CA1097123A - Photographic material for use in the silver complex diffusion transfer process - Google Patents

Abstract

Abstract of the Disclosure A photographic material comprising successively:
(1) a silver halide emulsion layer, (2) a layer reflecting white light having a day coating weight in the range of 5 g/sq.m to 20 g/sq.m and containing in an organic hydrophilic colloid binder white inorganic pigment particles in such an amount that said layer has a diffuse transmission density of 0.30 to 0.50 and a reflection density of 0.15 to 0.20, (3) a subbing layer, (4) a hydrophobic transparent film support, (5) a subbing layer, and (6) an antihalation layer having a dry coating weight in the range of 4 g/sq.m to 15 g/sq.m and containing dispersed in an organic hydrophilic colloid binder a non-bleachable black antihalation substance in such an amount that said layer has a diffuse transmission density of at least 2.

Description

~g71~3 ~he presen-t invention relates to a photographic material suitable for use in the silver complex diffusion transfer process.
In photomechanical colour reproduction the information content of the coloured original is split up in colour separations, which are used to prepare the proper intermediate prints that serve as exposure modulators in the exposure of the photosensitive resist composition of the printing forms.
~he light-sensi-tive material used in the production of these colour separations is commonly a panchromatic silver halide emulsion ma-terial. ~ssential in the photomechanical reproduction is the screening of the separations to transform the tone values of a continuous tone record in a ~ariety of black dots, whose area is related to the continuous tone value.
As is known to those skilled in the art screened separations are used in the exposure of a photoresist material to produce halftone printing plates, which are made to print i with a cyan, magenta, yellow and optionally black ink res-pectively.
Simplified methods of screening of continuous tone images have become available. ~hese methods involve the use of so-called contact screens. Such screens are used to produce screened positives from continuous tone negatives but are likewise used for the preparation of direct screen separations from colour transparencies. Years ago the production of direct screen separations was not much used in practice for the main reason that it has not been possible to obtain GV.988 PC~

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1~7~Z3 sufficien-tl~ good tone rendition and colour saturation.
Nowadays direct halftone colour separations are made on pan-chroma-tic lith-films with recommended colour separation filters (see ~wald ~red ~oemer, ~he Handbook of Modern Halftone Photography (1965) published by Perfect-Graphic Arts Supply Co~pany P.O.Box 62 Demarest, ~.Y. 07627, page 94).
~he processing of halftone images in regular lith developers re~uires a lot of care and -the investment in automatic film processors is often required to ensure high P
10quality work. ~herefore it would be interesting to have at the disposal a direct-screening system in which halftone separation positives could be obtained from op-tionally pre-masked colour originals in one single step and with a pro-cessing system that is rather inexpensive, simple and con-venient. ~he silver complex diffusion transfer process (D~R-process) offers such advan-tages bu-t one cannot use any photographic silver halide material to obtain therewi-th the desired speed, screen dot quality and exposure latitude required in the production of screened images.
In order to meet the high quality demands of screened colour separations with regard to screen dot definition and tonal reproduction some measures for ensuring dot sharpness and sufficient exposure latitude have to be taken. ~or example the very high sharpness demands ask for a strong reduction of light scattering and counteraction of so-called halation by light reflexion at the support.
GV~988 PCl - 2 -~97~3 According to United States Patent Specification 3,091,535 of Clifford ~.Milner, Jr. issued May 28, 1963 which does not deal with the D~R-process, bleachable antihalation dyes and pigments for improving the image resolution have been used in translucent lith films.
~ he use of a bleachable antihalation substance is a conditio sine qua non for said film material since the overall colouration due to said substance masks the silver image, which has -to be viewed against the white background of the trans- -lucent layer of said material.
In the United States Patent Specification 3,629,054 of Lodewijk ~elix De Keyser, Joseph Antoine Herbots and Julius ~hiers, issued December 21, 1971 a silver halide emulsion ma-terial for use in the D~R-process has been described which comprises a composite film support consisting of a black-pigmented hydrophobic layer and a white-pigmented hydrophob:ic layer. ~he material contains in subsequent order a gelatin silver halide emulsion layer, a gelatin subbing layer, a plas-ticized hydrophobic cellulose triacetate layer co~taining tita-nium dioxide and a hydrophobic cellulose triacetate layer con-taining carbon black. ~he purpose of said layer containing carbon black is to protect the light-sensitive silver halide emulsion layer against actinic environmental light during carrying out the diffusion transfer process in daylight condi-tions when the light-sensitive material with its emulsion side in contact with an opaque image-receiving material GV.988 PCT - ~ -.. . . . .
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~L~97~Z3 leaves the camera. Since the white titanium dioxide layer during the exposure offers an image-wise light reflection into the silver halide emulsion la~er an increase in speed is ob-tained.

