Image recording method and image recording apparatus

Abstract

An image recording method includes: a recording step of recording a white image by applying a white ink containing water and a white pigment to one surface of a non-penetrable substrate by an inkjet method; and a winding step of winding the non-penetrable substrate on which the white image is recorded in a state where a tension is applied, wherein a surface energy difference of mJ / m 2 In a case where the surface energy difference is ΔE and the tension in the unit of N / m is P, a ratio ΔE / P obtained by dividing ΔE by P is 0.06 to 0.60.

Description

Technical Field

[0001] This invention relates to an image recording method and an image recording apparatus. Background Technology

[0002] In the past, various studies have been conducted on image recording methods.

[0003] For example, in Patent Document 1, an aqueous inkjet ink composition is disclosed that provides a recordable material with excellent abrasion resistance and adhesion resistance while ensuring printout stability during recording. The composition contains resin particles, a nonionic surfactant, a resin-soluble solvent, and water. The acid value of the resin particles in the aqueous inkjet ink composition, and the total acid value of the resin particles and the dispersant resin when the aqueous inkjet ink composition contains a dispersant resin, is 200 (mgKOH / 100g ink) or less.

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

[0005] The technical problem to be solved by the invention

[0006] In image recording, where white images are recorded by applying white ink to a non-permeable substrate using an inkjet method and then winding up the non-permeable substrate containing the recorded white images, it is sometimes necessary to suppress the adhesion of the white images.

[0007] However, through the research of the inventors, it has been determined that when attempting to suppress the adhesion of white images in the aforementioned image recording, it is easy to cause the non-permeable substrate to roll off.

[0008] Therefore, in the above image recording, it is sometimes necessary to suppress the adhesion of white images and the roll-off of non-permeable substrates.

[0009] Here, the adhesion of the white image refers to the process where, after the non-permeable substrate on which the white image is recorded is wound up, the white image is adhered to the back of the image on the non-permeable substrate that is in contact with the surface of the white image.

[0010] Furthermore, the roll-off of the non-permeable substrate refers to the phenomenon that, as the non-permeable substrate on which the white image is recorded is wound up, the position of the wound non-permeable substrate gradually shifts along the winding axis.

[0011] The present invention was made in view of this situation, and its object is to provide an image recording method and an image recording apparatus that can record white images on a non-permeable substrate and suppress the adhesion of white images and the deflection of the non-permeable substrate when the non-permeable substrate on which the white images are recorded is wound up.

[0012] means for solving technical problems

[0013] The present invention includes the following methods.

[0014] <1> An image recording method, comprising: a recording step, wherein a white image is recorded by applying white ink containing water and white pigment to one surface of a non-porous substrate via inkjet printing; and a winding step, wherein the non-porous substrate on which the white image is recorded is wound up under tension.

[0015] The mJ / m of the non-permeable substrate surface compared to the surface of the white image. 2 When the surface energy difference per unit is ΔE and the tension per unit of N / m is P, the value obtained by dividing ΔE by P, i.e., the ΔE / P ratio, is 0.06 to 0.60.

[0016] <2> According to the image recording method described in <1>, wherein,

[0017] The recording process also includes recording a colored image by applying a coloring ink containing water and coloring pigments to one side of a non-permeable substrate using an inkjet printing method.

[0018] <3> According to the image recording method described in <2>, wherein,

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

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

[0021] ΔE ranges from 5.0 to 25.0.

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

[0023] P ranges from 30 to 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 includes, prior to the recording step, a step of applying a pretreatment liquid containing water and a coagulant to one surface of a non-permeable substrate.

[0027] In the recording process, white ink is applied to an area on a surface that has been pretreated with the liquid to record a white image.

[0028] <8> An image recording apparatus for use in any one of <1> to <7>,

[0029] The above-mentioned image recording device includes:

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

[0031] The winding unit includes a winding device that winds the non-permeable substrate on which the white image is recorded under tension, and performs the winding process described above.

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

[0033] Invention Effects

[0034] According to one embodiment of the present invention, an image recording method and an image recording apparatus are provided, which are capable of recording white images on a non-permeable substrate and suppressing the adhesion of white images and the deflection of the non-permeable substrate when the non-permeable substrate on which the white images are recorded is wound up. Attached Figure Description

[0035] Figure 1 This is a diagram that conceptually illustrates an example of an image recording apparatus used in implementing the image recording method of the present invention. Detailed Implementation

[0036] In this invention, the numerical range represented by “~” indicates the range included by taking the values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0037] Within the numerical ranges described in this specification, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different periods. Furthermore, within the numerical ranges described in this specification, the upper or lower limit value recorded in a certain numerical range can also be replaced with the values ​​shown in the embodiments.

[0038] In this invention, when a composition contains multiple substances corresponding to each component, unless otherwise stated, the amount of each component in the composition represents the total amount of the multiple substances present in the composition.

