JP4345492B2 - Inkjet recording method - Google Patents

Description

  The present invention relates to a novel ink jet recording method using an active energy ray curable ink.

  Conventionally, water-soluble liquid ink (water-based ink) has been widely used as ink for inkjet recording. Also, a hot melt ink that is made from a hot-melt ink made of solid wax or the like at room temperature, is liquefied by heating, sprayed with some energy, is cooled and solidified while adhering to the recording medium, and forms recording dots A melt type ink jet recording system has been proposed.

  Since this ink is solid at room temperature, it is not soiled during handling, and the amount of ink evaporation at the time of melting can be minimized, so that the nozzles are not clogged. Further, since it solidifies immediately after adhering to the recording medium, there is no “bleeding”, and there is an advantage that various types of recording media such as Japanese paper, drawing paper, postcards, and plastic sheets can be used without pretreatment.

  On the other hand, US Pat. Nos. 4,391,369 and 4,484,948 disclose inks that provide good print quality regardless of paper quality. JP-A-56-93776 discloses an ultraviolet curable resin ink having good adhesion to a metal surface. Further, as an ink for ink jet recording that is cured by exposure to ultraviolet rays, for example, U.S. Pat. No. 4,228,438 discloses an ink using an epoxy-modified acrylic resin and a urethane-modified acrylic resin as a binder, and a pigment having a particle size of 5 microns or less as a coloring component, Japanese Patent Laid-Open No. 58-32694 discloses an ink using a cationic polymerizable epoxy resin as a binder, and Japanese Patent Laid-Open No. 5-186725 uses a water-soluble or water-insoluble dye. However, inks that facilitate printing on plain paper and recycled paper are disclosed.

  As described above, there has been a demand for the appearance of an inkjet recording method capable of performing high-definition printing with photographic image quality on various recording media such as a plastic sheet without requiring inkjet dedicated paper or the like.

  However, when the above-mentioned water-soluble liquid ink is used for printing, it is difficult to print on a recording medium that does not absorb ink, and a large-sized ink drying device is required even when dedicated paper is used. In addition, due to the problem of bleeding, high-definition printing is difficult and resolution is limited, so that its use is limited at present.

  Even hot melt type inks using the above wax can be printed on non-absorbent recording media that do not absorb ink, and high-speed printing is possible. There is a problem that it is difficult to obtain high reliability and the smoothness is inferior.

  On the other hand, the ink jet recording method using an organic pigment as a colorant has many advantages over the ink jet recording method using a dye particularly in terms of weather resistance, and therefore, it is an OA device, a general household printer, a facsimile. Applications are not limited to office printers, etc., but are expected to be applied to indoor and outdoor posters, large signs, cars, glass, elevators, wall and building decorations, and prints on fabrics.

  In addition, an ink jet recording method using an active energy ray-curable ink that cures ink with an active energy ray such as ultraviolet rays can print on a recording medium having no ink absorbability. However, in the inkjet recording method that uses pigments and is substantially free of water and organic solvents and cures the ink liquid with active energy rays such as ultraviolet rays, high-definition printing with controlled dot diameter is formed. There has been little disclosure or suggestion on how to do this. In high-definition printing, it is important that the formed dot diameter is controlled to be small and that there is no blur and the contour is clear. When using a recording medium having high ink absorbability such as ink jet dedicated paper, the formed dot diameter can be adjusted by the amount of ink droplets, but it is difficult to adjust the bleeding alone. In addition, when printing on a non-ink-absorbing recording medium using the inkjet recording method, it is difficult to control the dot diameter only by the amount of ink droplets, especially the dot diameter formed from small droplets. Controlling this is a more difficult task.

  Furthermore, when an image is formed using a plurality of inks as in color printing, it is essential for high-definition printing that there is no difference in the shape of the dots formed by each ink.

In order to control the above-described dot shape, it is effective to adjust the surface tension of the ink. For example, a method for defining the surface tension of the ink as 25 to 35 mN / m has been proposed (for example, Patent Document 1). reference.). However, simply defining the surface tension of the ink as described above is not sufficient for high-definition printing, and further technical improvements are required.
WO99 / 29788 pamphlet (Claims)

  The present invention has been made in view of the above problems, and an object thereof is to provide an ink jet recording method capable of obtaining a high-definition image excellent in bleeding resistance, density uniformity and smoothness of a formed image.

