Image recording method

Abstract

The present invention provides an image recording method including a step of discharging an ink containing water and a colorant as at least two types of droplets having different droplet sizes onto a substrate in a single pass by using an ink jet recording method, setting two types of droplets among the at least two types of droplets as first droplets and second droplets, and setting the first droplets and the second droplets as second droplets, v1, V2, a1, a2, and theta, which are parameters relating to the first droplet and the second droplet, satisfy formula (1) and formula (2). 0.45 < = V2 / V1 < = 0.9 (1) 3.5 < = {V11 / 3 * (1 + cos theta)} 2 * a1 + {V21 / 3 * (1 + cos theta)} 2 * a2 < = 7.0 (2).

Description

Technical Field

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

[0002] Various studies have been conducted on image recording methods.

[0003] For example, Japanese Patent Gazette No. 2010-075786 describes a pattern forming method in which droplets are sequentially ejected in one direction from an inkjet recording head having a nozzle for ejecting droplets containing functional components onto the surface of a substrate onto the surface of a substrate to form a linear pattern, wherein, with the diameter of the droplets before landing on the substrate surface being set to d and the contact angle of the droplets with respect to the substrate being set to θ, the inkjet recording head is controlled so that the dot spacing p between adjacent droplets on the substrate surface satisfies specific conditions, and the ratio of the volumes of volatile solvents contained in the droplets is set to a specific ratio.

[0004] Japanese Patent Gazette No. 2009-233612 describes a drawing method for drawing a pattern extending in a prescribed direction on a recording material by ejecting multiple droplets of three or more by inkjet. The drawing method is characterized in that the multiple droplets are divided into a plurality of groups each including at least a group consisting of two or more adjacent droplets and consisting of one droplet or two or more droplets, the droplets of each group consisting of two or more droplets overlap with the adjacent droplets of the same group and land on the recording material, the droplets at the end of each group land on the recording material with a gap between them and the droplets at the end of other adjacent groups, and wet and spread on the recording material, thereby merging with the droplets at the end of the other groups.

[0005] Japanese Patent Gazette No. 2016-112892 describes an image processing device that records an image on a recording medium by recording a first ink according to first quantization data and recording a second ink according to second quantization data. The image processing device is characterized in that it includes: a first quantization unit that quantizes multi-value data representing an intermediate concentration corresponding to the first ink to generate first quantization data; and a second quantization unit that quantizes multi-value data representing an intermediate concentration corresponding to the second ink to generate second quantization data, the surface tension of the first ink is greater than the surface tension of the second ink, and the dispersion of the first dot pattern recorded on the recording medium according to the first quantization data is higher than the dispersion of the second dot pattern recorded on the recording medium according to the second quantization data. Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] However, it is difficult to achieve both drying properties and suppression of streaks in recorded images.

[0008] The present invention has been made in view of such circumstances, and an object of one embodiment of the present invention is to provide an image recording method that is excellent in drying properties and can suppress streaks in a recorded image.

[0009] Means for solving technical problems

[0010] The present invention includes the following aspects.

[0011] <1>

[0012] An image recording method comprising the steps of: using an inkjet recording method to discharge ink containing water and a colorant as at least two types of droplets having different droplet sizes onto a substrate in a single pass;

[0013] In the step of setting two of the at least two types of droplets as a first droplet and a second droplet,

[0014] The size of the first droplet is V1 in pL.

[0015] The size of the second droplet is V2 in pL.

[0016] The ratio of the number of discharges of the first droplet to the total number of discharges of the first and second droplets is a1,

[0017] The ratio of the number of discharges of the second droplet to the total number of discharges of the first and second droplets is a2.

[0018] When the contact angle of the ink with respect to the contact surface with which the ink comes into contact due to the ejection of the ink is denoted as θ°,

[0019] V1, V2, a1, a2, and θ satisfy the following equations (1) and (2).

[0020] 0.45≤V2 / V1≤0.9……(1)

[0021] 3.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤7.0……(2)

[0022] The contact angle is a contact angle measured at a point in time when 300 milliseconds have passed since the ink was applied to the contact surface.

[0023] <2>

[0024] The image recording method according to <1>, wherein:

[0025] V1 and V2 satisfy the following formula (1A).

[0026] 0.5≤V2 / V1≤0.8……(1A)

[0027] <3>

[0028] The image recording method according to <1> or <2>, wherein:

[0029] V1, V2, a1, a2, and θ satisfy the following formula (2A).

[0030] 4.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤6.2……(2A)

[0031] <4>

[0032] The image recording method according to any one of <1> to <3>, wherein:

[0033] V1, V2, a1, a2, and θ satisfy the following formula (3).

[0034] [{V1 1 / 3 ×(1+cosθ)} 2 -{V2 1 / 3 ×(1+cosθ)} 2 ]×a1≤4.8……(3)

[0035] <5>

[0036] The image recording method according to any one of <1> to <4>, wherein:

[0037] The substrate is an impermeable substrate.

[0038] <6>

[0039] The image recording method according to any one of <1> to <5>, wherein

[0040] The colorant is white pigment.

[0041] <7>

[0042] The image recording method according to <6>, wherein:

[0043] The white colorant includes at least one selected from the group consisting of titanium dioxide and hollow particles.

[0044] <8>

[0045] The image recording method according to any one of <1> to <7>, further comprising the step of applying a pretreatment liquid containing a coagulant to the substrate,

[0046] In the ink discharge step, the ink is discharged onto the substrate to which the pretreatment liquid has been applied.

[0047] Effects of the Invention

[0048] According to one embodiment of the present invention, there is provided an image recording method that is excellent in drying properties and can suppress streaks in a recorded image. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 FIG. 1 is a diagram schematically showing an example of an image recording apparatus for implementing the image recording method of the present invention. DETAILED DESCRIPTION

[0050] In the present invention, a numerical range expressed using “to” indicates a range including the numerical values ​​before and after “to” as the minimum value and the maximum value, respectively.

[0051] In the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the upper limit or lower limit of another numerical range described in another stage. In addition, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the values ​​shown in the Examples.

[0052] In the present invention, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0053] In the present invention, a combination of two or more preferred embodiments is a more preferred embodiment.

[0054] In the present invention, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0055] In the present invention, the term “image” refers to an ink film itself when a single ink is used, and refers to a laminated film of multiple ink films when multiple inks are superimposed and used.

[0056] In the present invention, "image recording" means the formation of an image.

[0057] The concept of "image" in the present invention also includes a solid image.

[0058] [Image recording method]

[0059] The image recording method of the present invention includes the following step (hereinafter also referred to as "ink ejection step"): using an inkjet recording method, ejecting ink containing water and a colorant as at least two types of droplets of different sizes onto a substrate in a single pass, wherein two of the at least two types of droplets are designated as a first droplet and a second droplet, the size of the first droplet is designated as V1 (pL), the size of the second droplet is designated as V2 (pL), the ratio of the number of ejections of the first droplet to the total number of ejections of the first and second droplets is designated as a1, the ratio of the number of ejections of the second droplet to the total number of ejections of the first and second droplets is designated as a2, and the contact angle of the ink with respect to a contact surface contacted by the ink by ejection is designated as θ°, then V1, V2, a1, a2, and θ satisfy equations (1) and (2). The contact angle is the contact angle measured at a point 300 milliseconds after the ink is applied to the contact surface.

[0060] The image recording method of the present invention may include other steps in addition to the above-mentioned ink ejection step, as needed.

[0061] According to the image recording method of the present invention, the drying property is excellent and streaks in the recorded image can be suppressed.

[0062] This effect is achieved when parameters related to two types of liquid droplets, ie, the first liquid droplet and the second liquid droplet, among at least two types of liquid droplets in the ink ejection process satisfy equations (1) and (2).

[0063] Conventional image recording methods using inkjet recording devices allow for selection of paper in the inkjet recording device and halftoning appropriate for the selected paper. However, these methods have not focused on the expansion of the ink film formed by ejecting ink onto the substrate.

[0064] The inventors focused on the sizes of the first and second droplets, the number of times the first and second droplets are ejected, and the contact angle of the ink relative to the contact surface with which the ink contacts, and found that if these parameters satisfy equations (1) and (2), the drying properties are excellent and image stripes can be suppressed.

[0065] Hereinafter, the image recording method of the present invention will be described in more detail.

[0066] [Ink application process]

[0067] In the image recording method of the present invention, ink containing water and a colorant is discharged as at least two types of droplets having different droplet sizes onto a substrate in a single pass using an inkjet recording method.

[0068] In the present invention, a "liquid droplet" refers to one drop of ink ejected from an inkjet head.

[0069] <Formula (1), Formula (1A)>

[0070] In the image recording method of the present invention, ink is discharged as at least two types of droplets having different droplet sizes. Two of the at least two types of droplets are referred to as a first droplet and a second droplet. The first droplet is larger than the second droplet.

[0071] The method for measuring the size (ie, volume) of the droplet is not particularly limited, and examples thereof include a weight method and a camera photography method.

[0072] The gravimetric method is performed, for example, by the following method.

[0073] Discharge the ink into a measuring container a predetermined number of times. Measure the total mass of the droplets discharged into the measuring container. Calculate the droplet size using the following formula.

