Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/72—Photosensitive compositions not covered by the groups G03C1/005 - G03C1/705
  • G03C1/73—Photosensitive compositions not covered by the groups G03C1/005 - G03C1/705 containing organic compounds
  • G03C1/732—Leuco dyes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
  • G03C7/02—Direct bleach-out processes; Materials therefor; Preparing or processing such materials

Definitions

• the present invention relates to light sensitive imageable layers , and in particular to photothermographic imageable layers comprising a nitrate salt, a leuco dye, a photobleachable dye, a binder, and an optional organic acid.
• An ultraviolet radiation sensitive initiator sensitized by said photobleachable dye may also be present.
• a great many photosensitive materials have been used in different imaging processes utilizing various photoinitiated phenomena such as photohardening of polymerizable materials (e.g., negative acting printing plates, photosolubilizing materials (e.g., positive acting printing plates), light initiated diazonium salt coupling reactions (e.g., diazonium microfilm), etc.
• a class of iodonium photoinitiators for both cationic and epoxy polymerization e.g., U.S. Pat. Nos. 4,026,705 and 3,981,897
• has also been proposed as equivalent to other photoinitiators in certain ethylenically unsaturated printing plate compositions e.g., U.S. Pat. No. 3,741,769).
• Photothermographic imaging systems are well known in the art. By definition, photothermographic systems are light sensitive imaging systems which are thermally developed. Photothermographic systems typically require development temperatures in the range of 80 to 200 °C. A number of imaging systems employ photosensitive compounds, leuco dyes or bleachable dyes, and nitrate salts to generate color images.
• Imaging systems which are sensitive to ultraviolet (UV) light, comprising a leuco dye or bleachable dye, nitrate ion, and diazonium salts in a binder are disclosed in U.S. Pat. No. 4,370,401.
• a leuco dye system a photothermographic, negative acting imaging system is provided; that is, the optical density in the final image is more dense in areas which are light struck than in areas which are not light struck.
• a photothermographic, positive acting imaging system is provided in those cases wherein a bleachable dye system is employed. That is, the optical density in the final image is more dense in areas which are not light struck than in areas which are light struck.
• the bleachable dye used in these cases does not seme in the role of a sensitizer or photoinitiator.
• compositions comprising a diazonium salt and leuco dye in a binder is disclosed in U.S. Pat. No. 4,394,433. These unamplafied compositions are positive-acting photothermographic compositions, and differ fundamentally from the compositions of the present invention, which are amplified by the action of a nitrate salt.
• U.S. Pat. No. 4,460,677 describes a thermally developable imaging system comprising a leuco dye, nitrate ion, and a spectrally sensitized organic compound having photolyzable halogen atoms.
• U.S. Pat. No. 4,386,154 describes a thermally developable imaging system comprising a leuco dye, a nitrate ion, and a spectrally sensitized compound selected from (1) aromatic iodonium salts and (2) compounds containing photolyzable halogen atoms. Both of these compositions act as a negative image forming systems in that the greatest image density is formed upon heat development in the light struck areas.
• the latent images are formed upon exposure to visible light and images are formed by heat development.
• the color fidelity and contrast of both of these systems is reduced by the presence of sensitizer stain, that is color due to unreacted sensitizer in regions not light exposed, and to colored by-products from reacted sensitizer in light exposed regions.
• This sensitizer stain aesthetically detracts from the image.
• the presence of (1) aromatic iodonium salts, or (2) compounds containing photolyzable halogen atoms generally leads to image printout on standing under ambient conditions on a time scale of minutes to days.
• Japanese Pat. No. 77,025,330 pertains to a UV light sensitive two component positive acting imaging composition comprised of an oxazine or phenothiazine leuco dye (BLMB), mono or disubstituted with a dialkylamino group, and an oxidizing agent such as nitrate ion.
• BLMB phenothiazine leuco dye
• Japanese Pat. No. 77,004,180 describes the use of triplet sensitizers for BLMB. Suitable sensitizers are aromatic carbonyl compounds and aromatic nitro compounds. Said patent describes both negative and positive systems, and is a counterpart to Japanese Pat. No. 77,025,330.
• the compositions described therein are UV light sensitive whereas the compositions of this invention are visible light sensitive through the entire visible spectrum of 400 - 700 nm. The compounds described are not equivalent to the compounds used in this invention.
• Japanese Pat. No. 76,035,847 describes photosensitive heat fixable recording materials containing a free radical producing organic halogen compound, leuco dye and a base. This is a negative acting system which contains no oxidizer.
• Japanese Pat. No. 77,025,088 describes photosensitive compositions containing an acid sensitive leuco dye (e.g., naphthospiropyran), a photochemical acid generating agent which is a mixture of an organic halide (e.g., CBr4), with a furan containing compound.
• an acid sensitive leuco dye e.g., naphthospiropyran
• a photochemical acid generating agent which is a mixture of an organic halide (e.g., CBr4), with a furan containing compound.
• Japanese Pat. No. 79,001,453 describes a photothermographic material which contains an oxidizer, a compound which reacts with the oxidizer to change or develop color, and a compound which deactivates the color developer either in exposed or unexposed regions. Images can be either positive or negative, and do not employ sensitizers or diaryliodonium salts or organic compounds having photolyzable halogen atoms, which are components of the present invention, and which activate rather than deactivate color development.
• the light sensitive materials used were colorless or nearly colorless aryl quinones and ultraviolet light sources were used. Additionally, the light sensitive materials used were not photobleachable.
• Decolorizable imaging systems comprising a binder, nitrate salt, acid, and dyes are disclosed in U.S. Pat. Nos. 4,336,323 and 4,373,020. These systems are particularly useful as antihalation layers in photothermographic systems where the development temperature acts to bleach the dye.
