Inkjet method and inkjet device

Abstract

The present invention provides an inkjet method and an inkjet device, which improve the balance between the color reproduction range and bleeding. The inkjet recording method includes: a step of ejecting a first composition of a radiation-curable type from an inkjet head at a color angle of -50 to -5°; a step of ejecting a second composition of a radiation-curable type from the inkjet head at a color angle of 5 to 50°; and an irradiation step of irradiating the ejected first composition with radiation within 1 second after landing and irradiating the ejected second composition with radiation within 1 second after landing to cure the compositions.

Description

[0001] This application is a divisional application of patent application filed on August 29, 2019, with application number 201910808476.0 and entitled "Inkjet Method and Inkjet Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to inkjet methods and recording devices. Background Technology

[0003] Inkjet recording methods can record high-resolution images using relatively simple devices and have been rapidly developed in various aspects. For example, Patent Document 1 discloses an active energy ray curable inkjet ink with excellent pigment dispersibility, ejection stability, and storage stability, composed of a polymeric dispersant, monomers, diketopyrrolopyrrole pigments, and pigment derivatives represented by a specific general formula.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2006-348200

[0005] However, according to the ink composition described in Patent Document 1, there is room for improvement in terms of the color reproduction range and the balance of bleeding. Summary of the Invention

[0006] The inventors of this invention conducted intensive research to solve the aforementioned problems. As a result, they discovered that using a combination of two inks with a specified hue angle under specified conditions could solve these problems, thus completing this invention.

[0007] That is, the inkjet method of the present invention includes: a step of ejecting a first composition of radiation curable type with a hue angle of -50 to -5° from an inkjet head; a step of ejecting a second composition of radiation curable type with a hue angle of 5 to 50° from an inkjet head; and a step of irradiating each composition with radiation for curing within 1 second after each ejected composition has landed.

[0008] The present invention may also be configured as follows.

[0009] An inkjet printing method includes: a step of ejecting a first composition of radiation curable type with a hue angle of -50 to -5° from an inkjet printhead; a step of ejecting a second composition of radiation curable type with a hue angle of 5 to 50° from an inkjet printhead; and an irradiation step, wherein the first composition is irradiated with radiation within 1 second after impact, and the second composition is irradiated with radiation within 1 second after impact, so as to cure the composition.

[0010] An inkjet device includes: an inkjet head for performing the above-described inkjet method; and a radiation source. Attached Figure Description

[0011] Figure 1 This is a schematic cross-sectional view showing the structure of a printhead printer.

[0012] Figure 2 This is a three-dimensional diagram showing the structure of a serial printer.

[0013] Figure 3 This is a schematic diagram illustrating an overview of the recording method one used in the embodiment.

[0014] Figure 4 This is a schematic diagram illustrating the general outline of recording method two used in the embodiment.

[0015] Figure 5 This is a schematic diagram illustrating the general outline of recording method three used in the embodiments.

[0016] Figure 6 This is a schematic diagram illustrating the general outline of recording method four used in the embodiments.

[0017] Figure 7 This is a schematic diagram illustrating the overview of recording method five used in the embodiments.

[0018] Figure 8 This is a schematic diagram illustrating the outline of recording method six used in the embodiments.

[0019] Explanation of reference numerals in the attached figures

[0020] 1. Line printer; 110. Feed section; 120. Transport section; 130. Recording section; 131. Inkjet head; 132, 133. Light source; 140. Drying section; 150. Discharge section; 2. Serial printer; 220. Transport section; 230. Recording section; 231. Inkjet head; 232, 233. Light source; 234. Carriage; 235. Carriage moving mechanism; F. Recording medium; Y. Transport direction; S1, S2. Main scanning direction; T1. Sub-scanning direction. Detailed Implementation

[0021] Hereinafter, embodiments of the present invention (hereinafter referred to as "this embodiment") will be described in detail with reference to the accompanying drawings as needed. However, the present invention is not limited thereto, and various modifications can be made without departing from its spirit. It should be noted that in the drawings, the same reference numerals are used for the same elements, and repeated descriptions are omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Moreover, the scale of the drawings is not limited to the scale shown in the drawings.

[0022] [Inkjet method]

[0023] The inkjet method of this embodiment includes a step of ejecting a first composition of radiation-curable type with a hue angle of -50 to -5° from an inkjet head, a step of ejecting a second composition of radiation-curable type with a hue angle of 5 to 50° from an inkjet head, and a step of irradiating each composition with radiation within 1 second after each ejected composition has landed, thereby curing it.

[0024] In signature or label printing, warm color regions are widely used; however, it is known that the color reproduction range of warm color regions is relatively narrow. Furthermore, even slight color differences in the recorded material tend to be easily noticeable to the naked eye. When printing the desired color, a wider color reproduction range results in higher color reproducibility, which is more advantageous. From the perspective of suppressing bleeding, radiation-cured compositions cure relatively quickly upon exposure to radiation. However, it is known that with such methods, curing occurs before the adhering composition diffuses onto the recording medium, resulting in decreased color viability and a narrower color reproduction range. To address this, in this embodiment, by combining a first radiation-cured composition with a hue angle of -50 to -5° and a second radiation-cured composition with a hue angle of 5 to 50°, both suppression of bleeding and ensuring a wide color reproduction range can be simultaneously achieved in a recording method that cures relatively quickly upon exposure to radiation.

[0025] The following describes each step; however, the recording method of this embodiment can be used in either a line printer with a line printhead or a serial printer with a serial printhead. In the line printer mode using a line printhead, the printhead is fixed, and the recording medium is moved along the sub-scanning direction (the longitudinal direction and transport direction of the recording medium). In conjunction with this movement, a composition is ejected from the nozzle opening of the printhead, thereby recording an image on the recording medium. Furthermore, in the serial printer mode using a serial printhead, the printhead is moved along the main scanning direction (the transverse direction and width direction of the recording medium). In conjunction with this movement, a composition is ejected from the nozzle opening of the printhead, thereby recording an image on the recording medium.

[0026] It should be noted that in both line and serial printing modes, the inkjet head is a printhead that ejects various compositions onto a recording medium for recording. This printhead has a cavity that ejects the contained compositions from nozzles, an ejection drive unit that provides the driving force for ejecting the ink compositions, and nozzles that eject the compositions to the outside of the printhead. Typically, each composition is filled corresponding to a specific nozzle row, and the same composition is ejected from the same nozzle row; however, this is not a limitation. The ejection drive unit may also be formed using electromechanical conversion elements such as piezoelectric elements that change the cavity volume through mechanical deformation, or electrothermal conversion elements that generate and eject bubbles from the composition through heating.

[0027] Inkjet printing is a method of producing a composition by inkjet printing. Examples include recording methods that attach the inkjet-printed composition to a recording medium to create a recording object, and modeling methods that laminate the inkjet-printed composition to create a model of the composition.

[0028] [The spraying process of the first composition]

[0029] This process involves ejecting a radiation-cured first composition with a hue angle of -50° to -5° from the inkjet head onto the recording medium. The first composition used in this process is equivalent to magenta ink, and by combining it with yellow and cyan inks, it is possible to uniformly reproduce colors across all hue angles. Based on this understanding, the first composition has a hue angle of less than 0°.

[0030] (First Composition)

[0031] The hue angle of the first composition is -50 to -5°, preferably -30 to -10°, more preferably -25 to -13°, and even more preferably -20 to -15°. Since the hue angle of the first composition is within the above range, the color reproduction range tends to be further improved.