[0074] Droplet size (pL) = (total mass of ejected droplets (g) ÷ number of ejections) ÷ specific gravity of ink (g / cm 3 )×10 9

[0075] The camera photography method is performed, for example, by the following method.

[0076] An inkjet flying droplet observation device (product name "jetXpert", manufactured by imageXpert) was installed on the inkjet head. The droplet size was calculated by photographing the droplets.

[0077] V1 and V2 satisfy the following formula (1).

[0078] 0.45≤V2 / V1≤0.9……(1)

[0079] In formula (1),

[0080] V1 is the size of the first droplet, expressed in pL.

[0081] V2 is the size of the second droplet, expressed in pL.

[0082] When "V2 / V1" is 0.45 to 0.9, the degree of overlap between dots formed by ink ejection can be reduced, and the drying properties of the ink are excellent.

[0083] From the viewpoint of further improving drying properties, V1 and V2 preferably satisfy the following formula (1A) or (1B).

[0084] 0.5≤V2 / V1≤0.8……(1A)

[0085] 0.55≤V2 / V1≤0.7……(1B)

[0086] <Formula (2), Formula (2A)>

[0087] V1, V2, a1, a2, and θ satisfy the following formula (2).

[0088] 3.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤7.0……(2)

[0089] In formula (2),

[0090] V1 is the size of the first droplet.

[0091] V2 is the size of the second droplet.

[0092] a1 is the ratio of the number of discharges of the first liquid droplet to the total number of discharges of the first liquid droplet and the second liquid droplet.

[0093] a2 is the ratio of the number of discharges of the second liquid droplet to the total number of discharges of the first and second liquid droplets.

[0094] θ is the contact angle of ink with respect to the surface with which the ink comes into contact during ink discharge. The unit is "°".

[0095] "{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2″ is a parameter related to the degree of dot overlap on the substrate (hereinafter also referred to as “dot overlap parameter”).

[0096] When the dot overlap parameter is 3.5 or more, the dots formed by ejecting the ink are appropriately arranged on the substrate, and streaks in the image are suppressed.

[0097] When the dot overlap parameter is 7.0 or less, the degree of overlap between dots formed by ink ejection can be reduced, and the drying properties of the ink are excellent.

[0098] From the viewpoint of further improving drying properties and further suppressing streaks in an image, V1, V2, a1, a2, and θ preferably satisfy the following formula (2A) or (2B).

[0099] 4.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤6.2……(2A)

[0100] 5.0≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤6.0……(2B)

[0101] <Formula (3)>

[0102] V1, V2, a1, a2, and θ preferably satisfy the following formula (3).

[0103] [{V1 1 / 3 ×(1+cosθ)} 2 -{V2 1 / 3 ×(1+cosθ)} 2 ]×a1≤4.8……(3)

[0104] "[{V1 1 / 3 ×(1+cosθ)} 2 -{V2 1 / 3 ×(1+cosθ)} 2 ]×a1" is a parameter related to the sharpness of the image (hereinafter also referred to as "image sharpness parameter").

[0105] When the image sharpness parameter is 4.8 or less, the jaggedness of the boundary line between the portion where the image is recorded and the portion where the image is not recorded is reduced, thereby improving the sharpness of the image.

[0106] From the viewpoint of further improving the sharpness of the image, the image sharpness parameter is more preferably 4.0 or less, and even more preferably 2.4 or less. The lower limit of the image sharpness parameter is not particularly limited, and is, for example, 0.

[0107] [V1, V2]

[0108] The size V1 of the first droplet and the size V2 of the second droplet are not particularly limited as long as they satisfy the above-mentioned formulas (1) and (2).

[0109] From the viewpoint of suppressing streaks in an image, V1 is preferably 2.5 pL to 5.0 pL, and more preferably 3.0 pL to 4.5 pL.

[0110] V2 is smaller than V1, and is preferably 1.5 pL or more, and more preferably 1.8 pL or more, from the viewpoint of discharge reliability.

[0111] In the image recording method of the present invention, in addition to the first and second droplets, droplets of a size different from the first and second droplets may be discharged. The droplets of a size different from the first and second droplets may be larger than the first droplets, smaller than the second droplets, or smaller than the first droplets and larger than the second droplets.

[0112] From the viewpoint of further improving drying properties and further suppressing streaks in an image, it is preferable to discharge the ink as only two types of droplets (first droplets and second droplets) having mutually different droplet sizes.

[0113] 〔a1、a2〕

[0114] The ratio a1 of the number of discharges of the first liquid droplets and the ratio a2 of the number of discharges of the second liquid droplets are not particularly limited as long as they satisfy the above-mentioned formula (2).

[0115] a1 is preferably 0.05 to 0.95, more preferably 0.3 to 0.7.

[0116] a2 is preferably 0.05 to 0.95, more preferably 0.3 to 0.7.

[0117] In addition, the total of the ratio of the number of discharges of the first liquid droplet and the ratio of the number of discharges of the second liquid droplet is 1.

[0118] 〔θ〕

[0119] The contact angle of the ink with respect to the contact surface with which the ink comes into contact due to the discharge of the ink is not particularly limited as long as the above-mentioned formula (2) is satisfied.

[0120] From the viewpoint of further improving drying properties and further suppressing streaks in an image, θ is preferably 20° to 70°, and more preferably 30° to 65°.

[0121] The term "contact surface with which the ink contacts during ink discharge" refers to the surface with which the ink contacts the substrate when the ink is discharged onto the substrate. The contact surface only needs to be dry enough to prevent contact and mixing with the ink. For example, when the ink is discharged directly onto the substrate, the contact surface is the surface of the substrate. Furthermore, when ink is discharged after forming layer A on the substrate, the contact surface is the surface of layer A.

[0122] The contact angle is a contact angle measured at a point in time when 300 milliseconds have passed since the ink was applied to the contact surface.

[0123] “The time point when 300 milliseconds have passed since the ink was applied to the contact surface” indicates a state in which volatile components such as water and organic solvent contained in the ink have volatilized to a certain extent and the shape of the ink has been fixed.

[0124] When measuring the contact angle, the method of applying the ink to the contact surface is not particularly limited.

[0125] In the present invention, the contact angle is measured by the following method.

[0126] The contact angle is measured using a contact angle meter. For example, the contact angle meter (product name: "DM-501", manufactured by Kyowa Interface Science Co., Ltd.) is used to measure the contact angle at 20° C. and a droplet volume of 2.0 μL.

[0127] The contact angle of ink with respect to the contact surface with which the ink comes into contact due to ink ejection changes depending on the surface tension of the ink, the surface energy of the contact surface with which the ink comes into contact due to ink ejection, and the like.

[0128] The surface tension of ink changes depending on, for example, the content of the surfactant contained in the ink, the content of the organic solvent contained in the ink, and the like.

[0129] (Base material)

[0130] The substrate is not particularly limited as long as an ink image can be formed thereon, and examples thereof include paper, cloth, wood, metal, and plastic.

[0131] The substrate can be a permeable substrate or a non-permeable substrate.

[0132] In the image recording method of the present invention, when a non-permeable substrate is used as the substrate, the drying effect and the effect of suppressing image streaks are high. Therefore, the substrate is preferably a non-permeable substrate.

[0133] In the present invention, impermeability in an impermeable substrate refers to a property where the water absorption rate is 2.5% or less within 24 hours, as measured in accordance with ASTM D570-98 (2018). The unit "%" for water absorption is based on mass. The water absorption rate is preferably 1.0% or less, and more preferably 0.5% or less.

[0134] 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.).

[0135] The material of the impermeable substrate is preferably a resin. In other words, the impermeable substrate is preferably a resin substrate.

[0136] 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.

[0137] The shape of the impermeable substrate is preferably a sheet (film) or plate. Examples of such impermeable substrates include glass plates, metal plates, resin sheets (resin films), plastic-laminated paper, metal-laminated or vapor-deposited paper, and metal-laminated or vapor-deposited plastic sheets (plastic films).

[0138] Examples of the resin-made impermeable substrate include resin sheets (resin films), and specifically, flexible packaging materials for packaging food and the like, and floor guide panels for mass retail stores.

[0139] Examples of the impermeable substrate include sheet-shaped (film-shaped) or plate-shaped impermeable substrates and also include textiles (woven fabrics) and nonwoven fabrics formed of impermeable fibers.

[0140] The impermeable substrate may be subjected to a hydrophilic treatment. Examples of hydrophilic treatments include, but are not limited to, corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., UV treatment), and flame treatment. Corona treatment can be performed using, for example, Corona Master (product name "PS-10S," manufactured by Shinko Electric & Instrumentation Co., Ltd.). The conditions for the corona treatment can be appropriately selected depending on the type of impermeable substrate.

[0141] The non-permeable substrate may be a transparent non-permeable substrate.

[0142] Here, transparency means that the transmittance of visible light with a wavelength of 400 nm to 700 nm is 80% or more (preferably 90% or more).

[0143] When the impermeable substrate is a transparent impermeable substrate, the image can be easily visually recognized through the impermeable substrate from the image non-recording surface side of the impermeable substrate.

