Ink set and image recording method

Abstract

The present invention provides an ink set and an image recording method, wherein the ink set can obtain an image recording material having excellent adhesion and bending resistance when recording an image using a colored ink and a white ink. The ink set comprises: a colored ink containing a colored pigment, a first pigment dispersant, and water, wherein the colored pigment is at least one selected from the group consisting of a color pigment and a black pigment; and a white ink containing a white pigment, a second pigment dispersant, and water, wherein the first pigment dispersant is a random polymer and the second pigment dispersant is a block polymer.

Description

Technical Field

[0001] The present invention relates to an ink set and an image recording method. Background Art

[0002] Conventionally, various studies have been conducted on image recording using a plurality of inks.

[0003] For example, Patent Document 1 describes an ink set comprising: a reaction liquid containing a coagulant; a first ink containing a colorant; and a second ink containing a colorant. The ink set is used for recording on a non-absorbent recording medium or a low-absorbent recording medium, and the reaction liquid, the first ink, and the second ink are sequentially overlapped on the recording medium for use.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-178131 Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] When an image is recorded using a colored ink and a white ink, the obtained image record may be required to have adhesion and bending resistance.

[0009] The present invention has been made in view of such circumstances, and an object of the embodiments of the present invention is to provide an ink set and an image recording method that can obtain an image recording material having excellent adhesion and bending resistance when recording an image using a colored ink and a white ink.

[0010] Means for solving technical problems

[0011] The present invention includes the following aspects.

[0012] <1> An ink set comprises: a color ink containing a color pigment, a first pigment dispersant and water, wherein the color pigment is at least one selected from the group consisting of a color pigment and a black pigment; and a white ink containing a white pigment, a second pigment dispersant and water, wherein the first pigment dispersant is a random polymer and the second pigment dispersant is a block polymer.

[0013] <2> according to <1> The ink set, wherein when the glass transition temperature of the first pigment dispersant is set to Tgc and the n glass transition temperatures of the second pigment dispersant are set to Tg1 to Tgn, respectively, the maximum value of the absolute value of the difference between Tgc and each of Tg1 to Tgn is greater than 50°C.

[0014] <3> according to <1> or <2> The ink set, wherein when the glass transition temperature of the first pigment dispersant is set to Tgc and the n glass transition temperatures of the second pigment dispersant are set to Tg1 to Tgn, respectively, the minimum value of the absolute value of the difference between Tgc and each of Tg1 to Tgn is greater than 5°C.

[0015] <4> according to <2> or <3> In the ink set, Tgc represents a value lower than all of Tg1 to Tgn.

[0016] <5> according to <2> to <4> The ink set described in any one of the preceding claims, wherein Tgc is 150° C. or lower, and the highest temperature among Tg1 to Tgn is 200° C. or lower.

[0017] <6> according to <1> to <5> The ink set described in any one of the preceding claims, wherein the first pigment dispersant and the second pigment dispersant are both polymers containing 30% by mass or more of a structural unit derived from a monomer having a hydrocarbon group having 4 or more carbon atoms, based on the total amount of the polymer.

[0018] <7> according to <1> to <6> The ink set described in any one of the preceding claims, wherein the second pigment dispersant is a polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group having 6 or more carbon atoms.

[0019] <8> according to <1> to <7> In any one of the above ink sets, an absolute value of a difference between number average molecular weights of the first pigment dispersant and the second pigment dispersant is 10,000 or more.

[0020] <9> according to <1> to <8> In any one of the above ink sets, the number average molecular weight of the first pigment dispersant is larger than the number average molecular weight of the second pigment dispersant.

[0021] <10> according to <1> to <9> The ink set described above further comprises a pre-treatment liquid containing a coagulant.

[0022] <11> An image recording method, using <1> to <10> The ink set as described above includes the steps of: applying a colored ink to an impermeable substrate by inkjet recording; and applying a white ink to a colored ink film formed by applying the colored ink by inkjet recording.

[0023] Effects of the Invention

[0024] According to the present invention, there are provided an ink set and an image recording method capable of obtaining an image recorded material having excellent adhesion and bending resistance when recording an image using a colored ink and a white ink. DETAILED DESCRIPTION

[0025] Hereinafter, the ink set and the image recording method of the present invention will be described in detail.

[0026] In the present specification, a numerical range expressed using "to" indicates a range including the numerical values ​​described before and after "to" as the minimum value and the maximum value, respectively.

[0027] In the numerical ranges recorded in this specification, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical ranges recorded in this specification, the upper limit or lower limit recorded in a certain numerical range can also be replaced by the value shown in the embodiments.

[0028] In the present specification, when a plurality of substances corresponding to each component are present in a composition, unless otherwise specified, the amount of each component in the composition means the total amount of the plurality of substances present in the composition.

[0029] In the present specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0030] In the present specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0031] In this specification, "image" means the entire film formed by applying ink, and "image recording" means the formation of an image (ie, film).

[0032] Furthermore, the concept of "image" in this specification also includes a solid image.

[0033] In this specification, "(meth)acrylate" is a concept including both acrylate and methacrylate. Also, "(meth)acrylic acid" is a concept including both acrylic acid and methacrylic acid.

[0034] [Ink set]

[0035] The ink set of the present invention comprises: a colored ink containing a colored pigment, a first pigment dispersant and water, wherein the colored pigment is at least one selected from the group consisting of a color pigment and a black pigment; and a white ink containing a white pigment, a second pigment dispersant and water, wherein the first pigment dispersant is a random polymer and the second pigment dispersant is a block polymer.

[0036] For example, Patent Document 1 describes an ink set in which a reaction liquid, a first ink, and a second ink are sequentially applied and stacked on a recording medium. However, Patent Document 1 does not pay attention to the structure of a resin dispersant for dispersing a pigment.

[0037] In contrast, in the ink set of the present invention, the first pigment dispersant contained in the coloring ink is a random polymer, and the second pigment dispersant contained in the white ink is a block polymer. The polymer forms of the first pigment dispersant contained in the coloring ink and the second pigment dispersant contained in the white ink are different from each other, so it is speculated that the degree of film formation when forming the ink film will be different between the surface and the inside of the ink film. Therefore, it is believed that the elongation at break of the ink film is large, and the obtained image record has excellent bending resistance. In addition, since the pigment dispersant contained in the coloring ink is a random polymer, it is speculated that the pigment dispersant will be oriented at the interface between the coloring ink film and the white ink film. Therefore, it is believed that the interaction between the coloring ink film and the white ink film is strong, and the obtained image record has excellent adhesion.

[0038] Hereinafter, each component contained in the colored ink and the white ink constituting the ink set of the present invention will be described.

[0039] <Coloring ink>

[0040] In the present invention, the coloring ink contains a coloring pigment, a pigment dispersant, and water, and the coloring pigment is at least one selected from the group consisting of a color pigment and a black pigment.

[0041] (Coloring Pigments)

[0042] The coloring ink contains a coloring pigment, which is at least one selected from the group consisting of a color pigment and a black pigment. The coloring pigment contained in the coloring ink may be only one kind, or may be two or more kinds. That is, the coloring pigment contained in the coloring ink may be one or more color pigments, may be one or more black pigments, or may be a combination of one or more color pigments and one or more black pigments.

[0043] The color pigment is any pigment that exhibits color, and its type is not particularly limited. The color pigment refers to a color with a hue.

[0044] The color pigment is not particularly limited, and examples thereof include cyan pigments, magenta pigments, yellow pigments, blue pigments, red pigments, green pigments, orange pigments, and violet pigments.

[0045] Specific examples of color pigments include organic pigments such as azo pigments, disazo pigments, condensed disazo pigments, phthalocyanine pigments, quinacridone pigments, quinacridonequinone pigments, anthraquinone pigments, aminoanthraquinone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perindole pigments, perylene pigments, isoindoline pigments, isoindolinone pigments, isovionanthrone pigments, benzimidazolone pigments, indanthrone pigments, triarylcarbonium pigments, and diketopyrrolopyrrole pigments.

[0046] More specifically, examples of color pigments include:

[0047] Perylene pigments such as CI Pigment Red 190, CI Pigment Red 224, CI Pigment Violet 29;

[0048] CI Pigment Orange 43, CI Pigment Red 194 and other violacetone pigments;

[0049] Quinacridone pigments such as CI Pigment Violet 19, CI Pigment Violet 42, CI Pigment Red 122, CI Pigment Red 192, CI Pigment Red 202, CI Pigment Red 207, CI Pigment Red 209;

[0050] Quinacridone quinone pigments such as CI Pigment Red 206, CI Pigment Orange 48, CI Pigment Orange 49;

[0051] Anthraquinone pigments such as CI Pigment Yellow 147;

[0052] CI Pigment Red 168 and other anthraquinone pigments;

[0053] CI Pigment Brown 25, CI Pigment Violet 32, CI Pigment Orange 36, CI Pigment Yellow 120, CI Pigment Yellow 180, Pigment Yellow 181, CI Pigment Orange 62, CI Pigment Red 185 and other benzimidazolone pigments;

[0054] Condensed disazo pigments such as CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 95, CI Pigment Yellow 128, CI Pigment Yellow 166, CI Pigment Orange 34, CI Pigment Orange 13, CI Pigment Orange 31, Pigment Red 144, Pigment Red 166, Pigment Red 220, CI Pigment Red 221, CI Pigment Red 242, Pigment Red 248, CI Pigment Red 262, CI Pigment Brown 23;

[0055] Disazo pigments such as CI Pigment Yellow 13, CI Pigment Yellow 83, CI Pigment Yellow 188;

[0056] Azo pigments such as CI Pigment Red 187, CI Pigment Red 170, CI Pigment Yellow 74, CI Pigment Yellow 150, CI Pigment Red 48, Pigment Red 53, CI Pigment Orange 64, CI Pigment Red 247;

[0057] Indanthrone pigments such as CI Pigment Blue 60;

[0058] Phthalocyanine pigments such as CI Pigment Green 7, CI Pigment Green 36, CI Pigment Green 37, CI Pigment Green 58, CI Pigment Blue 16, CI Pigment Blue 75, Pigment Blue 15;

[0059] CI Pigment Blue 56, CI Pigment Blue 61 and other triarylcarbonium pigments;

[0060] Dioxazine pigments such as CI Pigment Violet 23 and CI Pigment Violet 37;

[0061] Aminoanthraquinone pigments such as CI Pigment Red 177;

[0062] Diketopyrrolopyrrole pigments such as CI Pigment Red 254, CI Pigment Red 255, CI Pigment Red 264, CI Pigment Red 272, CI Pigment Orange 71, and CI Pigment Orange 73;

[0063] CI Pigment Red 88 and other thioindigo pigments;

[0064] Isoindoline pigments such as CI Pigment Yellow 139 and Pigment Orange 66; Isoindoline ketone pigments such as Pigment Yellow 109 and CI Pigment Orange 61;

[0065] Pyranthrone pigments such as CI Pigment Orange 40 and CI Pigment Red 216;

[0066] And isovioletanthrone pigments such as CI Pigment Violet 31.

[0067] The black pigment may be any pigment that exhibits black color, and the type thereof is not particularly limited. Examples of the black pigment include carbon black and titanium black.

[0068] The average particle size of the color pigment and the black pigment is preferably 10nm to 200nm, more preferably 10nm to 150nm, and further preferably 10nm to 110nm. If the average particle size is less than 200nm, the color reproducibility is good, and further, when the image is recorded using an inkjet recording method, the jetting stability is good. On the other hand, if the average particle size is more than 10nm, the light resistance is good. In addition, the particle size distribution of the pigment can be any one of a wide particle size distribution and a monodisperse particle size distribution. In addition, the average particle size and particle size distribution of the pigment are obtained as follows: the volume average particle size is measured by a dynamic light scattering method using a particle size distribution measuring device (for example, Nikkiso Co., Ltd. product name "NANOTRAC UPA-EX150"). In addition, when the pigment is coated with a pigment dispersant, the average particle size of the pigment represents the average particle size of the pigment coated with the pigment dispersant.

[0069] The content of the color pigment is preferably 1% by mass to 15% by mass, and more preferably 2% by mass to 10% by mass, based on the total amount of the color ink, from the viewpoint of image density and ejection stability.

