JPH1081846A - Stencil printing ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stencil printing ink in which the dispersedness of the pigment dispersion system and the emulsion system of the water phase are good and stable and which does not raise any troubles in a printing machine by using a combination of a polyglycerol fatty acid ester with a specified surfactant other than that. SOLUTION: This ink is a W/O emulsion stencil printing ink prepared by dispersing at least a pigment, a pigment dispersant, an emulsifier and water in a mineral oil or a vegetable oil and composed of about 10 to 90wt.% oil phase and about 90 to 10wt.% water phase, wherein a combination of 0.1-3wt.% polyglycerol fatty acid ester with 3-20wt.% another surfactant having an HLB of 1-8, desirably sorbitan fatty acid ester is contained. It is desirable that this ink has a viscosity of 100,000-500,000cP when measured with a cone plate viscometer at a shear rate of 10<-1> (1/sec).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stencil printing ink, and more particularly to a W / O emulsion ink for stencil printing.

[0002]

2. Description of the Related Art A general water-in-oil emulsion ink for stencil printing is an extremely complex and unstable system in which a solid pigment and liquid water are dispersed in oil serving as a dispersion medium. is there. When the pigment aggregates in the ink,
The secondary particle diameter becomes large, causing clogging, deterioration in permeability, reduction in image gloss, and the like. Further, when the emulsification system causes aggregation and coalescence, it causes a decrease in ink viscosity and macro phase separation (water separation). In order to solve these problems and provide a stable ink, a method using a polyglycerinoxy fatty acid ester as a surfactant (Japanese Patent Publication No. 3-78433) has been proposed.

[0003]

However, when polyglycerin fatty acid ester is used as a surfactant, the dispersibility of the pigment is good, but the viscosity of the emulsion is reduced.
It is considered that since the water phase particles are easily moved, the coalescence of the water phase particles is accelerated and water separation is likely to occur. Then, as a result, strike-through or bleeding due to excessive outflow of ink occurs. Further, as the flow characteristics, since the yield value is lower than the apparent viscosity, it is considered that a problem such as a tail leak or a side leak in the printing press may occur. From these, as emulsion ink for stencil printing,
An ink in which the pigment dispersion system and the emulsion system of the aqueous phase are simultaneously stable and have no trouble even in a printing machine has not been developed so far.

Accordingly, an object of the present invention is to provide a W / O for stencil printing in which the dispersion of the pigment dispersion system and the emulsion system of the aqueous phase is good and stable, and has no trouble even in a printing machine.
It is to provide a type emulsion ink.

[0005]

According to the present invention, at least a pigment, a pigment dispersant, an emulsifier and water are dispersed in a mineral oil or a vegetable oil.
In water-in-oil stencil emulsion inks composed of about 90% by weight and about 90% by weight of an aqueous phase, a polyglycerol fatty acid ester and an HLB value of 1 to 10 are used.
8. A stencil printing ink characterized by being combined with the surfactant of No. 8 above. Secondly, in the above-mentioned first, an HLB value of 1 other than polyglycerin fatty acid ester is used.
Stencil printing ink, wherein the surfactants of Nos. To 8 are sorbitan fatty acid esters. Third,
In the first or second, for the stencil printing, the blending amount of the polyglycerin fatty acid ester is 0.1 to 3% by weight, and the blending amount of the surfactant having an HLB value of 1 to 8 is 3 to 20% by weight. Let the ink provide. Fourth, in the above first, second or third, a cone plate type viscometer (φ30,
Shear rate 10 ^-1 (1/1 / cone angle 4 °)
The viscosity value of S) is from 100,000 cps to 500,000 cp
s is provided.

The present inventor has conducted various studies and studies in order to solve the above-mentioned problems of the prior art. By using the surfactant in combination, a pigment dispersion system and an emulsion system of an aqueous phase are simultaneously obtained, and a stencil printing ink having no trouble even in a printing machine has been obtained. The polyglycerin fatty acid ester is adsorbed on the pigment surface, imparts good dispersibility and fluidity, and makes the pigment particles excellent in preventing aggregation of pigment particles due to a steric hindrance effect. Thereby, clogging, deterioration of permeability, reduction of image gloss, and the like can be prevented. However, when this is used for an emulsifying system, the viscosity of the emulsion decreases, and the water phase particles move easily.
The coalescence of the aqueous phase particles is accelerated, and water separation is likely to occur. Then, as a result, strike-through or bleeding due to excessive outflow of ink occurs. Further, as the flow characteristics, the yield value is lower than the apparent viscosity, which causes a problem such as a tail leak or a side leak in the printing press.