[0039] In this invention, a combination of two or more preferred methods is a more preferred method.

[0040] In this invention, the term "process" includes not only independent processes, but also processes that can achieve the desired purpose of the process, even if they cannot be clearly distinguished from other processes.

[0041] In this invention, the term "image" refers to the ink film itself when no pretreatment liquid is used, and to the laminated film of the pretreatment liquid film and the ink film when a pretreatment liquid is used.

[0042] In this invention, "image recording" refers to the formation of an image.

[0043] The concept of "image" in this invention also includes solid images.

[0044] In this invention, the description of "applying ink to a substrate" includes applying ink directly to the surface of the substrate and applying ink directly to the surface of layer A, for example, when layer A is formed.

[0045] In this invention, unless otherwise specified, "upstream side" refers to the upstream side of the transport direction of the non-permeable substrate, and unless otherwise specified, "downstream side" refers to the downstream side of the transport direction of the non-permeable substrate.

[0046] [Image recording method]

[0047] The image recording method of the present invention (hereinafter also referred to as the "recording method") includes: a recording step, in which a white image is recorded by applying white ink containing water and white pigment to one side (hereinafter also referred to as the "front side") of a non-permeable substrate by inkjet printing; and a winding step, in which the non-permeable substrate on which the white image is recorded is wound under tension, and the other side (hereinafter also referred to as the "back side") of the non-permeable substrate is wound with the surface of the white image. 2 When the surface energy difference per unit is ΔE and the tension in N / m units is P, the value obtained by dividing ΔE by P, i.e., the ΔE / P ratio, is 0.06 to 0.60.

[0048] According to the recording method of the present invention, a white image can be recorded on a non-permeable substrate, and adhesion of the white image and deflection of the non-permeable substrate during winding are suppressed.

[0049] The reasons for achieving this effect are speculated as follows.

[0050] The reason why white images can be suppressed is speculated as follows.

[0051] mJ / m of the back side of the non-permeable substrate and the surface of the white image 2The larger the value of the surface energy difference, ΔE (hereinafter also referred to as "surface energy difference ΔE"), the more beneficial it is for suppressing the adhesion of white images. The reason 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 comes into contact with that back side after winding.

[0052] On the other hand, when winding a non-permeable substrate on which a white image is recorded, the smaller the value of the tension (i.e., P (hereinafter also referred to as "tension P") applied to the non-permeable substrate in N / m units, the more advantageous it is for suppressing the adhesion of the white image. The reason is that the smaller the tension P, the weaker the winding tightness of the non-permeable substrate. As a result, the mutual pressing force between the back side of the non-permeable substrate and the white image contacting the back side becomes weaker in the wound non-permeable substrate.

[0053] Therefore, the larger the value obtained by dividing ΔE by P, i.e., the larger the ΔE / P ratio, the more beneficial it is for suppressing the adhesion of white images.

[0054] Specifically, in the recording method of the present invention, the adhesion of white images can be suppressed by having a ΔE / P ratio of 0.06 or higher.

[0055] The reason for suppressing roll-off of non-permeable substrates is speculated as follows.

[0056] The smaller the surface energy difference ΔE, the more favorable it is for the roll-off of non-permeable substrates. The reason is that the smaller the surface energy difference ΔE, the higher the affinity between the back side of the non-permeable substrate and the white image that contacts the back side after winding, and the less likely it is to shift between the two.

[0057] On the other hand, the greater the value of tension P, the more advantageous it is for the winding of non-permeable substrates. The reason is that the greater the tension P, the tighter the non-permeable substrate is wound, and as a result, after winding, the mutual pressing force between the back side of the non-permeable substrate and the white image contacting that back side becomes stronger.

[0058] Therefore, the smaller the value obtained by dividing ΔE by P, i.e., the smaller the ΔE / P ratio, the more beneficial it is for suppressing the roll-up deviation of non-permeable substrates.

[0059] Specifically, in the recording method of the present invention, the roll-off of the non-permeable substrate can be suppressed by having a ΔE / P ratio of 0.60 or less.

[0060] <ΔE / P ratio>

[0061] As described above, the ΔE / P ratio in this 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 above 0.10, the adhesion of white images can be further suppressed.

[0064] When the ΔE / P ratio is below 0.50, the roll-off of non-permeable substrates can be further suppressed.

[0065] <Surface energy difference ΔE>

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

[0067] Here, the surface energy difference ΔE is based on

[0068] Dispersion of surface energy γ on the back side of a non-permeable substrate S d (1)

[0069] Hydrogen bonding component γ on the back surface energy of a non-permeable substrate S h (1)

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

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

[0072] It can be obtained from 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] Regarding the surface energy difference ΔE, there are no particular restrictions as long as the ΔE / P ratio falls within the range mentioned above.

[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 even more preferably 7.0 to 24.0.