• photobleachable dyes including o -nitroarylidene dyes as antihalation or acutance dyes is known in the art: U.S. Pat. Nos. 4,111,699; 4,271,263; 4,088,497; 4,033,948; 4,028,113; 3,988,156; 3,988,154; 3,984,248; 3,615,432 (RE28,225).
• the use of photobleachable dyes in this manner is unrelated to their function in the present invention. Additionally, it was found that o -nitroarylidene dyes are desensitizing to silver halide imaging systems.
• U.S. Pat. No. 4,713,312 teaches the use of photobleachable sensitizers in the range of 390-500 nm for free radical polymerization to reduce background sensitizer stain in an imaging system based on photosensitive microcapsules. Said patent does not provide for complete removal of residual sensitizer stain since sensitizers used in it covering the range 500-700 nm, necessary for full color reproduction, are not photobleachable, and hence add stain to the background in unirradiated areas.
• this invention provides photothermographic imageable layers comprising a nitrate salt, a leuco dye, photobleachable dye, a binder, and an optional organic acid.
• This invention provides imageable layers comprised of a nitrate salt, a leuco dye, and a photobleachable dye. These compositions are normally carried by a binder such as a polymeric binder which may also contain an organic acid.
• the imageable layers of this invention have reduced residual sensitizer stain both in exposed regions of the composition, and following an optional post-development blanket irradiation, in unexposed regions as well. Further, subsequent exposure of said blanket irradiated imageable layer to ammonia vapor semes to thermally stabilize (fix) said layer.
• Sensitivity to visible light that is the exposure necessary to enable the generation of images
• Sensitivity to visible light that is the exposure necessary to enable the generation of images
• This invention provides a negative-acting photothermographic imaging system which produces clean and stable images by overcoming the deficiencies of the prior art which are (1) the need to sensitize a UV sensitive photoinitiator, and (2) image instability (printout), caused by thermal interaction of said UV sensitive photoinitiator with the leuco dye.
• This invention is achieved by providing a novel photothermographic imageable layer which comprises a binder, leuco dye, nitrate ion, photobleachable dye, and an optional organic acid.
• a novel photothermographic imageable layer which comprises a binder, leuco dye, nitrate ion, photobleachable dye, and an optional organic acid.
• the application of heat develops the image by oxidizing the leuco dye more rapidly in either the exposed or unexposed region to afford a negative positive image, respectively.
• An image results due to a differential rate of oxidation occurring in exposed and unexposed regions.
• Latent images are formed upon exposure to visible light and stable images are then formed by heat development, a subsequent optional blanket light exposure, and a subsequent exposure to ammonia vapor. No wet processing steps are needed.
• the four required ingredients are (1) a photobleachable dye, (2) a nitrate salt, (3) a leuco dye, and (4) a polymeric resin (binder).
• An acidic material constitutes a preferred fifth ingredient.
• photobleachable means that upon exposure to actinic radiation between about 350 and about 1100 nm the dye is converted to a colorless or nearly colorless form (i.e., the molar absorptivity is reduced by at least a factor of 5).
• Photobleachable sensitizers useful in the present invention bleach at least 10%, and preferably bleach at least 25% and more preferably at least 50% when exposed to the following conditions: a film of polyethylene terephthalate (4 mil thickness) is coated with the sensitizer in question so as to create a colored film with an absorbance of from 0.1 to 0.6, whereupon said colored film is then placed onto the Fresnel lens of a 3M brand Model 213 Overhead Projector and exposed to light therefrom for 5 minutes.
• the photobleachable sensitizers are said to bleach at a given percentage when the layer containing the sensitizer decreases absorbance (absorption intensity) by a given percentage at the longest wavelength absorption band maximmum.
• This absorbance may be measured either by percentage reduction in optical density provided by the sensitizer or by measurement of the percentage of radiation actually absorbed.
• the overhead projector uses a single General Electric 82V ENX 360W projection bulb having a color temperature of 33300°K.
• the light intensity on the mage stage is 0.46W/cm2 ⁇ 0.05W/cm2.
• arylidene refers to a group formed by an aryl group and a methine linkage (e.g., benzylidene, cinnamylidene, etc.).
• o -Nitro-substituted arylidene dyes contain an o -nitro-substituted aryl group joined through a methine chain linkage to a basic heterocyclic nucleus containing an electron-donating atom, typically a nitrogen, oxygen, or sulfur. The number of atoms joining the electron donating atom and the aryl group is an even or odd number.
• the o -nitro-substituted aryl group is joined through an acyclic methine chain containing an even or odd number of methine groups to a 5- or 6-membered basic, cyanine dye-type heterocyclic nucleus.
• the heterocyclic nucleus can have additional carbocyclic and heterocyclic rings fused thereto.
• the o -nitro-substituted aryl group can contain a phenyl or heterocyclic nucleus, or can contain a nucleus formed by fused aromatic or heteroaromatic rings, such as naphthyl and the like.
• 3,984,248, 3,988,154, 3,988,156, and 4,271,263 disclose certain members of the o -nitroarylidene dyes as acutance agents in thermally-developable photosensitive compositions.
• U.S. Pat. No. 4,095,981 discloses certain members of the o -nitroarylidene dyes as energy sensitive dyes in silver based photographic or photothermographic materials.
• the o-nitro-substituted dyes have three general formulas.
• A represents an electron donating moiety, such as oxygen (-O-), sulfur (-S-), or
• R1 represents (1) an alkyl group having from 1 to 18 carbon atoms and preferably a lower alkyl group having from 1 to 4 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, sec -butyl, isobutyl, tert -butyl); a sulfoalkyl group, preferably sulfo lower alkyl containing from 1 to 4 carbon atoms in the alkyl moiety (e.g., ⁇ -sulfoethyl, ⁇ -sulfopropyl, ⁇ -sulfobutyl, etc.); a carboxyalkyl group, preferably a carboxy lower alkyl containing from 1 to 4 carbon atoms in the alkyl moiety (e.g., ⁇ -carboxyethyl, ⁇ -carboxpropyl, ⁇ -carboxybutyl, etc.); a sulfatoal