[0144] For example, in the case where the non-permeable substrate is a transparent non-permeable substrate, when the pre-treatment liquid described later, the non-white ink described later, and the white ink described later are sequentially applied to the non-permeable substrate to record an image, the non-white image (e.g., a pattern image such as characters or graphics) with a white image (e.g., a solid image) as a background can be easily visually recognized through the non-permeable substrate from the image non-recording side of the non-permeable substrate.

[0145] (Ink)

[0146] In the image recording method of the present invention, the ink contains water and a colorant.

[0147] -water-

[0148] The ink contains water.

[0149] The water content is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, and particularly preferably 50% by mass or more, relative to the total amount of the ink.

[0150] The upper limit of the water content relative to the total amount of the ink is appropriately determined depending on the contents of other components, but is, for example, 99% by mass, preferably 95% by mass, and more preferably 90% by mass.

[0151] -Colorant-

[0152] Ink contains colorant.

[0153] In the present invention, the colorant refers to a substance that, when contained in ink, can make the ink a color ink or an achromatic ink.

[0154] Examples of the colorant include dyes and pigments, of which pigments are preferred from the viewpoint of durability.

[0155] The pigment may be any of commercially available organic pigments and inorganic pigments.

[0156] Examples of the pigment include those described in "Encyclopedia of Pigments" (2000) edited by Seishiro Ito, "Industrial Organic Pigments" by W. Herbst, K. Hunger, JP-A-2002-12607, JP-A-2002-188025, JP-A-2003-26978, and JP-A-2003-342503.

[0157] Furthermore, the pigment may be a water-insoluble pigment that can be dispersed in water using a dispersant, or a self-dispersible pigment.

[0158] Self-dispersible pigments are pigments that can be dispersed in water without using a dispersant.

[0159] Self-dispersible pigments are compounds in which at least one selected from the group consisting of hydrophilic groups such as carbonyl, hydroxyl, carboxyl, sulfo, and phosphoric acid groups and salts thereof is chemically bonded to the pigment surface directly or via other groups.

[0160] The colorant may be a chromatic colorant (eg, cyan, magenta, yellow, etc.) or an achromatic colorant (eg, white and black).

[0161] Among them, the colorant is preferably a white colorant. A white image recorded using white ink containing a white colorant can have a non-white image (eg, a pattern image such as a character or graphic) as a background.

[0162] Examples of the white colorant include white pigments such as titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, zinc oxide, zinc sulfide, mica, talc, and pearl.

[0163] From the perspective of concealability, the average primary particle size of the white pigment is preferably 150 nm or greater, more preferably 200 nm or greater. Furthermore, from the perspective of ink ejection properties, the average primary particle size of the white pigment is preferably 400 nm or less, more preferably 350 nm or less. The average primary particle size of the white pigment is preferably between 150 nm and 400 nm.

[0164] In the present invention, the average primary particle size of the white pigment is a value measured using a transmission electron microscope (TEM). Specifically, it is a value obtained by selecting 50 random white pigments present in the field of view observed by TEM, measuring the primary particle sizes of the 50, and averaging the values. As a transmission electron microscope, a transmission electron microscope 1200EX manufactured by JEOL Ltd. can be used.

[0165] The white colorant can be hollow particles. Hollow particles are particles with internal voids. By incorporating hollow particles into ink based on the refractive index difference between the outer shell and the voids of the hollow particles, a white ink can be obtained.

[0166] Examples of the hollow particles include hollow resin particles and inorganic hollow particles.

[0167] Examples of the resin constituting the hollow resin particles include acrylic resins, styrene-acrylic resins, cross-linked styrene-acrylic resins, urethane resins, and maleic acid-based copolymers.

[0168] Examples of the inorganic material constituting the inorganic hollow particles include silicon dioxide, aluminum oxide, titanium dioxide, and zinc oxide.

[0169] Among them, the white colorant preferably contains at least one selected from the group consisting of titanium dioxide and hollow particles.

[0170] From the viewpoint of image density and ejection properties, the content of the colorant is preferably 2 to 25% by mass, more preferably 5 to 25% by mass, and even more preferably 10 to 20% by mass relative to the total amount of the ink.

[0171] -Resin-

[0172] The ink preferably contains at least one resin.

[0173] The resin in the ink contributes to the film-forming property of the ink (ie, the formability of the ink film).

[0174] The weight average molecular weight (Mw) of the resin is preferably 1,000 to 300,000, more preferably 2,000 to 200,000, and even more preferably 5,000 to 100,000.

[0175] In the present invention, unless otherwise specified, the weight average molecular weight (Mw) represents a value measured by gel permeation chromatography (GPC).

[0176] Gel permeation chromatography (GPC) measurements were performed using an HLC (registered trademark)-8020GPC (TOSOH CORPORATION) as the measuring apparatus, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, TOSOH CORPORATION) columns, and THF (tetrahydrofuran) as the eluent. Measurement conditions included a sample concentration of 0.45% by mass, a flow rate of 0.35 ml / min, a sample injection volume of 10 μl, and a measurement temperature of 40°C, with an RI detector.

[0177] The calibration curve was prepared using eight samples of TOSOH CORPORATION's "TSK standard, polystyrene": "F-40," "F-20," "F-4," "F-1," "A-5000," "A-2500," "A-1000," and "n-propylbenzene."

[0178] Examples of the resin include pigment dispersion resins serving as pigment dispersants.

[0179] Resin particles can also be mentioned as the resin.

[0180] The ink may also contain at least one pigment dispersing resin.

[0181] The pigment-dispersing resin is a resin having a function of dispersing a pigment.

[0182] The pigment dispersing resin may be a random copolymer or a block copolymer.

[0183] The pigment dispersing resin may have a cross-linked structure.

[0184] The ink can be prepared using a pigment dispersion containing a pigment and a pigment dispersing resin.

[0185] As the pigment-dispersing resin, for example, a known polymer dispersant such as the polymer dispersants described in paragraphs 0029 to 0106 of International Publication No. 2021 / 221069 can be used.

[0186] When the ink contains a pigment dispersion resin, the ratio of the pigment content in the ink to the pigment dispersion resin content is preferably 1:0.04 to 1:3, more preferably 1:0.05 to 1:1, and even more preferably 1:0.05 to 1:0.5 on a mass basis.

[0187] When the ink contains a pigment dispersion resin, the content of the pigment dispersion resin is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and even more preferably 0.5 to 2.5% by mass, relative to the total amount of the ink.

[0188] The ink may contain at least one type of resin particles.

[0189] The resin constituting the resin particles is preferably a water-insoluble resin. The term "water-insoluble" in a water-insoluble resin refers to a property in which the resin dissolves less than 2 g in 100 g of distilled water at 25°C.

[0190] The volume average particle size of the resin particles is preferably 1 nm to 300 nm, more preferably 3 nm to 200 nm, and even more preferably 5 nm to 150 nm.

[0191] In the present invention, the volume average particle size refers to a value measured using a laser diffraction / scattering particle size distribution analyzer.

[0192] As a measuring apparatus, the particle size distribution measuring apparatus "Microtrac MT-3300II" (made by Nikkiso Co., Ltd.) is mentioned, for example.

[0193] The resin particles are preferably at least one selected from the group consisting of acrylic resin particles, ester resin particles, a mixture of acrylic resin particles and ester resin particles, composite particles containing acrylic resin and ester resin, styrene acrylic resin particles, and polyurethane resin particles.

[0194] In the present invention, acrylic resin refers to a polymer (homopolymer or copolymer) containing at least one raw material monomer selected from the group consisting of acrylic acid, acrylic acid derivatives (eg, acrylic esters), methacrylic acid, and methacrylic acid derivatives (eg, methacrylic esters).

[0195] From the viewpoint of further improving the abrasion resistance of the image, the glass transition temperature (Tg) of the resin particles is preferably 50°C to 250°C, more preferably 50°C to 150°C.

[0196] Here, the glass transition temperature (Tg) of the resin particles is measured Tg obtained by actual measurement. For the measurement method of the measured Tg, reference can be made to paragraph 0111 of Japanese Patent Application Laid-Open No. 2015-25076.

[0197] Regarding the resin particles, for example, reference can be made to paragraphs 0038 to 0114 of International Publication No. 2021 / 192720 and paragraphs 0109 to 0120 of Japanese Patent Application Laid-Open No. 2015-25076.

[0198] When the ink contains resin particles, the content of the resin particles in the ink is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, relative to the total amount of the ink.

[0199] -Water-soluble organic solvents-

[0200] The ink preferably contains at least one water-soluble organic solvent.

[0201] This ensures the stability of ejection from the inkjet head.

[0202] The water-soluble organic solvent contained in the ink may be one kind or two or more kinds.

[0203] In the present invention, the "water-soluble" in the "water-soluble organic solvent" means a property of dissolving 1 g or more in 100 g of water at 25°C.

