ in formula (Q-I).
R₇₁ and R₇₂ are as defined for R₆₁ and R₆₂ in formula (Q-I). Letters j71, k71 and n71 and X71 are as defined for j61, k61 and n61 and X61 in formula (Q-I).
R₇₃ is an alkyl, alkenyl, alkynyl or aryl radical. Examples of the aryl radical include substituted or unsubstituted phenyl radicals. Letter m71 is equal to 2 or 3. R₇₄ is a hydrogen atom, lower alkyl or aryl radical, or forms a hydrocarbon ring or heterocyclic ring with another R₇₄, which ring is preferably five- or six-membered.
Q₇₁ is a sulfur, oxygen or selenium atom or =N-R₇₅ wherein R₇₅ is as defined for R₇₃.
In general formula (Q-III), Z₈₁ is a group of atoms necessary to form a heterocyclic ring. Examples of the heterocyclic ring are as described for Z₆₁ and Z₆₂ and exemplary are thiazolidine, benzothiazolidine, naphthothiazolidine, selenazolidine, selenazoline, benzoselenazoline, naphthoselenazoline, benzoxazoline, naphthoxazoline, dihydropyridine, dihydroquinoline, benzimidazoline, and naphthoimidazoline nuclei.
Q₈₁ is as defined for Q₇₁ in formula (Q-II). R₈₁ is as defined for R₆₁ or R₆₂, and R₈₂ is as defined for R₇₃. Letter m81 is equal to 2 or 3. R₈₃ is as defined for R₇₄ or forms a hydrocarbon ring or heterocyclic ring with another R₈₃. Letter j81 is as defined for j61.
Preferred are those sensitizing dyes of general formula (Q-I) wherein the heterocyclic nucleus of Z₆₁ and/or Z₆₂ has a naphtothiazole, naphthoselenazole, naphthoxazole, naphthoimidazole or 4-quinoline nucleus. The same applies to Z₇₁ and/or Z₇₂ in formula (Q-II) and Z₈₁ in formula (Q-III). Also preferred are those sensitizing dyes wherein the methine chain forms a hydrocarbon ring or heterocyclic ring.
Infrared sensitization which relies on the M-band sensitization of sensitizing dyes generally has a broader spectral sensitization distribution than the J-band sensitization. Then a colored layer containing a dye is provided as a colloidal layer disposed on the exposure side with respect to the relevant photosensitive layer in order to correct the spectral sensitization distribution. This colored layer has a filtering function which is effective in preventing color mixing.
The sensitizing dyes for infrared sensitization are preferably those compounds having a reduction potential of -1.05 volts vs SCE (standard calomel electrode) or more negative, more preferably -1.10 volts vs SCE or more negative. Sensitizing dyes having such a negative reduction potential are advantageous for increasing sensitivity, especially for stabilizing sensitivity and a latent image.
It is to be noted that the reduction potential may be measured by phase-discriminating second harmonic AC polarography. For example, the working electrode is a dropping mercury electrode, the reference electrode is a saturated calomel electrode and the counter electrode is platinum. Measurement of reduction potential by the phase-discriminating second harmonic AC voltammetry using a working electrode of platinum is described in J. Lenhard, Journal of Imaging Science, vol. 30 (1986), pages 27-35.
Examples of the sensitizing dye used herein are described in JP-A 157749/1990, pages 8-13. In addition, the following sensitizing dyes identified SD1 to SD114 are also useful. In the following formulae, Me is methyl, Et is ethyl, and Ph is phenyl, and PTS⁻ is a para-toluenesulfonate ion.
These spectral sensitizing dyes may be introduced in the silver halide emulsion according to the present invention by directly dispersing the dye in the emulsion. It is also possible to dissolve the dye in a solvent such as water, methanol, ethanol, propanol, methyl cellosolve, and 2,2,3,3-tetrafluoropropanol or a mixture thereof and then add the solution to the emulsion. Alternatively, the dye may be added to the emulsion by dissolving the dye in water in the co-presence of an acid or base to form an aqueous solution as disclosed in JP-B 23389/1969, 27555/1969 and 22089/1982; by dissolving or dispersing the dye in water in the co-presence of a surfactant to form an aqueous solution or colloidal dispersion which is added to an emulsion as disclosed in USP 3,822,135 and 4,006,025; by dissolving the dye in a solvent substantially immiscible with water such as phenoxyethanol and then dispersing in water or hydrophilic colloid to form a dispersion which is added to an emulsion; and by directly dispersing the dye in a hydrophilic colloid to form a dispersion which is added to an emulsion as disclosed in JP-A 102733/1978 and 105141/1983.
The stage at which the sensitizing dye is added to the silver halide emulsion may be any stage of emulsion preparation which has been recognized to be significant for spectral sensitization. More particularly, the dye may be added at any stages including before grain formation for a silver halide emulsion, during grain formation, from immediately after grain formation to prior to a water washing step, before chemical sensitization, during chemical sensitization, from immediately after chemical sensitization to cooling and solidification of an emulsion, and during preparation of a coating solution. Most often, the dye is added after the completion of chemical sensitization and before coating. It may be added at the same time as a chemical sensitizer to carry out spectral sensitization and chemical sensitization simultaneously as disclosed in USP 3,628,969 and 4,225,666; or before chemical sensitization as disclosed in JP-A 113928/1983; or well before to start spectral sensitization before the completion of silver halide grain precipitation. Furthermore, as disclosed in USP 4,225,666, a spectral sensitizing dye may be added in divided portions during different steps, for example, one portion prior to chemical sensitization and the remainder after chemical sensitization. The dye may be added at any stage during silver halide grain formation as taught by USP 4,183,756. Preferably, the sensitizing dye is added before water washing of the emulsion or before chemical sensitization.
The spectral sensitizing dye may be added in a varying amount although the preferred amount is from 0.5x10⁻⁶ to 1.0x10⁻² mol per mol of silver halide, especially from 1.0x10⁻⁶ to 5.0x10⁻³ mol per mol of silver halide.
For M-band sensitization in red or infrared sensitization in accordance with the invention, supersensitization by such compounds as described in JP-A 157749/1990, pages 13-22 is effective.
In the photosensitive material of the invention, compounds for improving color image storage stability as disclosed in EP 0277589 A2 are preferably used along with couplers, especially pyrazoloazole couplers. That is, a compound (F) which chemically bonds with an aromatic amine developing agent retained after color development to form a chemically inactive, substantially colorless compound and a compound (G) which chemically bonds with an oxidant of an aromatic amine developing agent retained after color development to form a chemically inactive, substantially colorless compound is used alone or in combination. Use of such compounds is effective for preventing stain and other side effects due to formation of color developing substances through reaction of the coupler with a color developing agent or an oxidant thereof retained in the film during storage after development process.
Further, antibacterial agents as disclosed in JP-A 271247/1988 are preferably added to the photosensitive material according to the invention for controlling propagation of bacteria and fungi in the hydrophilic colloid layer which would otherwise degrade the image.
Dyes may be used for improving sharpness and other image quality. Exemplary dyes are the following compounds identified as (A-1) through (A-43).
The support used in the photosensitive material according to the present invention may be selected from transparent films for use in photographic photosensitive materials such as cellulose nitrate films and polyethylene terephthalate films and reflective supports. Use of reflective supports is more advantageous for the objects of the invention.
The "reflective support" used herein is a support which is increased in reflection so as to make clearer or sharper a dye image formed on a silver halide emulsion layer. The reflective supports include supports coated with a hydrophobic resin having a light reflective substance (e.g., titanium oxide, zinc oxide, calcium carbonate and calcium sulfate) dispersed therein and supports formed of a hydrophobic resin having a light reflective substance dispersed therein. Exemplary supports include baryta paper, polyethylene-coated paper, polypropylene base synthetic paper, and transparent supports having a reflective layer coated or reflective substance applied thereon, such as glass plates, polyester films (e.g., polyethylene terephthalate, cellulose triacetate and nitrocellulose), polyamide film, polycarbonate film, polystyrene film, vinyl chloride resin and the like.
Other reflective supports are those having a metallic surface providing specular reflection or secondary diffuse reflection. The preferred metallic surface has a spectral reflectivity of at least 0.5 in the visible wavelength range and is roughened or coated with metal powder to provide diffuse reflection. The metal used herein may be aluminum, tin, silver, magnesium or an alloy thereof and the surface may be that of a metal plate, metal foil or metal lamina obtained by rolling, evaporation or plating. A metallic surface obtained by vapor depositing a metal on another substrate is preferred among others. On the metallic surface a coating of water resistant resin, especially thermoplastic resin is preferably provided. That surface of the support opposite to the metallic surface may be provided with an antistatic layer. For the detail of such support, reference is made to JP-A 210346/1986, 24247/1988, 24251/1988 and 24255/1988. A choice may be made among these supports depending on a particular purpose.
Preferably, the light reflective substance is prepared by fully milling a white pigment in the presence of a surfactant. Pigment particles may be surface treated with di- to tetrahydric alcohols.
The white pigment fine particles have an occupied area ratio (%) per unit area. The occupied area ratio (%) is determined by dividing an area under observation into adjoining unit areas of 6 µm x 6 µm, measuring the area occupied by fine particles, that is, the area of fine particles projected on the unit area, and calculating the percentage (Ri %) of the occupied area relative to the unit area. A coefficient of variation of the occupied area ratio (%) is determined as a ratio s/R wherein R is an average of Ri and s is a standard deviation of Ri. The number (n) of unit areas under consideration is 6 or more. Then the coefficient of variation s/R is calculated according to the follow formula.
The white pigment fine particles preferably have a coefficient of variation of the occupied area ratio (%) of up to 0.15, especially up to 0.12. Particles are regarded as "uniformly" dispersed when the coefficient of variation is less than 0.08.
Moreover, the support of the photosensitive material used herein may be a white polyester support or a support having a white pigment-containing layer on the silver halide emulsion layer-bearing side for display purposes. Preferably the support is further provided with an anti-halation layer on the silver halide emulsion layer-coating side or the rear side. The support preferably has a transmission density of 0.35 to 0.8 in order that the display be observed with either reflected or transmitted light.