• Y represents the atoms necessary to complete an aryl (preferably phenyl or naphthyl) ring which is o -nitro-substituted and preferably is also p -substituted with a nitro or other electron withdrawing group and which can have other substituents attached to it and other carbocyclic rings fused to it (e.g., 2-nitrophenyl, 2,4-dinitrophenyl, 2,6-dinitrophenyl, 2,4,6-trinitrophenyl, 2-nitronaphthyl, 2,4-dinitronaphthyl, 2-nitro-4-cyanophenyl, 2-nitro-4-ethoxycarbonylphenyl, 2-nitro-4-trifluoromethylphenyl, and the like); and
• Z represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the type used in cyanine dyes containing 5 or 6 atoms in the heterocyclic ring containing the electron-donating atom of the formula which ring can contain a second hetero atom such as oxygen, nitrogen, selenium, or sulfur.
• the heterocyclic nucleus preferably is selected from the group consisting of thiazole nucleus including substituted and unsubstituted benzothiazole and naphthothiazole nuclei and like (e.g., Othiazole, 4-methylthiazole, 4-phenylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)thiazole, benzothiazole, 4-chlorobenzothiazole, 4-methylbenzothiazole, 4-methoxybenzothiazole, 4-ethoxybenzothiazole, 4-phenylbenzothiazole, 5-chlorobenzothiazole, 5-bromobenzothiazole, 5-methylbenzophenylbenzothiazole, 5-methoxybenzothiazole, 5-ethoxybenzothiazole, 6-chlorobenzothiazole, 6-ethoxybenzothiazole, 5-methoxynaphtha[2,3- d ]thiazole, 5-nitrobenzothi
• the spectrally sensitive initiator is an aryl nitrone shown by Formula 4:
• the photobleachable dye should be present as at least 0.05 percent by weight of the dried imageable layer, up to 1.5 percent by weight or more. Preferably, they are present at from 0.075 to 1.25 percent by weight of the layer and most preferably from 0.1 to 1.0 percent.
• Any natural or synthetic water-insoluble polymeric binder may be used in the practice of this invention.
• Organic polymeric resins preferably thermoplastic resins although thermoset resins may be used) are generally preferred. Where speed is important, water-insoluble, water impermeable, water resistant polymers should be used and an acid should be added to the system to increase the rate of colorizing (i.e., leuco dye oxidation).
• Such resins as phenoxy resins, polyesters, polyvinyl resins, polycarbonates, polyamides, polyvinyl acetals, polyvinylidene chloride, polyacrylates, cellulose esters, copolymers and blends of these classes of resins, and others have been used with particular success.
• the resin should be able to withstand those conditions. Generally, it is preferred that the polymer not decompose or lose its structural integrity at 200 °F (93 °C) for 30 seconds and most preferred that it not decompose or lose its structural integrity at 260 °F (127 °C).
• Preferred polymers include polyvinylidene chloride resins (e.g., SaranTM supplied by Dow Chemical, Midland, MI), phenoxy resins (e.g., PKHHTM and PAHJTM supplied by Union Carbide, Ralphensack, NJ ), and polyvinyl formals (e.g., FormvarTM supplied by Monsanto Chemical, St. Louis, MO).
• polyvinylidene chloride resins e.g., SaranTM supplied by Dow Chemical, Midland, MI
• phenoxy resins e.g., PKHHTM and PAHJTM supplied by Union Carbide, Hackensack, NJ
• polyvinyl formals e.g., FormvarTM supplied by Monsanto Chemical, St. Louis, MO
• the binder semes a number of additionally important purposes in the constructions of the present invention.
• the imageable materials are protected from ambient conditions such as moisture.
• the consistency of the coating and its image quality are improved.
• the durability of the final image is also significantly improved.
• the binder should be present as at least about 25% by weight of ingredients in the layer, more preferably as 50% or 70% by weight and most preferably as at least about 80% by weight of dry ingredients (i.e., excluding solvents in the layer).
• a generally useful range is 30-98 percent by weight binder with 75 to 95 percent preferred.
• Nitrate salts themselves are well known. They may be supplied as various chemical compounds, but are desirably provided as a metal salt, and most preferably provided as a hydrated metal salt. Other ions which are ordinarily good oxidizing ions such as nitrite, chlorate, iodate, perchlorate, periodate, and persulfate do not provide comparable results. Extremely active oxidizing agents, such as iodate, even used in relatively smaller proportions to prevent complete and immediate oxidation or colorization of the dyes do not perform nearly as well as nitrate ion compositions. The performance of nitrate is so far superior to any other ion that it is apparently unique in the practice of the present invention.
• nitrate salts into the composition are satisfactory, for example, organic salts, metal salts, acid salts, mixtures of acids and salts, and other means of supplying the ion are useful.
• nitrates of zinc, cadmium, potassium, calcium, zirconyl (ZrO2), nickel, aluminum, chromium, iron, copper, magnesium, lithium, lead and cobalt, ammonium nitrate, cerous ammonium nitrate, and combinations of the above may be used.
• the nitrate salt component of the present invention is desirably present in a form within the imaging layer so the oxidizing quantities of HNO3, NO, NO2, or N2O4 will be provided within the layer when it is heated to a temperature no greater than 200 °C for 60 seconds and preferably no greater than 160 °C for 60 or most preferably 30 seconds. This may be accomplished with many different types of salts, both organic and inorganic, and in variously different types of constructions.
• thermal oxidant providing nitrate salts is to provide a hydrated nitrate salt such as magnesium nitrate hexahydrate (Mg(NO3)2 x 6H2O).
• non-hydrated salts such as ammonium nitrate, pyridinium nitrate, and guanidinium nitrate in an acidic environment are also capable of providing the oxidizing capability necessary for practice of the present invention.
• organic salts in non-alkaline environments are also quite useful in the practice of the present invention.
• nitrated quaternary ammonium salts such as guanidinium nitrate work quite well in acid environments, but will not provide any useful image in a basic environment.
• the alkaline environment causes any oxidizing agent (e.g., HNO3, NO, NO2, and/or N2O4) which is liberated from the nitrate salt to be neutralized so as to prevent oxidation of the leuco dyes. For this reason it is preferred to have an acidic environment for the nitrate salt.
• oxidizing agent e.g., HNO3, NO, NO2, and/or N2O4
• HNO3, NO, NO2, and/or N2O4 oxidizing agent
• the dye and a non-nitrate (preferably halide) salt of the cation may be co-dissolved in a solution. If the salt oxidizes the dye spontaneously (within two minutes) at room temperature, it is a reactive salt.
• a reactive salt such salts as silver nitrate, in which the cation itself is a strong oxidizing agent, is a reactive salt.
