Riso Kagaku Corporation

Masato Ishikawa

Yoshihiro Hayashi

Takashi Suzuki

Sadanao Okuda

Takahiro Wakayama

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.

Emulsion ink for stencil printing

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

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.

An 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 a water-insoluble colorant is contained in said water phase, and said oil phase comprises a solvent and an agent for thickening said solvent. The oil phase preferably has a viscosity at 23.degree. C. of 5-20,000 cps, more preferably 15-2,000 cps. The thickening agent may be a resin in an amount of 1-30%, preferably 2-25% by weight of the total of the ink, or may be oil-insoluble particulates or powders in an amount of 0.01-10%, preferably 0.1-5% by weight of the total of the ink.

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Inashiki-gun, Japan

Masato Ishikawa