JP2008075044A - Nonaqueous inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous inkjet ink that has excellent printability (scratch resistance and image transparency) to polyvinyl chloride, has not any problem of odor and does not deteriorate dispersion stability even upon use for a long period of time, and thus can be used stably. <P>SOLUTION: This nonaqueous inkjet ink comprises at least a pigment, a fixing resin and a solvent, wherein a dispersing mean particle diameter of the pigment is ≥50 nm and <200 nm, the fixing resin is a vinyl chloride-vinyl acetate copolymer, and the solvent has relative permittivily of ≥40 and no hydroxy group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel non-aqueous inkjet ink.

  In recent years, the inkjet recording method can be easily and inexpensively created images, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. Ink jet inks used in such an ink jet recording method include water-based inks mainly containing water, oil-based inks mainly containing non-volatile solvents, non-aqueous inks mainly containing volatile solvents, and room temperature. There are a plurality of inkjet inks, such as a hot melt ink that heats and melts solid ink for printing, and an actinic ray curable ink that is cured by actinic rays such as light after printing.

  On the other hand, recording media made of soft polyvinyl chloride are used in a wide range of fields such as outdoor postings that require long-term weather resistance and printed materials that require adhesion to curved objects. There are many methods for printing on soft polyvinyl chloride, but there is an inkjet recording method as a method suitable for the production of a small variety of products because there is no need to prepare a plate and the time to finish is short.

  When ink jet recording is performed on soft polyvinyl chloride, as an ink jet ink to be used, a non-aqueous ink containing a large amount of cyclohexanone or the like has been conventionally used. For example, an ink jet ink containing cyclohexanone is disclosed ( For example, see Patent Document 1.) This cyclohexanone has a high solubility in soft polyvinyl chloride, and since the pigment in the ink-jet ink enters into the soft polyvinyl chloride, good scratch resistance and glossiness can be obtained. However, cyclohexanone has a strong odor and has a problem that requires a local exhaust device when handling inkjet ink.

  On the other hand, non-aqueous inks characterized by not containing cyclohexanone have been developed and sold. For example, a non-aqueous ink containing a solvent such as N-methylpyrrolidone or γ-butyrolactone is disclosed as a solvent for dissolving polyvinyl chloride instead of cyclohexanone having the above-described problems (for example, (See Patent Documents 2 and 3.) Further, for the purpose of improving image fastness such as scratch resistance, a non-aqueous ink to which a fixing resin such as vinyl chloride-vinyl acetate copolymer or acrylic is added is disclosed (for example, see Patent Documents 2 to 5). .) As the fixing resin, a vinyl chloride-vinyl acetate copolymer is particularly frequently used because of its good affinity with polyvinyl chloride. With these configurations, it is possible to obtain an ink-jet ink that can suppress odor to some extent and can form an image having scratch resistance against polyvinyl chloride.

  On the other hand, since the pigment used preferably has a small pigment particle size in order to obtain a clearer image, the particle size is reduced by dispersion. For dispersing the pigment, a polymer dispersant is used (for example, see Patent Documents 2 to 5). When a vinyl chloride-vinyl acetate copolymer is added to the pigment dispersion, the dispersion average particle diameter of the pigment is 200 nm. If it is less than this, the dispersion stability tends to be lowered.

Therefore, the present situation is that a non-aqueous ink jet ink that has no environmental safety and odor problems, has sufficient suitability when printed on polyvinyl chloride, and has good dispersion stability has not yet been obtained.
Japanese translation of PCT publication No. 2002-526631 JP 2005-15672 A Japanese Patent Laid-Open No. 2005-60716 JP 2005-36199 A WO2004 / 007626 pamphlet

  The present invention has been made in view of the above-described problems, and its purpose is to provide excellent printability (scratch resistance, image transparency) for polyvinyl chloride, good odor resistance, and long-term use. Another object of the present invention is to provide a non-aqueous inkjet ink that can be used stably without lowering the dispersion stability.

  The above object of the present invention is achieved by the following configurations.

  1. It contains at least a pigment, a fixing resin and a solvent, and the dispersion average particle size of the pigment is 50 nm or more and less than 200 nm, the fixing resin is a vinyl chloride-vinyl acetate copolymer, and the solvent has a relative dielectric constant of 40. A non-aqueous ink-jet ink characterized by being free of hydroxyl groups.

