JPH10140067A - Emulsion ink for mimeograph printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsion ink for mimeograph printing that has a high printing conceptration without blur in characters or solid part with reduced blotting and print-through in a water-in-oil(W/O) type emulsion ink containing a water-insoluble coloring agent in the water phase. SOLUTION: This water-in-oil(W/O) type emulsion ink contains the water insoluble coloring agent in the water phase as well as contains another coloring agent in the oil phase. The coloring agent in the oil phase may be a pigment and/or a dye and the amount of the coloring agent in the oil phase is preferably 0.1-500wt.% based on the coloring agent in the water phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsion ink for stencil printing, and more particularly to an emulsion ink for stencil printing which has a high print density, does not blur characters and solid portions, and has little bleeding or strikethrough.

[0002]

2. Description of the Related Art In stencil printing, stencil printing is performed using a stencil sheet, and ink is passed through a perforated portion of the stencil sheet to perform printing on a printing material such as paper. This stencil printing is used in a wide range of fields because of easy production of the stencil. Conventionally, as a stencil printing ink, a water-in-oil (W / O) emulsion ink has been generally used, and a pigment component as a colorant is contained in the oil phase component (Japanese Patent Application Laid-Open No. Sho 61-61). No. 2559597, JP-A-64-14284, JP-A-4-132777
JP, JP-A-8-34944, JP-A-8-21
No. 8025). In addition, Japanese Patent Application Laid-Open No. Hei 5-11756
No. 5 proposes adding a trace amount of a water-soluble dye to the aqueous phase of this type of emulsion ink to obtain a toned emulsion ink without color separation.

[0003] When a water-in-oil (W / O) emulsion ink is printed on a printing medium such as paper, an oil phase component, which is an external phase of the emulsion, first permeates the printing medium, and then becomes an internal phase. The aqueous phase components penetrate and / or scatter. In conventional water-in-oil (W / O) emulsion inks in which the colorant is contained only in the oil phase component, much of the colorant permeates deep into the paper layer without remaining on the printing paper surface. As a result, there is a problem that the print density is reduced and that strike-through easily occurs. Further, there is a problem that bleeding is liable to occur due to penetration along the paper fiber.

[0004] In order to solve these problems, a water-in-oil (W / O) emulsion ink containing a water-insoluble colorant in an aqueous phase has been proposed (see JP-A-7-188598). In this form of the emulsion ink, the water-insoluble colorant is contained in the aqueous phase component, and thus remains on the surface of the printing paper. As a result, it is possible to obtain a printed matter having a high print density and less strikethrough or bleeding. That is, a printed matter having a large difference in shading between the image portion and the non-image portion and having a clear boundary is obtained.

[0005]

However, when such an ink is used, the transferred portion and the non-transferred portion of the ink are clearly distinguished. There is a problem that the thin line breaks are conspicuous.

An object of the present invention is to provide an emulsion ink for stencil printing which solves the above-mentioned problems of the prior art, has a high print density of printed matter, does not blur characters and solid portions, and has little bleeding or strikethrough. It is in.

[0007]

According to the present invention, the object is to provide a water-in-oil (W / O) containing a water-insoluble colorant in an aqueous phase.
This is achieved by a stencil emulsion ink, which further comprises a colorant in the oil phase.

That is, the present invention is characterized in that in a water-in-oil (W / O) emulsion ink containing a water-insoluble colorant in an aqueous phase, the oil phase also contains a colorant.

In the W / O emulsion ink, the oil phase component, which is the external phase, has a higher permeability than the aqueous phase component and has a lower surface tension, so that the oil phase component is coated on paper or the like before the aqueous phase component. Penetrates into the print, followed by the aqueous phase component and / or
Or scatter. In the water-in-oil (W / O) emulsion ink of the present invention, since most of the water-insoluble colorant contained in the aqueous phase remains in the ink transfer portion, the print density is not accompanied by strikethrough or bleeding. Has the effect of improving The colorant in the oil phase component penetrates into the printing paper together with the other oil phase components, coloring not only the ink transfer area but also the area immediately around it. It has the effect of preventing the occurrence of cutting. further,
When the pigment is contained in the oil phase component, an effect of improving the stability of the emulsion by increasing the viscosity of the oil phase and adsorbing the pigment on the emulsion interface is expected.

The water-in-oil (W / O) emulsion ink of the present invention usually contains 90 to 3% by weight of an oil phase of 10 to 70% by weight.
It can be produced by gradually adding and emulsifying 0% by weight of an aqueous phase.

