WO2004003092A1

WO2004003092A1 - Non-aqueous ink composition and method for preparation thereof

Info

Publication number: WO2004003092A1
Application number: PCT/JP2003/007935
Authority: WO
Inventors: Toshihiro Endo; Hiroyuki Ogawa; Teruaki Okawa; Osamu Matsumoto; Yasuo Yamamoto
Original assignee: Riso Kagaku Corporation
Priority date: 2002-06-27
Filing date: 2003-06-23
Publication date: 2004-01-08
Also published as: JP2004083862A

Abstract

A non-aqueous ink composition containing a solvent, a coloring pigment and a dispersant and having a viscosity at 23°C of 30 mPa · s or less, characterized in that it further comprises solid particles which have substantially no coloring ability and are capable of preventing the movement of the coloring pigment, during the printing onto a recording paper, from the front surface of the recording paper to the backside thereof. The non-aqueous ink composition has a low viscosity and allows the formation of an image having high quality being reduced in strike-through and oozing and thus of high quality, even when use is made of a recording paper not being specially processed, that is, an ordinary paper.

Description

Description Non-aqueous ink composition and method for producing the same [Technical Field]

The present invention relates to an ink composition for use in a printer for performing recording, and more particularly to a low-viscosity non-aqueous ink composition and a method for producing the same.

[Background technology]

The ink jet recording system is a printing system that ejects liquid ink with high fluidity from fine nozzles and prints it by attaching it to a recording medium such as paper.It is a relatively inexpensive device with high resolution and high quality. The system is capable of printing images at high speed and with low noise, and is a system that is rapidly spreading recently.

The inks used in this ink jet recording system are broadly classified into aqueous type inks and non-aqueous type inks. The water-based ink is obtained by dissolving a water-soluble dye in a glycol-based solvent and water, etc. and dispersing a solid pigment in a glycol-based solvent and water to improve light resistance and image bleeding. Is also used. Further, it is better that the ink liquid ejection speed is high in order to print at high speed, and it has been proposed to add silica particles to an aqueous solvent in order to increase the ink liquid ejection speed (Japanese Patent Laid-Open Publication No. Heisei 9 (1999) -207). 5-1 1 7 5 6 2 publication). However, in any case, there is a problem that the water-based type ink generally has poor water resistance.

On the other hand, non-aqueous type inks have the advantage of being superior in water resistance. This non-aqueous type ink mainly includes a solvent-based ink mainly composed of a volatile solvent and a non-volatile solvent mainly. Oil-based ink. In particular, the latter oil-based ink has the feature that the number of times of cleaning during printing is small because nozzle clogging is unlikely to occur, and is more suitable as ink for high-speed inkjet printers. Oil-based inks have the problem of causing ink bleeding or strike-through when a dye soluble in a solvent is used as a coloring agent.Therefore, a pigment is used as a coloring agent and the dispersibility of this pigment is improved to improve the dispersibility of the nozzle Clogging is suppressed. As a method for improving the dispersibility of the pigment, for example, a silica particle table is used. It has been proposed that a color pigment be physically bonded to the surface (Japanese Patent Application Laid-Open No. 2003-49096).

In the field of stencil printing, in which stencil printing is performed using a stencil sheet and ink is supplied from a perforated portion formed in the stencil sheet to print on a printing material such as paper, the stencil printing is performed on one side of a porous support. In addition, a stencil printing system that uses a stencil sheet coated with a porous resin film to close the pores of the porous resin film corresponding to the non-image area to form an opaque non-inking part (Japanese Patent Application No. 2000-01) — 283600) or a stencil printing system using a microporous stencil made of an inelastic resin film (Japanese Patent Application Laid-Open No. 2002-21040) has been proposed. . These stencil printing systems have received great attention because the use of low-viscosity inks can dramatically improve the drying properties of inks compared to conventional systems. A stencil system is called a low-viscosity stencil system).

Inks used in such a low-viscosity stencil system include water-based inks, water-in-oil emulsion inks, and non-aqueous inks.However, ink dries on the plate or printing drum, causing clogging. Because of the difficulty, oil-based ink is often selected. '

Both the ink jet recording system and the low viscosity stencil system require the use of low viscosity ink, and when an image is formed on a permeable recording medium such as paper (hereinafter referred to as recording paper), Due to the low viscosity of the ink, the coloring material moves to near the back side of the recording paper, and there is a problem that an image can be seen through from the back side, that is, so-called strike-through occurs. In particular, this tendency is remarkable in plain paper in which the voids between the fibers of the paper are large, since the coloring material easily moves.

