JP2007084588A - Ink for mimeographic printing and method of mimeographic printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide mimeographic printing ink capable of regulating an excessive ink-transfer on a material to be printed and excellent in fine character sharpness and drying property. <P>SOLUTION: This ink for the mimeographic printing is provided by having ≤500 mPa s ink viscosity at 10 Pa by increasing shearing stress from 0 Pa by 0.1 Pa/s rate at 23°C, ≥30 mm stringiness length by pulling up a chromium steel ball having 15 mm diameter by 150 mm/s from the ink at 23°C and also ≥40 mN/m surface tension. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stencil printing ink, and more particularly to a stencil printing ink suitable for use in a rotary digital stencil printing machine.

Compared with printing methods such as offset printing, gravure printing and letterpress printing, the stencil printing method does not require complicated operations such as cleaning after use, and has excellent operability such as not requiring a specialized operator, Easy to use. Since the use of the thermal plate making system that uses a thermal head as a device, digitization of image processing has become possible in the stencil printing system, and high-quality printed materials can be easily obtained in a short time. Even more so, its convenience is recognized.
Rotary stencil printers with automatic control of stencil paper (master) plate making, plate making, discharging, ink supply and printing operations are widely used in offices and schools under the name of digital stencil printing machines. ing.

  Conventionally, water-in-oil (W / O) emulsion inks have been used as stencil printing inks. W / O emulsion ink has a function to suppress changes in the composition and physical properties of the ink even if the ink inside the printing press is in contact with the air when the printing press is left unused. Yes. That is, since the water that is the inner phase component of the emulsion ink is covered with the oil that is the outer phase component, its evaporation is suppressed.

The drying of the ink in the printed matter printed with the W / O type emulsion ink causes the emulsion to become oily by penetrating between the paper fibers of the printing paper that is the printing medium (printing medium) and contacting with the paper fibers. It is considered that the water is the main component of the ink and gradually evaporates in contact with the atmosphere and is gradually separated into a phase and an aqueous phase. However, since the water in the ink transferred to the printing medium cannot be brought into contact with the atmosphere within a short time after printing, the drying property immediately after printing depends on osmotic drying. Since the viscosity of the O-type emulsion ink is designed to be high to some extent, the penetration speed is not fast, and the ink drying property immediately after printing cannot be said to be sufficient.
Accelerating the drying of printed matter is an extremely important issue for stencil printing. This is because if the printed matter is not dried, the operator cannot handle the printed matter, and the advantage of “obtaining high-quality printed matter in a short time” of stencil printing cannot be fully utilized.

Therefore, various improvements have been made to improve the drying property of the printed matter. For example, an ultraviolet curable ink for stencil printing that is fixed and dried by ultraviolet irradiation is known (Patent Document 1). In addition, water-based inks for stencil printing have been developed from the viewpoints of environmental conservation and safety, and a stencil printing method is known in which a base is added to the printing surface immediately after printing to increase the permeability of water-based ink to paper. (Patent Document 2).
JP 2002-30238 A JP 2001-302955 A

However, when a drying method using a chemical reaction is used, a curing energy irradiation device, a reaction liquid coating device, energy for the device, and the like are required, and expensive raw materials must be contained in the ink.
In stencil printing, the ink passes through the perforated portion of the stencil sheet and is transferred to the surface of the printing sheet by the printing pressure when the stencil sheet and the printing sheet are pressed against each other. If the viscosity of the ink is lowered to increase the permeation rate of the ink, the ink will easily pass through the perforated part and the amount of ink transfer will be excessive, and fine images and fine lines will blur and a fine image will not be obtained and drying will be poor There was a problem.
Therefore, the present invention can control the amount of ink transferred to the printing medium even if the ink has a low viscosity, thereby printing a delicate image, as well as heat, light, and reactive substances. It is an object of the present invention to provide a stencil printing ink that can improve the drying property of printed matter without using special means such as application, apparatus, energy, and the like, and a stencil printing method using the same.

In the present invention, the ink viscosity at 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C. is 500 mPa · s or less. The present invention relates to a stencil printing ink having an ink string length of 30 mm or more when pulled up at / s and a surface tension of 40 mN / m or more.
Another embodiment of the present invention is a drum that is rotatable and has a stencil sheet mounted on the surface of its outer peripheral wall, an ink supply means for supplying ink from the upstream side of the maximum printing area of the outer peripheral wall of the drum, and a paper feed A stencil printing machine provided with a press roll that presses the printed printing medium against the outer peripheral wall, and presses the stencil sheet with the stencil sheet after making the stencil sheet by pressing it with the press roll while rotating the drum on which the stencil sheet has been made The present invention relates to a stencil printing method in which ink is passed from a perforated portion and transferred to a printing medium, and the stencil printing method uses the stencil printing ink according to the present invention as the ink.

In the stencil printing ink according to the present invention, the ink thread length and the surface tension are not less than the specific value, so that the amount of ink transferred to the printing medium can be further controlled even if the ink has a low viscosity. Can do.
Therefore, by using the stencil printing ink according to the present invention, it is possible to reliably control the amount of ink transfer, and as a result, improve the sharpness of the printed matter and further improve the drying performance. Obtainable.

The viscosity of the stencil printing ink according to the present invention (hereinafter, the stencil printing ink is simply referred to as “ink”) is 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C. Ink viscosity is 500 mPa · s or less, more preferably 300 mPa · s or less, and particularly preferably 100 mPa · s or less. Further, the ink viscosity measured in the same manner is preferably 1.5 mPa · s or more, more preferably 3.0 mPa · s or more, and further preferably 5.0 mPa · s or more.
By lowering the viscosity of the ink in this way, it is possible to improve the penetration speed of the ink into the printing medium, and it is possible to easily increase the drying property of the printed matter.

  When a chromium steel ball having a diameter of 15 mm is pulled up from ink at 150 ° C. at 23 ° C., the ink thread length is 30 mm or more, preferably 40 mm or more, and more preferably 50 mm or more.

  Specifically, the measurement of the kite length can be performed using a measuring instrument as shown in FIG. This measuring device includes a container 201 containing ink, a chromium steel ball 202 having a diameter of 15 mm, a stepping motor 203, and a belt 204. The chrome steel ball 202 is fixed to a belt 204 that is rotated by a stepping motor 203, and moves up and down at a constant speed. When the measurement environment is 23 ° C., the entire chromium steel ball 202 is immersed in the ink in the container 201 so that the upper part of the sphere coincides with the line of the ink level, and is pulled up at a speed of 150 mm per second. The situation is photographed and recorded using a photographing machine (not shown) installed in front of the measuring instrument, and the ink fountain just before the ink fountain formed between the ink surface and the steel ball is torn off. The maximum length (distance between the ink level and the bottom of the steel ball) is read from the recorded image.