~ he incorporation of said white and black pigments in their respective hydrophobic layers poses serious problems with regard to brittleness and a sufficient pigment content.
In accordance wi-th the present invention a photographic ; silver halide emulsion material is provided, which is suited for the production of halftone images of high quality -through the D~R-process.
~he photographic material according -to the present invention comprises successively :
(1) a silver halide emulsion layer,

(2) a layer reflecting white light; having a dry coating weight in the range of 5 g/sq.m to 2C) g/sq.m and containing in an organic hydrophilic colloid binder white inorganic pigment particles in such an amount that said layer has a diffuse transmission density of 0.~0 to 0.50 and a reflection density of 0.~5 to 0.20,

(3) a subbing layer,

(4) a hydrophobic transparent film support,

(5) a subbing layer~ and

(6) an antihalation layer having a dry coatlng weight in the range of 4 g/sq.m to 15 g/sq.m and containing dispersed in an organic hydrophilic colloid binder a non-bleachable black antihalation substance in such an amount that said GV.988 PC~ - 4 -~ .

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1~973~23 layer has a diffuse transmission density of at least 2.
~ he "diffuse transmission densi-ty" is measured according to the requirements of American Standard PH 2. 19 - 1959.
~ y "reflection density" is meant "diffuse reflection density" which is measured according to the requirements of American Standard PH 2.17 - 1958.
According to a modified embodiment the antihalation layer mentioned under (6) is present immediately under the layer (2) reflecting white light, and the subbing layer (5) is covered with a clear coating on the basis of an organic hydrophilic colloid e.g. gelatin, which coating is intended as anti-curling layer.
r~he thickness of the pigment layer reflecting white light is preferably in the range of ~ to 6 ~m (micron), e.g. is 4 ~m.
~ he thickness of the black pigment layer is preferably in the range of 10 to 20 lum e.g. is 15 ~m.
As white inorganic pigment particles titanium dioxides, which may be of various crystalline forms, are preferably used. ~he rutile crystalline form gives the highest opacity for a given weight. However, not only pure titanium dioxides but likewise so-called coated titanium dioxide pigment particles may be used. Such means that the white titanium dioxide pigment has been modified by precipitation thereon of, e.g., hydrated aluminium oxide or of hydrated aluminium oxide together with hydrated silicon dioxide as described, e~g., in the United States Paten-t Specification 3,928,037 of ~ouis Maria GV.988 P~ - 5 -- . ... .