[0076] <Methods for determining surface energy (hydrogen bond component and dispersed component)>

[0077] In this invention, the surface energy (hydrogen bond component and dispersion component) of the solid surface (i.e., the back side of the non-permeable substrate and the surface of the white image, respectively) refers to the value calculated by the Owens-Wendt method.

[0078] Regarding the surface energy of the white image, the same white ink as that used in the recording process is used to record the white image on a non-permeable substrate under the same conditions as in the recording process, and the measurement is performed using the non-permeable substrate with the white image recorded (hereinafter also referred to as the "image sample").

[0079] The contact angles of water and diiodomethane, as described later, were determined within 30 minutes after the image samples were prepared (i.e., after the ink had dried).

[0080] The surface of the back side of the non-permeable substrate can be measured using the back side of the non-permeable substrate itself used in the recording process.

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

[0082] As a contact angle meter, for example, it can be manufactured under the product name "DM-501" by Kyowa Interface Science Co., Ltd.

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

[0084] The Owens-Wendt method is documented in D.K. Owens, and R.C. Wendt, Journal of Applied Polymer Science Vol. 13, pp. 1741-1747, (1969).

[0085] The specific calculation method is explained below.

[0086] When a liquid is dropped onto a solid surface, the following formula holds for the parameters at the interface between the solid surface and the liquid.

[0087] Equation 1 below is known as the Young equation.

[0088] Equation 2 below is known as the Dupre equation.

[0089] Equations 3, 4 and 5 below 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] The detailed contents of each symbol in Equations 1 to 5 are as follows.

[0096] θ…the contact angle between a liquid and a solid surface

[0097] γ S …surface energy of solid surfaces

[0098] γ L …the surface energy of liquids

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

[0100] W… Adhesion work

[0101] γ S d …dispersed components of surface energy on solid surfaces

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

[0103] γ L d …dispersed components of the surface energy of a liquid

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

[0105] From Equations 1 to 5 above, we can obtain Equation 6 below.

[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 are designated 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] The detailed contents of each symbol in Equations 6A and 6B are as follows.

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

[0112] θ2…Contact angle between diiodomethane and a solid surface

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

[0114] γ L1 d …Dispersed composition of surface energy of water (21.8 mN / m)

[0115] γ L1 h …hydrogen bond component of water surface energy (51.0 mN / m)

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

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

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

[0119] Additionally, the values ​​in parentheses are those recorded in the literature.

[0120] By substituting θ1, θ2, and 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] θ1 and θ2 are the measured values ​​obtained by the above measurement method.

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

[0123] There are no particular limitations on the surface energy of the back side of the non-permeable substrate and the surface energy of the white image, as long as they meet the range of the above-mentioned ΔE / P ratio.

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

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

[0126] Hydrogen bonding component γ on the back surface energy of a non-permeable substrateS h For example, 0mJ / m 2 ~3.0mJ / m 2 .

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

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

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

[0130] <Tension P>

[0131] In this invention, tension P (i.e., tension expressed in N / m when winding a non-permeable substrate) refers to the tension of the non-permeable substrate immediately in front of the winding device (specifically, the area within 1m of the winding device) when winding a non-permeable substrate on which a white image is recorded (hereinafter, also referred to as "tension P at the winding section").

[0132] In this invention, tension P (unit: N / m) refers to the value measured by a tension meter.

[0133] Regarding the tension P, there are no particular restrictions as long as the ΔE / P ratio falls within the range mentioned above.

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

[0135] In the recording method of the present invention, tension may also be applied to the region (e.g., the region to which ink is applied) on the upstream side of the non-permeable substrate more than 1 m from the take-up portion.

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

[0137] <Record Process>

[0138] The recording method of the present invention includes a recording step of applying white ink containing water and white pigment to the front side of a non-permeable substrate by inkjet printing to record a white image.

[0139] (Non-permeable substrate)

[0140] In this invention, the non-permeability of the non-permeable substrate refers to the property that the water absorption rate after 24 hours is less than 2.5%, as measured according to ASTM D570-98 (2018). Here, the unit "%" for water absorption rate is based on mass. The aforementioned water absorption rate is preferably less than 1.0%, more preferably less than 0.5%.

[0141] Materials that can be used as non-permeable substrates include, for example, 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 non-permeable substrate is preferably made of resin. That is, the non-permeable substrate is preferably a resin substrate.

[0143] From a general perspective, the preferred materials for non-permeable substrates are polypropylene, polyethylene, polyethylene terephthalate, nylon, acrylic resin, or polyvinyl chloride.

[0144] The shape of the non-permeable substrate is preferably sheet (film) or plate. Examples of non-permeable substrates with this 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] As a non-permeable substrate made of resin, examples include resin sheets (resin films), and more specifically, flexible packaging materials for packaged foods and floor guide panels in large retail stores.