After exposure, the photosensitive material is subject to conventional color development. The color development is preferably carried out in a rapid processing fashion, more preferably in a very rapid processing fashion. In the case of color photography photosensitive material, color development is preferably followed by bleach-fixation for the purpose of rapid processing. Particularly when a high silver chloride emulsion as previously mentioned is used, the bleach-fixing solution is preferably at about pH 6.5 or lower, more preferably at about pH 6 or lower for facilitating desilvering and other purposes.
With respect to the silver halide emulsion, other substances (such as additives) and photographic constituent layers (including layer arrangement) applied to the photosensitive material used in the present invention and a method for processing the photosensitive material and processing chemicals used therein, reference is made to the patents described in the following Reference List, especially EP 0,355,660 A2 (JP-A 107011/1989).
Among the color couplers, other useful yellow couplers are those of the short wavelength type as described in JP-A 231451/1988, 123047/1988, 241547/1988, 173499/1989, 213648/1989 and 250944/1989.
In addition to the diphenylimidazole cyan couplers described in JP-A 33144/1990, useful cyan couplers include 3-hydroxypyridine cyan couplers described in EP 0,333,185 A2, especially, coupler (42) in the form of a 4-equivalent coupler modified into a 2-equivalent coupler by incorporating a chlorine decoupling radical, couplers (6) and (9) therein and cyclic active methylene cyan couplers described in JP-A 32260/1989, especially couplers 3, 8 and 34 therein.
The color developer which can be used in the practice of the invention generally works at a temperature of about 20 to 50°C, preferably about 30 to 45°C. The amount of developer replenished is generally about 20 to 600 ml, preferably about 30 to 300 ml, more preferably about 40 to 200 ml, most preferably about 50 to 150 ml per square meter of the photosensitive material although the lesser the better.
Preferably, the developing time is up to 45 seconds. The invention is advantageously applicable to rapid processing requiring a developing time within substantially 20 seconds. The developing time within substantially 20 seconds is the time taken from the entry of the photosensitive material into the developer tank to the entry thereof into a subsequent tank including a time for crossover passage between the tanks.
Washing or stabilizing step is preferably carried out at pH 4 to 10, more preferably at pH 5 to 8. The temperature may vary with the application and type of the photosensitive material and is generally about 30 to 45°C, preferably 35 to 42°C. The time is arbitrary although a shorter time is desired for reducing the processing time. Desired is a time of about 10 to 45 seconds, especially about 10 to 40 seconds. The replenishment amount is desirably smaller from the standpoints of running cost, exhausted solution to be discarded, and handling. Preferably, the replenishment amount is about 0.5 to 50 times, more preferably 2 to 15 times the carry-over from the preceding bath per unit area of photosensitive material. Differently stated, the replenishment amount is preferably up to 300 ml, more preferably up to 150 ml per square meter of photosensitive material. Replenishment may be either continuous or intermittent.
The liquid used in the washing and/or stabilizing step may be recycled to the preceding step. In one exemplary arrangement, the overflow of washing water in a multi-stage counter-current flow system designed to reduce the amount of washing water is channeled to the preceding bath or bleachfixing bath to which a bleach-fixing concentrate is replenished, thereby reducing the amount of exhausted solution to be discarded.
Next comes a drying step. In order to complete an image in a very rapid processing fashion according to the present invention, the drying time is desirably from about 20 to 40 seconds. The drying time may be reduced by properly designing the photosensitive material and the dryer. The drying time reducing means associated with photosensitive material is by reducing the amount of hydrophilic binder such as gelatin to thereby reduce the amount of water introduced into the film. From the standpoint of reducing the amount of water introduced into the film, it is also possible to take up water from the film with squeeze rollers or absorbent fabric immediately after emergence from the washing bath. The means associated with the dryer for quickening drying is, as a matter of course, to increase the temperature or to augment drying air. Further, drying can be accelerated by adjusting the angle of drying air flow to the photosensitive material and modifying the way of removal of air after drying.
Color paper has been referred to in the foregoing description although the image forming process of the present invention is also applicable to heat development color photosensitive material, which is described below.
The heat development color photosensitive material used herein generally comprises a photosensitive silver halide, a dye providing compound and a binder on a support. These components are most often added to a common layer, but may be added to separate layers if interaction between them is allowed. For example, a dye providing compound which is already colored may be disposed below a silver halide emulsion containing layer, preventing a lowering of sensitivity.
In order to provide a wide range of color on a chromaticity diagram using three primary colors of yellow, magenta and cyan, at least three silver halide emulsion layers having photosensitivity in different spectrum regions are used in combination. Exemplary are a combination of blue, green and red-sensitive layers, a combination of green, red and infrared-sensitive layers, and a combination of red, first infrared and second infrared-sensitive layers. These photosensitive layers may be arranged in any desired one of the orders known for conventional color photosensitive materials. Each photosensitive layer may be divided into two or more sublayers, if desired.
The silver halide which can be used in the heat development color photosensitive material in accordance with the invention includes silver chloride, silver bromide, silver iodobromide, silver chlorobromide, silver chloroiodide, and silver chloroiodobromide.
The silver halide emulsions used in the practice of the present invention may be either of the surface latent image type or of the internal latent image type. The internal latent image type emulsion is used as a direct reversal emulsion in combination with a nucleating agent or secondary exposure. Also employable is a so-called core-shell emulsion in which a core and a surface shell of a grain have different phases. The silver halide emulsion may be either mono-dispersed or multi-dispersed, and a mixture of mono-dispersed emulsions may also be used.
The grain size preferably ranges from about 0.1 to about 2 µm, more preferably from about 0.2 to about 1.5 µm. The crystal habit of silver halide grains may be of a cubic, octahedral, tetradecahedral, or plate shape having a high aspect ratio, but is not limited thereto.
More illustratively, use may be made of any of the silver halide emulsions described in USP 4,500,626, col. 50, USP 4,628,021, Research Disclosure, 1978, RD-17029, and JP-A 253159/1987.
The silver halide emulsions may be applied without post-ripening, but ordinarily after chemical sensitization. For chemical sensitization purpose, there may be used sulfur sensitization, reducing sensitization, noble metal sensitization and other processes which are well known in connection with the emulsions for photosensitive materials of the ordinary type, and combinations thereof. Such chemical sensitization may be carried out in the presence of a nitrogenous heterocyclic compound as disclosed in JP-A 253159/1987.
The amount of the photosensitive silver halide coated preferably ranges from about 1 mg to about 10 g of silver per square meter.
The silver halides used in the practice of the present invention may be spectrally sensitized with methine dyes and other dyes. The dyes useful for spectral sensitization include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes, and hemioxonol dyes. Illustrative examples are the sensitizing dyes disclosed in USP 4,617,257, JP-A 180550/1984 and 140335/1985 and RD 17029 (June 1978), pages 12-13. Other useful examples of the sensitizing dye are as previously described in conjunction with the color paper.
These sensitizing dyes may be used individually or as a combination thereof. A combination of sensitizing dyes is frequently used for supersensitization.
In addition to the sensitizing dye, the emulsion may contain a dye which itself has no spectral sensitization function or a compound which does not substantially absorb visible light, but is capable of supersensitization. Such supersensitizing compounds are disclosed in USP 3,615,641 and Japanese Patent Application No. 226294/1086.
These sensitizing dyes may be added to the emulsion during, before or after chemical ripening, or before or after nucleation of silver halide grains according to the teachings of USP 4,183,756 and 4,225,666. The amount of the sensitizing dye is generally from about 10⁻⁸ to about 10⁻² mol per mol of the silver halide.
In the heat developable color photosensitive material used herein, an organic metal salt may be used as an oxidizing agent along with the photosensitive silver halide. The use of organic metal salts is preferred for heat developable photosensitive elements. Organic silver salts are preferred among these organic metal salts.
Useful examples of the organic compounds which can be used to form the organic silver salt oxidizing agents are benzotriazoles, fatty acids and other compounds as described in USP 4,500,626, columns 52-53. Also useful are silver salts of carboxylic acids having an alkynyl radical such as silver phenylpropiolate as described in JP-A 113235/1985 and silver acetylene as described in JP-A 249044/1986. A mixture of two or more organic silver salts may be used. The organic silver salt is used in an amount of from about 0.01 to about 10 mol, preferably from about 0.01 to about 1 mol per mol of photosensitive silver halide. The combined amount of the photosensitive silver halide and organic silver salt coated preferably ranges from about 50 mg to about 10 grams of silver per square meter.
In the practice of the present invention, various antifoggants or photographic stabilizers may be used. Examples are azoles and azaindenes as described in RD-17643 (1978), nitrogenous carboxylic acids and phosphoric acids as described in JP-A 59-168442/1984, mercapto compounds and metal salts thereof as described in JP-A 111636/1984, and acetylene compounds as described in JP-A 87957/1987.
In the heat development system according to the present invention, there may be used any of the reducing agents which are known in the field of diffusion transfer type color photosensitive materials. Also included are dye providing substances having reducing nature as will be described later (in this case, another reducing agent may be additionally used). Also useful are reducing agent precursors which themselves have no reducing nature, but exert reducing nature under the action of nucleophilic reagents, alkali or heat during development step.