  The reason why the amount of transfer to the printing paper is small in the ink having a long yarn length such that the yarn length by the measurement method is 30 mm or more can be considered as follows. That is, ink having a long string length has a property that the ink is not easily divided, that is, difficult to separate. Prior to the transfer of the ink to the printing paper, the ink must pass through the perforated portions of the stencil sheet as a pre-stage, so that ink having such physical properties is difficult to be pushed out from the perforated portions of the stencil sheet. it is conceivable that. Alternatively, even if the ink comes into contact with the printing paper, it is considered that the ink does not easily break up and is therefore difficult to transfer to the printing paper. For these or other reasons, it is believed that the amount of ink transferred to the printing paper is reduced.

  The upper limit of the thread length is not particularly limited, but is preferably 500 mm or less, more preferably 250 mm or less, and even more preferably 200 mm or less. If the thread length exceeds 500 mm, the amount of ink transfer is suppressed too much, and there is a risk that some fine characters and thin lines may be lost. If it exceeds 250 mm, the solid portion is uneven when there is a solid portion. May occur. The reason for this is not clear, but when the stencil sheet and the printing paper are separated, the ink transferred from the perforated portion of the stencil sheet to the printing paper attracts each other, and the formed image is attracted to each other. It is thought that unevenness will occur.

The surface tension of the ink (measured value at 25 ° C.) is set to 40 mN / m or more. The technical significance of defining the surface tension in this way is considered as follows.
The transfer of the ink to the printing paper is performed by applying pressure with a press roll during printing. At this time, it is considered that the transfer of the ink is proceeding at the same time due to the penetration of the ink into the printing paper accompanying the contact between the ink and the printing paper. The permeation of ink into the printing paper changes depending on the surface tension of the ink. When the surface tension of the ink is low, the ink easily penetrates into the paper. However, if the surface tension of the ink is too low, it is considered that when the printing paper comes into contact with the plate, the ink penetrates excessively into the printing paper and causes excessive transfer. In particular, when the viscosity of the ink is low, the influence of the surface tension becomes large.
Therefore, in the present invention, by defining the value of the surface tension in addition to the thread length, it is possible to further prevent the excessive transfer of the ink to the printing paper and to print an image with further excellent sharpness. it can.

The surface tension of the ink can be controlled by adding a water-soluble organic solvent, a surfactant or the like or adjusting the amount of the ink added.
The upper limit of the surface tension is not particularly limited, but is preferably 72 mN / m or less, and from the viewpoint of ensuring the wettability of the ink on the plate and the printing density of the first sheet after landing, 60 mN / m or less. It is preferable that
Therefore, by using an ink having a low viscosity, a string length of 30 mm or more, and a surface tension of 40 to 60 mN / m, the print density immediately after the plate is made appropriate, and the sharpness of the fine characters is improved. In addition, a printed matter having excellent drying properties can be obtained.

In addition, when the thread length and viscosity of a conventional commercially available emulsion ink for stencil printing were measured in the same manner as described above, “RISO SOY ink RP (black)” manufactured by Riso Kagaku Kogyo Co., Ltd. has a thread length of 25 mm, The viscosity was 1000 Pa · s (1 million mPs · s) or more, and the “ink type 400 (black)” manufactured by Ricoh Co., Ltd. had a kite length of 20 mm and a viscosity of 1000 Pa · s or more.
These inks suppress the amount of ink transfer by increasing the viscosity of the ink and increasing the flow resistance when the ink passes through the perforated portion of the plate. It is clear whether the ink is a novel ink having physical properties different from those of the ink.

The form of the ink is not particularly limited, such as a W / O type emulsion, but is preferably a water-based ink. The water contained in the ink tends to evaporate into the atmosphere immediately after printing, and the ink is pressed between the fibers of the printing paper and penetrates during printing. Since the water spreads rapidly and the water easily evaporates, the drying property of the printed matter can be further improved.
In the case of water-based ink, it is preferable that water, a colorant, and a spinnability imparting agent are contained.

  Water is preferably contained in the ink in an amount of 50% by weight or more, more preferably 65% by weight or more from the viewpoint of improving the drying property of the printed matter and controlling the string length and viscosity of the ink. preferable. On the other hand, the upper limit of the blending amount of water is not particularly limited, and may be set as appropriate from the balance with other blending components, and is preferably about 80% by weight or less, for example.

  As an ink colorant, a pigment or a dye can be used, and two or more kinds may be used in combination. Examples of the pigment include organic pigments such as azo, phthalocyanine, dye, condensed polycyclic, nitro, and nitroso (brilliant carmine 6B, lake red C, watching red, disazo yellow, hanza yellow, phthalocyanine blue, Phthalocyanine green, alkali blue, aniline black, etc.); metals such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese, nickel, metal oxides and sulfides, and ocher, ultramarine, bitumen, etc. Carbon blacks such as inorganic pigments, furnace carbon black, lamp black, acetylene black and channel black can be used. Examples of the dye include a basic dye, an acid dye, a direct dye, a soluble vat dye, an acid mordant dye, a mordant dye, a reactive dye, a vat dye, a sulfur dye, and the like. Water-soluble dyes can be used. Either or both of a pigment and a dye may be used as a colorant. However, the use of a pigment is preferable because an ink with less bleeding and show-through and excellent weather resistance can be obtained.

  The content of the colorant in the ink is usually 1 to 20% by weight, and preferably 3 to 15% by weight. In order to further increase the printing density of the printed material, it is more preferable to contain 5% by weight or more.

（式中、Ｒ^１，Ｒ^２，Ｒ^３はそれぞれ独立にＨ、ＣＨ_３、（ＣＨ_２）ｎＣＯＯＨ（ｎは０または１の整数）を表す。） The ink preferably contains a spinnability imparting agent capable of imparting appropriate spinnability to the ink. Among these, since the spinnability of the ink can be controlled appropriately, the linear structure type unsaturated carboxylic acid water-soluble polymer, the polyalkylene oxide having a molecular weight of 50,000 or more, and the linear structure type (meta ) Any one or more of acrylamide-based water-soluble polymers can be preferably used. Here, in this specification, acrylic acid or methacrylic acid is collectively referred to as “(meth) acrylic acid”, and (meth) acrylamide means acrylamide and methacrylamide.
Examples of the linear structure type unsaturated carboxylic acid-based water-soluble polymer include a repeating unit represented by the following general formula (1), which is a non-branched cross-linked linear structure type unsaturated carboxylic acid-based water-soluble polymer. Molecules are preferred.

(In the formula, R ¹ , R ² and R ³ each independently represent H, CH ₃ , (CH ₂ ) nCOOH (n is an integer of 0 or 1).)

Here, when two or more carboxyl groups are contained, they may form an acid anhydride. In the case of a copolymer, the copolymerization form may be any form such as a random type, an alternating type, or a block type.
Examples of the unsaturated carboxylic acid-based water-soluble polymer include one or more unsaturated carboxylic acids selected from the group consisting of (meth) acrylic acid, maleic anhydride, maleic acid, fumaric acid, crotonic acid, and itaconic acid. Are included in the main chain, and salts thereof are also included. When this unsaturated carboxylic acid-based water-soluble polymer is dissolved in water, it becomes a super multivalent ionic polymer having a number of negative charges. Due to the steric entanglement brought about by this strong ionic atmosphere and the structure of a linear polymer. It is considered that a spinnability imparting effect is produced.