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

〔式中、Ｒ ^１ は水素原子、炭素数１〜６のアルキル基、フルオロアルキル基、アリル基、アリール基、フリル基またはチエニル基である。〕 (Claim 1)
An ink containing a curable, cationic polymerizable component in the active energy ray, ejection to a recording medium from an inkjet recording head, after having landed, the ink jet recording method for forming an image by curing with an active energy ray, the The ink contains a compound represented by the following general formula (7) as the cationic polymerizable component, and the recording medium is selected from a polyethylene terephthalate film, a stretched polystyrene film, a stretched polypropylene film, a stretched nylon film, and a polyvinyl chloride film. The surface tension value (AmN / m) of the recording medium is 35 mN / m or more and 60 mN / m or less, and the surface tension value (BmN / m) of the ink cured by irradiation with the active energy ray There 30 mN / m or more and less 50 mN / m, and the table Ink jet recording method is characterized in that it is a 0~20mN / m absolute value of the difference between the tension value (AmN / m) surface tension values (BmN / m) (| | A-B).

[Wherein, R ¹ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group, an allyl group, an aryl group, a furyl group, or a thienyl group. ]

(Claim 2)
The inkjet recording method according to claim 1, wherein R ¹ in the general formula (7) is an alkyl group having 1 to 6 carbon atoms.
(Claim 3)
The inkjet recording method according to claim 1, wherein the recording medium is a polyethylene terephthalate film, a stretched polystyrene film, or a stretched polypropylene film.

(Claim 4 )
The surface tension value (BmN / m) of the ink cured by the irradiation of the active energy ray does not substantially change after 50% of the irradiation energy required for curing the ink is irradiated. Item 4. The inkjet recording method according to any one of Items 1 to 3 .

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording method from which the high-definition image excellent in the bleeding tolerance of the formed image, density uniformity, and smoothness is obtained can be provided.

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

The present inventor has proceeded with extensive study in view of the above problems, an in-click containing curable cationically polymerizable components in the active energy ray, ejection to a recording medium from an inkjet recording head, after having landed, the active energy In the ink jet recording method of forming an image by irradiating and curing a line, the ink contains a compound represented by the following general formula (7) as the cationic polymerizable component, and the recording medium is a polyethylene terephthalate film , A stretched polystyrene film, a stretched polypropylene film, a stretched nylon film, and a polyvinyl chloride film, and the surface tension value (AmN / m) of the recording medium is 35 mN / m or more and 60 mN / m or less, The surface tension value (BmN / m) of the ink cured by irradiation with active energy rays is 0 mN / m or more and less 50 mN / m, and the absolute value of the difference between the surface tension values (AmN / m) surface tension values (BmN / m) (| A -B |) is 0~20mN / m By forming an image under the following conditions, it has been found that a high-definition image excellent in bleeding resistance, density uniformity and smoothness can be obtained, and the present invention has been achieved.

Furthermore, R ¹ in the general formula (7) is an alkyl group having 1 to 6 carbon atoms, the recording medium is a polyethylene terephthalate film, a stretched polystyrene film or a stretched polypropylene film, or active energy rays. the surface tension value B of the ink cured by irradiation, since it was irradiated with 50% of the irradiation energy required to cure the ink, and more on the child and the conditions that do not substantially change, more are the effects of the present invention It has been found that it can be further demonstrated.

  Details of the present invention will be described below.

  First, the details of the active energy ray-curable ink according to the present invention (hereinafter also simply referred to as the ink according to the present invention) will be described.

  One feature of the active energy ray-curable ink according to the present invention is that it contains a cationically polymerizable component that can be cured with active energy rays.

The present invention is characterized by containing a compound represented by the general formula (7) described later as a cationic curable component (hereinafter also referred to as a cationic curable monomer). with a compound represented by), various known cationically curable monomer can be for 併. For example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, JP-A-2001-220526 Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene thereof. Examples thereof include di- or polyglycidyl ethers of oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-propyl Pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  The ink according to the present invention preferably contains a compound having at least one oxetane ring as a cationic curable monomer.

  The oxetane compound that can be used in the present invention is a compound having an oxetane ring, and any known oxetane compound as described in JP-A Nos. 2001-220526 and 2001-310937 can be used. .

  Further, the combined use of a monofunctional oxetane compound containing one oxetane ring and a polyfunctional oxetane compound containing two or more oxetane rings improves the film strength after curing and the adhesion to a recording medium. preferable. However, if a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, which makes it difficult to handle, and the glass transition temperature of the ink composition becomes high. Sex is not enough. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  Hereinafter, although the specific example of the compound which has an oxetane ring based on this invention is demonstrated, this invention is not limited to these.

  An example of the compound having one oxetane ring is a compound represented by the following general formula (1).

In the general formula (1), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group. , Furyl group or thienyl group. R ² is an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl- C2-C6 alkenyl group such as 2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group, etc. A group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group; Alkoxycarbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl Is N- alkylcarbamoyl group having a carbon number of 2-6 and the like. As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring because the resulting composition has excellent tackiness, low viscosity and excellent workability.