Examples of the reducing agent and precursor are described in the following patents.

USP 4,500,626, col. 49-50,
USP 4,483,914, col. 30-31,
USP 4,330,617 and 4,950,152
JP-A 140335/1985	40245/1982	138736/1981
178458/1984	53831/1984	182449/1984
182450/1984	119555/1985	128436/1985
128437/1985	128438/1985	128439/1985
198540/1985	181742/1985	259253/1986
244044/1987	131253/1987	131254/1987
131255/1987	131256/1987
EP-A 220746 A2

Also useful are combinations of reducing agents as disclosed in USP 3,039,869.
Where a non-diffusion reducing agent is used, an electron transfer agent and/or an electron transfer agent precursor may be used for promoting electron transfer between the non-diffusion reducing agent and developable silver halide, if desired. The electron transfer agents and precursors thereof may be selected from the above-mentioned reducing agents and precursors thereof. The electron transfer agent or precursors thereof should preferably have greater mobility than the non-diffusion reducing agent (electron donor). Useful electron transfer agents are 1-phenyl-3-pyrazolidones and aminophenols.
The non-diffusion reducing agent (electron donor) which is combined with the electron transfer agent may be selected from those of the above-mentioned reducing agents which are substantially immobile in a layer of photosensitive element, preferably hydroquinones, sulfonamidophenols, sulfonamidonaphthols, and the compounds described as the electron donor in JP-A 110827/1978, and dye providing substances having non-diffusion and reducing properties to be described later.
In the photosensitive material for the heat development system according to the present invention, the reducing agent is generally added in an amount of 0.001 to 20 mol, preferably 0.01 to 10 mol per mol of silver.
In a photosensitive material of the heat development system according to the present invention, there may be contained a compound which, when the photosensitive silver halide or silver ion is reduced into silver at elevated temperatures, produces or releases a mobile or diffusible dye in direct or inverse proportion to the reaction. These compounds are simply referred to as dye-providing compounds or substances.
Typical of the dye-providing substance are compounds capable of forming dyes through oxidative coupling reaction (or couplers). The couplers may be either four or two-equivalent couplers. Useful are two-equivalent couplers having a non-diffusion group as a splittable group and capable of forming a diffusible dye through oxidative coupling reaction. The non-diffusion group may form a polymeric chain. Illustrative examples of the color developing agents and couplers are described in, for example, T.H. James, "The Theory of the Photographic Process", 4th Ed., pages 291-334 and 354-361, and the following Japanese laid-open specifications .

JP-A 123533/1983 149046/1983 149047/1983

111148/1984 124399/1984 174835/1984

231539/1984 231540/1984 2950/1985

2951/1985 14242/1985 23474/1985

66249/1985
Another class of dye-providing substances includes compounds having the function of releasing or diffusing a diffusible dye imagewise. The compounds of this type may be represented by the following formula [L I]:

${[L I] (Dye-Y)}_{n} -Z$

wherein Dye represents a dye group, a temporarily wavelength shortened dye group or a dye precursor group; Y represents a valence bond or a connecting linkage; and Z represents a group which, in correspondence or counter-correspondence to photosensitive silver salt having a latent image distributed imagewise, produces a difference in diffusibility of the compound represented by (Dye-Y)_n-Z or releases Dye, the diffusibility of Dye released being different from that of the compound represented by (Dye-Y)_n-Z; and n represents an integer of 1 or 2, when n=2, the Dye-Y's may be the same or different.
Illustrative examples of the dye providing compound of formula [L I] are given below as classes (1) to (5). It is to be noted that the compounds of classes (1) to (3) are those forming a diffusible dye image (positive dye image) in counter proportion to the development of silver halide and the compounds of classes (4) to (5) are those forming a diffusible dye image (negative dye image) in proportion to the development of silver halide.
Class (1): Dye developing reagents in the form of a hydroquinone-type developing reagent having a dye moiety attached thereto are disclosed in USP 3,134,764; 3,362,819; 3,597,200; 3,544,545; and 3,482,972. These dye developing reagents are diffusible in an alkaline environment and become non-diffusible upon reaction with silver halide.
Class (2): Non-diffusible compounds which release diffusible dyes in an alkaline environment, but lose the ability upon reaction with silver halide are described in USP 4,503,137. Examples are substances which release a diffusible dye through intramolecular nucleophilic substitution reaction as disclosed in USP 3,980,479, and substances which release a diffusible dye through intramolecular rewind reaction of an isooxazolone ring as disclosed in USP 4,199,354.
Class (3) includes compounds which release a diffusible dye through reaction with the reducing agent which has left non-oxidized by development as disclosed in USP 4,559,290 and 4,783,396, EP 220746 A2, and Technical Report 87-6199.
Examples are compounds which release a diffusible dye through intramolecular nucleophilic substitution reaction after reduction as disclosed in USP 4,139,389 and 4,139,379, JP-A 185333/1984 and 84453/1982; compounds which release a diffusible dye through intramolecular electron transfer reaction after reduction as disclosed in USP 4,232,107, JP-A 101649/1984 and 88257/1986, RD 24025 (1984); compounds which release a diffusible dye through cleavage of a single bond after reduction as disclosed in German Patent 30 08 588A, JP-A 142530/1981, UPS 4,343,893 and 4,619,884; nitro compounds which release a diffusible dye upon receipt of an electron as disclosed in USP 4,450,223; and compounds which release a diffusible dye upon receipt of an electron as disclosed in USP 4,609,610.
Preferred examples are compounds having a N-X bond wherein X is an oxygen, sulfur or nitrogen atom and an electron attractive group in a molecule as disclosed in EP 220746 A2, Technical Report 87-6199, USP 4,783,396, JP-A 201653/1988 and 201654/1988; compounds having a SO₂-X bond wherein X is as defined above and an electron attractive group in a molecule as disclosed in Japanese Patent Application No. 106885/1987; compounds having a PO-X bond wherein X is as defined above and an electron attractive group in a molecule as disclosed in JP-A 271344/1988; and compounds having a C-X' bond wherein X' is the same as X or -SO₂- and an electron attractive group in a molecule as disclosed in JP-A 271341/1988. Also useful are compounds which release a diffusible dye through cleavage of a single bond after reduction due to π-bond conjugated with an electron accepting group as disclosed in JP-A 161237/1989 and 161342/1989.
More preferred are the compounds having a N-X bond and an electron attractive group in a molecule, with examples being described in EP 220746 A2 or USP 4,783,396 as compounds (1)-(3), (7)-(10), (12), (13), (15), (23)-(26), (31), (32), (35), (40), (41), (44), (53)-(59), (64), and (70) and in Technical Report 87-6199 as compounds (11) to (23).
Class (4) includes couplers having a diffusible dye as an eliminatable group and thus releasing a diffusible dye through reaction with an oxidant of a reducing agent, known as DDR couplers, as described in British Patent No. 1,330,524, JP-B 39165/1973; USP 3,443,940, 4,474,867 and 4,483,914.
Class (5) includes compounds (DRR couplers) which themselves have reducing nature to silver halide or organic silver salts and release a diffusible dye upon reduction of the silver halide or organic silver salts. Without a need for an extra reducing agent, the DRR couplers eliminate the serious problem that an image can be contaminated with oxidation decomposition products of a reducing agent. Typical examples are described in the following patents.