In the present invention, the aqueous phase basically comprises water and a water-insoluble colorant. The average particle size of the water-insoluble colorant is preferably 10 μm or less, more preferably 3 μm or less, and most preferably 0.5 μm or less. If the average particle size exceeds 10 μm, the water-in-oil (W / O) emulsion tends to collapse. The addition amount of the water-insoluble colorant is preferably from 1 to 30% by weight, more preferably from 2 to 10% by weight, based on the total amount of the emulsion ink.

As the water-insoluble colorant, known pigments and disperse dyes of various colors are used. For example, carbon blacks such as furnace carbon black, lamp black, acetylene black, and channel black; and inorganic oxides such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese, nickel, and sulfides. Pigments, azo, phthalocyanine, dye, condensed polycyclic, nitro, nitroso, alkali blue, aniline black and other organic pigments, azo, anthraquinone,
Disperse dyes such as azomethine and nitro are used.

The water phase in the present invention may contain an oil-in-water (O / W) type resin emulsion and / or a water-soluble resin, if necessary. By including these in the aqueous phase, the dispersibility of the water-insoluble colorant and the fixability of the water-insoluble colorant to a printing medium such as paper can be improved.

Examples of the O / W type resin emulsion include polyvinyl acetate, ethylene-vinyl acetate copolymer,
Vinyl acetate-acrylate copolymer, polymethacrylate, polystyrene, styrene-acrylate copolymer, styrene-butadiene copolymer, vinylidene chloride-acrylate copolymer, polyvinyl chloride, vinyl chloride- Resin emulsions such as vinyl acetate copolymers and polyurethanes are used.

Examples of the water-soluble resin include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl pyrrolidone, polyethylene-polyvinyl alcohol copolymer, polyethylene oxide, polyvinyl ether, polyacrylamide, gum arabic, starch, water-soluble resin. Polyurethane is used.

The addition amount of these oil-in-water (O / W) resin emulsions and / or water-soluble resins is preferably 1 to 20% by weight, in terms of solids, based on the total amount of the emulsion ink, and 2 to 10% by weight. Is more preferable. If the amount is less than 1% by weight, the dispersibility or fixability of the colorant component in the aqueous phase cannot be sufficiently obtained. In some cases, the passage of ink is prevented, which is not preferable.

Further, the aqueous phase component includes anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants as dispersants for improving the wettability and dispersibility of the water-insoluble colorant in water. Surfactants, polymer-based, silicone-based, and fluorine-based surfactants;
It is preferable to add a tertiary amine compound as described in JP-A-34944 or an acid anhydride-containing water-soluble polymer as described in Japanese Patent Application No. 8-177518.

Of these dispersants, a tertiary amine compound or a water-soluble polymer containing an acid anhydride is particularly preferred. By using such a compound as a dispersant, a water-insoluble colorant can be finely and stably dispersed in an aqueous phase. W / which has improved image quality (color appearance) due to fine dispersion of the water-insoluble colorant and has excellent emulsion stability.
An O-type emulsion ink is obtained. As a dispersant, a carboxyl group, a functional group such as a sulfonic acid group in the molecule, when a general polymer compound that is adsorbed on the pigment surface is used, the disintegration of the emulsion is likely to occur. It is considered that the polymer compound is adsorbed on the interface between the oil phase and the aqueous phase, thereby reducing the stability of the emulsion.

As the tertiary amine compound, for example,
High molecular compounds such as polyvinylpyrrolidone, polyethyleneimine, alkylolamine salt, and poly N-acroylpyrrolidine are exemplified.

The acid anhydride-containing water-soluble polymer can be selected, for example, from acid anhydride-containing olefin copolymers and acid anhydride-containing vinyl copolymers, and salts and esters thereof. Examples of the acid anhydride-containing olefin copolymer include a copolymer of an ethylenically unsaturated monomer having an acid anhydride group such as maleic anhydride and an olefin such as ethylene or isobutylene. As the acid anhydride-containing vinyl copolymer, an ethylenically unsaturated monomer containing an acid anhydride group such as maleic anhydride,
A copolymer with an aromatic vinyl monomer, a vinyl ester monomer or a vinyl ether monomer is exemplified. As the aromatic vinyl monomer, styrene, α-methylstyrene,
Examples include p-methylstyrene, vinyltoluene, p-butylstyrene, vinylnaphthalene, vinylanthracene, p-arylsulfoxyaminostyrene, and p-styrenesulfonic acid. Examples of the vinyl ester monomer include vinyl acetate, acrylic acid, acrylate and methacrylate. Examples of the vinyl ether monomer include methyl vinyl ether.
Of these, preferred acid anhydride-containing water-soluble polymers include isobutylene-maleic anhydride copolymer and styrene-maleic anhydride copolymer.

