JP2012161981A - Post-processing agent for nonaqueous ink, ink set, and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a post-processing agent for a nonaqueous ink that can reduce strike-through and obtain high printing density.SOLUTION: The post-processing agent for the nonaqueous ink includes: a non-organic particle containing silica and/or alumina; and water.

Description

  The present invention relates to a post-treatment agent for non-aqueous ink, an ink set, and a printing method.

  The ink jet recording method is a printing method in which printing is performed by ejecting liquid ink having high fluidity from a fine nozzle and attaching it to a recording medium such as plain paper. This method has a feature of being capable of printing a high-resolution, high-quality image with high speed and low noise with a relatively inexpensive apparatus, and has been rapidly spread recently.

  In terms of the solvent, the ink is large and can be divided into water-based ink and non-water-based ink. Non-water-based inks that do not use water as a solvent for inks, such as solvent-based inks mainly composed of volatile solvents and oil-based inks mainly composed of non-volatile solvents, are stable on the machine (intermittent ejection, left for a long time) It has been attracting attention because it has features such as good ejection recovery later), no curling of the recording medium, and a short ink permeation drying time.

  When printing non-aqueous ink on plain paper or other recording media, the phenomenon that the coloring material contained in the ink penetrates the inside of the recording paper together with the solvent and the ink penetrates the back side of the recording medium (so-called back-through) occurs. Or the density of the surface of the recording medium may be reduced.

  In Patent Document 1, after performing ink jet recording using a pigment ink, an aqueous post-treatment liquid containing pigment particles is applied to a recording medium to solve the occurrence of uneven gloss and a decrease in abrasion resistance. Has been proposed. The pigment ink used in Patent Document 1 contains water containing a pigment-based colorant.

  Patent Document 1 does not disclose a post-treatment agent suitable for a non-aqueous ink, and no proposal is made to prevent a show-through or a decrease in printing density which is a problem in the non-aqueous ink.

JP 2003-291484 A

  An object of the present invention relates to a post-treatment agent for non-aqueous ink, an ink set, and a printing method, which can reduce back-through and obtain a high printing density.

  One aspect of the present invention is a post-treatment agent for non-aqueous ink containing inorganic particles containing silica and / or alumina and water.

  Another aspect of the present invention is an ink set that is a combination of a non-aqueous ink containing a color material and a non-aqueous solvent and the above-described post-treatment agent for non-aqueous ink.

  According to still another aspect of the present invention, there is provided a printing method using the above-described ink set, wherein a non-aqueous ink is printed on a recording medium, and at least a printing surface is treated with a non-aqueous ink post-treatment agent. It is.

  According to the present invention, it is possible to provide a post-treatment agent for non-aqueous ink, an ink set, and a printing method capable of reducing the strike through and obtaining a high printing density.

  Hereinafter, embodiments according to the present invention will be described, but the examples in the present embodiment do not limit the present invention.

  A post-treatment agent for non-aqueous ink according to an embodiment of the present invention (hereinafter sometimes simply referred to as “post-treatment agent”) includes inorganic particles containing silica and / or alumina and water. . According to such a post-treatment agent, it is possible to reduce the show-through and obtain a high printing density.

  The post-treatment agent of this embodiment includes inorganic particles containing silica and / or alumina and water. The post-treatment agent of this embodiment can be used for printing a non-aqueous ink (hereinafter sometimes simply referred to as “ink”) on a recording medium and treating at least the printed surface. Accordingly, it is possible to suppress the penetration of the ink into the recording medium, reduce the breakthrough, and obtain a high image density. This is because the non-aqueous ink printed on the recording medium comes into contact with the post-treatment agent, the solvent in the non-aqueous ink is absorbed by the inorganic particles in the post-treatment agent, and the non-aqueous ink It is presumed that the color material is prevented from penetrating into the recording medium and the color material stays on the surface of the recording medium. Further, since the post-treatment agent is an aqueous medium, when the post-treatment agent contacts the recording medium, moisture in the post-treatment agent is absorbed by the recording medium, and the inorganic particles remain on the surface of the recording medium, and the solvent in the ink. Is more easily absorbed.