More specifically, poly (meth) acrylic acid, acrylic acid-methacrylic acid copolymer, (meth) acrylic acid-maleic acid copolymer, (meth) acrylic acid-sulfonic acid monomer copolymer, (meth ) Acrylic acid-itaconic acid copolymer, (meth) acrylic acid ester-maleic acid copolymer, (meth) acrylic acid- (meth) acrylamide copolymer, (meth) acrylic acid- (meth) acrylic acid ester co Examples include polymers, (meth) acrylic acid-vinyl pyrrolidone copolymers, polymaleic acid, polyfumaric acid, polycrotonic acid, polyitaconic acid, maleic anhydride-alkyl vinyl ether copolymers, and salts thereof.
The salt is preferably a monovalent metal salt or an amine salt. For example, if it is poly (meth) acrylic acid, the salt may be sodium poly (meth) acrylate, potassium poly (meth) acrylate, poly (meth). Examples include ammonium acrylate, poly (meth) acrylic acid triethanolamine, and the like. Other preferred examples include sodium polyitaconate, sodium polymaleate, acrylic acid-methacrylic acid copolymer sodium, acrylic acid-maleic acid copolymer sodium, acrylic acid-acrylamide copolymer sodium, and the like.

  When these unsaturated carboxylic acid-based water-soluble polymers are of an unneutralized type, usually, in the ink, these water-soluble polymers are mixed with sodium hydroxide, potassium hydroxide, ammonia water, triethanolamine. An alkaline neutralizing agent such as diisopropanolamine is added. When a neutralized salt of an unsaturated carboxylic acid-based water-soluble polymer is used, it is not necessary to add these alkaline neutralizers.

If the unsaturated carboxylic acid-based water-soluble polymer is of a linear structure type, when compared among compounds of the same molecular structure, it is possible to increase the ink thread length as the weight average molecular weight increases. The smaller the content in the ink, the lower the ink viscosity.
Among the above unsaturated carboxylic acid-based water-soluble polymers, it is possible to increase the string length without increasing the viscosity of the ink, so unsaturated carboxylic acid monomers (acrylic acid, methacrylic acid, crotonic acid, Polymers (homopolymers or copolymers) composed only of itaconic acid, maleic acid, maleic anhydride, fumaric acid) and salts of these polymers are preferably used, and polyacrylic acid and salts thereof are particularly preferred Used.

  The unsaturated carboxylic acid-based water-soluble polymer including polyacrylic acid and its salt preferably has a weight average molecular weight of 10,000 or more, more preferably 100,000 or more, even more preferably 600,000 or more, 120 Those of 10,000 or more are particularly preferably used. If the molecular weight is less than 10,000, it is necessary to contain a large amount of unsaturated carboxylic acid-based water-soluble polymer in order to increase the thread length of the ink, and as a result, it becomes difficult to make the ink low viscosity. . The molecular weight is preferably 10 million or less, more preferably 6 million or less. If the molecular weight exceeds 10 million, it is possible to increase the thread length of the ink with a small amount of content, but in order to obtain a thread length that is not too large, the content needs to be very small and stable. It is difficult to obtain the obtained ink physical properties.

As the alkylene group of the polyalkylene oxide, an ethylene group, a propylene group, a butylene group, or the like is preferably used. It may contain a single alkylene group or may contain multiple types of alkylene groups. Specifically, polyethylene oxide and ethylene oxide-propylene oxide copolymer can be preferably used, and polyethylene oxide is particularly preferably used. In the case of an ethylene oxide-propylene oxide copolymer, the polymerization ratio (molar ratio) of ethylene oxide is preferably 0.5 or more, and more preferably 0.8 or more.
The molecular weight (weight average molecular weight) of the polyalkylene oxide is 50,000 or more in order to obtain the effect of controlling the transfer amount of the low viscosity ink, preferably 300,000 or more, and preferably 1,000,000 or more. More preferably. On the other hand, the upper limit of the molecular weight is not particularly limited, but is preferably 10 million or less, and is preferably about 8 million or less from the viewpoint of easy adjustment of the blending amount.
Polyalkylene oxide is a polymer having a linear structure, and when dissolved in water, the degree of freedom of the intramolecular bond angle provided by the molecular structure, the steric entanglement provided by the structure of the linear polymer, It exhibits unique behavior in water due to its affinity with water molecules brought about by the polarity of oxygen atoms.

The “linear structure type” of the linear structure type (meth) acrylamide water-soluble polymer means a single chain structure having no branched chain (branching), a crosslinked structure or a cyclic structure. .
This includes (meth) acrylamide homopolymers as well as copolymers containing (meth) acrylamide in the main chain. In this case, the comonomer is unsaturated such as acrylic acid or methacrylic acid (hereinafter referred to as “(meth) acrylic acid”), maleic anhydride, maleic acid, fumaric acid, crotonic acid, itaconic acid, etc. Derivatives such as carboxylic acids and salts thereof; unsaturated sulfonic acids such as (meth) acrylamide alkyl sulfonic acids and salts thereof; and the like. As the salt, monovalent metal salts such as lithium, sodium and potassium; ammonium salts; amine salts such as monoethanolamine, dipropanolamine and triethanolamine are preferable. In the case of a copolymer, the polymerization ratio (molar ratio) of (meth) acrylamide is preferably 0.5 or more, and more preferably 0.8 or more.

The molecular weight (weight average molecular weight) of the linear structure type (meth) acrylamide water-soluble polymer is preferably 50,000 or more, preferably 300,000 or more in order to obtain the effect of controlling the transfer amount of the low-viscosity ink. More preferably, it is more preferably 1 million or more. On the other hand, the upper limit value of the molecular weight is not particularly limited, but is preferably 30 million or less, and is preferably about 15 million or less from the viewpoint of easy adjustment of the blending amount.
A linear structure type (meth) acrylamide water-soluble polymer is a polymer having a linear structure, and when dissolved in water, the degree of freedom of the intramolecular bond angle provided by the molecular structure is high. It exhibits unique behavior in water due to the three-dimensional entanglement brought about by the structure of molecules.

The content of the spinnability imparting agent as described above varies depending on the type, but is usually preferably 0.01 to 5% by weight, and 0.03 to 2% by weight based on the total amount of the ink. More preferably, the content is 0.03 to 0.5% by weight, still more preferably 0.05 to 0.2% by weight.
If the blending amount of the spinnability imparting agent is too large, the ink tends to have a high viscosity, and the dryness of the printed matter may deteriorate.
Since the ink string length may increase or decrease under the influence of other ink components, it is preferable to appropriately adjust the type and content of the spinnability imparting agent in consideration of the influence of other ink components.