  An example of a compound having two oxetane rings includes a compound represented by the following general formula (2).

In the general formula (2), R ¹ is the same group as that in the general formula (1). R ³ is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, a linear or branched poly (alkyleneoxy) such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. ) Group, propenylene group, methylpropenylene group, butenylene group or other linear or branched unsaturated hydrocarbon group, alkylene group containing carbonyl group or carbonyl group, alkylene group containing carboxyl group, alkylene containing carbamoyl group Group.

Moreover, as R < ³ >, the polyvalent group selected from the group shown by the following general formula (3), (4) and (5) can also be mentioned.

In the general formula (3), R ⁴ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. An alkoxy group having 1 to 4 carbon atoms, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group.

In the general formula (4), R ⁵ represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .

In General formula (5), R < ⁶ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. n is an integer of 0-2000. R ⁷ is a methyl group, an ethyl group, a propyl group, a butyl group having 1 to 4 carbon atoms, or an aryl group. R ⁷ may further include a group selected from the group represented by the following general formula (6).

In General formula (6), R < ⁸ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. m is an integer of 0-100.

  Specific examples of the compound having two oxetane rings include the following compounds.

Illustrative compound 1 is a compound in which R ¹ is an ethyl group and R ³ is a carboxyl group in the general formula (2). Exemplary compound 2 is a compound in which, in the general formula (2), R ¹ is an ethyl group, R ³ is the general formula (5), R ⁶ and R ⁷ are methyl groups, and n is 1.

In the present invention, a compound represented by the following general formula (7) is used as a compound having two oxetane rings. In general formula (7), ^{R 1} has the same meaning as ^{R 1} in the general formula (1).

  An example of a compound having 3 to 4 oxetane rings is a compound represented by the following general formula (8).

In the general formula (8), R ¹ is the same meaning as R ¹ in the general formula (1). As R ⁹ , for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by the following A to C, a branched poly (alkyleneoxy) group such as a group represented by the following D, or the following E And branched polysiloxy groups such as those shown. j is 3 or 4.

In A above, R ¹⁰ is a lower alkyl group such as a methyl group, an ethyl group or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Illustrative compound 3 is an example of a compound having 3 to 4 oxetane rings.

  Furthermore, examples of the compound having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (9).

In the general formula (9), R ⁸ has the same meaning as R ⁸ in the general formula (6). R ¹¹ is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

  Preferable specific examples of the oxetane compound used in the present invention include the following compounds.

  The production method of each compound having an oxetane ring described above is not particularly limited, and may be a conventionally known method, for example, Pattison (DB Pattison, J. Am. Chem. Soc., 3455, 79). (1957)) discloses a method for synthesizing an oxetane ring from a diol. In addition to these, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1000 to 5000 are also included. Examples of these specific compounds include the following compounds.

  In the ink according to the present invention, a photoacid generator can be used.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192).

  Examples of the photocationic polymerization initiator include aromatic onium salts. As this aromatic onium salt, a salt of a Group Va element of the periodic table, for example, a phosphonium salt (for example, triphenylphenacylphosphonium hexafluorophosphate), a salt of a Group VIa element, for example, a sulfonium salt (for example, tetra Triphenylsulfonium fluoroborate, triphenylsulfonium hexafluorophosphate, tris (4-thiomethoxyphenyl) hexafluorophosphate, sulfonium and triphenylsulfonium hexafluoroantimonate), and salts of Group VIIa elements, such as And iodonium salts (for example, diphenyliodonium chloride). The use of such an aromatic onium salt as a cationic polymerization initiator in the polymerization of an epoxy compound is described in U.S. Pat. Nos. 4,058,401, 4,069,055, 4,101,513 and No. 4,161,478.

  Preferred photocationic polymerization initiators include sulfonium salts of Group VIa elements. Among these, from the viewpoint of ultraviolet curable properties and storage stability of the ultraviolet curable ink, triarylsulfonium hexafluoroantimonate is preferable. In addition, the photopolymerization initiators described in pages 39 to 56 of the photopolymer handbook (published by Photographic Society Committee, 1989), JP-A 64-13142, JP-A-2-4804 Any compound can be used.

  Specific examples of the compound suitable for the present invention are listed below, but the present invention is not limited thereto.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ and CF ₃ SO ₃ ⁻ salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium and phosphonium are listed. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  The ink according to the present invention preferably contains at least one photoacid generator selected from diazonium having an arylborate compound as a counter ion, an aromatic onium compound of iodonium or sulfonium, and an iron allene complex.