[0204] The type of water-soluble organic solvent that can be contained in the ink is not limited, and examples thereof include:

[0205] Monoalcohols with 1 to 4 carbon atoms;

[0206] 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol and other diols;

[0207] Triols such as glycerol, 1,2,6-hexanetriol, and trimethylolpropane;

[0208] Alkylene glycols such as ethylene glycol and propylene glycol;

[0209] Alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether;

[0210] Polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, and polyoxyethylene polyoxypropylene glycol;

[0211] Polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, and polyoxypropylene glycerol ether; and

[0212] 2-pyrrolidone, N-methyl-2-pyrrolidone; etc.

[0213] From the viewpoint of ejection stability, the water-soluble organic solvent in the ink preferably contains at least one selected from the group consisting of alkylene glycols and alkylene glycol monoalkyl ethers.

[0214] The content of the water-soluble organic solvent is preferably 10% by mass to 40% by mass, and more preferably 15% by mass to 30% by mass, relative to the total amount of the ink.

[0215] -additive-

[0216] The ink may contain additives such as a surfactant, a water-soluble resin, a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and an alkaline compound as needed.

[0217] -Physical properties-

[0218] From the viewpoint of improving ejection stability, the pH (25° C.) of the ink is preferably 7 to 10, more preferably 7.5 to 9.5.

[0219] The pH of the ink is measured at 25° C. using a pH meter, for example, a pH meter manufactured by DKK-TOA CORPORATION (product name “WM-50EG”).

[0220] The viscosity of the ink (25° C.) is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, preferably 2 mPa·s to 15 mPa·s, and further preferably 3 mPa·s to 10 mPa·s.

[0221] The viscosity of the ink is measured at 25° C. using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0222] The surface tension of the ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 25 mN / m to 40 mN / m.

[0223] The surface tension of the ink is measured at 25° C. using a surface tensiometer, for example, an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”) and a plate method.

[0224] (Ink dispensing method)

[0225] In the ink ejection step, the ink is ejected in a single pass using an inkjet recording method.

[0226] The ink ejection method in the inkjet recording method is not particularly limited and can be any of the well-known methods, such as a charge control method that utilizes electrostatic induction force to eject 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 ink to eject the ink using radiation pressure, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and utilizes the generated pressure.

[0227] As an inkjet recording method, the method described in Japanese Patent Application Laid-Open No. 54-59936 can be particularly effective. This method involves using the force generated by the sudden change in volume of ink upon exposure to thermal energy to cause the ink to be ejected from the nozzle. The method described in paragraphs 0093 to 0105 of Japanese Patent Application Laid-Open No. 2003-306623 can also be applied as an inkjet recording method.

[0228] The step of applying ink to a substrate by an inkjet recording method is performed by ejecting ink from nozzles of an inkjet head.

[0229] As inkjet head methods, there are a reciprocating method (multi-pass method) in which a short strip serial head is used to scan and record in the width direction of the recording medium, and a linear method (single-pass method) in which a line head is used in which recording elements are arranged corresponding to the entire area of ​​one side of the recording medium.

[0230] In the linear method, the image can be recorded across the entire surface of the recording medium by scanning the recording medium in a direction intersecting the arrangement of the recording elements. The linear method eliminates the need for a transport system such as a carriage, as used in the reciprocating method to scan the short stripe-shaped printhead. Furthermore, compared to the reciprocating method, the linear method eliminates the need for carriage movement and complex scanning control of the recording medium; only the recording medium moves. Therefore, the linear method achieves faster image recording speeds than the reciprocating method.

[0231] The ink is preferably applied using an inkjet head having a resolution of 300 dpi or higher (more preferably 600 dpi or higher, and even more preferably 800 dpi or higher). Dpi stands for dots per inch, and 1 inch is 2.54 cm.

[0232] [Ink drying process]

[0233] The image recording method of the present invention may include a step of drying the ink discharged onto the substrate after the ink discharge step (hereinafter also referred to as “ink drying step”).

[0234] The ink drying method is not particularly limited, and examples thereof include infrared (IR) drying, warm air drying (eg, a dryer), and heat drying using a heating device (eg, a heater, a hot plate, a heating furnace, etc.).

[0235] As the heat drying method, a method of combining two or more of these may be used.

[0236] Heat drying can be performed by heating the ink from at least one of the image recording surface side and the non-image recording surface side of the substrate.

[0237] The heating temperature during heat drying of the ink is preferably 35° C. or higher, more preferably 40° C. or higher, further preferably 50° C. or higher, and further preferably 60° C. or higher.

[0238] The upper limit of the heating temperature is not particularly limited, but is preferably 100°C, more preferably 90°C.

[0239] The heating time for heat drying the ink is not particularly limited, but is preferably 1 to 180 seconds, more preferably 1 to 120 seconds, and even more preferably 1 to 60 seconds.

[0240] [Pretreatment liquid application process]

[0241] The image recording method of the present invention preferably further includes a step of applying a pretreatment liquid containing a coagulant (hereinafter also referred to as a "pretreatment liquid applying step"). When the pretreatment liquid applying step is included, in the ink ejection step, the ink is ejected onto the substrate to which the pretreatment liquid has been applied.

[0242] The ink is preferably discharged directly onto the substrate to which the pre-treatment liquid is applied. In this case, in the formula (2), θ is the contact angle of the ink with respect to the surface of the substrate to which the pre-treatment liquid is applied.

[0243] By providing a pretreatment liquid application process before the ink ejection process, the components contained in the ink (for example, pigment dispersion resin, resin particles, etc.) are aggregated by the coagulant contained in the pretreatment liquid, making it difficult for the ink to spread on the substrate, thereby suppressing landing interference.

[0244] (Pretreatment liquid)

[0245] -water-

[0246] The pretreatment liquid preferably contains water.

[0247] The water content is preferably 50% by mass or more, more preferably 60% by mass or more, based on the total amount of the pretreatment liquid.

[0248] The upper limit of the water content also depends on the amounts of other components, but is preferably 90% by mass or less, more preferably 80% by mass or less, based on the total amount of the pretreatment liquid.

[0249] - Coagulant -

[0250] The pretreatment liquid contains at least one coagulant.

[0251] The coagulant in the pre-treatment liquid aggregates the components of the ink on the substrate, thereby improving the image quality.

[0252] The coagulant is preferably at least one selected from the group consisting of organic acids, polyvalent metal compounds, metal complexes, and cationic polymers.

[0253] Preferred examples of the coagulant include those described in paragraphs 0122 to 0130 of International Publication No. 2020 / 195360.

[0254] Hereinafter, preferred embodiments of each of the organic acid, the polyvalent metal compound, the metal complex, and the cationic polymer that can be used as the coagulant will be described.

[0255] --Organic acid--

[0256] Examples of the organic acid include organic compounds having an acidic group.

[0257] 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, and a carboxyl group.

[0258] 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.

[0259] It is preferred that at least a part of the acidic groups be dissociated in the pretreatment liquid.

[0260] 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, pyronecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid, and nicotinic acid.

[0261] 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.

[0262] 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.

[0263] The organic acid preferably has a low pKa (e.g., 1.0 to 5.0). This reduces the surface charge of particles such as pigments and resin particles in the ink stabilized by weakly acidic functional groups such as carboxyl groups by contact with the organic acid with a lower pKa, thereby reducing dispersion stability.

[0264] 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 range lower than the pKa of the functional group (e.g., carboxyl group) that stabilizes particle dispersion in the ink.

[0265] --Polyvalent Metal Compounds--

[0266] Examples of the polyvalent metal compound include polyvalent metal salts.

[0267] Examples of the polyvalent metal salt include organic acid polyvalent metal salts and inorganic acid polyvalent metal salts.

[0268] As the organic acid polyvalent metal salt, polyvalent metal salts of the above-mentioned organic acids (for example, formic acid, acetic acid, benzoic acid, etc.) are preferred.

[0269] As the inorganic acid polyvalent metal salt, a nitrate polyvalent metal salt, a hydrochloric acid polyvalent metal salt or a thiocyanate polyvalent metal salt is preferable.

[0270] Examples of polyvalent metal salts include salts of alkaline earth metals of Group 2 of the periodic table (e.g., magnesium and calcium), salts of transition metals of Group 3 of the periodic table (e.g., lanthanum), salts of metals of Group 13 of the periodic table (e.g., aluminum), and salts of lanthanides (e.g., neodymium).

[0271] The polyvalent metal salt is preferably a calcium salt, a magnesium salt or an aluminum salt, more preferably a calcium salt or a magnesium salt.

[0272] The polyvalent metal compound is preferably an organic acid polyvalent metal salt, more preferably an organic acid calcium salt or an organic acid magnesium salt.

[0273] It is preferred that at least a portion of the polyvalent metal compound is dissociated into polyvalent metal ions and counter ions in the pretreatment liquid.

[0274] --Metal Complex--

[0275] The metal complex preferably contains at least one selected from the group consisting of zirconium, aluminum, and titanium as a metal element.

[0276] The metal complex is preferably a metal complex containing at least one ligand selected from the group consisting of acetate, acetylacetonate, methyl acetoacetate, ethyl acetoacetate, octanediol, butoxyacetylacetone, lactate, ammonium lactate, and triethanolaminate.

[0277] The metal complex can be a commercially available product. Various organic ligands, particularly various multidentate ligands capable of forming metal chelate catalysts, are commercially available. Therefore, the metal complex can be a metal complex prepared by combining a commercially available organic ligand and a metal.

