Europäisches Patentamt (19) European Patent Office Office européen des brevets (11) EP 0 661 356 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int. Cl.7: C09D 11/02 of the grant of the patent: 26.04.2000 Bulletin 2000/17 (21) Application number: 94309878.0 (22) Date of filing: 28.12.1994 (54) Stencil printing emulsion ink Emulsions-Tinten für den Schablonendruck Emulsion d'encre pour l'impression par stencil (84) Designated Contracting States: (74) Representative: DE FR GB Jenkins, Peter David et al PAGE WHITE & FARRER (30) Priority: 27.12.1993 JP 33242293 54 Doughty Street London WC1N 2LS (GB) (43) Date of publication of application: 05.07.1995 Bulletin 1995/27 (56) References cited: EP-A- 0 609 076 GB-A- 1 454 899 (73) Proprietor: US-A- 4 585 815 RISO KAGAKU CORPORATION Tokyo (JP) • DATABASE WPI Derwent Publications Ltd., London, GB; AN 93-191705[24] & JP-A-5 117 565 (72) Inventor: Okuda, Sadanao (RICOH KK) 14 May 1993 Minato-ku, Tokyo (JP) • DATABASE WPI Derwent Publications Ltd., London, GB; AN 92-254063[31] & JP-A-4 170 475 (SEIKO EPSON CORP.) 18 June 1992 • DATABASE WPI Derwent Publications Ltd., London, GB; AN 92-265692[32] & JP-A-4 183 762 (SEISAN NIPPONSHA KK) 30 June 1992 Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 0 661 356 B1 Printed by Xerox (UK) Business Services 2.16.7 (HRS)/3.6 EP 0 661 356 B1 Description [0001] The present invention relates to a stencil printing emulsion ink. More specifically, it relates to a stencil print- ing emulsion ink which is excellent in drying property and temperature suitability and has high printed concentrations in 5 printed matters and the less bleeding and strike through thereof. [0002] A stencil printing is carried out by platemaking using a stencil printing sheet and passing an ink through the perforated portions to print on a body to be printed such as paper and the like. This stencil printing is easy in preparation of platemaking and, therefore, used in broad fields. [0003] As for a stencil printing ink, a water-in-oil(W/O) type emulsion ink is generally used, and pigments and resin 10 components are contained as a coloring agent in the oil phase component of the W/O type emulsion ink (Japanese Pat. Laid-Open Pub.Nos.61-255967, 64-14284, 4-132777, 5-117565, etc.). [0004] When a W/O type emulsion ink is printed on a body to be printed such as paper, first of all, an oil phase as an outer phase of the emulsion permeates into the body to be printed and then, a water phase as an inner phase thereof permeates and/or splashes. Since the oil phase contains pigment components in such a W/O type emulsion ink, 15 there was a problem that it takes a long time from the permeation of the ink to the drying thereof, the bleeding of the ink is readily occurred, the ink components permeate into the deep portion of the paper layer, and therefore, the strike through of the ink is readily occurred. [0005] Furthermore, since the oil phase contains a resin component for improving the stable dispersion of the pig- ments and the fixation thereof onto the paper and this resin component has its large viscosity change to temperature, 20 there were disadvantages in that it is hard to secure the viscosity stability of the ink to temperature and the permeation velocity of the ink into the paper is delayed due to the presence of the resin component. [0006] GB 1454899 discloses a water-in-oil emulsion dye containing a dispense dyestuff in the aqueous phase. US-A-2,839,412 discloses a water-in-oil emulsion ink containing a pigment in the aqueous phase. [0007] It is a main aim of the present invention to provide a stencil printing emulsion ink which solves the above- 25 mentioned problems of the prior art, improves the drying property of the ink and the temperature suitability, and has printing concentrations in the printed matters and less bleeding and strike through of the ink. [0008] The inventions to be claimed for patent in the present application will be as follows. (1) A stencil printing emulsion ink of a water-in-oil type having a water phase dispersed in an oil phase, wherein the 30 emulsion ink consists of 10 to 70% by weight of an oil phase and 90 to 30% by weight of a water phase, and the water phase contains a water-insoluble coloring agent having a mean particle diameter of 10µm or less. (2) A stencil printing emulsion ink according to the item (1), wherein the water-insoluble coloring agent is contained in the range from 1 to 30% by weight to the