It is preferable to add a water-soluble organic solvent to the ink from the viewpoints of preventing drying at the perforated portion of the stencil sheet during printing and adjusting the surface tension of the ink.
As the water-soluble organic solvent, an organic compound that is liquid at room temperature and is soluble in water is used. For example, lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, 2-methyl-2-propanol; ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, penta Glycols such as ethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol; glycerin; acetins (monoacetin, diacetin, triacetin); triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, Triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene Glycol monoethyl ether, tetraethylene glycol dimethyl ether, derivatives of glycols such as tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, beta-thiodiglycol, may be used sulfolane. Polyethylene glycol having an average molecular weight of 200, 300, 400, 600 or the like in the range of 190 to 630, diol type polypropylene glycol having an average molecular weight of 400 or the like in the range of 200 to 600, average molecular weight of 300, 700, or the like A low molecular weight polyalkylene glycol such as a triol type polypropylene glycol having an average molecular weight of 250 to 800 can also be used. These water-soluble organic solvents can be used alone or in combination of two or more.

  The content of the water-soluble organic solvent in the ink is preferably 5% by weight or more, and more preferably 10% by weight or more as the total content when two or more kinds are used. The upper limit of the content is not particularly limited, but is preferably about 45% by weight or less, and more preferably about 35% by weight or less in order to reduce back-through of the image. By containing 5% by weight or more of a water-soluble organic solvent having a boiling point higher than that of water, more preferably having a boiling point of 150 ° C. or higher, drying of the stencil sheet punched portion during printing can be effectively prevented.

An arbitrary thickener can be mix | blended with ink as a viscosity modifier, For example, 1 or more types of a water-soluble polymer type | system | group thickener and a clay mineral type | system | group thickener can be used.
As the water-soluble polymer thickener, natural polymers, semi-synthetic polymers, and synthetic polymers can be used.
Examples of natural polymers include plant-based natural polymers such as gum arabic, carrageenan, guar gum, locust bean gum, pectin, tragacanth gum, corn starch, konjac mannan and agar; microbial natural polymers such as pullulan, xanthan gum and dextrin; Animal-based natural polymers such as gelatin, casein, and glue can be used.
Examples of semi-synthetic polymers include cellulose-based semi-synthetic polymers such as ethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and hydroxypropyl methyl cellulose; starch-based compounds such as hydroxyethyl starch, sodium carboxymethyl starch, and cyclodextrin Semi-synthetic polymers; Alginate-based semi-synthetic polymers such as sodium alginate and propylene glycol alginate; sodium hyaluronate can be used.
Synthetic polymers include, for example, polyacrylic acid, polymethacrylic acid, polycrotonic acid, polyitaconic acid, polymaleic acid, polyfumaric acid, acrylic acid-methacrylic acid copolymer, acrylic acid-itaconic acid copolymer, acrylic acid-maleic acid. Acid copolymer, acrylic acid-acrylamide copolymer, acrylic acid-acrylic acid ester copolymer, acrylic acid-methacrylic acid ester copolymer, acrylic acid-sulfonic acid monomer copolymer, acrylic acid-vinylpyrrolidone copolymer Polymers, unsaturated carboxylic acid synthetic polymers such as maleic anhydride-alkyl vinyl ether copolymers; vinyl synthetic polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, poly N-vinylacetamide, polyacrylamide; polyethylene oxide, Li ethyleneimine, could be used a polyurethane.

Among these thickeners, unsaturated carboxylic acid-based water-soluble polymer thickeners, which are electrolyte-type thickeners having a large number of dissociating groups in the side chain, can provide the desired thickening effect even in a small amount. For this reason, it is preferably used. Here, the unsaturated carboxylic acid-based synthetic polymer is selected from the group consisting of, for example, acrylic acid, methacrylic acid, maleic anhydride, maleic acid, fumaric acid, crotonic acid, and itaconic acid as illustrated above. Examples thereof include water-soluble polymers containing at least one kind of unsaturated carboxylic acid in the main chain, and include not only the above-described unneutralized type but also neutralized salts thereof. Examples of the neutralized salt include alkali metal salts such as sodium and potassium, ammonium salts, and alkanolamine salts such as triethanolamine. Specific examples include sodium polyacrylate, potassium polyacrylate, and polyacrylic acid. Ammonium, polyethanolic triethanolamine, polysodium methacrylate, polyammonium methacrylate, sodium polyitaconate, sodium polymaleate, sodium acrylic acid-methacrylic acid copolymer, sodium acrylic acid-maleic acid copolymer, etc. are preferably used. be able to.
As the clay mineral-based thickener, for example, smectite-based clay minerals such as montmorillonite, hectorite, and saponite can be used.
In addition to the ink thickener, the water-soluble polymer exemplified as the thickener can be used as a colorant fixing agent for printing paper, etc., depending on the type and amount thereof. Moreover, when using a pigment as a coloring agent, it can also be used as a pigment dispersant.

In addition to the above components, the ink can optionally contain a pigment dispersant, a fixing agent, an antifoaming agent, a surface tension reducing agent, a pH adjusting agent, an antioxidant, a preservative, and the like.
An alkali-soluble resin can be contained in the ink and used as a fixing agent for a colorant on a printing medium such as printing paper. When a pigment is used as the colorant, an alkali-soluble resin can also be used as the pigment dispersant. The alkali-soluble resin means a polymer that is insoluble in water but becomes water-soluble in the presence of alkali. Therefore, even if the compound name is the same, for example, acrylic acid-acrylic acid ester copolymer, in the present invention, it is classified into a water-soluble polymer or an alkali-soluble resin depending on its solubility.

Examples of the alkali-soluble resin include styrene- (meth) acrylic acid copolymer, styrene-α methylstyrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid ester- (meth) acrylic acid copolymer. Styrene-maleic anhydride copolymer, vinylnaphthalene- (meth) acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, isobutylene-maleic anhydride copolymer, (meth) acrylic acid ester- (meta ) Acrylic acid copolymer, acrylic acid ester-methacrylic acid ester- (meth) acrylic acid copolymer can be used. These can be used alone or in combination of two or more. These alkali-soluble resins can be used by neutralizing with any alkali such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkanolamines such as aqueous ammonia and triethanolamine, and making them water-soluble. it can.
The alkali-soluble resin is preferably contained in an amount of 5% by weight or less in terms of solid content in the ink because there is a risk that the printing performance after non-use of the printing press may be hindered when the alkali-soluble resin is contained in a large amount. Is 3% by weight or less.

The ink can contain an oil-in-water (O / W) type resin emulsion and can be used as a fixing agent for a colorant on a printing medium such as printing paper. In the case where a pigment is used as the colorant, this resin emulsion can also be used as a pigment dispersant.
Examples of the oil-in-water (O / W) resin emulsion include polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic ester copolymer, polyacrylic ester, polymethacrylic ester, polystyrene, and styrene. -Resin emulsions such as acrylic ester copolymer, styrene-butadiene copolymer, vinylidene chloride-acrylic ester copolymer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyurethane and the like can be used. Two or more of these may be used in combination.
The resin emulsion may be included in the ink in a range of 5% by weight or less in terms of solid content, more preferably, since there is a possibility that the printing performance after the non-use of the printing press may be hindered when the resin emulsion is contained in a large amount. 2% by weight or less.