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7~LZ3 De Haes, issued December 23, 1975.
~ he titanium dioxide particles of the layer reflecting white light have preferably an average grain size in the ran~e of 50 to 500 nm and are used preferably in the range of 100 %
to 200 % by weight with respect to the hydrophilic binder.
~he hydrophilic binder may be any organic hydrophilic colloid that can form a water-permeable layer but is preferably gelatin.
Mixtures of gelatin with carbo~ymethylcellulose are very useful.
lhe dispersed non-bleachable antihalation substance is preferably carbon black e.g. lampblack that has preferably an average grain size in the range of 10 to 50 nm and is used preferably in the range of 5 to 40 % by weight with respect to the hydrophilic binder.
~ he support of the photographic material may be any conventional transparent hydrophobic film consisting, e.g., of a cellulose ester (e.g. cellulo~e triaceka-te, cellulose nitrate, cellulose acetate butyrate), a vinyl polymer (e.g.
polystyrene and copolymers of styrene) or a polyester, ~preferably a highly polymeric linear polyester of a dicar-boxylic acid with a dihydric alcohol (e.g. polyethylene terephthalate)~ ~hese supports in the present invention are provided at both sides with a subbing layer to improve the adherence of the hydrophilic binder-pigment coatings.
Suitable subbing layers for that purpose are described, e.g~, in the United States Patent Specifications 3,495,984 of Johannes Camiel Vanpoecke 9 Lodewijk ~elix De Eeyser and GV.988 PG~ - 6 -- , . ........................ .~ . ...... .
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11D97~Z3 Andre Jan Conix, 37495,985 of ~odewijk ~elix De Keyser, Andre Jan Conix and Joseph Antoine ~erbots, both issued ~ebruary 17, 1970, 3,L~34,840 of Bodewijk ~elix De Keyser, Andre Jan Conix and ~odewijk August Van Dessel, issued March 25, 1969, 3,788,856 of August Jean Van Paesschen, ~ucien Janbaptist Van Gossum and Jan Josef Priem, issued January 29, 1974 and United ~ingdom Patent ~pecification 1,234,755 filed September 28, 1967 by Gevaert-Agfa N.V.
~he thickness of the transparent support is preferably in the range of 0.05 mm to 0.2 mm.
Any type of negatively and positively working silver halide is suitable for preparing the emulsio~ layer, provided the silver halide grains are capable of being developed and complexed in the exposed and non-exposed areas respectively with the rapidity required in diffusion transfer processes.
Direct-positive silver halide emulsions can be used comprising silver halide grains that have been fogged, before or after coating of the emulsion on a support, by an overall exposure to ac-tinic radiation or preferably by chemical fogging e.g. by means of reducing agents. Upon image-wise exposure of the prefogged emulsions the development centres formed by said fogging are destroyed at the exposed areas and remain at the unexposed areas. By subsequent development a direct-positive image is formed. Particularly suitable direct-positive emulsions are those comprising electron~traps e.g.
compounds acting as electron-acceptors or desensitizers such GV.988 PC~ - 7 -~0~7~Z3 as desensitizing dyes which are adsorbed to the surface of the fogged silver halide grains. Other favourable direct-positive emulsions are those comprising silver halide grains containing internal centres promoting the deposition of photo-lytic silver formed physically or chemically during precipi-tatio~ of the silver halide grains. ~hese centres form the electron-traps. Fogging of the silver halide grains con-taining electron-traps in their interior or electron-acceptors at their surface preferably occurs by red~ction a~d gold fogging, more particularly by digestion in the presence of one or more reducing agents e.g. thiourea dioxide and gold com-pounds e.g. potassium chloroaurate and auric trichloride or by digestion at low pAg values in the presence of gold com-pounds.