[0032] As long as the first composition is a radiation-curable composition with a hue angle of -50 to -5°, there are no particular limitations on its composition. Examples include substances containing pigments, polymerizable compounds, polymerization initiators, and dispersants, and, if necessary, polymerization inhibitors, surfactants, or other additives. The components are described below.

[0033] Radiation-cured compositions are compositions that are cured by radiation before use. Examples of radiation include ultraviolet light, visible light, and electron beams.

[0034] Inkjet compositions are compositions used by being ejected from an inkjet head using an inkjet method.

[0035] (pigment)

[0036] The hue angle of the first composition is determined based on the pigment. Preferably, the pigment included in the first composition is one or more selected from the group consisting of PR31, 122, 202, 207, 209, 147, 269, PV32, and 19, with PR122 being more preferred. By using such a pigment, in addition to further improving the color reproduction range, the composition with a specified hue angle can be easily adjusted. Furthermore, since the cured first composition forms a coating film covering the pigment, the pigment tends to have improved weather resistance compared to its original lightfastness. Moreover, as pigments, it is also possible to select pigments in combination such that the hue angle of the first composition is -50 to -5°. In this respect, the hue angle of a single pigment is not limited to -50 to -5°.

[0037] It should be noted that in this embodiment, the hue angle is determined based on the colorimetric values ​​obtained by measuring the recorded material using the composition according to CIELAB. However, the hue angle of the first composition is expressed in the range of -90 to 0°. Regarding the range of -90 to 0°, when expressed as a range of 270 to 360° after +360°, the position of the angle on the a*b* plane is the same.

[0038] The hue angle of the second composition is expressed in the range of 0 to 90°. The hue angles of the other compositions are expressed in the range of 0° and less than 360°.

[0039] The hue angles of the first and second compositions in this embodiment are the hue angles when a* is 60. These compositions are filled into an inkjet recording apparatus and adhered to a recording medium. Then, an LED with a peak wavelength of 395 nm is used as a light source, and the illumination energy is 500 mJ / cm². 2 Peak intensity 1000mW / cm 2 Ultraviolet light is used to cure the composition, thus creating a colorimetric pattern. It should be noted that the colorimetric pattern is created by gradually increasing the amount of the composition adhered, from a small amount to a larger amount, according to a specified adhesion amount, to create multiple recording patterns with different adhesion amounts. For example, the adhesion amount is increased successively by 0.1 mg / inch. 2 To create the pattern, adjust the amount of adhesion specified above or below to obtain the correct hue angle when a* is 60.

[0040] Furthermore, colorimetric measurements were performed on the colorimetric pattern using a spectrophotometer based on CIE LAB under conditions of light source D50, viewing angle 2°, white standard of absolute white, and no light source filter. Within the colorimetric pattern, the hue angle of the area designated as having a colorimetric value of 60 or higher, and representing the area with the lowest composition adhesion, was measured.

[0041] It should be noted that the hue angle of the compositions other than the first and second compositions is the hue angle when the same amount of adhesion was applied as when the hue angle of the first ink was calculated.

[0042] Based on the measured values ​​of a* and b*, calculate the phase angle using CIELAB. The calculation formula is as follows.

[0043] h = tan -1 (b* / a*)

[0044] The hue angle can be +360° or -360° to make the range of representation above correspond to each composition.

[0045] Preferably, the pigment content relative to the total amount of the first composition is 7.5% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2% by mass or less. Furthermore, preferably, the pigment content relative to the total amount of the first composition is 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. With the pigment content within the above-mentioned range, the optical concentration of the recorded material and the dispersion stability of the composition tend to be further improved. In particular, the cured product of the first composition forms a coating film by covering the pigment, making it difficult for the pigment to settle to the bottom of the coating film; therefore, even a small amount of pigment can exhibit high color rendering properties.

[0046] (polymeric compounds)

[0047] The polymerizable compound is polymerized using a polymerization initiator described later, resulting in the curing of the composition. Such polymerizable compounds can be made from various known monofunctional, difunctional, and trifunctional or more polyfunctional monomers and oligomers. Examples of such monomers include unsaturated carboxylic acids and / or their salts or esters such as (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid; urethanes; amides and their anhydrides; acrylonitrile; styrene; various unsaturated polyesters; unsaturated polyethers; unsaturated polyamides; and unsaturated urethanes. Examples of such oligomers include oligomers formed from the aforementioned monomers such as linear acrylic acid oligomers; epoxy (meth)acrylates; oxetane (meth)acrylates; aliphatic urethane (meth)acrylates; aromatic urethane (meth)acrylates; and polyester (meth)acrylates.

[0048] Esters of (meth)acrylic acid are preferred in the aforementioned polymerizable compounds. More specifically, examples of monofunctional (meth)acrylic esters include isopentyl (meth)acrylic acid, stearoyl (meth)acrylic acid, dodecyl (meth)acrylic acid, octyl (meth)acrylic acid, decyl (meth)acrylic acid, isotetradecyl (meth)acrylic acid, isostearyl (meth)acrylic acid, 2-ethylhexyl diethylene glycol (meth)acrylic acid, 2-hydroxybutyl (meth)acrylic acid, butoxyethyl (meth)acrylic acid, ethoxydiethylene glycol (meth)acrylic acid, methoxydiethylene glycol (meth)acrylic acid, methoxy polyethylene glycol (meth)acrylic acid, and methoxypropylene glycol (meth)acrylic acid. Monofunctional (meth) acrylates with aromatic ring skeletons, such as esters, tetrahydrofurfuryl (meth) acrylates, isobornyl (meth) acrylates, 2-hydroxyethyl (meth) acrylates, 2-hydroxypropyl (meth) acrylates, lactone-modified flexible (meth) acrylates, tert-butylcyclohexyl (meth) acrylates, dicyclopentyl (meth) acrylates, dicyclopentenyloxyethyl (meth) acrylates and phenoxyethyl (meth) acrylates, phenoxydiethylene (meth) acrylates, 2-hydroxy-3-phenoxypropyl (meth) acrylates and benzyl (meth) acrylates, as well as (meth) acrylates containing vinyl ether groups.

[0049] Among the aforementioned (meth)acrylates, difunctional (meth)acrylates include, for example, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, dihydroxymethyl-tricyclodecane (meth)acrylate, bisphenol A EO (ethylene oxide) adduct dimethacrylate, bisphenol A PO (propylene oxide) adduct dimethacrylate, hydroxypentanoic acid neopentyl glycol dimethacrylate, and polytetramethylene glycol dimethacrylate. Among these, at least one of diethylene glycol di(meth)acrylate and tripropylene glycol di(meth)acrylate is preferred.

[0050] Among the aforementioned (meth)acrylates, examples of multifunctional (meth)acrylates with trifunctionality or higher include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerol propoxy tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0051] To achieve excellent curability and consequently low viscosity of the ink, phenoxy(meth)acrylates, (meth)acrylates containing vinyl ether groups, and dipropylene glycol di(meth)acrylates are preferred. In particular, from the perspective of curability and low viscosity, the first and second compositions preferably include 2-(2-vinyloxyethoxy)ethyl acrylate as (meth)acrylates containing vinyl ether groups. It should be noted that (meth)acrylates containing vinyl ether groups are compounds represented by the following general formula (I).