The amounts of the tertiary amine compound and the acid anhydride-containing water-soluble polymer are not particularly limited. However, since these compounds are generally high molecular compounds, the thickening effect is remarkable as the amount used increases. Becomes In such a case, the water-insoluble colorant is finely dispersed in the aqueous phase, and the necessary minimum amount that can be stably dispersed is sufficient. Therefore, it is preferable to appropriately determine the amount of the colorant to be used depending on the dispersant. .

Further, a water-soluble coloring agent may be added to the aqueous phase. Examples of the water-soluble colorant include basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes,
Of mordant dyes, reactive dyes, vat dyes, sulfur dyes, etc.,
Water-soluble dyes and dyes that have become water-soluble by reduction or the like are used.

The aqueous phase may further include, if necessary,
Water-soluble additives such as an electrolyte, a pH adjuster, a wetting agent, a water evaporation inhibitor, an antifreezing agent, a preservative, a fungicide, and an antioxidant can be contained.

The oily phase in the present invention comprises a coloring agent, a non-volatile solvent, a volatile solvent, an emulsifier and the like.

As the colorant contained in the oil phase component, a pigment and / or a dye is used. When a pigment is used, the same known pigment as described above is used. As the dye, those which are insoluble in the aqueous phase and stably exist in the oil phase are preferable, and known oil-soluble dyes and the like are used. For example, azo-based, anthraquinone-based, azine-based oil-soluble dyes are used. The particle size of the colorant added to the oil phase is not particularly limited, and may be 10 μm or more, unlike the case of the aqueous phase.

The colorant in the oil phase component is preferably 0.1 to 500% by weight based on the colorant in the aqueous phase component.
More preferably, the dye is 0.5 to 20% by weight and the pigment is 5 to 4% by weight.
00% by weight. If the amount is less than this range, the coloring power of the colorant in the oil phase is insufficient, and the image quality is deteriorated, such as a noticeable solid white spot. Conversely, if the value exceeds this range, the image becomes worse, for example, bleeding is conspicuous.

As the non-volatile solvent, motor oil,
Spindle oil, machine oil, mineral oils such as liquid paraffin, olive oil, castor oil, vegetable oils such as salad oil are used, and as the volatile solvent, known mineral oil solvents,
Vegetable oil solvents are used.

The emulsifier is used for constituting a W / O emulsion, and a nonionic surfactant is preferably used. For example, sorbitan fatty acid esters such as sorbitan monooleate, sorbitan sesquioleate, sorbitan monoisostearate, glyceryl monostearate, decaglyceryl decaoleate, (poly) glycerin fatty acid esters such as hexaglyceryl pentaoleate, and these Ethylene oxide adducts, propylene glycol fatty acid esters, (poly) ethylene glycol fatty acid esters, and fatty acid / alkyl ether / alkylphenol / (hardened) castor oil ethylene oxide adducts. The aqueous phase component of the present invention may contain a surfactant for dispersing a water-insoluble colorant or a surfactant for constituting an O / W type resin emulsion. It is preferable to appropriately select an emulsifier so that the W / O emulsion is not disintegrated by the interaction with the agent or the like.

Further, it is preferable to use a resin as an oil phase component in order to improve the stability of the emulsion and to improve the dispersibility of the pigment and the fixability to paper. As the resin, rosin or rosin-modified resin, phenol resin, maleic resin, petroleum resin, rubber derivative resin, alkyd resin and the like are used.

Further, extenders may be contained in the aqueous phase and / or the oil phase. When the extender is contained in the ink, the extender stagnates on the surface of the printing paper, and the colorant in the aqueous phase and the oil phase can be more efficiently retained on the surface of the printing paper.

Examples of extenders include clay, talc, clay, diatomaceous earth, calcium carbonate, barium carbonate,
Inorganic fine particles such as barium sulfate, titanium oxide, alumina white, silica, kaolin, mica, and aluminum hydroxide, polyacrylate, polyurethane, polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polysiloxane, and phenol Organic fine particles such as a resin, an epoxy resin, and a benzoguanamine resin, and fine particles made of a copolymer thereof are used.