[0278] --Cationic polymer--

[0279] The cationic polymer is preferably a homopolymer of a cationic monomer having a primary or tertiary amino group or a quaternary ammonium salt group, or a copolymer or polycondensate of a cationic monomer and a non-cationic monomer. The cationic polymer can be used in the form of a water-soluble polymer or a water-insoluble polymer (i.e., latex particles).

[0280] Examples of the cationic polymer include polyvinyl pyridinium salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinyl imidazoles, polyethylene imines, polybiguanides, polyguanidines, polyallylamines, and derivatives thereof.

[0281] From the perspective of the viscosity of the pretreatment liquid, the cationic polymer preferably has a low weight-average molecular weight. When the pretreatment liquid is applied to the resin substrate by inkjet recording, the weight-average molecular weight is preferably 1,000 to 500,000, more preferably 1,500 to 200,000, and even more preferably 2,000 to 100,000. A weight-average molecular weight of 1,000 or more is advantageous from the perspective of aggregation speed. A weight-average molecular weight of 500,000 or less is advantageous from the perspective of ejection reliability. However, when the pretreatment liquid is applied to the resin substrate by methods other than inkjet recording, the present invention is not limited to this.

[0282] The content of the coagulant in the pretreatment liquid is preferably 0.1 to 40% by mass, more preferably 0.1 to 30% by mass, further preferably 1 to 20% by mass, and even more preferably 1 to 10% by mass, relative to the total amount of the pretreatment liquid.

[0283] -Resin-

[0284] The pretreatment liquid preferably contains at least one resin.

[0285] The resin in the pretreatment liquid contributes to the film-forming property of the pretreatment liquid (ie, the formability of the pretreatment liquid film).

[0286] As the resin in the pre-treatment liquid, the same resin as that in the ink (for example, resin particles) can be used.

[0287] The content of the resin in the pretreatment liquid is not particularly limited.

[0288] The content of the resin is preferably 0.5% by mass to 30% by mass, more preferably 1% by mass to 20% by mass, and particularly preferably 1% by mass to 15% by mass, relative to the total amount of the pretreatment liquid.

[0289] -Water-soluble organic solvents-

[0290] The pretreatment liquid may contain at least one water-soluble organic solvent.

[0291] As the water-soluble organic solvent in the pre-treatment liquid, the same water-soluble organic solvent as that which can be contained in the ink can be used.

[0292] -additive-

[0293] The pretreatment liquid may contain additives such as a surfactant, a water-soluble resin, a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and an alkaline compound as needed.

[0294] -Physical properties-

[0295] The pH (25° C.) of the pretreatment liquid is preferably 2.0 to 7.0, more preferably 2.0 to 4.0. The pH of the pretreatment liquid is measured by the same method as the pH of the ink.

[0296] From the perspective of coating properties, the viscosity of the pretreatment liquid is preferably 0.5 to 10 mPa·s, more preferably 1 to 5 mPa·s. The viscosity is measured at 25°C using a viscometer. The viscosity of the pretreatment liquid is measured using the same method as the viscosity of the ink.

[0297] The surface tension of the pretreatment liquid is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and even more preferably 30 mN / m to 45 mN / m. The surface tension is measured at 25°C. The surface tension of the pretreatment liquid is measured using the same method as the surface tension of the ink.

[0298] (Method of applying pretreatment liquid)

[0299] The method for applying the pretreatment liquid is not particularly limited, and examples thereof include known methods such as a coating method, a dipping method, and an inkjet recording method.

[0300] Examples of the coating method include known methods using a bar coater, extrusion die coater, air knife coater, blade coater, rod coater, knife coater, extrusion coater, reverse roll coater, and the like.

[0301] The application of the pretreatment liquid is preferably performed by a coating method.

[0302] [Pretreatment liquid drying process]

[0303] The image recording method of the present invention may include a step of drying the pre-treatment liquid applied to the substrate after the pre-treatment liquid application step.

[0304] The method for drying the pretreatment liquid is not particularly limited, and for example, the same method as exemplified as the method for drying the ink can be applied.

[0305] The preferred ranges of drying conditions (for example, heating temperature and heating time) for the pre-treatment liquid are the same as the preferred ranges of drying conditions for the ink.

[0306] [Other processes]

[0307] In the image recording method of the present invention, as described above, the colorant contained in the ink is preferably a white colorant. That is, the ink discharged in the ink discharge step is preferably a white ink.

[0308] When white ink is discharged in the ink discharge step, a step of recording a non-white image using non-white ink may be included before or after the ink discharge step.

[0309] The non-white ink refers to colored inks other than white ink (for example, cyan ink, magenta ink, yellow ink, and black ink).

[0310] The non-white image refers to an image recorded using non-white ink (for example, a cyan image, a magenta image, a yellow image, and a black image).

[0311] The non-white image may be an image recorded using only one type of non-white ink, or may be an image recorded using two or more types of non-white inks.

[0312] As an example of a method for recording a non-white image before the ink ejection step, a method in which a non-white image (e.g., a pattern image such as characters or graphics) is placed between the substrate and a white image (e.g., a solid image) can be cited. In this method, the non-white image is visually recognized through the substrate from the non-image recording side of the substrate against the white image as a background.

[0313] An example of a method for recording a non-white image after the ink ejection step is a method in which a non-white image (e.g., a pattern image such as characters or graphics) is placed on a white image (e.g., a solid image). In this method, the non-white image (e.g., a pattern image such as characters or graphics) is visually recognized against a white image (e.g., a solid image) as a background from the image recording surface of the substrate.

[0314] From the viewpoint of more effectively suppressing blocking of a multicolor image including a white image and a non-white image, it is preferred that the non-white image be recorded before the ink ejection step and arranged between the substrate and the white image.

[0315] <Example of an Image Recording Device>

[0316] Figure 1 FIG. 1 is a diagram schematically showing an example of an image recording apparatus used in the image recording method of the present invention.

[0317] like Figure 1 As shown, one embodiment of the inkjet recording device is an example of an inkjet recording device having a conveying mechanism for conveying a resin substrate in a roll-to-roll manner, and is a device as follows: a substrate A1 in the shape of a long film wound into a roll is unwound by a unwinding device R1, and the unwound substrate A1 is conveyed in the direction of the solid arrow under the application of tension, so that it passes through the pretreatment liquid imparting device P1, the pretreatment liquid drying area DP1, the first inkjet head IJ1, the first drying area D1, the second inkjet head IJ2 and the drying area D2 in sequence, and finally is wound by the winding device R2 including a winding core under the application of tension P.

[0318] The substrate A1 is conveyed while being tensioned and wound while being tensioned P. The tension during conveyance may be the same as or different from the tension P during winding. Furthermore, the tension may vary depending on the position in the conveyance direction or may be the same.

[0319] The image recording apparatus according to one embodiment may include a tension adjustment mechanism for adjusting the tension of the impermeable substrate.

[0320] As the tension adjustment mechanism, there are:

[0321] A magnetic powder brake (Powder Brake) provided on the unwinding device R1 and / or the rewinding device R2;

[0322] A dancer roller disposed along the conveying path; and

[0323] A control device (for example, a tension controller) that controls each tension by adjusting various conditions of the image recording device.

[0324] Furthermore, the image recording apparatus according to one embodiment may include a tension measuring mechanism (for example, a tensiometer) for measuring the tension of the non-permeable substrate.

[0325] in addition, Figure 1 Since this is a schematic diagram, the conveyance path of the substrate A1 is simplified and shown as being conveyed in one direction. However, it goes without saying that in reality, the conveyance path of the substrate A1 may be tortuous.

[0326] As a conveyance method for the substrate A1 , various web conveyance methods such as a drum and a roll can be appropriately selected.

[0327] Relative to the unwinding device R1 for unwinding the substrate A1, on the downstream side of the conveying direction of the substrate A1, the pretreatment liquid imparting device P1, the pretreatment liquid drying area DP1, the first inkjet head IJ1, the first drying area D1, the second inkjet head IJ2 and the drying area D2 are arranged in sequence from the upstream side of the conveying direction of the substrate A1.

[0328] The pre-treatment liquid applying device P1 , the first inkjet head IJ1 , and the second inkjet head IJ2 respectively apply the pre-treatment liquid, apply the first ink, and apply the second ink.

[0329] At this time, at least one of heating and drying the pretreatment liquid in the pretreatment liquid drying area DP1 , heating and drying the first ink in the first drying area D1 , and heating and drying the second ink in the second drying area D2 can be performed.

[0330] In the first drying area D1 , in addition to the heating and drying of the first ink, the heating and drying of the pre-treatment liquid can also be substantially performed.

[0331] In the second drying area D2 , in addition to the heating and drying of the second ink, the heating and drying of the pre-treatment liquid and / or the heating and drying of the first ink can be substantially performed.

[0332] Furthermore, if the resin substrate is passed through each drying zone in a state where the temperature of each drying zone is set to room temperature, heating and drying can be omitted.