[0052] CH2=CR 1 -COOR 2 -O-CH=CH-R 3 ……(I)

[0053] In the above general formula (I), R 1 It is a hydrogen atom or a methyl group, R 2 It is a divalent organic residue with 2 to 20 carbon atoms, R 3 It is a monovalent organic residue with 1 to 11 hydrogen or carbon atoms. As R 2 The divalent organic residues representing 2 to 20 carbon atoms are preferably linear, branched, or cyclic substituted alkylene groups with 2 to 20 carbon atoms, substituted alkylene groups with 2 to 20 carbon atoms having ether bonds and / or ester bonds in their structure, or substituted divalent aromatic groups with 6 to 11 carbon atoms. Preferably, alkylene groups with 2 to 6 carbon atoms, such as vinyl, n-propenyl, isopropenyl, and butenyl, and alkylene groups with 2 to 9 carbon atoms having ether bonds in their structure, such as oxyvinyl, oxyn-propenyl, oxyisopropenyl, and oxybutenyl, are used. Furthermore, as R... 3The represented monovalent organic residue having 1 to 11 carbon atoms is preferably a linear, branched, or cyclic substituted alkyl group having 1 to 10 carbon atoms, or a substituted aromatic group having 6 to 11 carbon atoms. Among these, alkyl groups having 1 to 2 carbon atoms (e.g., methyl or ethyl), phenyl groups, and aromatic groups having 6 to 8 carbon atoms, such as benzoyl groups, are preferred.

[0054] When the aforementioned organic residues are substituted groups, the substituents are classified into groups containing carbon atoms and groups not containing carbon atoms. First, when the substituent is a group containing carbon atoms, the carbon atom is counted as the number of carbon atoms in the organic residue. Although groups containing carbon atoms are not limited to those described below, examples such as carboxyl groups and alkoxy groups can be listed. Then, although groups not containing carbon atoms are not limited to those described below, examples such as hydroxyl groups and halogen groups can be listed.

[0055] Preferably, the content of 2-(2-ethyleneoxyethoxy)ethyl acrylate is 35% by mass or less relative to the total amount of the composition, more preferably 30% by mass or less, and even more preferably 35% by mass or less. By keeping the content of 2-(2-ethyleneoxyethoxy)ethyl acrylate within the above range, the effects of curability and low viscosity can be obtained.

[0056] In addition, as a polymerizable compound, it may also contain N-vinyl compounds. Examples of N-vinyl compounds include N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine and their derivatives.

[0057] The aforementioned polymeric compounds can be used alone or in combination with two or more.

[0058] The preferred content of the polymeric compound is 60-98% by mass relative to the total ink volume, more preferably 70-95% by mass, and even more preferably 80-92% by mass. By keeping the content of the polymeric compound within the above range, curability is further improved, bleeding of the resulting record is suppressed, and abrasion resistance tends to be further improved.

[0059] (Polymerization initiator)

[0060] Photopolymerization initiators are not particularly limited to any type of polymerizable compound that generates active species through radiation irradiation and can initiate the polymerization of the aforementioned polymerizable compounds. However, examples that can be listed include aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thiolated compounds (thioxanone compounds, compounds containing thiophene groups, etc.), α-aminoalkylphenyl ketone compounds, hexaaryldiimidazole compounds, ketoxime ester compounds, borate compounds, azazine compounds, metallocene compounds, active ester compounds, compounds with carbon-halogen bonds, and alkylamine compounds. More specifically, examples include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthones, fluorene, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, michidone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, and 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one. 2-Hydroxy-2-methyl-1-phenylpropane-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2,4-diethylthioxanthone, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0061] Commercially available polymerization initiators include, for example, IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one) / IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-one), DAROCUR 1173 (2-hydroxy-2-methyl-1-phenyl-propane-1-one), IRGACURE 2959 (1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one), IRGACURE 127 (2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]phenyl]-2-methyl-propane-1-one}, IRGACURE 907 (2-Methyl-1-(4-methylthiophenyl)-2-morpholinopropyl-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1), IRGACURE 379 (2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholino)phenyl]-1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), IRGACURE 784 (bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrolo-1-yl)-phenyl)titanium), IRGACURE OXE 01 (1,2-Octanedione, 1-[4-(phenylthio)-,2-(O-benzoyl oxime)]), IRGACURE OXE 02 (Ethyl ketone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyl oxime)), IRGACURE 754 (a mixture of hydroxyphenylacetic acid, 2-[2-oxo-2-phenylacetoxyethoxy]ethyl and hydroxyphenylacetic acid, 2-(2-hydroxyethoxy)ethyl ester) (all manufactured by BASF), Speedcure TPO, Speedcure DETX (2,4-diethylthioxanthone), Speedcure ITX (2-isopropylthioxanthone) (all manufactured by Lambson), KAYACURE DETX-S (2,4-diethylthioxanthone) (manufactured by Nippon Kayaku Co., Ltd.), Lucirin TPO, LR8893, LR8970 (all manufactured by BASF) and Ebecryl P36 (manufactured by UCB), etc.

[0062] Among these, DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) and IRGACURE 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) are preferred, and these polymerization initiators are also preferred. By using such polymerization initiators, curability is further improved, bleeding of the obtained record is suppressed, and there is a tendency to further improve abrasion resistance.

[0063] The preferred content of the polymerization initiator relative to the total amount of the composition is 2.5 to 15% by mass, more preferably 5 to 12.5% ​​by mass, and even more preferably 7.5 to 10% by mass. With the content of the polymerization initiator within the above range, the curability is further improved, the bleeding of the obtained record is suppressed, and there is a tendency to further improve the wear resistance.

[0064] (Dispersant)

[0065] There are no particular limitations on the term "dispersant." Examples include polymeric dispersants commonly used in the preparation of pigment dispersions. Specific examples include dispersants whose main components are one or more of the following: polyoxyethylene polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicone polymers, sulfur-containing polymers, fluoropolymers, and epoxy resins. Commercially available polymeric dispersants include the AJISPER series manufactured by Ajinomoto Fine Chemicals Co., Ltd.; the Solsperse series (Solsperse 36000, etc.) available from Avecia and Noveon; the Disparbiq series manufactured by BYK Chemie; and the DISPARON series manufactured by Kusumoto Chemical Co., Ltd.

[0066] The preferred content of the dispersant is 0.1 to 1.5% by mass relative to the total amount of the composition, more preferably 0.25 to 1% by mass, and even more preferably 0.3 to 0.75% by mass. With the dispersant content within the above range, there is a tendency for the dispersion stability of the composition to be further improved.

[0067] (surfactant)

[0068] There are no particular limitations on the surfactant used; however, for example, as a silicone surfactant, polyester-modified silicone or polyether-modified silicone can be used, with polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane being particularly preferred. Specific examples include BYK-347, BYK-348, BYK-UV3500, 3510, 3530, and 3570 (all manufactured by BYK Corporation).

[0069] The preferred surfactant content is 0.1 to 1.5% by mass relative to the total amount of the composition, more preferably 0.25 to 1% by mass, and even more preferably 0.3 to 0.75% by mass. With the surfactant content within the above range, the bleeding of the obtained record is suppressed, and there is a tendency for a further improvement in the color reproduction range.

[0070] [The spraying process of the second composition]

[0071] This process involves ejecting a second, radiation-cured composition with a hue angle of 5 to 50° from the inkjet head onto the recording medium. The second composition used in this process is equivalent to a red ink composition, and by combining it with the first ink, it is possible to expand the color reproduction range centered on the area near a hue angle of 0°.

[0072] (Second Composition)

[0073] The hue angle of the second composition is 5–50°, preferably 10–40°, more preferably 13–25°, and even more preferably 15–20°. By having the hue angle of the second composition within the above range, there is a tendency to further improve the color reproduction range.

