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
  • G03C1/52—Compositions containing diazo compounds as photosensitive substances
  • G03C1/58—Coupling substances therefor
• • 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
  • G03C1/52—Compositions containing diazo compounds as photosensitive substances
  • G03C1/56—Diazo sulfonates

Definitions

• Heatand light-sensitive compositions containing aryl diazosulfonate salts and coupling agents are known in the art, and have been used in processes for data reproduction. Such processes make use of the following reactions to reproduce data, such as graphic or pictorial images:
• a typical conventional diazotype reproduction process involves the sensitization of a base or carrier, such as paper, with a composition containing a light-sensitive diazo compound such as a diazonium salt.
• the sensitized base is then exposed to light under an image pattern. Where light strikes the sensitized base, the diazonium compound is decomposed or burnt out in the areas exposed to light.
• a colored image is then developed in the areas not exposed to light by reaction of the remaining diazonium compound in the unexposed areas with a coupler to give an azo dye.
• the coupler is included with the diazo compound in the sensitizing coating and the coupling reaction is simply effected by heating.
• aryl diazosulfonate salts behave anomalously. As the light sensitivity of such a heatand light-sensitive system is increased, due to the choice of particular highly light-sensitive aryl diazosulfonate salts employed, the thermal sensitivity of the system decreases. This experience runs contrary to what would be expected by those skilled in the art, since sensitivity to heat and light are both ultimately dependcut on the molecular structure of the diazosulfonate salts employed and both would normally be expected to decrease and/or increase as diazo compounds with greater or lesser molecular stability were investigated.
• the diazosulfonate salts (where R above is an aromatic radical and X is a metal ion, such as an alkali metal ion) are in equilibrium with 21 diazonium cation and a metal sulfite anion.
• the applicants have found that the diazonium cation RNEN+ will not react significantly with a coupler in the presence of heat since the rate of thermal decomposition of the cation is faster than its rate of coupling: the heat-sensitive species in the coupling reaction is probably the diazosulfonate salt.
• diazotype systems employing arromatic diazosulfonates salts and a coupling agent can be modified in a manner permitting the use of diazosulfonate salts having increased light sensitivity without incurring the concomitant loss in heat sensitivity which has heretofore been observed in the prior art when such highly light-sensitive materials have been used.
• This result is achieved by adding a dissociable diazonium salt to systems containing an aromatic diazosulfonate.
• the presence of the dissociable diazonium salt i.e. the presence of diazonium cations
• diazosulfon-ate salts suitable for use in the compositions of the invention are well known in the prior art. Materials of this type are shown in US. Patents 2,217,189, 2,694,009, 2,974,042, 2,995,442, 2,994,608, and 3,029,146, for example. Particularly good results have been obtained in the present invention when using alkali metal p-amino diazosulfonates having nuclear alkyl or allcoxy substitutents and having one or more N-substituents discouraging air oxidation of the amino group. These N-substituents may be monoor di-alkyl groups, for example, or the nitrogen atom may be included in a ring system such as a morpholino group.
• couplers in the system of the invention the socalled active couplers also conventional in diazo systems such as phloroglucinol, resorcinol, 8-naphthol, etc. can be used.
• a coupler particularly preferred according to the present invention is 2,3-dihydroxynaphthalene, both because of the colors of the azo dyes formed with this coupler and because of the ease with which the material couples to form such azo dyes.
• the systems of the invention additionally critically contain a diazonium cation preferably, but not necessarily, corresponding with the diazo nucleus of the diazosulfonate materials employed.
• a diazonium ion such as Z-rnethyl-4-diethylaminobenzene diazonium ion
• a halide salt such as the diazonium chloride, bromide, or iodide.
• any amount of dissociable salt added to the diazosulfonate will disturb the equilibrium shown earlier and increase the concentration of heat-sensitive diazosulfonate in the system to a value above its equilibrium concentration in the absence of added diazonium cation at comparable conditions of temperature and solvation.