In order to improve the image quality of the printed matter, extender pigments can be included in the ink.
As the extender pigment, for example, white clay, talc, clay, diatomaceous earth, calcium carbonate, barium carbonate, barium sulfate, alumina white, silica, kaolin, mica, aluminum hydroxide can be used, and two or more of these can be used in combination. May be.
If the extender pigment is contained in a large amount, it may hinder the fixing of the colorant to the printing material or may impair the printing performance after the printer is not used. More preferably, it is 2 wt% or less.

Further, as a pigment dispersant, an antifoaming agent, a surface tension reducing agent, etc., an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or a polymer-based, silicone-based, fluorine-based interface An activator can be included in the ink.
In order to adjust the viscosity and pH of the ink, an electrolyte can be added to the ink. Examples of the electrolyte include sodium sulfate, potassium hydrogen phosphate, sodium citrate, potassium tartrate, and sodium borate, and two or more kinds may be used in combination. Sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonium hydroxide, triethanolamine, and the like can also be used as an ink thickening aid or pH adjuster.

By blending an antioxidant, the ink components can be prevented from being oxidized and the storage stability of the ink can be improved. As the antioxidant, for example, L-ascorbic acid, sodium L-ascorbate, sodium isoascorbate, potassium sulfite, sodium sulfite, sodium thiosulfate, sodium dithionite, sodium pyrosulfite can be used.
By blending a preservative, the ink can be prevented from being spoiled and the storage stability can be improved. Examples of preservatives include 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 1 Isothiazolone preservatives such as 1,2-benzisothiazolin-3-one; triazine preservatives such as hexahydro-1,3,5-tris (2-hydroxyethyl) -s-triazine; 2-pyridinethiol sodium-1- Pyridine / quinoline preservatives such as oxide and 8-oxyquinoline; Dithiocarbamate preservatives such as sodium dimethyldithiocarbamate; 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitro-1,3 -Propanediol, 2,2-dibromo-2-nitroethanol, 1,2-dibromo-2,4-dicia Brominated organic preservatives such as butane; p-hydroxybenzoate, p- hydroxybenzoate ethyl, potassium sorbate, sodium dehydroacetate, can be used salicylic acid.

  The ink according to the present invention can be produced by mixing each compounding component, and details thereof are not particularly limited. For example, a part of water, a pigment and a pigment dispersant are mixed, and the pigment is dispersed using a dispersing means such as a ball mill or a bead mill, while the remaining water, the spinnability imparting agent and the water-soluble organic solvent are mixed. May be mixed, and both may be mixed.

In the stencil printing using the above ink, it is preferable to use a digital stencil printing machine from the viewpoint of excellent operability. In particular, the ink according to the invention of the present inventors can be used even if the printing machine is left in a non-use state. It is preferable to use a novel stencil printing apparatus (Japanese Patent Application Laid-Open No. 2004-122712, Japanese Patent Application Laid-Open No. 2005-53209) in which the component structure and physical properties do not change.
This stencil printing apparatus is rotatable and has a drum on which a stencil sheet is mounted on the outer peripheral wall surface, an ink supply means for supplying ink from the upstream side of the maximum printing area of the outer peripheral wall of the drum, and a paper feed. And a press roll that presses the printed medium against the outer peripheral wall (hereinafter also referred to as “RK device”).
The stencil printing method according to the present invention is performed using the ink according to the present invention and the RK apparatus, and is made by pressing with a press roll while rotating a drum equipped with a stencil sheet that has been subjected to plate making. Ink is passed through the perforated portion of the stencil sheet and transferred to the printing medium.

  In the RK apparatus, when the outer peripheral wall of the drum is rotated and the surface of the outer peripheral wall is supplied with ink from the ink supply unit and the printing medium is fed, the printing medium is stenciled by a press roll. While being pressed against the base paper and the outer peripheral wall of the drum, the ink between the outer peripheral wall of the drum and the stencil paper is diffused downstream in the printing direction by the pressing force of the press roll, and is also diffused. The ink oozed out from the perforations of the stencil sheet and transferred to the printing medium side, and an ink image was printed on the printing medium. That is, the ink is supplied by squeezing between the drum surface and the stencil sheet with a press roll. The ink supplied to the drum is held in a substantially sealed space between the outer peripheral wall of the drum and the stencil sheet, and contact with the atmosphere is minimized. Therefore, evaporation of moisture in the ink and alteration of the ink in the stencil printing apparatus are prevented, and as a result, it is possible to provide a high-quality printed material that has excellent drying properties and does not rub the image even when handled immediately after printing. it can. In addition, after leaving the printing press for a long period of time, printing can be resumed without the need for cleaning or other work. From the initial printed matter after non-use, it is equivalent to the printed matter before leaving. Printing performance can be obtained.

Therefore, for example, even when a high water content water-based ink is used as the ink of the present invention, in the stencil printing apparatus, the ink inside the printing press is sealed to prevent moisture from evaporating into the atmosphere. The same effect can be obtained.
Furthermore, in this apparatus, it is not necessary to set the viscosity of the ink to be high to some extent for matching with a printing machine such as preventing ink leakage from the printing machine as in the prior art. On the contrary, in the RK apparatus, since the ink is supplied to the surface of the drum outer peripheral wall from the ink supply unit provided upstream of the drum outer peripheral wall in the printing mode as described above, In contrast, an ink having a low viscosity is preferably used.
Therefore, if the viscosity of the ink is high, it is necessary to set a high pressing force by the press roll. If this is too high, there is a risk that the amount of ink transfer will increase or the image will expand and contract due to the elongation of the stencil paper. However, when using a low-viscosity ink as the ink of the present invention, such a problem does not occur, the ink supply in the stencil printing apparatus is optimal, and there is no image chipping at the edge of the printing surface, And the penetration speed of the ink to a printing medium can be improved, and the drying property of printed matter can be improved easily.

A preferred embodiment of the stencil printing apparatus will be described below with reference to the drawings.
1 to 7 show a first embodiment, FIG. 1 is a schematic configuration diagram of a stencil printing apparatus, FIG. 2 is a perspective view of a drum, FIG. 3 is a cross-sectional view taken along the line A1-A1 in FIG. 2 is a cross-sectional view taken along the line B1-B1 in FIG. 2, FIG. 5 is a plan view of the drum showing the ink supply unit, FIG. 6 is a cross-sectional view taken along the line C1-C1 in FIG. It is a fragmentary sectional view.
The stencil printing apparatus shown in this embodiment has an outer peripheral wall that is rotatable and formed of an ink-impermeable member, a drum on which a stencil sheet is mounted on the surface of the outer peripheral wall, and the drum An ink supply unit is provided upstream of the maximum printing area of the outer peripheral wall, and an ink supply unit that supplies ink to the surface of the outer peripheral wall from the ink supply unit, and presses the fed print medium against the outer peripheral wall. Press roll.