[0074] The composition of the second composition is not particularly limited as long as it is a radiation-curable composition with a hue angle of 5 to 50°. Examples include compositions that include pigments, polymerizable compounds, polymerization initiators, and dispersants, and may include polymerization inhibitors, surfactants, or other additives as needed. Except for the type of pigment, the second composition can be formed to have the same composition as the first composition independently of the composition of the first composition. Therefore, pigments will be described below.

[0075] Preferably, the difference in hue angle between the first composition and the second composition is 10–45°, more preferably 10–40°, and even more preferably 10–35°. By ensuring the difference in hue angle between the first composition and the second composition is within the above range, there is a tendency to further improve the color reproduction range.

[0076] (pigment)

[0077] The hue angle of the second composition is determined based on the pigment. Preferably, the pigment included in the second composition is one or more selected from the group consisting of PR166, 168, 149, 177, 179, 254, 255, 264, 242, and 224, more preferably PR254. By using such a pigment, in addition to further improving the color reproduction range, the composition with a specified hue angle can be easily adjusted. Moreover, the cured product of the second composition forms a coating film by covering the pigment, thus the pigment tends to have further improved weather resistance compared to its original lightfastness. Furthermore, as the pigment, it is also possible to select pigments in combination of two or more, resulting in a hue angle of 5 to 50° for the second composition. In this respect, the hue angle of a single pigment is not limited to 5 to 50°.

[0078] Preferably, the pigment content relative to the total amount of the second composition is 7.5% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2% by mass or less. Furthermore, preferably, the pigment content relative to the total amount of the second composition is 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. With the pigment content within the above-mentioned range, there is a tendency for further improvement in the optical concentration of the obtained record and the dispersion stability of the composition. In particular, the cured product of the second composition forms a coating film by covering the pigment, making it difficult for the pigment to settle to the bottom of the coating film; therefore, even a small amount of pigment can exhibit high color rendering properties.

[0079] [Irradiation process]

[0080] This process involves irradiating each of the sprayed compositions with radiation within one second after they land, thereby curing them. Preferably, radiation is applied within one second of landing. It should be noted that "irradiating each composition with radiation within one second of landing" means that radiation irradiation begins within one second of landing, and is the initial irradiation after the ink lands. It should also be noted that irradiation preferably ends within one second of the composition landing. Furthermore, the duration of radiation irradiation is preferably 0.5 seconds or less. Irradiation is applied within one second of landing, preferably within 0.5 seconds, more preferably within 0.3 seconds, and even more preferably within 0.2 seconds. In this case, the image quality is superior, which is preferable. On the other hand, it is preferable to irradiate 0.1 seconds or more after landing, more preferably after 0.2 seconds or more, even more preferably after 0.3 seconds or more, and even more preferably after 0.5 seconds or more. In this case, the color reproduction range is superior, which is preferable.

[0081] The specific method of irradiation is not particularly limited. However, in serial mode, a light source close to the inkjet head can be used to irradiate the main scan after ink has been ejected. Furthermore, in row mode, irradiation can be performed using a light source downstream of the inkjet head's transport direction. This irradiation can be for formal curing or for temporary curing. It should be noted that when the irradiation is for temporary curing, a second subsequent irradiation can be performed.

[0082] Temporary curing is a curing process that cures only a portion of the composition. Formal curing, on the other hand, involves further curing, such as irradiation, after temporary curing to achieve full curing. Full curing, then, is the curing process that fully cures the resulting product to a degree suitable for use as a recording, model, or other similar object.

[0083] In this case, LEDs are preferably used as the radiation source. LEDs are small and generate little heat, making them easy to position close to the inkjet head, suitable for irradiation processes that irradiate each composition with radiation within one second after landing. Furthermore, the use of LEDs tends to narrow the color reproduction range, making this invention particularly useful. Preferably, the peak wavelength of the LED is 350–420 nm.

[0084] The irradiation process can be a single irradiation process in which the irradiation process on the first composition and the irradiation process on the second composition are performed by the same irradiation process. In this case, radiation is irradiated onto the first composition within 1 second after it lands, and simultaneously, radiation is irradiated onto the second composition within 1 second after it lands.

[0085] Alternatively, the irradiation of the first composition and the irradiation of the second composition can be performed separately. In this case, the first composition is irradiated with radiation within 1 second after it lands, and the second composition is irradiated with radiation within 1 second after it lands.

[0086] The former is preferred in that irradiation can be performed in a single irradiation step, while the latter is preferred in that the start time of irradiation can be easily adjusted according to the time when the composition falls.

[0087] The composition may land on a recording medium or on a previously landed composition.

[0088] The preferred radiation energy is 5–2000 mJ / cm². 2 When this irradiation process is equivalent to a temporary curing irradiation process, the preferred irradiation energy is 2–100 mJ / cm². 2 More preferably 5–50 mJ / cm 2More preferably, it is 10–30 mJ / cm 2 .

[0089] In the case of an irradiation process equivalent to formal curing, the preferred irradiation energy is 50–2000 mJ / cm². 2 More preferably 150–800 mJ / cm 2 Further preferred is 200–400 mJ / cm 2 .

[0090] When the radiation energy is within the aforementioned range, there is a tendency to suppress the bleeding of the obtained recordings.

[0091] The preferred peak intensity of radiation exposure is 100 mW / cm². 2 The above, and more preferably 150–20000 mW / cm 2 More preferably, it is 200–10000 mW / cm 2 Furthermore, for temporary curing, a concentration of 200–1000 mW / cm² is more preferable. 2 More preferably, it is 250–500 mW / cm 2 Furthermore, during formal curing, a concentration of 1000–7000 mW / cm is more preferable. 2 More preferably, it is 1500–5000 mW / cm 2 The preferred value is 2000–4000 mW / cm². 2 When the radiation energy is within the aforementioned range, there is a tendency to suppress the bleeding of the obtained recordings.

[0092] [Other spraying processes]

[0093] In addition to the above-described ejection process, the recording method of this embodiment may also include a process of ejecting a radiation-curable cyan composition from the inkjet head and a process of ejecting a radiation-curable yellow composition from the inkjet head. Thus, by combining the cyan, magenta, and yellow compositions, colors can be reproduced evenly across all hue angles. It should be noted that, as an irradiation process, it can be performed within one second after the first and / or second compositions have landed, irradiating each composition with radiation. Alternatively, an additional irradiation process for curing the cyan and yellow compositions may be included. Alternatively, the first composition, the second composition, the cyan composition, and the yellow composition may be irradiated with radiation in a concentrated manner.

[0094] Preferably, irradiation is performed within 1 second after the cyan composition has landed, and within 1 second after the yellow composition has landed. The irradiation energy, peak intensity, and other conditions of the irradiation process can be set independently of the aforementioned irradiation process but within the same range as those of the aforementioned irradiation process.

[0095] It should be noted that the preferred cyan composition has a hue angle of 210 to 260°. Preferably, the hue angle relative to the first composition is located in a clockwise direction in the a*b* plane. Furthermore, there are no particular limitations on the pigments that can be used in the cyan composition, but examples include PB15 (e.g., 15:3), 16, 17, etc.

[0096] Furthermore, the preferred hue angle of the yellow composition is 80–110°. It is preferable that the hue angle is larger than that of the second composition. Moreover, there are no particular limitations on the pigments that can be used in the yellow composition, but examples include PY155, 150, 74, and 180.