[0070] (First Pigment Dispersant)

[0071] The color ink of the present invention contains a first pigment dispersant. The first pigment dispersant is a random polymer. In the present invention, a polymer refers to a compound having a number average molecular weight of 1,000 or more.

[0072] In the present invention, the number average molecular weight and the weight average molecular weight represent the values ​​measured by gel permeation chromatography (GPC). When measuring by gel permeation chromatography (GPC), HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) is used as a measuring device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mmID×15 cm, manufactured by Tosoh Corporation) are used as columns, and THF (tetrahydrofuran) is used as an eluent. In addition, the measurement is performed using an RI detector, wherein the sample concentration is set to 0.45% by mass, the flow rate is set to 0.35 ml / min, the sample injection amount is set to 10 μl, and the measurement temperature is set to 40°C. The calibration curve was prepared based on eight samples of "TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0073] A random polymer is also called a random copolymer, and refers to a polymer having structural units derived from at least two monomers, and the order of the structural units is irregular.

[0074] In the present invention, the pigment dispersant has a function of dispersing the pigment. The pigment dispersant is adsorbed on the surface of the pigment and covers at least a part of the surface of the pigment, thereby being able to disperse the pigment in water.

[0075] The random polymer as the first pigment dispersant preferably contains: a structural unit derived from a hydrophobic monomer; and a structural unit derived from a monomer containing an anionic group (hereinafter referred to as "anionic group-containing monomer"). From the viewpoint of dispersion stability, the content ratio (a:b) of the structural unit a derived from the hydrophobic monomer and the structural unit b derived from the anionic group-containing monomer is preferably 8:1 to 1:1.

[0076] The structural unit derived from the hydrophobic monomer contained in the random polymer may be only one kind or two or more kinds.

[0077] The structural unit derived from the anionic group-containing monomer contained in the random polymer may be only one kind or two or more kinds.

[0078] The hydrophobic monomer is preferably a monomer having a hydrocarbon group with 4 or more carbon atoms, more preferably an ethylenically unsaturated monomer having a hydrocarbon group with 4 or more carbon atoms, and further preferably a (meth)acrylate having a hydrocarbon group with 4 or more carbon atoms. The hydrocarbon group may be any one of a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. The number of carbon atoms of the hydrocarbon group is more preferably 4 or more, and more preferably 6 or more. The upper limit of the number of carbon atoms of the hydrocarbon group is, for example, 12.

[0079] Examples of (meth)acrylates having a chain hydrocarbon group with 4 or more carbon atoms include n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and lauryl (meth)acrylate. The carbon number of the chain hydrocarbon group is more preferably 6 or more, and further preferably 8 or more. Among them, the ethylenically unsaturated monomer having a chain hydrocarbon group with 4 or more carbon atoms is preferably lauryl (meth)acrylate.

[0080] Examples of the (meth)acrylate having an alicyclic hydrocarbon group having 4 or more carbon atoms include (bicyclo〔2.2.1〕heptyl-2-(meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 3-methyl-1-adamantyl (meth)acrylate, 3,5-dimethyl-1-adamantyl (meth)acrylate, 3-ethyladamantyl (meth)acrylate, 3-methyl-5-ethyl-1-adamantyl (meth)acrylate, 3,5,8-triethyl-1-adamantyl (meth)acrylate, 3,5-dimethyl-8-ethyl-1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, The alicyclic hydrocarbon group preferably has 6 or more carbon atoms. Among them, the ethylenically unsaturated monomer having an alicyclic hydrocarbon group having 4 or more carbon atoms is preferably isobornyl (meth)acrylate or cyclohexyl (meth)acrylate.

[0081] Examples of the (meth)acrylate having an aromatic hydrocarbon group having 4 or more carbon atoms include styrene, 2-naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate. Among them, the ethylenically unsaturated monomer having an aromatic hydrocarbon group having 4 or more carbon atoms is preferably styrene.

[0082] Examples of the anionic group in the anionic group-containing monomer include a carboxyl group, a salt of a carboxyl group, a sulfonic group, a salt of a sulfonic group, a phosphoric acid group, a salt of a phosphoric acid group, a phosphonic acid group, and a salt of a phosphonic acid group.

[0083] Examples of the counter ion in the salt include alkali metal ions such as sodium ion, potassium ion, and lithium ion; alkaline earth metal ions such as calcium ion and magnesium ion; and ammonium ion.

[0084] Among them, the anionic group is preferably a carboxyl group or a salt of a carboxyl group.

[0085] Examples of the carboxyl group-containing monomer include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0086] From the viewpoint of dispersion stability, the anionic group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid.

[0087] The mixing ratio of the color pigment to the first pigment dispersant is preferably 1:0.06 to 1:3, more preferably 1:0.125 to 1:2, and even more preferably 1:0.125 to 1:1.5 on a mass basis.

[0088] As a dispersing device for dispersing the pigment, a known dispersing device can be used, and examples thereof include a ball mill, a sand mill, a bead mill, a roll mill, a jet mill, a paint shaker, an attritor, an ultrasonic disperser, and a disperser.

[0089] (water)

[0090] In the present invention, the coloring ink contains water. The content of water is not particularly limited, and is, for example, 40% by mass to 70% by mass.

[0091] (resin particles)

[0092] In the present invention, from the viewpoint of obtaining the scratch resistance of the image, the color ink preferably contains at least one type of resin particles. The color ink preferably contains resin particles in addition to the pigment dispersant, and the resin particles are particles composed of a resin.

[0093] In particular, if the color ink contains resin particles, the image quality is improved when a pretreatment liquid is applied to the substrate in advance. When the color ink is applied to the substrate to which the pretreatment liquid is applied, the coagulant contained in the pretreatment liquid contacts the resin particles contained in the color ink, making the dispersion of the resin particles unstable, thereby increasing the viscosity of the color ink. As a result, the color ink is fixed on the substrate, and the image quality of the recorded image is improved.

[0094] The resin constituting the resin particles is preferably a water-insoluble polymer. The "water-insoluble" in the water-insoluble polymer means a property that the amount of the water-insoluble polymer dissolved in 100 g of distilled water at 25°C is less than 2 g.

[0095] The resin particles preferably include at least one of particles composed of an acrylic resin (hereinafter referred to as “acrylic resin particles”) and particles composed of a urethane resin (hereinafter also referred to as “urethane resin particles”), and more preferably include acrylic resin particles.

[0096] The resin particles are preferably self-dispersible resin particles.

[0097] Examples of the self-dispersible resin particles include resin particles described in paragraphs 0062 to 0076 of JP-A-2016-188345 and paragraphs 0109 to 0140 of International Publication No. 2013 / 180074.

[0098] The resin in the resin particles is preferably an acrylic resin containing a structural unit derived from a (meth)acrylate having an aromatic ring structure or an alicyclic structure, a structural unit derived from (meth)acrylic acid, and a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms.

[0099] The (meth)acrylate having an alicyclic structure is preferably an alkyl (meth)acrylate having a cycloalkyl group having 3 to 10 carbon atoms, more preferably at least one selected from the group consisting of cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate and dicyclopentanyl (meth)acrylate, and further preferably at least one selected from the group consisting of isobornyl (meth)acrylate, adamantyl (meth)acrylate and dicyclopentanyl (meth)acrylate.

[0100] The (meth)acrylate having an aromatic ring structure is preferably phenoxyethyl (meth)acrylate or benzyl (meth)acrylate.

[0101] Examples of the resin in the resin particles include phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (50 / 45 / 5), phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (30 / 35 / 29 / 6), phenoxyethyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (50 / 44 / 6), phenoxyethyl acrylate / methyl methacrylate / ethyl acrylate / acrylic acid copolymer (30 / 55 / 10 / 5), benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (35 / 59 / 6), Styrene / phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (10 / 50 / 35 / 5), Benzyl acrylate / methyl methacrylate / acrylic acid copolymer (55 / 40 / 5), Phenoxyethyl methacrylate / benzyl acrylate / methacrylic acid copolymer (45 / 47 / 8), Styrene / phenoxyethyl acrylate / butyl methacrylate / acrylic acid copolymer (5 / 48 / 40 / 7), Benzyl methacrylate / isobutyl methacrylate / cyclohexyl methacrylate / methacrylic acid copolymer (35 / 30 / 30 / 5), Phenoxy acrylate Ethyl Acrylate / Methyl Methacrylate / Butyl Acrylate / Methacrylic Acid Copolymer (12 / 50 / 30 / 8), Benzyl Acrylate / Isobutyl Methacrylate / Acrylic Acid Copolymer (93 / 2 / 5), Methyl Methacrylate / Methoxyethyl Acrylate / Benzyl Methacrylate / Acrylic Acid Copolymer (44 / 15 / 35 / 6), Styrene / Butyl Acrylate / Acrylic Acid Copolymer (62 / 35 / 3), Methyl Methacrylate / Phenoxyethyl Acrylate / Acrylic Acid Copolymer (45 / 51 / 4), Methyl Methacrylate / Isobornyl Methacrylate / Methacrylic Acid Copolymer (20 / 72 / 8), methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (40 / 52 / 8), methyl methacrylate / isobornyl methacrylate / methacrylic acid copolymer (48 / 42 / 10), methyl methacrylate / isobornyl methacrylate / dicyclopentyl methacrylate / methacrylic acid copolymer (20 / 62 / 10 / 8), methyl methacrylate / dicyclopentyl methacrylate / methacrylic acid copolymer (20 / 72 / 8) and methyl methacrylate / isobornyl methacrylate / methacrylic acid / methacrylic acid copolymer (70 / 20 / 5 / 5). In addition, the mass ratio of the structural unit derived from the monomer is shown in the brackets.

[0102] The acid value of the resin in the resin particles is preferably 25 mgKOH / g to 100 mgKOH / g, more preferably 30 mgKOH / g to 90 mgKOH / g, and even more preferably 35 mgKOH / g to 80 mgKOH / g.

[0103] The weight average molecular weight of the resin in the resin particles is preferably 1,000 to 300,000, more preferably 2,000 to 200,000, and further preferably 5,000 to 100,000.

[0104] From the viewpoint of spraying stability, the average particle size of the resin particles is preferably 1 nm to 200 nm, more preferably 3 nm to 200 nm, and further preferably 5 nm to 50 nm. In addition, the average particle size of the resin particles is obtained as follows: the volume average particle size is measured by a dynamic light scattering method using a particle size distribution measuring device (e.g., Nikkiso Co., Ltd. product name "NANOTRAC UPA-EX150").

[0105] When the color ink contains resin particles, the content of the resin particles is preferably 0.1% to 15% by mass, more preferably 0.5% to 10% by mass, further preferably 1% to 8% by mass, and further preferably 2% to 5% by mass, relative to the total amount of the color ink.

[0106] (Organic Solvent)

[0107] From the viewpoint of improving ejection stability, the colored ink preferably contains at least one organic solvent.

[0108] Examples of the organic solvent include glycerol, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and alkanediols (polyols) such as 1,3-butanediol and 2,3-butanediol;

[0109] Alkyl alcohols with 1 to 4 carbon atoms, such as ethanol, methanol, butanol, propanol, and isopropanol;

[0110] Glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol monoethyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-tert-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol monoisopropyl ether and tripropylene glycol monomethyl ether.

[0111] The content of the organic solvent is preferably 5% by mass to 60% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 15% by mass to 30% by mass, based on the total amount of the colored ink.

[0112] (Surfactant)

[0113] From the viewpoint of improving ejection stability, the colored ink may contain at least one surfactant.

[0114] As the surfactant, there can be mentioned the surfactants described in Japanese Patent Application Laid-Open No. 62-173463 and Japanese Patent Application Laid-Open No. 62-183457. Also, as the surfactant, for example, there can be mentioned anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, fatty acid salts, etc.; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycol, polyoxyethylene-polyoxypropylene block copolymers, etc.; and cationic surfactants such as alkylamine salts and quaternary ammonium salts. Also, the surfactant can be a fluorine-based surfactant or a silicone-based surfactant.

