Image recording method and image recording apparatus

Abstract

An image recording method includes: a recording step in which a white image is recorded by applying a white ink containing water and a white pigment to one surface of an impermeable substrate by an inkjet method; and a winding step in which the impermeable substrate on which the white image is recorded is wound in a state in which tension is applied, and a [delta] E / P ratio, which is the value obtained by dividing [delta] E by P, is 0.06-0.60, where [delta] E is the surface energy difference in mJ / m2 units between the other surface of the impermeable substrate and the surface of the white image, and P is the tension in N / m units.

Description

Technical Field

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

[0002] Conventionally, various studies have been conducted on image recording methods.

[0003] For example, Patent Document 1 discloses an aqueous inkjet ink composition containing resin particles, a nonionic surfactant, a resin-soluble solvent, and water as an aqueous inkjet ink composition that can obtain a recorded object with excellent abrasion resistance and sticking resistance while ensuring ejection stability during recording. The acid value of the resin particles in the aqueous inkjet ink composition and, when the aqueous inkjet ink composition contains a dispersant resin, the total acid value of the resin particles and the acid value of the dispersant resin are 200 (mgKOH / 100g ink) or less.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-165314 Summary of the invention

[0005] Technical issues to be solved by the invention

[0006] In image recording in which a white image is recorded by applying a white ink to an impermeable substrate by an inkjet method and then the impermeable substrate on which the white image is recorded is wound up, it is sometimes required to suppress blocking of the white image.

[0007] However, the present inventors have found through studies that when an attempt is made to suppress blocking of a white image during the above-mentioned image recording, curling of the non-permeable substrate is likely to occur.

[0008] Therefore, in the above-mentioned image recording, it is sometimes required to suppress the blocking of the white image and the curling of the non-permeable substrate.

[0009] Here, the blocking of the white image means that after the impermeable substrate on which the white image is recorded is rolled up, the white image sticks to the image back side of the impermeable substrate in contact with the surface of the white image.

[0010] The winding deviation of the impermeable substrate refers to a phenomenon in which, as the impermeable substrate having a white image recorded thereon is wound up, the position of the wound impermeable substrate gradually shifts in the axial direction of the winding.

[0011] The present invention is completed in view of this situation, and its purpose is to provide an image recording method and an image recording device, which can record a white image on a non-permeable substrate and suppress the adhesion of the white image and the winding deviation of the non-permeable substrate when the non-permeable substrate with the white image recorded is rolled up.

[0012] Means for solving technical problems

[0013] The present invention includes the following aspects.

[0014] <1> An image recording method comprising: a recording step of applying a white ink containing water and a white pigment to one surface of an impermeable substrate by an inkjet method to record a white image; and a winding step of winding the impermeable substrate on which the white image is recorded under tension.

[0015] mJ / m 2 When the surface energy difference in a unit is ΔE and the tension in a unit of N / m is P, the ΔE / P ratio, which is a value obtained by dividing ΔE by P, is 0.06 to 0.60.

[0016] <2> The image recording method according to <1>, wherein:

[0017] The recording step further includes applying a coloring ink containing water and a coloring pigment to one surface of the non-permeable substrate by an inkjet method to record a coloring image.

[0018] <3> The image recording method according to <2>, wherein:

[0019] The colored image is recorded before the white image and is disposed between one side of the non-permeable substrate and the white image.

[0020] <4> The image recording method according to any one of <1> to <3>, wherein:

[0021] ΔE is 5.0~25.0.

[0022] <5> The image recording method according to any one of <1> to <4>, wherein:

[0023] P is 30~150.

[0024] <6> The image recording method according to any one of <1> to <5>, wherein:

[0025] The ΔE / P ratio is 0.10 to 0.50.

[0026] <7> The image recording method according to any one of <1> to <6>, further comprising, before the recording step, applying a pretreatment liquid containing water and a coagulant to one surface of the non-permeable substrate,

[0027] In the recording step, white ink is applied to the area on one surface to which the pretreatment liquid is applied, thereby recording a white image.

[0028] <8> An image recording device used in the image recording method according to any one of <1> to <7>,

[0029] The image recording device comprises:

[0030] a recording unit including an inkjet head for applying the white ink to one surface of the non-permeable substrate and performing a recording step of recording the white image on the one surface of the non-permeable substrate; and

[0031] The winding section includes a winding device for winding the impermeable substrate having the white image recorded thereon under tension, and performs the winding step.

[0032] The above-mentioned ΔE / P ratio is 0.06 to 0.60.

[0033] Effects of the Invention

[0034] According to one embodiment of the present invention, an image recording method and an image recording device are provided, which can record a white image on an impermeable substrate and suppress the sticking of the white image and the winding deviation of the impermeable substrate when the impermeable substrate with the white image recorded thereon is rolled up. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram conceptually showing an example of an image recording device used to implement the image recording method of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] 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 represents the total amount of the plurality of substances present in the composition unless otherwise specified.

[0039] In the present invention, a combination of two or more preferred aspects is a more preferred aspect.

[0040] In the present invention, 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.

[0041] In the present invention, the “image” refers to the ink film itself when no pre-treatment liquid is used, and refers to a laminated film of the pre-treatment liquid film and the ink film when a pre-treatment liquid is used.

[0042] In the present invention, "image recording" means the formation of an image.

[0043] The concept of "image" in the present invention also includes a solid image.

[0044] In the present invention, the expression "applying ink onto a substrate" includes a method of directly applying ink onto the surface of a substrate and a method of directly applying ink onto the upper side of the substrate, for example, onto the surface of layer A when layer A is formed.

[0045] In the present invention, unless otherwise specified, “upstream side” refers to the upstream side in the conveying direction of the impermeable substrate, and unless otherwise specified, “downstream side” refers to the downstream side in the conveying direction of the impermeable substrate.

[0046] [Image recording method]

[0047] The image recording method of the present invention (hereinafter, also referred to as "recording method") comprises: a recording step of applying white ink containing water and white pigment to one side (hereinafter, also referred to as "front side") of an impermeable substrate by inkjet method to record a white image; and a winding step of winding the impermeable substrate with the white image recorded thereon under a tension applied thereto, and aligning the other side (hereinafter, also referred to as "back side") of the impermeable substrate with the surface of the white image. 2 When the surface energy difference in a unit is ΔE and the tension in a unit of N / m is P, the ΔE / P ratio, which is a value obtained by dividing ΔE by P, is 0.06 to 0.60.

[0048] According to the recording method of the present invention, a white image can be recorded on an impermeable substrate, and blocking of the white image and winding deviation of the impermeable substrate can be suppressed when the impermeable substrate having the white image recorded thereon is rolled up.

[0049] The reason why this effect can be obtained is presumably as follows.

[0050] The reason why the blocking of the white image can be suppressed is presumed to be as follows.

[0051] mJ / m2 on the back of the non-permeable substrate and on the surface of the white image 2The larger the value of the unit surface energy difference, ΔE (hereinafter also referred to as "surface energy difference ΔE"), the more advantageous it is for suppressing the blocking of the white image. The reason for this is that the larger the surface energy difference ΔE, the lower the affinity between the back side of the non-permeable substrate and the white image that contacts the back side after winding.

[0052] On the other hand, when the impermeable substrate having the white image recorded thereon is rolled up, the smaller the value of the tension in N / m (i.e., P (hereinafter also referred to as "tension P") applied to the impermeable substrate is, the more advantageous it is for suppressing the sticking of the white image. The reason for this is that the smaller the tension P is, the less tightly the impermeable substrate is rolled up, and as a result, in the rolled-up impermeable substrate, the mutual pressing force between the back side of the impermeable substrate and the white image contacting the back side becomes weaker.

[0053] Therefore, the larger the ΔE / P ratio, which is a value obtained by dividing ΔE by P, the more advantageous it is for suppressing the sticking of the white image.

[0054] Specifically, in the recording method of the present invention, when the ΔE / P ratio is 0.06 or more, blocking of the white image can be suppressed.

[0055] The reason why the curling of the impermeable substrate can be suppressed is presumed to be as follows.

[0056] The smaller the value of the surface energy difference ΔE, the more favorable it is for the winding deviation of the impermeable substrate. The reason is that the smaller the surface energy difference ΔE, the higher the affinity between the back side of the impermeable substrate and the white image that contacts the back side after winding, and the deviation between the two is less likely to occur.

[0057] On the other hand, the greater the value of the tension P, the more favorable it is for the impermeable substrate to be rolled up. The reason for this is that the greater the tension P, the tighter the impermeable substrate is rolled up, and as a result, after winding up, the mutual pressing force between the back side of the impermeable substrate and the white image contacting the back side becomes stronger.

[0058] Therefore, the larger the ΔE / P ratio, which is the value obtained by dividing ΔE by P, the more advantageous it is for suppressing the deviation of the impermeable substrate.