[0333] In one embodiment, the first ink is either a non-white ink containing water and a colorant for recording a non-white image or a white ink containing water and a colorant for recording a white image, and the second ink is the other of the non-white ink and the white ink.

[0334] A surface treatment unit (not shown) for performing a surface treatment (preferably a corona treatment) on at least one of the front and back surfaces of the substrate A1 may be provided upstream of the pretreatment liquid applying device P1.

[0335] Furthermore, a cooling zone for cooling the recorded multi-color image (ie, a multi-color image including a white image and a non-white image) may be provided downstream of the second drying zone D2.

[0336] The first inkjet head IJ1 and the second inkjet head IJ2 may be shuttle heads, but from the viewpoint of increasing the speed of image recording, they are preferably line heads having a plurality of ejection ports (nozzles) arranged in the width direction of the long film-shaped substrate A1.

[0337] There may be only one or more first inkjet head IJ1 and second inkjet head IJ2.

[0338] As an example of a combination of the first inkjet head IJ1 and the second inkjet head IJ2, the following combination can be cited: the first inkjet head IJ1 is four inkjet heads corresponding to the four colors of cyan, magenta, yellow and black (Note: these four inkjet heads are arranged along the conveying direction of the resin substrate), and the second inkjet head IJ2 is one inkjet head corresponding to white (i.e., white).

[0339] Furthermore, as another example of the combination of the first inkjet head IJ1 and the second inkjet head IJ2, the following combination can also be cited: the first inkjet head IJ1 is an inkjet head corresponding to white, and the second inkjet head IJ2 is four inkjet heads corresponding to the four colors of cyan, magenta, yellow and black (Note: these four inkjet heads are arranged along the conveying direction of the substrate).

[0340] In inkjet recording using the image recording apparatus according to one embodiment,

[0341] First, the long film-shaped substrate A1 wound into a roll is unwound by the unwinding device R1.

[0342] The unwound substrate A1 is conveyed in the direction of the solid arrow under tension.

[0343] The pre-treatment liquid applying device P1 applies the pre-treatment liquid to the transported substrate A1.

[0344] Next, the pre-treatment liquid is dried in the pre-treatment liquid drying area DP1 as needed.

[0345] Next, the first ink (ie, either non-white ink or white ink) is applied by the first inkjet head IJ1.

[0346] Next, the first ink is dried in the first drying area D1 as needed.

[0347] Next, the second ink (i.e., the other of the non-white ink and the white ink) is applied by the second inkjet head IJ2.

[0348] Next, the second ink is dried in the second drying area D2 as needed.

[0349] Thus, a multicolor image can be obtained including a first image derived from the first ink (i.e., one of the non-white image and the white image) and a second image derived from the second ink (i.e., the other of the non-white image and the white image).

[0350] Next, the obtained multi-color image is cooled as needed, and finally the substrate A1 with the multi-color image is wound up with tension P applied thereto by a winding device R2 including a winding core.

[0351] In addition, the application and drying of the pretreatment liquid in one embodiment may be omitted.

[0352] Furthermore, in one embodiment, only a white image may be recorded without recording a non-white image.

[0353] Example

[0354] Examples of the present invention are shown below, but the present invention is not limited to the following examples.

[0355] Preparation of white ink

[0356] (Preparation of white pigment dispersion)

[0357] -Synthesis of Pigment Dispersant P1-

[0358] 965 g of dipropylene glycol was added to a 5000 mL three-necked flask equipped with a stirrer and a cooling tube, and the mixture was heated to 85° C. under a nitrogen atmosphere.

[0359] Solution I and solution II were prepared separately. Solution I was obtained by dissolving 640 g of benzyl methacrylate, 340 g of methacrylic acid, and 19.94 g of 2-mercaptopropionic acid in 370.28 g of dipropylene glycol.

[0360] The solution II was obtained by dissolving 17.69 g of tert-butyl peroxy-2-ethylhexanoate (product name: "PERBUTYL O", manufactured by NOF CORPORATION) in 221.17 g of dipropylene glycol.

[0361] Solution I was added dropwise to the three-necked flask over 4 hours, and solution II was added dropwise over 5 hours. After the addition was completed, the mixture was allowed to react for another 2 hours.1 H-NMR confirmed the disappearance of the monomer.

[0362] The obtained reaction solution was heated to 70°C, 248.02 g of a 50% by mass potassium hydroxide aqueous solution was added, and then 107.48 g of dipropylene glycol and 75.52 g of pure water were added and stirred to obtain a 37% by mass solution of a random polymer. This random polymer was used as pigment dispersant P1.

[0363] pass 1 The structural units constituting the obtained random polymer were confirmed by H-NMR. Furthermore, the weight average molecular weight (Mw) was determined by GPC. The obtained pigment dispersant P1 had a weight average molecular weight (Mw) of 8400 and an acid value of 221.7 mgKOH / g.

[0364] -Preparation of white pigment dispersion-

[0365] Pigment dispersant P1 (150 parts by mass) was dissolved in water to prepare a polymer solution having a concentration of pigment dispersant P1 of 25% by mass.

[0366] 96 parts by mass of the polymer solution, 300 parts by mass of CI Pigment White 6 (product name "JR-405," titanium dioxide particles, manufactured by TAYCA Co., Ltd.) as a white pigment, and 270 parts by mass of water were mixed to obtain a mixed solution. A potassium hydroxide aqueous solution was added to the obtained mixed solution to adjust the pH (25°C) after neutralization to 8.7.

[0367] The neutralized mixed solution was then dispersed for 3 hours using a bead mill (bead diameter: 0.1 mmφ, zirconia beads) to obtain a white pigment dispersion (uncrosslinked dispersion) PD1 in which a white pigment was dispersed in the pigment dispersant P1.

[0368] Next, ultrafiltration was performed using an ultrafiltration apparatus (cross-flow ultrafilter (UF), manufactured by Sartorius) by flowing ion-exchanged water at a flow rate of 600 mL per minute into the obtained white pigment dispersion (uncrosslinked dispersion) PD1. The ultrafiltration was performed three times, with the liquid temperature maintained at 25°C, using one pass as one pass, to double the volume of the prepared liquid. Ion-exchanged water was added to the ultrafiltered liquid to obtain an ultrafiltered dispersion with a white pigment concentration of 45% by mass and a pigment dispersant P1 concentration of 3.6% by mass.

[0369] To 136 parts by mass of the ultrafiltrated dispersion were added 1.35 parts by mass of trimethylolpropane polyglycidyl ether (product name "Denacol EX-321", manufactured by Nagase ChemteX Corporation) as a crosslinking agent and 14.5 parts by mass of an aqueous boric acid solution (boric acid concentration: 4% by mass), and the mixture was reacted at 70°C for 6 hours, followed by cooling to 25°C. This crosslinked the pigment dispersant P1 in the dispersion to form the pigment dispersant P1a, which is a crosslinked polymer dispersant. This yielded a white pigment dispersion (crosslinked dispersion) in which the white pigment was dispersed in the pigment dispersant P1a.

[0370] Ion-exchanged water was added to the obtained cross-linked dispersion to a pigment concentration of 15% by mass. The cross-linked dispersion to which ion-exchanged water was added was passed through an ultrafiltration device (cross-flow ultrafilter (UF), manufactured by Sartorius) equipped with a polyethersulfone (PESU) membrane (pore size: 0.1 μm) at a flow rate of 600 mL per minute to perform ultrafiltration. At this time, the liquid temperature was adjusted to 25°C, and ultrafiltration was performed three times, with 1 volume ratio of the produced liquid being considered as 1 pass. Next, ion-exchanged water was added to a white pigment concentration of 45% by mass. Thus, a white pigment dispersion was obtained.

[0371] The acid value of the pigment dispersant P1a contained in the white pigment dispersion was 144 mgKOH / g, and the concentration of the pigment dispersant P1a was 3.6% by mass.

[0372] (Preparation of white ink W1)

[0373] The following components were mixed to prepare white ink W1.

[0374] - Composition of white ink W1 -

[0375] ·The above white pigment dispersion

[0376] ...12% by mass in terms of white pigment content

[0377] Propylene glycol (PG) (water-soluble organic solvent)

[0378] ...28% by mass

[0379] Propylene glycol monomethyl ether (PGmME) (water-soluble organic solvent)

[0380] ...2% by mass

[0381] BYK-347 (manufactured by BYK) [Silicone-based surfactant]

[0382] ……0.20 mass%

[0383] OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) [Acetylene glycol surfactant]

[0384] ……0.60 mass%

[0385] SOLSPERSE 43000 (manufactured by The Lubrizol Corporation) [Water-soluble polymer]

[0386] ...1% by mass

[0387] PVP-K15 (Polyvinylpyrrolidone K15)

[0388] ……0.12 mass%

[0389] Urea

[0390] ……0.50 mass%

[0391] SNOWTEX XS (manufactured by Nissan Chemical Corporation) [Colloidal silica dispersion]

[0392] ...the content of colloidal silica particles is 0.1% by mass

[0393] NEOCRYL A1091 (manufactured by Covestro Coating Resins) [Aqueous dispersion of styrene acrylic resin particles]

[0394] ...the content of styrene acrylic resin particles is 5.0% by mass

[0395] ·water

[0396] ...white ink as a whole makes up the remainder of 100% by mass

[0397] (Preparation of White Inks W2 to W6)

[0398] White inks W2 to W6 were prepared in the same manner as for white ink W1, except that the contents of BYK-347 and OLFINE E1010 in white ink W1 were changed to the contents shown below and the water content was appropriately adjusted.