[0097] Furthermore, in addition to the aforementioned ejection process, the recording method of this embodiment can also include a process of ejecting a radiation-cured third composition from the inkjet head, which has a hue angle larger than that of the second composition and a lower hue angle than that of the yellow composition. This results in a further improvement in the color reproduction range. It should be noted that, as an irradiation process, it can be configured such that, within one second after the first and / or second compositions have landed, each composition is irradiated with radiation, and the third composition is also irradiated to cure it. Alternatively, an additional irradiation process for curing the third composition can be included. Alternatively, the first, second, and third compositions can be irradiated with radiation simultaneously. Preferably, the irradiation process for curing the third composition involves irradiating with radiation within one second after the third composition lands. The irradiation energy, peak intensity, and other conditions of the irradiation process can be set independently of the aforementioned irradiation process, within the same range as the aforementioned irradiation process.

[0098] It should be noted that the third composition, except that it selects pigments with a hue angle larger than that of the second composition and lower than that of the yellow composition, can have the same composition as the first composition. Preferably, the hue angle of such a third composition is 55–80°. Furthermore, there are no particular limitations on the pigments that can be used in the third composition; however, PO43 can be listed as an example. By using such a third composition, there is a tendency to further improve the color reproduction range from red to yellow. The third composition can also be, for example, an orange composition.

[0099] Furthermore, in addition to the aforementioned ejection process, the recording method of this embodiment can also include a process of ejecting a radiation-curable transparent composition from the inkjet head. This further enhances the gloss of the recorded material and also tends to improve its lightfastness. It should be noted that, as an irradiation process, if a process of irradiating each composition with radiation within one second after the first and second compositions have landed can be included, then an additional irradiation process for curing the transparent composition can be added, and radiation can be concentrated after all the first, second, and transparent compositions have landed.

[0100] It should be noted that the transparent composition refers to ink not used for coloring recording media, but for other purposes. Other purposes may include adjusting the gloss of the recording media, improving the abrasion resistance of the recorded material, and enhancing the fixing and color development properties of colored inks. As components other than pigments in the transparent composition, polymerizable compounds, polymerization initiators, surfactants, etc., as exemplified in the first composition, may be used. Preferably, the content of the colorant in the transparent composition is 0.1% by mass or less, more preferably 0.05% by mass or less.

[0101] [Other irradiation procedures]

[0102] In the recording method of this embodiment, radiation irradiation can be performed only in the aforementioned irradiation step. When the composition is sufficiently cured to a fully cured state by a single irradiation in the aforementioned irradiation step, a relatively large irradiation energy is required, resulting in a tendency for the color reproduction range of the obtained record to narrow. Therefore, the present invention is particularly useful. On the other hand, in the recording method of this embodiment, in addition to the aforementioned irradiation step, a step can be included whereby each composition is further irradiated with radiation after the aforementioned irradiation step and more than one second after each composition has settled. This not only makes curing more reliable and further improves the color reproduction range, but also tends to further improve the abrasion resistance of the obtained record. Furthermore, by dividing the irradiation step into multiple stages, the upstream irradiation step can be positioned as temporary curing, and the downstream irradiation step as formal curing. In this case, bleeding can be suppressed by implementing temporary curing, and sufficient curing can be achieved through formal curing.

[0103] When performing the formal curing step as a further irradiation step, the irradiation energy and peak irradiation intensity can be set to a preferred range for the aforementioned irradiation step as the formal curing step. The further irradiation step can be performed using the aforementioned LED.

[0104] [Inkjet Printer]

[0105] The inkjet apparatus of this embodiment includes an inkjet head for performing the inkjet recording method described above and an emission source. Depending on the type of inkjet head used, the inkjet apparatus is referred to as a line printer or a serial printer. The apparatuses of these two types will be described below.

[0106] [Line printer]

[0107] Figure 1 A schematic side view of a line printer is shown. (As shown) Figure 1 As shown, the line printer 1 includes a media feed section 110, a transport section 120, a recording section 130, a drying section 140, and an ejection section 150.

[0108] The feeding unit 110 feeds the recording medium F to the conveying unit 120, and the conveying unit 120 conveys the recording medium F fed by the feeding unit 110 to the recording unit 130, the drying unit 140, and the discharge unit 150. Specifically, the conveying unit 120 has conveying rollers that convey the fed recording medium F in the conveying direction Y.

[0109] Furthermore, the recording unit 130 includes an inkjet head 131 that ejects a radiation-curing composition onto the recording medium F fed by the transport unit 120, and light sources 132 and 133 that irradiate the attached composition with radiation. In the case of a line printer, the inkjet head 131 has a line printhead with a length equivalent to or greater than the width of the recording medium, and the printhead is fixed in a (almost) immobile manner, recording in one pass. A pass is also referred to as a scan.

[0110] In this embodiment, to achieve the above-described recording method, the transport speed of the recording medium and the distance between the inkjet head 131 and the light source 132 are adjusted. It should be noted that... Figure 1 The image shows one inkjet head, but it is not limited to this; multiple inkjet heads may be used depending on the type of composition.

[0111] The drying section 140 is a component for drying the composition adhering to the recording medium as needed. It has a drying section 141 (pressure plate heater) disposed opposite to the recording section 130 and a drying section 142 disposed further downstream of the recording section 130. Furthermore, the discharge section 150 is configured to discharge the recorded material to the outside of the line printer 1. It can be omitted when drying is not required.

[0112] [Serial printer]

[0113] Figure 2 A 3D view of a serial printer is shown. (As shown) Figure 2As shown, the serial printer 2 includes a transport unit 220 and a recording unit 230. The transport unit 220 conveys the recording medium F fed to the serial printer to the recording unit 230, and discharges the recorded recording medium to the outside of the serial printer. Specifically, the transport unit 220 has conveying rollers that transport the fed recording medium F in the sub-scanning direction T1.

[0114] Furthermore, the recording unit 230 includes an inkjet head 231 that ejects a radiation-curable composition onto the recording medium F conveyed to the transport unit 220, a light source 232 that irradiates the attached composition with radiation, a carriage 234 that mounts these components, and a carriage moving mechanism 235 that moves the carriage 234 in the main scanning directions S1 and S2 of the recording medium F. In the case of a serial printer, the inkjet head 131 has a printhead whose length is less than the width of the recording medium, and the printhead moves to record in multiple passes. In a serial printer, the printhead 231 and the light source 232 are mounted on the carriage 234 that moves in a predetermined direction. As the carriage moves, the printhead moves, thereby ejecting the composition onto the recording medium. Thus, recording is performed in two or more passes. A pass is also called a main scan. A sub-scan is performed between passes to transport the recording medium. That is, main scans and sub-scans are performed alternately. In the main scan where the ejected ink settles, the ink is irradiated within one second after settling, which is the preferred method.

[0115] Furthermore, when irradiating the ink after the main scan where the ink is ejected and falls, it is preferable to irradiate it more than one second after it falls, which is an even better step for further irradiation. In this case, for example, it is preferable to irradiate the ink in the main scan after the main scan where the ink is ejected and falls.

[0116] It should be noted that if the distance of a single sub-scan is, for example, one-eighth of the length of the sub-scan direction of the inkjet head's nozzle array, then ink is applied to the same location on the recording medium by running eight times. This is referred to as an 8-pass. When the number of passes is large, applying ink to the same location on the recording medium multiple times reduces the amount of ink applied in a single pass, preventing ink dots from contacting each other and causing image quality degradation, which is preferable.