[0059] Specifically, in the recording method of the present invention, when the ΔE / P ratio is 0.60 or less, the curling of the non-permeable substrate can be suppressed.

[0060] <ΔE / P ratio>

[0061] As described above, the ΔE / P ratio in the present invention is 0.06 to 0.60.

[0062] The ΔE / P ratio is preferably 0.10 to 0.50.

[0063] When the ΔE / P ratio is 0.10 or more, blocking of the white image can be further suppressed.

[0064] When the ΔE / P ratio is 0.50 or less, the curling of the impermeable substrate can be further suppressed.

[0065] <Surface energy difference ΔE>

[0066] The surface energy difference ΔE is the surface energy difference between the back side of the non-permeable substrate and the surface of the white image.

[0067] Here, the surface energy difference ΔE is calculated according to

[0068] The dispersion component of the surface energy of the back side of the non-permeable substrate γ S d (1)

[0069] The hydrogen bonding component of the surface energy of the back side of the non-permeable substrate is γ S h (1)

[0070] Dispersive component of the surface energy of the white image γ S d (2)

[0071] The hydrogen bonding component of the surface energy of the white image γ S h (2)

[0072] It can be obtained by the following formula.

[0073] ΔE=((γ S d (2)-γ S d (1)) 2 +(γ S h (2)-γ S h (1)) 2 ) 1 / 2

[0074] The surface energy difference ΔE is not particularly limited as long as the ΔE / P ratio is a value within the above range.

[0075] The surface energy difference ΔE is, for example, 35.0 or less, preferably 1.0 to 30.0, more preferably 5.0 to 25.0, and further preferably 7.0 to 24.0.

[0076] <Measurement method of surface energy (hydrogen bonding component and dispersion component)>

[0077] In the present invention, the surface energy (hydrogen bonding component and dispersion component) of the solid surface (ie, each of the back surface of the non-permeable substrate and the surface of the white image) refers to a value calculated by the Owens-Wendt method.

[0078] The surface energy of the white image is measured by recording the white image on an impermeable substrate using the same white ink as the white ink in the recording process and under the same conditions as in the recording process, thereby using an impermeable substrate on which the white image is recorded (hereinafter also referred to as an "image sample").

[0079] The contact angle of water and the contact angle of diiodomethane described below were measured within 30 minutes after the image sample was prepared (that is, after the ink was dried).

[0080] The surface energy of the back surface of the impermeable substrate can be measured using the back surface of the impermeable substrate itself used in the recording step.

[0081] The contact angles of water and methylene iodide with a solid surface (ie, the surface of the white image in the image sample or the back side of the non-permeable substrate) were measured using a contact angle meter.

[0082] As the contact angle meter, for example, product name “DM-501” manufactured by Kyowa Interface Science Co., Ltd. can be used.

[0083] The surface energy of the solid surface was calculated by the Owens-Wendt method using the measured values ​​of the contact angles of water and diiodomethane with the solid surface and the dispersion components and hydrogen bonding components of water and diiodomethane.

[0084] The Owens-Wendt method is described in DK Owens, and, RC Wendt, Journal of applied polymer science Vol. 13, PP. 1741-1747, (1969).

[0085] The specific calculation method is described below.

[0086] When a liquid is dropped onto a solid surface, the following equations hold true for various parameters at the interface between the solid surface and the liquid.

[0087] The following formula 1 is known as Young's equation.

[0088] The following formula 2 is known as the Dupre equation.

[0089] The following formula 3, formula 4, and formula 5 are known as equations based on the Owens-Wendt method.

[0090] γ S =γ L cosθ+γ SL …(1)

[0091] W=γ S +γ L -γ SL …(2)

[0092] γ S =γ S d +γ S h …(3)

[0093] γ L =γ L d +γ L h …(4)

[0094] W = 2(γ S d γ L d ) 1 / 2 +2(γ S h γ L h ) 1 / 2 …(5)

[0095] In Formula 1 to Formula 5, the details of each symbol are as follows.

[0096] θ…Contact angle between liquid and solid surface

[0097] γ S …the surface energy of a solid surface

[0098] γ L …the surface energy of a liquid

[0099] γ SL …interfacial energy between solid surface and liquid

[0100] W…bonding work

[0101] γ S d …the dispersive component of the surface energy of a solid surface

[0102] γ S h …the hydrogen bonding component of the surface energy of a solid surface

[0103] γ L d …the dispersive component of the surface energy of a liquid

[0104] γ L h …the hydrogen bonding component of the surface energy of a liquid

[0105] According to the above formulas 1 to 5, the following formula 6 can be obtained.

[0106] (γ S d γ L d ) 1 / 2 +(γ S h γ L h ) 1 / 2 =γ L (1+cosθ) / 2…(6)

[0107] As the liquid in Formula 6, water and diiodomethane are used, and they are set as Formula 6A and Formula 6B.

[0108] (γ S d γ L1 d ) 1 / 2 +(γ S h γ L1 h ) 1 / 2 =γ L1 (1+cosθ1) / 2…(6A)

[0109] (γ S d γ L2 d ) 1 / 2 +(γ S h γ L2 h ) 1 / 2 =γ L2 (1+cosθ2) / 2…(6B)

[0110] In Formula 6A and Formula 6B, the details of each symbol are as follows.

[0111] θ1…Contact angle between water and solid surface

[0112] θ2…Contact angle of diiodomethane on solid surface

[0113] γ L1 ...Surface energy of water (72.8 mN / m)

[0114] γ L1 d ...dispersive component of water's surface energy (21.8 mN / m)

[0115] γ L1 h ...the hydrogen bonding component of the surface energy of water (51.0 mN / m)

[0116] γ L2 ...Surface energy of diiodomethane (50.8 mN / m)

[0117] γ L2 d ...dispersive component of the surface energy of diiodomethane (50.8 mN / m)

[0118] γ L2 h ...Hydrogen bonding component of the surface energy of diiodomethane (0mN / m)

[0119] In addition, the values ​​in parentheses are values ​​described in literature.

[0120] By substituting θ1, θ2, γ into equations 6A and 6B, L1 , γ L1 d , γ L1 h , γ L2 , γ L2 d and γ L2 h To calculate γ S d and γ S h .

[0121] As θ1 and θ2, the measured values ​​obtained by the above-mentioned measuring method were used.

[0122] By substituting the calculated γ into Equation 3 S d and γ S h , the surface energy γ of the solid surface can be calculated S .

[0123] The surface energy of the back surface of the impermeable substrate and the surface energy of the surface of the white image are not particularly limited as long as they satisfy the above range of the ΔE / P ratio.

[0124] The surface energy of the back side of the non-permeable substrate γ S For example, 30.0 mJ / m 2 ~50.0mJ / m 2 .

[0125] The dispersion component of the surface energy of the back side of the non-permeable substrate γ S d For example, 30.0 mJ / m 2 ~50.0mJ / m 2 .

[0126] The hydrogen bonding component of the surface energy of the back side of the non-permeable substrate is γS h For example, 0mJ / m 2 ~3.0mJ / m 2 .

[0127] Surface energy of white image γ S For example, 35.0 mJ / m 2 ~80.0mJ / m 2 .

[0128] Dispersive component of the surface energy of the white image γ S d For example, 30.0 mJ / m 2 ~50.0mJ / m 2 .

[0129] The hydrogen bonding component of the surface energy of the white image γ S h For example, 5.0 mJ / m 2 ~30.0mJ / m 2 .

[0130] <Tension P>

[0131] In the present invention, tension P (i.e., tension expressed in N / m when winding up an impermeable substrate) refers to the tension of the impermeable substrate just before the winding device (specifically, the area within 1 m from the winding device) for winding up the impermeable substrate having a white image recorded thereon (hereinafter also referred to as "tension P at the winding portion").

[0132] The tension P (unit: N / m) in the present invention refers to a value measured by a tensiometer.

[0133] The tension P is not particularly limited as long as the ΔE / P ratio is a value within the above range.

[0134] The tension P is, for example, 20 to 160, preferably 30 to 150, more preferably 35 to 100, and further preferably 40 to 80.

[0135] In the recording method of the present invention, tension may be applied to a region of the impermeable substrate more than 1 m upstream from the winding portion (for example, a region to which ink is applied).

[0136] In this case, the tension P may be the same as or different from the tension in the upstream region.

[0137] <Recording process>

[0138] The recording method of the present invention includes a recording step of applying a white ink containing water and a white pigment to the front surface of an impermeable substrate by an inkjet method to record a white image.

[0139] (Impermeable substrate)

[0140] In the present invention, the impermeability of the impermeable substrate refers to the property that the water absorption rate measured in accordance with ASTM D570-98 (2018) for 24 hours is 2.5% or less. Here, the "%" as the unit of water absorption rate is a mass basis. The above water absorption rate is preferably 1.0% or less, and more preferably 0.5% or less.