More details about fogged direct positive silver halide emulsions can be found iIl British Patents 723,019 filed ~ebruary 5, 1952 by Gevaert Photo Producten N.V., 1,299,868 filed April 2, 1969 by Agfa-Gevaert A.G. and 1,427,525 filed July 13, 1972 by Agfa-Gevaert N.V., in US Patents 3,367,778 of Robert W.Berriman, issued ~ebruary 6, 1968, 3,501,305, 3,501,306, 3, 501, 307, all of B~rnard D.Illingsworth, issued March 17, 1970, 3,501,310 of Bernard D.Illingsworth and Harry ~.Spencer, issued March 17, 1970, 3,531,290 of Roberta A.
Litzerman, issued September 29, 1970, 3,537,858 of ~lbert W.Wise, issued No;vember 3, 1970 and 3,963,493 of Willy Joseph Vanassche, Herman Alberik Pattyn and Hendrik Alfons Borginon ~V .988 PC~ - 8 -. ~ . .
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issued June 15, 1976.
Another group of direct-positive silver halide emulsion materials comprises a so-called unfogged direct-positive silver halide emulsion, which has its sensitivity predominantly in the interior of the silver ~alide grains. Upon image-wise exposure of such emulsion a laten-t image forms predominantly in the in-terior of the silver halide grains. However, the development of such unfogged direct-positive silver halide emulsion is carried out under fogging conditions, wherein fog forms predominantly in the unexposed areas and a positive silver image results upon development. ~he unfogged, direct-positive silver halide emulsion material is characterized thereby that in the exposed parts no silver image is produced or only one of very poor density upon development by the use o~ a typical surface developer of the following composition :
p~hydro~yphenylglycine 10 g sodium carbonate-1-water 100 g water up to 1000 ml, whereas a silver image with sufficient density forms if an internal type developer of the following composition is used :
hydroquinone 15 g monomethyl-p-aminophenol sulphate 15 g anhydrous sodium sulphite 50 g potassium bromide 10 g sodium hydroxide 25 g sodium thiosulphate-5-water 20 g water up to 1000 ml.
G~.988 PC~ - 9 -.... . . .
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~13197~Z3 ~ he selective fogging of the image-wise exposed unfogged direct-positive emulsion materials can be carried out before or during development by a treatment with a fogging agent.
Suitable fogging agents are reducing agents such as hydrazine or substituted hydrazine compounds. Reference may be made -to US Patent ~pecification 3,227,552 of Keith ~. Whitmore issued January ~ 1966.
Unfogged direct-positive emulsions are e.g. those showing defects in the interior of the silver halide grains (ref. US
Patent Specification 2~592,250 of ~dward Philip Davey and Edward Bowes Knott, issued April 8, 1952) or silver halide emulsions wi-th covered-grain structure (ref. published German Patent Application 2,308,239 filed ~ebruary 20, 1973 by Agfa-Gevaert N.V.).
'~he silver halide of the emulsions used according to the present inven-tion may be any of the usual silver halides but preferably substantially consist of silver chloride e.g. at least 70 mole% of the silver halide is chloride, the remainder bei~g pre~erably bromide. ~he average grain-size is usually in the range of 200-300 nm.
In order to obtain a spectral sensitivity over the whole visible spectrum range (panchromatic sensitivity) the silver halide is spectrally sensitized with a mixture of known methine dyes that offer in a proper ratio a spectral sensitivity as equal as possible for each wavelength between 400 and 700 ~m.