[0399] -White ink W2-

[0400] BYK-347……0.10 mass%

[0401] ·OLFINE E1010……0.60 mass%

[0402] -White ink W3-

[0403] ·OLFINE E1010……0.60 mass%

[0404] Does not contain BYK-347.

[0405] -White ink W4-

[0406] BYK-347……0.30 mass%

[0407] ·OLFINE E1010……0.60 mass%

[0408] -White ink W5-

[0409] ·OLFINE E1010……0.10 mass%

[0410] Does not contain BYK-347.

[0411] -White ink W6-

[0412] BYK-347……0.70 mass%

[0413] ·OLFINE E1010……1.0 mass%

[0414] <Preparation of pretreatment solution>

[0415] The following components were mixed to prepare a pretreatment liquid. The surface tension of the pretreatment liquid was 35 mN / m.

[0416] - Composition of pretreatment solution -

[0417] Glutaric acid (coagulant)

[0418] ……6.1% by mass

[0419] Propylene glycol (PG) (water-soluble organic solvent)

[0420] ...20% by mass

[0421] OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) [Surfactant]

[0422] ……0.5% by mass

[0423] SUPER FLEX 500M (DKS Co. Ltd.) [Aqueous dispersion of urethane resin particles]

[0424] ……7.0% by mass

[0425] Triisopropanolamine (pH adjuster)

[0426] ...0.2% by mass

[0427] BYK024 (BYK)〔Defoaming Agent〕

[0428] ...0.01 mass%

[0429] Ultrapure water

[0430] ...the remainder of the pretreatment solution is 100% by mass.

[0431] <Preparation of image recording equipment>

[0432] As an image recording device for evaluation, a Figure 1 The image recording device shown.

[0433] As the pretreatment liquid applying apparatus P1, a gravure coater was used.

[0434] The drying method in the pre-treatment liquid drying area DP1 is warm air drying.

[0435] The first inkjet head IJ1 and the first drying area D1 are set to be inactive.

[0436] As the second inkjet head IJ2, an inkjet head for white ink is arranged.

[0437] Before ejecting ink, the inkjet head was wiped with a cleaning cloth (product name "Toraysee (registered trademark), manufactured by TORAY INDUSTRIES, INC.") soaked in inkjet cleaning liquid (product name "C-FJ-CC", manufactured by FUJIFILM Corporation) as a preliminary preparation.

[0438] The drying method in the second drying zone D2 is warm air drying.

[0439] An air cooling zone (not shown) is provided between the second drying zone D2 and the winding device R2.

[0440] As the inkjet head, a 1200 dpi (dot per inch, 1 inch is 2.54 cm) / 20-inch width piezoelectric line head (total number of nozzles: 2048) was used.

[0441] The driving frequency of the inkjet head was set to 30 kHz.

[0442] The white ink was discharged in two droplet sizes shown in Table 1. In Comparative Example 2, only one droplet size was used.

[0443] <Image Record>

[0444] Image recording was performed using the above-mentioned image recording device.

[0445] The image recording device is loaded with the above-mentioned pre-treatment liquid and white ink.

[0446] As the non-permeable substrate, an OPP film (product name "pylenct film-OT", manufactured by Toyobo Co., Ltd., thickness 25 μm) was used.

[0447] First, the impermeable substrate is unwound by the unwinding device R1 and conveyed under tension. The pretreatment liquid is applied to the conveyed impermeable substrate by the gravure coater serving as the pretreatment liquid applying device P1.

[0448] Next, the pre-treatment liquid is dried in the pre-treatment liquid drying region DP1.

[0449] Next, the first inkjet head IJ1 and the first drying area D1 are passed directly.

[0450] Next, the second inkjet head IJ2 applies white ink in a solid image onto the area of ​​the non-permeable substrate to which the pre-treatment liquid has been applied.

[0451] Next, the white ink is dried in the second drying area D2.

[0452] Through the above operation, a white image (solid image) derived from white ink was recorded on the non-permeable substrate having a length of 1000 m, thereby obtaining an image recorded material.

[0453] Next, the obtained image recorded material is air-cooled and then wound up by a winding device R2 including a winding core, thereby obtaining a roll of the image recorded material.

[0454] The amount of pretreatment liquid applied was set to 1.7 g / m 2 .

[0455] The drying conditions of the pretreatment liquid were set at 40° C. and 3 seconds.

[0456] The drying conditions for the white ink were set at 70° C. and 20 seconds.

[0457] (Contact angle of ink on substrate applied with pre-treatment liquid)

[0458] After applying the pretreatment liquid to the substrate and drying it, the substrate with the pretreatment liquid was cut to obtain a measurement sample. 2.0 μL of white ink was dropped onto the surface of the measurement sample with the pretreatment liquid, and the contact angle of the ink film was measured after 300 milliseconds.

[0459] The contact angle was measured at 20° C. using a contact angle meter (product name “DM-501”, manufactured by Kyowa Interface Science Co., Ltd.).

[0460] The obtained image records were used to evaluate streaks, drying properties, and sharpness using the following evaluation methods.

[0461] (stripe)

[0462] The resulting image recorded material roll was unwound. A portion of the 1000-meter-long image recorded material, corresponding to the width of one inkjet head, was visually inspected to determine the number of streaks occurring in the white image along the substrate's feed direction. Evaluation criteria were as follows.

[0463] AA: No streaks were observed.

[0464] A: There are 1 or more and less than 4 streaks.

[0465] B: There are 4 or more and less than 8 streaks.

[0466] C: The number of streaks is 8 or more and less than 15.

[0467] D: There are 15 or more streaks.

[0468] (Drying properties)

[0469] The resulting roll of image-recorded material was unwound and its drying properties were evaluated at a location approximately 100 m from the end of winding. Specifically, the presence of peeling noises caused by unwinding was confirmed. Furthermore, the presence of transferred material on the back of the impermeable substrate was visually verified. The evaluation criteria are as follows.

[0470] AA: No peeling sound due to unwinding was heard at a position approximately 100 m from the winding end position, and no transferred material was confirmed on the back surface of the impermeable substrate.

[0471] A: A peeling sound caused by unwinding was sometimes heard at a position approximately 100 m from the winding end position, but no transferred material was confirmed on the back surface of the non-permeable substrate.

[0472] B: Peeling noises due to unwinding were continuously heard at a position approximately 100 m from the winding end position, but no transferred material was observed on the back surface of the impermeable substrate.

[0473] C: A colorless and transparent transferred material was observed on the back surface of the non-permeable substrate at a position approximately 100 m from the winding end position.

[0474] D: A transferred white image was observed on the back surface of the non-permeable substrate at a position approximately 100 m from the winding end position.

[0475] (Sharpness)

[0476] The frame line of the white image in the image record (the boundary line between the white image and the part where the white image is not recorded) was visually observed from a position 10 cm away from the image record. It was confirmed whether the frame line was a smooth straight line (specifically, without undulations). In the case where the frame line was a smooth straight line, the evaluation was completed. In the case where the frame line was not a smooth straight line, the frame line was observed in the same way from a position 30 cm away from the image record. In the case where the frame line was a smooth straight line, the evaluation was completed. In the case where the frame line was not a smooth straight line, the frame line was observed in the same way from a position 50 cm away from the image record. Based on the observation results, the sharpness was evaluated. The evaluation criteria are as follows.

[0477] AA: When viewed from a distance of 10 cm, the frame lines appear as smooth straight lines.

[0478] A: When viewed from a distance of 30 cm, the frame line is a smooth straight line.

[0479] B: When viewed from a distance of 50 cm, the frame line is a smooth straight line.

[0480] C: Observing the frame line from a distance of 50 cm, undulation was confirmed in part of the frame line.

[0481] D: Observing the frame line from a distance of 50 cm, undulations are observed along the entire frame line.

[0482] Table 1 shows the evaluation results.

[0483] In Table 1, a1 represents the ratio of the number of ejection times of the first droplet to the total number of ejection times of the first and second droplets, a2 represents the ratio of the number of ejection times of the second droplet to the total number of ejection times of the first and second droplets, V1 represents the size of the first droplet, V2 represents the size of the second droplet, and θ represents the contact angle of the ink with respect to the surface of the substrate to which the pretreatment liquid has been applied.

[0484] In Table 1, the calculated value of “V2 / V1” is recorded in the column of formula (1), and the calculated value of “{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2”, the calculated value is recorded in the column of formula (3) as “[{V1 1 / 3 ×(1+cosθ)} 2 -{V21 / 3 ×(1+cosθ)} 2 ]×a1". In Comparative Example 2, since only one type of droplet was used, V2 was calculated as the same value as V1.