[0141] Examples of the material of 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.).

[0142] The material of the impermeable substrate is preferably a resin. That is, the impermeable substrate is preferably a resin substrate.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] At least one of the front side and the back side of the impermeable substrate may be subjected to a surface treatment.

[0149] As surface treatment, corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (such as UV treatment) and flame treatment can be cited, but it is not limited to these. Corona treatment can be carried out using a corona master (product name "PS-10S", manufactured by Shinko Electric & Instrumentation Co., Ltd.).

[0150] The conditions for the surface treatment may be appropriately selected depending on the type of the impermeable substrate and the like.

[0151] Furthermore, the surface energy of the back surface of the impermeable substrate can be adjusted by the presence or absence of surface treatment on the back surface of the impermeable substrate and the conditions for the surface treatment, thereby adjusting ΔE and the ΔE / P ratio.

[0152] The impermeable substrate may be a transparent impermeable substrate.

[0153] Here, having 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).

[0154] When the impermeable substrate is a transparent impermeable substrate, the image can be easily visually recognized from the image rear side of the impermeable substrate through the impermeable substrate.

[0155] For example, in the case where the impermeable substrate is a transparent impermeable substrate, when recording is performed on the impermeable substrate in a manner in which a pattern image such as characters or graphics, i.e., a colored image, and a white image (e.g., a solid image) as a background image are arranged in sequence when viewed from the impermeable substrate side, it is easy to visually recognize the colored image (e.g., a pattern image such as characters or graphics) with the white image (e.g., a solid image) as the background from the image back side of the impermeable substrate through the impermeable substrate.

[0156] In the present invention, the "coloring" in the coloring ink and the coloring pigment refers to a color (for example, cyan, magenta, yellow, etc.) or black (hereinafter also referred to as Black).

[0157] 〔White ink〕

[0158] In the recording process, white ink is applied to the front surface of the non-permeable substrate by an inkjet method to record a white image.

[0159] White ink contains water and white pigment.

[0160] Next, the white ink will be described.

[0161] -water-

[0162] White ink contains water.

[0163] The content of water 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, based on the total amount of the white ink.

[0164] The upper limit of the water content relative to the total amount of the white ink can be appropriately determined according to the contents of other components, and is, for example, 99% by mass, preferably 95% by mass, and more preferably 90% by mass.

[0165] -White pigment-

[0166] White ink contains white pigment.

[0167] Examples of the white pigment include inorganic pigments such as titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, zinc oxide, zinc sulfide, mica, talc, and pearl.

[0168] The white pigment is preferably titanium dioxide, barium sulfate, calcium carbonate or zinc oxide, more preferably titanium dioxide.

[0169] From the viewpoint of concealability, the average primary particle size of the white pigment is preferably 150 nm or more, more preferably 200 nm or more, and from the viewpoint 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.

[0170] Here, the concealing property refers to the property of covering the base on which the white image is formed (for example, the front surface of the non-permeable substrate or a colored image recorded on the front surface earlier than the white image) with the white image.

[0171] 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 any 50 white pigments present in the visual field observed by TEM to measure 50 primary particle sizes and averaging them. As a transmission electron microscope, a transmission electron microscope 1200EX manufactured by JEOL Ltd. can be used.

[0172] From the viewpoint of image density and ejection properties, when the ink contains a white pigment, the content of the white pigment 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.

[0173] -Resin-

[0174] The white ink may contain at least one type of resin.

[0175] The resin in the white ink contributes to the film-forming property of the white ink (ie, the formability of the white ink film).

[0176] The weight average molecular weight (Mw) of the resin is preferably 1,000 to 300,000, more preferably 2,000 to 200,000, and further preferably 5,000 to 100,000.

[0177] In the present invention, unless otherwise specified, the weight average molecular weight (Mw) refers to a value measured by gel permeation chromatography (GPC).

[0178] In the measurement by gel permeation chromatography (GPC), HLC (registered trademark)-8020GPC (TOSOH CORPORATION) was used as a measuring apparatus, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mmID×15 cm, TOSOH CORPORATION) columns were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, as measurement conditions, the sample concentration was set to 0.45 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., and the RI detector was used for the measurement.

[0179] The calibration curve was prepared using eight samples of "TSK standard, polystyrene" produced by TOSOH Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0180] As the resin, there can be mentioned a pigment dispersion resin which is a pigment dispersant.

[0181] Examples of the resin include resin particles.

[0182] The white ink may contain at least one pigment dispersion resin.

[0183] The pigment dispersion resin is a resin having a function of dispersing a pigment.

[0184] The pigment dispersing resin may be a random copolymer or a block copolymer.

[0185] The pigment dispersion resin may have a cross-linked structure.

[0186] The ink can be prepared using a pigment dispersion containing a pigment and a pigment dispersing resin.

[0187] As the pigment dispersion 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.

[0188] When the white ink contains a pigment dispersion resin, the ratio of the content of the pigment in the ink to the content of the pigment dispersion resin 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.

[0189] When the white 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, based on the total amount of the ink.

[0190] The white ink may contain at least one type of resin particles.

[0191] The resin constituting the resin particles is preferably a water-insoluble resin. The "water-insoluble" in the water-insoluble resin refers to a property that the amount of the resin that dissolves in 100 g of distilled water at 25°C is less than 2 g.

[0192] 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.

[0193] In the present invention, the volume average particle size refers to a value measured using a laser diffraction / scattering particle size distribution analyzer.

[0194] As a measuring apparatus, a particle size distribution measuring apparatus "Microtrac MT-3300II" (made by Nikkiso Co., Ltd.) is mentioned, for example.

[0195] 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.

[0196] 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 (such as acrylic acid esters), methacrylic acid and methacrylic acid derivatives (such as methacrylic acid esters).

[0197] 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.

[0198] Here, the glass transition temperature (Tg) of the resin particles is applied to the 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.

[0199] Regarding the resin particles, for example, paragraphs 0038 to 0114 of International Publication No. 2021 / 192720, paragraphs 0109 to 0120 of Japanese Patent Application Laid-Open No. 2015-25076, and the like can be referred to.

[0200] When the white ink contains resin particles, the content of the resin particles in the white ink is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, based on the total amount of the white ink.

[0201] -Water-soluble organic solvents-

[0202] The white ink preferably contains at least one water-soluble organic solvent.

[0203] This ensures the stability of ejection from the inkjet head.

[0204] The water-soluble organic solvent contained in the white ink may be one kind or two or more kinds.

[0205] In the present invention, the "water-soluble" in the "water-soluble organic solvent" refers to the property of dissolving 1 g or more in 100 g of water at 25°C.

[0206] The type of water-soluble organic solvent that can be contained in the white ink is not limited, and examples thereof include:

[0207] Monoalcohols having 1 to 4 carbon atoms;

[0208] 1,2-ethanediol (alias: ethylene glycol), 1,3-propylene glycol (alias: propylene glycol), 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 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;

[0209] Triols such as propylene glycol, 1,2,6-hexanetriol, and trimethylolpropane;

[0210] Alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether;

[0211] Polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol, etc.;

[0212] Polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether, and the like; and

[0213] 2-pyrrolidone, N-methyl-2-pyrrolidone;

[0214] wait.

[0215] From the viewpoint of discharge stability, the water-soluble organic solvent in the white ink preferably contains at least one selected from the group consisting of glycols and alkylene glycol monoalkyl ethers.

[0216] 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, based on the total amount of the white ink.

[0217] -Surfactant-

[0218] The white ink may contain at least one surfactant.

[0219] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants.

[0220] As a preferable surfactant, an acetylene glycol-based surfactant which is a kind of nonionic surfactant can be mentioned.

[0221] As the acetylene glycol-based surfactant, for example, the acetylene glycol-based surfactants described in paragraphs 0070 to 0080 of International Publication No. 2017 / 149917 can be used.

[0222] Examples of acetylene glycol surfactants include:

[0223] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 2,4,7,9-tetramethyl-5-decyne-4,7-diol,

[0224] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 3,6-dimethyl-4-octyne-3,6-diol,

[0225] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 2,5,8,11-tetramethyl-6-dodecene-5,8-diol,

[0226] Polyalkylene oxide adduct (preferably polyethylene oxide adduct) of 2,5-dimethyl-3-hexyne-2,5-diol

[0227] wait.

[0228] Commercially available products of acetylene glycol-based surfactants include: Surfynol series (e.g., Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485), OLFINE series (e.g., OLFINE E1010, OLFINE E1020), Dynol series (e.g., Dynol 604), etc. manufactured by Air Products Ltd. or Nissin Chemical Co., Ltd.; ACETYLENOL manufactured by Kawaken Fine Chemicals Co., Ltd., etc.