In order to solve such a problem, a method has been proposed in which the coloring material is fixed to the recording paper surface by performing a special process such as applying a pigment or the like to the recording paper surface to reduce strikethrough. However, the use of such specially processed coated paper or inkjet paper has a problem when the printing cost increases.

The present invention has been made in view of the above circumstances, and has excellent water resistance and high quality images with little strikethrough and little image bleeding even on recording paper that has not been subjected to special processing, so-called plain paper. To provide a low-viscosity ink composition that can be formed It is assumed that.

[Disclosure of the Invention]

The non-aqueous ink composition of the present invention contains at least a solvent, a color pigment, and a dispersant,

23 A non-aqueous ink composition having a viscosity of 3 OmPas or less at 23 ° C, which substantially prevents the coloring pigment from moving from the front surface to the back surface of the recording paper during printing on recording paper. It is characterized by containing solid particles having no specific coloring ability. The solid particles having substantially no coloring ability for preventing the coloring pigment from moving from the front surface to the back surface of the recording paper during printing on the recording paper are referred to as recording particles in a process in which ink penetrates into the recording paper. The fact that the coloring pigment contained in the ink stays in the fiber of the paper and prevents it from moving from the front surface to the back surface of the recording paper, and is itself a solid particle having no function of coloring the recording paper. means. Therefore, as long as it has such a function, the shape is not necessarily required to be particulate, and for example, it may be fine fibrous. However, if the solid particles are bonded to the color pigment, the interaction between the silica particles is hindered by the bonded color pigment, so that the ink remaining in the fiber voids of the paper does not have a thickening effect and the fiber voids are not generated. The solid particles combined with the coloring pigment are removed because the remaining ink escapes to the back of the paper. -The solid particles are preferably, for example, silicon particles. More preferably, the sily particles are contained in the ink composition in an amount of 1 to 10% by weight. In this case, the average particle diameter of the silica particles is desirably 300 nm or less. Further, the average particle size of the silica particles is preferably 0.1 to 10 times the average particle size of the color pigment.

The non-aqueous ink composition of the present invention includes the solvent, the dispersant, and the silica particles, and includes a silica particle dispersion liquid that does not include the color pigment, the solvent, the dispersant, and the color pigment. It is preferably obtained by mixing with a color pigment dispersion liquid containing no silica particles. In this case, the dispersant contained in the silica particle dispersion is a polyesteramine-based polymer dispersant, and the content of the polyesteramine-based polymer dispersant with respect to the silicic acid particles is a weight ratio. Is preferably 0.1 or more.

The method for producing a non-aqueous ink composition according to the present invention includes the step of: After preparing a silica particle dispersion liquid containing power particles and not containing the color pigment, and a color pigment dispersion liquid containing the solvent, the dispersant and the color pigment, and containing no silica particles, respectively, It is characterized by mixing a silica particle dispersion and the above-mentioned color pigment dispersion.

The strike-through occurs more easily as the color material contained in the ink moves from the recording surface of the recording paper to the back surface. In particular, strike-through is remarkable in printing and recording inks having low viscosity and small dispersion of pigment particles, and plain paper with large voids between fibers.

In the non-aqueous ink composition of the present invention, in a non-aqueous ink composition having a viscosity at 23 ° C. of 3 OmPas or less, the coloring pigment moves from the recording paper surface to the back surface during printing on the recording paper. Since the ink contains solid particles that have substantially no coloring ability, the solid particles stay in the fibers of the recording paper and are contained in the ink during the process of ink penetration into the recording paper. This prevents color pigments from moving from the front side to the back side of the recording paper, and has no function of coloring the recording paper itself, so that strikethrough can be effectively prevented. In addition, on the surface of the recording paper, the coloring pigment also moves in the horizontal direction of the recording paper.However, since the solid particles stay in the fibers of the recording paper, the movement of the coloring pigment in the horizontal direction can be prevented. As a result, bleeding of an image can be reduced, and a high-quality printed matter can be obtained.