[0115] In the present invention, from the viewpoint of further suppressing cracks in the recorded image, the surfactant preferably contains a nonionic surfactant. Among them, the nonionic surfactant is preferably an acetylene glycol derivative (acetylene glycol-based surfactant).

[0116] Examples of acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol. Examples of commercially available products include E series such as OLFINE E1010 and E1020 from Nissin Chemical Industry Co., Ltd.

[0117] The content of the surfactant is preferably 0.01% by mass to 4.0% by mass, more preferably 0.05% by mass to 2.0% by mass, and even more preferably 0.1% by mass to 1.0% by mass, based on the total amount of the colored ink.

[0118] (additive)

[0119] The colored ink may contain additives such as a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and a basic compound as required.

[0120] (physical properties)

[0121] From the viewpoint of improving ejection stability, the pH of the colored ink is preferably 7 to 10, more preferably 7.5 to 9.5. The pH is measured at 25° C. using a pH meter, for example, a pH meter manufactured by DKK-TOA CORPORATION (model “HM-31”).

[0122] The viscosity of the coloring ink is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, further preferably 2 mPa·s to 15 mPa·s, and further preferably 3 mPa·s to 10 mPa·s. The viscosity is measured at 25° C. using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0123] The surface tension of the coloring ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 30 mN / m to 45 mN / m. The surface tension is measured at 25° C. using a surface tensiometer, for example, using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”) by a plate method.

[0124] <White ink>

[0125] In the present invention, the white ink contains a white pigment, a second pigment dispersant, and water.

[0126] (white pigment)

[0127] White pigments are white pigments, and the types are not particularly limited. White means a color that does not absorb a specific wavelength or absorbs less of a specific wavelength. Examples of white pigments include inorganic pigments such as titanium oxide, strontium titanate, barium titanate, zinc oxide, magnesium oxide, zirconium oxide, aluminum oxide, barium sulfate, silicon dioxide, talc, mica, aluminum hydroxide, calcium silicate, aluminum silicate, and zinc sulfide. White pigments are preferably particles having titanium atoms, and more preferably titanium oxide.

[0128] The average particle size of the white pigment is preferably 10nm to 550nm, more preferably 100nm to 450nm, and further preferably 150nm to 400nm. If the average particle size is less than 550nm, the color reproducibility is good, and further, when the image is recorded using an inkjet recording method, the jetting stability is good. On the other hand, if the average particle size is more than 10nm, the light resistance is good. In addition, the particle size distribution of the pigment can be any one of a wide particle size distribution and a monodisperse particle size distribution. In addition, the average particle size and particle size distribution of the pigment are obtained as follows: the volume average particle size is measured by a dynamic light scattering method using a particle size distribution measuring device (for example, Nikkiso Co., Ltd. product name "NANOTRACUPA-EX150"). In addition, when the pigment is coated with a pigment dispersant, the average particle size of the pigment represents the average particle size of the pigment coated with the pigment dispersant.

[0129] From the viewpoint of image density and ejection stability, the content of the white pigment is preferably 5% by mass to 20% by mass, and more preferably 8% by mass to 15% by mass, based on the total amount of the colored ink.

[0130] (Second Pigment Dispersant)

[0131] The white ink of the present invention contains a second pigment dispersant. The second pigment dispersant is a block polymer.

[0132] A block polymer, also called a block copolymer, is a copolymer in which at least two polymers are bonded in a molecule.

[0133] Whether the polymer contained in the white ink is a block polymer can be determined, for example, by the following method. First, the polymer is separated from the white ink using a separation method such as solvent extraction. The separated polymer is analyzed using various analysis methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermal analysis, and physical properties such as glass transition temperature are measured to comprehensively determine whether it is a block polymer.

[0134] For example, a case where the block polymer contained in the white ink has two or more glass transition temperatures can also be cited as a preferred embodiment of the above determination method.

[0135] The block polymer as the second pigment dispersant preferably contains: a structural unit derived from a hydrophobic monomer; and a structural unit derived from a monomer containing an anionic group (hereinafter referred to as "anionic group-containing monomer"). From the viewpoint of dispersion stability, the content ratio (c:d) of the structural unit c derived from the hydrophobic monomer to the structural unit d derived from the anionic group-containing monomer is preferably 10:1 to 1:2.

[0136] The structural unit derived from the hydrophobic monomer contained in the block polymer may be only one kind or two or more kinds.

[0137] The structural unit derived from the anionic group-containing monomer contained in the block polymer may be only one kind or two or more kinds.

[0138] The hydrophobic monomer is preferably a monomer having a hydrocarbon group with 4 or more carbon atoms, more preferably an ethylenically unsaturated monomer having a hydrocarbon group with 4 or more carbon atoms, and further preferably a (meth)acrylate having a hydrocarbon group with 4 or more carbon atoms. The hydrocarbon group may be any one of a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. The number of carbon atoms of the hydrocarbon group is more preferably 4 or more, and more preferably 6 or more. The upper limit of the number of carbon atoms of the hydrocarbon group is, for example, 12.

[0139] The block polymer as the second pigment dispersant is preferably a polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group having 6 or more carbon atoms.

[0140] It is believed that the polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group with carbon atoms of 6 or more interacts strongly with the white pigment, and is therefore not easily separated from the surface of the white pigment. Therefore, if the second pigment dispersant is a polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group with carbon atoms of 6 or more, the white pigment will be fully coated with the second pigment dispersant, and the scratch resistance will be improved.

[0141] The anionic group is preferably a carboxyl group or a salt of a carboxyl group.

[0142] From the viewpoint of dispersion stability, the anionic group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid.

[0143] The mixing ratio of the white pigment to the second pigment dispersant is preferably 1:0.06 to 1:3, more preferably 1:0.125 to 1:2, and even more preferably 1:0.125 to 1:1.5 on a mass basis.

[0144] (water)

[0145] In the present invention, the white ink contains water. The content of water is not particularly limited, and is, for example, 40% by mass to 70% by mass.

[0146] (resin particles)

[0147] In the present invention, from the viewpoint of obtaining the scratch resistance of the image, the white ink preferably contains at least one type of resin particles. The white ink preferably contains resin particles in addition to the second pigment dispersant, and the resin particles are particles composed of a resin.

[0148] In particular, if the white ink contains resin particles, the image quality is improved when a pretreatment liquid is applied to the substrate in advance. When the white ink is applied to the substrate to which the pretreatment liquid is applied, the coagulant contained in the pretreatment liquid contacts the resin particles contained in the white ink, making the dispersion of the resin particles unstable, thereby increasing the viscosity of the white ink. As a result, the white ink is fixed on the substrate, and the image quality of the recorded image is improved.

[0149] Preferred embodiments of the resin particles contained in the white ink are the same as the preferred embodiments of the resin particles contained in the above-mentioned color ink.

[0150] When the white ink contains resin particles, the content of the resin particles is preferably 0.1% to 15% by mass, more preferably 0.5% to 10% by mass, further preferably 1% to 8% by mass, and further preferably 2% to 6% by mass, relative to the total amount of the white ink.

[0151] (Organic Solvent)

[0152] From the viewpoint of improving ejection stability, the white ink preferably contains at least one organic solvent.

[0153] Preferred embodiments of the organic solvent contained in the white ink are the same as the preferred embodiments of the organic solvent contained in the above-mentioned color ink.

[0154] The content of the organic solvent is preferably 5% by mass to 60% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 20% by mass to 35% by mass, based on the total amount of the white ink.

[0155] (Surfactant)

[0156] From the viewpoint of improving ejection stability, the white ink may contain at least one surfactant.

[0157] Preferred embodiments of the surfactant contained in the white ink are the same as the preferred embodiments of the surfactant contained in the above-mentioned color ink.

[0158] The content of the surfactant is preferably 0.01% by mass to 4.0% by mass, more preferably 0.05% by mass to 2.0% by mass, and even more preferably 0.1% by mass to 1.0% by mass, based on the total amount of the white ink.

[0159] (Additives) The white ink may contain additives such as a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and a basic compound as required.

[0160] (physical properties)

[0161] From the viewpoint of improving ejection stability, the pH of the white ink is preferably 7 to 10, more preferably 7.5 to 9.5. The pH is measured at 25° C. using a pH meter, for example, a pH meter manufactured by DKK-TOA CORPORATION (model “HM-31”).

[0162] The viscosity of the white ink is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, further preferably 2 mPa·s to 15 mPa·s, and further preferably 3 mPa·s to 10 mPa·s. The viscosity is measured at 25° C. using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0163] The surface tension of the white ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 30 mN / m to 45 mN / m. The surface tension is measured at 25° C. using a surface tensiometer, for example, using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”) by a plate method.

[0164] (Relationship between the first pigment dispersant and the second pigment dispersant)

[0165] In the ink set of the present invention, if the first pigment dispersant contained in the color ink and the second pigment dispersant contained in the white ink have a specific relationship, the adhesion and bending resistance of the image recorded using the ink set are further improved. The specific relationship is described in detail below.

[0166] -Glass transition temperature-

[0167] When the glass transition temperature of the first pigment dispersant is Tgc and the n glass transition temperatures of the second pigment dispersant are Tg1 to Tgn, the maximum value of the absolute value of the difference between Tgc and each of Tg1 to Tgn is preferably 50° C. or more.

[0168] The second pigment dispersant is a block polymer. In the case where the second pigment dispersant is, for example, an AB block polymer composed of an A block and a B block, the second pigment dispersant generally has two glass transition temperatures, namely, a glass transition temperature derived from the A block and a glass transition temperature derived from the B block. However, depending on the structure of the A block and the B block, sometimes only one glass transition temperature is present. In the case where the glass transition temperature of the second pigment dispersant is one, the absolute value of the difference between Tgc and Tg1, which are the glass transition temperatures of the first pigment dispersant, is preferably 50°C or more. In the case where the glass transition temperature of the second pigment dispersant is two or more, the absolute value of the difference between Tgc and each of Tg1 to Tgn is calculated, and the maximum value among the calculated values ​​is preferably 50°C or more.

[0169] If the maximum value is 50°C or more, the softness differs between the surface and the inside of the ink film, the elongation at break increases, and the bending resistance of the image recorded material obtained thereby further improves. From the viewpoint of further improving the bending resistance of the image recorded material obtained, the maximum value (the maximum value among the absolute values ​​of the differences between Tgc and Tg1 to Tgn when the glass transition temperature of the first pigment dispersant is Tgc and the n glass transition temperatures of the second pigment dispersant are Tg1 to Tgn, respectively) is more preferably 75°C or more, and further preferably 100°C or more. From the viewpoint of scratch resistance, the upper limit of the maximum value is, for example, 150°C or less, and preferably 125°C or less.

[0170] Furthermore, when the glass transition temperature of the first pigment dispersant is Tgc and the n glass transition temperatures of the second pigment dispersant are Tg1 to Tgn, the minimum value of the absolute value of the difference between Tgc and each of Tg1 to Tgn is preferably 5° C. or more. That is, the absolute value of the difference between Tgc and each of Tg1 to Tgn is preferably 5° C. or more.

[0171] When the minimum value is 5°C or more, the bending resistance of the obtained image recorded material is further improved. From the viewpoint of further improving the bending resistance of the obtained image recorded material, the minimum value is more preferably 20°C or more, further preferably 35°C or more, and particularly preferably 50°C or more.

[0172] From the viewpoint of scratch resistance, the upper limit of the minimum value is preferably 100° C. or lower, more preferably 65° C. or lower.

[0173] That is, when the glass transition temperature of the first pigment dispersant is Tgc and the n glass transition temperatures of the second pigment dispersant are Tg1 to Tgn, the absolute value of the difference between Tgc and each of Tg1 to Tgn is preferably 5°C to 150°C.

[0174] The glass transition temperature Tgc of the first pigment dispersant may be higher than the glass transition temperatures Tg1 to Tgn of the second pigment dispersant, or may be lower than the Tg1 to Tgn. When a white ink image is recorded after a color ink image is recorded on a substrate, Tgc is preferably lower than all of Tg1 to Tgn. By making the ink film formed on the side close to the substrate softer, the bending resistance of the obtained image record is further improved.