[0229] Commercial products of acetylene glycol-based surfactants are also provided by The Dow Chemical Company, General Aniline & Film Corp., and the like.

[0230] As surfactants, compounds listed as surfactants in JP-A-59-157636, pp. 37-38, and Research Disclosure No. 308119 (1989) can also be cited. Fluorine (fluoroalkyl) surfactants and silicone surfactants described in JP-A-2003-322926, JP-A-2004-325707, and JP-A-2004-309806 can also be cited.

[0231] When the white ink contains a surfactant, the content of the surfactant in the white ink can be appropriately adjusted in consideration of the surface energy of a white image to be recorded.

[0232] The content of the surfactant in the white ink is preferably 0.01% by mass to 5% by mass, more preferably 0.05% by mass to 3% by mass, and even more preferably 0.1% by mass to 2% by mass, based on the total amount of the white ink.

[0233] -Other ingredients-

[0234] The white ink may contain other components in addition to the above components.

[0235] As other components, for example, there can be mentioned known additives such as silicic acid compounds (for example, silicic acid compounds described in paragraphs 0058 to 0075 of Japanese Patent No. 5430316), urea, urea derivatives, wax, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, mildewproofing agents, pH adjusters, defoaming agents, viscosity adjusters, dispersion stabilizers, and chelating agents.

[0236] -Physical properties-

[0237] From the viewpoint of improving discharge stability, the pH (25° C.) of the white ink is preferably 7 to 10, and more preferably 7.5 to 9.5. The pH of the ink can be measured by the same method as the pH of the pretreatment liquid.

[0238] The viscosity (25° C.) of the white ink 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.

[0239] The viscosity of the white ink is measured at 25° C. using a viscometer, for example, a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd.

[0240] The surface tension (25° C.) of the white ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 25 mN / m to 40 mN / m.

[0241] The surface tension is measured at 25° C. using a surface tensiometer, for example, by a plate method using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”).

[0242] (Provision of white ink)

[0243] In the recording process, white ink is applied to the front surface of the non-permeable substrate by an inkjet method to record a white image.

[0244] There is no particular limitation on the method of ejecting white ink based on the inkjet method, and it may be any of the known methods, for example, a charge control method that utilizes electrostatic attraction 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 beam onto 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 resulting pressure.

[0245] 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 subjected to thermal energy undergoes a rapid volume change, 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 applied.

[0246] The application of the white ink onto the non-permeable substrate by the inkjet recording method is performed by ejecting the white ink from the nozzles of the inkjet head.

[0247] The inkjet head types include a reciprocating type, in which a short serial head performs recording while scanning in the width direction of the recording medium, and a line type, in which a line head (Line Heat) is used in which recording elements are arranged corresponding to the entire area of ​​one side of the recording medium.

[0248] In the linear method, by scanning 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 linear method, there is no need for a transport system such as a carriage that scans the short strip-shaped inkjet head in the reciprocating method. In addition, compared with the reciprocating method, in the linear method, there is no need for the movement of the carriage and the complex scanning control of the recording medium, and only the recording medium needs to be moved. Therefore, according to the linear method, it is possible to achieve high-speed image recording compared with the reciprocating method.

[0249] The application of white ink is preferably performed 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 1 inch is 2.54 cm.

[0250] From the viewpoint of obtaining a high-definition image, the ejection amount of the white ink is preferably 1 pL (picoliter) to 10 pL, and more preferably 1.5 pL to 6 pL.

[0251] (Drying of white ink)

[0252] In the recording step, the white ink applied to the front surface of the non-permeable substrate can be dried to obtain a white image.

[0253] The method for drying the white ink is not particularly limited, and examples thereof include infrared (IR) drying, warm air drying (eg, a dryer), and heating drying using a heating device (eg, a heater, a hot plate, a heating furnace, etc.).

[0254] As the method of heat drying, a method of combining two or more of these may be used.

[0255] Heat drying can be performed by heating the white ink from at least one of the front side and the back side of the impermeable substrate.

[0256] The heating temperature during heat drying of the white 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.

[0257] The upper limit of the heating temperature is not particularly limited, but is preferably 100°C, more preferably 90°C.

[0258] The heating time during heat drying of the white ink is not particularly limited, but is preferably 1 second to 180 seconds, more preferably 1 second to 120 seconds, and even more preferably 1 second to 60 seconds.

[0259] (Record of colored images)

[0260] The recording step may further include applying a colored ink containing water and a colored pigment to the front surface of the non-permeable substrate by an inkjet method to record the colored image.

[0261] According to this aspect, a multi-color image including a white image and a colored image can be recorded on the front surface of the impermeable substrate.

[0262] In this method, only one coloring ink can be used to record only one coloring image (for example, one of a cyan image, a magenta image, a yellow image, and a black image), or more than two coloring inks can be used to record more than two coloring images (for example, two or more of a cyan image, a magenta image, a yellow image, and a black image).

[0263] The colored image may be recorded before or after the white image.

[0264] As a method of recording a colored image before a white image, for example, a method in which a colored image (e.g., a pattern image such as a character or a graphic) is arranged between the front surface of the impermeable substrate and a white image (e.g., a solid image) can be cited. This method is a method in which the colored image (e.g., a pattern image such as a character or a graphic) with a white image (e.g., a solid image) as a background is visually recognized from the back side of the impermeable substrate through the impermeable substrate.

[0265] As a method of recording a colored image after a white image, for example, a method of placing a colored image (e.g., a pattern image such as characters or graphics) on a white image (e.g., a solid image) can be cited. This method is a method in which the colored image (e.g., a pattern image such as characters or graphics) on the upper layer side with the white image (e.g., a solid image) on the lower layer side as the background is visually recognized from the front side of the impermeable substrate.

[0266] From the viewpoint of more effectively suppressing the blocking of the multi-color images including the white image and the colored image, it is preferred that the colored image is recorded before the white image and arranged between the front surface of the non-permeable substrate and the white image.

[0267] When this method is applied, compared with a method in which a colored image is recorded after a white image and the colored image is arranged on the white image, the contact area between the white image and the back surface of the non-permeable substrate becomes larger, so that the blocking of multiple color images can be more effectively suppressed.

[0268] -Coloring ink-

[0269] The coloring ink for recording a coloring image contains water and a coloring pigment (ie, a color or black pigment).

[0270] Preferred aspects of the colored ink are the same as those of the aforementioned preferred aspects of the white ink, except for the type of pigment.

[0271] The coloring pigment may be any of commercially available organic pigments and inorganic pigments.

[0272] Examples of coloring pigments include pigments described in "Encyclopedia of Pigments" edited by Seijiro Ito (published in 2000), "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.

[0273] Furthermore, the coloring pigment may be a water-insoluble pigment that can be dispersed in water using a dispersant, or may be a self-dispersible pigment.

[0274] The self-dispersible pigment is a pigment that can be dispersed in water without using a dispersant.

[0275] The self-dispersible pigment is, for example, a compound in which at least one selected from the group consisting of hydrophilic groups such as carbonyl, hydroxyl, carboxyl, sulfonyl, and phosphoric acid groups and salts thereof is chemically bonded to the surface of the pigment directly or via other groups.

[0276] From the viewpoint of the density of the colored image and the ejection properties of the colored ink, the content of the colored pigment in the colored ink is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 1 to 10% by mass, relative to the total amount of the ink.

[0277] <Pre-treatment liquid application step>

[0278] The recording method of the present invention may further include a step of applying a pretreatment liquid containing water and a coagulant to the front surface of the impermeable substrate before the recording step (hereinafter also referred to as a "pretreatment liquid applying step").

[0279] In this case, in the recording step, the white ink is applied to the area on the front surface to which the pretreatment liquid is applied, thereby recording the white image.

[0280] According to the embodiment including the pre-treatment liquid application step, the components of the white ink are aggregated by the action of the aggregating agent applied to the front surface in advance, which is advantageous in terms of the image quality of the white image.

[0281] In the embodiment including the pre-treatment liquid application step, the above-mentioned colored image can be recorded in addition to the white image.

[0282] In this case, the color ink is applied to the area on the front side to which the pretreatment liquid is applied to record the color image. This allows the components of the color ink to aggregate due to the action of the aggregating agent, which is advantageous in terms of the image quality of the color image.

[0283] As described above, the colored image may be recorded on the upper layer side of the white image (the side away from the impermeable substrate) or on the lower layer side of the white image (the side close to the impermeable substrate. That is, between the front surface of the impermeable substrate and the white image.)

[0284] (Pretreatment liquid)

[0285] The pretreatment liquid contains water and a coagulant.

[0286] -water-

[0287] The pretreatment liquid contains water.

[0288] The content of water is preferably 50% by mass or more, more preferably 60% by mass or more, based on the total amount of the pretreatment liquid.