Therefore, the above-mentioned polyglycerol fatty acid ester and the other polyglycerol fatty acid ester have an HLB value of 1 to 8, preferably 3
When used together with the surfactants of Nos. 6 to 6, both the pigment dispersion system and the emulsification system can produce a good dispersion state and a stable state, and the yield value of the emulsification system decreases as the polyglycerin fatty acid ester is used. Therefore, coalescence of the aqueous phases can be prevented, and tail leakage and side leakage in the printing press can be prevented. A surfactant having an HLB value lower than 1 has a weak emulsifying ability, while a surfactant having an HLB value higher than 8 makes it difficult to form a W / O emulsion. Particularly, the HLB value is 3-6.
With the surfactant described above, a W / O emulsion can be formed most stably.

As the surfactant having an HLB value of 1 to 8, sorbitan fatty acid ester is most effective. The sorbitan fatty acid ester not only stabilizes the emulsion by giving an appropriate yield value in terms of the flow characteristics of the ink, but also can provide the ink with the best prevention of tail leakage and side leakage.

In the stencil printing ink of the present invention, the amount of the polyglycerol fatty acid ester is 0.1 to 3% by weight,
Other than the above, the amount of surfactant having an HLB value of 1 to 8 is 3
The amount is desirably within the range of from 20 to 20% by weight, and the pigment can be dispersed and emulsified without excess or deficiency within the range of these amounts.

The stencil printing ink of the present invention preferably has an optimum viscosity range in terms of printing characteristics in a printing press.
The cone plate type viscometer (φ30, cone angle 4
The viscosity at a shear rate of 10 ^-1 (1 / S) measured according to (°) should be in the range of 100,000 cps to 500,000 cps. Within this viscosity range, the best image can be obtained. JP-A-7-150091 describes that polyglycerin fatty acid esters and sorbitan fatty acid esters can be employed as nonionic ones having an HLB value of preferably 1 to 7, but these may not be used in combination. Nothing is suggested.

[0011]

Next, the present invention will be described in more detail. The polyglycerin constituting the polyglycerin fatty acid ester used in the present invention has a polymerization mole number of 2 to 14,
For example, there are diglycerin, triglycerin, hexaglycerin, decaglycerin and the like.

The mineral oil used in the present invention includes, for example, petroleum solvents, liquid paraffin, spindle oil, light oil, kerosene, machine oil, gear oil, lubricating oil, motor oil and the like. Tall oil, corn oil, olive oil, rapeseed oil, castor oil, soybean oil, dehydrated castor oil, and the like. Also, polyisobutylenes, hydrogenated polydecenes, trimethylolpropane esters, neopentyl esters, pentaerythritol esters, siloxanes, silicones, fluorocarbons, alkyl-substituted diphenyl ethers, phthalate esters, phosphate esters And the like can also be used. A mixed solvent such as Isopar manufactured by Exxon Corporation or Nisseki Solvent manufactured by Nippon Oil Corporation may be used as the petroleum-based solvent. These oils may be used alone or in combination of two or more.

As the pigment, conventionally known pigments can be arbitrarily used, and examples thereof include carbon black, azo pigments, phthalocyanine pigments, nitroso pigments, nitro pigments, vat dye pigments, and mordant dye pigments. And pigments such as basic dye pigments, acid dye pigments, and natural dye pigments. These pigments may be added alone or as a mixture of two or more kinds.
It is 15% by weight, preferably 2 to 10% by weight.

As the surfactant other than the polyglycerin fatty acid ester, it is preferable to use a nonionic surfactant. Specifically, as the sorbitan fatty acid ester, sorbitan monolaurate, sorbitan monopalmitate, sorbitan sesquiole Ethates and polyoxyethylene sorbitan fatty acid esters are exemplified. In addition, glycerin fatty acid ester, propylene glycol fatty acid ester, pentaerythritol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyethylene alkyl ether, polyoxyethylene phytosterol ether, polyoxyethylene polyoxy Propylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene castor oil, polyoxyethylene hardened castor oil, polyoxyethylene lanolin derivative, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, polyoxyethylene alkylphenyl formaldehyde condensate, etc. Is exemplified. These may be added to the ink singly or as a mixture of two or more kinds as long as the effect is not impaired. The addition amount may be 3 to 20% by weight of the ink weight.