1 is a schematic configuration diagram of a stencil printing apparatus, FIG. 2 is a perspective view of a drum, FIG. 3 is a sectional view taken along line A1-A1 in FIG. 2, and FIG. 4 is a sectional view taken along line B1-B1 in FIG. 5 is a plan view of the drum showing the ink supply unit, FIG. 6 is a sectional view taken along line C1-C1 in FIG. 5, and FIG. 7 is a partial sectional view for explaining the ink diffusion mechanism.
As shown in FIG. 1, the stencil printing apparatus mainly includes a document reading unit 1, a plate making unit 2, a printing unit 3, a paper feeding unit 4, a paper discharging unit 5 and a plate discharging unit 6. .

  The document reading unit 1 includes a document setting table 10 on which a document to be printed is placed, reflection-type document sensors 11 and 12 that detect the presence of documents on the document setting table 10, and documents on the document setting table 10. The document transport rolls 13 and 14 to be transported, the stepping motor 15 that rotationally drives the document transport rolls 13 and 14, and the image data of the document transported by the document transport rolls 13 and 14 are optically read and this is converted into an electrical signal. A contact type image sensor 16 for conversion and a document discharge tray 17 for placing a document discharged from the document setting table 10 are provided. Then, the document placed on the document setting table 10 is transported by the document transport rollers 13 and 14, and the image sensor 16 reads the image data of the transported document.

The plate making unit 2 includes a base paper storage unit 19 that stores the rolled long stencil base paper 18, a thermal head 20 that is disposed downstream of the base paper storage unit 19, and a position opposite to the thermal head 20. The platen roll 21, a pair of base paper feed rolls 22, 22 disposed downstream of the transport of the platen roll 21 and the thermal head 20, a light pulse motor 23 that rotationally drives the platen roll 21 and the base paper feed roll 22, And a base paper cutter 24 disposed downstream of the pair of base paper feed rolls 22 and 22.
Then, the long stencil sheet 18 is transported by the rotation of the platen roll 21 and the base paper feed roll 22, and each point-like heating element of the thermal head 20 selectively generates heat based on the image data read by the image sensor 16. Thus, the stencil sheet 18 is thermally perforated to make a stencil, and the stencil sheet 18 thus made is cut by a stencil sheet cutter 24 to produce a stencil sheet 18 having a predetermined length.

  The printing unit 3 includes a drum 26 that rotates in the direction of arrow A in FIG. 1 by the driving force of the main motor 25, a base paper clamp unit 27 that is provided on the outer peripheral surface of the drum 26 and clamps the leading end of the stencil base paper 18, and a drum A stencil sheet 18 is wound around the outer peripheral surface of the stencil sheet 26, a stencil sheet check sensor 28 for detecting whether or not the stencil sheet 18 is mounted, a reference position detection sensor 30 for detecting the reference position of the drum 26, and a rotary encoder for detecting the rotation of the main motor 25. 31. The rotational position of the drum 26 can be detected by detecting the output pulse of the rotary encoder 31 based on the detection output of the reference position detection sensor 30.

The printing unit 3 includes a press roll 35 disposed below the drum 26. The press roll 35 is pressed against the outer peripheral surface of the drum 26 by the driving force of the solenoid device 36. It is configured to be able to change between a standby position separated from the outer peripheral surface. The press roll 35 is always positioned at the pressing position during the printing mode period (including trial printing), and is positioned at the standby position during the period other than the printing mode.
Then, the leading end of the stencil sheet 18 conveyed from the plate making unit 2 is clamped by the stencil sheet clamp unit 27, and the drum 26 is rotated in this clamped state so that the stencil sheet 18 is wound around the outer peripheral surface of the drum 26. The printing paper (printing medium) 37 fed from the paper feeding unit 4 in synchronism with the rotation of the paper is pressed against the stencil paper 18 wound around the drum 26 by the press roll 35, whereby the stencil paper 18 is applied to the printing paper 37. The ink 56 is transferred from the perforations and the image is printed.

The paper feed unit 4 includes a paper feed tray 38 on which the print paper 37 is stacked, primary paper feed rolls 39 and 40 that transport only the uppermost print paper 37 from the paper feed base 38, and the primary paper feed. A pair of secondary paper feed rolls 41 and 41 for conveying the printing paper 37 conveyed by the rolls 39 and 40 between the drum 26 and the press roll 35 in synchronization with the rotation of the drum 26, and the pair of secondary paper feed rolls A paper feed sensor 42 that detects whether or not the printing paper 37 has been conveyed between 41 and 41. The primary feed rolls 39 and 40 are configured to selectively transmit the rotation of the main motor 25 via the feed clutch 43.
The paper discharge unit 5 includes a paper separation claw 44 that separates the printed printing paper 37 from the drum 26, a conveyance path 45 through which the printing paper 37 separated from the drum 26 by the paper separation claw 44 is conveyed, And a paper discharge tray 46 on which the printing paper 37 discharged from the conveyance path 45 is placed.

  The plate discharging unit 6 guides the leading end of the stencil sheet 18 unclamped from the outer peripheral surface of the drum 26 and transports the guided used stencil sheet 18 while being peeled off from the drum 26, and this plate discharging transport. A stencil box 48 for storing the stencil sheet 18 conveyed by the means 47 and a stencil compression member 49 for pushing the stencil sheet 18 conveyed into the stencil box 48 by the stencil conveying means 47 into the stencil box 48 are provided. Have.

  As shown in FIGS. 2 to 4, the drum 26 includes a pair of support shafts 50 fixed to the apparatus main body H (shown in FIG. 1) and a pair of shafts 50 rotatably supported by the support shafts 50 through respective bearings 51. Side discs 52 and 52, and a cylindrical outer peripheral wall 53 fixed between the pair of side discs 52 and 52. The outer peripheral wall 53 is integrally driven with the pair of side disks 52 and 52 by the rotational force of the main motor 25. The outer peripheral wall 53 is formed of an ink impermeable member that has rigidity and does not allow the ink 56 to pass therethrough. Depending on the type of the ink impermeable member, for the purpose of forming the outer peripheral surface of the outer peripheral wall 53 into a cylindrical surface without irregularities, fluororesin processing such as Teflon (registered trademark) processing, nickel plating, nickel chrome plating, Various known surface processing treatments such as hot dip galvanization and anodizing treatment may be applied to the outer peripheral wall 53.

  The base paper clamp portion 27 is provided by using a clamp recess 53 a formed along the axial direction of the support shaft 50 of the outer peripheral wall 53. One end of the base paper clamp portion 27 is rotatably supported by the outer peripheral wall 53 and protrudes from the outer peripheral wall 53 in the clamp release state indicated by the phantom line in FIG. 4, but in the clamped state indicated by the solid line in FIG. 53 so as not to protrude from 53. Therefore, the stencil sheet clamping unit 27 can clamp the stencil sheet 18 without protruding onto the outer peripheral wall 53.