USP 3,443,939 3,725,062 3,728,113

3,928,312 4,053,312 4,055,428

4,336,322 4,500,626

JP-A 65839/1984 69839/1984 116537/1983

179840/1982 3819/1978 104343/1976

Examples of the DRR compound are described in USP 4,500,626, columns 22-44, with preferred ones being identified as compounds (1)-(3), (10)-(13), (16)-(19), (28)-(30), (33)-(35), (38)-(40), and (42)-(64). Also useful are those described in USP 4,639,408, columns 37-39.
There are available dye providing compounds other than the aforementioned couplers and compounds of formula [L I]. Such additional dye-providing compounds include dye-silver compounds in which an organic silver salt is combined with a dye (see Research Disclosure, May 1978, pages 54-58); azo dyes useful in heat development silver dye bleaching process (see USP 4,235,957 and Research Disclosure, April 1976, pages 30-32); and leuco dyes (see USP 3,985,565 and 4,022,617).
Hydrophobic additives like dye-providing compounds and non-diffusible reducing agents may be introduced into a layer of photosensitive material by any desired method, for example, by the method described in USP 2,322,027. Use may be made of high-boiling organic solvents as described in JP-A 83154/1984, 178451/1984, 178452/1984, 178453/1984, 178454/1984, 178455/1984, 178457/1984, optionally in combination with low-boiling organic solvents having a boiling point of 50 to 160°C.
The amount of the high-boiling organic solvent used is generally up to 10 grams, preferably up to 5 grams per gram of the dye-providing compound and up to 1 cc, preferably up to 0.5 cc, more preferably up to 0.3 cc per gram of the binder.
A dispersion method using a polymer as disclosed in JP-B 39853/1976 and JP-A 59943/1976 may be used.
In the case of substantially water-insoluble compounds, they may be dispersed in a binder as fine particles although any of the aforementioned addition methods may be used.
In dispersing hydrophobic compounds in hydrophilic colloids, a variety of surfactants may be used. Exemplary surfactants are found in JP-A 157636/1984, pages 37-38.
The photosensitive material according to the invention may further contain a compound capable of activating development and stabilizing an image at the same time. Examples are found in USP 4,500,626, columns 51-52.
In the system of forming images through diffusion transfer of dyes, a photosensitive material is used in combination with a dye fixing element. There are generally two typical forms, one form having photosensitive material and dye-fixing element separately applied on two separate supports and another form having both photosensitive material and dye-fixing element applied on a common support. With respect to the relation of the photosensitive material and the dye-fixing element to one another, to the support, and to a white reflective layer, reference may be made to USP 4,500,626, col. 57.
The dye-fixing element preferably used in the present invention has at least one layer containing a mordant and a binder. The mordant may be selected from those known in the photographic art, for example, the mordants described in USP 4,500,626, col. 58-59 and JP-A 88256/1986, pages 32-41; and the compounds described in JP-A 244043/1987 and 244036/1987. Also useful are dye accepting polymers as disclosed in USP 4,463,079. If desired, the dye-fixing element may be provided with any auxiliary layer, for example, a protective layer, peeling layer, and anti-curling layer, in addition to the above-mentioned layers. Provision of a protective layer is especially effective.
The binders employed in layers of the photosensitive material and dye-fixing material according to the present invention may be hydrophilic. Typical examples are described in JP-A 253159/1987, pages 26-28. More particularly, the preferred binder is a transparent or translucent hydrophilic binder, examples of which include natural substances, for example, proteins such as gelatin, gelatin derivatives and cellulose derivatives and polysaccharides such as starch, dextran, pluran, gum arabic, etc.; and synthetic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, acrylamide polymer, etc. Another example of the synthetic polymer is a polymer having a high water-absorbing capacity as described in JP-A 62-245260, that is, a homopolymer of a vinyl monomer having -COOM or -SO₃M wherein M is hydrogen or an alkali metal or a copolymer of such vinyl monomers or a copolymer of such a vinyl monomer with another vinyl monomer, for example, sodium methacrylate, ammonium methacrylate, and Sumikagel L-5H manufactured and sold by Sumitomo Chemical K.K. of Japan. The binders may be used alone or in admixture of two or more.
Particularly in a system of carrying out heat development in the presence of a small amount of water, the use of a highly water-absorbing polymer as mentioned above enables rapid water absorption. The highly water-absorbing polymer, when used in a dye-fixing layer or a protective layer therefor, is also effective in preventing the once transferred dye from being re-transferred from the dye-fixing element to any other layer.
The binders may be coated in amounts of up to about 20 grams per square meter, preferably up to about 10 grams per square meter, and most preferably up to about 7 grams per square meter of heat development color photosensitive material.
The hardeners employed in layers of the photosensitive material and dye-fixing material according to the present invention may be those hardeners described in USP 4,678,739, col. 41, and JP-A 116655/1984, 18942/1986 and 245261/1987. More illustratively, useful are aldehyde hardeners such as formaldehyde, aziridine hardeners, epoxy hardeners, vinyl sulfone hardeners such as N, N'-ethylene-bis(vinylsulfonylacetamide)ethane, N-methylol hardeners such as dimethylol urea, and high-molecular weight hardeners as described in JP-A 234157/1987.
An image formation promoter may be used in the photosensitive material and/or the dye-fixing material according to the present invention. The image formation promoters have the functions of promoting such reaction as redox reaction of a silver salt oxidizing agent with a reducing agent, formation of a dye from a dye-providing compound, decomposition of a dye or release of a mobile dye, and promoting transfer of a dye from a photosensitive material layer to a dye-fixing layer. From their physical-chemistry, they may be classified into bases, base precursors, nucleophilic compounds, high-boiling organic solvents (oils), thermal solvents, surfactants, and compounds capable of interacting with silver or silver ion. It should be noted that these compounds generally have multiple functions and thus possess some of the above-mentioned promoting effects combined. For further detail, reference is to be made to U.S. Patent No. 4,678,739, col. 38-40.
The base precursors include organic acid-base salts which are decarbonated upon heating and compounds which release amines through intramolecular nucleophilic substitution reaction, Lossen or Beckman rearrangement. Their examples are given in U.S. Patent No. 4,511,493 and JP-A 65038/1987.
In a system of carrying out heat development at the same time as dye transfer in the presence of a small amount of water, the base and/or base precursor is preferably contained in a dye-fixing element because the photosensitive material can have higher shelf stability.
Also useful are a combination of a difficultly soluble metal compound with a compound (complexing compound) capable of forming a complex with the metal ion of the metal compound as disclosed in EP 210,660 A and USP 4,740,445 as well as a compound capable of generating a base upon electrolysis as disclosed in JP-A 61-232451. The former method is particularly effective. It is advantageous to add the difficultly soluble metal compound and the complexing compound separately to the photosensitive material and the dye-fixing material.
A variety of development inhibitors may be used in the photosensitive material and/or the dye-fixing material according to the invention for the purpose of obtaining a consistent image irrespective of variations in processing temperature and time during heat development. By the development inhibitor is meant a compound capable of, immediately after development has proceeded to an optimum extent, quickly neutralizing or reacting with a base to reduce its concentration in the film to inhibit development, or a compound capable of, immediately after optimum development, interacting with silver or silver salt to retard development. Illustrative examples are acid precursors capable of releasing acid upon heating, electrophilic compounds capable of substitution reaction with a coexisting base upon heating, nitrogenous heterocyclic compounds, mercapto compounds and their precursors, and the like. Specific examples are disclosed in JP-A 253159/1987, pages 31-32.
A variety of polymer latexes may be contained in layers (including a back layer) of the photosensitive material or the dye-fixing element according to the invention for the purposes of improving film physical properties, for example, increasing dimensional stability and preventing curling, adhesion, film crazing, pressure sensitization or desensitization. Useful examples are the polymer latexes described in JP-A 245258/1987, 136648/1987, and 110066/1987. Particularly, addition of a polymer latex having a low glass transition temperature of up to 40°C to a mordant layer is useful in preventing crazing of the mordant layer. Addition of a polymer latex having a high glass transition temperature to a back layer is useful in preventing curling.