[0146] In addition to sheet-like (film-like) or plate-like non-permeable substrates, textiles (fabrics) and non-woven fabrics formed from non-permeable fibers can also be cited as examples of non-permeable substrates.

[0147] The thickness of the non-permeable substrate is preferably 0.1 μm to 1,000 μm, more preferably 0.1 μm to 800 μm, and even more preferably 1 μm to 500 μm.

[0148] Surface treatment can be applied to at least one of the front and back sides of a non-permeable substrate.

[0149] Examples of surface treatments include corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., UV treatment), but are not limited to these. Corona treatment can be performed, for example, using a corona master (product name "PS-10S", manufactured by Shinko Electric & Instrumentation Co., Ltd.).

[0150] The surface treatment conditions can be selected appropriately based on the type of non-permeable substrate.

[0151] Furthermore, the surface energy of the back side of the non-permeable substrate can be adjusted by the presence or absence of surface treatment on the back side of the non-permeable substrate and the conditions under which the surface treatment is performed, thereby adjusting ΔE and the ΔE / P ratio.

[0152] Non-permeable substrates can be transparent non-permeable substrates.

[0153] Here, transparency means that the transmittance of visible light with wavelengths of 400nm to 700nm is 80% or more (preferably 90% or more).

[0154] When the non-permeable substrate is a transparent non-permeable substrate, the image can be easily visually identified from the back side of the non-permeable substrate.

[0155] For example, when the non-permeable substrate is a transparent non-permeable substrate, and when recording is performed on the non-permeable substrate in a manner in which patterned images such as characters and graphics, i.e. colored images, and white images (e.g., solid images) as background images are arranged sequentially when viewed from the non-permeable substrate side, it is easy to visually identify the colored images (e.g., patterned images such as characters and graphics) with white images (e.g., solid images) as backgrounds through the non-permeable substrate from the image back side of the non-permeable substrate.

[0156] In this invention, "coloring" in coloring inks and coloring pigments refers to color (e.g., 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 side of a non-porous substrate using an inkjet printer to record a white image.

[0159] White ink contains water and white pigment.

[0160] The following is an explanation of the white ink.

[0161] -water-

[0162] White ink contains water.

[0163] The water content relative to the total amount of white ink is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 50% by mass or more.

[0164] The upper limit of the water content relative to the total amount of white ink can be appropriately determined based on the content of other components, 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 inorganic pigments that can be used as white pigments include titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, zinc oxide, zinc sulfide, mica, talc, and pearl.

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

[0169] From the viewpoint of concealment, the average primary particle size of the white pigment is preferably 150 nm or more, more preferably 200 nm or more. Furthermore, from the viewpoint of ink ejectibility, the average primary particle size of the white pigment is preferably 400 nm or less, more preferably 350 nm or less.

[0170] Here, concealment refers to the ability to cover a substrate that forms a white image (e.g., the front side of a non-permeable substrate or a colored image recorded on the front side earlier than the white image) with a white image.

[0171] In this invention, the average primary particle size of the white pigment is a value measured using a transmission electron microscope (TEM). Specifically, it is the value obtained by selecting any 50 white pigments present in the field of view observed by the TEM, measuring the primary particle size of each of the 50 pigments, and averaging the results. The transmission electron microscope is the JEOL Ltd. 1200EX transmission electron microscope.

[0172] From the viewpoint of image density and ejectibility, when the ink contains white pigment, the content of white pigment relative to the total amount of ink is preferably 2% to 25% by mass, more preferably 5% to 25% by mass, and even more preferably 10% to 20% by mass.

[0173] -Resin-

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

[0175] The resin in white ink contributes to the film-forming properties of white ink (i.e., the ability to form a 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 even more preferably 5,000 to 100,000.

[0177] In this invention, unless otherwise stated, weight-average molecular weight (Mw) refers to the value determined by gel permeation chromatography (GPC).

[0178] In the determination by gel permeation chromatography (GPC), the apparatus used was an HLC-8020GPC (TOSOH CORPORATION), with three TSKgel Super Multipore HZ-H columns (4.6 mm ID × 15 cm, TOSOH CORPORATION) used as the column and THF (tetrahydrofuran) as the eluent. The determination conditions were set as follows: sample concentration 0.45% by mass, flow rate 0.35 ml / min, sample injection volume 10 μl, and determination temperature 40 °C, using an RI detector.

[0179] The calibration curves were prepared using eight samples from TOSOH Corporation's "Standard Samples TSK standard, polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0180] As a resin, pigment dispersion resins, which are used as pigment dispersants, can be cited as an example.

[0181] As a resin, resin particles can also be cited as an example.

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

[0183] Pigment dispersion resin is a resin that has the function of dispersing pigments.

[0184] Pigment dispersion resins can be random copolymers or block copolymers.

[0185] Pigment dispersion resins can have cross-linked structures.

