# US 5,704,968 A · Stamp ink and stamp ink impregnation pad for stencil printing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,968 A - Document ID: US5704968A - Status: Granted - Kind: A - Application number: 08/593,050 - Filed: 1996-01-29 - Granted: 1998-01-06 - Earliest claimed: 1995-01-31 - Assignees: Brother Kogyo Kabushiki Kaisha - Inventors: Hiroshi Taira; Minoru Yamamoto; Hiroshi Takami; Takahiro Yuasa; Hideki Hasegawa - Web page: https://patentgrep.com/patent/US5704968A ## CPC - C09D 11/02: Printing inks (C09D11/30 takes precedence) - B41K 1/32: for stencilling - C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D) - B41K: STAMPS; STAMPING OR NUMBERING APPARATUS OR DEVICES (marking meat A22C17/10; embossing combined with printing B41F19/00; selective printing mechanisms B41J; embossing decorations or marks B44B5/00; marking or coding completed packages B65B61/26; ticket printing and issuing, fare registering, nonprinting aspects of franking apparatus G07B) ## Abstract A stamp ink, for stencil printing, is made from a coloring-agent mixed in a vehicle made from resin and oil-based solvent. The stamp ink has a viscosity in a range from 20 to 250 poises at a shear rate of 20/sec under temperature of 25.degree. C. and has a thixotropy index T.I. in a range from 1.2 to 3.0 under temperature of 25.degree. C. where the thixotropy index T.I. is defined in the expression of: T.I.=(Viscosity at a shear rate of 0.5/sec)/(Viscosity at a shear rate of 5.O/sec). ## Claims ### Claim 1 A stamp ink for stencil printing, comprising a coloring-agent mixed in a vehicle made from resin and oil-based solvent, wherein the stamp ink has a viscosity in the range of from 20 to 250 posies at a shear rate of 20/sec at a temperature of 25.degree. C., and has a thixotropy index T.I. in the range of from 1.2 to 3.0 at a temperature of 25.degree. C., wherein the thixotropy index T.I. is defined in the expression of: T.I.=(Viscosity at a shear rate of 0.5/sec)/(Viscosity at a shear rate of 5.0/sec). ### Claim 2 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the stamp ink is made from the coloring-agent, the resin, and the oil-based solvent with their amounts allowing the stamp ink to develop the viscosity in the range from 20 to 250 poises at the shear rate of 20/sec and to develop the thixotropy index T.I. in the range from 1.2 to 3.0. ### Claim 3 (depends on 2) A stamp ink for stencil printing as claimed in claim 2, wherein the stamp ink is made by adding the coloring-agent to the resin and the oil-based solvents to form a mixture breaking down and dispersing the mixture, and then adding, to the mixture, amounts of the resin and the oil-based solvents that allow the stamp ink to develop the viscosity in the range from 20 to 250 poises at the shear rate of 20/sec and to develop the thixotropy index T.I. in the range from 1.2 to 3.0. ### Claim 4 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the stamp ink further includes a thixotropic agent. ### Claim 5 (depends on 4) A stamp ink for stencil printing as claimed in claim 4, wherein the stamp ink is made from the coloring-agent, the resin, the oil-based solvent, and the thixotropic agent with the amount of the thixotropic agent allowing the stamp ink to develop the viscosity in the range from 20 to 250 poises at the shear rate of 20/sec and to develop the thixotropy index T.I. in the range from 1.2 to 3.0. ### Claim 6 (depends on 4) A stamp ink for stencil printing as claimed in claim 4, wherein the thixotropic agent comprises a material selected from the group consisting of aluminum stearate, aluminum octylate, aluminum oleate, aluminum naphthenate, ethyl acetoacetate aluminum diisopropylate, alkyl acetoacetate aluminum diisopropylate, higher fatty acid amides, extender pigments, silica gel, and class four ammonium salts of montmorillonite. ### Claim 7 (depends on 6) A stamp ink for stencil printing as claimed in claim 6, wherein the extender pigments are selected from the group consisting of talc, kaolin, calcium carbonate, and barium sulfate. ### Claim 8 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the stamp ink has the viscosity in a range from 50 to 200 poises at the shear rate of 20/sec and has the thixotropy index in the range from 1.2 to 2.5. ### Claim 9 (depends on 8) A stamp ink for stencil printing as claimed in claim 8, wherein the stamp ink has the viscosity in the range from 80 to 150 poises at the shear rate of 20/sec and has the thixotropy index in the range from 1.2 to 2.0. ### Claim 10 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the coloring-agent is a pigment. ### Claim 11 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the coloring-agent comprises a material selected from the group consisting of carbon black, red iron oxide, ochre, ultramarine blue, Prussian blue, insoluble azo dye, soluble azo dye, phthalocyanine, quinacridone, and oil-soluble dyes. ### Claim 12 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the resin comprises a material selected from the group consisting of rosin, rosin ester, rosin-modified phenol resin, alkyd resin, petroleum resin, and rosin-modified maleic resin. ### Claim 13 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the oil-based solvents have a low volatility. ### Claim 14 (depends on 1) A stamp ink for stencil printing as claimed in claim 1, wherein the oil-based solvents comprises a material selected from the group consisting of hydrocarbon solvents with a boiling point of 300.degree. C. or higher, petroleum solvents, synthetic oils obtained through polymerization of unsaturated hydrocarbons, and animal and vegetable oils. ### Claim 15 (depends on 14) A stamp ink for stencil printing as claimed in claim 14, wherein the petroleum solvents are selected from the group consisting of spindle oil, liquid paraffin, motor oil, gear oil, and machine oil, wherein the synthetic oils are obtained through polymerization of one of ethylene, propylene, and butene, and wherein the animal and vegetable oils are selected from the group consisting of castor oil, tall oil, soybean oil, olive oil, and whale oil.