  2. 2. The non-aqueous inkjet ink according to 1 above, wherein the vinyl chloride-vinyl acetate copolymer is a vinyl chloride-vinyl acetate-maleic anhydride copolymer.

  According to the present invention, it has excellent printability for polyvinyl chloride (scratch resistance, image transparency), good odor resistance, and can be used stably without deterioration of dispersion stability even in long-term use. A water-based inkjet ink could be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor of the present invention contains at least a pigment, a fixing resin, and a solvent, and the dispersion average particle size of the pigment is 50 nm or more and less than 200 nm. It is a vinyl acetate copolymer, and its solvent has a relative dielectric constant of 40 or more and does not contain a hydroxyl group. It has been found that a non-aqueous ink-jet ink that can be used stably for a long period of time without deterioration in dispersion stability can be realized.

  That is, as a result of various studies on non-aqueous ink-jet inks, the present inventor has conventionally used a vinyl chloride-vinyl acetate copolymer as a fixing resin and contains a solvent such as N-methylpyrrolidone or γ-butyrolactone. In the non-aqueous ink-jet inks described above, when the dispersion average particle size of the pigment is less than 200 nm, as one of the factors that degrade the dispersion stability, the above solvent does not sufficiently dissolve the vinyl chloride-vinyl acetate copolymer. As a result, it is estimated that the dispersion stability is adversely affected.

  On the other hand, the present inventors have studied various solvents and combinations thereof in view of the above problems. As a result, by using a solvent having a relative dielectric constant of 40 or more and not containing a hydroxyl group, vinyl chloride-vinyl acetate is obtained. It has been found that the solubility of the copolymer is improved and sufficient dispersion stability of the pigment particles can be realized.

  Hereinafter, the configuration of the non-aqueous inkjet ink of the present invention will be specifically described.

  The non-aqueous inkjet ink of the present invention (hereinafter also referred to as inkjet ink or ink) is characterized by containing a solvent having a relative dielectric constant of 40 or more and not containing a hydroxyl group, more preferably a dielectric constant of 40 or more. The solvent does not contain a hydroxyl group and has a sulfur atom in the structure.

  Examples of the solvent according to the present invention having the above characteristics include sulfolane (dielectric constant 43), dimethyl sulfoxide (dielectric constant 49), and the like, and other solvents having a dielectric constant of 40 or more and no hydroxyl group. Any may be used. In the ink of the present invention, the relative dielectric constant according to the present invention is preferably 40 or more and the amount of the solvent not containing a hydroxyl group is preferably 3% by mass or more and 30% by mass or less in the ink.

  The relative dielectric constant referred to in the present invention is a relative dielectric constant with respect to vacuum, and can be measured with a commercially available measuring device such as a dielectric constant measuring device HP E5050A HEWRET PACKARD according to ASTM-150. The values are described in “Chemical Handbook 4th revised edition (II)” Maruzen Co., Ltd., “Solvent Handbook 1st edition” (Kodansha Scientific), etc., which can be referred to.

  In addition, known solvents can be used in combination as long as the object and effects of the present invention are not impaired. Examples of these solvents include diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and tripropylene. Alkylene glycol monoalkyl ethers such as glycol monomethyl ether, alkylene glycol dialkyl ethers such as ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol diethyl ether, tetraethylene glycol dimethyl ether, and alkylene glycol acetates such as diethylene glycol acetate , Ethylene glycol diacetate, propylene Alkylene glycol diacetate such as recall diacetate, ethylene glycol monobutyl ether acetate, alkylene glycol monoalkyl ether acetates such as propylene glycol monomethyl ether acetate are preferable. These solvents have a property of swelling polyvinyl chloride as compared with glycols, polyols, and glycerin, and even if they are contained in the ink, they hardly affect the drying property. Among these, a solvent selected from diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, ethylene glycol diacetate, and propylene glycol diacetate is preferable, and the quick drying property of the ink when printed on polyvinyl chloride is further improved. Can be made.

  One feature of the ink of the present invention is that a vinyl chloride-vinyl acetate copolymer is used as the fixing resin. For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer Examples thereof include vinyl chloride, vinyl acetate-vinyl alcohol copolymer, and vinyl chloride-vinyl acetate-hydroxyalkyl acrylate copolymer. A preferred number average molecular weight is in the range of 10,000 to 30,000.