[0186] Inks can be prepared using pigment dispersions containing pigments and pigment dispersing resins.

[0187] Regarding pigment dispersion resins, for example, known polymer dispersants such as those described in paragraphs 0029 to 0106 of International Publication No. 2021 / 221069 can be used.

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

[0189] When the white ink contains pigment dispersion resin, the content of pigment dispersion resin relative to the total amount of ink 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.

[0190] White ink may contain at least one type of resin particle.

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

[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 this invention, the volume average particle size refers to the value measured using a laser diffraction / scattering particle size analyzer.

[0194] As a measuring device, an example is the particle size distribution measuring device "Microtrac MT-3300II" (manufactured by Nikkiso Co., Ltd.).

[0195] The resin particles are preferably selected from at least one of the following groups: acrylic resin particles, ester resin particles, mixtures 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 this 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, derivatives of acrylic acid (e.g., acrylates), methacrylic acid, and derivatives of methacrylic acid (e.g., methacrylates).

[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, and more preferably 50°C to 150°C.

[0198] Here, the glass transition temperature (Tg) of the resin particles is determined by actual measurement. For the method of determining Tg, please refer to paragraph 0111 of Japanese Patent Application Publication No. 2015-25076.

[0199] Regarding resin particles, for example, see paragraphs 0038 to 0114 of International Publication No. 2021 / 192720 and paragraphs 0109 to 0120 of Japanese Patent Application Publication No. 2015-25076.

[0200] When the white ink contains resin particles, the content of resin particles in the white ink relative to the total amount of 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.

[0201] -Water-soluble organic solvents-

[0202] White inks preferably contain at least one water-soluble organic solvent.

[0203] This ensures the stability of the inkjet output.

[0204] The water-soluble organic solvent contained in white ink can be one type or two or more types.

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

[0206] There is no limitation on the types of water-soluble organic solvents that can be contained in white inks. For example, the following can be cited:

[0207] Monools with 1 to 4 carbon atoms;

[0208] 1,2-Ethylene glycol (also known as ethylene glycol), 1,3-propanediol (also known as propylene glycol), 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-buten-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 glycerol, 1,2,6-hexanetriol, and trimethylolpropane;

[0210] Ethylene glycol monoalkyl ethers, propylene glycol monoalkyl ethers, and other alkylene glycol monoalkyl ethers;

[0211] Diethylene glycol, triethylene glycol, tetraethylene glycol, pentylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol, and other polyalkylene glycols;

[0212] Diethylene glycol monoalkyl ethers, triethylene glycol monoalkyl ethers, tripropylene glycol monoalkyl ethers, polyoxypropylene glycerol ethers, and other polyalkylene glycol ethers; and

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

[0214] wait.

[0215] From the viewpoint of ejection 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 water-soluble organic solvent relative to the total amount of white ink is preferably 10% to 40% by mass, more preferably 15% to 30% by mass.

[0217] -surfactant-

[0218] White ink may contain at least one surfactant.

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

[0220] As a preferred surfactant, acetylene glycol-based surfactants, which are a type of nonionic surfactant, can be cited as an example.

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

[0222] Examples of acetylene glycol surfactants include:

[0223] Polyalkylene adducts (preferably polyethylene oxide adducts) of 2,4,7,9-tetramethyl-5-decyn-4,7-diol

[0224] Polyalkylene oxide adducts (preferably polyethylene oxide adducts) of 3,6-dimethyl-4-octyne-3,6-diol

[0225] Polyalkylene adducts (preferably polyethylene oxide adducts) of 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol

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

[0227] wait.

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

[0229] Commercially available acetylene glycol surfactants are also supplied by companies such as The Dow Chemical Company and General Aniline & Film Corp.

[0230] Examples of surfactants include compounds listed on pages 37-38 of Japanese Patent Application Publication No. 59-157636 and Research Disclosure No. 308119 (1989). Furthermore, examples include fluorinated (fluoroalkyl) surfactants and silicone surfactants described in Japanese Patent Application Publication Nos. 2003-322926, 2004-325707, and 2004-309806.

[0231] When white ink contains surfactants, the surfactant content in the white ink can be appropriately adjusted by taking into account the surface energy of the white image to be recorded.

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

[0233] -Other ingredients-

[0234] White ink may contain other ingredients besides those mentioned above.

[0235] Other ingredients include, for example, known additives such as silica compounds (e.g., silica compounds described in paragraphs 0058 to 0075 of Japanese Patent No. 5430316), urea, urea derivatives, waxes, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, antifungal agents, pH adjusters, defoamers, viscosity modifiers, dispersion stabilizers, and chelating agents.

[0236] -Physical properties-

[0237] From the viewpoint of improving ejection stability, the pH (25°C) of the white ink is preferably 7 to 10, more preferably 7.5 to 9.5. The pH of the ink can be measured using the same method as that used for the pH of the pretreatment solution.