GV~988 PC'l - ~0 -. . .. .
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~L097~Z3 ~ he amount of spectral sensitization dyes present per mole of silver halide is e.g. from 0.10 to 60 mg.
The hydrophilic colloid used as binder medium for the silver halide is preferably gelatin.
A suitable coverage of silver halide expressed in g of silver nitrate per sq.m is in the range of 0.5 g/sg.m to 5g~sq.m.
~ he present invention includes a process for the production of halftone images, which process comprises the steps of (1) photographically exposing to a light-image being a line or screened image a photographic material as defined above, (2) bringing the emulsion layer side of the exposed photographic material in contact with an image-receiving layer containing developing nuclei of an image receptor material in the presence of a liquid that makes the development of the exposed silver halide to take place and a silver halide complexing agent to efEect the trans~er by diEfusion of silver halide complexes from the photographic material into the image-receiving la~er to form a visible silver image therein, and 0 (3) separating the exposed photographic material from the image receptor material.
In preparing a direct screen image the exposure proceeds through a contact screen and a continuous tone originalO
When the receptor material contains two image receiving layers, one at each side of the support e.g. a transparent film, it does not matter which side is contacted and G~.988 PC~

1a~97:1Z3 conse~uently any error that may occur in contacting the receptor material with the emulsion layer of the photographic material is avoided.
~ hen halftone dot patterns obtained in the image receptor material by effecting the DTR-process with the photosensitive material of the present invention are examined with a magni-fying glass clear and sharp edges of the dots are observed.
In comparison with conventional lith material the obtained dot image configuration shows an improved sharpness of the dot edges.
~ or a same density in the dots the absolute amount of silver is considerably smaller in the images produced according to the invention than those produced in conventional lith films.
~ he binder of the image receiving layer containing developing nuclei in dispersed state may be any of the common hydrophilic binders used i~l the art, e.g. gelatin, carbox~methylcellulose, gum arabic, sodium alginate, propy-lene glycol ester of alginic acid, hydrox~ethyl starch, dextrine, hydroxyethylcellulose, polyvinylpyrrolidone, poly-styrene sulphonic acid, polyvinyl alcohol, etc.
It is preferred to use nickel sulphide nuclei or silver sulphide though other development nuclei can be used as well, e.g. sulphides of heavy metals such as sulphides of antimony, bismuth, cadmium, cobalt, lead and zinc. Other suitable salts are selenides, polyselenides, polysulphides, mercaptans and tin(II) halides. ~he complex salts of lead and zinc sulphides GV.988 PCl _ 12 -... . .
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are active both alone and when mi~ed with thioacetamide, dithiobiuret and dithio-oxamide. ~ogged silver halides can also be used as well as heavy metals themselves in colloidal form, preferably silver, gold, platinum, palladium and mercury may be used.
~ he image-receiving layer may be hardened so as to improve i-ts mechanical strength. Xardening egents for colloid layers include e.g. formaldehyde, glyoxal, mucochloric acid, and chrome alum. ~ardening may also be effected by incorporating a latent hardener in the colloid layer, whereby a hardener is released at the stage of applying the alkaline processing liquid.
~urther information on the composition of the image-receiving layer can be found in "Photographic Silver HalideDiffusion Processes" by André Rott and ~dith Weyde - ~he Focal Press, London and New York (~972), p. 50-65.
~ or carrying out the silver complex diffusion transfer process it is common practice to incorporate the developing agent~ into the light-sensitive silver halide emulsion layer and/or the image-receiving layer, or other water-permeable layers adjacent thereto.
In order to ensure a very good keepability, the present photosensitive material preferably does not contain a developing substance.
~ he D~R-processing liquid applied in the present invention is consequently preferably an alkaline liquid containing one or GV.988 PCT - 13 -- , . .

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~a~97~2~3 more developing agents and silver halide complexing compounds.
Suitable developing agents for the exposed silver halide are, e~g., hydro~uinone and 1-phenyl-3-pyrazolidinone and p-monomethylaminophenol. ~he development or activating liquid contains in the process for forming a silver image through the silver complex diffusion transfer process a silver halide solvent, e.g., a complexing compound such as an alkali metal or ammonium thiosulphate or thiocyanate, or ammonia.
Alternatively or in addition such complexing compound may be present in the image-receiving layer.
~ he exposure of -the light-sensitive material and the diffusion transfer proceed preferably with, or in the apparatus commercially available therefor and of which several types have been described in -the already mentioned book of A.Rott and E.Weyde.
~ he presen-t invention is illustrated by the following example. All percentages and ratios are by weight unless otherwise stated.

~xample - Preparation of the film material A with one pigment layer con-taining carbon black ____________________ A washed gelatino silver chlorobromide emulsion (98.2 mole of % chloride and 1.8 mole % of bromide) comprising an amount of silver halide equivalent to 150 g of silver nitrate per kg was fogged chemically by addition of potassium chloro-aurate (1.2 mg per mole of silver halide) at pH 7 and pAg 6 - GV.988 PCl - 14 -, ;

~7îz3 and by keeping the emulsion at 55C for 3 hours.
400 mg of pinacryptol yellow and 250 mg of the following desensitizing methine dye of the 2-phenyl-indole class described in the United States Patent 3,615,610 ~3 _ C = CH-CH=C ~ -CH~ I

were added to the fogged emulsion.
~he pH of the emulsion was lowered to 5 and the pAg raised to 9.5.
The emulsion was coa-ted at a silver halide coverage equivalent to 2.75 g of silver nitrate and 1.9 g of gelatin per sq.m, on a black antihalation layer carried b~ a subbed polyethylene terephthalate film support having a thickness of 0.1 mm.
~ he black antihalation coating was coated from the following mixture : -water 800 ml 35 k aqueous dispersion of lampblack (average grain size 30 nm) 21 g gelatin 64 g 12.5 % solution of saponine in a mixture of ethanol and water (80/20 by volume) 21 ml water to make 1 l.

GV.988 PC~ - 15 -. , -....... , ,, .

. : ~, . , The coating proceeded at a coverage of 1 litre/17.1 sq.m.
The diffuse transmission density of the black antihalation la~er was 2.60.
_ Preparation of the film material B with one pigment l~er containing titanium dioxide.