In particular, in the non-aqueous ink composition of the present invention, since the solid particles are not bonded to the color pigment, most of the solvent is absorbed by the fibers of the paper when the ink is transferred to the paper, and the silica particles ( (Solid) ink remains. In such a state, the ink viscosity increases due to the interaction between the silica particles (hydrogen cross-linking of silanol groups), and the ink is prevented from passing through the fiber voids of the paper to the back side, and the strike-through effect is suppressed. Can be prevented.

When silica particles are used as the solid particles, the above-mentioned strikethrough can be effectively prevented by containing 1 to 10% by weight in the ink composition, and the ink jet recording can be performed. High-quality image formation with less image bleeding is possible in systems and low-viscosity stencil systems.

In this case, by setting the average particle diameter of the silica particles to 300 nm or less, the average particle diameter of the silica particles is further reduced to 0.1 to 10 times the average particle diameter of the color pigment. By doing so, it is possible to more effectively prevent the strikethrough. The non-aqueous ink composition of the present invention contains the solvent, the dispersant, and the silica particles, and includes the silica particle dispersion liquid that does not include the color pigment, and includes the solvent, the dispersant, and the color pigment. After preparing the color pigment dispersion liquid not containing the sily particles, respectively, mixing the silica particle dispersion and the color pigment dispersion to obtain the silica particles dispersion and the color pigment in the non-aqueous ink composition It is easy to control the size of each particle, and the effect of suppressing strikethrough and image bleeding can be more easily obtained.

[Preferred embodiment for carrying out the invention]

The non-aqueous ink composition of the present invention is a non-aqueous ink composition containing at least a solvent, a coloring pigment, and a dispersant, and having a viscosity of not more than 30 mPas at 23 ° C. It contains particles.

Examples of solid particles include inorganic fine particles such as silica, clay, talc, clay, diatomaceous earth, calcium carbonate, barium carbonate, barium sulfate, titanium oxide, alumina white, silica, myriki, and aluminum hydroxide. In addition, organic fine particles such as polyacrylate, polyurethane, polyester, polyethylene, polypropylene, polychlorinated biel, polyvinylidene chloride, polystyrene, polysiloxane, phenolic resin, epoxy resin, and benzoguanamine resin, or copolymers thereof. Fine particles composed of a body are used. It is desirable that these solid particles have high wettability with respect to the solvent to be used. However, even if the solid particles have low wettability by appropriately selecting a dispersant, they can be used.

The above solid particles may be used alone or in an appropriate combination. The amount of solid particles to be added varies depending on the type of solid particles. However, it is desirable to contain 1 to 4% by weight.

When the amount is less than 1% by weight, the effect of preventing the color pigment from moving from the front surface to the back surface of the recording paper is reduced, and the effect of preventing strike-through is reduced. On the other hand, the larger the amount of addition, the greater the effect of reducing strike-through, but if added too much, the viscosity of the ink increases, making it difficult to eject ink from the head in an ink jet recording system, or in the stencil system. Poor ink permeability of stencil paper causes poor image formation Live. On the other hand, if the added amount of the silica particles is too large, the ink viscosity particularly in a stationary state increases, and the thixotropic property increases. This thixotropic property means that the particle size is 1 μπ! This is manifested by dispersing fine particles called colloid particles of ~ 1 nm in a liquid.When the shear stress applied to this dispersion is small, such as in a static state, the viscosity increases, and when it is stirred, When the shear stress is large as in the above, the viscosity decreases. In particular, in an ink jet recording system, there is a close relationship between ink viscosity and the amount and speed of ink ejection, and if ink has thixotropic properties, the viscosity of the ink changes depending on the environment and conditions in which the ink is placed. As a result, stable ink ejection cannot be performed. Therefore, by making the ink not exhibit thixotropic properties, more specifically, by setting the viscosity at a shear stress of 100 (lZs) to within twice the shear stress at a shear stress of 100 (lZs), It enables stable image formation regardless of the environment where the ink is placed. In addition, by appropriately selecting the polar solvent described below, and further suitably selecting the dispersing agent described later, it becomes possible to add more silica particles without developing thixotropic properties. Even when such a method is employed, it is not preferable to add too much silicic acid particles because the thixotropic properties are exhibited. Therefore, when solid particles other than silica particles are used, the addition amount can be adjusted from these viewpoints.