  The ink according to the present invention includes, for the first time, JP-A-8-248561 and JP-A-9-34106, and an acid proliferating agent that newly generates an acid by an acid generated by actinic ray irradiation that has already been known. It is preferable to do. By using an acid multiplication agent, it is possible to further improve discharge stability.

  The ink according to the present invention can contain a thermal base generator for the purpose of improving ejection stability. By containing a thermal base generator, in the ink jet recording in which the printed ink film thickness becomes thicker than that of normal printing, it is possible to remarkably reduce the curl and wrinkles of the recording medium due to ink shrinkage that occurs during ink curing. .

  Examples of the thermal base generator include compounds that release amines by decomposition by reactions such as organic acid and base salts that are decomposed by decarboxylation by heating, intramolecular nucleophilic substitution reaction, Rossen rearrangement, Beckmann rearrangement, etc. Those which cause some kind of reaction by heating and release a base are preferably used. Specifically, the salt of trichloroacetic acid described in British Patent No. 998,949, the salt of alpha-sulfonylacetic acid described in US Pat. No. 4,060,420, and the propionic acids described in JP-A-59-157737 Salts, 2-carboxycarboxamide derivatives, salts with a base component described in JP-A-59-168440 and a thermally decomposable acid using an alkali metal or an alkaline earth metal in addition to an organic base, JP-A-59-180537 Hydroxam carbamates utilizing the Lossen rearrangement described in No. 5, and aldoxime carbamates described in JP-A No. 59-195237 that generate nitriles by heating. In addition, British Patent No. 998,945, US Pat. No. 3,220,846, British Patent No. 279,480, Japanese Patent Laid-Open Nos. 50-22625, 61-32844, 61-51139, 61 The thermal base generators described in Nos. -52638, 61-51140, 61-53634 to 61-53640, 61-55644, 61-55645 and the like are useful. More specifically, guanidine trichloroacetate, methylguanidine trichloroacetate, potassium trichloroacetate, guanidine phenylsulfonylacetate, guanidine p-chlorophenylsulfonylacetate, guanidine p-methanesulfonylphenylsulfonylacetate, potassium phenylpropiolate, phenylpropiool Examples include acid guanidine, cesium phenylpropiolate, guanidine p-chlorophenylpropiolate, guanidine p-phenylene-bis-phenylpropiolate, tetramethylammonium phenylsulfonylacetate, and tetramethylammonium phenylpropiolate. The thermal base generator can be used in a wide range.

  When coloring the ink according to the present invention, a coloring material is added. As the color material, various color materials that can be dissolved or dispersed in the cationically polymerizable component can be used, but a pigment is preferable from the viewpoint of weather resistance.

  As the pigment contained in the ink according to the present invention, an achromatic inorganic pigment such as carbon black, titanium oxide, calcium carbonate, or a chromatic organic pigment can be used. Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red, soluble azo pigments such as lithol red, heliobordeaux, pigment scarlet, and permanent red 2B, alizarin, indanthrone, thio Derivatives from vat dyes such as indigo maroon, phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green, quinacridone organic pigments such as quinacridone red and quinacridone magenta, perylene organic pigments such as perylene red and perylene scarlet, isoindolinone Isoindolinone organic pigments such as yellow and isoindolinone orange, pyranthrone organic pigments such as pyranthrone red and pyranthrone orange, Oindigo organic pigments, condensed azo organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments such as quinophthalone yellow, isoindoline organic pigments such as isoindoline yellow, and other pigments such as flavanthrone yellow and acylamide yellow Nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like.

  When organic pigments are exemplified by color index (CI) numbers, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, C.I. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Pigment brown 23, 25, 26, and the like.

  Among the above pigments, quinacridone organic pigments, phthalocyanine organic pigments, benzimidazolone organic pigments, isoindolinone organic pigments, condensed azo organic pigments, quinophthalone organic pigments, isoindoline organic pigments, etc. are light-resistant. Is preferable because it is excellent. The organic pigment is preferably a fine pigment having an average particle diameter of 10 to 150 nm as measured by laser scattering. When the average particle diameter of the pigment is less than 10 nm, the light resistance is lowered due to the small particle diameter, and when it exceeds 150 nm, it is difficult to maintain stable dispersion, and the pigment is likely to precipitate.