• the addition of excessively large amounts of diazonium cation will only increase the time for bleaching a system containing these ions under light without contributing to color formation since, as noted earlier, the diazonium ion does not participate significantly in thermally induced coupling reactions in view of its more rapid thermal descomposition in a competitive reaction.
• the ratio of added diazonium salt to diazosulfonate salt present in the system may vary from 1:4 to 1:8.
• the basic inventive principle of suppression of the equilibrium ionization of the diazosulfonate salt is operative when even the smallest amount of diazonium cation is added to the system (since the additional presence of the cation will upset the equilibrium when present in even small amounts) and is equally applicable when extremely large amounts of the diazonium cation are added to the system.
• the systems of the present invention are conveniently employed in data reproduction processes by coating them in layer form onto a suitable carrier or substrate material such as of wood, glass, plastic, fabric, paper, or the like.
• a suitable carrier or substrate material such as of wood, glass, plastic, fabric, paper, or the like.
• Such coated substrates, particularly coated papers are useful in a number of reproduction processes including the so-called reflex process and the so-called heat developable diazo process.
• the copy sheet containing the heat and light sensitive diazo layer is placed coated face up atop and in contact with the original to be reproduced.
• a material transparent to infrared radiation such as the infrared transparent papers known to the art, is used as the carrier for the diazo coating.
• the copy and original are then exposed to infrared radiation, such as a source of radiation in the near infrared, through the copy sheet.
• infrared radiation such as a source of radiation in the near infrared
• the heat is transferred back to the heat-sensitive layer of the copy sheet in contact with the original.
• coupling between the (hazesulfonate and coupler occurs to reproduce the original image.
• the resulting copy is subsequently fixed by exposing the copy sheet to ultraviolet light which bleaches those areas where no coupling reaction has occurred by destroying the photosensitive diazoniurn cation in equilibrium with the diazosulfonate salts present in the heatand light-sensitive layer of the copy sheet.
• a substrate material coated with the heatand light-sensitive compositions of the invention is exposed to an ultraviolet source through the original to be copied, which latter must be transparent to ultraviolet light.
• Ultraviolet light pass ing through the non-image areas of the original will destroy the diazosulfonate material in the sensitive layer of the underlying copy sheet by photo-destruction of the diazonium ion in equilibrium with the diazosulfonate salt.
• the diazo layer of the copy sheet will remain unchanged.
• the copy sheet may then be heated to cause coupling of the diazosulfonate salts and coupled remaining in the copy sheet under the image areas of the original to form a colored copy of the original image.
• the heat developable diazo process may employ a copy sheet of any suitable material, but can only be used with originals which are transparent to ultraviolet.
• the coating of infrared transparent substrate materials with the heatand light-sensitive coatings of the invention adapts the sensitized substrate to use in either process.
• Infrared transparent materials suitable for use as carriers or sub strates for the sensitive compositions of the invention are known in the art, and includes, for example, the so-called glassine or greaseproof papers, or ordinary thin paper stock.
• coated papers of the invention are easily adaptable to use in machines now commercially available for thermal reproduction processes such as the so-called Therrnofax process.
• the ultraviolet sources used for bleaching exposures can be those now employed in commercial diazotype processes, such as in the Ozamatic machine.
• undercoating layer to the paper.
• a synthetic or natural resinous substance for example polyvinyl acetate, or of any other water-resistant chemically inert material as an undercoating layer will inhibit ab sorption of the coating materials by the substrate, and will keep the heatand light-sensitive chemicals at the surface of the substrate.
• under-coating materials may be applied in amounts of anywhere from /2 to 2 lbs. per 3090 sq. feet.
• the thermal and light-sensitive coating is generally applied to a carrier in thickness such that /2 to 1 /2 lbs. of dry solids are present per 3000 sq. feet of coated substratc. However, larger or smaller amounts may be employed depending on the color density and sensitivity required in the coating, and the active materials may be combined with an inert resinous binder, if desired.