In the case of silica particles, though it varies slightly depending on the type of recording paper, strike-through can be further reduced by setting the average particle diameter of the silica particles in the ink to 300 nm or less. The average particle size of the silica particles is preferably 300 nm or less, more preferably 200 nm or less, and further preferably 150 nm or less. The average particle diameter of the silica particles is preferably 0.1 to 10 times the average particle diameter of the color pigment. If the average particle size of the silica particles is smaller than 0.1 times the average particle size of the color pigment, or if the average particle size of the silica particles is larger than 10 times the average particle size of the color pigment, strikethrough occurs. More likely to happen.

The solvent used in the non-aqueous ink composition of the present invention may be a polar solvent or a non-polar solvent. Examples of the polar solvent include ester solvents, alcohol solvents, and higher fatty acid solvents. , Ether-based solvents and their mixed solvents can be used You. The polar solvent is selected to be a single phase when mixed with a non-polar solvent.

Specifically, methyl laurate, isopropyl laurate, isopropyl myristate, and phenol. Noremichin isopropyl, Nono ⁰ Noremichin isostearyl, methyl Orein acid, Orein acid Echiru, Orein isopropyl, butyl Orein acid, Li Nord methyl, isobutyl linoleate, Li Nord acid Echiru, isopropyl isostearate, soybean oil methyl, large Soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, getyl sebacate, propylene glycol monopotassium, trimethylolpropane triethylhexane, glyceryl trihexyl hexate, etc. Ester solvents, alcohol solvents such as isomiri stino oleanol, isopalmitino real alcohol, isostearyl alcohol, oleyl alcohol, etc., isononanoic acid , Isomiristinic acid, hexadecanoic acid, isopalmitic acid, oleic acid, isostearic acid, etc., higher fatty acid solvents, getyl glycol monobutyl ether, ethylene daryl monobutyl ether, propylene glycol monobutynoate ether, propylene glycol diethylene glycol Examples include ether solvents such as butyl ether. -Non-polar solvents include non-polar solvents such as naphthenic solvents, paraffinic solvents, and isoparaffinic solvents. Specifically, Ekuson's I sopar G, I sopar H, I sopar L, I sopar ME xxo 1 D 40, E xxol D 8 0, E xxo 1 D 1 0 0, E xxo 1 D 1 30 N E xxol D 140, Nippon Oil Company's AF_4, AF-5, AF-6, AF-7, No. 0 Sonorevent L, No. 0 Solven M, No. 0 Solvent H, Techleen N-- 16, Techleen N-- 20, Techlin N-22, Nisseki Isozonole 300, Nisseki Aisosol 400, S Stone Naphthesol, Nisseki Naphthesol M, Stone Naphthesol 1, Sanseng Co., Ltd., Sansen, Samper and the like.

As the above solvent, for example, a polar solvent or a non-polar solvent may be used alone, or two or more types may be appropriately selected and used, or a polar solvent and a non-polar solvent may be appropriately used in combination. Is also possible.

Dispersing agents include carboxylic acid esters containing hydroxyl groups and long-chain polyaminoamides. High-molecular-weight acid ester salt, high-molecular-weight polycarboxylic acid salt, long-chain polyaminoamide and polar acid ester salt, high-molecular-weight unsaturated acid ester, polymer copolymer, modified polyurethane, modified polyatalylate, poly Ether ester type anionic surfactant, naphthalene sulfonic acid formalin condensate, aromatic sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate, polyoxyethylene phenol ether, polyester polyamine, stearylamine ace Tates and the like can be used.

Specific examples of the dispersing agent include “Anti_Terra_U (polyaminoamide phosphate)” manufactured by BYK Chemie and “Anti-Terra—203322 (high molecular weight polycarboxylic acid). Salt), ”Disperbyk—101 (polyaminoamide phosphate and acid ester), 107 (hydroxyl-containing carboxylic acid ester), 110 (copolymer containing acid group), 130 ( (Polyamide), 161, 162, 163, 164, 165, 1666, 170 (polymer copolymer) "," 400 "," Bykum " en (high molecular weight unsaturated acid ester) "," BYK_P104, PI05 (high molecular weight unsaturated acid polycarboxylic acid) "," P104S, 240S (high molecular weight unsaturated) Acid polycarboxylic acid and silicone) and Lactimon (long-chain amine, unsaturated acid polycarboxylic acid and silicon).