  Among these vinyl chloride-vinyl acetate copolymers, it is particularly preferable to use a vinyl chloride-vinyl acetate-maleic anhydride copolymer from the viewpoint of further improving the dispersion stability of the pigment particles.

  As a synthesis method of the vinyl chloride-vinyl acetate copolymer according to the present invention, suspension polymerization method, emulsion polymerization method, solution polymerization method and the like can be applied without particular limitation. However, it is preferable from the viewpoint that the object effect of the present invention can be further exhibited.

  The solution polymerization method referred to in the present invention is one of the methods used for radical polymerization of a monomer having a vinyl group. The monomer and initiator are dissolved in a solvent in which the polymer to be produced is soluble, and heated. This is a method of performing polymerization. Vinyl chloride-vinyl acetate copolymer synthesized by the solution polymerization method has high solubility even at a relatively high molecular weight, and can contain more resin in the ink, thus improving scratch resistance. Can be made.

  The content of the vinyl chloride-vinyl acetate copolymer in the ink of the present invention is preferably 1 to 10% by mass. When the content is 1% by mass or more, the image weather resistance when recorded on polyvinyl chloride is enhanced, and when the content is 10% by mass or less, the ejection stability of ink from the inkjet head is improved. A more preferable content is in the range of 3 to 7% by mass.

  As the pigment applicable in the present invention, conventionally known pigments can be used without particular limitation. For example, organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as carbon black can be preferably used.

  The insoluble pigment is not particularly limited, for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 12, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48 (Ca), C.I. I. Pigment red 48 (Mn), C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57 (Ca), C.I. I. Pigment red 57: 1, C.I. I. Pigment red 112, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 168, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 184, C.I. I. Pigment red 202, C.I. I. Pigment red 209, C.I. I. Pigment red 222, C.I. I. Pigment red 254, C.I. I. Pigment violet 19 and the like.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 130, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 147, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 185, C.I. I. Pigment yellow 213, C.I. I. And CI Pigment Yellow 214.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 1, C.I. I. Pigment blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 22, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

In addition to the above, when red, green, blue and intermediate colors are required, it is preferable to use the following pigments alone or in combination. I. Pigment Red 209, 224, 177, 194,
C. I. Pigment Orange 43,
C. I. Vat Violet 3,
C. I. Pigment Violet 19, 23, 37,
C. I. Pigment Green 7, 36,
C. I. Pigment Blue 15: 6,
Etc. are used.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The content of these pigments in the ink of the present invention is preferably 2 to 10% by mass. In addition, light color ink may be used for the purpose of reducing image graininess. In this case, the pigment content is preferably 1/5 to 1/2 with respect to the dark color ink.

  One of the characteristics of the average particle diameter of the pigment particles in the pigment dispersion used in the ink according to the present invention is 50 nm or more and less than 200 nm, and more preferably 60 nm or more and less than 150 nm. The average particle diameter of the pigment particles in the pigment dispersion referred to in the present invention can be measured by a photon correlation method and determined by a cumulant method. For example, the average particle size can be calculated by a cumulant method using a Zetasizer Nano manufactured by Malvern.

  As the pigment dispersant used for the preparation of the pigment dispersion, a surfactant, a polymer dispersant and the like are used, and among these, a polymer dispersant is preferable. Examples of the polymer dispersant include (meth) acrylic resin, styrene- (meth) acrylic resin, hydroxyl group-containing carboxylic acid ester, salt of long-chain polyaminoamide and high molecular weight acid ester, and salt of high molecular weight polycarboxylic acid. , Salt of long-chain polyaminoamide and polar acid ester, high molecular weight unsaturated acid ester, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalenesulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate Examples thereof include salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, stearylamine acetate, and pigment derivatives.

  Specifically, Jonkrill (manufactured by Johnson Polymer), Anti-Terra-U (manufactured by BYK Chemie), Disperbyk (manufactured by BYK Chemie), Efka (manufactured by Efka CHEMICALS), Floren (manufactured by Kyoeisha Chemical), Disparon (manufactured by Enomoto Kasei Co., Ltd.), Azisper (manufactured by Ajinomoto Fine-Techno Co., Ltd.), Demole (manufactured by Kao Corporation), Homogenol, Emulgen (manufactured by Kao Corporation), Solspurs (manufactured by Avicia), Nikkor (manufactured by Nikko Chemical Co., Ltd.), etc. Is mentioned.