In the present invention, in addition to the above, a resin, a gelling agent, an antioxidant and the like can be added to the oil phase as long as the formation of the emulsion is not hindered. Further, a water-soluble polymer, an antiseptic / fungicide, a water evaporation inhibitor, an antifreezing agent, a pH adjuster, an electrolyte and the like can be added to the aqueous phase as long as the formation of the emulsion is not hindered. Note that water may be clean as long as tap water, ion-exchanged water, distilled water, or the like can be used.

The resin added to the oil phase is a binder resin that has been conventionally added for the purpose of fixing the pigment to the printing material, dispersing the pigment, and improving the aging stability of the ink. Therefore, it is sufficient to add a conventionally added resin, specifically, rosin, polymerized rosin, hydrogenated rosin,
Rosin esters, rosin-based resins such as hydrogenated rosin esters, rosin-modified resins such as rosin-modified phenolic resins, phenolic resins, petroleum resins, alkyd resins, rubber derivatives,
Polymerized castor oil or the like may be added alone or as a mixture of two or more. In addition, the amount of addition is 20% by weight or less of the ink weight,
Preferably, it may be 1 to 7% by weight.

As a pigment dispersant for dispersing one or more pigments, a polyglycerol fatty acid ester may be used alone or in combination with the above-mentioned nonionic surfactant for an emulsifier as long as its effect is not impaired. I can do it. In addition, alkylamine polymer compounds, aluminum chelate compounds, styrene-maleic anhydride copolymers, partial alkyl esters of polyacrylic acid, polyalkylene polyamine aliphatic polycarboxylic acids, polyethers, ester-type anionic surfactants Agents, long-chain amine salts of high molecular weight polycarboxylic acids, polyamides, phosphate surfactants, alkyl sulfocarboxylates, α-olefin sulfonates, dioctyl sulfosuccinates, and the like can also be used in combination.

The gelling agent has a role of gelling the resin contained in the oil phase to improve the storage stability and fixability of the ink. The gelling agent added to the ink of the present invention includes:
Compounds that coordinate with the resin in the oil phase are preferred. Illustrative of such compounds are Li, Na, K, Al, Ca, Co, F
e, organic salts containing metals such as Mn, Mg, Pb, Zn, and Zr, organic chelate compounds, metal soap oligomers, and the like.Specifically, metal octylates such as aluminum octylate, manganese naphthenate, etc. Examples include metal salts of naphthenic acid, stearates such as zinc stearate, and organic chelate compounds such as aluminum diisopropoxide monoethyl acetoacetate. One or two of these gelling agents may be used.
More than one seed may be added to the oil phase, and the amount added is 15% by weight or less, preferably 5 to 10% by weight of the resin in the oil phase.

Antioxidants added to the oil phase include dibutylhydroxytoluene, propyl gallate, butylhydroxyanisole, and the like. The addition of these additives prevents oxidation of the binder resin and the like in the oil phase, thereby reducing the viscosity of the ink. Ascent is prevented. The amount of addition is 2% by weight or less, preferably 0.1 to 1.0% by weight of the oil in the ink. The antioxidants may be used alone or in combination of two or more.

The water-soluble polymer added to the aqueous phase of the emulsion ink is added for moisturizing and thickening. Specifically, the following natural or synthetic polymers are added. Natural polymers such as starch, mannan, sodium alginate, galactan, tragacanth gum, gum arabic, pullulan, dextran, xanthan gum, glue, gelatin, collagen, casein, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxy Methyl starch, carboxymethyl starch, semi-synthetic polymers such as dialdehyde starch, polyacrylic acid, sodium polyacrylate, acrylic resin derivatives such as polyethanol triethanolamine, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyethylene oxide,
Synthetic polymers such as polyvinyl methyl ether. These water-soluble polymers may be used alone or as a mixture of two or more kinds, and are added in an amount of 25% by weight or less, preferably 0.5 to 15% by weight of water contained in the ink.