In addition, `` Efka C HEMICALS Co., Ltd.``F force 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 7 6 4, 7 6 6 ”,“ F-Polymer 100 (modified polyacrylate), 150 (aliphatic modified polymer), 400, 401, 402, 400, 45 0, 451, 4552, 4553 (denatured poly acrylate), 745 (copper phthalocyanine), Kyoeisha Chemical Co., Ltd., "Floren TG—710 (urethane oligomer)", "Floren DO PA-15B (acrylic oligomer)", "Floren SH-290, SP-100", "Polyflow No.500E, No.300 (Atalyl) ) Kusumoto Kasei Co., Ltd. “DISVALON KS-860, 873 SN, 874 (polymer dispersant), # 2150 (aliphatic polycarboxylic acid), # 7004 (polyetherester type) "DA-703-50 (polyester acid Amide amine salt) ”.

Furthermore, Kao's “Demol RN, N (formalin naphthalenesulfonic acid condensation) Sodium salt), MS.C, SN-B (sodium salt of aromatic sulfonic acid formalin condensate), EP "," Homogenol L-18 (polycarboxylic acid type polymer) "," Emanoregen 920, 930, 931, 935, 955, 985 (polyoxyethylennoninolephenyl phenyl), `` acetamin 24 (coconut amine acetate), 86 (stearylamine) Acetate), Abyssia's "Sol Sperse 500 000 (phthalocyanine ammonium salt)", 139400 (polyesteramine), 17 000, 18000 (fatty acid amine), 22000, 2400 , 28 000 ”, Nikko Chemical's“ Nikkor T106 (polyoxyethylene sorbitan monooleate), MYS—IEX (polyoxyethylene monostearate), Hexagline 4-O (hexaglyceryl tetraolate) ” etc And the like.

As the color pigments, those generally used in the printing technical field can be used irrespective of inorganic pigments and organic pigments. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, pyridian, cobalt green, ultra limb benzole, puno ressible blue, kobanoleto blue , Azo-based pigments, lid-based cyanine-based pigments, quinatalidone-based pigments, isoindolinone-based pigments, dioxazine-based pigments, selen-based pigments, perylene-based pigments, perinone-based pigments, thioindigo-based pigments, quinofata-based pigments Conventionally known pigments such as a system pigment and a metal complex pigment can be used without any particular limitation.

The above pigments may be used alone or in an appropriate combination, and are desirably contained in the range of 0.01 to 20% by weight based on the whole ink composition.

The non-aqueous ink composition of the present invention can be manufactured by a conventionally known manufacturing method.However, silica particles and a coloring pigment are separately prepared as a dispersion, and then mixed with each other to obtain silica particles. A non-aqueous ink composition in which the color pigment is not physically bound can be obtained. That is, a silica particle dispersion liquid containing a solvent, a dispersant, and silica particles and containing no color pigment, and a color pigment dispersion liquid containing a solvent, a dispersant, and a color pigment but containing no silica particles were prepared. Mix It is preferable to obtain a non-aqueous ink composition in total. The solid particles and the coloring pigment can be dispersed by a conventionally known dispersing means such as a bead mill.

Hereinafter, the present invention will be described more specifically with reference to examples.

(Example 1)

Dissolve 3 parts by weight of Solsperse 139400 (polyesteramine-based polymer dispersant: Abyssia) as a dispersing agent in 8 parts by weight of a vegetable fatty acid ester solvent. : Mitsubishi Chemical Corporation) 5 parts by weight were added and premixed. Thereafter, the mixture was dispersed in a bead mill with a residence time of about 20 minutes to obtain a pigment dispersion. On the other hand, 56 parts by weight of a vegetable fatty acid ester solvent and 20 parts by weight of a naphthenic solvent are mixed, and 4 parts by weight of Solsperse 139400 as a dispersing agent are dissolved therein, and further, aerogel as silica particles is dissolved. 4 parts by weight of R972 (manufactured by Nippon Aerosil Co., Ltd.) were added and premixed, and then dispersed in a bead mill with a residence time of about 20 minutes to obtain a silica dispersion. The obtained pigment dispersion and silica dispersion were mixed to obtain an ink.

(Example 2)

An ink was obtained in the same manner as in Example 1 except that aerogel RY200 (produced by AEROSIL Co., Ltd.) was used as the silica particles. -(Example 3)

An ink was obtained in the same manner as in Example 1 except that aerogel R812 (manufactured by Nippon Aerosil Co., Ltd.) was used as the silica particles.

(Example 4)

An ink was obtained in the same manner as in Example 1 except that aerogel OX50 (manufactured by Nippon Aerosil Co., Ltd.) was used as the silica particles.