[0289] The upper limit of the water content depends on the amounts of other components, but is preferably 90% by mass or less, and more preferably 80% by mass or less, based on the total amount of the pretreatment liquid.

[0290] - Coagulant -

[0291] The pretreatment liquid contains at least one coagulant.

[0292] The coagulant in the pretreatment liquid aggregates the components in the ink on the non-permeable substrate, thereby improving the image quality.

[0293] The coagulant is preferably at least one selected from the group consisting of organic acids, polyvalent metal compounds, metal complexes, and cationic polymers.

[0294] Preferred examples of the coagulant include those described in paragraphs 0122 to 0130 of International Publication No. 2020 / 195360.

[0295] 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.

[0296] --Organic Acids--

[0297] Examples of the organic acid include organic compounds having an acidic group.

[0298] 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.

[0299] 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.

[0300] It is preferred that at least a part of the acidic groups be dissociated in the pretreatment liquid.

[0301] 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.

[0302] 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.

[0303] 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.

[0304] The organic acid preferably has a low pKa (eg, 1.0 to 5.0). Thus, 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 is reduced by contact with an organic acid with a lower pKa, thereby reducing dispersion stability.

[0305] 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.

[0306] --Multivalent Metal Compounds--

[0307] Examples of the polyvalent metal compound include polyvalent metal salts.

[0308] Examples of the polyvalent metal salt include organic acid polyvalent metal salts and inorganic acid polyvalent metal salts.

[0309] 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.

[0310] As the inorganic acid polyvalent metal salt, a nitrate polyvalent metal salt, a hydrochloride polyvalent metal salt or a thiocyanate polyvalent metal salt is preferred.

[0311] 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).

[0312] As the polyvalent metal salt, a calcium salt, a magnesium salt or an aluminum salt is preferred, and a calcium salt or a magnesium salt is more preferred.

[0313] As the polyvalent metal compound, an organic acid polyvalent metal salt is preferred, and an organic acid calcium salt or an organic acid magnesium salt is more preferred.

[0314] 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.

[0315] --Metal Complexes--

[0316] The metal complex preferably contains at least one selected from the group consisting of zirconium, aluminum, and titanium as a metal element.

[0317] The metal complex is preferably a metal complex containing at least one selected from the group consisting of acetate, acetylacetonate, methyl acetoacetate, ethyl acetoacetate, octanediol, butoxyacetylacetone, lactate, lactate ammonium salt and triethanolaminate as a ligand.

[0318] The metal complex may be a commercially available product. Various organic ligands, especially various multidentate ligands capable of forming metal chelate catalysts, are commercially available. Therefore, the metal complex may be a metal complex prepared by combining commercially available organic ligands and metals.

[0319] --Cationic polymers--

[0320] The cationic polymer is preferably a homopolymer of a cationic monomer having a primary or tertiary amino group or a quaternary ammonium salt group, a copolymer or a 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 a water-insoluble polymer (ie, latex particles).

[0321] Examples of the cationic polymer include polyvinyl pyridinium salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimidazoles, polyethyleneimine, polybiguanide, polyguanidine, polyallylamine, and derivatives thereof.

[0322] From the viewpoint of the viscosity of the pretreatment liquid, the cationic polymer preferably has a small weight average molecular weight. When the pretreatment liquid is applied to the resin substrate 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. When the weight average molecular weight is 1000 or more, it is advantageous from the viewpoint of the coagulation rate. When the weight average molecular weight is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, when the pretreatment liquid is applied to the resin substrate by a method other than inkjet recording, it is not limited thereto.

[0323] 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 further preferably 1 to 10% by mass, based on the total amount of the pretreatment liquid.

[0324] -Resin-

[0325] The pretreatment liquid may contain at least one resin.

[0326] The resin in the pretreatment liquid contributes to the film-forming property of the pretreatment liquid (that is, the formability of a film based on the pretreatment liquid).

[0327] As the resin in the pretreatment liquid, the same resin as the resin in the ink (for example, resin particles) can be used.

[0328] The content of the resin in the pretreatment liquid is not particularly limited.

[0329] 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, based on the total amount of the pretreatment liquid.

[0330] -Water-soluble organic solvents-

[0331] The pretreatment liquid may contain at least one water-soluble organic solvent.

[0332] As the water-soluble organic solvent in the pretreatment liquid, the same water-soluble organic solvent as that which can be contained in the ink can be used.

[0333] -additive-

[0334] 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 necessary.

[0335] -Physical properties-

[0336] The pH of the pretreatment liquid is preferably 2.0 to 7.0, and 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.

[0337] From the viewpoint of coating properties of the pretreatment liquid, the viscosity of the pretreatment liquid is preferably 0.5 to 10 mPa·s, more preferably 1 to 5 mPa·s. The viscosity is a value measured using a viscometer at 25° C. The viscosity of the pretreatment liquid is measured by the same method as the viscosity of the ink.

[0338] 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 of the pretreatment liquid is measured by the same method as the surface tension of the ink.

[0339] (Method of applying pretreatment liquid)

[0340] 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.

[0341] Examples of the coating method include known coating 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.

[0342] (Drying of pretreatment liquid)

[0343] The step of applying the pretreatment liquid may include a step of drying the pretreatment liquid applied to the non-permeable substrate.

[0344] 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 white ink can be applied.

[0345] The preferred range of drying conditions (for example, heating temperature and heating time) of the pretreatment liquid is the same as the preferred range of drying conditions of the white ink.

[0346] <Coiling process>

[0347] The recording method of the present invention includes a winding step of winding the impermeable substrate having the white image recorded thereon while a tension P is applied thereto.

[0348] The winding step is not particularly limited, and can be performed using a known winding device including a winding core.

[0349] The recording method of the present invention may include other steps besides the above steps.

[0350] <Image recording device>

[0351] The image recording device used in the image recording method of the present invention comprises:

[0352] a recording unit including an inkjet head for applying the white ink to one surface of the non-permeable substrate and performing a recording step of recording the white image on the one surface of the non-permeable substrate; and

[0353] The winding section includes a winding device for winding the impermeable substrate having the white image recorded thereon under tension, and performs the winding step.

[0354] The above-mentioned ΔE / P ratio is 0.06 to 0.60.

[0355] According to the above-mentioned image recording device, the same effects as those of the above-mentioned image recording method of the present invention can be achieved.

[0356] <An example of an image recording device>

[0357] Figure 1 This is a diagram conceptually showing an example of an image recording device used in the image recording method of the present invention.

[0358] like Figure 1 As shown, the inkjet recording device involved in this example is an example of an inkjet recording device having a conveying mechanism for conveying a resin substrate in a roll-to-roll manner, which is a device as follows: a non-permeable substrate A1 in the shape of a long film wound into a roll is unwound by a unwinding device R1, and the unwound non-permeable substrate A1 is conveyed in the direction of the block arrow under a tension applied thereto so that it passes through a pretreatment liquid imparting device P1, a pretreatment liquid drying area DP1, a first inkjet head IJ1, a first drying area D1, a second inkjet head IJ2 and a drying area D2 in sequence, and is finally wound up by a winding device R2 including a winding core under a tension P applied thereto.

[0359] The impermeable substrate A1 is conveyed under tension and is wound under tension P. The tension during conveyance may be the same tension as or different from the tension P during winding. Furthermore, the tension may be different depending on the position in the conveyance direction or may be the same tension.

[0360] The image recording apparatus according to this example may include a tension adjustment mechanism for adjusting the tension applied to the impermeable substrate.

[0361] As the tension adjustment mechanism, there are:

[0362] A powder brake (Powder Brake) provided on the unwinding device R1 and / or the winding device R2;

[0363] A dancer roller disposed in the conveying path; and

[0364] A control device (eg, a tension controller) that controls each tension by adjusting various conditions of the image recording device.

[0365] Furthermore, the image recording apparatus according to this example may include a tension measuring mechanism (for example, a tensiometer) for measuring the tension of the impermeable substrate.

[0366] In addition, due to Figure 1 This is a conceptual diagram, and thus the conveying path of the impermeable substrate A1 is simplified and illustrated as if the impermeable substrate A1 is conveyed in one direction, but it goes without saying that the conveying path of the impermeable substrate A1 may be curved in reality.

[0367] As a conveyance method of the impermeable substrate A1, various web conveyance methods such as a drum and a roll can be appropriately selected.

[0368] Relative to the unwinding device R1 for unwinding the non-permeable substrate A1, on the downstream side of the conveying direction of the non-permeable substrate A1, a pretreatment liquid applying device P1, a pretreatment liquid drying area DP1, a first inkjet head IJ1, a first drying area D1, a second inkjet head IJ2 and a drying area D2 are arranged in sequence from the upstream side of the conveying direction of the non-permeable substrate A1.