One or more layers of the photosensitive material and dye-fixing material may contain a plasticizer, a lubricant, or a high-boiling organic solvent as an agent for facilitating stripping of the photosensitive material from the dye-fixing material. Examples are found in JP-A 253159/1987 and 245253/1987.
Moreover, various silicone fluids may be used for the same purpose as above. The silicone fluids include dimethylsilocone fluid and modified silicone fluids of dimethylsiloxane having organic radicals incorporated therein. Examples are the modified silicone fluids described in "Modified Silicone Oil Technical Data", Shin-Etsu Silicone K.K., pages 16-18B, especially carboxymodified silicone (trade name X-22-3710). Also useful are the silicone fluids described in JP-A 215953/1987 and 46449/1988.
Various anti-fading agents may be used in the photosensitive material and dye-fixing material according to the invention. Exemplary anti-fading agents are antioxidants, UV absorbers and certain metal complexes. The antioxidants include chromans, coumarans, phenols (e.g., hindered phenols), hydroquinone derivatives, hindered amine derivatives, and spiroindanes. Also useful are the compounds described in JP-A 159644/1986. The UV absorbers include benzotriazoles (see USP 3,533,794, etc.), 4-thiazolidones (see USP 3,352,681, etc.), benzophenones (see JP-A 2784/1971, etc.), and the compounds described in JP-A 48535/1979, 136641/1987, and 88256/1986. Also useful are the compounds described in JP-A 260152/1987. Useful metal complexes are described in USP 4,241,155, USP 4,245,018, col. 3-36, USP 4,254,195, col. 3-8, JP-A 174741/1987, 88256/1986, pages 27-29, 199248/1988, and Japanese Patent Application Nos. 234103/1987 and 230595/1987. Other useful anti-fading agents are described in JP-A 215272/1987, pages 125-137.
For preventing the dye transferred to the dye-fixing material from fading, the anti-fading agent may be previously contained in the dye-fixing material or supplied to the dye-fixing material from the exterior, typically photosensitive material.
The above-mentioned antioxidants, UV absorbers and metal complexes may be used in combination.
Fluorescent brighteners may be used in the photosensitive material and dye-fixing material according to the present invention. Preferably, the brightener is incorporated in the dye-fixing material or supplied thereto from the exterior such as the photosensitive material. Exemplary brighteners are described in K. Veenkataraman, "The Chemistry of Synthetic Dyes", Vol. V, Chap. 8, and JP-A 143752/1986. Illustrative examples include stilbene compounds, coumarin compounds, biphenyl compounds, benzoxazolyl compounds, naphthalimide compounds, pyrazoline compounds, and carbostyryl compounds. The brightener may be combined with the anti-fading agent.
The photosensitive material and dye-fixing material may contain a surfactant in any layer thereof for various purposes including coating aid, stripping aid, lubrication, antistatic, and development acceleration. Useful surfactants are found in JP-A 173463/1987 and 183457/1987.
The photosensitive material and dye-fixing material may contain an organic fluorine compound in any layer thereof for various purposes including lubrication, antistatic, and stripping aid. Useful organic fluorine compounds are the fluoride surfactants described in JP-B 9053/1982, JP-A 20944/1986 and 135826/1987, and hydrophobic fluorine compounds including oily fluorine compounds such as fluorooil and solid fluorine compound resins such as tetrafluoroethylene resin.
The photosensitive material and dye-fixing material may contain a matte agent in any layer thereof. Exemplary matte agents include silicon dioxide, polyolefins, polymethacrylate and other compounds as described in JP-A 88256/1986, and beads of benzoguanamine resin, polycarbonate resin, AS resin or the like as described in JP-A 274944/1988 and 274952/1988.
The photosensitive material and dye-fixing material may contain thermal solvents, defoaming agents, antifungal and antibacterial agents, colloidal silica or the like in any layer thereof. These additives are described in JP-A 88256/1986.
The support used in the heat developable photosensitive material and dye-fixing material according to the present invention may be of any desired material which can withstand the processing temperature. Such materials include paper and polymers (film). Examples include films of polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, polystyrene, polypropylene, polyimide, and celluloses (e.g., triacetyl cellulose), those films having incorporated therein pigments such as titanium oxide, synthetic paper formed from polypropylene or the like, mix paper machined from synthetic resin pulp such as polyethylene and natural pulp, Yankee paper, baryta paper, coated paper (cast coated paper), metals, fabrics, and glass. These supports may be used alone or supports laminated with synthetic polymers such as polyethylene on one or both surfaces thereof be used. Also useful are the supports described in JP-A 253159/1987, pages 29-31.
The support on the surface may be coated with a hydrophilic binder and an antistatic agent such as a semiconductive metal oxide (e.g., alumina sol and tin oxide) and carbon black.
In heat developing the heat developable color photosensitive material according to the invention, the heating temperature is about 50°C to about 250°C, preferably about 80°C to about 180°C. Dye diffusion transfer may be effected at the same time as heat development or after the completion of heat development. In the latter case, the heating temperature in the transfer step may be from room temperature to the temperature used in the heat development, preferably from about 50°C to a temperature about 10°C lower than the heat development temperature.
In such heat developable color photosensitive material according to the invention, the layers coated on a support preferably total to a thickness of up to 15 µm in dry state. Such a thickness is effective for promoting dye transfer, thus forming images with sufficient sharpness.
Dye transfer can be induced solely by heat although a solvent may be used for promoting dye transfer. It is also useful to heat in the presence of a minor amount of solvent (especially water) to carry out development and transfer simultaneously or sequentially as disclosed in JP-A 218443/1984 and 238056/1986. In this mode, the heating temperature is from 50°C to below the boiling point of the solvent, for example, from 50°C to 100°C if the solvent is water.
Examples of the solvent which is used in order to promote development and/or allowing the diffusible dye to migrate to the dye-fixing layer include water and basic aqueous solutions containing inorganic alkali metal salts and organic bases (which may be those previously described for the image formation promoter). Also, low-boiling solvents and mixtures of a low-boiling solvent and water or a basic aqueous solution are useful. Surfactants, antifoggants, difficultly soluble metal salts, complexing compounds or the like may be contained in the solvents.
The solvent is used by applying it to the dye-fixing material or photosensitive material or both. The amount of the solvent used may be as small as below the weight of solvent corresponding to the maximum swollen volume of entire coatings, especially below the weight of solvent corresponding to the maximum swollen volume of entire coatings minus the dry weight of entire coatings.
Useful for applying the solvent to the photosensitive layer or dye-fixing layer is a method as disclosed in JP-A 147244/1986, page 26. It is also possible to seal the solvent in microcapsules and incorporate the microcapsules in the photosensitive material or dye-fixing material or both.
To promote dye transfer, a hydrophilic thermal solvent which is solid at room temperature, but soluble at high temperature may be incorporated into the photosensitive material or dye-fixing material or both. The layer into which the thermal solvent is incorporated is not limited and may be selected from emulsion layers, intermediate layer, protective layer and dye-fixing layer. Preferably, the thermal solvent is incorporated into the dye-fixing layer and/or layers contiguous thereto. Examples of the hydrophilic thermal solvent include ureas, pyridines, amides, sulfonamides, imides, alcohols, oximes, and heterocyclics. To promote dye transfer, a high-boiling organic solvent may be incorporated into the photosensitive material or dye-fixing material or both.
Heating required in the development and/or transfer step may be carried out by any desired means, for example, by contacting with heated blocks or plates, contacting with hot plates, hot presses, hot rollers, halide lamp heaters, infrared or far infrared lamp heaters, or by passing through a hot atmosphere. It is also possible to heat the photosensitive material or dye-fixing material by providing either of them with a resistance heating layer and conducting electricity thereacross. Useful heater layers are described in JP-A 145544/1986.
Pressure is applied in overlapping a photosensitive element and a dye-fixing material in close contact. Such pressure requirements and pressure application are described in JP-A 147244/1986.
For processing photosensitive materials according to the present invention, there may be used any of various developing apparatus including those described in JP-A 75147/1984, 177547/1984, 181353/1984 and 18951/1985 and Japanese U.M. Application Kokai No. 25944/1987.