The silver halide emulsion prepared as described for film material A was coated at a same coverage on a white pigment coating, which itself had been applied from the following coating composition to a subbed polyethylene terephthalate support having a thickness of 0.1 mm :
water 200 ml ethanol 110 ml gelatin 53 g 16 % dispersion of titanium dioxide (rutile having an average grain size of 300 nm) in an aqueous gelatin solution containing 4.3 % of gelatin555 ml 12.5 % aqueous solution of saponine 25 ml water to make 1 l.
The coating was performed at a coverage of 1 litrej13.3 sq.m The white pigment coating had a diffuse transmission density o~ 0.43 and a reflection densi-ty of 0.16. The diffuse transmission densit~ was measured with a MACB~TH Quanta-~og Densitometer Model ~D-102 and the reflection density was measured with the MAGBE~X Quanta-~og Densitometer Model RD-219 (Quanta-~og is a tradename of Macbeth Corporation, ~ewburgh, NoY~ 12550 U.~.A.).

GV.988 PCT - 16 -., . , ~. , .

~og7~23 - Preparation of the ~ilm material C according to the invention with one pi~ment layer containing titanium dioxide and one pigment layer containing carbon black.
~ ilm material C was prepared in the same way as material B
with the difference, however, that the rear side of the support was coated with a black antihalation layer from the following composition :
water 600 ml 35 % aqueous dispersion of lampblack (average grain size 30 nm) 27 g gelatin 100 g ethanol 73 ml 12.5 % aqueous solution of saponine 13.5 ml 4 % aqueous solution of formaldehyde11 ml water to make 1 l.
~ he coating was performed at a coverage of 1 litre/14.5 sq.m.
~ he diffuse transmission density of the black antihalation layer was 3.00.

~ hese film materials were used under the same conditions in the ~R-process in combination with an image-receiving material prepared by coating a subbed polyethylene terephthalate film with the following coating composition :
water 800 ml gelatin 62 g aqueous dispersion of 0.20 % of colloidal silver sulphide and 11.6 % of gelatin 33 ml GV.988 PC~ - 17 -~L~97~:3 12.5 % solu-tion of saponine in a mixture of ethanol and water 80/20 by volume 35 ml 20 % aqueous formaldehyde solution 10 ml water to make 1 l ~he coating was per~ormed in such a way that after drying at 50C a layer having a dry weight of 54.~ g per sq.m was obtained.
~or compara-tive de-termina-tion of the exposure latitude of the above materials A, B, and a these materials were exposed in contact under the same conditions through superposed wedges, one of which being a screened wedge having in super-position thereon but turned over an angle of 90 the other wedge, which is a continuous tone step wedge having a constant of 0.15.
~he identically exposed ma-terials A, B, and C were D~R-processed in contact with the above receptor material b~ means of a developer solution containing the following ingredients :
water ~00 ml sodium hydroxide 10 g hydroquinone 10 g 1-phen~1-3-pyrazolidinone 1.5 g sodium thiosulphate 5 g potassium bromide 0.5 g sodium sulphite 50 g water to make 1 l.
In each step area of the prints obtained the point P
corresponding with 0 % dot value (no dots recognizable with a . GV.988 PC~ - 18 -. ., , . ;~. , ,~ , : .,, , ,- ~ ' ,'' - . .,, :, ;: , . ~
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~09~ 3 magnifying glass-enlargement factor 50x) and the point Q
corresponding with 100 % dot value (total blackening, no screen dots separately recognizable) were determined.
In order to illustrate the exposure latitude of said materials A, B and C the shift (S) (logarithmic values to the base 10 in the ordinate) of point P and point Q with respect to their position on the original screen wedge as a function of increasing exposure (rela-tive log E in the absciss) is given in the accompan~ing figures 1 to 3.
~he shift (S) stands for a change of the screen range at the side of point P and Q respectively as a function of relative log exposure.
Each of the figures therefore contains two curves, one (curve P) showing the shift of point P (corresponding with 0 %
dot value) and one (curve Q) showing the shift of point Q
(corresponding with 100 % dot value) both depending on rel. log E.
From figures 1, 2, and 3 relating to materials A, ~, and C respectively it can be learned that material A possesses the greatest exposure latitude, that material B through its large shift of point Q has but a poor exposure latitude, and that material C according to the present invention shows an unexpected relatively low shift for both points, which makes the material particularly useful for the production of separation images according to the D~R-process.
Besides, the relative speed values of the materials A, B7 and C in the present D~R imaging have been determined at optical GV.988 PC~ - 19 -: . . ~ . . . . .