  The outer peripheral wall 53 is rotated in the direction of arrow A in FIGS. 2 and 4, and the position where the outer peripheral wall 53 is slightly rotated from the base paper clamp portion 27 is the printing start point. Therefore, the rotation direction A becomes the printing direction M, and the area below the printing start point is the printing area. In this embodiment, the maximum print area is set to an area where A3 size printing is possible. An ink supply unit 55 </ b> A of the ink supply means 54 is provided upstream of the maximum print area of the outer peripheral wall 53 in the printing direction M.

  As shown in FIGS. 2 to 6, the ink supply means 54 is sucked by an ink container 57 in which ink 56 is stored, an ink pump 58 that sucks the ink 56 in the ink container 57, and the ink pump 58. A first pipe 59 for supplying the ink 56, and a support shaft 50 to which the other end of the first pipe 59 is connected, an ink passage 60 is formed therein, and a hole 61 is formed at a position opposed to 180 degrees. A rotary joint 63 that is rotatably supported on the outer peripheral side of the support shaft 50 and has a communication hole 62 that can communicate with the hole 61, one end connected to the rotary joint 63, and the other end connected to the outer peripheral wall 53. The second pipe 64 is guided and an ink supply part 55A having the other end of the second pipe 64 opened.

The ink supply unit 55A includes an ink diffusion groove 65 that diffuses the ink 56 from the second pipe 64 in the printing orthogonal direction N, and a plurality of communication holes that are opened at intervals in the printing orthogonal direction N of the ink diffusion groove 65. 66 and an ink supply port 55a serving as an ink diffusion supply unit that communicates with the plurality of communication holes 66 and opens on the surface of the outer peripheral wall 53.
As shown in FIGS. 5 and 6, the ink diffusion groove 65, the plurality of communication holes 66, and the ink supply port 55 a are formed along the direction orthogonal to the printing direction M of the outer peripheral wall 53 (that is, the printing orthogonal direction N). The ink supply recess 67 and the ink distribution member 68 disposed therein are formed. The ink supply ports 55 a are formed along the printing orthogonal direction N, and supply the ink 56 almost uniformly in the printing orthogonal direction N of the outer peripheral wall 53.

Next, the operation of the stencil printing apparatus having the above configuration will be briefly described.
First, when the plate making mode is selected, the plate making unit 2 transports the stencil sheet 18 by the rotation of the platen roll 21 and the base paper feed roll 22, and a number of thermal heads 20 are based on the image data read by the document reading unit 1. When the heating element selectively generates heat, the stencil sheet 18 is thermally perforated to make a plate, and a predetermined portion of the stencil sheet 18 is cut with a stencil cutter 24 to make a stencil sheet 18 having a desired size.

In the printing unit 3, the tip of the stencil sheet 18 made by the plate making unit 2 is clamped by the stencil sheet clamping unit 27 of the drum 26, and in this clamped state, the drum 26 is rotated to place the stencil sheet 18 on the outer peripheral surface of the drum 26. Wrap and plate.
Next, when the printing mode is selected, the drum 26 is rotationally driven in the printing unit 3 and the driving of the ink supply means 54 is started. Then, the ink 56 is supplied to the outer peripheral wall 53 from the ink supply port 55a, and the supplied ink 56 is held between the outer peripheral wall 53 and the stencil sheet 18, and the press roll 35 is displaced from the standby position to the pressing position. Is done.

  In synchronization with the rotation of the drum 26, the paper feeding unit 4 feeds the printing paper 37 between the drum 26 and the press roll 35. The fed printing paper 37 is pressed against the outer peripheral wall 53 of the drum 26 by the press roll 35 and is conveyed by the rotation of the outer peripheral wall 53 of the drum 26. That is, the printing paper 37 is conveyed while being in close contact with the stencil sheet 18.

  In parallel with the conveyance of the printing paper 37, the ink 56 held between the outer peripheral wall 53 of the drum 26 and the stencil sheet 18 is squeezed by the pressing force of the press roll 35 as shown in FIG. While being diffused downstream in the printing direction M, the diffused ink 56 oozes out from the perforations of the stencil sheet 18 and is transferred to the printing paper 37 side. As described above, an ink image is printed on the printing paper 37 while passing between the outer peripheral wall 53 of the drum 26 and the press roll 35. The printing paper 37 that has passed through between the outer peripheral wall 53 of the drum 26 and the press roll 35 is peeled off from the drum 26 by the paper separation claw 44, and the printing paper 37 that is separated from the drum 26 passes through the conveyance path 45. Then, the paper is discharged onto a paper discharge tray 46 and stacked there.

When printing of the set number of prints is completed, the rotation of the outer peripheral wall 53 of the drum 26 is stopped and the drive of the ink supply means 54 is stopped. Thereby, the supply of the ink 56 to the outer peripheral wall 53 is stopped. Further, the press roll 35 is returned from the pressing position to the standby position and enters the standby mode.
When the plate discharging mode is selected by starting a new plate making or the like, the base paper clamp part 27 of the drum 26 is displaced to the clamp release position, and the leading end side of the stencil paper 18 that has been released from the clamp is transported by the drum 26 as the drum 26 rotates. It is guided by the means 47 and is stored in the discharge box 48.

  As described above, in this stencil printing apparatus, the ink 56 is supplied to the outer peripheral wall 53 of the drum 26, and the ink 56 is diffused on the outer peripheral wall 53 by being squeezed by the pressing force of the press roll 35. The ink 56 is transferred to the printing paper 37 by punching the stencil sheet 18 by the pressing force of the press roll 35. Therefore, when the printing mode is completed, the ink 56 supplied to the drum 26 is held in a substantially sealed space between the outer peripheral wall 53 of the drum 26 and the stencil sheet 18, and contact with the atmosphere is minimized. . Thereby, even if it does not perform printing for a long time, the ink 56 does not change in quality, and the quality change of the ink 56 can be prevented reliably. Further, it is not necessary to arrange various rolls for supplying ink inside the drum 26 as in the conventional example. Thereby, the drum 26 can be further reduced in size and weight.

Further, since the outer peripheral wall 53 of the drum 26 may be formed of an ink impermeable member, variations in material selection are widened, and a simple structure may be used, so that it can be manufactured at low cost. Further, since the strength of the drum 26 can be easily increased, image unevenness due to fluctuations in printing pressure or the like can be prevented.
Furthermore, the ink 56 is basically subjected to printing in the best state with almost no deterioration because contact with the atmosphere is minimized. Further, since it is not necessary to manage the deterioration prevention of the ink 56, the degree of freedom in selecting the ink 56 can be expanded.