EXAMPLE

Examples of the present invention are given below by way of illustration and not by way of limitation.

Example 1

Preparation of Emulsions (1)-(3)

To a thoroughly agitated aqueous solution of the composition shown in Table 2, Solutions I and II of the compositions shown in Table 3 were added over 15 minutes. Thereafter, Solutions III and IV of the compositions shown in Table 3 were added over 35 minutes. After water washing and desalting, 25 grams of gelatin was added to the solution, which was adjusted to pH 6.2 and pAg 8.2 and then chemically sensitized at 60°C. Using triethylthiourea and 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, optimum chemical sensitization was carried out such that the maximum sensitivity might be available at exposure for 10⁻⁴ second.
The resulting emulsions were monodispersed emulsions with their yield, grain size and crystal habit reported in Table 4.

Table 4

Emulsion (1) Emulsion (2) Emulsion (3)

Yield 610 g 630 g 615 g

Mean grain size 0.40 µm 0.20 µm 0.35 µm

Crystal habit cubic octahedral cubic

Preparation of a gelatin dispersion of zinc hydroxide

To 100 cc of 4% gelatin in water were added 12.55 grams of zinc hydroxide having a mean particle size of 0.25 µm, 1 gram of carboxymethyl cellulose and 0.1 gram of sodium polyacrylate as dispersants. The mixture was pulverized for 30 minutes in a mill using glass beads having an average diameter of 0.75 mm. Removal of the glass beads yielded a gelatin dispersion of zinc hydroxide.

Preparation of a gelatin dispersion of hydrophobic additives

The oily phase components shown in Table 5 were dissolved in 250 cc of ethyl acetate to form a uniform solution at 60°C. The aqueous phase components were heated at 60°C and added to the solution. The mixture was dispersed for 30 minutes in a dissolver by operating a disc of 8 cm in diameter at 5000 rpm. Post-water was added to the dispersion followed by agitation into a uniform dispersion. This dispersion is designated a gelatin dispersion of hydrophobic additives.
Using the above-prepared materials, a heat developable color photosensitive material No. 101 of the multilayer structure formulated in Table 6 was fabricated.
Shown below are structural formulae of the components in Tables 5 and 6 including yellow dye-providing compound (1), magenta dye-providing compound (2), cyan dye-providing compounds (3) and (4), filter dye (5), auxiliary developing agent (6), antifoggant (7), water-soluble polymer (8), surfactants (9) and (10), sensitizing dyes (12), (13) and (14), antifoggants (15), (16) and (17), high boiling solvents (18) and (19), surfactants (20), (21) and (22). Hardener (11) is 1,2-bis(vinylsulfonylacetamide)ethane.
Photosensitive material No. 102 was fabricated by the same procedure as No. 101 except that Emulsions (1), (2) and (3) are replaced by Emulsions (4), (5) and (5) which were prepared as described later, respectively.
Photosensitive material No. 103 was fabricated by the same procedure as No. 101 except that a mixture of 0.68 mg/m² of sensitizing dye (12) and 0.68 mg/m² sensitizing dye (34) was used instead of 1.3 mg/m² of sensitizing dye (12) in the fifth layer and 0.07 mg/m² sensitizing dye (35) was used instead of 0.06 mg/m² of sensitizing dye (13) in the third layer.
Photosensitive material No. 104 was fabricated by the same procedure as No. 103 except that Emulsions (1), (2) and (3) are replaced by Emulsions (4), (5) and (5), respectively.

Preparation of Emulsions (4)-(6)

Emulsion (4)

It was prepared by the same procedure as Emulsion (1) except that 25 grams of gelatin, 0.02 grams of KI and a temperature of 60°C were used in the aqueous solution of Table 2 and the addition time of Solutions I and II in Table 3 was reduced to 3 minutes. The emulsion had a mean grain size of 0.41 µm and a yield of 605 grams which were both approximately equal to Emulsion (1). But, the crystal habit was potato-shape or somewhat rounded cube.

Emulsion (5)

It was prepared by the same procedure as Emulsion (2) except that chemical sensitizing conditions were pH 6.9, pAg 8.8 and temperature 72°C and the triethylthiourea for chemical sensitization was replaced by sodium thiosulfate. The emulsion had a mean grain size of 0.20 µm, a yield of 631 grams, and an octahedral crystal habit.

Emulsion (6)

It was prepared by the same procedure as Emulsion (3) except that the temperature of the aqueous solution in Table 2 was lowered to 41°C and the chemical sensitization used sodium thiosulfate, chloroauric acid and 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene. The emulsion had a mean grain size of 0.27 µm, a yield of 621 grams, and a cubic crystal habit.

Preparation of dye-fixing material

A dye-fixing material designated R-1 was prepared according to the formulation shown in Table 7.

Shown below are structural formulae of the components in Table 7 including silicone oil (23), surfactants (24) and (25), mordant (28), high boiling solvent (29), surfactant (31), and hardener (32).

Water-soluble polymer (26): Sumikagel L5-H (Sumitomo Chemical K.K.)
Water-soluble polymer (27): dextran (molecular weight 70,000)
Brightener (30): 2,5-bis(5-tert-butylbenzoxazol(2))thiophene
Matter agent (33): benzoguanamine resin (mean particle size 15 µm)
Photosensitive material Nos. 101 to 104 were exposed to light using a semiconductor laser exposure apparatus as described in Japanese Patent Application No. 318351/1990. The exposure conditions are shown in Table 8.