(Example 5)

An ink was obtained in the same manner as in Example 1 except that the composition of the silica dispersion was changed as shown in Table 1.

(Example 6)

(Example 7) An ink was obtained in the same manner as in Example 1 except that the composition of the silica dispersion was changed as shown in Table 1.

(Example 8)

An ink was obtained in the same manner as in Example 1 except that the composition of the silica dispersion was as shown in Table 1 and the pigment was changed to Pigment Yellow (manufactured by Dainichi Seika).

(Example 9)

An ink was obtained in the same manner as in Example 3, except that the formulation of the silica dispersion was as shown in Table 1.

(Example 10)

An ink was obtained in the same manner as in Example 8, except that the residence time of the sily dispersion was 60 minutes.

(Comparative Example 1)

62 parts by weight of a vegetable fatty acid ester and 20 parts by weight of a naphthenic solvent were mixed with the pigment dispersion obtained in the same manner as in Example 1 to obtain an ink.

(Comparative Example 2)

An ink was obtained in the same manner as in Example 1 except that aerogel R972 was used as the sily particles, and the mixing of the shiri force dispersion was as shown in Table 1.

(Comparative Example 3)

Table 1 shows the ink formulations of Examples 1 to 10 and Comparative Examples 1 and 3, and a summary of the ink viscosities, pigment particle diameters, and silica particle diameters.

【table 1 】

The ink viscosity, pigment particle size and silica particle size described in Table 1 were measured as follows.

12 26 Measurement of ink viscosity>

Shear when the shear stress was increased from 0.7 to 100 (lZs) in 60 seconds at 23 ° C using a 6 cm diameter cone with a Haake Rheometer RS75. The viscosity when the stress was 100 (1 / s) was measured.

The pigment dispersion is diluted with a solvent so that the pigment concentration becomes 0.1%, printed on plain paper (“Ideal Paper Thick S”, manufactured by Riso Kagaku Kogyo Co., Ltd.), and the printed portion is scanned with a scanning electron microscope. The pigment particles which can be observed on paper fibers were selected arbitrarily, and the diameter (the direction in which the length becomes the longest) of the pigment particles was measured, and the average value was defined as the particle diameter.

Measurement of silica particle size>

As with the pigment particle size, the silica dispersion is diluted with a solvent so that the silica concentration is 0.1%, and this is printed on plain paper (“Ideal Paper Thick s” manufactured by Riso Kagaku Kogyo Co., Ltd.). Observe the letter-shaped part with a scanning electron microscope, select 100 silica particles that can be observed on the paper fiber, measure the diameter of the silica particles (the direction in which the length becomes the longest), and calculate the average value of the particles. Diameter.

(Evaluation method)-strike-through and image quality by using the inkjet system>

Print a 2cm square solid on plain paper (Riso Kagaku Kogyo “Ideal Paper Thickness S”) with an ink jet, leave it for 24 hours, and measure the back side of the solid part with an OD meter (Macbeth) And evaluated as follows.

〇: OD value is less than 0.13

: 00 value is 0.13 or more and less than 0.20

X: OD value is 0.20 or more

In addition, the image quality was evaluated as follows.

〇: No blurring of image

X: Image blurring (ink ejection failure)

Average pore size on one side of porous support (Japanese paper) 5.? ! ! ^ Density. 3. Digital stencil printing machine using stencil paper having a porous resin layer of 9 g / cm ³ (RP 3790: Riso Kagaku Kogyo Co., Ltd.), print on plain paper (Riso Kagaku Kogyo Co., Ltd., “Ideal Paper Thick S”), leave it for 24 hours, then OD the solid back. A total (Macbeth) was used and evaluated as follows.

〇: OD value is less than 0.13

/: 00 value is more than 0.13 and less than 0.20

X: 00 value is 0.20 or more

In addition, the image quality was evaluated as follows.

〇: No blurring of image

X: Blurring of the image (poor ink transfer)

The inks of Examples 1 to 8 and Comparative Examples 1 and 2 were evaluated by the above evaluation methods. Table 2 shows the results.

漭啉 I ¾

As is clear from Table 2, the ink compositions of Examples 1 to 10 have a viscosity at 30 ° C of 30 mPas or less, and are therefore suitable for ink jet recording systems and low viscosity stencil systems. Even if it is used, there will be no problem when ink ejection from the head becomes difficult or the ink permeability of the stencil paper becomes poor, resulting in poor image formation.Silica particles are used as solid particles. Since it was contained, it became possible to effectively prevent strikethrough.