The antiseptic / fungicide added to the aqueous phase is added to prevent the growth of bacteria and mold in the emulsion. When the emulsion is stored for a long period of time, the antiseptic / fungicide is usually added. is there. The amount of addition is 3% by weight or less of water contained in the ink, preferably 0.1 to 1.2% by weight. In addition, as antiseptic and fungicides, salicylic acid, phenols, methyl p-oxybenzoate,
In addition to an aromatic hydroxy compound such as ethyl p-oxybenzoate and its chlorine compound, sorbic acid, dehydroacetic acid and the like are used, and these may be used alone or in combination of two or more.

The water evaporation inhibitor and the antifreezing agent can be used in combination. Chemicals added for these purposes include glycols such as ethylene glycol, diethylene glycol and propylene glycol, methanol, ethanol, isopropanol, butanol and isobutanol. And lower polyhydric alcohols such as glycerin and sorbitol. One or more of these chemicals may be added, and the added amount is 15% by weight or less, preferably 4 to 12% by weight of the weight of water in the ink.

The pH adjuster added to water is triethanolamine, sodium acetate, triamylamine, etc. If necessary, these pH adjusters are added to add p
H can be maintained at 6 to 8. If the pH of the aqueous phase is out of the above range, there is a problem that the effect is lost when a water-soluble polymer for a thickener is added.

The electrolyte added to the aqueous phase is added to enhance the stability of the emulsion. Therefore, it is preferable to add an electrolyte composed of ions having a high liquid-separation sequence effective for improving the stability of the emulsion. Anions with high syneresis are citrate ions,
Tartrate ion, sulfate ion, acetate ion, etc., and the cation having a high liquid separation order is an alkali metal ion or an alkaline earth metal ion. Therefore, at least one of the anion and the cation is added as the electrolyte added here. A salt composed of the above-mentioned ions is preferable. Therefore, as the electrolyte added here, magnesium sulfate, sodium sulfate, sodium citrate, sodium hydrogen phosphate, sodium borate, sodium acetate, and the like are preferable. 0.1 to 2% by weight, preferably 0.5 to 1.5% by weight
It is.

In addition to the above, the water-in-oil emulsion ink for stencil printing of the present invention has an oil phase for improving the separation between the printing paper and the printing drum during printing or for preventing the printing paper from rolling up. Can be added with wax. Further, to the aqueous phase, triethanolamine, sodium hydroxide, or the like can be added to further increase the viscosity by adding a water-soluble polymer. Further, by adding a rust inhibitor or a defoaming agent to the aqueous phase, it is possible to prevent the printing press from rusting or bubbling of the ink during printing. Known additives added to the stencil printing ink may be added as necessary, and the amount of these additives may be about the same as that of the conventional product.

The emulsion ink of the present invention may be prepared by preparing an oil phase and an aqueous phase liquid in the same manner as in the conventional emulsion ink production, and emulsifying both of them in a known emulsifier to form an ink. That is, an oil in which additives such as a coloring agent, an emulsifier, and a resin to be added as needed are well dispersed is adjusted by an ordinary method, and an antiseptic / fungicide, a water-soluble polymer, and the like are optionally added thereto. What is necessary is just to gradually add and emulsify the added aqueous solution.

[0027]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 0.5 part by weight of polyglycerin fatty acid ester Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil with a viscosity of 240 mPa · S at 20 ° C.) 10.0 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 5.0 parts by weight Water 70.0 parts by weight , Carbon black, titanium oxide, polyglycerin fatty acid ester, Nisseki A oil, Nisseki B oil, alkyd resin, and sorbitan sesquiolate were mixed, and the mixture was dispersed with a three-roll mill to obtain an oil phase. As for the oil phase,
A mill base may be prepared from polyglycerin fatty acid ester, pigment and oil, and each additive may be mixed with the mill base to form an oil phase. While stirring this oil phase with a stirring machine,
Water was gradually added and emulsified to obtain a W / O emulsion ink. Using this emulsion ink, printing was performed with a stencil printing machine (VT-3820) manufactured by Ricoh Company to obtain a printed image. In addition, regarding this ink and printed image,
The viscosity, permeability, bleeding, buttocks leakage and the like were evaluated. The ink viscosity was measured at a shear rate of 10 using a CV-20 manufactured by HAAKE.
^It was measured at a value of ^-1 (1 / S). Permeability is the fixing rate of printed image (image density after 10 round trips of eraser / initial image density)
Was measured. The bleeding was evaluated by visually observing the printed image after accelerating the change with time at 60 ° C. for one month. The tail leakage was evaluated by the amount of ink at the rear end of the master after printing. The HLB value is the value of the surfactant used for emulsification.