  The inorganic particles contain silica and / or alumina. The post-treatment agent may contain silica or alumina alone, or may contain both silica and alumina. Moreover, silica and / or alumina may be contained in the post-treatment agent as inorganic particles, and other inorganic particles may be further contained within a range not impairing the effects of the present invention. As an example, an alkali metal, an alkaline earth metal, a transition metal, a non-ferrous metal, or the like, or an oxide, hydroxide, sulfide, carbonate, sulfate, or the like thereof may be contained. For example, simple metals such as gold, platinum, silver, aluminum, or oxides such as silicon, aluminum, calcium, magnesium, titanium, zinc, barium, zirconium, manganese, iron, sodium, potassium, hydroxides, sulfides, Examples thereof include carbonates and sulfates. In particular, calcium carbonate, magnesium carbonate, titanium oxide, and zinc oxide can be preferably contained.

  The silica is not limited to this, and powdered silica, colloidal silica, synthetic amorphous silica, and the like can be used alone or in combination. Examples of the powder silica include AEROSIL 90 and OX 50 manufactured by Nippon Aerosil Co., Ltd., E-200A, E-220A, K-500, E-1009, E-1011, E-1030, and E- manufactured by Tosoh Silica Co., Ltd. 150J, E-170, etc. can be used. Examples of colloidal silica include Snowtex S, OS, XS, OXS, 20, 30, 40, 50, O, AK, AK-YL, O-40, CM, 20L, C, ZL manufactured by Nissan Chemical Industries, Ltd. , XL, N, UP, Quatron PL-1, PL-3, PL-7, PL-20 manufactured by Fuso Chemical Industry Co., Ltd., silicaloid, silicaloid-LL, silicaloid-A manufactured by Sanko Colloid Chemical Co., Ltd. Can be used. Synthetic amorphous silica is formed by neutralization reaction of silicate and acid, and can be divided into various properties depending on the production method. For example, Mizusuka Chemical Co., Ltd. Mizukacil P-73, P-78A , P-707, P-709, P-527, P-803, etc. can be used.

  For example, alumina sol 100, 200, 520 manufactured by Nissan Chemical Industries, Ltd., which is in the form of an aqueous dispersion, can be used as the alumina. In particular, from the viewpoint of stability as an aqueous phase component, alumina sol 520 (nitrite stabilized boehmite plate crystal type alumina) is preferable.

  The average particle diameter of the inorganic particles is not particularly limited, and can be appropriately selected and used within a range of 5 nm to 10 μm, for example. Here, the average particle diameter of the inorganic particles is obtained by measurement by a dynamic light scattering method. Specifically, it can be measured by a dynamic light scattering particle size distribution measuring device “LB500” manufactured by Horiba, Ltd. Depending on the type of inorganic particles, the average particle size of the inorganic particles may be a primary particle or an aggregate in which primary particles are aggregated, that is, a secondary particle. When the average particle size of the inorganic particles is small, the specific surface area increases, it becomes easier to absorb the solvent in the ink, and the coloring material is restrained from moving with the solvent, thereby reducing back-through and increasing the printing density. Obtainable. On the other hand, when the average particle size of the inorganic particles is large, the inorganic particles adhering to the surface of the recording medium may diffusely reflect light and the image quality may deteriorate. Therefore, it is preferable to be within the above range.

  Furthermore, the inorganic particles preferably contain silica having an average particle size of 30 nm to 150 nm. More preferably, it is 40 nm-140 nm, More preferably, it is 40 nm-100 nm. By being in this range, the showthrough can be further reduced and a high printing density can be obtained.

  The shape of the inorganic particles is not particularly limited, and an arbitrary shape can be used as appropriate. Examples of the shape of the primary particles of the inorganic particles include a spherical shape, a needle shape, a granular shape, a plate shape, a rod shape, a chain shape (a shape bent in a “<”) shape, a feather shape, and the like. Can be used. Examples of the shape of the secondary particles of the inorganic particles include a spherical shape, a needle shape, a granular shape, a plate shape, a rod shape, a chain shape, and a shape having a three-dimensional network structure, which can be appropriately selected and used.