[0485] [Table 1]

[0486]

[0487] As shown in Table 1, Examples 1 to 14 include the following steps: using an inkjet recording method, an ink containing water and a colorant is ejected as at least two types of droplets having different droplet sizes onto a substrate in a single-pass manner, two of the at least two types of droplets are set as a first droplet and a second droplet, and V1, V2, a1, a2, and θ, which are parameters related to the first droplet and the second droplet, satisfy equations (1) and (2), so that the drying property is excellent and streaks in the recorded image can be suppressed.

[0488] On the other hand, in Comparative Example 1, it was found that the drying property was poor because the ink was discharged with only one droplet size.

[0489] In Comparative Example 2, it was found that since "V2 / V1" was less than 0.45, the drying property was poor.

[0490] In Comparative Example 3, due to “{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 Since ×a2" is less than 3.5, streaks are observed in the image.

[0491] In Comparative Example 4, it can be seen that due to "{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2" exceeds 7.0, so the drying property is poor.

[0492] In Example 4, since "V2 / V1" is 0.5 to 0.8, it can be seen that the drying property is excellent compared with Example 5.

[0493] In Example 6, it can be seen that due to "{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 Since ×a2" is 4.5 or more, streaks in the recorded image are further suppressed.

[0494] In Examples 1 to 4, 7, 11 to 13, it can be seen that due to “{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 Since ×a2" is 6.2 or less, the drying property is more excellent.

[0495] It can be seen that due to the "[{V1 1 / 3 ×(1+cosθ)} 2 -{V2 1 / 3 ×(1+cosθ)} 2 ]×a1" is 4.8 or less, so the image sharpness is excellent.

[0496] Next, in addition to the above-mentioned pre-treatment liquid and white ink W1 , image recording was performed using cyan ink.

[0497] <Preparation of Cyan Ink C1>

[0498] The following components were mixed to prepare cyan ink C1.

[0499] -Composition of Cyan Ink C1-

[0500] Cyan pigment dispersion (product name "APD4000 Cyan", manufactured by Fujifilm Imaging Colorants Ltd.)

[0501] ...the content of cyan pigment is 3.4% by mass

[0502] Propylene glycol (PG) (water-soluble organic solvent)

[0503] ...28% by mass

[0504] Propylene glycol monomethyl ether (PGmME) (water-soluble organic solvent)

[0505] ...2% by mass

[0506] BYK-347 (manufactured by BYK) [Silicone-based surfactant]

[0507] ...0.2% by mass

[0508] OLFINE E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) [Acetylene glycol surfactant]

[0509] ……0.60 mass%

[0510] SOLSPERSE 43000 (manufactured by The Lubrizol Corporation) [Water-soluble polymer]

[0511] ...1% by mass

[0512] PVP-K15 (Polyvinylpyrrolidone K15)

[0513] ……0.12 mass%

[0514] Urea

[0515] ……0.50 mass%

[0516] SNOWTEX XS (manufactured by Nissan Chemical Corporation) [Colloidal silica dispersion]

[0517] ...the content of colloidal silica particles is 0.1% by mass

[0518] NEOCRYL A1091 (manufactured by Covestro Coating Resins) [Aqueous dispersion of styrene acrylic resin particles]

[0519] ...the content of styrene acrylic resin particles is 7.0% by mass

[0520] ·water

[0521] ...the remainder of the cyan ink is 100% by mass.

[0522] <Preparation of image recording equipment>

[0523] As an image recording device for evaluation, a Figure 1 The image recording device shown.

[0524] As the pretreatment liquid applying apparatus P1, a gravure coater was used.

[0525] The drying method in the pre-treatment liquid drying area DP1 is warm air drying.

[0526] As the first inkjet head IJ1, an inkjet head for cyan ink is arranged.

[0527] As the second inkjet head IJ2, an inkjet head for white ink is arranged.

[0528] The drying method in the first drying zone D1 and the second drying zone D2 is warm air drying.

[0529] An air cooling zone (not shown) is provided between the second drying zone D2 and the winding device R2.

[0530] As the inkjet head, a 1200 dpi (dot per inch, 1 inch is 2.54 cm) / 20-inch width piezoelectric line head (total number of nozzles: 2048) was used.

[0531] The driving frequency of the inkjet head was set to 30 kHz.

[0532] The cyan ink was discharged at the droplet size V2 shown in Example 1 (2.00 pL).

[0533] The white ink was discharged in the two droplet sizes shown in Example 1.

[0534] <Image Record>

[0535] Image recording was performed using the above-mentioned image recording device.

[0536] The image recording apparatus is loaded with the aforementioned pre-treatment liquid, cyan ink C1, and white ink W1.

[0537] As the non-permeable substrate, an OPP film (product name "pylenct film-OT", manufactured by Toyobo Co., Ltd., thickness 25 μm) was used.

[0538] First, the impermeable substrate is unwound by the unwinding device R1 and conveyed under tension. The pretreatment liquid is applied to the conveyed impermeable substrate by the gravure coater serving as the pretreatment liquid applying device P1.

[0539] Next, the pre-treatment liquid is dried in the pre-treatment liquid drying region DP1.

[0540] Next, the cyan ink C1 is applied in a solid image form by the first inkjet head IJ1 onto the area of ​​the non-permeable substrate to which the pre-treatment liquid has been applied.

[0541] Next, the cyan ink C1 is dried in the first drying area D1 .

[0542] Next, the second inkjet head IJ2 applies white ink W1 in a solid image onto the area of ​​the non-permeable substrate to which the cyan ink C1 has been applied.

[0543] Next, the white ink W1 is dried in the second drying region D2.

[0544] By the above operation, a cyan ink image (solid image) derived from the cyan ink C1 and a white image (solid image) derived from the white ink W1 were recorded on the non-permeable substrate having a length of 1000 m, thereby obtaining an image recorded material.

[0545] Next, the obtained image recorded material is air-cooled and then wound up by a winding device R2 including a winding core, thereby obtaining a roll of the image recorded material.

[0546] The amount of pretreatment liquid applied was set to 1.7 g / m 2 .

[0547] The drying conditions of the pretreatment liquid were set at 40° C. and 3 seconds.

[0548] The drying conditions for the cyan ink C1 and the white ink W1 were set to 70° C. and 20 seconds.

[0549] (Contact angle of ink on substrate applied with cyan ink C1)

[0550] After applying cyan ink C1 to a substrate and drying it, the substrate coated with cyan ink C1 was cut to obtain a measurement sample. 2.0 μL of white ink was dropped onto the surface of the measurement sample coated with cyan ink C1, and the contact angle of the ink film was measured after 300 milliseconds.

[0551] The contact angle was measured at 20° C. using a contact angle meter (product name “DM-501”, manufactured by Kyowa Interface Science Co., Ltd.).

[0552] The contact angle is 40°.

[0553] The obtained image recorded material was used to evaluate streaks, drying properties, and sharpness in the same manner as the above-mentioned evaluation method. As a result, all the evaluation results were A.

[0554] In addition, the disclosure of Japanese Patent Application No. 2023-019432 filed on February 10, 2023 is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. An image recording method comprising the steps of: using an inkjet recording method to discharge at least two types of droplets containing water and a colorant as droplets of different sizes onto a substrate in a single pass; In the step of setting two of the at least two types of droplets as a first droplet and a second droplet, The size of the first droplet is V1 in pL. The size of the second droplet is V2 in pL. The ratio of the number of discharges of the first droplet to the total number of discharges of the first droplet and the second droplet is a1, The ratio of the number of discharges of the second droplet to the total number of discharges of the first droplet and the second droplet is a2, When the contact angle of the ink with respect to the contact surface with which the ink comes into contact by the ejection of the ink is denoted as θ°, The V1, the V2, the a1, the a2, and the θ satisfy the following equations (1) and (2): 0.45≤V2 / V1≤0.9(1); and 3.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤7.0(2), in, The contact angle is a contact angle measured at a point in time when the ink is applied to the contact surface and 300 milliseconds have passed since the ink was applied to the contact surface.

2. The image recording method according to claim 1, wherein: The V1 and the V2 satisfy the following formula (1A): 0.5≤V2 / V1≤0.8(1A).

3. The image recording method according to claim 1 or 2, wherein: V1, V2, a1, a2, and θ satisfy the following formula (2A): 4.5≤{V1 1 / 3 ×(1+cosθ)} 2 ×a1+{V2 1 / 3 ×(1+cosθ)} 2 ×a2≤6.2(2A)。 4. The image recording method according to claim 1 or 2, wherein: The V1, the V2, the a1, the a2, and the θ satisfy the following formula (3): [{V1 1 / 3 ×(1+cosθ)} 2 -{V2 1 / 3 ×(1+cosθ)} 2 ]×a1≤4.8 (3)。 5. The image recording method according to claim 1 or 2, wherein: The substrate is a non-permeable substrate.

6. The image recording method according to claim 1 or 2, wherein: The colorant is a white colorant.

7. The image recording method according to claim 6, wherein: The white colorant includes at least one selected from the group consisting of titanium dioxide and hollow particles.

8. The image recording method according to claim 1 or 2, wherein: The method further comprises the steps of applying a pretreatment liquid containing a coagulant to the substrate, In the step of discharging the ink, the ink is discharged onto the substrate to which the pre-treatment liquid has been applied.

Images