[0175] The glass transition temperature Tgc of the first pigment dispersant is preferably 150° C. or less, and the highest temperature among the n glass transition temperatures Tg1 to Tgn of the second pigment dispersant is preferably 200° C. or less. When Tgc is 150° C. or less and the highest temperature among Tg1 to Tgn is 200° C. or less, the bending resistance of the obtained image recorded material is further improved.

[0176] From the viewpoint of further improving the bending resistance of the obtained image recorded material, Tgc is more preferably 100° C. or lower, and the highest temperature among Tg1 to Tgn is more preferably 160° C. or lower.

[0177] As the glass transition temperature, the measured value is basically applicable. The glass transition temperature is measured using a differential scanning calorimeter (for example, a differential scanning calorimeter (product name "EXSTAR6220", manufactured by SII NanoTechnology Inc.)) under normal measurement conditions. However, in the case where it is difficult to measure due to decomposition of the material, the calculated value calculated by the following calculation formula is applicable. The glass transition temperature is calculated using the following formula 1.

[0178] 1 / Tg=∑(Xi / Tgi)…(1)

[0179] Here, the polymer to be calculated is a copolymer of n monomers with i=1 to n. Xi is the mass fraction of the i-th monomer (∑Xi=1), and Tgi is the glass transition temperature (absolute temperature) when the i-th monomer is a homopolymer. ∑ is the sum of i=1 to n. In addition, the value of the glass transition temperature (Tgi) when each monomer is a homopolymer is the value of Polymer Handbook (3rd Edition) (J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

[0180] -Polymer structure-

[0181] The first pigment dispersant and the second pigment dispersant are both preferably polymers containing 30% by mass or more of a structural unit derived from a monomer having a hydrocarbon group with a carbon number of 4 or more relative to the total amount of the polymer. The first pigment dispersant is a random polymer, and the second pigment dispersant is a block polymer, and the polymer structures of the two are different. However, if the first pigment dispersant and the second pigment dispersant are both polymers containing 30% by mass or more of a structural unit derived from a monomer having a hydrocarbon group with a carbon number of 4 or more, the hydrophobic interaction between the first pigment dispersant and the second pigment dispersant becomes stronger, and the adhesion between the colored ink film and the white ink film is improved. As a result, the adhesion of the obtained image record is improved.

[0182] From the viewpoint of further improving the adhesion of the obtained image recorded material, the content of the structural unit derived from the monomer having a hydrocarbon group with a carbon number of 4 or more is more preferably 45% by mass or more, and further preferably 60% by mass or more, relative to the total mass of the polymer. From the viewpoint of bending resistance, the upper limit of the content of the structural unit derived from the monomer having a hydrocarbon group with a carbon number of 4 or more can be, for example, 90% by mass or less, and preferably 80% by mass or less.

[0183] Furthermore, from the viewpoint of further improving the adhesion of the obtained image recorded material, the structural unit derived from the monomer having a hydrocarbon group with 4 or more carbon atoms is preferably a structural unit derived from a monomer having an alicyclic hydrocarbon group with 4 or more carbon atoms. Since the molecular freedom of the alicyclic hydrocarbon group is low, the hydrophobic interaction between the first pigment dispersant and the second pigment dispersant is further strengthened, and the adhesion between the colored ink film and the white ink film is improved. As a result, the adhesion of the obtained image recorded material is further improved.

[0184] -Number average molecular weight-

[0185] The absolute value of the difference between the number average molecular weights of the first pigment dispersant and the second pigment dispersant is preferably 10,000 or more. If the absolute value of the difference between the number average molecular weights is 10,000 or more, the interaction between the first pigment dispersant and the second pigment dispersant will not become too strong, and the bending resistance of the obtained image record will be further improved. The upper limit is not particularly set, and for example, it can be 50,000 or less, preferably 30,000 or less.

[0186] From the viewpoint of further improving the bending resistance of the obtained image recorded material, the number average molecular weight of the first pigment dispersant is preferably larger than the number average molecular weight of the second pigment dispersant.

[0187] The number average molecular weight of the first pigment dispersant is preferably 5,000 to 40,000, more preferably 10,000 to 30,000.

[0188] The number average molecular weight of the second pigment dispersant is preferably 5,000 to 30,000, more preferably 5,000 to 25,000, and even more preferably 8,000 to 20,000.

[0189] <Pretreatment solution>

[0190] The ink set of the present invention may further include a pretreatment liquid containing a coagulant in addition to the colored ink and the white ink.

[0191] (Agglutinating agent)

[0192] The coagulant is preferably at least one selected from the group consisting of a polyvalent metal compound, an organic acid, a metal complex, and a cationic polymer, and more preferably contains an organic acid.

[0193] -Multivalent Metal Compounds-

[0194] Examples of polyvalent metal compounds include salts of alkaline earth metals of Group 2 of the periodic table (e.g., magnesium and calcium), transition metals of Group 3 of the periodic table (e.g., lanthanum), metals of Group 13 of the periodic table (e.g., aluminum), and lanthanides (e.g., neodymium).

[0195] The salt of these metals is preferably a salt of an organic acid described later, a nitrate, a chloride or a thiocyanate.

[0196] Among them, the polyvalent metal compound is preferably a calcium salt or a magnesium salt of an organic acid (eg, formic acid, acetic acid, benzoic acid, etc.); a calcium salt or a magnesium salt of nitrate; calcium chloride, magnesium chloride, or a calcium salt or a magnesium salt of thiocyanate.

[0197] It is preferred that at least a part of the polyvalent metal compound is dissociated into polyvalent metal ions and counter ions in the pretreatment liquid.

[0198] -Organic Acids-

[0199] Examples of the organic acid include organic compounds having an acidic group.

[0200] Examples of the acidic group include a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfonic acid group, a sulfinic acid group, and a carboxyl group.

[0201] Among them, from the viewpoint of the aggregation speed of the ink, the acidic group is preferably a phosphoric acid group or a carboxyl group, and more preferably a carboxyl group.

[0202] It is preferred that at least a part of the acidic groups be dissociated in the pretreatment liquid.

[0203] Examples of the organic compound having a carboxyl group include (meth)acrylic acid, poly(meth)acrylic acid, acetic acid, formic acid, benzoic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, pyrrolidonecarboxylic acid, pyranonecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid and nicotinic acid.

[0204] Among them, from the viewpoint of the aggregation speed of the ink, the organic compound having a carboxyl group is preferably a divalent or higher-valent carboxylic acid (hereinafter also referred to as a polyvalent carboxylic acid), and more preferably a dicarboxylic acid.

[0205] Specifically, the polycarboxylic acid is preferably malonic acid, malic acid, maleic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, fumaric acid, tartaric acid, 4-methylphthalic acid or citric acid, and more preferably malonic acid, malic acid, tartaric acid, succinic acid, glutaric acid, pimelic acid, adipic acid or citric acid.

[0206] The organic acid preferably has a low pKa (eg, 1.0 to 5.0). Thus, contact with an organic acid with a lower pKa can reduce the surface charge of particles such as pigments and resin particles in the ink dispersed and stabilized by weakly acidic functional groups such as carboxyl groups, thereby reducing dispersion stability.

[0207] The organic acid preferably has a low pKa, high solubility in water, and a valence of 2 or more. Furthermore, the organic acid more preferably has a high buffering capacity in a pH region lower than the pKa of the functional group (eg, carboxyl group) that stabilizes particle dispersion in the ink.

[0208] -Metal Complex-

[0209] The metal complex preferably contains at least one selected from the group consisting of zirconium, aluminum, and titanium as a metal element.

[0210] The metal complex is preferably a metal complex containing at least one selected from the group consisting of acetate, acetylacetone, methyl acetoacetate, ethyl acetoacetate, octanediol, butoxyacetylacetone, lactate, lactate ammonium salt and triethanolamine as a ligand.

[0211] The metal complex may be a commercially available product. Various organic ligands (especially various multidentate ligands capable of forming metal chelate catalysts) are available on the market. Therefore, the metal complex may be a metal complex prepared by combining commercially available organic ligands and metals.

[0212] Examples of the metal complex include zirconium tetraacetylacetonate (e.g., “ORGATIX ZC-150” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoacetylacetonate (e.g., “ORGATIX ZC-540” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium diacetylacetonate (e.g., “ORGATIX ZC-550” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoethyl acetylacetonate (e.g., “ORGATIX ZC-560” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium acetate (e.g., “ORGATIX ZC-115” manufactured by Matsumoto Fine Chemical Co., Ltd.), diisopropoxybis(acetylacetonate)titanium (e.g., “ORGATIX TC-100” manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium tetraacetylacetonate (e.g., “ORGATIX ZC-550” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium monoethyl acetylacetonate (e.g., “ORGATIX ZC-560” manufactured by Matsumoto Fine Chemical Co., Ltd.), zirconium acetate (e.g., “ORGATIX ZC-115” manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium tetraacetylacetonate (e.g., “ORGATIX TC-100” manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium tetraacetylacetonate (e.g., “ORGATIX TC-401”), dioctyloxy bis(octanediol) titanium (e.g., “ORGATIX TC-200” manufactured by Matsumoto Fine Chemical Co., Ltd.), diisopropoxy bis(ethyl acetoacetate) titanium (e.g., “ORGATIX TC-750” manufactured by Matsumoto Fine Chemical Co., Ltd.), tetraacetylacetonate zirconium (e.g., “ORGATIX ZC-700” manufactured by Matsumoto Fine Chemical Co., Ltd.), tributoxy monoacetylacetonate zirconium (e.g., “ORGATIX ZC-540” manufactured by Matsumoto Fine Chemical Co., Ltd.), monobutoxy acetylacetonate bis(ethyl acetoacetate) zirconium (e.g., “ORGATIX ZC-570” manufactured by Matsumoto Fine Chemical Co., Ltd.), dibutoxy bis(ethyl acetoacetate) zirconium (e.g., “ORGATIX ZC-750” manufactured by Matsumoto Fine Chemical Co., Ltd.), tetraacetylacetonate zirconium (e.g., “ORGATIX ZC-700” manufactured by Matsumoto Fine Chemical Co., Ltd.), ZC-580”), aluminum triacetylacetonate (e.g., “ORGATIX AL-80” manufactured by Matsumoto Fine Chemical Co., Ltd.), ammonium lactate titanium salt (e.g., “ORGATIX TC-300” manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate (e.g., Matsumoto Fine Chemical Co., Ltd., Ltd. "ORGATIX TC-310, 315"), tristriethanolamine titanium (Matsumoto Fine Chemical Co., Ltd. "ORGATIX TC-400"), and zirconium chloride compounds (for example, Matsumoto Fine Chemical Co., Ltd. "ORGATIX ZC-126").

[0213] Among them, the metal complex is preferably titanium ammonium lactate (e.g., "ORGATIX TC-300" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium lactate (e.g., "ORGATIX TC-310, 315" manufactured by Matsumoto Fine Chemical Co., Ltd.), titanium triethanolamine (e.g., "ORGATIX TC-400" manufactured by Matsumoto Fine Chemical Co., Ltd.) or a zirconium chloride compound (e.g., "ORGATIX ZC-126" manufactured by Matsumoto Fine Chemical Co., Ltd.).

[0214] -Cationic polymer-

[0215] Furthermore, the pretreatment liquid may be in a form containing one or more cationic polymers as agglomerating components. The cationic polymer is preferably a homopolymer of a cationic monomer having a primary to tertiary amino group or a quaternary ammonium base, a copolymer or polycondensate of a cationic monomer and a non-cationic monomer. The cationic polymer may be used in the form of a water-soluble polymer or water-dispersible latex particles.

[0216] Examples of the cationic polymer include polyvinyl pyridinium salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimidazoles, polyethyleneimine, polybiguanide, polyguanidine, polyallylamine, and derivatives thereof.

[0217] From the viewpoint of the viscosity of the pretreatment liquid, the weight average molecular weight of the cationic polymer is preferably small. In the case of imparting the pretreatment liquid to the recording medium by inkjet recording, it is preferably 1,000 to 500,000, more preferably 1,500 to 200,000, and further preferably 2,000 to 100,000. If the weight average molecular weight is 1,000 or more, it is advantageous from the viewpoint of agglomeration speed. If the weight average molecular weight is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, in the case of imparting the pretreatment liquid to the recording medium by a method other than inkjet recording, it is not limited thereto.