  The shape of the inorganic particles is preferably an elongated shape such as a chain shape or a rod shape from the viewpoint of printing density. In particular, as a suitable shape of silica, the minor axis is 3 nm or more and less than 30 nm, more preferably 5 nm or more and 20 nm or less, and the major axis is 30 nm or more and 500 nm or less, more preferably 40 nm or more and 100 nm or less. When silica having a shape in this range is used, the average particle diameter of silica is more preferably 30 nm to 150 nm as described above. Moreover, as a suitable shape of an alumina, it is preferable that a short axis is 3 nm or more and less than 50 nm, More preferably, it is 40 nm or more and less than 45 nm, and a long axis is 50 nm or more and 100 nm or less, More preferably, it is 50 nm or more and 60 nm or less. This is presumably because the elongated aggregates overlap each other on the surface of the recording medium to form a film, absorb the solvent of the non-aqueous ink more efficiently, and suppress the penetration of the coloring material.

  As content in the post-processing agent of an inorganic particle, 1-20 mass% is preferable in conversion of solid content, and it is more preferable that it is 5-20 mass%. By being 1% by mass or more, it is possible to sufficiently obtain the effect of reducing the back-through and the printing density. From the viewpoint of preventing irregular reflection of light on the recording medium and the dispersion stability of inorganic particles in the post-treatment agent, the content is preferably 20% by mass or less.

  The water for the post-treatment agent is not particularly limited, and is preferably contained in the post-treatment agent by about 10 to 95% by mass. As water, it is preferable to use pure water such as ion-exchanged water or distilled water, or ultrapure water.

  For the post-treatment agent, a dispersant represented by a polymer dispersant or a surfactant may be used in order to stably disperse the inorganic particles.

  Examples of the polymer dispersant include commercially available Solsperse series (Solsperse 20000, 27000, 41000, 41090, 43000, 44000) manufactured by Nippon Lubrizol Co., Ltd. , 60, 62, 63, 71, 501) and the like.

  Examples of the surfactant include anionic surfactants such as the Kao Corporation Demall series (Demol N, RN, NL, RNL, T-45), and Kao Corporation Emulgen series (Emulgen A-60, A). Nonionic surfactants such as -90, A-500, B-40, L-40, 420).

  When the dispersant is used in the post-treatment agent, the blending amount in the post-treatment agent varies depending on the type and is not particularly limited, but is generally 0 with respect to the inorganic particles 1 in terms of the mass ratio of the active ingredient (solid content). It is preferably used in the range of 0.005 to 0.5.

The post-treatment agent may further contain a water-soluble solvent from the viewpoint of viscosity adjustment and a moisturizing effect. As the water-soluble solvent, an organic compound that is liquid at room temperature and is soluble in water can be used. For example, lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, 2-methyl-2-propanol; ethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, Diglycols such as dipropylene glycol and tripropylene glycol; glycerin; diglycerin; 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, Tiger ethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, glycol ethers such as tetraethylene glycol diethyl ether; triethanolamine, it can 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 solvents can be used alone or in combination of two or more.
The water-soluble solvent is preferably contained in the post-treatment agent by about 15 to 40% by mass.

  In addition to the above-mentioned components, the post-treatment agent optionally includes a surface tension adjusting agent (penetrating agent), an antifoaming agent, an antioxidant, a pH adjusting agent, a preservative, a wetting agent (moisturizing agent), a fixing agent, etc. Can be appropriately contained.

  As surface tension modifiers and antifoaming agents, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, or polymer-based, silicone-based, and fluorine-based surfactants Can be used.

  Specifically, as an anionic surfactant, Kao Corporation Emar series (Emar 0, 10, 2F, 40, 20C), Neopelex series (Neopelex GS, G-15, G-25, G- 65), Pelex series (Pelex OT-P, TR, CS, TA, SS-L, SS-H), and Demolle series (Demol N, NL, RN, MS).

  Examples of the cationic surfactant include Acetamine series (Acetamine 24, 86), Coatamine series (Coatamine 24P, 86P, 60W, 86W) and Sanizol series (Sanisol C, B-50) manufactured by Kao Corporation. Can be mentioned.