In addition, since the solid particles stay on the recording paper fibers on the recording paper surface, the movement of the coloring pigment in the horizontal direction can be prevented, so that the bleeding of the image can be reduced. It became possible and high quality printed matter was obtained. In fact, when the cross section of the printed matter was observed with an optical microscope, it was found that in Examples 1 to 10 in which the silica particles were added, the amount of the colored pigment moved to the back side of the paper as compared with Comparative Example 1 in which no silica particles were contained. Was observed to be low. This effect was observed regardless of the pigment particle size. Although the larger the amount of silica particles added, the greater the effect of reducing strike-through, the ink viscosity increased (38 mPa · s) in Comparative Example 2 in which the added amount was 15 parts by weight. In the inkjet recording system, it was difficult to discharge ink from the head, and in the stencil system, the ink permeability of the stencil paper became difficult. In Comparative Example 3, since the content of the polyesteramine-based polymer dispersant was as small as 0.05 in terms of the weight ratio with respect to the silicic acid particles, a silica dispersion in which the dispersion state of the silica particles was stable could not be obtained. I got it.

When the average particle diameter of the silica particles is about 300 nm or less, the show-through reduction effect and the image formation are good. In Example 5, some breakthrough of force with an average particle diameter of 300 nm or less was observed. This is because the added amount of silica particles is as low as 0.5 part by weight. Also, in Example 10, although strike-through was slightly observed even though the average particle size was 300 nm or less, the average particle size of the silica particles was less than 0.1 times the particle size of the color pigment. For.

As described above, in the ink composition of the present invention, in a non-aqueous ink composition having a viscosity of 3 OmPas or less at 23 ° C, the color pigment is printed from the surface of the recording paper when printing on the recording paper. Since the ink contains solid particles that have substantially no coloring ability that prevents it from moving to the back surface, the solid particles are converted into fibers of the recording paper during the process of ink penetration into the recording paper. The color pigment contained in the ink stays in the ink and is prevented from moving from the front side to the back side of the recording paper, and the solid particles themselves do not have the function of coloring the recording paper. It became possible to prevent.

The non-aqueous ink composition of the present invention may contain, for example, various additives other than the solvent, the color pigment, the dispersant, and the solid particles.In Examples, silica particles are used as the solid particles. However, even if solid particles other than the above are used, the strike-through reduction effect of the present invention and high-quality image formation without image bleeding can be realized.

Claims

The scope of the claims

1. A non-aqueous ink composition containing at least a solvent, a coloring pigment, and a dispersing agent and having a viscosity of 30 mPas or less at 23 ° C, wherein the coloring pigment is used for printing on recording paper. A non-aqueous ink composition comprising solid particles having substantially no coloring ability for preventing the recording paper from moving from the front surface to the back surface.

2. The non-aqueous ink composition according to claim 1, wherein the solid particles are silica particles.

3. The non-aqueous ink composition according to claim 2, wherein the ink composition contains 1 to 10% by weight of the silica particles.

4. The non-aqueous ink composition according to claim 3, wherein the silica particles have an average particle diameter of 300 nm or less.

5. The non-aqueous liquid according to claim 2, wherein the average particle diameter of the silica particles is 0.1 to 10 times the average particle diameter of the coloring pigment. Based ink composition.

6. A silica particle dispersion containing the solvent, the dispersant, and the silica particles, and not containing the color pigment, and a color pigment containing the solvent, the dispersant, and the color pigment, but not containing the silica particles. The non-aqueous ink composition according to any one of claims 2 to 5, wherein the composition is obtained by mixing with a dispersion.

7. The dispersant contained in the silica particle dispersion is a polyesteramine-based polymer dispersant, and the content of the polyesteramine-based polymer dispersant with respect to the silica particles is 0. 7. The non-aqueous ink composition according to claim 6, wherein the composition is 1 or more.

8. A silica particle dispersion containing the solvent, the dispersant, and the silica particles, and not containing the color pigment, and a color pigment containing the solvent, the dispersant, and the color pigment, but not containing the silica particles. A method for producing a non-aqueous ink composition, comprising: preparing a dispersion liquid and then mixing the silica particle dispersion liquid and the color pigment dispersion liquid.