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
  • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N1/00—Printing plates or foils; Materials therefor
  • B41N1/24—Stencils; Stencil materials; Carriers therefor
  • B41N1/242—Backing sheets; Top sheets; Intercalated sheets, e.g. cushion sheets; Release layers or coatings; Means to obtain a contrasting image, e.g. with a carbon sheet or coating

Definitions

• My invention constitutes improvements in stencils and materials for making stencils and more particularly to improvements relating to the preservation and protection of hydrophilic films or layers, for example, the gelatin films of stencil sheets.
• One known method of printing graphic images is the screen process in which a stencil is applied to a surface to be printed and coloring matter such as printing ink is passed through the openings of the stencil onto the surface. Excess coloring matter is wiped off and the stencil is removed, thereby leaving on the surface a pattern of coloring matter corresponding to the pattern of the stencil.
• This stencil printing process is used to apply graphic images on many kinds of surfaces with many kinds of coloring matter.
• Stencils may be prepared from paper, cloth, plastic film and other similar materials. They are cut, punched, etched taped or treated in some manner to produce a physical pattern on the sheet.
• a typical sheet for making a stencil includes a plastic film support, for example, polyethylene terephthalate coated with a hydrophilic film-former such as gelatin.
• Gelatin has excellent properties for the preparation of stencils. However, it also has one serious disadvantage; it becomes brittle with age. Thus, in the form of a layer, aged gelatin develops cracks quite readily as the result of slight stresses. These cracks cannot be tolerated where the gelatin layer is used in a stencil since coloring matter would flow through and be deposited in unwanted areas.
• gelatin Another serious disadvantage in the use of gelatin is the absorption of moisture from the atmosphere or from the fingers. In either case the gelatin becomes tacky and the stencil sheets become difiicult to separate from each other, or have no relative slip. Fingerprints show up and mar the quality of the stencil. Stacks of stencil sheets block or stick together. When the stacked sheets are pulled apart, pick-off or undesirable transfer of gelatin from one sheet to another occurs and the sheets are ruined.
• one object of the present invention is to provide a novel and useful sheet which is preserved and protected from the effects of atmospheric moisture by a protective coating which does not interfere with subsequent processing.
• Another object is to provide a new composition of matter for protecting and preserving a hydrophilic layer from the effects of atmospheric moisture without interfering with subsequent processing of the hydrophilic layer.
• hydrophilic films or layers such as gelatin
• a protective coating material including a water-soluble, organic solvent-soluble binder in the solvent and fine, solvent-insoluble, substantially inert particles of an anti-tack agent uniformly dispersed in the protective coating material.
• the sheet comprises a support carrying a hydrophilic or gelatin layer which in turn carries a dry protective coating of the binder material in which the particles of the anti-tack agent are uniformly dispersed.
• binders and anti-tack agents are effective for protecting and preserving the hydrophilic film or layer from the effects of moisture with out interfering with subsequent handling or processing of the hydrophilic film or layer in water or aqueous solutions.
• EXAMPLE 1 Polyethylene terephthalate film supports were coated with gelatin from an aqueous solution to provide a number of units. The gelatin coatings on the supports were dried. A 5% by weight solution of hydfoxypropyl cellulose polymer as the binder in ethanol as the solvent, was prepared and 2 grams of zinc stearate powder, as the anti-tack agent, were uniformly dispersed in grams of the 5% solution.
• This dispersion was then coated on the dry gelatin layers of one portion of the gelatin-coated units by the flow-down technique and then dried. A thin uniform protective coating was thus formed on the gelatin layer of each of these units. The thickness of the dried protective coating was about 0.1 mil.
• the resulting protected gelatin coated sheets were then subjected to 70% relative humidity conditions at 70 F. for twenty four hours, after which the sheets were not tacky and handled with ease and free slip. Furthermore, the protectively coated sheets when stacked did not block or stick together. The sheets were easily separated with no pick-off.
• the protected sheets may be used in various ways and in various processes, for example one of the protected sheets was sensitized by immersion in a 2% aqueous potassium dichromate solution for a few minutes. The agueous sensitizer solution penetrated the water-soluble protective coating and sensitized the gelatin layer. No special step or operation was required to remove the protective coating.
• the sensitized stencil sheet was then exposed to ultraviolet light through a transparency. Where the actinic light struck the sensitized gelatin, a hardening action insolubilized the gelatin.
• the stencil sheet was then washed with warm water to remove unhardened parts of the gelatin layer which remained soluble in water.
• the protective coating was also washed off since it was not affected by exposure to light. Only the insolubilized areas of the gelatin layer remained on the film support. A relief image suitable for screen printing was then produced in the usual Way.
• a Water-soluble dye may be incorporated into the gelatin layer to provide visual contrast in the relief image.
• the insolubilized areas retain the color of the dye while the washed out areas are colorless. This provides a visible indication of the completeness of the washing.