[0117] In this embodiment, to achieve the above-described recording method, the transport speed of the recording medium, the travel speed of the carriage, and the distance between the inkjet head 231 and the light source 232 are adjusted. It should be noted that... Figure 2 The image shows a light source mounted on a carriage, but it is not limited to this; a light source not mounted on a carriage may also be available.

[0118] [Example]

[0119] The present invention will now be described in more detail with reference to embodiments and comparative examples. The present invention is not limited to the embodiments described below.

[0120] [Materials for ink compositions]

[0121] The main materials used in the ink compositions in the following examples and comparative examples are as follows.

[0122] [Polymerizing compounds]

[0123] • PEA (phenoxyethyl acrylate, manufactured by Osaka Organic Chemicals Co., Ltd.)

[0124] • VEEA (2-(2-Ethyleneoxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd.) • DPGDA (Dipropylene glycol diacrylate, manufactured by Sartamomer Co., Ltd.)

[0125] [Polymerization initiator]

[0126] • 819 (IRGACURE 819, manufactured by BASF)

[0127] • TPO (DAROCURE TPO, manufactured by BASF)

[0128] [surfactants]

[0129] • UV3500 (BYK-UV3500, manufactured by BYK Corporation)

[0130] [Polymerization inhibitor]

[0131] • Methylhydroquinone (hereinafter referred to as "MEHQ").

[0132] [Dispersant]

[0133] Solsperse 36000 (manufactured by Lubrizol)

[0134] [Adjustment of Pigment Dispersion]

[0135] Mix the pigments and dispersants listed in the table below according to the mass ratios in the table to form a pigment mixture. Mix the main monomers (PEA or PEA and VEEA) according to the mass ratios listed in the table below to form a monomer mixture. Mix the pigment mixture in the monomer mixture and stir using a bead mill to prepare a pigment dispersion.

[0136] [Preparation of the composition]

[0137] The pigment dispersion obtained as described above, the monomer residue, and other materials were mixed according to the compositions shown below, and stirred thoroughly to obtain the various compositions. It should be noted that in Table 1 below, the values ​​are in mass %, totaling 100.0% by mass.

[0138]

[0139] [Methods for measuring hue angle]

[0140] The hue angle is the hue angle when a* is 60. The composition obtained as described above is filled into an inkjet recording device (trade name "SC-S30650", manufactured by Epson Corporation), and then adhered to the recording medium (manufactured by MACtac Corporation, white PVC medium 5829R). Then, an LED with a peak wavelength of 395 nm is used as the light source, and the device is irradiated with an irradiation energy of 500 mJ / cm². 2 Peak intensity 1000mW / cm 2 The ultraviolet light is used to cure the composition and form a colorimetric pattern. It should be noted that the colorimetric pattern formed in this way has multiple layers that increase the adhesion amount of the composition by 0.1 mg / inch each time. 2 Patterns with varying amounts of adhesion were used. It should be noted that the peak intensity was measured using a UM-10 ultraviolet intensity meter and a UM-400 light-receiving unit (both manufactured by KONICA MINOLTA SENSING) at equal distances from the light source and the surface of the recording medium.

[0141] Furthermore, the colorimetric pattern was measured using a spectrophotometer (Spectrolino SPM50, manufactured by GRETAGMACBETH) conforming to CIE LAB standards, under conditions of light source D50, viewing angle 2°, pure white as the white standard, and no light source filter. Within the colorimetric pattern, the hue angle of the region with a colorimetric value of a* greater than 60 and the lowest possible composition adhesion was measured. It should be noted that the hue angles of the compositions other than the first and second compositions were measured using the same adhesion amount as when the hue angle of the first ink was calculated.

[0142] [Ink Group]

[0143] The compositions prepared as described above are combined in the following manner to form a composition group.

[0144] Table 2

[0145]

[0146]

[0147] (Method 1)

[0148] As a serial printer, it is prepared as follows Figure 3 This is a modified version of an inkjet recording device (trade name "SC-S30650", manufactured by Epson Corporation) configured as shown, equipped with an inkjet head on a carriage and a light source (LED with a peak wavelength of 395nm). Furthermore, each of the six nozzle rows arranged along the main scanning direction of the inkjet head is individually filled with ink. During the main scan, the carriage is moved, ink is ejected from each nozzle, adhering to the recording medium, and then irradiated with radiation by light sources 232 and 233. It should be noted that, through the light source 232 adjacent to the inkjet head, the ink adhering to the recording medium is immediately irradiated with radiation during this main scan. Furthermore, through the light source 233, which is separately positioned from the inkjet head, the ink is irradiated a second time during the main scan following this main scan. By adjusting the inkjet head's moving speed (main scan speed), all ink is irradiated by the light source 232 within one second after ink adhering to the carriage. By adjusting the transport speed and the stop time between passes, all ink is irradiated by the light source 233 one second after ink adhering to the carriage. It should be noted that the time difference between ink landing and the start of irradiation caused by the position of the main scanning direction of the six nozzle rows is very small. However, the time of the ink from the nozzle row with the longest landing time is taken as the time in the table.

[0149] It should be noted that the nozzle density of each nozzle column in the inkjet head is 360 dpi. Furthermore, the recording resolution of the pattern is set such that the maximum pixel size for each ink type is 1440 × 1440 dpi. Within this pixel, the spacing between dots (droplets) is lengthened or multiple dots (droplets) are arranged to ensure that the dots are distributed as evenly as possible across the recording pattern for each ink type. The above recording is performed through eight printing passes.

[0150] (Method 2)

[0151] In addition to adopting Figure 4 The modified machine shown is equipped with an inkjet recording device (trade name "SC-S30650", manufactured by Epson Corporation) with an inkjet printhead and a light source. Recording was performed in the same manner as in Method 1. It should be noted that in Method 2, the first irradiation occurs in the main scan after the ink is ejected and falls, using a light source 233 that is separate from the printhead. Therefore, a certain amount of time is required from ink adhesion to radiation irradiation.

[0152] (Method 3)

[0153] In addition to adopting Figure 5The modified machine shown is equipped with an inkjet recording device (trade name "SC-S30650", manufactured by Epson Corporation) with an inkjet printhead and a light source. Otherwise, the recording process is the same as in Method 1. It should be noted that in Method 3, the radiation from the light source 233, which is located separately from the printhead, is not applied; otherwise, it is the same as in Method 1.

[0154] (Method 4)

[0155] As a line printer, it is prepared with Figure 6 The illustrated method is a modification of an inkjet recording device (trade name "L-4533", manufactured by Epson Corporation) equipped with an inkjet head and a light source (LED with a peak wavelength of 395nm). The inkjet head 131 has six nozzle rows arranged in the scanning direction (transport direction). Each nozzle row is filled with ink. Ink is ejected from each nozzle row, adhering to the recording medium, and the adhering ink is irradiated with radiation by the light source 132. It should be noted that the ink adhering to the recording medium is immediately irradiated with radiation by the light source 132 located near the inkjet head, and then irradiated a second time by the light source 133 located separately from the inkjet head. By adjusting the transport speed of the recording medium, all ink is irradiated by the light source 132 within one second after ink adhering. The light sources 133 are separately arranged downstream in the transport direction, and irradiation of all ink occurs one second after ink adhering. It should be noted that the time difference between the ink landing position at the location of the six nozzle rows in the scanning direction (transfer direction) and the start of irradiation is very small. However, the time of the ink in the nozzle row with the longest time from landing to the start of irradiation is used as the time in the table.