• Ceric nitrate is also reactive, while hydrated cerous nitrate is not.
• Preferred salts are the hydrated metal salts such as nickel nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, ferric nitrate nonahydrate, cupric nitrate trihydrate, zinc nitrate hexahydrate, cadmium nitrate tetrahydrate, bismuth nitrate pentahydrate, thorium nitrate tetrahydrate, cobalt nitrate hexahydrate, gadolinium or lanthanum nitrate nonahydrate, mixtures of these hydrated nitrates and the like.
• Nonhydrated (e.g., lithium nitrate) or organic nitrates may be admixed therewith.
• Organic nitrates are also quite useful in the practice of the present invention. These nitrates are usually in the form of quarternary nitrogen containing compounds such as guanidinium nitrate, pyridinium nitrate, and the like. It is preferred to have at least 0. 10 moles of nitrate ion per mole of leuco dye. It is more preferred to have at least 0.30 or 0.50 moles of ion per mole of dye.
• the nitrate ordinarily constitutes from 0.05 to 10 percent by weight of the imaging layer, preferably 0.1 to 10 percent and most preferably 0.5 to 8 percent by weight.
• Leuco dyes are well known. These are colorless compounds which when subjected to an oxidation reaction form colored dyes. These leuco dyes are well described in the art (e.g., U.S. Pat. No. 3,974,147; Mees, C.E.K.; James, R. The Theory of Photographic Process , 3rd Ed.; MacMillan: New York,; pp 283-284, 390-391; and Kosar, J. Light-Sensitive Systems ; John Wiley and Sons: New York, 1965; pp 367, 370-380, 406. Only those leuco dyes which can be converted to colored dyes by oxidation are useful in the practice of the present invention.
• the preferred leuco dyes are the acylated leuco diazine, phenoxazine, and phenothiazine dyes examples of which are disclosed in U.S. Pat. Nos. 4,460,677, 4,647,525, and G.B. Pat. No. 1,271,289.
• Acid or base sensitive dyes such as phenolphthalein and other indicator dyes are not useful in the present invention.
• Indicator dyes form only transient images and are too sensitive to changes in the environment.
• the leuco dye should be present as at least about 0.3 percent by weight of the total weight of the light sensitive layer, preferably at least 1 percent by weight, and most preferably at least 2 percent to 10 percent or more (e.g., 15 percent) by weight of the dry weight of the imageable layer. About 10 mole percent of the nitrate/leuco dye is minimally used, with 20 to 80 mole percent preferred and from 35 to 65 mole percent most preferred. Molar percentages of nitrate/dye in excess of 100% are definitely useful.
• the leuco dye ordinarily constitutes from 0.5 to 15 percent by weight of the imaging layer preferably 2 to 8 percent.
• initiator refers to either a diaryliodonium salt, or an photolyzable organic halogen compound. Each of the two classes of initiators are known in the art.
• diaryliodonium salts of the present invention may be generally described by the formulae: wherein
• alkyl group includes ether groups (e.g., CH3-CH2-CH2-O-CH2-) , haloalkyls, nitroalkyls, carboxy alkyls, hydroxy alkyls, etc. while the term alkyl includes only hydrocarbons. Substituents which react with active ingredients, such as very strong reducing or oxidizing substituents, would of course be excluded as not being sensitometrically inert or harmless.
• the photolyzable organic halogen compounds are those that upon exposure to radiation dissociate at one or more carbon-halogen bonds to form free radicals.
• the carbon-halogen bond dissociation energy should be between about 40 and 70 kilocalories per mole as taught in U.S. Pat. Nos. 3,515,552 and 3,536,481.
• Preferred halogen compounds are nongaseous at room temperature and have a polarographic half-wave reduction potential greater than about -0.9 V as described in U.S. Pat. Nos. 3,640,718, 3,617,288, and 3,779,778.
• diaryliodonium cations useful in the practice of the present invention are diphenyliodonium, di(4-chlorophenyl)iodonium, 4-trifluoromethylphenylphenyliodonium, 4-ethylphenylphenyliodonium, di(4-acetylphenyl)iodonium, tolylphenyliodonium, anisylphenyliodonium, 4-butoxyphenylphenyliodonium, di(4-phenylphenyl)iodonium, di(carbomethoxyphenyl)iodonium, etc.
• Examples of the iodonium cations are disclosed in U.S. Pat. Nos. 3,729,313, 4,076,705, and 4,386,154. Bis-type forms of these initiators may also be used.
• photolyzable organic halogen compounds are hexabromoethane, ⁇ , ⁇ , ⁇ ′, ⁇ ′-tetrabromoxylene, carbon tetrabromide, m -nitro(tribromoacetyl)benzene, ⁇ , ⁇ , ⁇ -trichloroacetanilide, trichloromethylsulfonylbenzene, tribromoquinaldine, bis(pentachlorocyclopentadiene), tribromomethylduinoxaline, ⁇ , ⁇ -dibromo- p -nitrotoluene, ⁇ , ⁇ , ⁇ , ⁇ ′ ⁇ ′, ⁇ ′-hexachloro- p -xylene, dibromotetrachloroethane, pentabromoethane, dibromodibenzoylmethane, carbon tetraiodide, halomethyl- s -triazines such as 2,4-bis(trichloromethyl)
• Acidic materials may be added to the light sensitive layer to increase its speed.
• the acids used in the present invention are acids as generally known to one skilled in the art. Organic acids are preferred, but inorganic acids (generally in relatively smaller concentrations) are also useful. Organic acids having carboxylic groups are most preferred.
• the acid should be present as at least about 0.1 percent by weight of the total weight of the light sensitive layer. More preferably it is present in amounts from 0.2 to 2.0 times the amount of nitrate ion.
• the acid may, for example, be present in a range of from 0.05 to 10 percent by weight, preferably from 0.1 to 7 percent, most preferably from 0.5 to 5 percent. Higher molecular weight acids are generally used at the higher concentrations and lower molecular weight acids used at the lower concentrations.
• Anhydrides such as phthalic anhydride, maleic anhdyride, succinic anhydride, acetic anhydride, and the like may also be used.
• temperatures should, of course, not be used during manufacture which would completely colorize the layer or decompose the photobleachable dye. Some colorization is tolerable, with the initial leuco dye concentrations chosen so as to allow for anticipated changes. It is preferred, however, that little or no leuco dye be oxidized dig forming and coating so that more standardized layers can be formed.
• the coating or forming temperature can be varied. Therefore, if the anticipated development temperature were, for example, 220 °F (104 °C), the drying temperature would be 140 °F (60 °C). It would therefore not be likely for the layer to gain any of its optical density at the drying temperature in less than 6 - 7 minutes.