Example 2 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 0.5 part by weight of polyglycerol fatty acid ester Nisseki A oil (mineral oil 20 having a viscosity of 80 mPa · S) C) 5.5 parts by weight Nisseki B oil (mineral oil with a viscosity of 240 mPa · S at 20 ° C) 10.0 parts by weight Alkyd resin 3.0 parts by weight Polyoxyethylene castor oil 5.0 parts by weight Water 70.0 parts by weight Using the formulation, an ink was prepared in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

Example 3 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 0.05 part by weight of polyglycerol fatty acid ester Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 10.45 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 5.0 parts by weight Water 70.0 parts by weight An ink was prepared from the product in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

Example 4 Carbon black (colorant) 0.5 parts by weight Titanium oxide (colorant) 5.5 parts by weight Polyglycerol fatty acid ester 0.5 part by weight Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 12.5 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 2.5 parts by weight Water 70.0 parts by weight An ink was prepared from the product in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

Example 5 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 0.5 parts by weight of polyglycerin fatty acid ester Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 16.0 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 4.0 parts by weight Water 65.0 parts by weight An ink was prepared from the material in the same manner as in Example 1,
The same evaluation as in Example 1 was performed.

Example 6 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 0.5 parts by weight of polyglycerin fatty acid ester Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 6.0 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 6.0 parts by weight Water 73.0 parts by weight An ink was prepared from the product in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

Comparative Example 1 Carbon black (colorant) 0.5 parts by weight Titanium oxide (colorant) 5.5 parts by weight Polyglycerol fatty acid ester 0.5 part by weight Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) C) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 10.0 parts by weight Alkyd resin 3.0 parts by weight Polyoxyethylene sorbitan monooleate 5.0 parts by weight Water 70.0 parts by weight Part An ink was prepared from the above composition in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

Comparative Example 2 0.5 parts by weight of carbon black (colorant) 5.5 parts by weight of titanium oxide (colorant) 5.5 parts by weight of polyglycerin fatty acid ester Nisseki A oil (mineral oil having a viscosity of 80 mPa · S 20) 5.5 ° C.) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 10.0 parts by weight Alkyd resin 3.0 parts by weight Water 70.0 parts by weight An ink was prepared in the same manner, and the same evaluation as in Example 1 was performed.

Comparative Example 3 Carbon black (colorant) 0.5 parts by weight Titanium oxide (colorant) 5.5 parts by weight Nisseki A oil (mineral oil having a viscosity of 80 mPa · S at 20 ° C.) 5.5 parts by weight Nisseki B oil (mineral oil having a viscosity of 240 mPa · S at 20 ° C.) 10.0 parts by weight Alkyd resin 3.0 parts by weight Sorbitan sesquiolate 5.5 parts by weight Water 70.0 parts by weight Same as Example 1 with the above composition. , And the same evaluation as in Example 1 was performed.

Table 1 shows the results of Examples 1, 2, 3, 4, 5, and 6 and Comparative Examples 1, 2, and 3.

[0038]

[Table 1] * Rank ◎: Good ○: Somewhat good □: Normal △: Somewhat bad ×: Bad

As is clear from Table 1, Example 1 is an ink satisfying all of claims 1 to 4. Permeability,
Good ink for both bleeding and buttocks leakage. Example 2 is an ink that does not satisfy only claim 2. Polyoxyethylene castor oil was used as the activator, and bleeding and buttocks leakage were slightly inferior to those in Example 1. This is due to the properties of the activator, and has a function of slightly lowering the viscosity as compared with the sorbitan fatty acid ester. Further, it is considered that coalescence of the aqueous phase is slightly promoted due to the low viscosity.