[0218] The coagulant contained in the pretreatment liquid of the present invention may be only one kind or two or more kinds.

[0219] The content of the coagulant is preferably 0.1 to 40% by mass, more preferably 0.1 to 30% by mass, further preferably 1 to 20% by mass, and particularly preferably 1 to 10% by mass, based on the total amount of the pretreatment liquid.

[0220] (Other ingredients)

[0221] The pretreatment liquid may contain other components besides the coagulant as required. Other components that may be contained in the pretreatment liquid include organic solvents, resin particles, surfactants, solid wetting agents, colloidal silica, inorganic salts, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, mildew inhibitors, pH adjusters, viscosity adjusters, rust inhibitors, chelating agents, water-soluble polymer compounds (for example, water-soluble polymer compounds described in paragraphs 0026 to 0080 of Japanese Patent Application No. 2013-001854), and other well-known additives.

[0222] (physical properties)

[0223] From the viewpoint of the aggregation speed of the ink, the pH of the pretreatment liquid is preferably 0.1 to 4.5, and more preferably 0.2 to 4.0. The pH is measured at 25° C. using a pH meter, for example, a pH meter manufactured by DKK-TOA CORPORATION (model “HM-31”).

[0224] From the viewpoint of the aggregation speed of the ink, the viscosity of the pretreatment liquid is preferably 0.5 mPa·s to 10 mPa·s, and more preferably 1 mPa·s to 5 mPa·s. The viscosity is a value measured at 25° C. using a viscometer. The viscosity is measured at 25° C. using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0225] The surface tension of the pretreatment liquid is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 30 mN / m to 45 mN / m. The surface tension is a value measured at a temperature of 25° C. The surface tension is measured at 25° C. using a surface tensiometer, for example, using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”) by a plate method.

[0226] [Image recording method]

[0227] In the image recording method of the present invention, it is preferred to use the above-mentioned ink set to impart a colored ink and a white ink to an impermeable substrate by inkjet recording. The white ink may be imparted after imparting the colored ink to the impermeable substrate, or the colored ink may be imparted after imparting the white ink. When the impermeable substrate is transparent and used for back printing, it is preferred to impart the white ink after imparting the colored ink to the impermeable substrate. That is, the image recording method of the present invention more preferably includes the following steps: imparting the colored ink to the impermeable substrate by inkjet recording; and imparting the white ink to the colored ink film formed by imparting the colored ink by inkjet recording.

[0228] (Coloring ink applying step)

[0229] The image recording method of the present invention preferably includes a step of applying a color ink to an impermeable substrate by an inkjet recording method (hereinafter referred to as a "color ink applying step").

[0230] -Impermeable substrate-

[0231] In the present invention, the impermeability of the impermeable substrate refers to the property that the water absorption rate within 24 hours measured in accordance with ASTM D570-98 (2018) is 2.5% or less. Here, the "%" as the unit of water absorption rate is based on mass. The above water absorption rate is preferably 1.0% or less, and more preferably 0.5% or less.

[0232] Examples of materials for the non-permeable substrate include glass, metals (e.g., aluminum, zinc, copper, etc.) and resins (e.g., polyvinyl chloride, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, nylon, acrylic resin, etc.).

[0233] The material of the impermeable substrate is preferably resin.

[0234] Among them, from the viewpoint of versatility, the material of the impermeable substrate is preferably polypropylene, polyethylene, polyethylene terephthalate, nylon, acrylic resin or polyvinyl chloride.

[0235] The shape of the impermeable substrate is preferably sheet-like (film-like) or plate-like. Examples of the impermeable substrate having such a shape include glass plates, metal plates, resin sheets (resin films), paper laminated with plastic, paper laminated or vapor-deposited with metal, and plastic sheets (plastic films) laminated or vapor-deposited with metal.

[0236] Examples of the resin-made impermeable substrate include resin sheets (resin films), and specific examples include flexible packaging materials for packaging food and the like, and floor guides for large retail stores.

[0237] Examples of the impermeable substrate include sheet-shaped (film-shaped) or plate-shaped impermeable substrates and woven fabrics (textiles) and nonwoven fabrics formed of impermeable fibers.

[0238] The thickness of the impermeable substrate is preferably 0.1 μm to 1,000 μm, more preferably 0.1 μm to 800 μm, and further preferably 1 μm to 500 μm.

[0239] The non-permeable substrate can be subjected to a hydrophilic treatment. As the hydrophilic treatment, corona treatment, plasma treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., UV treatment) and flame treatment can be cited, but are not limited to these. The corona treatment can be carried out using, for example, a corona master (product name "PS-10S", Shinko Flectric & Instrumentation Co., Ltd. system). The conditions of the corona treatment can be appropriately selected according to the type of the non-permeable substrate, etc.

[0240] -Inkjet recording method-

[0241] The ink jetting method in the inkjet recording method is not particularly limited and may be any of the known methods, for example, a charge control method that utilizes electrostatic attraction to jet ink, a drop-on-demand inkjet method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into a sound beam and irradiates the beam onto the ink and utilizes radiation pressure to jet the ink, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0242] As the inkjet recording method, the method described in Japanese Patent Publication No. 54-59936 can be particularly effectively used. In this inkjet recording method, the ink undergoes a rapid volume change under the action of thermal energy, and the ink is ejected from the nozzle using the force generated by the state change. As the inkjet recording method, the method described in paragraphs 0093 to 0105 of Japanese Patent Publication No. 2003-306623 can also be used.

[0243] Imparting ink onto a non-permeable substrate in an inkjet recording method is performed by ejecting the ink from nozzles of an inkjet head.

[0244] As inkjet head methods, there are a reciprocating method in which a short stripe serial inkjet head records while scanning in the width direction of the recording medium, and a line method in which a line inkjet head is used in which recording elements are arranged corresponding to the entire area of ​​one side of the recording medium.

[0245] In the line method, by scanning on the recording medium in a direction intersecting the arrangement direction of the recording elements, it is possible to record an image on the entire surface of the recording medium. In the line method, there is no need for a transport system such as a carriage for scanning a short strip of inkjet head in the reciprocating method. Moreover, compared to the reciprocating method, in the line method, there is no need for complex scanning control between the movement of the carriage and the recording medium, and only the recording medium is moved. Therefore, according to the line method, the speed of image recording can be increased compared to the reciprocating method.

[0246] The ink is preferably applied using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi or more, and even more preferably 800 dpi or more). Dpi is an abbreviation for dots per inch, and linch (1 inch) is 2.54 cm.

[0247] From the perspective of obtaining high-definition images, the amount of ink droplets ejected from the nozzles of the inkjet head is preferably 1 pL (picolitre) to 10 pL, more preferably 1.5 pL to 6 pL. In addition, from the perspective of improving image unevenness and connection of continuous steps, it is also effective to eject different droplet amounts in combination.

[0248] (White ink application process)

[0249] The image recording method of the present invention preferably includes a step of applying a white ink on a colored ink film formed by applying the colored ink by an inkjet recording method (hereinafter referred to as a "white ink applying step").

[0250] The details of the inkjet recording method are the same as those in the coloring ink applying step.

[0251] The image recording method of the present invention preferably includes a step of pre-applying a pre-treatment liquid to an impermeable substrate. That is, the image recording method of the present invention preferably includes: a step of applying a pre-treatment liquid to an impermeable substrate (hereinafter referred to as a "pre-treatment liquid applying step"); a step of applying a colored ink to the impermeable substrate to which the pre-treatment liquid is applied by an inkjet recording method; and a step of applying a white ink to a colored ink film formed by applying the colored ink by an inkjet recording method.

[0252] (Pretreatment liquid application step)

[0253] The application of the pretreatment liquid in the pretreatment liquid application step can be performed by applying a known application method such as a coating method, an inkjet recording method, or a dipping method.

[0254] Examples of the coating method include known coating methods using a bar coater, an extrusion die coater, an air knife coater, a blade coater, a rod coater, a knife coater, an extrusion coater, a reverse roll coater, and the like.

[0255] The details of the inkjet recording method are the same as those in the coloring ink applying step.

[0256] The amount of the pretreatment liquid applied is preferably 0.5 g / m 2 ~2.5g / m 2 , more preferably 1.0 g / m 2 ~2.0g / m 2 .

[0257] The impermeable substrate may be heated before applying the pretreatment solution. The heating temperature may be appropriately set according to the type of the impermeable substrate and the composition of the pretreatment solution, but the temperature of the impermeable substrate is preferably set to 30°C to 70°C, more preferably 30°C to 60°C.

[0258] In the pretreatment liquid application step, the pretreatment liquid applied to the non-permeable substrate may be heated and dried. Examples of the mechanism for heating and drying the pretreatment liquid include a known heating mechanism such as a heater, a known air supply mechanism such as a dryer, and a combination thereof.

[0259] Examples of methods for heating and drying the pretreatment liquid include a method of heating the non-permeable substrate from the side opposite to the side to which the pretreatment liquid is applied using a heater, a method of blowing warm air or hot air toward the side to which the pretreatment liquid is applied, a method of heating the non-permeable substrate from the side to which the pretreatment liquid is applied or from the side opposite to the side to which the pretreatment liquid is applied using an infrared heater, and a method of combining a plurality of these methods.

[0260] The heating temperature during heat drying of the pretreatment liquid is preferably 35° C. or higher, more preferably 40° C. or higher. The upper limit of the heating temperature is not particularly limited, but is preferably 100° C., more preferably 90° C., and further preferably 70° C.

[0261] The heating drying time is not particularly limited, but is preferably 0.5 to 60 seconds, more preferably 0.5 to 20 seconds, and even more preferably 0.5 to 10 seconds.

[0262] (Other processes)

[0263] The image recording method of the present invention may include a drying step of heating and drying the applied ink after the step of applying the ink.

[0264] As a mechanism for heating and drying the ink, there can be mentioned a known heating mechanism such as a heater, a known air supply mechanism such as a dryer, and a combination of these.

[0265] Examples of methods for heating and drying the ink include a method of heating the non-permeable substrate from the side opposite to the surface to which the ink is applied using a heater, a method of blowing warm air or hot air toward the surface to which the ink is applied using an infrared heater, a method of heating the non-permeable substrate from the surface to which the ink is applied or from the side opposite to the surface to which the ink is applied using an infrared heater, and a method of combining a plurality of these methods.

[0266] The heating temperature during heat drying is preferably 55° C. or higher, more preferably 60° C. or higher, and further preferably 65° C. or higher. The upper limit of the heating temperature is not particularly limited, and is, for example, 100° C., and preferably 90° C.

[0267] The heating and drying time of the ink is not particularly limited, but is preferably 3 seconds to 60 seconds, more preferably 5 seconds to 60 seconds, and even more preferably 10 seconds to 45 seconds.

[0268] Example

[0269] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it departs from the gist of the present invention.

[0270] In the examples, the glass transition temperature is measured under normal measurement conditions using a differential scanning calorimeter (for example, a differential scanning calorimeter (product name “EXSTAR6220”, manufactured by SII NanoTechnology Inc.)).

[0271] In the examples, the number average molecular weight is measured using gel permeation chromatography (GPC). When measuring by gel permeation chromatography (GPC), HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) was used as a measuring device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mmID×15 cm, manufactured by Tosoh Corporation) were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, the measurement was performed using an RI detector, wherein the sample concentration was set to 0.45% by mass, the flow rate was set to 0.35 ml / min, the sample injection volume was set to 10 μl, and the measurement temperature was set to 40°C. The calibration curve was prepared based on eight samples of "standard sample TSKstandard, polystyrene (polystyrene)" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0272] <Example 1 to Example 14, Comparative Example 1 to Comparative Example 3>

[0273] First, a magenta pigment dispersion and a white pigment dispersion are prepared, and various additives are added to the prepared magenta pigment dispersion and white pigment dispersion to prepare a magenta ink and a white ink.