total amount of the emulsion ink; (3), A stencil printing emulsion ink according to the item (1), wherein the water phase further contains an oil-in- 35 water type resin emulsion and/or a water-soluble resin; (4), A stencil printing emulsion ink according the item (1), wherein no resin is contained in the oil phase; and (5), A stencil printing emulsion ink according to the item (3), wherein the water-soluble resin is contained in the range from 1 to 20% by weight as a reduced solid basis versus the total amount of an emulsion ink. 40 [0009] Since as an outer phase of the W/O type emulsion ink, the oil phase has its permeability which is larger and its surface tension which is lower than those of the water phase, respectively, the oil phase component permeates into the body to be printed in advance of the water phase and then the water phase permeates and/or splashes. [0010] In the W/O type emulsion ink of the invention, the permeability of the oil phase components into the body to be printed can be improved, since the water-insoluble coloring agent is contained in the water phase, there is no need 45 of containing not only the water-insoluble coloring agent but also the resin components for dispersing or fixing this in the oil phase. On the other hand, the water phase components cannot permeate into the interior of the body to be printed and are kept and dried on the surface thereof. As a result, the printing concentrations in printed matters are improved and the strike through and bleeding of the ink are prevented. [0011] In the case that any water-insoluble coloring agent is presented in the oil phase as shown in the prior art, 50 the permeation velocity of the oil phase components is lowered and the time required for the permeation and drying of the ink becomes longer. In the emulsion ink of the invention, however, the drying property of the ink is also improved since the permeation of the oil phase components are proceeded swiftly. [0012] Furthermore, since there is no need of containing any resin components in the oil phase, the temperature dependence of the ink can be lessened and the resulting stable ink feed becomes possible against any temperature 55 change. [0013] A Water-in-Oil (W/O) type emulsion ink of the invention is produced by adding gradually, ., a water phase (W) component of 90 - 30 % by weight to an oil phase (O) component of 10 - 70 % by weight and emulsifying the resulting mixture. 2 EP 0 661 356 B1 [0014] In the present invention, a water-insoluble coloring agent is contained in the water phase component. The mean particle diameter of the water-insoluble coloring agent is 10 µm or less and more preferably, 3 µm or less. [0015] When the mean particle diameter exceeds 10 µm, the W/O type emulsion ink becomes easily collapsive. Also, an added amount of the water-insoluble coloring agent is preferably in the range from 1 to 30 % by weight to the 5 total amount of the emulsion ink and, more preferably, in the range from 3 to 10 % by weight. [0016] As for a water-insoluble coloring agent, known pigments can be used, but it is preferable to use what has good affinity to water which is a main solvent. For example, carbon black and the like, such as furnace carbon black, lamp black, acetylene black and channel black, for monochrome color, metals such as copper, iron and titanium oxide, and organic pigments, such as ortho-nitroaniline black and the like, are exemplified. Also, various pigments generally 10 used for use of color can be applied. [0017] In a water phase component, an O/W type resin emulsion and/or a water-soluble resin are preferred to be contained so as to improve the dispersibility of the water-insoluble coloring agent and the sticking tendency of the same to paper. [0018] As an O/W type resin emulsion, for example, resin emulsion containing polyvinyl acetate, ethylene - vinyl 15 acetate copolymer, vinyl acetate - acrylic ester copolymer, polymethacrylate, polystyrene, styrene - acrylic ester copol- ymer, styrene - butadiene copolymer, vinylidene chloride - acrylic ester copolymer, polyvinyl chloride, vinyl chloride - vinyl acetate copolymer, polyurethane or the like, can be used. [0019] As a water-soluble resin, for example, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, polyvinyl pyrolidone, polyethylene - polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl 20 ether, polyacrylamide, gum arabic, starch, water-soluble polyurethane or the like can be used.