Riso Kagaku Corporation

Sadanao Okuda

Yoshihiro Hayashi

Takashi Isozaki

Takahito Tojima

Takashi Suzuki

Masato Ishikawa

Ryuji Higa

Hideo Watanabe

Hiromichi Yamada

Makoto Ishikawa

Takahiro Wakayama

Masakazu Kawano

Hirohide Hashimoto

Hiroyuki Ogawa

Satoru Komata

Hiroyasu Kato

Teruaki Ohkawa

Takao Kawabe

Ryuta Ono

Kenji Suzuki

A water-in-oil (W/O) emulsion ink for stencil printing is provided which is prevented from pigment aggregation and thus excellent in ink fixability, high in printing density and less declining in printing density even after printing many sheets. The emulsion ink has a ratio by volume of the water phase to liquid components of the oil phase (i.e., volume of water phase/volume of the liquid components of oil phase) in a range of 1.0 to 3.5, preferably 1.0 to 3.0 at 23&deg; C. The liquid components of the oil phase may be composed of a resin, a solvent and a surfactant. The oil phase can contain a pigment at a ratio by volume of 0.19 or less to the total volume of the oil phase. The pigment preferably has an average particle size of 0.02 to 1.5 (&mgr;m). The water phase preferably has an average particle size of 0.1 to 1.0 (&mgr;m). The ink is suitable for containing particles of organic pigments with non-uniform shapes and a large average particle size like copper phthalocyanine blue and diaxazine violet.

Emulsion ink for stencil printing

By preventing a deformation of printing drum of a rotary stencil printing apparatus caused at the time of printing, uniform printed images can be printed even under conditions such as low temperature and high-speed printing and even using an apparatus provided with a large-sized drum. That is, the invention provides a method for stencil printing which comprises winding a perforated stencil sheet around the peripheral wall of a cylindrical printing drum having an ink permeable peripheral wall and rotating around its central axis, supplying an ink to the peripheral wall from the inside of the drum at the time of rotation of the drum, and pressing a printing paper to the outer surface of the peripheral wall of the drum to transfer the ink to the printing paper through the stencil sheet, wherein the peripheral wall of the drum has such a strength that the peripheral wall shows a stress of 0.75 kgf/cm,or more, preferably 1.4 kgf/cm,or more when it is deformed by 0.1 cm in a direction towards its central axis and viscosity of the ink is 330 Pa&bull;s or lower, preferably 150 Pa&bull;s or lower. An apparatus for carrying out the stencil printing is also provided.

Method and apparatus for stencil printing

Provided is a water-in-oil (W/O) emulsion ink for stencil printing which is less in change of viscosity with time and can give always stable prints. The emulsion ink contains a resinous component having a free carboxylic acid group or a higher fatty acid in the oil phase, and contains a divalent or trivalent metal salt and a monovalent metal salt having alkalinity in the water phase, whereby an interfacial layer of the emulsion is strengthened to stabilize the emulsion. The resinous component is preferably an alkyd resin, a rosin-modified phenolic resin, a maleic acid resin and a rosin. The monovalent metal salt or the divalent or trivalent metal salt is preferably contained in at least an amount equivalent to the free carboxylic acid of the resinous component and the higher fatty acid contained in the oil phase. The resinous component or the higher fatty acid is contained in an amount of 0.5-30% by weight based on the total amount of the emulsion ink.

A water-in-oil (W/O) emulsion ink for stencil printing is provided, which is excellent in emulsion stability and drying, high in printing density and low in blurring and seep through. The W/O emulsion ink has an oil phase and a water phase, in which an acid anhydride containing water-soluble polymer is contained together with a water-insoluble colorant in said water phase. The acid anhydride containing water-soluble polymer is preferably an acid anhydride containing olefin copolymer, more specifically, an isobutylene-maleic anhydride copolymer, or an acid anhydride containing vinyl copolymer, more specifically, a styrene-maleic anhydride copolymer. Preferably, the oil phase comprises at least a solvent and an emulsifier, and the water phase comprises a water-in-oil (O/W) emulsion of resin and/or a water-soluble resin.

A W/O emulsion ink, which is superior in emulsion stability, causes no softening or separation even after stored for a long time, and can always provide prints of uniform quality, is provided. The emulsion ink has an oil phase and a water phase, in which said water phase has a pH of 6.0 to 12.0, preferably 7.0 to 9.0 at 23.degree. C. The emulsion ink may contain a water-insoluble colorant in the water phase and/or the oil phase. Preferably, the water phase has a pH buffer action.

A process for preparing a stencil printing emulsion ink which is a water-in-oil (W/O) emulsion having an oil phase and a water phase and containing a water-insoluble colorant in the water phase, is provided. The process comprises the steps of preparing an aqueous dispersion of said water-insoluble colorant separately from water or an aqueous solution of the remaining water phase components, and adding said aqueous dispersion and water or said aqueous solution separately to said oil phase for emulsification. The process is suitable to produce emulsion inks of various colors, particularly of mixed colors containing two or more colorants in the water phase with a fixed formulation of the oil phase.