• a reasonable development temperature range is between 160 °F (71 °C) and 350 °F (177 °C) and a reasonable dwell time is between 3 seconds and 2 minutes, preferably at between 175 °F (79 °C) and 250 °F (121 °C) and for 5 to 60 seconds, with the longer times most likely associated with the lower development temperatures.
• the imageable layers of the present invention must under some conditions allow reactive association amongst the active ingredients in order to enable imaging. That is, the individual ingredients may or may not be separated by impenetrable barriers (i.e., which cannot be dissolved, broken, or disrupted dig use) within the layer. Generally the active ingredients are homogeneously mixed (e.g., a molecular mixture) within the layer. They may be individually maintained in heat softenable binders which are dispersed or mixed within the layer and which soften upon heating to allow migration of ingredients, but this would require a longer development time. The ingredients may be incorporated into a binder medium, fine particles of which may be subsequently dispersed in a second layer binder medium as described in U.S. Patent No. 4,708,928
• the imageable layers of the present invention may contain various materials in combination with the essential ingredients of the present invention.
• plasticizers for example, plasticizers, coating aids, antioxidants (e.g., ascorbic acid, hindered phenols, phenidone, etc.), in amounts that would prevent oxidation of the dyes when heated), surfactants, antistatic agents, waxes, ultraviolet radiation absorbers, mild oxidizing agents in addition to the nitrate, and brighteners may be used without adversely affecting the practice of the invention.
• photobleachable, light sensitive photoinitiators may be combined with a nitrate salt and a leuco dye, to provide a light sensitive thermally developable imaging system. Visible light sensitive systems are desirable for natural full color reproduction, which cannot be obtained with ultraviolet or blue sensitive photoinitiators.
• compositions of the present invention increase stability of the developed image by reducing printout.
• D max and D min refer to the maximum and minimum optical density, respectively, which is observed in the developed imaged layer.
• Optical densities were determined using a MacBeth TD504 densitometer (Kollmorgen Corp., Newburgh, NY), using either a Status A red or green filter as appropriate.
• the benzoyl leuco of Basic Blue 3 was purchased from Ciba-Geigy (Ardsley, New York) under the trade name Pergascript TurquoiseTM.
• the o -nitroarylidene dyes of the type shown in Table 1 are prepared according to the general procedures described in U.S. Pat. No. 3,988,154.
• dye 37 was prepared from 4-fluoro-5-nitrophenylsulfone (Aldrich) using the general procedure of U.S. Pat. No 3,988,154 to afford a violet-brown solid, mp 264-267 °C.
• dye 38 was prepared from 4-fluoro-5-nitrophenylsulfone (Aldrich) using the general procedure of U.S. Pat. No. 3,988,154 to afford a dark brown solid, mp 156-159 °C. A solution of 4 mg of dye 39 in 3 ml of THF photobleached 86% to colorless products after 5 min on a 3M Model 213 overhead projector.
• a coating solution was prepared by mixing 10 mg of o -nitroarylidene dye 1 , 80 mg of the benzoyl leuco of Basic Blue 3, 940 mg of a solution (prepared from 9 g MeOH, 0.26 g Mg(NO3)2 x 6H2O, and 0.14 g tartaric acid), and 7.5 g of 20% PKHHTM in THF. The solution was placed on a shaker table for 15 minutes at room temperature in a dark room.
• the solution was knife-coated upon 4 mil (0.1 mm) transparent polyethylene terephthalate film at 4 mil (0.1 mm) wet thickness, air dried for 15 minutes, and dried at 50 °C for 5 minutes.
• the development temperature of the dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ strip on a 3M brand "179" Contact Printer Processor containing a white tungsten light source for 20 seconds at the 32 exposure setting (about 8.5 x 105 microwatts/cm2 as determined with a radiometric filter).
• the strip was placed on a Reichert Walkerbank apparatus (from Kofler Reichert, Austria) for 20 seconds and the thermal limits (the temperature at which development occurred) were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• the cyan color developed at 72 °C and 85 °C respectively.
• a control film was prepared as described in Example 6 containing 60 mg of 2,4,6-tris(trichloromethyl)-1,3,5-triazine.
• An 8 ⁇ x 2 ⁇ (20.3 cm x 5.1 cm) strip of the dried film was exposed lengthwise through a Stouffer ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• the strip was processed on a drum processor with a dwell time of 20 seconds at 89 °C. This afforded a negative of the original with eight steps of cyan image of optical density of D min + 0.6.
• a processed sample was exposed for two hours on a 3M brand Model 213 overhead projector.
• the D min increased 1.30 and the D max increased 0.50 optical density units (as determined with a Status A red filter on a Macbeth TD504 densitometer).
• Example 6 This example demonstrates the thermal development process is time and temperature dependent and that a range of development times or temperatures may be achieved.
• the same formulation of Example 6 was used to prepare another film in the same manner.
• An 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip of the dried film was exposed lengthwise through a Stouffer ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting and thermally developed for the indicated times to afford similar D min levels.
• the development times and the corresponding development temperatures required are shown in Table 4.
• each strip was placed on a Reichert Walkerbank apparatus for 20 seconds and the thermal limits were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• the sensitivity of each dried negative acting film was determined by exposing one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip lengthwise through a Stouter ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the full exposure setting.
• Each strip was processed on a drum processor with a dwell time of 20 seconds at a temperature at which the D min level appeared.
• the speed of each strip was determined at the point where the transmission optical density is D min + 0.6 optical density units (as determined with a Status A red filter on a Macbeth TD504 densitometer).
• the amount of photobleaching of each film was determined as described in Example 6.
• the results of each film are shown in Table 5, and show the general utility for the various o -nitroarylidene dyes.
• a test analogous to the sensitizing dye test specified in U.S. Pat. Nos. 4,386,154 and 4,460,677 was performed.