  The content of the pigment dispersant in the inkjet ink of the present invention is preferably 10 to 200% by mass with respect to the pigment. By setting the content to 10% by mass or more, the pigment dispersion stability is enhanced, and by setting the content to 200% by mass or less, the ink ejection from the inkjet head is easily stabilized.

  In addition to the above description, the inkjet ink of the present invention is publicly known depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Various additives such as a viscosity modifier, a specific resistance modifier, a film forming agent, an ultraviolet absorber, an antioxidant, a discoloration inhibitor, an antifungal agent, and a rust inhibitor can be appropriately selected and used.

  The ink-jet head used when forming an image by discharging the ink-jet ink of the present invention may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, thermal ink jet) Any ejection method such as a mold, a bubble jet (registered trademark) mold, or the like may be used.

  In the ink jet recording method using the ink jet ink of the present invention, for example, an ink jet recorded image is obtained by ejecting ink from an ink jet head based on a digital signal and adhering it to a recording medium by a printer loaded with the ink jet ink. . In order to quickly and surely dry the ink adhered to the recording medium, a method of forming an image by increasing the surface temperature of the recording medium is preferable.

  The surface temperature is adjusted according to the durability of the recording medium and the drying property of the ink used, but is preferably 40 to 100 ° C. In particular, when polyvinyl chloride is used as the recording medium, increasing the surface temperature improves the wettability of the ink with respect to the surface of the recording medium. Therefore, it is more preferable to record at a higher surface temperature.

  Depending on the brand of the recording medium made of polyvinyl chloride, there may be a difference in wettability and ink drying, so the surface temperature may be adjusted according to the characteristics of each medium.

  When recording is performed by increasing the surface temperature of the recording medium, it is preferable to mount a heater on the ink jet recording apparatus, and by heating the recording medium before or during transport of the recording medium, the surface temperature of the recording medium alone by the ink jet recording apparatus Can be adjusted.