  Nonionic surfactants include acetylene glycol surfactants such as Surfynol series (Surfinol 104E, 104H, 420, 440, 465, 485) manufactured by Air Products, and Emulgen series (Emulgen 102KG manufactured by Kao Corporation). , 103, 104P, 105, 106, 108, 120, 147, 150, 220, 350, 404, 420, 705, 707, 709, 1108, 4085, 2025G) and the like. It is done.

  Examples of the amphoteric surfactants include the Amphitol series (Amphithol 20BS, 24B, 86B, 20YB, 20N) manufactured by Kao Corporation.

  By mix | blending antioxidant, the oxidation of a post-processing agent component can be prevented and the storage stability of a post-processing agent can be improved. For example, L-ascorbic acid, sodium L-ascorbate, sodium isoascorbate, potassium sulfite, sodium sulfite, sodium thiosulfate, sodium dithionite, sodium pyrosulfite, etc. can be used, Two or more kinds may be mixed and used.

  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 mix | blending antiseptic | preservative with a post-processing agent, the decay of a post-processing agent can be prevented and 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.

  As the wetting agent, polyhydric alcohols can be used.

  The method for adjusting the post-treatment agent is not particularly limited, and the post-treatment agent can be adjusted by mixing inorganic particles and optional components in water.

  The method for treating the post-treatment agent is not particularly limited, and the post-treatment agent can be treated on the recording medium by any method. For example, a gravure printing method, an ink jet recording method, a screen printing method, a roll coating method, a bar coating method, and the like can be appropriately selected and used.

The amount of the post-treatment agent applied is not particularly limited and can be appropriately adjusted and used. If the coating amount of the inorganic particles is too large, light may be irregularly reflected on the recording medium and the image quality may be deteriorated. If it is too small, the effect of absorbing the solvent in the ink may not be sufficiently obtained. Further, since the post-treatment agent contains water, if the application amount of the post-treatment agent is too large, the recording medium may be curled. From this viewpoint, the coating amount of the post-treatment agent is preferably 0.5 to 5 g / m ² in terms of solid content.

  An ink set according to an embodiment of the present invention is a combination of a non-aqueous ink containing a coloring material and a non-aqueous solvent and the above-described post-treatment agent for non-aqueous ink. According to such an ink set, the show-through can be reduced and a high printing density can be obtained.

  According to the ink set of the present embodiment, the non-aqueous ink is printed on the recording medium, and at least the printing surface is treated with the post-treatment agent. Since the non-aqueous solvent of the water-based ink is absorbed, the back-through can be reduced and a high printing density can be obtained.

  The recording medium is not particularly limited, and the thickness of the ink absorbing layer is larger than that of plain paper, high-quality plain paper, inkjet (IJ) paper, IJ matte paper, coated paper with a recording medium coated with an ink absorbing solution, and coated paper. Can be used for thin coated paper, glossy paper (photo glossy paper), special paper, cloth, etc. Specifically, in these recording media, ink permeation tends to be a problem, and according to the present embodiment, it is possible to further expect a reduction in strikethrough and an increase in print density.

  The non-aqueous ink contains a color material. The color material may be a pigment, a dye, or a combination thereof. Even in the case of dyes, there is a problem in that the density of the image is lowered and the back-through occurs because the dye enters the inside of the recording medium together with the nonaqueous solvent.

  The non-aqueous ink may have any color, and examples of pigments include organic pigments such as azo, phthalocyanine, dye, condensed polycyclic, nitro, and nitroso (brilliant carmine 6B, lake red C). , Watching Red, Disazo Yellow, Hansa Yellow, Phthalocyanine Blue, Phthalocyanine Green, Alkaline Blue, Aniline Black, etc.); Cobalt, Iron, Chromium, Copper, Zinc, Lead, Titanium, Vanadium, Manganese, Nickel and other metals, metal oxidation And sulfides, and inorganic pigments such as ocher, ultramarine, and bitumen, and carbon blacks such as furnace carbon black, lamp black, acetylene black, and channel black can be used. Any one of these pigments may be used alone, or two or more of these pigments may be used in combination.

  The average particle diameter of the pigment is preferably 300 nm or less, and more preferably 150 nm or less, from the viewpoints of dispersibility and storage stability. Here, the average particle diameter of the pigment is a value measured by a dynamic light scattering particle size distribution analyzer LB-500 manufactured by Horiba, Ltd.