[0032]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In Examples and Comparative Examples, W / O emulsion inks were prepared according to the formulations shown in Table 1 by the following methods. In addition, the part in an example means a weight part.

Examples 1 and 2 First, an aqueous phase was prepared by mixing ion-exchanged water, ethylene glycol, furnace carbon black, and polyvinylpyrrolidone, and sufficiently dispersing the mixture in a ball mill. Next, furnace carbon black, alkyd resin, motor oil, Nisseki No. 5 solvent, and sorbitan monooleate were mixed and kneaded well with a three-roll mill to prepare an oil phase.
While gradually adding the aqueous phase to the oil phase, emulsification was carried out with a stirrer to obtain a stencil printing emulsion ink.

Example 3 First, an aqueous phase was prepared by mixing ion-exchanged water, ethylene glycol, furnace carbon black, and polyvinylpyrrolidone, and thoroughly dispersing the mixture in a ball mill. Next, furnace carbon black, nigrosine, alkyd resin, motor oil, Nisseki No. 5 solvent, and sorbitan monooleate were mixed and sufficiently kneaded with three rolls to prepare an oil phase. While gradually adding the aqueous phase to the oil phase, emulsification was carried out with a stirrer to obtain a stencil printing emulsion ink.

Comparative Example 1 First, an aqueous phase was prepared by mixing ion-exchanged water, ethylene glycol, furnace carbon black, and polyvinylpyrrolidone, and sufficiently dispersing the mixture in a ball mill. Next, an alkyd resin, motor oil, Nisseki No. 5 solvent, and sorbitan monooleate were mixed to prepare an oil phase. While gradually adding the aqueous phase to the oil phase, emulsification was carried out with a stirrer to obtain a stencil printing emulsion ink.

Comparative Example 2 Furnace carbon black, alkyd resin, motor oil, Nisseki No. 5 solvent, and sorbitan monooleate were mixed and thoroughly kneaded with a three-roll mill to prepare an oil phase. Emulsification was carried out with a stirrer while gradually adding a mixed solution of ion-exchanged water and ethylene glycol to the oil phase to obtain a stencil printing emulsion ink.

[0037]

[Table 1]

Stencil printing was performed using a stencil printing machine (Risograph GR375 (registered trademark) made by Riso Kagaku Kogyo Co., Ltd.) using the emulsion inks for stencil printing prepared in Examples 1 to 3 and Comparative Examples 1 and 2, respectively. The print density, strikethrough, bleeding property, fine line image, and solid image of the obtained printed matter were evaluated by the following methods, and the results are shown in Table 2.

(1) Print Density: The print density of the printed solid portion was measured with a reflection densitometer (RD 920, manufactured by Macbeth). (2) strike-through property: The back surface of the printed solid portion was visually observed. (3) Bleeding property: The bleeding state of the portion to which the ink was attached was observed using a microscope (× 80). (4) Fine line image: When the fine line break is inconspicuous,
In the case where the broken line was conspicuous and the character was faint, the evaluation was x. (5) Solid image: When a white point was not conspicuous in a solid portion, it was evaluated as ○, and when a white point was conspicuous, it was evaluated as x.

[0040]

[Table 2]

In Examples 1 to 3, good prints were obtained with high print density, less strike-through and bleeding, and no noticeable thin lines or solid blurring. In Comparative Example 1, the print density was high and strike-through and bleeding were small, but fine lines and solids were noticeably blurred. In Comparative Example 2, although fine lines and solid blurring were inconspicuous, the print density was low, and strikethrough and bleeding were large.

[0042]

According to the W / O emulsion ink of the present invention, since the water phase contains a water-insoluble colorant, a printed matter having a high print density without ink strikethrough or bleeding is obtained. Because, and the colorant is included in the oil phase,
A good image is obtained in which solid white points, fine characters and fine line breaks are inconspicuous.

Claims (3)

[Claims] 1. A water-in-oil (W / O) emulsion ink containing a water-insoluble colorant in an aqueous phase, further comprising a colorant in an oil phase. 2. The emulsion ink for stencil printing according to claim 1, wherein the colorant in the oil phase is a pigment and / or a dye. 3. The emulsion ink for stencil printing according to claim 1, wherein the colorant in the oil phase is 0.1 to 500% by weight based on the colorant in the aqueous phase.