• Such coatings may, for example, comprise materials such as paraffin or natural or synthetic resinous materials such as polyvinylidene chloride applied in amounts of from /2 to 4 lbs. per 3000 sq. feet of substrate.
• the coating layers are suitably applied with the coating substances in solution in an inert solvent whose nature is not otherwise critical.
• solvents such as methanol, ethanol, acetone, methyl ethyl ketone and other such volatile polar organic materials have proved to be good solvents for the diazo compounds and couplers involved.
• borax is particularly useful in stabilizing the systems against changes due to aging at room temperature and/or under conditions of high humidity.
• the presence of borax is optional, but particularly good results in stabilization have been obtained when the molar ratio of borax to coupling agent varies between about 1:10 and about 1:30.
• diazotype systems have heretofore been observed in the art, and is also true of the present system, that improved results in diazotype systems are observed in the presence of organic acid materials.
• a material such as citric acid or an equivalent, preferably solid, weak organic or inorganic acid is included in diazotype systems. Though such materials are not critically present, their presence in the system improves its behavior.
• the effect of an acidic material in the system is not known, although it has been speculated that the acid plays a buffering role. Since diazo systems of this type are generally non-aqueous systems, the acids present are very little ionized and it is not possible to speak of the pH of the system.
• the acids are usually employed in amounts such that dilution of the system with water results in an aqueous solution having a pH of between about 3.5 and 4.5.
• Acids such as lactic, stearic, acetic, ascorbic, oxalic, glycollic, malonic, boric, etc. can be used alone, or in combination with each other or with citric acid.
• EXAMPLE 1 A preferred coating composition was prepared by dissolving the following ingredients in a mixture of 5.0 ml. of water and 95 ml. of methanol:
• the coated paper was used in a reflex process by placing the coated paper with the coated side up atop the original to be copied, the original being face up.
• the two sheets were passed through a Thermofax Secretary machine.
• Infrared radiation passing through the copy paper was absorbed by the image areas of the original, converted to heat, and conducted back to the copy paper.
• the heat promoted coupling and dye formation in the copy paper over the image areas of the original.
• the copy paper was then exposed to ultraviolet light in a Ozalid machine for a few seconds to produce a fixed copy of the original image, resistant to further light or heat, on a colorless background.
• Another sheet of the copy paper was exposed to an ultraviolet source, coated side up, through a translucent original to be copied. Where light penetrated the original, i.e., in the non-image areas, decomposition of the active ingredients of the copy sheet coating occurred. After exposure to ultraviolet, the copy sheet was then heated for a short period during which coupling and dye formation between the diazonium compounds and the coupler occurred in the areas not exposed to and bleached by the ultraviolet light source.
• a copy paper of improved stability was prepared by pre-coating an infrared transparent paper of the type earlier described, prior to sensitization of the copy paper, with a water-resistant coating containing 0.4% by weight of borax.
• the pre-coat inhibited soaking in of the sensitive layer into the paper substrate, and the presence of the borax in the pre-coat lends additional moisture stability to the paper when subsequently coated with the heatand light-sensitive composition.
• Still further samples were prepared in which paratfin overcoats were applied to sensitized papers and to precoated sensitized papers.
• a coating composition was prepared by dissolving the following components in a mixture of 37.0 gms. water and 55.0 gins. methyl alcohol:
• the material was used to coat commercially available papers for the preparation of copy media suitable for use in the reflex and heat developable diazo processes.
• Heat and light-sensitive compositions suitable for the preparation of coated printing media for data reproduction were prepared by dissolving the following ingredients in 5 gms. of water and gms. of methyl alcohol:
• compositions were used for the preparation of coated data reproduction media, including coated papers having either or both water-resistant precoats and waterresistant overcoatings.