  The content of the pigment in the ink is usually 0.01 to 20% by mass, and preferably 3 to 15% by mass from the viewpoint of printing density and ink viscosity.

  Non-aqueous ink dyes include azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, cyanine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes Oil-soluble dyes such as phthalocyanine dyes and metal phthalocyanine dyes are more preferable. Any one of these dyes may be used alone, or two or more of these dyes may be used in combination. The content of the dye in the ink is usually 0.01 to 20% by mass.

  When the non-aqueous ink contains a pigment, it may further contain a pigment dispersant. The pigment dispersant is not particularly limited as long as it can stably disperse the pigment in the solvent. For example, hydroxyl group-containing carboxylic acid ester, long chain polyaminoamide and 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, high molecular weight copolymer , Modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonyl phenyl ether, polyester polyamine, stearylamine acetate, etc. Of these, the use of a polymer dispersant is preferred. These may be used alone or in combination of two or more.

As specific examples of commercially available pigment dispersants,
“Solsperse 5000 (phthalocyanine ammonium salt type), 13940 (polyesteramine type), 17000, 18000 (fatty acid amine type), 11200, 22000, 24000, 28000” (all trade names);
“Efka CHEMICALS” “Efka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)” (both products) Name);
“Demol P, EP, Poise 520, 521, 530, Homogenol L-18 (polycarboxylic acid type polymer surfactant)” manufactured by Kao Corporation (all trade names);
“Disparon KS-860, KS-873N4 (amine salt of polymer polyester)” manufactured by Enomoto Kasei Co., Ltd. (both are trade names);
“Discall 202, 206, OA-202, OA-600 (multi-chain polymer nonionic)” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (all trade names);
Etc.

  The blending amount of the pigment dispersant in the non-aqueous ink can be appropriately set, but from the viewpoint of pigment dispersibility, the weight ratio is preferably about 0.05 to 1.0 part with respect to 1 part of the pigment. More preferably, it is 1 to 1.0 part. The pigment dispersant is preferably contained in an amount of about 0.5 to 10% by weight, more preferably 1 to 8% by weight, based on the total amount of ink.

  The non-aqueous ink contains a non-aqueous solvent. Here, the non-aqueous solvent refers to a non-polar organic solvent and a polar organic solvent having a 50% distillation point of 150 ° C. or higher. The 50% distillation point means a temperature at which 50% by weight of a solvent is volatilized, which is measured according to JIS K0066 “Testing method for distillation of chemical products”.

  For example, preferred examples of the nonpolar organic solvent include aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents and the like. Examples of the aliphatic hydrocarbon solvent and alicyclic hydrocarbon solvent include, for example, “Teclean N-16, Teclean N-20, Teclean N-22, Nisseki Naphthezol L, Nissho Naphthezol M, manufactured by Nippon Petroleum Corporation. Nisseki Naphthezol H, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Nisseki Isosol 300, Nisseki Isosol 400, AF-4, AF-5, AF-6, AF-7 ", manufactured by Exxon “Isopar G, Isopar H, Isopar L, Isopar M, Exxsol D40, Exxsol D80, Exxsol D100, Exxsol D130, Exxsol D140”, “Normal Paraffin H” manufactured by Japan Energy, etc. are preferable. Preferred examples of the aromatic hydrocarbon solvent include “Nisseki Clean Sol G” (alkylbenzene) manufactured by Nippon Petroleum Corporation, “Solvesso 200” manufactured by Exxon, and the like.

  As the polar organic solvent, ester solvents, alcohol solvents, higher fatty acid solvents, ether solvents, and mixed solvents thereof can be used. For example, selected from the group consisting of an ester solvent that is an ester of a higher fatty acid having 8 to 20 carbon atoms and an alcohol having 1 to 24 carbon atoms, a higher alcohol having 8 to 24 carbon atoms, and a higher fatty acid having 8 to 20 carbon atoms. One or more of them can be preferably used.