  The organic pigment can be refined by the following method. That is, a mixture comprising at least three components of an organic pigment, a water-soluble inorganic salt of 3 mass times or more of the organic pigment, and a water-soluble solvent is made into a clay-like mixture, which is kneaded strongly with a kneader or the like and then refined. And stirred with a high speed mixer or the like to form a slurry. Next, filtration and washing of the slurry are repeated to remove the water-soluble inorganic salt and the water-soluble solvent. In the miniaturization step, a resin, a pigment dispersant, or the like may be added. Examples of the water-soluble inorganic salt include sodium chloride and potassium chloride. These inorganic salts are used in the range of 3 times by mass or more, preferably 20 times by mass or less of the organic pigment. When the amount of the inorganic salt is less than 3 times by mass, a treated pigment having a desired size cannot be obtained. On the other hand, when the amount is more than 20 times by mass, the cleaning process in the subsequent step is enormous, and the substantial processing amount of the organic pigment is reduced.

  The water-soluble solvent is an organic solvent and a water-soluble inorganic salt that is used as a crushing aid, and is used for efficient crushing efficiently, especially if it is a solvent that dissolves in water. Although not limited, a high boiling point solvent having a boiling point of 120 to 250 ° C. is preferable from the viewpoint of safety because the temperature rises during kneading and the solvent is easily evaporated. Examples of water-soluble solvents include 2- (methoxymethoxy) ethanol, 2-butoxyethanol, 2- (isopentyloxy) ethanol, 2- (hexyloxy) ethanol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Butyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, low Examples thereof include molecular weight polypropylene glycol.

  In the present invention, the pigment is preferably contained in the ink in the range of 3 to 15% by mass in order to obtain a sufficient concentration and sufficient light resistance.

  Examples of the pigment dispersant used for dispersing the pigment include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, Molecular weight unsaturated acid ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphorus Examples include acid esters, polyoxyethylene nonylphenyl ether, stearylamine acetate, and pigment derivatives.

  Specific examples of the pigment dispersant include "Anti-Terra-U (polyaminoamide phosphate)", "Anti-Terra-203 / 204 (high molecular weight polycarboxylate)" manufactured by BYK Chemie, "Disperbyk-101 ( Polyaminoamide phosphate and acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (polymer) Copolymer)), "400", "Bykumen" (high molecular weight unsaturated acid ester), "BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid)", "P104S, 240S (high molecular weight unsaturated acid) Polycarboxylic acid and silicon system "," Lactimon (long chain amine and unsaturated acid polycarl) Phosphate and silicon) ", and the like.

  Also, “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified polyacrylate), 150 (aliphatic) System modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine system) ", Kyoei Chemical Co., Ltd." Floren TG-710 (urethane oligomer) "," “Flonon SH-290, SP-1000”, “Polyflow No. 50E, No. 300 (acrylic copolymer)”, “Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150, manufactured by Enomoto Kasei Co., Ltd. (Aliphatic polyvalent carboxylic acid), # 7004 (polyether ester type) " That.

  Furthermore, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18 (Polyethylene)” manufactured by Kao Corporation Carboxylic acid type polymer) "," Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonyl phenyl ether) "," Acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate) ", General Corporation "Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000", Nikko Chemical's "Nikkor T106 (polyoxyethylene sorbitan monooleate), MYS" IEX (polyoxyethylene monostearate), Hexagline4-0 (hexaglyceryl ruthenate Huwei rate) ", and the like.

  The pigment dispersant is preferably contained in the ink in the range of 0.1 to 10% by mass.

  The ink according to the present invention is produced by well dispersing the pigment together with an active energy ray-curable compound (cationic polymerizable component) and a pigment dispersant using a normal dispersing machine such as a sand mill. It is preferable to prepare a concentrated solution having a high pigment concentration in advance and dilute with an active energy ray-curable compound. Sufficient dispersion is possible even with dispersion by a normal disperser. Therefore, excessive dispersion energy is not required, and a large amount of dispersion time is not required. An ink having excellent properties is prepared. The ink is preferably filtered through a filter having a pore diameter of 3 μm or less, more preferably 1 μm or less.

  In the ink according to the present invention, various additives other than those described above can be used. For example, in order to improve the storage stability of the ink composition, a polymerization inhibitor can be added at 200 to 20000 ppm. Since the UV curable ink is preferably ejected by heating and lowering the viscosity, it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization. In addition, leveling additives, matting agents, polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes for adjusting film physical properties may be added as necessary. I can do it. In order to improve the adhesion with the recording medium, it is also effective to add a trace amount of organic solvent. In this case, it is effective to add in the range where the solvent resistance and VOC problems do not occur, and the amount used is in the range of 0.1 to 5%, preferably 0.1 to 3%. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In the ink according to the present invention configured as described above, the absolute difference between the surface tension value (AmN / m) of the recording medium and the surface tension value (BmN / m) of the ink cured by irradiation with the active energy ray. The value (| AB) is 0 to 20 mN / m, preferably 0 to 10 mN / m. If the absolute value (| A−B |) of the difference between the surface tension value A and the surface tension value B exceeds 20 mN / m, the smoothness of the formed image may be impaired, or density unevenness may occur. As a result, a high-definition image cannot be obtained.