• EXAMPLE 2 A polyethylene terephthalate film sheet support was coated with a gelatin solution as in Example 1, but in this case the gelatin solution included a dichromate sensitizer and a small amount of water-soluble dye. The coating was dried and then coated with a zinc stearate-hydroxypropyl cellulose dispersion the same as in Example 1. This protective coating was air-dried.
• unprotected presensitized sheets were tacky to the touch when exposed to the same conditions.
• the unprotected sheets stuck together when stacked, and pickoff occurred when the stacked sheets were pulled apart.
• a protected sheet in accordance with this example was exposed to light through a transparency and washed in the usual manner to produce a relief image suitable for making a stencil. No special processing was required to remove the protective coating and at no time did the pro tective coating interfere with the normal functioning of the hydrophilic gelatin layer.
• the protective coating protected and preserved the unsensitized as Well as the presensitzed layers Without interfering with normal processing.
• EXAMPLE 3 A polyethylene terephthalate film support was coated with a gelatin solution as in Example 1. The gelatin layer was dried and then coated with 5% hydroxypropyl cellulose solution in ethanol into which solution slica powder was uniformly dispersed in the proportion of 2 grams to 100 grams of solution. The dry protective coating containing the uniformly dispersed silica powder protected and preserved the gelatin layer when it was exposed to humid conditions as in Example 1. Unprotected sheets were tacky under the same conditions.
• anti-tack agents may be used in place of those in the above examples.
• Zinc oxide powder or titanium dioxide powder may be used.
• Other powders such as polyethylene powder and polypropylene powder are equally suitable anti-tack agents.
• Other metal soaps may be used in place of the zinc stearate but they must be fine, solid, dispersible powders. Suitable examples are the stearates of aluminum, magnesium, nickel and calcium, ferric and ferrous stearates zinc and aluminum palmitates. All of these materials are substantially inert, water insoluble and unreactive under the conditions of use.
• Suitable water-soluble, solvent-soluble binders may be used.
• suitable binders are polyvinyl-pyrrolidone, polyethylene glycol, ethylene-maleic anhydride copolymer and polyethylene oxide.
• Suitable solvents include methanol and dimethyl formamide in addition to ethanol.
• Other organic solvents may be used and the solvent selected should dissolve the selected binder, and the combination should not affect the hydrophylic layer. The solvent should be vaporizable under the usual drying conditions.
• the present invention is directed to an improvement, it will be understood that those skilled in the art will know the supports and the hydrophilic layer materials to be used, the effect of different grades of binder material on solution vicosity, the proper proportion of anti-tack agent to binder to be used for optimum results for each combination, and the dyes and sensitizers which are suitable.
• the anti-tack agent Works and is effective under the conditions described because the solid particles of the agent protrude from the surface of the thin protective coating in sufficient numbers and over the Whole area of the sheet to eliminate tackiness due to the presence of atmospheric moisture. These particles may serve as many minute separators between sheets. In any case they cooperate with the binder to promote slip and eliminate tackiness.
• the ratio of anti-tack agent to binder is less than 1 to 1.
• a sheet including a water-insoluble support and a hydrophilic layer coated on said support and normally affected by atmospheric moisture, the improvement comprising a protective coating on said layer for protecting and preserving said hydrophilic layer from the effects of atmospheric moisture without interfering in subsequent use and processing of said layer, said protective coating comprising a water-soluble and organic solvent-soluble binder, and fine, solid, water-insoluble and organic solvent-insoluble particles of an anti-tack agent uniformly dispersed in the coating in which the weight ratio of antitack agent to binder is less than one to one, said anti-tack agent being a metal soap substantially insoluble in water and unreactive with said binder and said layer.
• a sheet including a Water-insoluble support and a hydrophilic layer coated on said support and normally affected by atmospheric moisture
• the improvement comprising a protective coating on said layer for protecting and preserving said hydrophilic layer from the effects of atmospheric moisture without interfering in subsequent use and processing of said layer
• said protective coating comprising a waterand organic solvent-soluble binder and fine, solid waterand solvent-insoluble particles of an anti-tack and slip promoting agent uniformly dispersed in the binder of the coating, which particles are solid particles of a metal soap substantially insoluble in water and unreactive with respect to the hydrophilic layer, the weight ratio of anti-tack and slip promoting agent to binder being less than 1 to 1.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Laminated Bodies (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (7)

Cited By (6)

Citations (3)

• 1966
  • 1966-05-26 US US553055A patent/US3503743A/en not_active Expired - Lifetime
• 1967
  • 1967-05-05 GB GB20934/67A patent/GB1194858A/en not_active Expired
  • 1967-05-24 DE DE19671671610 patent/DE1671610B2/de active Granted
  • 1967-05-24 CH CH731867A patent/CH475417A/fr not_active IP Right Cessation
  • 1967-05-25 SE SE7383/67A patent/SE321245B/xx unknown
  • 1967-05-25 NO NO168308A patent/NO124669B/no unknown
  • 1967-05-26 NL NL6707383A patent/NL6707383A/xx unknown

Patent Citations (3)

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