Table 8

Exposure conditions
Scanning line density	800 dpi (32 rasters/mm)
Beam diameter	100±10 µm in main scanning direction
Beam diameter	80±10 um in auxiliary scanning direction
Exposure time	0.9 msec. per raster
Exposure wavelength	672,755.810 nm as measured for 0.5 mW emission at room temperature
Exposure quantity	1logE change per 2.5 cm in main scanning direction (maximum 80 erg/cm², minimum 1.2 erg/cm²)
Exposure changing mode	(A) luminous intensity modulation
Exposure changing mode	(B) luminous time modulation

Ten A4-size sheets of photosensitive material were successively exposed under the conditions of Table 8 whereupon the emission wavelength shifted from 672 nm to 675 nm in the fifth layer and from 755 nm to 758 nm in the third layer, which suggests the occurrence of a mode hopping phenomenon due to a temperature change as shown in FIG. 1. This phenomenon occurred in all of photosensitive material Nos. 101 to 104 and was observed in either of the intensity and time modulation modes.
Water, 12 ml/m², was supplied to the emulsion surface of the photosensitive material which had been exposed under the conditions of Table 8 and immediately thereafter, the photosensitive material was placed on an image receiving material such that their effective surfaces were in close contact. The assembly was passed through heat rollers such that the wet film was heated at a temperature of 90°C for 25 seconds. Then the image receiving material was stripped from the photosensitive material, obtaining transferred images of magenta, cyan and yellow on the image receiving material.
The transferred images of magenta and cyan were visually observed for density unevenness.
The transferred images were measured by an automatic recording densitometer, determining a maximum density (Dmax) and minimum density (Dmin) at the given exposure.
Instead of the laser exposure, the photosensitive materials were subjected to exposure for 10⁻³ second in a high illuminance sensitometer (EG & G Company) using a three color separation filter wedge allowing passage of light having a continuously varying density and wavelengths of 670 nm, 750 nm and 810 nm. Thereafter, the same procedures (development, transfer and density measurement) as above were carried out to determine a dynamic range (DR) and gamma (γ).
The results are shown in Table 9.
Additionally, photosensitive material Nos. 101 to 104 were measured for spectral sensitivity. The results are shown in FIG. 4. It is to be noted that the spectral sensitivity is expressed as a relative sensitivity (RS) based on a spectral sensitivity of 10 for the third layer of photosensitive material No. 103 at 755 nm.
The fifth (magenta) layer and the third (cyan) layer of photosensitive material Nos. 1 to 4 were determined for a variation of the logarithm of the relative sensitivity (RS) per nm in the emission wavelength region, that is, Δlog(RS)/nm and a deviation of the emission wavelength (λ) from the maximum spectral sensitivity wavelength (λmax), that is, (λmax - λ). The results are also shown in Table 9.
As mentioned above, the emission wavelength region of semiconductor laser for the exposure of the fifth layer is from 672 to 675 nm and the emission wavelength region of semiconductor laser for the exposure of the third layer is from 755 to 758 nm.
Photosensitive material Nos. 101 to 104 have the following λmax.
Photosensitive material Nos. 101 & 102
5th layer: λmax 686 nm
3rd layer: λmax 737 nm
Photosensitive material Nos. 103 & 104
5th layer: λmax 673 nm
3rd layer: λmax 752 nm
As seen from Table 9, the image forming process of the present invention is successful in forming images having high Dmax and free of unevenness.

Example 2

A silver halide color photography photosensitive material or color paper, designated No. 201, was prepared.
The silver halide emulsions of the respective layers are first described.

Cyan coupler-containing layer emulsion

Lime-treated gelatin, 32.0 grams, was added to 1000 ml of distilled water and dissolved therein at 40°C. To the solution adjusted to pH 3.8 with sulfuric acid, 5.5 grams of sodium chloride and 0.02 grams of N,N-dimethylimidazolidine-2-thion were added and the temperature was raised to 52.5°C. With vigorous stirring at 52.5°C, a solution of 62.5 grams of silver nitrate in 750 ml of distilled water and a solution of 21.5 grams of sodium chloride in 500 ml of distilled water were added to the solution over 40 minutes. Again with vigorous stirring at 52.5°C, a solution of 62.5 grams of silver nitrate in 500 ml of distilled water and a solution of 21.5 grams of sodium chloride in 300 ml of distilled water were added to the solution over 20 minutes. The aqueous sodium chloride solution added at this point contained 1x10⁻⁸ mol of potassium hexachloroiridate (IV) per mol of silver nitrate.
Upon observation under an electron microscope, the resulting emulsion was found to contain monodispersed cubic silver halide grains having a mean grain size of 0.46 µm in side length and a coefficient of variation of grain size distribution of 0.09.
The emulsion was desalted, washed with water, and combined with 0.2 grams of nucleic acid and a monodispersed silver bromide emulsion having a mean grain size of 0.05 µm (containing 1.2x10⁻⁵ mol of dipotassium hexachloroiridate (IV) per mol of silver bromide) in an amount of 1.0 mol% calculated as silver halide. It was chemically sensitized with about 2x10⁻⁶ mol per mol of Ag of triethylthiourea and finally combined with 7x10⁻⁶ mol per mol of Ag of compound (V-6) and 5x10⁻³ mol per mol of Ag of compound (F-1), both shown below.
The resulting emulsion was for an infrared-sensitive cyan color developing layer as a fifth layer.

Magenta coupler-containing layer emulsion

The above-mentioned preparation of cyan emulsion grains was repeated except that the temperature during formation of silver halide grains was changed to 50°C. There was obtained an emulsion containing monodispersed cubic silver halide grains having a mean grain size of 0.44 µm in side length and a coefficient of variation of grain size distribution of 0.08.
The emulsion was desalted, washed with water, and combined with 0.2 grams of nucleic acid and a monodispersed silver bromide emulsion having a mean grain size of 0.05 µm (containing 1.8x10⁻⁵ mol of dipotassium hexachloroiridate (IV) per mol of silver bromide) in an amount of 0.5 mol% calculated as silver halide. It was chemically sensitized with about 2.5x10⁻⁶ mol per mol of Ag of triethylthiourea and finally combined with 4.5x10⁻⁵ mol per mol of Ag of compound (V-3) and 5x10⁻³ mol per mol of Ag of compound (F-1).
The resulting emulsion was for an infrared-sensitive magenta color developing layer as a third layer.

Yellow coupler-containing layer emulsion

An emulsion was prepared by the same procedure as the magenta coupler-containing layer emulsion except that 1.2x10⁻⁴ mol per mol of Ag of compound (V-7) and 0.2x10⁻⁴ mol per mol of Ag of compound (V-8) were added instead of compound (V-3), and compound (F-1) was omitted.
The resulting emulsion was for a red-sensitive yellow color developing layer as a first layer.
To the coating solutions, compounds (D-1), (D-2), (D-3), (D-4), (D-5) and (D-6) shown below were added in amounts of 16.0 mg/m², 6.0 mg/m², 8.0 mg/m², 20.0 mg/m², 4.0 mg/m², and 22.0 mg/m², respectively, for the purposes of improving the safety to safe light and image sharpness.
It will be noted that some of these compounds are identical with the compounds previously illustrated for the dye. The correspondence is:

D-3 A-2

D-4 A-1

D-4 A-27

D-6 A-42
A multilayer color photosensitive material or multilayer color paper of the following layer arrangement was prepared by subjecting a paper support laminated with polyethylene on either surface to corona discharge treatment, forming a gelatin undercoat layer containing sodium dodecylbenzenesulfonate thereon, and applying photographic constituent layers thereon. The coating solutions were prepared as follows.

Preparation of first layer coating solution

In 27.2 cc of ethyl acetate, 4.1 grams of solvent (Solv-3) and 4.1 grams of solvent (Solv-7) were dissolved 19.1 grams of yellow coupler (ExY), 4.4 grams of color image stabilizer (Cpd-1) and 0.7 grams of color image stabilizer (Cpd-7). This solution was emulsion dispersed in 185 cc of a 10% gelatin aqueous solution containing 8 cc of 10% sodium dodecylbenzenesulfonate, obtaining an emulsified dispersion. This dispersion was combined with the above-prepared yellow coupler-containing layer emulsion and dissolved by mixing, obtaining a first coating solution of the composition shown below.
Coating solutions for the second through seventh layers were prepared in a similar manner. The gelatin hardener used in the respective layers was sodium 1-oxy-3,5-dichloro-s-triazine. Compounds (Cpd-10) and (Cpd-11) were added to the layers such that their total amounts were 25.0 mg/m² and 50.0 mg/m², respectively.
To each emulsion layer of yellow, magenta and cyan color developing layers, 8.0x10⁻⁴ per mol of silver halide of 1-(5-methylureidophenyl)-5-mercaptotetrazole was added. Additionally, 2.0x10⁻³ mol per mol of silver halide of a compound of the following formula was added to each of the magenta and cyan color developing layers.
Table 10 shows the layer arrangement and the composition of the respective layers of sample No. 201. The coating weight is expressed in g/m² except that the silver halide emulsion is given a coating weight based on silver.
The compounds used in the layers are shown later.
Color paper sample No. 202 was prepared by the same procedure as No. 201 except that in the preparation of the emulsion of each layer, 20 µg of rhodium chloride was added to the aqueous sodium chloride solution added for the first time during formation of silver halide grains.
Color paper sample No. 203 was prepared by the same procedure as No. 201 except that the spectral sensitizing dye used in the silver halide emulsion for the third layer was changed to compound (V-9) in an amount of 1.4x10⁻⁵ mol per mol of Ag.
Color paper sample No. 204 was prepared by the same procedure as No. 202 except that the spectral sensitizing dye used in the silver halide emulsion for the third layer was changed to compound (V-9) in an amount of 6.8x10⁻⁵ mol per mol of Ag.