[0238] The viscosity (at 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, more preferably 2 mPa·s to 15 mPa·s, and even more preferably 3 mPa·s to 10 mPa·s.

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

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

[0241] Surface tension was measured using a surface tension meter at 25°C, for example, using an automated surface tension meter (product name "CBVP-Z") manufactured by Kyowa Interface Science Co., Ltd., and measured by the plate method.

[0242] (Applying white ink)

[0243] In the recording process, white ink is applied to the front side of a non-porous substrate using an inkjet printer to record a white image.

[0244] There are no particular restrictions on the ejection method of white ink based on inkjet technology. It can be any of the known methods, such as charge control method that uses electrostatic attraction to eject ink, on-demand inkjet method (pressure pulse method) that uses the vibration pressure of piezoelectric elements, acoustic inkjet method that converts electrical signals into sound beams to irradiate ink and uses radiation pressure to eject ink, and thermal inkjet method (Bubble Jet (registered trademark)) that heats ink to form bubbles and uses the resulting pressure.

[0245] As an inkjet recording method, the inkjet recording method described in Japanese Patent Application Publication No. 54-59936 can be used particularly effectively. In this inkjet recording method, the ink undergoes a rapid volume change under the action of heat energy, and the ink is ejected from the nozzle by the force generated by this change in state. As an inkjet recording method, the method described in paragraphs 0093 to 0105 of Japanese Patent Application Publication No. 2003-306623 can also be used.

[0246] Applying white ink to a non-permeable substrate using an inkjet recording method by ejecting white ink from the nozzle of an inkjet head.

[0247] As inkjet heads, there are the following methods: a reciprocating method, in which a short strip-shaped serial head scans and records simultaneously along the width of the medium being recorded; and a linear method, 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 medium being recorded.

[0248] In the inline method, by scanning the recording medium along a direction intersecting the arrangement direction of the recording elements, images can be recorded across the entire surface of the recording medium. The inline method eliminates the need for a transport system such as a carriage, which is required for scanning the short, strip-shaped inkjet head as in the reciprocating method. Furthermore, compared to the reciprocating method, the inline method eliminates the need for carriage movement and complex scanning control of the recording medium; only the recording medium needs to be moved. Therefore, the linear method achieves higher image recording speeds compared to the reciprocating method.

[0249] Applying white ink is preferably done using an inkjet head with a resolution of 300 dpi or higher (more preferably 600 dpi or higher, and even more preferably 800 dpi or higher). Here, dpi is an abbreviation for dots per inch, and 1 inch is 2.54 cm.

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

[0251] (Drying of white ink)

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

[0253] There are no particular limitations on the drying method for white inks. Examples include infrared (IR) drying, warm air drying (e.g., dryer), and heating drying based on heating devices (e.g., heater, hot plate, furnace).

[0254] As a method of heating and drying, it is also possible to combine two or more of these methods.

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

[0256] The heating temperature for drying white ink is preferably 35°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher.

[0257] There is no particular limit to the upper limit of the heating temperature, but it is preferably 100°C, and more preferably 90°C.

[0258] There is no particular limitation on the heating time for drying white ink, but it is preferably 1 to 180 seconds, more preferably 1 to 120 seconds, and even more preferably 1 to 60 seconds.

[0259] (Record of a colored image)

[0260] The recording process may also include recording a colored image by applying a coloring ink containing water and coloring pigments to the front side of an impermeable substrate using an inkjet method.

[0261] According to this method, it is possible to record multicolor images containing white and colored images on the front side of a non-permeable substrate.

[0262] In this method, only one type of coloring ink can be used to record only one type of colored image (e.g., one of cyan, magenta, yellow and black images), or two or more types of coloring ink can be used to record two or more colored images (e.g., two or more of cyan, magenta, yellow and black images).

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

[0264] As a method of recording a colored image in front of a white image, an example is a method in which a colored image (e.g., a patterned image such as characters or graphics) is positioned between the front side of a non-porous substrate and a white image (e.g., a solid image). This method allows for visual identification of a colored image (e.g., a patterned image such as characters or graphics) against a white image (e.g., a solid image) through the non-porous substrate from the back side of the substrate.

[0265] As a method of recording a colored image after a white image, an example is a method in which a colored image (e.g., a patterned image of characters, graphics, etc.) is disposed on a white image (e.g., a solid image). This method is a way of visually recognizing a colored image (e.g., a patterned image of characters, graphics, etc.) on an upper layer with a white image (e.g., a solid image) on the lower layer as a background from the front side of a non-permeable substrate.

[0266] From the viewpoint of more effectively suppressing the adhesion of multiple color images containing white and colored images, it is preferable to record the colored image before the white image and place it between the front side of the non-porous substrate and the white image.