  In the present invention, by using polyvinyl chloride as a recording medium used in the inkjet recording method, the excellent characteristics of the inkjet ink of the present invention can be exhibited. Specific examples of the recording medium made of polyvinyl chloride include SOL-371G, SOL-373M, SOL-4701 (manufactured by Big Technos Co., Ltd.), glossy vinyl chloride (manufactured by Systemgraph Co., Ltd.), KSM-VS, KSM. -VST, KSM-VT (above, manufactured by Kimoto Co., Ltd.), J-CAL-HGX, J-CAL-YHG, J-CAL-WWWG (above, manufactured by Kyo Show Osaka Co., Ltd.), BUS MARK V400 F vinyl, LITEcal V-600F vinyl (above, manufactured by Flexcon), FR2 (manufactured by Hanwha), LLBAU13713, LLSP20133 (above, manufactured by Sakurai Co., Ltd.), P-370B, P-400M (above, manufactured by Kambo Plus Co., Ltd.), S02P, S12P, S13P, S14P, S22P, S24P, 34P, S27P (manufactured by Grafityp), P-223RW, P-224RW, P-249ZW, P-284ZC (manufactured by Lintec Corporation), LKG-19, LPA-70, LPE-248, LPM-45 LTG-11, LTG-21 (manufactured by Shinsei Co., Ltd.), MPI 3023 (manufactured by Toyo Corporation), Napoleon Gloss PVC (manufactured by Futaki Electronics Co., Ltd.), JV-610, Y-114 ( As described above, manufactured by ICC Corporation), NIJ-CAPVC, NIJ-SPVCGT (hereinafter, manufactured by Nichie Corporation), 3101 / H12 / P4, 3104 / H12 / P4, 3104 / H12 / P4S, 9800 / H12 / P4, 3100 / H12 / R2, 3101 / H12 / R2, 3104 / H12 / R 2, 1445 / H14 / P3, 1438 / One Way Vision (manufactured by Inetrcoat), JT5129PM, JT5728P, JT5822P, JT5829P, JT5829R, JT5829PM, JT5829RM, JT5929PM (above, manufactured by Mactac, MP1100, MP1100 MPI2001, MPI2002, MPI3000, MPI3021, MPI3500, MPI3501 (above, manufactured by Avery), AM-101G, AM-501G (above, manufactured by Ginichi Co., Ltd.), FR2 (manufactured by Hanwha Japan Co., Ltd.), AY-15P, AY-60P, AY-80P, DBSP137GGH, DBSP137GGL (above, manufactured by Insight Inc.), SJT-V200F, SJ T-V400F-1 (above, manufactured by Hiraoka Oryome Co., Ltd.), SPS-98, SPSM-98, SPSH-98, SVGL-137, SVGS-137, MD3-200, MD3-301M, MD5-100, MD5- 101M, MD5-105 (manufactured by Metamark), 640M, 641G, 641M, 3105M, 3105SG, 3162G, 3164G, 3164M, 3164XG, 3164XM, 3165G, 3165SG, 3165M, 3169M, 3451SG, 3551G, 3551M, 3631, 3641M , 3651G, 3651M, 3651SG, 3951G, 3641M (above, manufactured by Orafol), SVTL-HQ130 (manufactured by Lamy Corporation), SP300 GWF, SPCLEARAD vinyl l (above, manufactured by Catalina), RM-SJR (produced by Ryoyo Shoji Co., Ltd.), Hi Lucky, New Lucky PVC (above, produced by LG), SIY-110, SIY-310, SIY-320 (above, Sekisui Chemical) Industrial Co., Ltd.), PRINT MI Frontlit, PRINT XL Lightweight banner (above, manufactured by Endutex), RIJET 100, RIJET 145, RIJET165 (above, manufactured by Ritrama), NM-SG, NM-SM Co., Ltd. Manufactured), LTO3GS (manufactured by Lucio Co., Ltd.), easy print 80, performance print 80 (manufactured by Jetgraph Co., Ltd.), DSE 550, DSB 550, DSE 800G, DSE 802/137, V250WG, 300WG, V350WG (manufactured by Hexis Ltd.), Digital White 6005PE, 6010PE (or, Multifix Co., Ltd.).

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

<Preparation of inkjet ink>
[Preparation of Ink 1]
<Preparation of pigment dispersion>
C. I. 10 parts of Pigment Blue 15: 3 (hereinafter abbreviated as PB15: 3), 5 parts of Solspers 20000 (manufactured by IC Japan) as a pigment dispersant, 10 parts of sulfolane as a solvent, diethylene glycol diethyl Disperse using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 60 parts of ether and 15 parts of ethylene glycol diacetate and filled with zirconia beads having a diameter of 0.5 mm by volume. 1 was obtained.

<Preparation of resin solution>
10 parts of sulfolane, 65 parts of diethylene glycol diethyl ether and 15 parts of ethylene glycol diacetate, 10 parts of vinyl chloride-vinyl acetate copolymer (trade name VYHD, manufactured by Dow Chemicals) as a fixing resin are mixed and dissolved. Thus, a resin solution 1 was prepared.

<Preparation of ink>
While stirring 50 parts of the resin solution 1, 50 parts of the pigment dispersion 1 was mixed and then filtered through a 0.8 μm filter to obtain ink 1. The average particle diameter (cumulant method) of the pigment particles determined by Zetasizer Nano (Malvern) was 100 nm.

[Preparation of inks 2 to 16]
Inks 1 to 16 were prepared in the same manner as in the preparation of the ink 1, except that the pigment type, pigment average particle size, fixing resin type, solvent type and addition amount were changed as shown in Table 1.

  In addition, the detail of each additive described with the abbreviation in Table 1 is as follows.