More specifically, as polar organic solvents, methyl laurate, isopropyl laurate, isopropyl myristate, isooctyl myristate, isopropyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate , Methyl linoleate, isobutyl linoleate, ethyl linoleate, isopropyl isostearate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate Ester solvents such as trimethylolpropane tri-2-ethylhexanoate and glyceryl tri-2-ethylhexanoate; isomyristyl alcohol, isopalmityl Alcohol solvents such as alcohol, isostearyl alcohol, oleyl alcohol, hexyl decanol, octyldodecanol, and decyltetradecanol; higher grades such as nonanoic acid, isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, and isostearic acid Preferred examples include fatty acid solvents; ether solvents such as diethyl glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, and propylene glycol dibutyl ether.
These non-aqueous solvents can be used alone or in combination of two or more.

  Among the non-aqueous solvents described above, solvents that are preferably used for non-aqueous inks include aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, higher alcohols, fatty acid esters, and the like. Since the post-processing agent has good mixing properties, the fluidity of the ink can be more efficiently lowered, and the back-through of the recorded image can be further reduced.

  In addition to the above-mentioned components, the non-aqueous ink can optionally contain a surface tension adjusting agent (penetrating agent), an antifoaming agent, an antioxidant, and the like as appropriate.

  As surface tension modifiers and antifoaming agents, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, or polymer-based, silicone-based, and fluorine-based surfactants Can be used. Specifically, the thing similar to an above-mentioned post-processing agent can be mentioned.

  As the antioxidant, for example, dibutylhydroxytoluene, propyl gallate, tocopherol, butylhydroxyanisole, nordihydroguaiaretic acid and the like can be used, and these may be used alone or in combination of two or more. Good.

  The non-aqueous ink can be prepared by mixing the compounding components using any dispersing means such as a ball mill and a bead mill, but is not limited thereto.

  Non-aqueous inks can be preferably used for inkjet recording apparatuses. The viscosity of the ink when used as an inkjet ink varies depending on the nozzle diameter of the ejection head, the ejection environment, and the like, but in general, it is preferably 5 to 30 mPa · s at 23 ° C., preferably 5 to 15 mPa · s. It is more preferable that it is 5 to 13 mPa · s. Here, the viscosity represents a value at 10 Pa when the shear stress is increased from 0 Pa at a rate of 0.1 Pa / s at 23 ° C.

  Next, a printing method according to an embodiment of the present invention is a printing method using the above-described ink set, wherein non-aqueous ink is printed on a recording medium, and at least the printing surface is treated with a post-treatment agent. And According to such an ink jet recording method, it is possible to increase the density of the image and reduce the show-through.

  The post-treatment agent may treat a part or the whole of the printing surface, and may treat the non-printing surface together with the printing surface. The post-treatment agent can be appropriately selected from the above treatment methods.

  In the printing method of this embodiment, non-aqueous ink can be printed by an inkjet recording method. As an inkjet recording method, any method such as a piezo method, an electrostatic method, or a thermal method may be used. When an ink jet recording apparatus is used, ink is ejected from an ink jet head based on a digital signal, and the ejected ink droplets are attached to a recording medium. A line head method can also be used as the ink jet recording method, and the line head ink jet recording method enables printing at a high printing speed.

  The time from printing with a non-aqueous ink to processing with a post-treatment agent is preferably short, and usually about 5 seconds or less is preferable. As a result, the inorganic particles in the post-treatment agent to be treated later come into contact with the non-aqueous solvent in the non-aqueous ink in the previously printed non-aqueous ink while the non-aqueous solvent in the ink is in a liquid state on the recording medium. Since the ink is absorbed, it is possible to efficiently prevent the coloring material in the ink from penetrating into the recording medium, to reduce back-through and to obtain a high printing density.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

<Post-treatment agent>
Table 1 shows the pretreatment formulation. Each component was mixed according to the formulation shown in Table 1. The properties of the inorganic particles shown in Table 1 are shown in Table 2. The average particle size shown in Table 2 is measured by a dynamic light scattering method using colloidal silica 1 to 4 and an aqueous alumina dispersion using a dynamic light scattering particle size distribution measuring device “LB500” (manufactured by Horiba, Ltd.). did. The average particle diameter of the colloidal silica 1 to 4 and the aqueous alumina dispersion was a numerical value based on the size of the primary particles. The synthetic amorphous silica was measured by a laser diffraction method using a laser diffraction particle size distribution analyzer “SALD-2000A” (manufactured by Shimadzu Corporation). The average particle size in the synthetic amorphous silica was based on the size of the secondary particles. The lengths of the short axis and the long axis shown in Table 2 were determined using an electron microscope “JSM-5400LV” (manufactured by JEOL Ltd.).