[0369] The pretreatment liquid applying device P1 , the first inkjet head IJ1 , and the second inkjet head IJ2 respectively apply the pretreatment liquid, apply the first ink, and apply the second ink.

[0370] 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 may be performed.

[0371] In the first drying area D1, in addition to heating and drying the first ink, the pre-treatment liquid can also be heated and dried substantially.

[0372] In the second drying area D2, in addition to heating and drying the second ink, heating and drying of the pretreatment liquid and / or heating and drying of the first ink can also be performed substantially.

[0373] 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 drying can be omitted.

[0374] In this example, the first ink is either a colored ink containing water and a coloring pigment for recording a colored image or a white ink containing water and a white pigment for recording a white image, and the second ink is the other of the colored ink and the white ink.

[0375] 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 impermeable substrate A1 may be provided upstream of the pretreatment liquid applying device P1.

[0376] Furthermore, a cooling area for cooling the recorded multi-color image (ie, the multi-color image including the white image and the colored image) may be provided downstream of the second drying zone D2.

[0377] The first inkjet head IJ1 and the second inkjet head IJ2 may be reciprocating inkjet 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 non-permeable substrate A1.

[0378] The number of the first inkjet head IJ1 and the number of the second inkjet head IJ2 may be only one or a plurality.

[0379] As an example of a combination of the first inkjet head IJ1 and the second inkjet head IJ2, for example, the following combination can be cited: the first inkjet head IJ1 is four inkjet heads corresponding to 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).

[0380] 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 (i.e., white), and the second inkjet head IJ2 is four inkjet heads corresponding to four colors of cyan, magenta, yellow, and black (Note: these four inkjet heads are arranged along the conveying direction of the resin substrate).

[0381] In inkjet recording using the image recording apparatus according to this example,

[0382] First, the long film-shaped impermeable substrate A1 wound into a roll is unwound by the unwinding device R1.

[0383] The released impermeable substrate A1 is conveyed in the direction of the block arrow under a tension.

[0384] The pretreatment liquid applying device P1 applies the pretreatment liquid to the transported non-permeable substrate A1.

[0385] Next, the pre-treatment liquid is dried in the pre-treatment liquid drying area DP1 as required.

[0386] Next, the first ink (that is, either the color ink or the white ink) is applied by the first inkjet head IJ1.

[0387] Next, the first ink is dried in the first drying area D1 as needed.

[0388] Next, the second ink (that is, the other of the color ink and the white ink) is applied by the second inkjet head IJ2.

[0389] Next, the second ink is dried in the second drying area D2 as necessary.

[0390] Thus, a multi-color image including a first image derived from the first ink (ie, one of the colored image and the white image) and a second image derived from the second ink (ie, the other of the colored image and the white image) can be obtained.

[0391] Next, the obtained multi-color image is cooled as necessary, and finally the non-permeable substrate A1 with the multi-color image is wound up with a winding device R2 including a winding core under a tension P applied thereto.

[0392] In this example, the surface energy difference ΔE (mJ / m 2 ) divided by the tension immediately before the winding device R2, that is, the tension P (N / m), i.e., the ΔE / P ratio is adjusted to 0.06 to 0.60.

[0393] This can suppress winding deviation and blocking of the white image in the rolled-up impermeable substrate A1.

[0394] At this time, in the case where the first image is a colored image and the second image is a white image (i.e., the colored image is recorded before the white image) and the colored image is arranged between the impermeable substrate and the white image, the white image becomes the upper layer side, so the entire surface of the white image contacts the back surface of the impermeable substrate. As a result, the contact area between the white image and the back surface of the impermeable substrate becomes larger, so the blocking suppression effect of the multi-color image is more excellent compared to the case where the colored image is the upper layer side.

[0395] In addition, the application and drying of the pretreatment liquid in this example can be omitted.

[0396] Furthermore, in this example, it is possible to record only a white image instead of a colored image.

[0397] Example

[0398] Examples of the present invention are described below, but the present invention is not limited to the following examples.

[0399] <Preparation of pretreatment solution>

[0400] The following components were mixed to prepare a pretreatment liquid.

[0401] - Composition of pretreatment solution -

[0402] Glutaric acid (coagulant)

[0403] ...6.1% by mass

[0404] Propylene glycol (PG) [other water-soluble organic solvents]

[0405] ...20% by mass

[0406] ·OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.)〔Surfactant〕

[0407] ...0.5% by mass

[0408] SUPER FLEX 500M (DKS Co., Ltd.)〔Aqueous dispersion of urethane resin particles〕

[0409] ...7.0% by mass

[0410] ·Triisopropanolamine (pH adjuster)

[0411] ...0.2% by mass

[0412] BYK024 (BYK)〔Defoaming agent〕

[0413] ...0.01% by mass

[0414] Ultrapure water

[0415] ...the remainder of the pretreatment liquid is 100% by mass

[0416] <Preparation of white ink W1>

[0417] The following components were mixed to prepare white ink W1.

[0418] - Composition of white ink W1 -

[0419] ·The following white pigment dispersion

[0420] ...12% by mass in terms of white pigment content

[0421] Propylene glycol (PG) [other water-soluble organic solvents]

[0422] ...28% by mass

[0423] Propylene glycol monomethyl ether (PGmME) [water-soluble organic solvent]

[0424] ...2% by mass

[0425] ·OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.) [Acetylene glycol surfactant]

[0426] ...0.60% by mass

[0427] SOLSPERSE 43000 (manufactured by The Lubrizol Corporation) [Water-soluble polymer]

[0428] ...1% by mass

[0429] ·PVP-K15 (Polyvinylpyrrolidone K15)

[0430] ...0.12% by mass

[0431] Urea

[0432] ...0.50% by mass

[0433] ·SNOWTEX XS (manufactured by Nissan Chemical Corporation) [Colloidal silica dispersion]

[0434] ...The content of colloidal silica particles is 0.1% by mass

[0435] ·NEOCRYL A1091 (manufactured by Covestro Coating Resins)〔Aqueous dispersion of styrene acrylic resin particles〕

[0436] ...5.0% by mass in terms of the content of styrene acrylic resin particles

[0437] ·water

[0438] ...white ink as a whole is the remainder of 100% by mass

[0439] (Preparation of white pigment dispersion)

[0440] -Synthesis of Pigment Dispersant P1-

[0441] 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.

[0442] Prepared respectively:

[0443] 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; and

[0444] 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.

[0445] 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.

[0446] The obtained reaction solution was heated to 70° C., 248.02 g of a 50% by mass potassium hydroxide aqueous solution was added thereto, and then 107.48 g of dipropylene glycol and 75.52 g of pure water were added thereto and stirred to obtain a 37% by mass solution of a random polymer. This random polymer was used as a pigment dispersant P1.

[0447] pass 1 The structural units constituting the obtained random polymer were confirmed by H-NMR. The weight average molecular weight (Mw) was determined by GPC. The weight average molecular weight (Mw) of the obtained pigment dispersant P1 was 8400, and the acid value was 221.7 mgKOH / g.

[0448] -Preparation of white pigment dispersion-

[0449] 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.

[0450] 96 parts by mass of the polymer aqueous 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 after neutralization to 8.7.

[0451] Next, the neutralized mixed solution was dispersed for 3 hours using a bead mill (bead diameter: 0.1 mmφ, zirconia beads), thereby obtaining a white pigment dispersion A (uncrosslinked dispersion) PD1 in which a white pigment was dispersed in the pigment dispersant P1.

[0452] Next, the obtained white pigment dispersion (uncrosslinked dispersion) PD1 was ultrafiltered using an ultrafiltration device (cross-flow ultrafilter (UF), manufactured by Sartorius) at a flow rate of 600 mL per minute by flowing ion exchange water. The liquid temperature was maintained at 25°C, and ultrafiltration was performed three times, with 1 times the volume of the produced liquid as 1 time. Ion exchange water was added to the ultrafiltered liquid to obtain an ultrafiltered dispersion having a white pigment concentration of 45% by mass and a pigment dispersant P1 concentration of 3.6% by mass.

[0453] 1.35 parts by mass of trimethylolpropane polyglycidyl ether (product name "Denacol EX-321", manufactured by Nagase ChemteX Corporation) and 14.5 parts by mass of an aqueous solution of boric acid (boric acid concentration: 4% by mass) were added as a crosslinking agent to 136 parts by mass of the above-mentioned ultrafiltrated dispersion, and the mixture was reacted at 70° C. for 6 hours, followed by cooling to 25° C. Thus, the pigment dispersant P1 in the dispersion was crosslinked to form a pigment dispersant P1a as a crosslinked polymer dispersant, and a white pigment dispersion (crosslinked dispersion) in which a white pigment was dispersed by the pigment dispersant P1a was obtained.