  Further, in the ink according to the present invention, it is preferable that the value B does not substantially change after 50% of the irradiation energy necessary for curing the ink is applied. This is because, when an image is formed by further ejecting ink onto an ink image that has been previously ejected and cured on a recording medium, if an attempt is made to increase the recording speed, the following is performed on the ink that is not completely cured. Of ink may land. In such a case, if the surface tension value B is a characteristic that greatly depends on the irradiation energy, the ink will land on the image surface having various surface tensions. As a result, it is difficult to obtain a high-definition image.

  That the surface tension value B in the present invention does not substantially change means that the difference from the surface tension of the completely cured ink is within 5 dyn / cm.

  In the ink according to the present invention, when an image is formed using an ink set composed of a plurality of inks, it is preferable that the maximum value of the difference in surface tension value B between the inks is 10 mN / m or less. When the difference between the inks exceeds 10 mN / m, the dot shapes formed by the respective inks vary and cause image unevenness, so that it is difficult to obtain a high-definition image.

  In the present invention, the method for setting the surface tension of the ink cured by irradiation with the active energy ray defined above as a condition defined in the present invention is not particularly limited, but the type and amount of the surfactant, or the above This can be realized by appropriately adjusting the kind and addition amount of the pigment dispersant described, the kind and addition amount of the polymerizable component, and the kind and addition amount of the polymerization initiator.

  The surfactant that is one of the means for adjusting the surface tension will be described below.

  The surfactant that can be used in the present invention is not particularly limited, and examples thereof include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxy Nonionic surfactants such as ethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers, phosphate esters, cationic surfactants such as alkylamine salts and quaternary ammonium salts, fluorine And surface active agents. Of these, anionic surfactants and nonionic surfactants are particularly preferred.

  As described above, the present invention is characterized by using a recording medium having a surface tension value A such that the difference from the surface tension of the cured ink is 0 to 20 mN / m.

  In the present invention, as a method for determining the surface tension value (mN / m) of the recording medium and the cured ink, the respective contact angles of water, methylene iodide and nitromethane are measured on the recording medium or the cured inkjet image surface. After that, the solid surface tension value (mN / m) of the inkjet image can be obtained by calculation according to the calculation formula described in Journal of the Adhesion Society of Japan, Vol. 8, page 131 (1972).

Serial Rokunakadachi body Ru used in the present invention, PET (polyethylene terephthalate) film, OPS (oriented polystyrene) film, OPP (oriented polypropylene) film, ONy (oriented nylon) films and PVC 1 kind selected from (polyvinyl chloride) film It is characterized by being. In these recording media, not only curling and deformation of the film are likely to occur due to curing shrinkage of the ink, heat generation during the curing reaction, and the like, but the ink film is difficult to follow the shrinkage of the recording medium.

  The surface energy of these various plastic films is greatly different, and the dot diameter after ink landing varies depending on the recording medium, which has been a problem in the past. Select a recording medium that satisfies the conditions specified in the present invention. By doing so, it is possible to obtain an image excellent in bleeding resistance, image density unevenness resistance, and smoothness.

  With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording media having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording medium in terms of the cost of the recording medium such as the packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  In the ink jet recording method of the present invention, ink is ejected and drawn on a recording medium by the ink jet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

  As the ink ejection conditions, it is preferable from the viewpoint of ejection stability that the recording head and ink are heated to 35 to 100 ° C. and ejected. Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 2 to 15 pl.

  In the ink jet recording method of the present invention, as the irradiation condition of the generated light, the active light is preferably applied within 0.001 to 2.0 seconds after ink landing, and more preferably 0.001 to 1.0. Seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, irradiation with actinic rays is divided into two stages. First, actinic rays are irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further, actinic rays are irradiated after all printing is completed. The method is also a preferred embodiment. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording medium that occurs during ink curing.

In the present invention, it is preferable to use an actinic ray having a low illuminance having a maximum illuminance of 0.1 to 50 mW / cm ² in a wavelength range effective for curing. Conventionally, in the UV inkjet method, in order to suppress dot spreading and bleeding after ink landing, a light source having a high illuminance exceeding the maximum illuminance in the wavelength range effective for curing exceeds 50 mW / cm ² has been used. . However, when these light sources are used, the shrinkage of the recording medium is too large, particularly in the case of shrink labels and the like, and the actual situation is that the recording medium cannot be used.

  Examples of the light source used for actinic ray irradiation include, but are not limited to, a low-pressure mercury lamp, UV laser, xenon flash lamp, insect trap, black light, germicidal lamp, cold cathode tube, and LED.