[0156] It should be noted that the nozzle density of each nozzle column in the inkjet head is set to 360 dpi. Furthermore, the recording resolution of the pattern is set to 360 dpi in the width direction of the line printhead and 1440 dpi in the paper transport direction. Within this pixel, the spacing between dots (droplets) is lengthened or multiple dots (droplets) are configured to ensure that the dots are distributed as evenly as possible according to each type of ink within the recorded pattern. The above recording is performed in a single printing pass.

[0157] (Method 5)

[0158] In addition to adopting Figure 7 The modified machine shown is equipped with an inkjet recording device (trade name "L-4533", manufactured by Epson Corporation) with an inkjet printhead and a light source. Otherwise, the recording process is the same as in Method 4. It should be noted that in Method 5, the first irradiation is performed using a light source 133 located separately from the printhead; therefore, a certain amount of time is required from ink adhesion to irradiation.

[0159] (Method Six)

[0160] In addition to adopting Figure 8 The method shown is the same as in Method 4, except that the modified machine equipped with an inkjet recording device (trade name "L-4533", manufactured by Epson Corporation) with an inkjet head and a light source is used for recording. It should be noted that in Method 6, the radiation irradiation of the light source 133, which is set separately from the inkjet head, is not performed. Otherwise, it is the same as Method 4.

[0161] In addition to the above, methods one and four, after 1 second, use the downstream formal curing light source with a peak wavelength of 2000mW / cm. 2 Irradiation 200mJ / cm 2 This is used for formal curing irradiation. Furthermore, in other methods, the initial irradiation energy is less than 200 mJ / cm². 2 The example also involves a second irradiation after 1 second, to achieve a total of 200 mJ / cm². 2 above.

[0162] Furthermore, a reference example test was conducted. The reference example used the solvent-based ink composition described in Table 7. This was not a radiation-curable composition.

[0163] [Solvent]

[0164] • Diethylene glycol ethyl methyl ether (manufactured by a Japanese emulsifier company)

[0165] • Diethylene glycol diethyl ether (manufactured by a Japanese emulsifier company)

[0166] ·γ-Butyrolactone (manufactured by Mitsubishi Chemical Corporation)

[0167] [Resin]

[0168] SOLBIN CL (manufactured by Nissin Chemical Industry Co., Ltd.)

[0169] [surfactants]

[0170] • BYK-340 (manufactured by BYK Corporation)

[0171] [Dispersant]

[0172] Solsperse 24000 (manufactured by Lubrizol)

[0173] The pigments and dispersants listed in Table 7 were mixed according to the mass ratios specified in the table to form a pigment mixture. A solvent mixture with the mass ratios of solvents specified in the table was prepared and mixed with the pigment mixture. The mixture was stirred using a bead mill to prepare a pigment dispersion. The obtained pigment dispersion, residual solvent, and other materials were mixed according to the compositions shown below and stirred thoroughly to obtain the respective compositions. It should be noted that in Table 7, the units of the values ​​are mass %, and the total is 100.0% mass.

[0174] [Color Reproduction Range]

[0175] The evaluation pattern was color-measured under the same color measurement conditions as the hue angle measurement.

[0176] As an evaluation pattern, each ink in the ink group was applied with an arbitrary amount of ink to create a pattern capable of reproducing all colors using the ink group. The printable gamut volume in the L*a*b* color space was calculated based on all color measurements, and the color reproduction range was evaluated according to the following evaluation criteria.

[0177] A: Color gamut volume is over 600,000.

[0178] B: Color gamut volume is 550,000 or more but less than 600,000

[0179] C: Color gamut volume is greater than 500,000 and less than 550,000

[0180] D: Color gamut volume less than 500,000

[0181] [Image quality (bleed) evaluation]

[0182] Each ink component of the ink group is applied in equal amounts sequentially to achieve a total adhesion amount of 10 mg / inch. 2 Under the conditions of the above-mentioned recorded test, ultraviolet light irradiation was performed to create an evaluation pattern.

[0183] It should be noted that when the ink group includes transparent ink, the inks are applied in equal amounts sequentially to ensure that the total amount of inks (excluding transparent ink) adheres to 10 mg / inch. 2 Under the conditions of the above-mentioned recorded experiment, the sample was irradiated with ultraviolet light, and then subjected to a concentration of 2 mg / inch. 2 The amount of ink adhered to the transparent ink layer by layer is overlapped, and the mixture is then subjected to ultraviolet irradiation under the same conditions to create an evaluation pattern.

[0184] The evaluation was conducted by visually confirming whether bleeding was visible in the evaluation pattern obtained as described above, and according to the evaluation criteria below. It should be noted that the same recording medium used for measuring the hue angle was employed.

[0185] (Evaluation Criteria)

[0186] A: The pattern lacks the uneven density caused by the lack of dot aggregation, and the deep parts of the pattern lack concentrated ink, resulting in a seemingly dark color.

[0187] B: The pattern does not have uneven density due to the aggregation of dots. There are some areas in the depths of the pattern where the ink is concentrated and the color appears very dark.

[0188] C: The pattern has uneven density and irregularity due to the aggregation of a few dots.

[0189] D: The pattern shows an uneven distribution of light and dark areas due to the obvious clustering of points.

[0190] [Image quality (gloss)]

[0191] The difference in gloss between the substrate and the pattern area of ​​the recording medium was visually confirmed by reflecting the fluorescent lamp onto the evaluation pattern made in the image quality (bleeding) evaluation, and the evaluation was carried out according to the following evaluation criteria.

[0192] A: I didn't notice any difference in gloss.

[0193] B: I noticed a slight difference in the sheen.

[0194] C: The difference in gloss is obvious.

[0195] [Ejection Stability Evaluation]

[0196] Recording was performed continuously for one hour using a recording device, with nozzles flushed every hour. This operation was repeated for a total of ten hours. Finally, the nozzles in the nozzle arrays used for recording the first and second inks were checked for any instances of non-dispensing. Based on the inspection results, an evaluation was conducted according to the following evaluation criteria. It should be noted that the non-dispensing nozzle rate is the average of the nozzles used for recording the first and second inks.

[0197] A: Non-spray nozzles account for less than 1% of all nozzles.

[0198] B: Non-spraying nozzles account for 2-3% of all full nozzles.

[0199] C: Non-spraying nozzles account for 4-5% of all nozzles.

[0200] D: Non-spraying nozzles account for more than 6% of all nozzles.

[0201] The following table shows the evaluation results.

[0202] Table 3

[0203]

[0204] Table 4

[0205]

[0206] Table 5

[0207]

[0208] Table 6

[0209]

[0210] Table 7

[0211] Bk C Y M Diethylene glycol ethyl methyl ether 54.4 53.4 54.4 54.4 Diethylene glycol diethyl ether 30 30 30 30 γ-Butyrolactone 10 10 10 10 BYK-340 0.1 0.1 0.1 0.1 SOLBIN CL 2 2 2 2 carbon black 2 Pigment Blue 15:3 2.5 Pigment Yellow 155 2 Pigment Red 122 2 dispersant 1.5 2 1.5 1.5 total 100 100 100 100

[0212] As described above, it can be seen that in Comparative Examples 1 to 8, which use only one of the first composition or the second composition, the color reproduction range is narrowed. On the other hand, it can be seen that in Comparative Examples 9 to 11, which do not involve irradiating each composition with radiation within 1 second of the landing delay to cure it, bleeding occurs, and the image quality of the obtained recordings deteriorates.