[0267] When this method is applied, compared to the method where the colored image is recorded after the white image and the colored image is placed on the white image, the contact area between the white image and the back of the non-permeable substrate becomes larger, thus more effectively suppressing the adhesion of multiple colored images.

[0268] -Coloring Inks-

[0269] Coloring inks used to record colored images contain water and coloring pigments (i.e., colored or black pigments).

[0270] Regarding the preferred method for coloring ink, except for the type of pigment, it is the same as the preferred method for white ink described above.

[0271] Coloring pigments can be either commercially available organic or inorganic pigments.

[0272] As coloring pigments, examples include those described in Seishiro Itō's "Encyclopedia of Pigments" (published in 2000), W. Herbst and K. Hunger's "Industrial Organic Pigments," Japanese Patent Application Publication Nos. 2002-12607, 2002-188025, 2003-26978, and 2003-342503.

[0273] Furthermore, the coloring pigment can be a water-insoluble pigment that can be dispersed in water by a dispersant, or it can be a self-dispersing pigment.

[0274] Self-dispersible pigments are pigments that can be dispersed in water even without the use of a dispersant.

[0275] Self-dispersible pigments are, for example, compounds selected from the group consisting of hydrophilic groups such as carbonyl, hydroxyl, carboxyl, sulfonyl, and phosphate groups and their salts, which are directly or chemically bonded to the surface of the pigment via other groups.

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

[0277] <Pretreatment solution application process>

[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 side of a non-permeable substrate (hereinafter also referred to as the "pretreatment liquid application step") before the recording step.

[0279] In this case, during the recording process, the aforementioned white ink is applied to the area on the front side that has been treated with the pretreatment liquid to record the aforementioned white image.

[0280] According to the method including the pretreatment liquid application process, the components of white ink are coagulated by the action of the coagulant pre-applied to the front, which is beneficial to the image quality of white images.

[0281] In a method that includes a pretreatment liquid application process, in addition to a white image, the aforementioned colored image can also be recorded.

[0282] In this case, the aforementioned coloring ink is applied to the area on the front side that has been treated with the pretreatment liquid to record the aforementioned colored image. As a result, the components of the coloring ink are agglomerated by the action of the coagulant, thus improving the image quality and other aspects of the colored image.

[0283] As described above, the colored image can be recorded on the upper side of the white image (the side away from the non-porous substrate) or on the lower side of the white image (the side closer to the non-porous substrate; that is, between the front of the non-porous substrate and the white image).

[0284] (Pretreatment solution)

[0285] The pretreatment solution contains water and coagulant.

[0286] -water-

[0287] The pretreatment solution contains water.

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

[0289] While the upper limit of water content depends on the amount of other components, it is preferably 90% by mass or less, and more preferably 80% by mass or less, relative to the total amount of pretreatment liquid.

[0290] -Flocculant-

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

[0292] The coagulant in the pretreatment solution causes the components in the ink to coagulate on a non-permeable substrate. This improves image quality.

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

[0294] As a coagulant, the coagulant described in paragraphs 0122 to 0130 of International Publication No. 2020 / 195360 is preferred.

[0295] The preferred methods for organic acids, polyvalent metal compounds, metal complexes, and cationic polymers that can be used as coagulants are described below.

[0296] --Organic acids--

[0297] Organic acids can be exemplified by organic compounds having acidic groups.

[0298] Examples of acidic groups include phosphate, phosphonic acid, hypophosphonic acid, sulfate, sulfonic acid, sulfinic acid, and carboxyl groups.

[0299] From the perspective of ink coagulation speed, the acidic group is preferably a phosphate group or a carboxyl group, and more preferably a carboxyl group.

[0300] Preferably, at least a portion of the acidic groups dissociate in the pretreatment solution.

[0301] Examples of organic compounds containing a carboxyl group include (meth)acrylic acid, poly(meth)acrylic acid, acetic acid, formic acid, benzoic acid, ethylene glycol, 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, pyrrolidone carboxylic acid, pyranone carboxylic acid, pyrrolic carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, and nicotinic acid.

[0302] From the viewpoint of ink coagulation speed, organic compounds with carboxyl groups are preferably carboxylic acids with a valence of 2 or higher (hereinafter also referred to as polycarboxylic acids), and more preferably dicarboxylic acids.

[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 is preferably low in pKa (e.g., 1.0 to 5.0). Thus, the surface charge of particles such as pigments and resin particles in inks that are dispersed and stabilized by weakly acidic functional groups such as carboxyl groups is reduced by contact with organic acids with lower pKa, thereby reducing dispersion stability.

[0305] The organic acid is preferably low in pKa, highly soluble in water, and has a valence of 2 or higher. Furthermore, the organic acid is more preferably high in the pH region where it has a lower pKa than the functional group (e.g., carboxyl group) that disperses and stabilizes the particles in the ink.

[0306] --Polyvalent metal compounds--

[0307] As examples of polyvalent metal compounds, polyvalent metal salts can be cited.