Example 3 is an ink that does not satisfy claim 3 alone. In particular, the amount of the polyglycerin fatty acid ester used is less than the range of claim 3.
When the amount of the polyglycerin fatty acid ester used is less than 0.1, it indicates that the permeability is slightly inferior. this is,
This indicates that the dispersibility of the pigment is slightly inferior to that of Example 1. If the polyglycerin fatty acid ester is more than the range of (3), no further effect is exhibited,
Conversely, the ink becomes disadvantageous in terms of cost and the like.

Example 4 is also an ink that does not satisfy only claim 3, but is an ink in which the amount of a surfactant used as an emulsifier is smaller than that of claim 3. As a result, the particle size of the aqueous phase becomes slightly larger, so that the viscosity is slightly lowered, and as a result, bleeding and buttocks leakage are slightly deteriorated. If the amount of the emulsifier is larger than the range of the third aspect, no further effect is exhibited, and conversely, the ink becomes disadvantageous in terms of cost and the like.

Example 5 is an ink which does not satisfy only claim 4. If the viscosity is lower than the range of claim 4, bleeding and buttocks leakage are slightly deteriorated. It is conceivable that the stability of the emulsion system of the ink and the matching property with the machine are slightly deteriorated. Example 6 is also an ink that does not satisfy only claim 4, and has a viscosity higher than that of claim 4. Therefore, the permeability is poor.

Comparative Example 1 does not correspond to claim 1 and has an HLB value of 15. This does not form a W / O emulsion and results in an O / W emulsion. O /
In a W emulsion, when the dispersion medium phase is water, the water phase in contact with the outside air evaporates quickly, and the balance between the oil phase and the water phase of the ink tends to be lost. In addition, it is not suitable for ink for stencil printing presses because mechanical problems occur. In Comparative Example 2, both the pigment dispersant and the emulsifier were all polyglycerol fatty acid esters. This results in an ink having a very low yield value and a high plastic viscosity due to the physical properties of the ink, so that bleeding and tail leakage are very poor. In Comparative Example 3, both the pigment dispersant and the emulsifier were all sorbitan fatty acid esters. This is contrary to Comparative Example 2,
An ink having a very high yield value and a low plastic viscosity results in an ink having very poor permeability. From the above, by satisfying the conditions of the present invention, it is possible to obtain a good emulsion ink having excellent permeability and free from inconveniences such as bleeding and buttocks leakage.

[0044]

The emulsion ink for stencil printing of the present invention comprises polyglycerin fatty acid ester and HL
By using a surfactant having a B value of 1 to 8 in combination, the polyglycerin fatty acid ester is adsorbed on the pigment surface and has a good dispersibility and fluidity, and also has an action of preventing the collection of pigment particles due to a steric hindrance effect. I do. Thereby, clogging, deterioration of permeability, reduction of image gloss, and the like can be prevented. In addition, other surfactants prevent the viscosity of the emulsified system, the decrease of the yield value, thereby preventing the coalescence of the aqueous phase particles,
Water separation can be prevented. Therefore, as a result, strikethrough or bleeding due to excessive ink ejection can be prevented, and furthermore, problems such as tail leakage and side leakage in the printing press, which occur due to a low yield value, can be prevented.

Claims (4)

[Claims] 1. A water-in-oil droplet comprising at least a pigment, a pigment dispersant, an emulsifier and water dispersed in a mineral oil or a vegetable oil and comprising about 10 to 90% by weight of an oil phase and about 90 to 10% by weight of an aqueous phase. What is claimed is: 1. A stencil printing ink, comprising a polyglycerol fatty acid ester and a surfactant having an HLB value of 1 to 8 in combination. 2. The stencil printing ink according to claim 1, wherein the surfactant having an HLB value of 1 to 8 other than the polyglycerin fatty acid ester is a sorbitan fatty acid ester. 3. The compounding amount of the polyglycerol fatty acid ester is 0.1 to 3% by weight, and the HLB value is 1 to 8 in other cases.
The amount of the surfactant is 3 to 20% by weight.
Or the ink for stencil printing according to 2. 4. The viscosity value at a shear rate of 10 ⁻¹ (1 / S) measured with a cone plate type viscometer (φ30, cone angle 4 °) is 100,000 cps to 500,000 cps. Stencil printing ink.