Process and apparatus for preparing emulsion ink for stencil printing

An emulsion ink for stencil printing is disclosed which enlarges the selection region of a body to be printed on, improves the handling property and adds a building-up feeling and a brilliance to the printed letters and others by developing the drying property, sticking tendency and preservation stability of the ink. The emulsion ink for stencil printing is characterized by using an oil-in-water type resin emulsion as a water phase in the water-in-oil type emulsion ink consisting of an oil phase and a water phase, and it is further characterized in that the minimum film-making temperature for the oil-in-water type resin emulsion described above is 40.degree. C. or less and its compound ratio is 2-45 wt.% as a reduced solid basis of the total amount of the avaiable emulsion ink.

Emulsion inks for stencil printing

A stencil printing paper and a process for perforating and engraving the same having the advantages in that the production of the stencil printing paper is easy, the resulting production cost can be thereby reduced and there is no generation of any problem at a time of stencil-making. In a stencil printing paper constituted by laminating a solvent-soluble resin layer to a porous substrate, the present invention comprises a stencil printing paper containing an acetalized polyvinyl alcohol having an acetalization degree of 1-70 mol % and a process for perforating and engraving the stencil printing paper by a mixed solvent containing water and an alcohol type solvent.

Stencil printing sheet and process for stencil making the same

A print image treatment device is formed of a supply device for holding an excess ink removing liquid, the excessive ink removing liquid not dissolving in a printing ink forming a print image and having a lower surface tension than that of the printing ink; a rotating contact member having an outer surface, on which the excessive ink removing liquid is supplied from the supply device; a facing member situated under the contact member for nipping and carrying a printing sheet between the contact member and the facing member, an excessive printing ink forming the print image on a printing sheet being transferred to the excessive printing ink removing liquid when the printing sheet contacts the contacting member; a cleaning device contacting the contact member for removing the excessive printing ink with the excessive ink removing liquid; and a separation device receiving the excessive ink removing liquid with the excessive printing ink. The excessive ink removing liquid is separated from the printing ink having been transferred from the printing sheet. The separation device includes a filter having the thickness and air-flow resistance indicated below:

Print image treatment device

A print image treatment device is formed of a contact member which is coated on the peripheral surface with an excessive ink removing liquid incompatible with printing ink for forming a print image and having a lower surface tension than the printing ink, and is rotated in a specific direction, a facing member which serves to bring the printed side of a printed paper into contact with the excessive ink removing liquid by feeding the printed paper nipped between the contact member and the facing member, a supply means for supplying the excessive ink removing liquid to the peripheral surface of the contact member, and a cleaning means which contacts the peripheral surface of the contact member. The angle of the cleaning means from the tangent line of the peripheral surface is within a range of 5 to 60 degrees.

A stencil printing sheet is disclosed comprising a resin film and optionally a support for the resin film which is fixed to the resin film with an adhesive, wherein the resin film has a layer for preventing thermal fusion including a polyethylene wax and arranged on one surface thereof. The stencil printing sheet does not cause breakage of the resinous film during a perforating process even at a high printing speed using a thermal head, provides excellent perforation images, and exhibits a long-lasting, excellent resistance to thermal fusion.

Stencil printing sheet with thermal fusion preventing layer

A water-in-oil (W/O) emulsion ink for stencil printing having an oil phase and a water phase is provided, in which a pearlescent pigment is contained in said oil phase and/or said water phase in an amount of 1 to 20% by weight of the total weight of said emulsion ink. The pearlescent pigment has an average particle size of 1 to 30 .mu.m. The pearlescent pigment preferably has a hiding power of 1,000 cm.sup.2 /g or lower. A colorant may be contained in at least one of said oil phase and said water phase. The oil phase preferably contains a non-volatile solvent, a volatile solvent, and an emulsifier, and optionally a resin. The water phase preferably contains an oil-in-water (O/W) emulsion of resin and/or a water soluble resin. The emulsion ink provides glossy printed images regardless of types of paper, and is quick in drying.

A water-in-oil (W/O) emulsion ink for stencil printing is provided, which contains a water-insoluble colorant in the water phase, has the water phase dispersed finely and stably in the oil phase, and can provide prints high in printing density and glossiness. The water-insoluble colorant has an average particle size of 1 .mu.m or less, and is constituted by particles of 1 .mu.m or less in particle size in an amount of 50% or more on area basis of the total of the water-insoluble colorant. The emulsion ink is preferably formed by use of an emulsifier having an HLB of 1.5-6.0, and preferably contains a tertiary amine compound in the water phase as a dispersant for the water-insoluble colorant.

An water-in-oil (W/O) emulsion ink for stencil printing is provided, which is excellent in emulsion stability. The water-in-oil (W/O) emulsion ink has an oil phase and a water phase, in which a water-insoluble colorant is contained in said water phase, and said water-insoluble colorant comprises an insoluble azo pigment. The insoluble azo pigment contained in the water phase preferably has an average particle size of 1 .mu.m or less. The emulsion ink is preferably formed by use of an emulsifier having an HLB of 1.5-6.0, and the water phase preferably has a maximum particle diameter of 10 .mu.m or less.

A water-in-oil (W/O) emulsion ink for stencil printing, high in printing density, low in seep through and blurring and excellent in temperature stability, is provided, which contains carbon black as a water-insoluble colorant in the water phase, in which said carbon black has a pH value of 6 to 10. The carbon black is preferably 10 .mu.m or less in average particle diameter. The water phase may contain an oil-in-water (O/W) emulsion of resin and/or a water-soluble resin to improve dispersion of carbon black in water and its fixation to prints. The oil phase may be free from any resinous component.

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Tokyo, Japan

Sadanao Okuda