[0274] Pigment dispersants P1 to P5 and pigment dispersants Q1 to Q9 used for preparing magenta pigment dispersions and white pigment dispersions were prepared by the following method. Pigment dispersants Q1 to Q9 were prepared with reference to the method described in Japanese Patent Application Laid-Open Nos. 2014-40553 and 2015-63688.

[0275] (Pigment dispersant P1)

[0276] 89.7 parts by mass of butyl diglycol were placed in a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and the gas was replaced with nitrogen. The reaction vessel was heated to 110° C., and a mixed solution of 40 parts by mass of lauryl methacrylate, 47 parts by mass of styrene, 47 parts by mass of acrylic acid, and 7.0 parts by mass of 2,2'-azobis(2-methylpropionic acid) dimethyl ester (product name "V-601", manufactured by FUJIFILM Wako Pure Chemical Corporation, hereinafter referred to as "V-601") as a polymerization initiator was added dropwise over 2 hours to carry out polymerization reaction. After completion of the dropwise addition, the reaction was further carried out at 110° C. for 3 hours, and then 0.6 parts by mass of V-601 was added, and the reaction was further carried out at 110° C. for 1 hour to obtain a polymer having a number average molecular weight (Mn) of 28,000. Furthermore, after cooling to room temperature, 51.2 parts by mass of dimethylaminoethanol was added for neutralization. The amount of dimethylaminoethanol was an amount sufficient to neutralize 100% of the acrylic acid. Furthermore, 168.7 parts by mass of water was added to obtain an aqueous solution of the pigment dispersant P1 having a solid content concentration of 24% by mass.

[0277] Pigment dispersant P1 is a random polymer, and the mass ratio of each structural unit constituting the polymer is lauryl methacrylate: styrene: acrylic acid = 30: 35: 35. In addition, the structural unit derived from acrylic acid is 100% neutralized with dimethylaminoethanol, and the structural unit derived from acrylic acid in the pigment dispersants P2 to P5 described later is also neutralized in the same manner. In addition, the number average molecular weight of pigment dispersant P1 is 28,000, and the glass transition temperature is 29.7°C.

[0278] (Pigment dispersant P2)

[0279] Pigment dispersant P2 was obtained by the same method as that of pigment dispersant P1 except that a mixed solution of 10 parts by mass of lauryl methacrylate, 47 parts by mass of styrene, 45 parts by mass of methacrylic acid, and 7.0 parts by mass of V-601 was added dropwise to the reaction container.

[0280] The pigment dispersant P2 is a random polymer, and the mass ratio of each structural unit constituting the polymer is lauryl methacrylate: styrene: methacrylic acid = 10: 46: 44. The number average molecular weight of the pigment dispersant P2 is 26,500, and the glass transition temperature is 113.2°C.

[0281] (Pigment dispersant P3)

[0282] Pigment dispersant P3 was obtained by the same method as that of pigment dispersant P1 except that a mixed solution of 40 parts by mass of isobornyl methacrylate, 38 parts by mass of styrene, 22 parts by mass of methacrylic acid and 7.0 parts by mass of V-601 was added dropwise to the reaction container.

[0283] Pigment dispersant P3 is a random polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: styrene: methacrylic acid = 40: 38: 22. Also, pigment dispersant P3 has a number average molecular weight of 27,000 and a glass transition temperature of 151°C.

[0284] (Pigment dispersant P4)

[0285] Pigment dispersant P4 was obtained by the same method as that of pigment dispersant P1 except that a mixed solution of 40 parts by mass of lauryl methacrylate, 97 parts by mass of methyl methacrylate, 30 parts by mass of methacrylic acid and 7.0 parts by mass of V-601 was added dropwise to the reaction container.

[0286] Pigment dispersant P4 is a random polymer, and the mass ratio of each structural unit constituting the polymer is lauryl methacrylate:methyl methacrylate:methacrylic acid=24:58:18. Also, pigment dispersant P4 has a number average molecular weight of 25,000 and a glass transition temperature of 55.1°C.

[0287] (Pigment dispersant P5)

[0288] Pigment dispersant P5 was obtained by the same method as that of pigment dispersant P1 except that a mixed solution of 17 parts by mass of lauryl methacrylate, 20 parts by mass of styrene, 20 parts by mass of acrylic acid, and 7.0 parts by mass of V-601 was added dropwise to the reaction container.

[0289] Pigment dispersant P5 is a random polymer, and the mass ratio of each structural unit constituting the polymer is lauryl methacrylate: styrene: acrylic acid = 30: 35: 35. Also, pigment dispersant P5 has a number average molecular weight of 12,000 and a glass transition temperature of 29.7°C.

[0290] (Pigment dispersant Q1)

[0291] In a 500 ml separable flask equipped with a reflux tube, a gas introduction device, a thermometer and a stirring device, 186.6 parts by mass of triethylene glycol monobutyl ether (hereinafter referred to as "TEGmBE"), 1.0 parts by mass of iodine, 3.7 parts by mass of 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (product name "V-70", manufactured by FUJIFILM Wako Pure Chemical Corporation, hereinafter referred to as "V-70"), 44.0 parts by mass of isobornyl methacrylate, 20 parts by mass of cyclohexyl methacrylate and 0.2 parts by mass of iodosuccinimide were placed, and polymerization was carried out at 45° C. for 5 hours while nitrogen gas was passed through to obtain a solution of the A polymer block. The polymerization rate (yield) of the A polymer block calculated from the solid content of the obtained solution of the A polymer block was 99.0%. In addition, the number average molecular weight (Mn) measured by GPC was 5,500. Next, the polymerization temperature was lowered to 40°C, and 23.5 parts by mass of isobornyl methacrylate, 17.6 parts by mass of cyclohexyl methacrylate, 17.6 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of the A polymer block obtained above. Then, the polymerization was carried out for 4 hours, and then heated to 70°C for polymerization for 1 hour, thereby forming a B polymer block and obtaining a solution of an AB block polymer. The solid content of the obtained solution of the AB block polymer was 41.2%, and the polymerization rate of the B polymer block calculated based on its solid content was almost 100%. In addition, the number average molecular weight (Mn) of the AB block polymer was 11,000. After cooling the obtained solution of the AB block polymer, 66.1 parts by mass of TEGmBE were added to adjust the solid content concentration to 33.3% by mass. The AB block polymer was used as a pigment dispersant Q1.

[0292] Pigment dispersant Q1 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: cyclohexyl methacrylate: methacrylic acid = 55:31:14. In addition, the glass transition temperature of pigment dispersant Q1 is 92°C and 154°C.

[0293] (Pigment dispersant Q2)

[0294] When preparing the solution of the A polymer block, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 44 parts by mass of isobornyl methacrylate, 14.08 parts by mass of cyclohexyl methacrylate, and 0.2 parts by mass of iodosuccinimide were added. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 5,000. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) of the AB block polymer was 9,500.

[0295] Pigment dispersant Q2 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: cyclohexyl methacrylate: methacrylic acid = 58: 27: 15. In addition, the glass transition temperature of pigment dispersant Q2 is 137.9°C and 154°C.

[0296] (Pigment dispersant Q3)

[0297] When preparing the solution of the A polymer block, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 44 parts by mass of isobornyl methacrylate, 84 parts by mass of cyclohexyl methacrylate, and 0.2 parts by mass of iodosuccinimide were loaded. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 4,500. 23.5 parts by mass of isobornyl methacrylate, 35.25 parts by mass of cyclohexyl methacrylate, 58.75 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of the A polymer block. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) of the AB block polymer is 10,000.

[0298] Pigment dispersant Q3 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: cyclohexyl methacrylate: methacrylic acid = 27: 49: 24. In addition, the glass transition temperature of pigment dispersant Q3 is 108.5°C and 163.3°C.

[0299] (Pigment dispersant Q4)

[0300] When preparing the solution of the A polymer block, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 44 parts by mass of isobornyl methacrylate, 31 parts by mass of cyclohexyl methacrylate, 145 parts by mass of methacrylic acid, and 0.2 parts by mass of iodosuccinimide were loaded. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 6,500. 24 parts by mass of isobornyl methacrylate, 35 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of the A polymer block. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) of the AB block polymer is 12,000.

[0301] Pigment dispersant Q4 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: cyclohexyl methacrylate: methacrylic acid = 24: 11: 65. In addition, the glass transition temperature of pigment dispersant Q4 is 0°C and 203.1°C.

[0302] (Pigment dispersant Q5)

[0303] When preparing the solution of the A polymer block, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 16 parts by mass of isobornyl methacrylate, 69.3 parts by mass of methyl methacrylate, 21.3 parts by mass of acrylic acid, and 0.2 parts by mass of iodosuccinimide were loaded. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 4,300. 23.5 parts by mass of methyl methacrylate, 35.25 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of the A polymer block. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) of the AB block polymer is 9,800.

[0304] Pigment dispersant Q5 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: methyl methacrylate: methacrylic acid: acrylic acid = 10: 56: 21: 13. In addition, the glass transition temperature of pigment dispersant Q5 is 113.7°C and 170.3°C.

[0305] (Pigment dispersant Q6)

[0306] When preparing the solution of polymer block A, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 38 parts by mass of lauryl methacrylate, 70.6 parts by mass of acrylic acid, and 0.2 parts by mass of iodosuccinimide were loaded. In addition, the solution of polymer block A was obtained by the same method as pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 5,600. 15 parts by mass of lauryl methacrylate, 23.18 parts by mass of methyl methacrylate, 30 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of polymer block A. In addition, the solution of AB block polymer was obtained by the same method as pigment dispersant Q1. The number average molecular weight (Mn) of AB block polymer is 11,500.

[0307] Pigment dispersant Q6 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is lauryl methacrylate: methyl methacrylate: methacrylic acid: acrylic acid = 30: 13: 17: 40. In addition, the glass transition temperature of pigment dispersant Q6 is 21.3°C and 79.7°C.

[0308] (Pigment dispersant Q7)

[0309] When preparing the solution of the A polymer block, 186.6 parts by mass of TEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 88 parts by mass of isobornyl methacrylate, 40.5 parts by mass of cyclohexyl methacrylate, and 0.2 parts by mass of iodosuccinimide were loaded. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) measured by GPC was 10,000. 47 parts by mass of isobornyl methacrylate, 35.2 parts by mass of cyclohexyl methacrylate, 35.2 parts by mass of methacrylic acid, and 1.2 parts by mass of V-70 were added to the solution of the A polymer block. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q1. The number average molecular weight (Mn) of the AB block polymer is 22,000.

[0310] Pigment dispersant Q7 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: cyclohexyl methacrylate: methacrylic acid 55: 31: 14. In addition, the glass transition temperature of pigment dispersant Q7 is 92°C and 154°C.

[0311] (Pigment dispersant Q8)

[0312] In a 500 ml separable flask equipped with a reflux tube, a gas introduction device, a thermometer and a stirring device, 198.2 parts by mass of diethylene glycol monobutyl ether (hereinafter referred to as "DEGmBE"), 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 120 parts by mass of methyl methacrylate, 67.2 parts by mass of cyclohexyl methacrylate, 28.8 parts by mass of acrylic acid, and 0.17 parts by mass of diphenylmethane as a catalyst were loaded. While nitrogen gas was flowing, polymerization was carried out at 45°C for 5 hours to obtain a solution of the A polymer block. The polymerization rate (yield) of the A polymer block calculated based on the solid content of the solution was 96.2%. In addition, the number average molecular weight (Mn) measured using GPC was 5,200. Next, the polymerization temperature was reduced to 40°C, and 35.2 parts by mass of benzyl methacrylate and 1.2 parts by mass of V-70 were added to the obtained solution of the A polymer block. Then, the polymerization was carried out for 4 hours and then heated to 70° C. for 1 hour to form a B polymer block, thereby obtaining an AB block copolymer solution.

[0313] The solid content of the obtained AB block copolymer solution was 40.8%, and the polymerization rate of the B polymer block calculated based on the solid content was almost 100%. After cooling the AB block copolymer solution, 66.1 parts by mass of DEGmBE was added to adjust the solid content to 33.3% by mass. The AB block copolymer was used as the pigment dispersant Q8. The number average molecular weight (Mn) of the pigment dispersant Q8 was 5,800.