• a standard test solution was prepared with the following composition: 5.0 g of 5% (weight by volume) solution in methyl ethyl ketone of polyvinyl butyral (45,000-55,000 molecular weight, 9.0-13.0% hydroxyl content "Butvar-B76" is a trademarked product of Monsanto Chem. Co.) 0.3 g of trimethylolpropane trimethacrylate 0.03 g of 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine.
• the coating was treated with a finely divided black toner powder of the type conventionally used in xerography.
• the tested material was a sensitizer as described in U.S. Pat. No. 4,386,154, the trimethylol propane trimethacrylate monomer in the light exposed areas would be polymerized by the light generated free radicals from the photolyzable organic halogen compound, (i.e., 2-methyl-4,6-bis(trichloromethyl)- 1,3,5-triazine). Since the polymerized areas are essentially tack free, the black toner powder will selectively adhere only to the tacky, unexposed areas of the coating, providing a visual image corresponding to that in the template.
• This example illustrates the process of preparing a clear transparent image.
• a coating solution containing 20 mg of o -nitroarylidene dye 1 , 160 mg of the benzoyl leuco of Basic Blue 3, 1.88 g of a solution (prepared from 27 g MeOH, 0.78 g Mg(NO3)2 x 6H2, and 0.42 g succinic acid), and 15 g of 20% PKHHTM in THF was used to prepare a film in the same manner as described in Example 6.
• the dried film was exposed on a 3M brand " 179" Contact Printer Processor for 20 seconds at a 64 exposwe setting through a color negative and thermally developed on a drum processor with a dwell time of 20 seconds at 82 °C This afforded a bright cyan transparency image as a negative of the original with a red background.
• the image was exposed on a 3M brand Model 213 overhead projector for 2-5 minutes. The final image was devoid of the red background.
• Example 6 illustrates the ability to increase sensitivity with increasing exposure temperature.
• the dried film was stored for two weeks at room temperature in a black bag.
• the dried film was exposed on a hot plate through a Stouffer ⁇ 2, 21 step tablet with a 150 Watt tungsten reflector spot at 30 inches from the film.
• the film was thermally developed on a drum processor with a dwell time of 25 seconds at 95 °C. This afforded a bright cyan transparency image as a negative of the original.
• the table indicates the number of steps of cyan color developed at a transmission optical density of D min + 0.6 (as determined with a Status A red filter on a Macbeth TD504 densitometer), the number of steps of cyan color with transmission optical density equal to or greater than 1.0 optical density units, and D max versus the exposure temperature.
• Example 30 The formulation of Example 30 was used to prepare another film in the same manner.
• the dried film was exposed at room temperature through a calibrated Stouffer ⁇ 2, 21 step tablet in a sensitometer with a calibrated visible light of 536 nm with a band width of 20 nm.
• the film was thermally developed on a drum processor with a dwell time of 25 seconds at 91 °C.
• the film required light energy of 2000 ergs/cm2 to generate a transmission optical density of D min + 0.6 and 2600 ergs/cm2 to afford an optical density of 1.0 (as determined with a Status A red filter on a Macbeth TD504 densitometer).
• Example 30 The formulation of Example 30 was used to prepare a film on 4 mil filled opaque polyethylene terephthalate in the same manner.
• the dried film was exposed on a 3M brand "179" Contact Printer Processor for 5 seconds at the 32 exposure setting through a Stouffer ⁇ 2, 21 step tablet and thermally developed on a drum processor with a dwell time of 25 seconds at 91 °C.
• the image was exposed on a 3M brand Model 213 overhead projector for 5 minutes. This afforded a bright cyan image as a reflection print without red background stain with a D max reflection optical density greater than 3.0 optical density units (as determined with a Status A red filter on a Macbeth TR527 densitometer). In addition, 9 steps of cyan color with reflection optical density > 1.0 were generated.
• Example 30 The formulation of Example 30 was used to prepare another film in the same manner. 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strips of the dried film were exposed lengthwise on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting and stored in the dark for the indicated time period. Each strip was placed on a Reichert Schubank apparatus for 20 seconds. Table 9 reveals the time period between exposure and thermal development and the image temperature differentials ( ⁇ T °C) between the exposed and unexposed portions.
• the dried film was exposed through a Stouffer ⁇ 2, 21 step tablet on 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• the film was thermally developed on a drum processor with a dwell time of 20 seconds at 88 °C.
• a coating solution containing 10 mg of o -nitroarylidene dye 1 , 120 mg of the diazine magenta leuco 46 , 0.94 g of a solution (prepared from 27 g MeOH, 0.78 g Mg(NO3)2 x 6H2O, and 0.42 g succinic acid), and 7.5 g of 20% PKHHTM in THF was used to prepare a film in the same manner as Example 6.
• the dried film was exposed through a Stouter ⁇ 2, 21 step tablet on 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• the film was thermally developed on a drum processor with a dwell time of 20 seconds at 80 °C and exposed on a 3M brand Model 213 overhead projector for 5 minutes.
• the film was thermally developed on a drum processor with a dwell time of 20 seconds at 78.5 °C.
• the sample was exposed on a 3M brand Model 213 overhead projector for 5 minutes. This afforded a bright magenta transparency image as a negative of the original having transmission optical density D max of 2. 10 optical density units (Status A green filter), and D min of 0.12 optical density units.
• a coating solution containing 10 mg of o -nitroarylidene dye 1 , 80 mg of the benzoyl leuco of methylene blue thiazine, 0.94 g of a solution (prepared from 9 g MeOH, 0.26 g Mg(NO3)2 x 6H2O, and 0.16 g 1,3,5-benzenetricarboxylic acid), and 7.5 g of 20% PKHHTM in THF was used to prepare a film in the same manner as Example 6.
• the dried film was exposed through a Stouter ⁇ 2, 21 step tablet on 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• the film was thermally developed on a drum processor with a dwell time of 20 seconds at 89 °C.
• the sample was exposed on a 3M brand Model 213 overhead projector for 5 minutes. This afforded a bright blue transparency image devoid of red background stain as a negative of the original having transmission optical density D max of 1.76 optical density units (Status A red filter), and D min of 0.09 optical density units, and six steps of optical density greater than 1.0.