[0454] Ion exchange water was added to the obtained cross-linked dispersion so that the concentration of the pigment was 15% by mass. The cross-linked dispersion to which ion exchange water was added was flowed into an ultrafiltration device (cross-flow ultrafilter (UF), manufactured by Sartorius) having a polyethersulfone (PESU) membrane (pore size: 0.1 μm) at a flow rate of 600 mL per minute for ultrafiltration. At this time, the liquid temperature was adjusted to 25°C, and 1 times the volume ratio of the manufactured liquid was taken as 1 time, and ultrafiltration was performed 3 times. Next, ion exchange water was added so that the concentration of the white pigment was 45% by mass. Thus, a white pigment dispersion was obtained.

[0455] 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.

[0456] <White ink W2~W7>

[0457] White inks W2 to W7 were prepared in the same manner as in the preparation of the white ink W1 except that the ink composition was changed as shown in Table 1 below.

[0458] In the preparation of the white inks W2 to W7, the same white pigment dispersion as that used in the preparation of the white ink W1 was used.

[0459] In addition, blank columns in Table 1 indicate that the corresponding components are not contained.

[0460] <Preparation of cyan ink C1>

[0461] Cyan ink C1 was prepared in the same manner as in the preparation of white ink W1 except that the ink composition was changed as shown in Table 1 below.

[0462] In the preparation of the cyan ink C1, APD4000 Cyan (manufactured by Fujifilm Imaging Colorants Ltd.) was used as a cyan pigment dispersion liquid instead of the white pigment dispersion liquid.

[0463] [Table 1]

[0464]

[0465] -Details of ingredients in Table 1-

[0466] ·White pigment…the white pigment in the above-mentioned white pigment dispersion

[0467] · Cyan pigment: A cyan pigment in APD4000 Cyan (manufactured by Fujifilm Imaging Colorants Ltd.) as a cyan pigment dispersion

[0468] PG…propylene glycol (water-soluble organic solvent)

[0469] PGmME…Propylene glycol monomethyl ether (water-soluble organic solvent)

[0470] ·DEGmBE…Diethylene glycol monobutyl ether (water-soluble organic solvent)

[0471] ·OLFINE E1010 ... an acetylene glycol surfactant manufactured by Nissin Chemical Co., Ltd.) ·Surfynol 104P ... an acetylene glycol surfactant manufactured by Nissin Chemical Co., Ltd.

[0472] BYK-347…Silicone-based surfactant manufactured by BYK.

[0473] Solsperse 43000…a water-soluble polymer manufactured by The Lubrizol Corporation

[0474] ·PVP-K15…Polyvinylpyrrolidone K15.

[0475] ·SNOWTEX XS ... colloidal silica dispersion manufactured by Nissan Chemical Corporation. The contents in Table 1 are the contents based on the solid content (colloidal silica particles).

[0476] SuperFlex: SuperFlex 460. Aqueous dispersion of urethane resin particles manufactured by DKS Co., Ltd. The contents in Table 1 are based on solid content (resin particles).

[0477] · NEOCRYL A1091 ... aqueous dispersion of styrene acrylic resin particles manufactured by Covestro Coating Resins. The contents in Table 1 are based on solid content (resin particles).

[0478] <Preparation of image recording equipment>

[0479] As an image recording device for evaluation, the above-mentioned example was prepared. Figure 1 The image recording device shown.

[0480] As the pretreatment liquid applying device P1, a gravure coater was used.

[0481] The drying method in the pretreatment liquid drying zone DP1 is set to warm air drying.

[0482] As the first inkjet head IJ1, a cyan inkjet head is arranged.

[0483] As the second inkjet head IJ2, a white inkjet head is arranged.

[0484] All inkjet heads and ink ejection conditions were as follows.

[0485] Inkjet head: A piezo full line head with a 1200 dpi (dot per inch: dots per inch, 1 inch is 2.54 cm) / 20 inch width (total number of nozzles: 2048) was used.

[0486] Ink drop volume: set to 2.0 pL.

[0487] Drive frequency: set to 30kHz.

[0488] The drying method in the first drying zone D1 and the second drying zone D2 is warm air drying.

[0489] An air cooling zone (not shown) is provided between the second drying zone D2 and the winding device R2.

[0490] A tension controller ("LE-40MTA" manufactured by Mitsubishi Electric Corporation) was incorporated in the inkjet recording apparatus, and the tension applied to the non-permeable substrate (particularly, the tension P at the take-up section described below) was controlled by the tension controller during the inkjet recording described below.

[0491] <Preparation of non-permeable substrate>

[0492] As the impermeable substrates used for evaluation, the following impermeable substrates were prepared.

[0493] In each of the examples and comparative examples described below, any of the following impermeable substrates was used (for details, refer to Table 2).

[0494] · P2161 ... OPP film "PYLEN FILM-OT" manufactured by Toyobo Co., Ltd. The thickness is 25 μm or 40 μm.

[0495] ·PET…PET film “Taiko polyester film FE2001” manufactured by Futamura Chemical Co., Ltd. The thickness was 12 μm, 25 μm, or 50 μm.

[0496] · Back-side treated PET… A film obtained by corona-treating the back side of a PET film "Taiko Polyester Film FE2001" (thickness 12 μm) manufactured by Futamura Chemical Co., Ltd. The corona treatment was performed using a corona treatment apparatus "Corona Master PS-10S" manufactured by Shinko Electric & Instrumentation Co., Ltd. at a treatment voltage of 15 kV and a treatment speed of 100 mm / s.

[0497] FOR-AQ ... OPP film "Taiko polypropylene film" manufactured by Futamura Chemical Co., Ltd. Thickness: 25 μm.

[0498] · Nylon: Nylon film "ON-25" manufactured by UNITIKA LTD. Thickness: 25 μm.

[0499] [Example 1]

[0500] <Image Record>

[0501] The following inkjet recording was performed using the above-mentioned image recording apparatus, the non-permeable substrate (P2161, thickness 25 μm), the above-mentioned pre-treatment liquid and the above-mentioned white ink W1 to obtain a substrate with an image. In Example 1, no cyan ink was used, and no treatment was performed at the first inkjet head IJ1 and the first drying area D1.

[0502] First, the non-permeable substrate is unwound by the unwinding device R1.

[0503] The released impermeable substrate is transported under tension.

[0504] The pretreatment liquid is applied to the conveyed non-permeable substrate by a gravure coater as the pretreatment liquid applying device P1.

[0505] Next, the pretreatment liquid is dried in the pretreatment liquid drying area DP1.

[0506] Then, it passes directly through the first inkjet head IJ1 and the first drying area D1 without stopping.

[0507] Next, the second inkjet head IJ2 applies the white ink W1 in a solid image to the area of ​​the non-permeable substrate to which the pre-treatment liquid has been applied.

[0508] Next, the white ink W1 is dried in the second drying area D2.

[0509] Through the above operation, a white image (solid image) derived from the white ink W1 is recorded on the conveyed non-permeable substrate, thereby obtaining a substrate with an image.

[0510] Next, the obtained substrate with an image is air-cooled and then wound up by a winding device R2 including a winding core, thereby obtaining a substrate roll with an image.

[0511] In the above image recording, the conveying speed of the impermeable substrate was adjusted to 70 m / min, and the tension P of the impermeable substrate at a distance within one meter (1 m) from the take-up device R2 (hereinafter also referred to as "the tension P of the take-up section") was adjusted to the value shown in Table 2. The tension P (N / m) of the take-up section was measured by a tensiometer.

[0512] The amount of pretreatment liquid applied was set to 1.7 g / m 2 .

[0513] The amount of white ink applied was set to 3.8 g / m 2 .

[0514] The drying conditions of the pretreatment liquid were set at 40° C. and 3 seconds.

[0515] The drying conditions of the white ink were set at 70° C. and 20 seconds (hereinafter, this drying condition is referred to as “control”).

[0516] <Measurement of surface energy and calculation of surface energy difference ΔE>

[0517] Immediately before the image recording starts (specifically, at least one hour before the start of the image recording), the surface energy (i.e., the dispersed component γ) of the back side of the non-permeable substrate is measured in advance by the above-mentioned method. S d , hydrogen bond component γ S h and surface energy γ S ).

[0518] After winding up during the image recording (specifically, within 1 hour after winding up), the substrate with the image was loosened, and the surface energy of the white image in the substrate with the image (i.e., the dispersed component γ) was measured by the above method. S d , hydrogen bond component γ S h and surface energy γ S ).

[0519] Based on the above measurement results, the surface energy difference ΔE (mJ / m 2 ).

[0520] The above results are shown in Table 2.

[0521] <Calculation of ΔE / P ratio>

[0522] The ΔE / P ratio was calculated from the surface energy difference ΔE and the tension P of the winding portion.

[0523] The results are shown in Table 2.

[0524] <Evaluation>

[0525] The image recording was performed on a length of 1000 m of the impermeable substrate by the above-described image recording, thereby obtaining an image-attached substrate roll having a length of 1000 m of the impermeable substrate.