<Pigment>
PR122: C.I. I. Pigment Red 122
PY150: C.I. I. Pigment Yellow 150
PB15: 3; C.I. I. Pigment Blue 15: 3
PBr7: C.I. I. Pigment Black 7
<Fixing resin>
PVC1: Vinyl chloride-vinyl acetate copolymer VYHD (manufactured by Dow Chemical Company)
PVC2: Vinyl chloride-vinyl acetate-maleic anhydride copolymer VMCA (manufactured by Dow Chemical Company)
<Solvent and relative dielectric constant>
Sulfolane: relative dielectric constant = 43
DMSO: Dimethylsulfoxide Relative permittivity = 49
NMP: N-methylpyrrolidone Relative permittivity = 32
γ-BL: γ-butyrolactone relative permittivity = 39
Glycerin: relative dielectric constant = 43 containing hydroxyl group <other solvents>
DEGDEE: Diethylene glycol diethyl ether EGDAc: Ethylene glycol diacetate

<Evaluation of formed image>
[Image formation]
A piezo-type head having a nozzle diameter of 28 μm, a driving frequency of 15 kHz, a nozzle number of 512, a minimum liquid amount of 14 pl, and a nozzle density of 180 dpi (dpi in the present invention represents the number of dots per 2.54 cm) is mounted, and the maximum recording density Each ink was loaded into an on-demand type ink jet printer equipped with a heater of 1440 × 1440 dpi. Next, each ink was ejected, and a solid image of 10 cm × 10 cm was recorded on JT5929PM (manufactured by Mactac) which is a recording medium made of polyvinyl chloride. During printing, the recording medium was heated from the back side, and the heater temperature was set so that the surface temperature of the recording medium during image recording was 45 ° C. The surface temperature of the recording medium was measured using a non-contact thermometer (IT-530N type, manufactured by Horiba, Ltd.).

[Evaluation of ink and formed image]
According to the above method, each ink and each image created from each ink were evaluated according to the following method. In all cases, the performance of Δ or higher was regarded as an acceptable level.

<Evaluation of scratch resistance>
The formed image surface was rubbed with dry cotton, and scratch resistance was evaluated according to the following criteria.

A: Image hardly changes even after rubbing 51 times or more ○: Slight scratch remains at the stage of rubbing 50 times, but hardly affects the image density Δ: Image density decreases during rubbing 20 to 49 times × : Image density decreases during rubbing 1 to 19 times <Evaluation of transparency>
The degree of transparency of the formed solid image was visually observed, and the transparency was evaluated according to the following criteria.

◎: Transparency of the formed image is extremely high ○: Transparency of the formed image is high △: Transparency of the formed image is slightly high ×: The formed image is poor in transparency <Evaluation of odor resistance>
One day after the solid image creation, the odor evaluation by 10 subjects was performed, and the score was given in 5 stages, with 5 points when judged as almost odorless and 1 point when judged as very unpleasant odor. Odor resistance was evaluated according to standards.

A: The average score of 10 subjects is 4.0 points or more. ○: The average score of 10 subjects is 3.0 points or more and less than 4.0 points. Δ: The average score of 10 subjects is 2.0 or more and less than 3.0 ×: The average score of 10 subjects is less than 2.0 <Evaluation of dispersion stability>
Each ink prepared above was stored in a thermostat at 70 ° C. for 3 months, and then the average particle diameter change rate of the pigment particles was determined according to the following formula, and the dispersion stability was evaluated according to the following criteria.

Average particle diameter change rate (%) of pigment particles = {(average particle diameter of pigment particles after storage−average particle diameter of pigment particles before storage) / average particle diameter of pigment particles before storage} × 100
◎: Average particle size change rate after storage was less than 5% ○: Average particle size change rate after storage was 5% or more and less than 10% △: Average particle size change rate after storage Was 10% or more and less than 20%. X: The average particle size change rate after storage was 20% or more. Table 2 shows the results obtained as described above.

  As is apparent from the results shown in Table 2, the ink having the constitution defined in the present invention is superior in dispersion stability of pigment particles even when stored at a high temperature for a long period of time, compared to the comparative example. It can be seen that the image recorded on the recording medium made of vinyl chloride is excellent in scratch resistance, transparency and odor resistance.

Claims (2)

It contains at least a pigment, a fixing resin and a solvent, and the dispersion average particle size of the pigment is 50 nm or more and less than 200 nm, the fixing resin is a vinyl chloride-vinyl acetate copolymer, and the solvent has a relative dielectric constant of 40. A non-aqueous ink-jet ink characterized by being free of hydroxyl groups. The non-water-based inkjet ink according to claim 1, wherein the vinyl chloride-vinyl acetate copolymer is a vinyl chloride-vinyl acetate-maleic anhydride copolymer.