[0314] Pigment dispersant Q8 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is cyclohexyl methacrylate: benzyl methacrylate: methyl methacrylate: acrylic acid = 27: 14: 48: 11. In addition, the glass transition temperature of pigment dispersant Q8 is 54°C and 94°C.

[0315] (Pigment dispersant Q9)

[0316] When preparing the solution of the A polymer block, 198.2 parts by mass of DEGmBE, 1.0 parts by mass of iodine, 3.7 parts by mass of V-70, 116.9 parts by mass of methyl methacrylate, 60.6 parts by mass of isobornyl methacrylate, 28.8 parts by mass of acrylic acid, and 0.17 parts by mass of diphenylmethane as a catalyst were loaded. In addition, the solution of the A polymer block was obtained by the same method as the pigment dispersant Q8. The number average molecular weight (Mn) measured by GPC is 5,400. 35.2 parts by mass of benzyl methacrylate and 1.2 parts by mass of V-70 were added to the solution of the A polymer block. In addition, the solution of the AB block polymer was obtained by the same method as the pigment dispersant Q8. The number average molecular weight (Mn) of the AB block polymer is 6,200.

[0317] Pigment dispersant Q9 is an AB block polymer, and the mass ratio of each structural unit constituting the polymer is isobornyl methacrylate: benzyl methacrylate: methyl methacrylate: acrylic acid = 25: 15: 48: 12. In addition, the glass transition temperature of pigment dispersant Q9 is 54°C and 141.7°C.

[0318] (Magenta ink M1) - Preparation of magenta pigment dispersion MA1 -

[0319] 150 parts by mass of pigment dispersant P1 were dissolved in water to a concentration of about 25% by mass to prepare a polymer aqueous solution. 180 parts by mass of polymer aqueous solution, 90 parts by mass of PR-122 (FUJI Fast Red (registered trademark), manufactured by Fuji Pigment Co., Ltd.) as a magenta pigment and 171.9 parts by mass of water were mixed to obtain a mixed solution. A potassium hydroxide aqueous solution was added to the obtained mixed solution and the pH after neutralization was adjusted to 8.7. Next, a bead mill (bead diameter: 0.1 mmφ, zirconia beads) was used to disperse the neutralized mixed solution for 3 hours. Thus, a magenta pigment dispersion in which the magenta pigment was dispersed by the pigment dispersant P1 was obtained. The pigment concentration was 15% by mass.

[0320] -Preparation of Magenta Ink M1-

[0321] The following ingredients were mixed to prepare magenta ink M1.

[0322] · The above-mentioned magenta pigment dispersion MA1 (pigment concentration: 15 mass %) ... 46.7 mass %

[0323] ·Dispersion of resin particles A (solid content: 23.2% by mass) ... 12.9% by mass

[0324] ·Organic solvent: Propylene glycol…26.0 mass%

[0325] Surfactant: OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 0.25 mass%

[0326] · Water: The remainder to make the total ink 100% by mass

[0327] The resin particles A are produced by the following method.

[0328] A 2-liter three-necked flask (reaction vessel) equipped with a stirrer, a thermometer, a reflux cooling tube, and a nitrogen inlet tube was charged with 560.0 g of methyl ethyl ketone, and the temperature was raised to 87°C. Next, while maintaining the reflux state in the reaction vessel, a mixed solution consisting of 220.4 g of methyl methacrylate, 301.6 g of isobornyl methacrylate, 58.0 g of methacrylic acid, 108 g of methyl ethyl ketone, and 2.32 g of 2,2'-azobis(2-methylpropionic acid) dimethyl ester (product name "V-601", manufactured by FUJIFILM Wako Pure Chemical Corporation) as a polymerization initiator was added dropwise at a constant rate to the methyl ethyl ketone in the reaction vessel in a manner that the addition was completed within 2 hours. In addition, the reflux state was maintained until the reaction was completed. After the addition was completed, the reaction solution was stirred for 1 hour, and then the following step (1) was performed on the reaction solution.

[0329] Step (1) ... A solution consisting of 1.16 g of "V-601" and 6.4 g of methyl ethyl ketone was added, and the mixture was stirred for 2 hours.

[0330] Next, the operation of the above step (1) was repeated 4 times, and then a solution consisting of 1.16 g of "V-601" and 6.4 g of methyl ethyl ketone was further added, and stirring was continued for 3 hours.

[0331] After the reaction was completed, the temperature of the solution was lowered to 65° C., 163.0 g of isopropyl alcohol was added, and the mixture was naturally cooled to obtain a polymerization solution (solid content concentration: 41.0% by mass) containing a copolymer.

[0332] Next, 317.3 g of the obtained polymerization solution was weighed, and 46.4 g of isopropyl alcohol, 1.65 g of a 20% by mass aqueous maleic anhydride solution (equivalent to 0.3% by mass in terms of maleic acid relative to the copolymer) and 40.77 g of a 2 mol / L aqueous sodium hydroxide solution were added thereto, and the temperature of the liquid in the reaction container was raised to 70°C.

[0333] Next, 380 g of distilled water was added dropwise to the liquid heated to 70° C. at a rate of 10 mL / min. Then, the temperature of the liquid in the reaction container was maintained at 70° C. for 1.5 hours under reduced pressure, thereby distilling off a total of 287.0 g of isopropyl alcohol, methyl ethyl ketone, and distilled water. 0.278 g of PROXEL GXL (S) (manufactured by Arch Chemicals Japan, Inc.) was added to the obtained liquid (440 ppm in terms of benzisothiazoline-3-one relative to the polymer solid content).

[0334] The obtained liquid was filtered with a 1 μm filter and the filtrate was recovered to obtain an aqueous dispersion (solid content concentration 23.2% by mass) of resin particles A which was a copolymer of methyl methacrylate / isobornyl methacrylate / methacrylic acid / sodium methacrylate (=70 / 20 / 5 / 5 [mass ratio]). The volume average particle size of the resin particles A was 5.0 nm and the weight average molecular weight (Mw) was 60,000.

[0335] (Magenta ink M2~M7)

[0336] The pigment dispersant was changed to the pigment dispersant described in Table 1, and after preparing the pigment dispersion liquid by the same method as the magenta pigment dispersion liquid MA1, magenta inks M2 to M7 were prepared by the same method as the magenta ink M1 using the resin particles, surfactants, and organic solvents described in Table 1. In the magenta inks M6 and M7, BYK-347 (manufactured by BYK) was used as a surfactant.

[0337] The resin particles B contained in the magenta inks M6 and M7 were prepared by the following method.

[0338] A three-necked flask equipped with a stirrer, a thermometer, a reflux cooling tube and a nitrogen inlet tube was charged with water (250 g), 12-methacrylamide dodecanoic acid (7.0 g), potassium bicarbonate (0.17 g) and isopropyl alcohol (20 g), and the temperature was raised to 85° C. under a nitrogen stream. A mixed solution consisting of 4,4'-azobis(4-cyanovaleric acid) (free radical polymerization initiator, product name "V-501", manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.11 g), potassium bicarbonate (0.08 g) and water (9 g) was added thereto, and stirred for 10 minutes. Next, a monomer solution consisting of styrene (30 g) and methyl methacrylate (63 g) was dripped into the three-necked flask at a constant speed in a manner that the addition was completed within 3 hours. Furthermore, a mixed solution consisting of V-501 (0.06 g), potassium bicarbonate (0.04 g) and water (6 g) was added twice (immediately after the start of the dropwise addition of the monomer solution and 1.5 hours after the start of the dropwise addition of the monomer solution). After the dropwise addition of the monomer solution, stirring was performed for 1 hour. Next, a mixed solution consisting of V-501 (0.06 g), potassium bicarbonate (0.04 g) and water (6 g) was added to the obtained reaction mixture, and stirring was further performed for 3 hours. The obtained reaction mixture was filtered with a mesh having an opening of 50 μm to obtain an aqueous dispersion of resin particles B which was a copolymer of styrene / methyl methacrylate / 12-methacrylamide dodecanoic acid (=30 / 63 / 7 [mass ratio]). The obtained aqueous dispersion of resin particles B had a pH of 8.5, a solid content concentration of 25% by mass, a volume average particle size of 30 nm, a weight average molecular weight (Mw) of 250,000, and a Tg of 96°C.

[0339] In Table 1, the content (mass %) relative to the total amount of magenta ink is recorded for pigments, pigment dispersants, resin particles, organic solvents and surfactants. In addition, in Table 1, the type, form, type of monomers constituting the polymer and their content (mass %) and glass transition temperature Tgc are recorded for the pigment dispersants contained in each magenta ink. "Block" in the form column represents a block polymer, and "random" represents a random polymer. The glass transition temperature Tgc only records the example in which the pigment dispersant contained in the magenta ink is a random polymer. In addition, in Table 1, EGmHE represents ethylene glycol monohexyl ether. The water content is the remainder that makes the ink as a whole 100% by mass, which is recorded as "remainder" in Table 1.

[0340] [Table 1]

[0341]

[0342] (White ink W1)

[0343] -Preparation of white pigment dispersion WA1-

[0344] 136.4 parts by mass of pigment dispersant Q1, 163.6 parts by mass of butyl carbitol, and 6450 parts by mass of CI pigment white as white pigment (trade name "JR-405", titanium oxide, manufactured by TAYCA Co., Ltd.) were blended and stirred with a disperser. Then, a horizontal medium disperser was used to fully disperse the white pigment to obtain an oily pigment dispersion. The average particle size of the white pigment dispersed in the oily pigment dispersion was 290 nm. The viscosity of the oily pigment dispersion was 86.3 mPa·s. Then, while stirring 700 parts by mass of the above-mentioned oily pigment dispersion using a disperser, a mixed solution consisting of 4.0 parts by mass of potassium hydroxide and 341 parts by mass of water was slowly added to neutralize and phase transfer. Then, a horizontal medium disperser was used to fully disperse the white pigment to obtain an aqueous pigment dispersion. Coarse particles were removed from the obtained aqueous pigment dispersion using a 10 μm filter and a 5 μm filter. At this time, no clogging of the filter was observed. The average particle size of the white pigment dispersed in the aqueous pigment dispersion is 266nm. The viscosity of the aqueous pigment dispersion is 14.5mPa·s, and the pH is 9.8. In addition, the average particle size of the above-mentioned white pigment is measured using a light scattering particle size distribution measuring machine (product name "UPA-EX150", Nikkiso Co., Ltd. system).

[0345] -Preparation of white ink W1-

[0346] The following components were mixed to prepare white ink W1.

[0347] · The above-mentioned white pigment dispersion WA1 (pigment concentration: 45 mass%) ... 26.7 mass%

[0348] ·Dispersion of resin particles A (solid content: 23% by mass) ... 17.2% by mass

[0349] ·Organic solvent: Propylene glycol…25.0 mass%

[0350] Surfactant: OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 0.25 mass%

[0351] · Water: The remainder of the ink is 100% by mass

[0352] (White ink W2~W11)

[0353] The pigment dispersant was changed to the pigment dispersant described in Table 2, and after preparing a white pigment dispersion by the same method as the white pigment dispersion WA1, white inks W2 to W11 were prepared by the same method as the white ink W1 using the resin particles, surfactant and organic solvent described in Table 2.

[0354] In Table 2, the content (mass %) of the pigment, pigment dispersant, resin particles, organic solvent and surfactant relative to the total amount of white ink is recorded. In addition, in Table 2, the type, form, type of monomer constituting the polymer and its content (mass %) and glass transition temperatures Tg1 and Tg2 (Tg1<Tg2) of the pigment dispersant contained in each white ink are recorded. "Block" in the form column represents a block polymer, and "random" represents a random polymer. The glass transition temperatures Tg1 and Tg2 only record examples in which the pigment dispersant contained in the white ink is a block polymer. The water content is the remainder that makes the ink as a whole 100% by mass, which is recorded as "remainder" in Table 2.

[0355]

[0356] (Pretreatment liquid)

[0357] Resin particles, a coagulant, an organic solvent, a surfactant, and water were mixed so as to have the following contents (mass %) to prepare a pretreatment solution to be applied to a substrate in advance. The details of the resin particles, a coagulant, an organic solvent, and a surfactant used in the preparation of the pretreatment solution are as follows.