[0526] The following evaluations were performed using the obtained substrate roll with an image.

[0527] The results are shown in Table 2.

[0528] (Stick of white image)

[0529] The image-bearing substrate roll was unwound, and blocking of the white image was evaluated in accordance with the following evaluation criteria at a position approximately 100 m from the end of winding.

[0530] In the following evaluation criteria, the level in which sticking of the white image is most suppressed is AA.

[0531] -Evaluation criteria for sticking of white images-

[0532] AA: At a position approximately 100 m from the winding end position, no peeling sound due to winding loosening was heard, and no transferred material was confirmed on the back surface of the impermeable substrate.

[0533] A: At a position of about 100 m from the winding end position, a peeling sound caused by loosening of the winding was sometimes heard, but no transfer material was confirmed on the back surface of the impermeable substrate.

[0534] B: At a position of about 100 m from the winding end position, peeling noise due to winding loosening was continuously heard, but no transfer material was confirmed on the back surface of the impermeable substrate.

[0535] C: A colorless and transparent transferred material was confirmed on the back surface of the impermeable substrate at a position approximately 100 m from the winding end position.

[0536] D: A transferred white image was confirmed on the back surface of the impermeable substrate at a position approximately 100 m from the winding end position.

[0537] (Warping of non-permeable substrates)

[0538] The image-carrying substrate roll used in the evaluation of the blocking of the white image was observed, and the maximum value of the distance (deviation) between the axial end of the roll core and the width end of the non-permeable substrate was measured, and the measurement result was taken as the roll deviation amount of the non-permeable substrate. Based on the roll deviation amount of the non-permeable substrate, the roll deviation of the non-permeable substrate was evaluated according to the following evaluation criteria.

[0539] In the following evaluation criteria, the non-permeable substrate with the best suppression of curling was rated AA.

[0540] -Evaluation criteria for curling of non-permeable substrates-

[0541] AA: The curling deviation of the non-permeable substrate is less than 0.5 mm.

[0542] A: The winding deviation of the impermeable substrate is 0.5 mm or more and less than 1.0 mm.

[0543] B: The winding amount of the impermeable substrate is 1.0 mm or more and less than 2.0 mm.

[0544] C: The winding amount of the impermeable substrate is 2.0 mm or more and less than 3.0 mm.

[0545] D: The winding deviation of the impermeable substrate is 3.0 mm or more.

[0546] [Examples 2 to 7, 9 to 12]

[0547] The same operation as in Example 1 was performed except that at least one of the type of white ink, the drying conditions of the white ink, the type of impermeable substrate, the thickness of the impermeable substrate, and the tension P of the winding portion was changed as shown in Table 2.

[0548] The results are shown in Table 2.

[0549] Regarding the drying conditions of the white ink, “strong drying” refers to a drying condition of 75° C. for 20 seconds, and “weak drying” refers to a drying condition of 65° C. for 20 seconds.

[0550] [Example 8]

[0551] The same operation as in Example 2 was performed except that application of the cyan ink C1 by the first inkjet head IJ1 and drying of the cyan ink C1 in the first drying area D1 were added between drying of the pretreatment liquid and application of the white ink.

[0552] The results are shown in Table 2.

[0553] In Example 8, cyan ink C1 is applied in a solid image to the area of ​​the non-permeable substrate to which the pretreatment liquid is applied, and white ink W1 is applied in a solid image and in an overlapping manner on the cyan ink C1 applied to the above area (i.e., on the cyan solid image).

[0554] The drying conditions of the cyan ink C1 were set to 70° C. and 20 seconds (ie, “control”).

[0555] [Comparative Examples 1 to 5]

[0556] The same operation as in Example 1 was performed except that at least one of the type of white ink, the drying conditions of the white ink, the type of impermeable substrate, the thickness of the impermeable substrate, and the tension P of the winding portion was changed as shown in Table 2.

[0557] The results are shown in Table 2.

[0558]

[0559] As shown in Table 2, in Examples 1 to 12 in which the ΔE / P ratio was 0.06 to 0.60, blocking of the white image and curling of the non-permeable substrate were suppressed.

[0560] On the other hand, in Comparative Examples 2 to 4 in which the ΔE / P ratio was less than 0.06, the blocking of the white image could not be suppressed.

[0561] Furthermore, in Comparative Examples 1 and 5 in which the ΔE / P ratio exceeded 0.60, although the blocking of the white image could be suppressed, the curling of the non-permeable substrate could not be suppressed.

[0562] From the results of Examples 1, 5, 11, and 12, it can be seen that when ΔE is 5.0 to 25.0 (Examples 1 and 5), the curling of the impermeable substrate can be further suppressed.

[0563] From the results of Examples 1, 6, 7 and 10, it can be seen that when P is 30 to 150 (Examples 1, 6 and 10), the curling of the impermeable substrate can be further suppressed.

[0564] From the results of Examples 1 to 12, it is understood that when the ΔE / P ratio is 0.10 or more (Examples 2 to 9, 11, and 12), the blocking of the white image can be further suppressed.

[0565] From the results of Examples 1 to 12, it is understood that when the ΔE / P ratio is 0.50 or less (Examples 1 to 6 and 8 to 11), the curling of the impermeable substrate can be further suppressed.

[0566] [Variation of Example 8]

[0567] The same operation as in Example 8 was performed except that the cyan ink C1 in Example 8 was replaced with the magenta ink M1 prepared as follows (variation of Example 8). As a result, the same evaluation results as those in Example 8 were obtained in this variation as well.

[0568] <Preparation of Magenta Ink M1>

[0569] Magenta ink M1 was prepared in the same manner as in the preparation of cyan ink C1, except that the cyan pigment dispersion liquid (APD4000 Cyan; manufactured by Fujifilm Imaging Colorants Ltd.) used in the preparation of cyan ink C1 was changed to APD4000 Magenta (manufactured by Fujifilm Imaging Colorants Ltd.) and APD1000 Red (manufactured by Fujifilm Imaging Colorants Ltd.) as magenta pigment dispersion liquids. At this time, the usage amounts of APD4000 Magenta and APD1000 Red were adjusted so that the content of the pigment in APD4000 Magenta was 4.9% by mass relative to the total amount of magenta ink M1, and the content of the pigment in APD1000 Red was 1.6% by mass relative to the total amount of magenta ink M1.

[0570] Although the example group in which the pre-treatment liquid is applied before applying the white ink is described above, the application of the pre-treatment liquid may be omitted.

[0571] When the application of the pretreatment liquid is omitted and a white image is recorded on the non-permeable substrate directly or via a colored image, the effects of suppressing blocking of the white image and suppressing curling of the non-permeable substrate can be obtained as in the above-mentioned Example Group.

[0572] The entire contents of Japanese Patent Application No. 2022-122181 filed on July 29, 2022 are incorporated into this specification by reference.

[0573] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually described as being incorporated by reference.

Claims

1. An image recording method, comprising: A recording step of applying white ink containing water and white pigment to one surface of the non-permeable substrate by inkjet method to record a white image; and a winding step of winding the impermeable substrate having the white image recorded thereon under tension, When the other side of the non-permeable substrate is brought into contact with the surface of the white image, the 2 When the surface energy difference in units is denoted as ΔE and the tension in N / m is denoted as P, the ΔE / P ratio, which is a value obtained by dividing ΔE by P, is in the range of 0.06 to 0.

60.

2. The image recording method according to claim 1, wherein: The recording process further includes the step of applying a coloring ink containing water and a coloring pigment to the one surface of the non-permeable substrate by an inkjet method to record a coloring image.

3. The image recording method according to claim 2, wherein: The colored image is recorded before the white image and is arranged between the one surface of the non-permeable substrate and the white image.

4. The image recording method according to any one of claims 1 to 3, wherein: The ΔE is 5.0 to 25.

0.

5. The image recording method according to any one of claims 1 to 3, wherein: The P is 30-150.

6. The image recording method according to any one of claims 1 to 3, wherein: The ΔE / P ratio is 0.10 to 0.

50.

7. The image recording method according to any one of claims 1 to 3, wherein: Before the recording step, the method further includes applying a pretreatment liquid containing water and a coagulant to the one surface of the non-permeable substrate. In the recording step, the white ink is applied to the region on the one surface to which the pretreatment liquid is applied, thereby recording the white image.

8. An image recording device used in the image recording method according to any one of claims 1 to 7, The image recording device comprises: a recording unit including an inkjet head for applying the white ink to one surface of the non-permeable substrate and performing a recording step of recording the white image on the one surface of the non-permeable substrate; and The winding section includes a winding device for winding the impermeable substrate having the white image recorded thereon under tension, and performs the winding step. The ΔE / P ratio is 0.06 to 0.60.

Images