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~97~L23 density 1.00. ~hese speed values expressed as relative log values were 1.97, 1.52, and ~.55 for the materials A, B, and C respectivel~. ~he higher the log value number, the lower the speed. A decrease of 0~3 corresponds with a doubling of speed.
As a result of the high speed value of material C and of its broad exposure latitude, this material C is especially suited for camera reproduction of halftone images such as screened colour separation images.

GV.988 PC~ - 20 -~, . .
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Claims (19)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows :

1. A photographic material comprising successively :
(1) a silver halide emulsion layer, (2) a layer reflecting white light having a dry coating weight in the range of 5 g/sq.m to 20 g/sq.m and containing in an organic hydrophilic colloid binder white inorganic pigment particles in such an amount that said layer has a diffuse transmission density of 0.30 to 0.50 and a reflection density of 0.15 to 0.20, (3) a subbing layer, (4) a hydrophobic transparent film support, (5) a subbing layer, and (6) an antihalation layer having a dry coating weight in the range of 4 g/sq.m to 15 g/sq.m and containing dispersed in an organic hydrophilic colloid binder a non-bleachable black antihalation substance in such an amount that said layer has a diffuse transmission density of at least 2.

2. A photographic material according to claim 1 with the modification that the antihalation layer mentioned under (6) is present immediately under the layer (2) reflecting white light and the subbing layer (5) is covered with a clear coating on the basis of an organic hydrophilic colloid.

3. A photographic material according to claim 1, wherein the thickness of the pigment layer reflecting white light is in the range of 3 to 6 µm.
GV.988 PCT CA - 21 -

4. A photographic material according to claim 1, wherein the thickness of the black pigment layer is in the range of 10 to 20 µm.

5. A photographic material according to claim 1, wherein the white inorganic pigment particles of layer (2) are titanium dioxide particles.

6. A photographic material according to claim 5, wherein the titanium dioxide particles have an average grain size in the range of 50 to 500 nm.

7. A photographic material according to claim 5, wherein said particles are used in the range of 100 to 200 %
by weight with respect to the hydrophilic binder.

8. A photographic material according to claim 1, wherein the hydrophilic binder is gelatin.

9. A photographic material according to claim 1, wherein the film support is a polyethyleneterephthalate support.

10. A photographic material according to claim 1, wherein the non-bleachable black antihalation substance is carbon black.

11. A photographic material according to claim 10, wherein the carbon black has an average grain size in the range of 10 to 50 nm.

12. A photographic material according to claim 10, wherein the carbon black is used in the range of 5 to 40 %
by weight with respect to the hydrophilic binder.

13. A photographic material according to claim 1, wherein the silver halide emulsion layer is prepared from a silver halide emulsion of the negative type.
GV.988 PCT CA - 22 -

14. A photographic material according to claim 1, wherein the silver halide emulsion layer is prepared from a silver halide emulsion of the direct-positive type containing fogged silver halide grains.

15. A photographic material according to claim 14, wherein the silver halide is a silver chloridebromide.

16. A photographic material according to claim 1, wherein the silver halide emulsion layer has a spectral sensitivity over the whole visible spectrum range.

17. A process for the production of halftone images, which process comprises the steps of :
(1) photographically exposing to a light-image being a line or screened image a photographic material as defined in claim 1, effecting the exposure in the direction of the side of the silver halide emulsion layer, (2) bringing the emulsion layer side of the exposed photographic material in contact with an image-receiving layer containing developing nuclei of an image receptor material in the presence of a liquid that makes the development of the exposed silver halide to take place and a silver halide complexing agent to effect the transfer by diffusion of silver halide complexes from the photographic material into the image-receiving layer to form a visible silver image therein, and (3) separating the exposed photographic material from the image receptor material.

GV.988 PCT CA - 23 -

18. A process according to claim 17, wherein the exposure proceeds through a contact screen and a continuous tone original.

19. A process according to claim 17, wherein the photo-graphic material comprises a direct-positive silver halide emulsion layer with fogged silver halide grains.

GV.988 PCT CA - 24 -