• EXAMPLE 4 A non-aqueous .heatand light-sensitive composition was prepared by dissolving the following ingredients in 95 gms. of methyl alcohol:
• a heatand light-sensitive coating composition was prepared by admixing the following ingredients in 5 gms. of water and 95 gms. of methyl alcohol:
• a data reproduction process for producing a pos itive copy of an original having image areas and nonimage areas in a copy medium comprising a heatand light-sensitive composition and a carrier therefor, said composition comprising a diazosulfona-te salt and a coupling agent reactive therewith under the influence of heat, which process comprises exposing said copy medium to heat in those of its portions corresponding with image areas of the original, whereby color is formed in the heat struck portions of said copy medium by reaction of said diazosulfonate salt and said coupling agent, and densensitizing said copy medium in those of its portions corresponding with non-image areas of the original by exposing said medium to ultraviolet light, whereby said diazosulfonate salt is decomposed and rendered incapable of reaction with said coupling agent, the improvement of further adding to said composition a diazonium salt supplying a diazonium cation to said composition.
• a data reproduction process for producing a positive copy of an original having image areas and nonirnage areas in a copy medium comprising a heatand light-sensitive composition and a carrier therefor, said composition comprising a diazosultonate salt and a coup'iing agent reactive therewith under the influence of heat, which process comprises transferring heat from image areas of the original to portions of said copy medium corresponding with image areas of the original whereby color is formed in heat struck portions of said copy medium by reaction of said diazosulfonate salt and said coupling agent, and then desensitizing said copy medium in those of its portions corresponding with non-image areas of the original by exposing said medium to ultravioiet light, whereby said diazosulfonate salt is decomposed and rendered incapable of reaction with said coupling agent, the improvement of further adding to said composition a diazonium salt supplying a diazonium cation to said composition.
• a data reproduction process for producing a positive copy of an original having image areas and nonimage areas in a copy medium comprising heatand light-sensitive composition and a carrier therefor, said composition comprising a diazosulfonate salt and a coupling agent reactive therewith under the influence of heat, which process comprises exposing said copy medium to ultraviolet light through said original, whereby portions of said medium corresponding with non-image areas of the original are desensitized by decomposition of said diazosulfonate salt which is rendered incapable of reaction with said coupling agent, and then heating said copy medium to form color by reaction of said diazosulfonate salt and coupling agent in those unexposed areas of said medium corresponding with image areas of the originai, the improvement of including in said composition a diazonium salt supplying a diazonium cation to said composition.
• diazosulfonate and said cliazonium cation has the formula R'NEN+ where R and R are aromatic groups and X is an alkali metal ion.
• Heatand light-sensitive compositions comprising a diazosulfonate salt, a coupling agent reactive with said diazosulfonate salt under the influence of heat to form color, and a further diazo material which is a diazonium salt supplying a diazonium cation to said composition, said diazosulfonate salt being decomposable by irradiation with ultraviolet light to render it incapable of reaction with said coupling agent.
• a heatand light-sensitive copy medium for data reproduction processes comprising a substrate coated with a heatand light-sensitive composition comprising a diazosuifonate salt, a coupling agent reactive with said diazosulfonate salt under the influence of heat to form color, and a further diazo material which is a diazonium salt supplying diazonium cation to said composition, said diazosulfonate salt being decomposable by irradition with ultraviolet light to render it incapable of reaction with said coupling agent.
• a copy medium as in claim 9 wherein said diazosulfonate salt has the formula RN NSO X and said diazonium cation has the formula R'NEN' where R and R are aromatic groups and X is an alkali metal ion.

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Citations (10)

• 1963
  • 1963-06-03 US US284803A patent/US3309200A/en not_active Expired - Lifetime
• 1964
  • 1964-06-02 BE BE648724D patent/BE648724A/xx unknown
  • 1964-06-02 NL NL6406202A patent/NL6406202A/xx unknown
  • 1964-06-02 DE DE19641471670 patent/DE1471670A1/de active Pending
  • 1964-06-03 GB GB23024/64A patent/GB1062865A/en not_active Expired

Patent Citations (10)

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