• This example illustrates the ability to use more than one leuco dye in the imaging system.
• the development temperature of the dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the 32 exposure setting. The strip was placed on a Reichert Schubank apparatus for 20 seconds and the development temperatures were determined. A mixed purple color from the development of both leuco dyes was generated and developed at 102 °C on the unexposed portion and at 88 °C on the exposed portion.
• Example 6 shows the wide variety of nitrate salts which can be used in the construction.
• 0.94 g of a solution prepared from 9 g methanol, 0. 14 g succinic acid, and the indicated amount of nitrate salt
• the development temperature of each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand " 179" Contact Printer Processor for 20 seconds at the 32 exposure setting.
• Each strip was placed on a Reichert Rothbank apparatus for 20 seconds and the thermal limits were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• each negative acting film was determined by exposing one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip lengthwise through a Stouffer ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting. Each strip was processed on a drum processor with a dwell time of 20 seconds at a temperature at which the D min level appeared. This afforded bright cyan transparency images as negatives of the original. The speed of each strip (in number of steps) was determined at the point where the transmission optical density is D min + 0.6 optical density units. The development temperature, D min , D max , and the number of steps of image optical density of D min + 0.6 of the example are shown in Table 12.
• a Status A red filter was used for the densitometer readings.
• the addition of silver nitrate to the formulation resulted in undesired oxidation of the coating formulation within one minute.
• This unacceptable film possessed a very high background D min when dried at room temperature. Therefore, silver nitrate is not a useful oxidant of the present invention.
• each strip was placed on a Reichert Walkerbank apparatus for 20 seconds and the thermal limits were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• the sensitivity of each negative acting film was determined by exposing one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip lengthwise through a Stouffer ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• Each strip was processed on a drum processor with a dwell time of 20 seconds at a temperature at which the D min level appeared. This afforded bright magenta transparency images as negatives of the original.
• the speed of each strip (in number of steps) was determined at the point where the transmission optical density is D min + 0.6.
• the development temperature, D min , D max , and the number of steps of image optical density of D min + 0.6 of the examples are shown in Table 13.
• a Status A green filter was used for the densitometer readings.
• binders may be useful in the invention.
• Coating solutions containing 10 mg of o -nitroarylidene dye 1 , 80 mg of the benzoyl leuco of Basic Blue 3, 940 mg of a solution (prepared from 9 g MeOH, 0.14 g succinic acid, and 0.26 g of Mg(NO3)2 x 6H2O) and the amount of the indicated binder in THF or in methyl ethyl ketone for Saran F-310TM were used to prepare films in the same manner as in Example 6.
• the development temperature of each dried film was determined by exposing lengthwise one-half of 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the 32 exposure setting. Each strip was placed on a Reichert Walkerbank apparatus for 20 seconds and the thermal limits were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• the sensitivity of each negative acting film was determined by exposing one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip lengthwise through a Stouffer ⁇ 2, 21 step tablet on a 3M brand "179" Contact Printer Processor for 10 seconds at the 32 exposure setting.
• Each strip was processed on a drum processor with a dwell time of 20 seconds at a temperature at which the D min level appeared. This afforded bright cyan transparency images as negatives of the original.
• the speed of each strip (in number of steps) was determined at the point where the transmission optical density is D min + 0.6 optical density units.
• the development temperature, D min , D max , and the number of steps of image optical density of D min + 0.6 of the example are shown in Table 14.
• a Status A red filter was used for the densitometer readings.
• Coating solutions containing 10 mg of indicated o -nitroarylidene dye, 80 mg of the benzoyl leuco of Basic Blue 3, 470 mg of a solution (prepared from 27 g MeOH and 0.78 g Mg(NO3)2 x 6H2O, and 0.42 g succinic acid), and 7.5 g of 20% PKHHTM in THF were used to prepare films in the same manner as Example 6.
• the development temperature of each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the full exposure setting.
• Coating solutions containing 10 mg of indicated o -nitroarylidene dye, 80 mg of the benzoyl leuco of methylene blue, 470 mg of a solution (prepared from 27 g MeOH and 0.78 g Mg(NO3)2 x 6H2O, and 0.42 g succinic acid), and 7.5 g of 20% PKHHTM in THF were used to prepare films in the same manner as Example 6.
• the development temperature of each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the full exposure setting.
• Coating solutions containing 10 mg of indicated o -nitroarylidene dye, 80 mg of the diazine magenta leuco 46 , 470 mg of a solution (prepared from 27 g MeOH and 0.78 g Mg(NO3)2 x 6H2O, and 0.42 g succinic acid), and 7.5 g of 20% PKHHTM in THF were used to prepare films in the same fashion as Example 6.
• the development temperature of each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the full exposure setting.
• Coating solutions containing 10 mg of indicated o -nitroarylidene dye, 80 mg of the leuco 53 , 470 mg of a solution (prepared from 27 g MeOH and 0.78 g Mg(NO3)2 x 6H2O, and 0.42 g succinic acid), and 7.5 g of 20% PKHHTM in THF were used to prepare films in the same manner as Example 6.
• the development temperature of each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the full exposure setting.
• each dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor for 20 seconds at the full exposure setting. Each strip was placed on a Reichert Walkerbank apparatus for 20 seconds and the thermal limits were determined for the exposed (T exp ) and unexposed (T unexp ) regions. The results of each film are shown in Table 19.
• This example illustrates that exposure to ammonia vapor thermally stabilizes the imageable layers of the present invention.