[0213] In contrast, in the embodiment where both the first and second compositions were used, and a process was performed where each composition was irradiated with radiation within one second after application to cure it, a balance was achieved between color reproduction range and bleeding suppression. Furthermore, as in Examples 1-16, the color reproduction range was expanded by combining the first and second compositions, and as in Example 17, the color reproduction range was further expanded by using other color compositions. On the other hand, as in Example 18, a glossy finish was achieved by using transparent ink. Moreover, as in Examples 25 and 26, adjusting the irradiation energy or peak intensity to perform temporary curing with weaker irradiation further improved the color reproduction range, ejection stability, and gloss. Furthermore, the invention was also found to be useful in Examples 27-29, which are examples of line printers.

[0214] It should be noted that the solvent-based ink group shown in Table 7 was used, and the same evaluation as the color reproduction range evaluation described above was performed. As the evaluation pattern, the same recording apparatus as used in recording method one was used, and the ink was adhered to the same recording medium. However, during ink adhesion, a pressure plate heater was used to heat the surface temperature of the recording medium to 40°C. After ink adhesion was completed, the recording medium was discharged from the recording apparatus, heated to 50°C for 30 minutes, and then left at room temperature for one day. No irradiation was performed. Colorimetric measurements were performed on the evaluation pattern prepared in this way, as described above. This ink group does not contain an ink equivalent to the second ink, and in this respect is similar to ink group S19 described above. However, the color reproduction range is C. However, it is not a radiation-curable composition, and it is not a composition used after curing by irradiation. Therefore, when using a radiation-curable composition, an excellent color reproduction range can be obtained, and based on this, the present invention is necessary.

[0215] The present invention may also be configured as follows.

[0216] (1) An inkjet method comprising: a step of ejecting a first composition of radiation curable type with a hue angle of -50 to -5° from an inkjet head; a step of ejecting a second composition of radiation curable type with a hue angle of 5 to 50° from an inkjet head; and an irradiation step of irradiating the ejected first composition with radiation within 1 second after landing, and irradiating the ejected second composition with radiation within 1 second after landing, so as to cure the composition.

[0217] (2) The inkjet method described in (1) further comprises: a step of ejecting a radiation-curable cyan composition from an inkjet head; and a step of ejecting a radiation-curable yellow composition from an inkjet head.

[0218] (3) In the inkjet method described in (1) or (2), the difference in hue angle between the first composition and the second composition is 10 to 35°.

[0219] (4) In any one of the inkjet methods described in (1) to (3), the hue angle of the first composition is -30 to -10°, and the hue angle of the second composition is 10 to 40°.

[0220] (5) In any one of the inkjet methods described in (1) to (4), the first composition comprises one or more pigments selected from the group consisting of PR31, 122, 202, 207, 209, 147, 269, PV32 and 19, and the second composition comprises one or more pigments selected from the group consisting of PR166, 168, 149, 177, 179, 254, 255, 264, 242 and 224.

[0221] (6) In any one of (2) to (5) the inkjet method further comprises a step of ejecting a radiation-curable third composition from an inkjet head, wherein the hue angle is larger than that of the second composition and lower than that of the yellow composition.

[0222] (7) In any one of the inkjet printing methods described in (1) to (6), the radiation energy of the irradiation process is 5 to 2000 mJ / cm². 2 .

[0223] (8) In any one of the inkjet methods described in (1) to (7), the peak intensity of the radiation during the irradiation process is 150 mW / cm². 2 above.

[0224] (9) In any of the inkjet methods described in (1) to (8), an LED is used as the radiation source for the radiation in the irradiation process.

[0225] (10) In any one of (1) to (9) the inkjet method further comprises: after the irradiation step and after 1 second after each composition has landed, irradiating each composition with radiation.

[0226] (11) In any of the inkjet methods described in (1) to (10), the first composition and the second composition comprise 2-(2-ethyleneoxyethoxy)ethyl acrylate.

[0227] (12) In any one of the inkjet methods described in (1) to (11), the pigment content in the first composition is 2% by mass or less relative to the total amount of the first composition, and the pigment content in the second composition is 2% by mass or less relative to the total amount of the second composition.

[0228] (13) In any one of (1) to (12) the inkjet method further comprises: a step of ejecting a radiation-curable transparent composition from an inkjet head.

[0229] (14) An inkjet apparatus comprising: an inkjet head for performing the inkjet method described in any one of [1] to

[13] ; and a radiation source.

Claims

1. An inkjet printing method, characterized in that, have: The process of ejecting a first composition of radiation-curable type with a hue angle of -50 to -5° from an inkjet head; The process of ejecting a second composition of radiation-curable type with a hue angle of 5 to 50° from an inkjet head; The process of ejecting a radiation-cured cyan composition from an inkjet head; The process of ejecting a radiation-curable yellow composition from an inkjet head; The process of ejecting a radiation-curable third composition from an inkjet head, which has a hue angle greater than that of the second composition and lower than that of the yellow composition; as well as The irradiation process involves irradiating the first ejected composition with radiation within one second after impact, irradiating the second ejected composition with radiation within one second after impact, and irradiating the third ejected composition with radiation within one second after impact, to solidify the compositions. In the inkjet method, An LED is used as the radiation source for the irradiation process. The first composition, the second composition, and the third composition all comprise an acylphosphine oxide compound as a polymerization initiator. The first composition, the second composition, and the third composition are non-aqueous compositions containing 60-98% by mass of a polymeric compound relative to the total amount of ink. The acylphosphine oxide compound is one or more of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

2. The inkjet method according to claim 1, characterized in that, The difference in hue angle between the first composition and the second composition is 10~35°.

3. The inkjet method according to claim 1, characterized in that, The hue angle of the first composition is -30 to -10°. The hue angle of the second composition is 10~40°.

4. The inkjet method according to claim 1, characterized in that, The first composition comprises one or more pigments selected from the group consisting of PR31, 122, 202, 207, 209, 147, 269, PV32, and 19. The second composition comprises one or more pigments selected from the group consisting of PR166, 168, 149, 177, 179, 254, 255, 264, 242 and 224.

5. The inkjet method according to claim 1, characterized in that, The radiation energy during the irradiation process is 5~2000 mJ / cm². 2 .

6. The inkjet method according to claim 1, characterized in that, The inkjet method also has the following characteristics: The process of further irradiating each composition with radiation after the irradiation process and after each composition has been in place for 1 second.

7. The inkjet method according to claim 1, characterized in that, The first composition and the second composition comprise 2-(2-ethyleneoxyethoxy)ethyl acrylate.

8. The inkjet method according to claim 1, characterized in that, The pigment content in the first composition is less than 2% by mass relative to the total amount of the first composition. The pigment content in the second composition is less than 2% by mass relative to the total amount of the second composition.

9. The inkjet method according to claim 1, characterized in that, The inkjet method also has the following characteristics: The process of ejecting a radiation-curable transparent composition from an inkjet head.

10. The inkjet method according to claim 1, characterized in that, The peak wavelength of the LED is 350~420nm.

11. The inkjet method according to claim 1, characterized in that, The inkjet method comprises: An irradiation process in which the cyan composition is sprayed with radiation within 1 second after landing, and the yellow composition is sprayed with radiation within 1 second after landing to solidify the composition.

12. The inkjet method according to claim 1, characterized in that, The peak intensity of the radiation during the irradiation process is 1500 mW / cm². 2 above.

13. An inkjet device, characterized in that, have: The inkjet head performs the inkjet method according to any one of claims 1 to 12; and Radiation source.

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