[0358] Resin particles: polyester resin (product name "PESRESIN A124GP", manufactured by TAKAMATSU OIL & FAT CO., LTD.) ... 10% by mass

[0359] · Coagulant: Malonic acid…5% by mass

[0360] ·Organic solvent: Propylene glycol...10% by mass

[0361] Surfactant: Sodium dodecylbenzenesulfonate (hard type) (manufactured by Tokyo Chemical Industry Co., Ltd.) ... 1 mass%

[0362] · Water: the remainder to make the entire pretreatment liquid 100% by mass

[0363] [Image Record]

[0364] Using the above-mentioned colored ink and white ink and the above-mentioned pretreatment liquid, image recording was performed by the following method. As an inkjet head, a GELJET (registered trademark) GX5000 print head (made by Ricoh Co., Ltd.) was prepared. The above-mentioned inkjet head is a line-type inkjet head arranged with 96 nozzles. The above-mentioned inkjet head is configured by fixing the above-mentioned inkjet head to an inkjet recording device. At this time, the arrangement direction of the 96 nozzles is configured to be inclined 75.7° relative to the direction orthogonal to the moving direction of the workbench of the inkjet recording device on the same plane. As a substrate, a polyethylene terephthalate (PET) substrate (product name "FE2001", thickness 12μm, made by FUTAMURA CHEMICAL CO., LTD.) was prepared, and the following pretreatment liquid imparting process and image recording process were carried out in sequence using the PET substrate.

[0365] (Pretreatment liquid application step)

[0366] The substrate was fixed on the workbench of the inkjet recording device, and then the workbench with the substrate fixed was moved in a straight line at a constant speed of 500 mm / sec while applying the pretreatment liquid on the substrate using a wire bar coater. The amount of pretreatment liquid applied was set to 1.5 g / m 2 At the part where the application of the pretreatment liquid was completed, drying of the pretreatment liquid was started using a dryer at 50° C. 1.5 seconds after the application of the pretreatment liquid to the part was completed. Drying was completed 3.5 seconds after the application of the pretreatment liquid was completed. That is, the drying time was 2 seconds.

[0367] (Image Recording Process)

[0368] While the substrate on which the pretreatment liquid has been dried is moved at a constant table speed of 50 mm / sec, magenta ink is sprayed from the inkjet head onto the surface of the substrate to which the pretreatment liquid has been applied (coloring ink application process). After spraying the magenta ink, white ink is sprayed to record a solid image (white ink application process) to obtain an image record. The spraying of the magenta ink begins within 2 seconds from the completion of the drying of the pretreatment liquid. Regarding the ink spraying conditions, the spraying frequency is set to 24 kHz and the resolution is set to 1200 dpi×1200 dpi (dot per inch). The total application amount of the magenta ink and the white ink is set to 17.9 g / m 2 In addition, the magenta ink and the white ink were degassed through a degassing filter and adjusted to 30° C. before being ejected.

[0369] [evaluate]

[0370] The obtained image records were used to evaluate the bending resistance, adhesion and scratch resistance of each Example and Comparative Example. The evaluation method is as follows.

[0371] -Bending resistance-

[0372] The bending resistance was evaluated according to JIS K5600-5-1 by the following method. A cylindrical mandrel bending tester (manufactured by Allgood Co.) was used as the tester. Mandrels with diameters of 8 mm, 10 mm, 12 mm, 13 mm, 16 mm, 19 mm, 20 mm, 25 mm, and 32 mm were prepared.

[0373] First, the substrate of the image record is brought into contact with the mandrel, and the image record is bent 180 degrees with the substrate as the inner side. Then, the state of the image when it returns to its original planar shape is observed with the naked eye. Specifically, the tests were carried out in sequence from the mandrel with the largest diameter (32mm). If cracks or wrinkles are generated after the test, the test is terminated at that point. On the other hand, if cracks or wrinkles are not generated after the test, the test is carried out using the next mandrel with a smaller diameter until the test using a mandrel with a diameter of 8mm. The diameter of the mandrel when cracks or wrinkles are generated is taken as the "final diameter". The evaluation criteria are as follows. Grade 5 indicates the best bending resistance, and it can be said that the smaller the final diameter, the better the bending resistance.

[0374] 5: In the test using a mandrel with a diameter of 8 mm, no cracks or wrinkles were generated.

[0375] 4: The final diameter is 8mm, 10mm or 12mm.

[0376] 3: The final diameter is 13mm or 16mm.

[0377] 2: The final diameter is 19mm or 20mm.

[0378] 1: The final diameter is 25mm or 32mm.

[0379] (Adhesion)

[0380] After a NICHIBAN Co., Ltd. transparent tape (width 18 mm) was firmly attached to the surface of the image recording, the front end of the transparent tape was held and peeled off while maintaining an angle of 90 degrees. The surface of the image after peeling was observed with the naked eye. Adhesion was evaluated based on the peeling area of ​​the image relative to the adhesive surface of the transparent tape. The evaluation criteria are as follows. 3 or more is a level that does not cause problems in actual use.

[0381] 5: The peeling area is less than 5%.

[0382] 4: The peeling area is 5% or more and less than 10%.

[0383] 3: The peeling area is 10% or more and less than 20%.

[0384] 2: The peeling area is 20% or more and less than 30%.

[0385] 1: The peeling area is 30% or more.

[0386] - Scratch resistance -

[0387] After the image surface of the image recorded material was rubbed 10 times with cotton cloth while applying a load of 200 g, the state of the image surface and the cotton cloth was observed with the naked eye. The evaluation criteria were as follows.

[0388] 4: There was no change in the image side after rubbing, and no color transfer to the cotton cloth was observed.

[0389] 3: There was no change in the image surface after rubbing, and almost no color transfer to the cotton cloth was observed.

[0390] 2: Scratches were observed on the image surface after rubbing, and color transfer to the cotton cloth was observed.

[0391] 1: There is a portion where the base material is exposed on the image surface after wiping.

[0392] The evaluation results are shown in the following Tables 3 and 4. In Tables 3 and 4, "|Tgc-Tg1|" and "|Tgc-Tg2|" represent the absolute value of the difference between the glass transition temperature Tgc of the pigment dispersant contained in the magenta ink and the glass transition temperature Tg1 or Tg2 of the pigment dispersant contained in the white ink. In addition, in Tables 3 and 4, "|Magenta Mn-White Mn|" represents the absolute value of the difference between the number average molecular weight (Mn) of the pigment dispersant contained in the magenta ink and the number average molecular weight (Mn) of the pigment dispersant contained in the white ink. In Tables 3 and 4, "the proportion of structural units derived from monomers containing hydrocarbon groups greater than C4" represents the proportion of structural units derived from monomers having hydrocarbon groups greater than 4 carbon atoms relative to the total amount of polymers. "Structural units derived from monomers containing alicyclic hydrocarbon groups greater than C6" represents structural units derived from monomers having alicyclic hydrocarbon groups greater than 6 carbon atoms.

[0393] [Table 3]

[0394]

[0395]

[0396] As shown in Tables 3 and 4, Examples 1 to 14 include: a color ink containing a magenta pigment, a random polymer, and water; and a white ink containing a white pigment, a block polymer, and water. Therefore, it can be seen that the obtained image records have excellent bending resistance and adhesion.

[0397] On the other hand, in Comparative Example 1, since the pigment dispersant contained in the white ink is a random polymer, it is found that the bending resistance and the scratch resistance are inferior.

[0398] In Comparative Example 2, since the pigment dispersant contained in the magenta ink is a block polymer, it is found that the bending resistance and adhesion are poor.

[0399] In Comparative Example 3, the pigment dispersant contained in the magenta ink is a block polymer, and the pigment dispersant contained in the white ink is a random polymer, so it is found that the adhesion and scratch resistance are poor.

[0400] In Example 1, the maximum absolute value of the difference between the glass transition temperature Tgc of the pigment dispersant contained in the magenta ink and the glass transition temperatures Tg1 and Tg2 of the pigment dispersant contained in the white ink is 50° C. or more, and thus it is found that the bending resistance is superior to that of Example 2.

[0401] In Example 1, the minimum absolute value of the difference between the glass transition temperature Tgc of the pigment dispersant contained in the magenta ink and the glass transition temperatures Tg1 and Tg2 of the pigment dispersant contained in the white ink is 5° C. or more, and thus it is found that the bending resistance is superior to that of Example 3.

[0402] In Example 1, the glass transition temperature Tgc of the pigment dispersant contained in the magenta ink is lower than both the glass transition temperatures Tg1 and Tg2 of the pigment dispersant contained in the white ink. Therefore, it is found that the bending resistance is superior to that of Example 3.

[0403] In Example 1, the glass transition temperature Tgc of the pigment dispersant contained in the magenta ink is 150° C. or less, and the highest glass transition temperature Tg2 of the pigment dispersant contained in the white ink is 200° C. or less. Therefore, it is found that the bending resistance is superior to that of Example 4.

[0404] In Example 1, the pigment dispersant contained in the magenta ink and the pigment dispersant contained in the white ink are both polymers containing 30% by mass or more of a structural unit derived from a monomer having a hydrocarbon group having 4 or more carbon atoms, and therefore it is found that the adhesion is superior to that of Examples 5 to 7.

[0405] In Example 1, the pigment dispersant contained in the white ink is a polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group having 6 or more carbon atoms. Therefore, it is found that the adhesiveness and abrasion resistance are superior to those of Example 8.

[0406] In Example 1, the absolute value of the difference in number average molecular weight between the pigment dispersant contained in the magenta ink and the pigment dispersant contained in the white ink is 10,000 or more, and therefore, it is found that the bending resistance is superior to that of Example 9.

[0407] In Example 1, the number average molecular weight of the pigment dispersant contained in the magenta ink is larger than the number average molecular weight of the pigment dispersant contained in the white ink. Therefore, it is found that the bending resistance is superior to that of Example 10.

[0408] Since Example 14 used the pretreatment liquid, it was found that the bending resistance, adhesion, and scratch resistance were superior to those of Example 11.

Claims

1. An ink set comprising: A coloring ink comprising a coloring pigment, a first pigment dispersant, and water, wherein the coloring pigment is at least one selected from the group consisting of a color pigment and a black pigment; and White ink, containing white pigment, second pigment dispersant and water, The first pigment dispersant is a random polymer, The second pigment dispersant is a block polymer, When the glass transition temperature of the first pigment dispersant is Tgc and the n glass transition temperatures of the second pigment dispersant are Tg1 to Tgn, respectively, Tgc is 150° C. or less and the highest temperature among Tg1 to Tgn is 200° C. or less.

2. The ink set according to claim 1, wherein: The maximum absolute value of the difference between the Tgc and each of Tg1 to Tgn is 50° C. or more.

3. The ink set according to claim 1, wherein: The minimum absolute value of the difference between the Tgc and each of Tg1 to Tgn is 5° C. or more.

4. The ink set according to claim 2 or 3, wherein: The Tgc is a value lower than all of the Tg1 to Tgn.

5. The ink set according to claim 1 or 2, wherein: Both the first pigment dispersant and the second pigment dispersant are polymers containing 30% by mass or more of a structural unit derived from a monomer having a hydrocarbon group having 4 or more carbon atoms, based on the total amount of the polymer.

6. The ink set according to claim 1 or 2, wherein: The second pigment dispersant is a polymer containing a structural unit derived from a monomer having an alicyclic hydrocarbon group having 6 or more carbon atoms.

7. The ink set according to claim 1 or 2, wherein: An absolute value of a difference in number average molecular weight between the first pigment dispersant and the second pigment dispersant is 10,000 or more.

8. The ink set according to claim 1 or 2, wherein: The number average molecular weight of the first pigment dispersant is greater than the number average molecular weight of the second pigment dispersant.

9. The ink set according to claim 1 or 2, wherein: A pretreatment solution containing a coagulant is also provided.

10. An image recording method comprising the following steps: A step of applying the colored ink in the ink set according to any one of claims 1 to 9 to a non-permeable substrate by inkjet recording; and A step of applying the white ink in the ink set according to any one of claims 1 to 9 onto a colored ink film formed by applying the colored ink by an inkjet recording method.

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