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
  • G03C1/54—Diazonium salts or diazo anhydrides

Definitions

• organic compounds as light-sensitive media for photographic purposes is well known, and is perhaps best exemplified by the diazo process.
• This process is based on the photochemical changes effected in various diazonium salts upon exposure to light, and which atfect their capacity to form dyes.
• dyes are formed when the diazonium compounds, or diazotized amines, couple with phenols or aromatic amines in an alkaline medium. Upon exposure to light, the diazonium compounds undergo decomposition and are rendered incapable of forming the corresponding dyestuffs through the coupling process.
• a dyestulf is formed at the portions of the lightsensitive material which have not been exposed to light (i.e., at portions on the light-sensitive material which have been protected by the pattern or design on the material to be copied) and thus a positive record is obtained from a positive image.
• diazotype processes used for the reproduction of documents two methods of development are used, the so-called dry development with gaseous ammonia and the so-called semi-wet development with alkaline solutions containing among other things the azo dye coupling component or coupler. Consequently, there are also two types of light sensitive material suitable for the diazotype reproduction processes, to wit, two component material for the dry development process and one component material for the semi-wet development process.
• the azo dye coupling component is present in the light-sensitive coating and not in the developing material.
• the semiwet materials the azo dye coupling component is present in the developer but not in the light-sensitive material. It is understood that the two essential components are the light sensitive diazo compound and the azo dye coupling component.
• the coupling solutions usually contain a mixture of ingredients which are selectively absorbed by the copying paper during the development process. This results in non-uniform color reproduction as the solution is used during a given period.
• the dye formed by the diazo and the coupler must be wash-fast, since it is formed under wet conditions which are favorable to bleeding.
• a further object is to provide a dry diazotype sheet having a light-sensitive coating thereon, and where said material has good storage characteristics.
• a further object is to provide a dry diazotype sheet having a light-sensitive coating thereon, and which coating has no coupling component incorporated therein.
• a suitable substrate with a composition containing the cation of a light-sensitive diazonium salt.
• a zinc chloride stabilizer is preferably used to provide stability inthe manner well understood in the art.
• suitable other or equivalent adjuvants such as citric acid, oxalic acid,
• the material After the substrate is coated with the aqueous diazonium solution, the material is dried. Upon exposure to light, the portions of diazonium compounds exposed to light undergo decomposition and, therefore, are incapable of forming conjugated, colored compounds. A latent image exists on the diazonium coated substrate. During development, a dyestuif is formed at the portions of the light-sensitive material which have not been'exposed to light (i.e., at portions on the 1ight-sensitive material to be copied) and thus a positive record is obtained from a positive image.
• the diazonium material containing a latent image is treated with ammonium, a primary aliphatic amine, or a secondary aliphatic amine.
• These materials contain electron rich centers and also at least one hydrogen directly bonded to a nitrogen. It is believed that they join with the positive diazo group with the expulsion of a hydrogen to form the more stable aromatic azo compound.
• Ammonia and primary aliphatic amines form azo compounds in which the nitrogen which was originally part of the ammonia or amine still contains an electron rich center and a directly bonded hydrogen. Such a nitrogen is believed to join once again with a diazo group to form a symmetrical azo compound with five nitrogen molecules in a chain. This is described by the following formulas, where AR is an aryl radical and R is aliphatic.
• a preferred formula contains p-diazo-N-morpholino-2, S-diethoxybenzene chloride-half zinc chloride salt, pdiazo-N-ethyl-N-benzylaniline chloridehalf zinc chloride salt, and citric acid using water as a solvent.
• the solution is coated on the paper and dried at a temperature between 70 and 140 F.
• suitable radiant energy through a master (such as a letter typed on 20-pound bond paper) and treatment of the exposed coating with warm moist ammonia fumes, an image of the original is produced.
• the combined diazo compounds yield a very satisfactory, near black color. Since no coupler or basic ingredient need be present in the formula which is coated on the substrate, the stability of the unexposed material is substantially improved.
• Example I The following solution was coated on paper to a wet thickness of about 1 mil and dried. This gave a concentration of about 0.75 grams of diazo per, square meter. When exposed to light and developed with moist aqueous ammonia, a brown image was produced.
• Example II The diazo of Example I can be replaced by one of the following diazos:
• Example III The acid of Example I can be replaced by citric acid, 1-6 grams per 100 grams of water or oxalic acid 1-4 grams.
• Example IV The thiourea may be left out or replaced by one of the substituted thioureas such as 1-allyl-2-thiourea and stabilizers such as naphthalene-1,3,6-trisodium sulfonate may be used.
• substituted thioureas such as 1-allyl-2-thiourea and stabilizers such as naphthalene-1,3,6-trisodium sulfonate may be used.
• Example V Mixtures of two or more diazonium salts may be used to improve the shade of the color obtained.
• the following is an example illustrating such a composition:
• background stabilizers such as thiourea
• diazo stabilizers such as naphthalene-1,3,6-trisodiu-m sulfonate
• a process for development of a visual image in the 5 absence of an azo-coupling component which comprises:
• said light-sensitive material being a layer consisting essentially of a mixture of light-sensitive diazonium salts, said mixture comprising the cation of a p-diazo-N-ethyl-N benzylaniline salt and the cation of a 4-N-morpholino-2,5-diethoxy benzene diazonium salt, and

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

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Citations (9)

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• 1964
  • 1964-06-08 US US373549A patent/US3331690A/en not_active Expired - Lifetime
• 1965
  • 1965-05-07 CH CH638965A patent/CH446887A/de unknown
  • 1965-05-10 GB GB19559/65A patent/GB1100456A/en not_active Expired
  • 1965-06-02 DE DEI28266A patent/DE1294808B/de active Pending
  • 1965-06-04 SE SE7365/65A patent/SE344642B/xx unknown
  • 1965-06-04 NL NL6507110A patent/NL6507110A/xx unknown
  • 1965-06-08 FR FR19876A patent/FR1437034A/fr not_active Expired

Patent Citations (9)

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