• a solution was prepared from 7.50 g 20% PKHHTM in THF, 0.12 g magenta leuco 46 , 0.01 g of 1, and 0.94 g of a solution (9 g MeOH, 0.26 g magnesium nitrate hexahydrate, and 0.14 g tartaric acid).
• the solution was knife coated onto 4 mil transparent polyester (PET) substrate at 4 mil wet thickness, dried at room temperature for 15 minutes, and dried at 50 °C for 5 minutes.
• PET transparent polyester
• the film was cut into strips which were placed on a Reichert Schubank thermal gradient apparatus for 20 seconds, and the thermally developed strips were placed in a chamber containing ammonia vapor from concentrated ammonium hydroxide at room temperature. Exposure times were 0, 0.5, 1, 5, 10, and 15 minutes.
• Nitrone dyes 47 and 48 were prepared by the condensation o -phenylhydroxylamine with the corresponding aldehyde (3,3-(4′-dimethylaminophenyl)propenal or 3-(4′dimethylaminophenyl)propenal for 47 and 48 , respectively, in EtOH according to the methods of West, P.R.; Davis, G.C.; Griffing, B.F. J.Imag. Sci. 1986 , 30 , 65.
• Solution A was prepared by mixing 26.25 g of 20% PKHHTM in tetrahydrofuran, 0.28 g of the benzoyl leuco of Basic blue 3, and 0.04 g of dye 1.
• Solution B was prepared by mixing 26.25 g of 20% PKHHTM in tetrahydrofuran, and 0.28 g of the benzoyl leuco of Basic Blue 3.
• Solution C was prepared by mixing 9 g methanol, 0.26 g of Mg(NO3)2 x 6H2O, and 0.14 g of succinic acid.
• Strips of the film coated with Solution D were imagewise exposed for 10 seconds on a 3M brand Model 179 contact printer processor at the 32 exposure setting. The thermal limit of the exposed samples was measured as before to give an average value of 86 °C.
• a fixed image with reduced background dye stain, improved color, and improved thermal stability can be prepared by the steps of (1) imagewise exposure, (2) thermal development, (3) blanket exposure, and (4) fixing by exposure to ammonia vapor.
• Example 74 The film construction of Example 74 was imagewise exposed as in Examples 74-75, and then thermally processed for 20 seconds at 85 °C to afford a blue-cyan colored negative image of the original image with magenta stain throughout exposed and unexposed regions.
• Transmission densitometer readings (Status A green filter, indicative of magenta color, and Status A filter, indicative of cyan color), were measured for both D max (light exposed), and D min (unexposed) areas on a MacBeth TR527 densitometer.
• a coating solution was made up of the following components: 7.5 g of 20% PKHHTM in THF, 80 mg of the benzoyl leuco of Basic Blue 3 (Pergascript TurquoiseTM, Ciba-Geigy, Ardsley, NY), 4 to 9 mg sensitizer dye, 940 mg solution of 9 g MeOH, 0.26 g Mg(NO3)2 x 6H2O, 0.14 g succinic acid; and 60 mg of either 2,4,6-tris(trichloromethyl)-1,3,5-triazine (TTT), or diphenyliodonium hexafluorophosphate (Ph2I).
• TTT 2,4,6-tris(trichloromethyl)-1,3,5-triazine
• Ph2I diphenyliodonium hexafluorophosphate
• the solution was placed on a shaker table for 15 minutes at room temperature in a dark room. Under appropriate safelights, the solution was knife-coated upon 4 mil (0.1 mm) transparent polyethylene terephthalate film at 4 mil (0.1 mm) wet thickness, and at 66 °C for 3.25 minutes. Several duplicate strips (approximately 8 ⁇ x 2 ⁇ ) were cut from this film and used for the following test.
• the development temperature of the dried film was determined by exposing lengthwise one-half of an 8 ⁇ x 2 ⁇ (20.3 x 5.1 cm) strip on a 3M brand "179" Contact Printer Processor containing a white tungsten light source for 20 seconds at the 32 exposure setting (about 8.5 x 105 microwatts/cm2).
• the strip was placed on a Reichert Schubank thermal gradient apparatus (Cambridge Instruments, Buffalo, NY), for 20 seconds and the thermal limits (the temperature at which development occurs), were determined for the exposed (T exp ) and unexposed (T unexp ) regions.
• the results are presented in Table 24.
• the amount of photobleaching was determined by the following procedure: one half of a strip was exposed on a 3M brand Model 213 OverHead Projector for 5 minutes. The UV spectrum of the unexposed film was taken, the ⁇ max was determined, and the optical density of the exposed strip was measured at the ⁇ max .
• the photothermographic speed was determined by the following procedure: one half of a strip was exposed lengthwise through a Stouffer ⁇ 2, 21 step tablet (Stouffer Graphic Arts Equipment, South Bend, IN), on a 3M brand "179" Contact Printer Processor or 10 seconds at an exposure setting of 32 (approximately 1.4 x 104 ergs sec/cm2 for 450-900 nm).
• the strip was processed on a for 20 seconds at a temperature between T unexp and T exp (from Examples 82-93), at which a background density of ⁇ 0.2 was observed.
• the speed, in number of steps, was determined at the point where the density is 0.6 + fog. The results are presented in Table 25.
• the following example demonstrates that the photobleachable sensitizers of this invention can be different from those of the photothermographic systems of U.S. Patent Nos. 4,386,154 and 4,460,677.
• a test analogous to the sensitizing dye test specified in U.S. Patent Nos. 4,386,154 and 4,460,677 was performed.
• a standard test solution was prepared with the following composition: 5.0 g of 5% (weight by volume) solution in methyl ethyl ketone of polyvinylbutyral (45,000 - 55,000 molecular weight, 9.0 - 13.0% hydroxyl content, ButvarTM-B76, Monsanto Chem. Co., St. Louis, MO), 0.3 g of trimethylolpropane trimethacrylate, and 0.03 g of 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine.
• the trimethylolpropane trimethacrylate monomer in the light exposed areas would be polymerized by the light generated free radicals from the photolyzable organic halogen compound, i.e., 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine. Since the polymerized areas are essentially tack free, the black toner powder selectively adheres to the tacky, unexposed areas of the coating, providing a visual image corresponding to that in the template.
• the results are shown below and are compared with a sensitizing dye (5,10-diethoxy-16,17-dimethoxyviolanthrene) of the prior art. Table 26 demonstrates the present invention is outside the scope of the prior art as described in U.S. Pat. Nos. 4,386,154 and 4,460,677.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Heat Sensitive Colour Forming Recording (AREA)

Applications Claiming Priority (4)

Publications (1)

Family

ID=27066134

Family Applications (1)

Country Status (2)

Cited By (3)

Citations (5)

• 1991
  • 1991-06-14 EP EP91305402A patent/EP0462763A1/fr not_active Withdrawn
  • 1991-06-17 JP JP14478791A patent/JPH04232941A/ja active Pending

Patent Citations (5)

Also Published As

Similar Documents

Legal Events