In the present invention, it is also effective to use an actinic ray having a maximum illuminance of 50 to 3000 mW / cm ² in a wavelength range effective for curing. Although it is a light source of high illuminance used for conventional UV inkjet recording, there is a problem of shrinkage of the recording medium as described above, and substantially UV inkjet recording has not been used in the field of flexible packaging printing and label printing. In the configuration of the present invention, this problem is solved, and high-definition images can be formed on various plastic films even when a conventionally used high-illuminance light source is used. Examples of the light source include, but are not limited to, a high-pressure mercury lamp, a metal halide lamp, and an electrodeless UV lamp.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

<< Preparation of pigment dispersion >>
Each composition described below was dispersed in a sand mill for 1 hour and then filtered to prepare each pigment dispersion.

(Preparation of black pigment dispersion)
Carbon black 10 parts by weight Cationic polymerizable compound (OXT221, oxetane compound, manufactured by Toagosei Co., Ltd.) 88 parts by weight Pigment dispersant (Ajisper PB822, manufactured by Ajinomoto Finetech) 2 parts by weight (Preparation of yellow pigment dispersion)
C. I. Pigment Yellow 180 10 parts by weight Cationic polymerizable compound (OXT221 supra) 88 parts by weight Pigment dispersant (Azisper PB822 supra) 2 parts by weight (Preparation of magenta pigment dispersion)
C. I. Pigment Red 146 10 parts by weight Cationic polymerizable compound (OXT221 supra) 88 parts by weight Pigment dispersant (Azisper PB822 supra) 2 parts by weight (Preparation of cyan pigment dispersion)
C. I. Pigment Blue 15: 3 10 parts by weight Cationic polymerizable compound (OXT221, supra) 88 parts by weight Pigment dispersant (Azisper PB822, supra) 2 parts by weight << Preparation of ink >>
Each color ink was prepared with the constitution described in Tables 1 to 4 using each of the pigment dispersions prepared above.

  Each color ink was prepared by adding all the additives other than the pigment dispersions listed in each table and confirming that they were sufficiently dissolved. After each addition, the mixture was sufficiently stirred using a dissolver, and then filtered through a 0.8 μm filter. In addition, pre-filtration with a 10 μm filter was performed as a pretreatment. In the filtration step, the occurrence of pressure loss was small, and a sufficient filtration rate was obtained.

  Next, the ink was heated to 50 ° C., and the pressure was reduced while stirring to remove dissolved air and moisture, thereby preparing each ink.

<Measurement of ink characteristic values>
[Measurement of surface tension value B of cured inkjet image]
The solid surface tension of the cured inkjet image defined in the present invention was determined by the following method.

  After measuring the contact angles of water, methylene iodide and nitromethane on the cured inkjet image surface formed according to the inkjet recording method described below, the calculation described in Journal of the Adhesion Society of Japan, Vol. 8, page 131 (1972) The solid surface tension value (mN / m) of the inkjet image was determined by calculation according to the equation.

[Measurement of surface tension (* 1) of inkjet image when 50% of irradiation energy required to cure ink is irradiated]
After forming an inkjet image according to the method described later, when the ink was irradiated with 50% of the irradiation energy required to be cured until it could not be removed with a finger, the surface tension of the ink image was measured in the same manner as described above. .

  Each surface tension measured value obtained by the above was similarly described in Tables 1-4.

  The details of the additives and abbreviations listed in Tables 1 to 4 are as follows.

OXT221: Cationic polymerizable compound (supra)
2021P: Cationic polymerizable compound (Celoxide 2021P epoxy compound manufactured by Daicel Chemical Industries, Ltd.)
3000: Cationic polymerizable compound (Celoxide 3000 epoxy compound manufactured by Daicel Chemical Industries)
INI: Photocationic polymerization initiator (triphenylsulfonium hexafluorophosphate)
178K: Fluorosurfactant (Megafac F178K manufactured by Dainippon Ink & Chemicals, Inc.)
ED152: Phosphate ester surfactant (PLAAD ED152 manufactured by Enomoto Kasei Co., Ltd.)
* 1: Surface tension (mN / m) of the inkjet image when 50% of the irradiation energy required to cure the ink is irradiated
<Inkjet image output>
Next, using an inkjet recording apparatus having a piezo-type inkjet nozzle having a nozzle diameter of 23 μm and 128 nozzles, an OPP (stretched polypropylene) film having a surface tension (surface energy) of 47 mN / m and an OPP (simple) of 52 mN / m are used as recording media. Adhesives) Images were recorded on film.