  As another stencil printing apparatus, for example, it has a peripheral wall on which a stencil sheet is mounted, and the outer peripheral wall does not pass ink, and the surface of at least the maximum printing area of the base wall. A drum provided with an ink passage between the porous member and the base wall at least over the entire maximum printing area, and ink in the ink passage. It is also possible to use a stencil printing apparatus provided with an ink supply means for supplying, an ink recovery means for recovering ink in the ink passage, and a press roll for pressing a fed printing medium against the outer peripheral wall.

  The stencil sheet used in the present invention can be produced by a conventionally known method. Specifically, a method of laminating a porous support and a thermoplastic resin film with an adhesive disclosed in JP-A-11-309954; an adhesive disclosed in JP-A-2001-10247 A method of thermally bonding a porous support and a thermoplastic resin film without using an agent; forming a porous resin film on one surface of a thermoplastic resin film as disclosed in JP-A-10-147075 And a method of laminating a porous fiber film on the surface; a method of forming a porous resin film on a porous support disclosed in JP-A-2003-165282; and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Hereinafter, “% by weight” is simply referred to as “%”.

Example 1
While stirring 29.97% of distilled water, 0.03% of a linear structure type sodium polyacrylate (Nippon Pure Chemicals Co., Ltd. “Aronbis S”: molecular weight 4 million to 5 million) as a spinnability-imparting agent. Was added and dissolved.
20.0% of glycerin was added to 30% of the obtained aqueous sodium polyacrylate solution while stirring. 50% of the obtained solution was stirred and added to 50% of a self-dispersing carbon black dispersion (“Bonjet Black CW-1” manufactured by Orient Chemical Co., Ltd.) (pigment content 20%). The ink of Example 1 was obtained.

(Examples 2 to 10, Comparative Examples 1 to 4)
Inks of Examples 2 to 8 and Comparative Examples 1 to 4 were obtained in the same manner as Example 1 except that the formulation shown in Table 1 was used.
In Examples 9 and 10, carbon black (“# 40” manufactured by Mitsubishi Chemical Corporation) was used as a colorant as shown in Table 1, and carbon black, a dispersant shown in Table 1 and 38% distilled water were mixed in advance. The pigment dispersion was prepared by sufficiently dispersing with a bead mill. Thereafter, ink was produced in the same manner as in Example 1.
In the table, polyvinylpyrrolidone is “K17” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sodium naphthalene sulfonate formalin condensate is “Demol N” manufactured by Kao Corporation, and polyethylene glycol is “polyethylene glycol manufactured by Wako Pure Chemical Industries, Ltd. “200”, CMC (carboxymethylcellulose) sodium is manufactured by Kanto Chemical Co., Ltd., and smectite is “Lucentite SWN90” manufactured by Corp Chemical Co., Ltd.

  The string length of each ink obtained was measured using a measuring instrument whose outline is schematically shown in FIG. That is, under an ambient temperature of 23 ° C., the container 201 is filled with ink, and the entire chrome steel ball 202 (diameter 15 mm) is immersed therein so that the upper part of the sphere coincides with the line of the ink level. Then, the state when the chrome steel ball was pulled vertically at a speed of 150 mm per second was photographed from the front using a photographing machine (3CCD color video camera module XC-003 manufactured by Sony Corporation) (not shown). The maximum length of the ink fountain immediately before the ink fountain formed between the ink liquid surface and the steel ball was broken (distance between the ink liquid surface and the lower part of the steel ball) was read from the recorded image.

The surface tension of the ink was measured at 25 ° C. using a CBVP-Z surface tension meter manufactured by Kyowa Interface Science Co., Ltd.
The viscosity of the ink was measured using a stress-controlled rheometer RS75 (cone angle: 1 °, diameter: 60 mm) manufactured by Harke.

Using each of the obtained inks, printing is performed on printing paper ("ideal paper thin mouth" manufactured by Riso Kagaku Kogyo Co., Ltd.) with the stencil printing apparatus (prototype manufactured by Riso Kagaku Kogyo Co., Ltd.) shown in Figs. The printed matter obtained was evaluated for image quality (sharpness of fine characters), drying property, and printing density of the first sheet after landing.
The evaluation of image quality is made by visual inspection. The sharpness of thin characters is indicated by ◯ when fine characters (6 points) were sufficiently readable, △ when difficult to read, and × when impossible. Expressed as:
The dryness of the printed matter was evaluated based on the smudge of the finger when touching the image. If the finger did not get dirty even after touching 3 seconds after printing, ○ What was soiled even after 2 seconds was represented by x.
The printing density of the first sheet after the plate-fixing is ◎ when the printing density of the first printed material is equivalent to the printing density of the 20th printed material, ◯ when the printing density is slightly thinner than the 20th printed material, 20 Those that were much thinner than the first printed product were represented by Δ.
The results are also shown in Table 1.

  As shown in the above table, in each of the examples, compared to the comparative example, it was possible to obtain a printed material having good fine character sharpness, good dryness of the printed material, and the like.

1 is a schematic configuration diagram showing an embodiment of a suitable stencil printing apparatus. 1 is a perspective view of a drum, showing an embodiment of a suitable stencil printing apparatus. FIG. 3 is a cross-sectional view taken along the line A1-A1 in FIG. 2, showing an embodiment of a suitable stencil printing apparatus. FIG. 3 is a cross-sectional view taken along line B1-B1 in FIG. 2, showing an embodiment of a suitable stencil printing apparatus. It is a top view of the drum which shows one Embodiment of a suitable stencil printing apparatus and shows an ink supply part. One embodiment of a suitable stencil printing apparatus is shown, and is a cross-sectional view taken along line C1-C1 in FIG. It is a fragmentary sectional view showing one embodiment of a suitable stencil printing apparatus and explaining an ink diffusion mechanism. It is the schematic block diagram which showed typically the apparatus used for the measurement of a kite length.

Explanation of symbols

18 Stencil Paper 26 Drum 35 Press Roll 37 Printing Paper (Printing Medium)
53 Outer wall 54 Ink supply means 55A, 55B, 55C, 55D Ink supply section 55d Ink supply port 56 Ink M Printing direction N Printing orthogonal direction

Claims (3)

  The ink viscosity at 10 Pa when the shear stress is increased from 0 Pa at a speed of 0.1 Pa / s at 23 ° C. is 500 mPa · s or less, and a chromium steel ball having a diameter of 15 mm is pulled from the ink at 150 ° C. at 23 ° C. An ink for stencil printing having an ink string length of 30 mm or more and a surface tension of 40 mN / m or more.   The stencil printing ink according to claim 1, which is a water-based ink.   A drum that is rotatable and has a stencil sheet mounted on the surface of its outer peripheral wall, an ink supply means for supplying ink from the upstream side of the maximum printing area of the outer peripheral wall of the drum, and a fed printing medium Using a stencil printing machine equipped with a press roll that presses against the outer peripheral wall, the ink is passed through the perforated part of the stencil sheet that has been made by pressing the press roll while rotating the drum on which the stencil sheet has been made. A stencil printing method for transferring to a printing medium, wherein the stencil printing ink according to claim 1 or 2 is used as the ink.

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