These samples were exposed to spectrally separated light through a spectral sensitivity sensitometer (manufactured by Fuji Photo-Film Co., Ltd.) and processed in accordance with the procedure shown in Table 11.

Table 11

Processing step	Temperature	Time
Color development
	50°C	9 sec.
Bleach-fix	50°C	12 sec.
Rinse (1)	40°C	5 sec.
Rinse (2)	40°C	5 sec.
Rinse (3)	40°C	5 sec.
Drying	90°C	9 sec.

The color developer and bleach-fixer used in this procedure were of the compositions shown below.

Color developer

Ethylenediamine-N,N,N',N'-tetramethylene phosphonic acid		3.0 g
N,N-di(carboxymethyl)hydrazine		4.5 g
N,N-diethylhydroxylamine oxalate		2.0 g
Triethanol amine		8.5 g
Sodium sulfite		0.14 g
Potassium chloride		1.6 g
Potassium bromide		0.01 g
Potassium carbonate		25.0 g
N-ethyl-N-(b-methanesulfonamidethyl)-3-methyl-4-aminoaniline hydrogensulfate		5.0 g
Brightener (Whitex-4 by Sumitomo Chemical K.K.)		1.4 g
Water	totaling to	1000 ml
	pH adjusted to	10.5

Bleach-fixer

Ammonium thiosulfate (55wt%)		100 ml
Sodium sulfite		17.0 g
Ammonium iron (III) ethylenediaminetetraacetate		55.0 g
Disodium ethylenediaminetetraacetate		5.0 g
Ammonium bromide		40.0 g
Glacial acetic acid		9.0 g
Water	totaling to	1000 ml
	pH adjusted to	5.80

Rinse liquid

ion exchanged water (calcium ion less than 3 ppm and magnesium ion less than 2 ppm)

The thus processed sample Nos. 201 to 204 were measured for spectral sensitivity. The results are shown in FIG. 5. It is to be noted that the spectral sensitivity is expressed as a relative sensitivity based on a spectral sensitivity of 40 for the fifth layer at 830 nm.
As in Example 1, the third (magenta) layer of sample Nos. 201 to 204 were determined for Δlog(RS)/nm in the emission wavelength region (750-753 nm) and λmax - λ.
The third layers of sample Nos. 201 to 204 have the following λmax.
Photosensitive material Nos. 201 & 202
3rd layer: λmax 733 nm
Photosensitive material Nos. 203 & 204
3rd layer: λmax 748 nm
Also as in Example 1, sample Nos. 201 to 204 were determined for photographic properties. More particularly, the sample was exposed for 10⁻³ seconds to light from a xenon flash sensitometer (manufactured by EG & G Company) through an optical wedge and a separation filter allowing passage of light of specific wavelengths, and then processed as in Example 1. A characteristic curve (developed color density vs exposure quantity curve) corresponding to each layer was drawn. The transmission wavelengths of the separation filter were changed to 670 nm, 750 nm and 830 nm.
From these characteristic curves, the γ and dynamic range of each layer were determined as in Example 1. As previously defined, γ is the gradient of a straight line connecting a point on the curve which corresponds to a density equal to the fog density (Dmin) plus 0.5 and a point on the curve which corresponds to an exposure quantity equal to the corresponding exposure quantity plus 0.5. The dynamic range is a difference (ΔlogE) between a value which is smaller by 0.2 than the exposure quantity corresponding to a density equal to the fog density plus 0.1 and an exposure quantity corresponding to a density equal to the maximum density (Dmax) minus 0.1. (See FIGS. 2 and 3.)

The results are shown in Table 12.

Table 12

Sample		γ	ΔlogE	Δlog(RS)/nm	λmax - λ
201	Yellow layer	1.46	2.32	-	-
	Magenta layer	1.47	2.27	-0.036	- (20-17)nm
	Cyan layer	1.49	2.23	-	-
202	Yellow layer	2.35	1.57	-	-
	Magenta layer	2.38	1.49	-0.036	-(20-17)nm
	Cyan layer	2.44	1.43	-	-
203	Yellow layer	1.45	2.31	-	-
	Magenta layer	1.47	2.28	-0.0038	-(5-2)nm
	Cyan layer	1.48	2.21	-	-
204	Yellow layer	2.36	1.56	-	-
	Magenta layer	2.39	1.48	-0.0038	-(5-2)nm
	Cyan layer	2.46	1.41	-	-

Next, a developed color density unevenness test was carried out using a semiconductor laser exposure apparatus as used in Example 1. The semiconductor laser was changed to that having oscillation wavelengths of 672 nm, 750 nm and 830 nm. The image pattern was changed such that the three layers were exposed simultaneously and so as to provide a gradation that the three developed colors of cyan, magenta and yellow would balance to gray. The exposed samples were processed in accordance with the same processing procedure and solutions as used in the sensitometry. The resulting images were evaluated for density unevenness, with the results shown in Table 13.
Forty (40) sheets (100 mm x 148 mm) of color paper were successively exposed under the same conditions as the above-mentioned semiconductor laser exposure whereupon the emission wavelength for the magenta layer exposure shifted from 750 nm to 753 nm, which suggests the occurrence of a mode hopping phenomenon due to a temperature change as shown in FIG. 1. This phenomenon occurred in all of color paper sample Nos. 201 to 204 and was observed in either of the intensity and time modulation modes.
It is thus evident that when applied to color paper in accordance with the laser scanning exposure system, the image forming process of the invention is successful in providing scanning images of quality having a high maximum color development density and free of unevenness.
There has been described an image forming process which can form images having satisfactory density and quality without occurrence of image unevenness resulting from uneven exposure.

Claims

A process for forming an image in a photosensitive material having at least one photosensitive layer containing a photosensitive silver halide on a support, by imagewise exposing said at least one photosensitive layer using a modulatable light source, wherein
said light source is a semiconductor laser of the longitudinal single mode capable of emitting light at a wavelength which discontinuously varies in accordance with a variation in temperature or luminous quantity,
the emission wavelength during exposure is in such a range that the variation of the logarithm of the spectral sensitivity of said photosensitive layer per nm, Δlog(spectral sensitivity)/nm, is within ±0.015, and
said photosensitive layer has a gamma value of at least 1.5.
A process for forming an image in a photosensitive material having at least one photosensitive layer containing a photosensitive silver halide on a support, by imagewise exposing said at least one photosensitive layer using a modulatable light source, wherein
said light source is a semiconductor laser of the longitudinal single mode capable of emitting light at a wavelength which discontinuously varies in accordance with a variation in temperature or luminous quantity,
the emission wavelength during exposure is within a range of ±10 nm from the maximum spectral sensitivity wavelength (nm) of said photosensitive layer, and
said photosensitive layer has a gamma value of at least 1.5.
The image forming process of claim 2 wherein the emission wavelength during exposure is in such a range that the variation of the logarithm of the spectral sensitivity of said photosensitive layer per nm, Δlog(spectral sensitivity)/nm, is within ±0.015.
The image forming process of any one of claims 1 to 3 wherein said photosensitive layer has a dynamic range of exposure (E) of up to 2.0 as expressed in logE unit.