<Ink>
As the non-aqueous black ink, RISOX ink F (non-aqueous ink for inkjet, black pigment, manufactured by Riso Kagaku Kogyo Co., Ltd.) was used.

(Example)
The above non-aqueous black ink is loaded into "ORPHIS X9050" (manufactured by Riso Kagaku Kogyo Co., Ltd., a high-speed color printer which is an ink jet recording apparatus), and a solid image is printed on plain paper (ideal paper thin end, produced by Riso Kagaku Kogyo Co., Ltd.). Printed. The X9050 uses a 300 dpi line-type inkjet head (each nozzle is arranged at an interval of about 85 μm) and conveys the paper in the sub-scanning direction orthogonal to the main scanning direction (the direction in which the nozzles are arranged) for printing. It is a system to do.

Immediately after printing (after about 0.5 to 5 seconds), the coating amount of each of the post-treatment agents on the printed surface was 12 g / m ² using a bar coater (in Examples 1-4 and 6 in terms of solid content, 2. 16 g / m ² , and 1.6 g / m ^{2 in} Example 5 was applied.

(Comparative example)
As Comparative Example 1, a non-aqueous black ink printed in the same manner as in the above-described example, but not treated with a post-treatment agent was prepared.

<Evaluation>
The penetration and print density of each example and comparative example were evaluated, and the results are shown in Table 3.

(Betrayal)
After leaving the obtained printed matter for 3 days, the printing density (backside OD value) of the non-printed side (backside) of the printed matter was measured with a Macbeth densitometer (RD920 from Macbeth). Moreover, the back surface OD value was relatively evaluated. The evaluation criteria are as follows.
AA: Back surface OD value is less than 0.56 A: Back surface OD value is 0.56 or more and less than 0.61 B: Back surface OD value is 0.61 or more and less than 0.66 C: Back surface OD value is 0.66 or more

(Print density)
After the obtained printed matter was allowed to stand for 3 days, the printing density (surface OD value) of the printed surface (front surface) of the printed matter was measured with a Macbeth densitometer (RD920 manufactured by Macbeth). Moreover, the surface OD value was relatively evaluated. The evaluation criteria are as follows.
AA: Surface OD value is 1.18 or more A: Surface OD value is 1.13 or more and less than 1.18 B: Surface OD value is 1.08 or more and less than 1.13 C: Surface OD value is less than 1.08

  As shown in Table 3, the combination of the ink sets of each example reduced the show-through and achieved a high printing density as compared with the comparative example that was not treated with the post-treatment agent.

  In Examples 1 and 2, the average particle diameter of the inorganic particles was in a more preferable range, and the back-through could be further reduced. In Example 2, the average particle diameter of the inorganic particles was smaller than that in Example 1, and the particle shape was chain-like, and a higher printing density could be obtained along with the reduction of the back-through. Further, in Example 5, the particle shape was rod-like, and a higher printing density could be obtained with the reduction of the back-through.

Claims (6)

  A post-treatment agent for non-aqueous ink containing inorganic particles containing silica and / or alumina and water.   The post-treatment agent for non-aqueous ink according to claim 1, wherein the silica has an average particle diameter of 30 nm to 150 nm.   The post-treatment agent for non-aqueous ink according to claim 1, wherein the silica has a minor axis of 3 nm or more and less than 30 nm and a major axis of 30 nm or more and 500 nm or less.   The post-treatment agent for non-aqueous ink according to any one of claims 1 to 3, wherein the alumina has a minor axis of 3 nm or more and less than 50 nm and a major axis of 50 nm or more and 100 nm or less. A non-aqueous ink containing a coloring material and a non-aqueous solvent;
The ink set which is a combination with the post-processing agent for non-aqueous inks of any one of Claim 1 to 4. A printing method using the ink set according to claim 5,
A printing method in which a non-aqueous ink is printed on a recording medium, and at least the printing surface is treated with a post-treatment agent for non-aqueous ink.