  The ink supply system used consisted of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head, and heat insulation and heating were performed from the front chamber tank to the head portion. Temperature sensors were provided in the vicinity of the front chamber tank and the nozzle of the piezo head, respectively, and temperature control was performed so that the nozzle portion was always 60 ± 2 ° C. The droplet size was about 7 pl, and ejection was possible at a resolution of 720 × 720 dpi (where dpi means the number of dots per 2.54 cm), and the liquid was driven at a driving frequency of 10 kHz.

Image formation was performed by a four-color full-color printer in which four-color heads of Y, M, C, and K were mounted on the piezo head carriage in combinations shown in Tables 5 and 6. Cold cathode lamps with a wavelength of 308 nm (custom products manufactured by Hibeck Co.) were mounted on both ends of the carriage, the head was scanned, and ultraviolet rays were irradiated within 1000 ms after ink landing. The exposure surface illuminance was 15 mW / cm ² . The exposure energy was adjusted by changing the speed of the head carriage so that all ink was irradiated.

<Evaluation of inkjet image>
The following evaluation was performed for each full-color image output using the inkjet recording apparatus described above.

(Evaluation of smear resistance)
Each adjacent color dot was magnified with a magnifying glass, the degree of bleeding was visually observed, and bleeding resistance was evaluated according to the following criteria.

◎: Adjacent dot shape maintains a perfect circle and no blurring ○: Adjacent dot shape maintains an almost perfect circle and almost no blur △: Adjacent dot is slightly blurred and the dot shape is slightly displaced , Level that can be used at the end ×: Level where adjacent dots are blurred and mixed and cannot be used (Evaluation of unevenness in image density)
A black solid image was output by the above-described ink jet recording apparatus, and after ultraviolet irradiation, density unevenness was visually observed and evaluated according to the following criteria.

◎: Good with no density unevenness ○: There is some density unevenness, but there is no problem in high-definition printing △: There is density unevenness, but somehow usable level ×: Unusable density unevenness, unusable level (Smoothness Evaluation)
A black solid image was output by the above-described ink jet recording apparatus, and after ultraviolet irradiation, the ink film thickness and unevenness were visually observed and evaluated according to the following criteria.

◎: Image thickness is thin and good image quality ○: Image has thickness but no unevenness, high-definition printed image △: Image has thickness and some unevenness is observed, but practical Table 5 and Table 6 show the evaluation results obtained as described above. The evaluation results obtained above are in the allowable range ×: the image has a thickness and the image unevenness is conspicuous and has a practical problem.

  As is apparent from Tables 5 and 6, the absolute value (|) of the difference between the surface tension value (AmN / m) of the recording medium and the surface tension value (BmN / m) of the ink cured by irradiation with active energy rays. It can be seen that the ink jet recording method of the present invention in which A-B |) is 0 to 20 mN / m is superior to the comparative example in bleeding resistance, image density unevenness resistance and smoothness of the formed image.

  Further, the above-described effect is that the surface tension value B is a level using ink that does not substantially change after the irradiation of 50% of the irradiation energy required to cure the ink, and the difference in the value B between the inks. It was confirmed that by using an ink set having a maximum value of 10 mN / m or less, bleeding resistance, image density unevenness resistance and smoothness were further improved.

Claims (4)

An ink containing a curable, cationic polymerizable component in the active energy ray, ejection to a recording medium from an inkjet recording head, after having landed, the ink jet recording method for forming an image by curing with an active energy ray, the The ink contains a compound represented by the following general formula (7) as the cationic polymerizable component, and the recording medium is selected from a polyethylene terephthalate film, a stretched polystyrene film, a stretched polypropylene film, a stretched nylon film, and a polyvinyl chloride film. The surface tension value (AmN / m) of the recording medium is 35 mN / m or more and 60 mN / m or less, and the surface tension value (BmN / m) of the ink cured by irradiation with the active energy ray There 30 mN / m or more and less 50 mN / m, and the table Ink jet recording method is characterized in that it is a 0~20mN / m absolute value of the difference between the tension value (AmN / m) surface tension values (BmN / m) (| | A-B).

[Wherein, R ¹ represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group, an allyl group, an aryl group, a furyl group, or a thienyl group. ] R in the general formula (7) ¹ The ink jet recording method according to claim 1, wherein is an alkyl group having 1 to 6 carbon atoms. The inkjet recording method according to claim 1, wherein the recording medium is a polyethylene terephthalate film, a stretched polystyrene film, or a stretched polypropylene film. The surface tension value (BmN / m) of the ink cured by the irradiation of the active energy ray does not substantially change after 50% of the irradiation energy required for curing the ink is irradiated. Item 4. The inkjet recording method according to any one of Items 1 to 3.