JPH06116525A - Ink composition for stencil printing - Google Patents

Abstract

PURPOSE:To provide an ink composition reduced in set-off, excellent in abrasion resistance, containing a specified amount of specific solid particles. CONSTITUTION:The composition containing 0.1-1wt.% of solid particles 8-30mum in mean diameter (e.g. glass, wax).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition capable of significantly reducing set-off in an ink for stencil printing whose main drying means is permeation drying.

[0002]

2. Description of the Related Art In stencil printing inks, the main means of drying is to penetrate into paper, and a W / O emulsion ink in which water is emulsified to make it quick-drying is generally used. The phenomenon that ink adheres to the back surface when printed materials are piled up immediately after printing due to insufficient drying) is unavoidable. In order to improve this set-off, in JP-A-63-277287, the viscosity of the ink is defined to control the amount of ink transfer, and in JP-A-2-41376, curing and drying by ultraviolet rays are used. In Japanese Patent No. 86667, it is proposed to use a foam ink.
However, these have a problem that they are not sufficiently effective or require a special device.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a stencil printing ink which does not require a special device or the like and has significantly reduced set-off.

[0004]

[Constitution of the invention]

The present invention has an average particle size of 8 to
The present invention relates to a stencil printing ink composition containing 0.1 to 1% by weight of solid particles of 30 μm.

Since the thickness of the ink film immediately after printing on the stencil printing machine is about 2 to 10 μm, the set-off can be remarkably reduced by adding a small amount of solid particles having a diameter larger than that. That is, the added particles are in a form of protruding from the ink film, which prevents contact between the paper and the ink film which are overlaid. Actually, even particles having a particle diameter similar to the film thickness immediately after printing have an effect because the printed materials take a little time to be stacked and the ink penetrates and the film thickness becomes thin during that time.

As the component of the particles used, any component can be used as long as it does not dissolve in other ink components and can maintain the shape of the particles. Specifically, glass, inorganic materials such as ceramics, nylon, polyethylene, polypropylene,
There are polymer compounds such as polystyrene, PMMA, and polyester. In addition, waxes can be cited as ones that can reduce the set-off and improve the abrasion resistance at the same time. The particle size used is 8 to 30 μm. If it is smaller than this, the effect is small, and if it is large, it causes clogging of the plate. Further, a shape having a true spherical shape and a narrow particle size distribution is desirable because the clogging of the stencil printing plate is less likely to occur. The amount of solid particles added is preferably 0.1 to 1% by weight.
If the amount is small, the effect is not so great, and if the amount is large, the plate is likely to be clogged, and the roughness of the printing surface becomes a concern. Any other ink composition may be used as long as it does not dissolve or aggregate the added particles.

An ink for stencil printing to which solid particles are added is
Water-in-oil emulsions are preferred. Water-in-oil emulsion stencil printing ink is a fine dispersion of water droplets in an oil phase consisting of a solvent or a resin and a solvent.As the resin, alkyd resin, rosin-modified alkyd resin, rosin-modified phenolic resin, petroleum A resin or the like is used, and as the solvent, spindle oil is generally used, but an aliphatic solvent may be used. The water-in-oil type emulsion ink is a fine dispersion of an aqueous phase in an oil phase. The oil phase mainly comprises an organic solvent and a resin dissolved in the organic solvent, constitutes 15 to 45% by weight based on the total stencil printing ink, and contains a colorant, an emulsifier and the like. As the colorant, it is possible to use an inorganic pigment such as carbon black, titanium dioxide or navy blue, an organic pigment such as a phthalocyanine pigment, an insoluble azo pigment, a soluble azo pigment or a quinacridone pigment. The content of the colorant is 1 to 20% by weight based on the total ink.

As the emulsifier, HLB such as sorbitan fatty acid ester, glycerin or polyglycerin fatty acid ester and polyoxyethylene fatty acid ester is 1
Those of 0 or less can be used. In addition to water, the aqueous phase is ethylene glycol, in order to prevent freezing and evaporation.
Polyhydric alcohols such as glycerin and propylene glycol can be added. Further, in order to improve the emulsion stability of the ink, a water-soluble polymer such as methyl cellulose or carboxymethyl cellulose, a preservative, an electrolyte and the like can be added.

In the stencil printing ink of the present invention, a colorant is added to all or part of the oil layer component, and a three-roll mill,
The mixture is kneaded and dispersed with a disperser such as a sand mill, an emulsifier is added, and water is gradually added, while a water-in-oil emulsion is formed with a disperser such as a homomixer, a sand mill and a disper. The particle size of the finely dispersed aqueous phase is preferably 50 μm or less. An example will be described below.

[0010]

【Example】

Example 1 Fine Port PB-3011E manufactured by Sumitomo Chemical Co., Ltd. (a true spherical polystyrene particle having an average particle diameter of 11 μ) was mixed with Ricoh Preport Ink VT black ink (emulsion ink for stencil printing) using a mixer. 5% by weight was added to obtain the ink of the present invention. When 1000 sheets of this ink were printed by a single cylinder type stencil printer (Preport VT-3500 manufactured by Ricoh Co., Ltd.), a printed matter with very little set-off could be obtained.

Example 2 0.5% by weight of a spherical polyamide resin having an average particle diameter of 25 μm was added to a preport ink VT ink (emulsion ink for stencil printing) manufactured by Ricoh Co., Ltd. with a mixer to prepare the ink of the present invention. Got This ink was applied to a single cylinder stencil printer (Preport VT-3500 manufactured by Ricoh Co., Ltd.) for 10
When 00 sheets were printed, it was possible to obtain a printed material with very little set-off as in Example 1.

Comparative Example 1 When printing was carried out in the same manner as in the example without adding resin particles, there was some set-off.

Comparative Example 2 Fine Pearl PM305 manufactured by Sumitomo Chemical as in Example 1
When 0% (PMMA particles having an average particle diameter of 50 μm) was added at 1% and printing was performed, the plate was clogged on the 100th sheet, and image defects were recognized.

Comparative Example 3 Fine Pearl P manufactured by Sumitomo Chemical Co., Ltd. as in Example 1
When B-3006E (polystyrene particles having an average particle size of 6 μm) was added in an amount of 1% and printed, a decrease in set-off was slight.

[0015]

The ink composition for stencil printing according to the present invention can be used to obtain a printed matter with significantly less set-off by using a conventional printing machine without adding a special device.

Claims (1)

[Claims] 1. Solid particles having an average particle size of 8 to 30 μm
An ink composition for stencil printing containing 1 to 1% by weight.