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

[0309] As a polyvalent metal salt of an organic acid, the polyvalent metal salts of the above-mentioned organic acids (e.g., formic acid, acetic acid, benzoic acid, etc.) are preferred.

[0310] As a polyvalent metal salt of inorganic acid, polyvalent metal salts of nitrate, hydrochloric acid, or thiocyanate are preferred.

[0311] Examples of polyvalent metal salts include salts of alkaline earth metals (e.g., magnesium, calcium) from Group 2 of the periodic table, salts of transition metals (e.g., lanthanum) from Group 3 of the periodic table, salts of metals (e.g., aluminum) from Group 13 of the periodic table, and salts of lanthanides (e.g., neodymium).

[0312] As a multivalent metal salt, calcium salt, magnesium salt, or aluminum salt are preferred, with calcium salt or magnesium salt being more preferred.

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

[0314] Preferably, at least a portion of the polyvalent metal compound dissociates into polyvalent metal ions and counterions in the pretreatment solution.

[0315] --Metal complex--

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

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

[0318] Metal complexes are commercially available. Various organic ligands, especially multidentate ligands capable of forming metal chelating catalysts, are commercially available. Therefore, metal complexes can be prepared by combining commercially available organic ligands with metals.

[0319] --Catonic polymers--

[0320] The cationic polymer is preferably a homopolymer, copolymer, or condensation polymer of a cationic monomer having primary to tertiary amino or quaternary ammonium groups. As a cationic polymer, it can be used in either the form of a water-soluble polymer or a water-insoluble polymer (i.e., latex particles).

[0321] Examples of cationic polymers include polyvinylpyridine salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimazoles, polyethyleneimine, polybiguanidines, polyguanidines, polyallylamines, and their derivatives.

[0322] From the viewpoint of the viscosity of the pretreatment solution, a low weight-average molecular weight of the cationic polymer is preferred. When the pretreatment solution is applied to the resin substrate by inkjet printing, a weight-average molecular weight of 1,000 to 500,000 is preferred, more preferably 1,500 to 200,000, and even more preferably 2,000 to 100,000. A weight-average molecular weight of 1,000 or higher is advantageous from the viewpoint of coagulation rate. A weight-average molecular weight of 500,000 or lower is advantageous from the viewpoint of ejection reliability. However, this is not a limitation when the pretreatment solution is applied to the resin substrate by methods other than inkjet printing.

[0323] The content of coagulant in the pretreatment liquid relative to the total amount of the pretreatment liquid is preferably 0.1% to 40% by mass, more preferably 0.1% to 30% by mass, even more preferably 1% to 20% by mass, and even more preferably 1% to 10% by mass.

[0324] -Resin-

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

[0326] The resin in the pretreatment solution contributes to the film-forming properties of the pretreatment solution (i.e., the film-forming properties based on the pretreatment solution).

[0327] As the resin in the pretreatment solution, the same resin (e.g., resin particles) as the resin in the ink can be used.

[0328] There are no particular restrictions on the resin content in the pretreatment solution.

[0329] The resin content relative to the total amount of the pretreatment solution is preferably 0.5% to 30% by mass, more preferably 1% to 20% by mass, and especially preferably 1% to 15% by mass.

[0330] -Water-soluble organic solvents-

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

[0332] As a water-soluble organic solvent in the pretreatment solution, the same solvent that can be used as the water-soluble organic solvent that the ink may contain can be used.

[0333] -additive-

[0334] Inks may contain additives such as surfactants, water-soluble resins, co-sensitizers, UV absorbers, antioxidants, anti-fading agents, conductive salts, and alkaline compounds, depending on the requirements.

[0335] -Physical properties-

[0336] The pH of the pretreatment solution is preferably 2.0 to 7.0, more preferably 2.0 to 4.0. The pH of the pretreatment solution is determined by the same method as that used for the pH of the ink.

[0337] From the viewpoint of the coatability of the pretreatment solution, the viscosity of the pretreatment solution is preferably 0.5 mPa·s to 10 mPa·s, more preferably 1 mPa·s to 5 mPa·s. The viscosity is the value measured using a viscometer at 25°C. The viscosity of the pretreatment solution is measured using 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 even more preferably 30 mN / m to 45 mN / m. The surface tension is a value measured at 25°C. The surface tension of the pretreatment liquid is measured using the same method as that used for the surface tension of the ink.

[0339] (Method for applying pretreatment solution)

[0340] The method of applying the pretreatment solution is not particularly limited, and well-known methods such as coating, immersion, and inkjet recording can be cited.

[0341] As a coating method, known coating methods include those using bar coaters, die coaters, air knife coaters, blade coaters, bar coaters, knife coaters, extrusion coaters, and reverse roller coaters.

[0342] (Drying of the pretreatment solution)

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

[0344] There are no particular limitations on the drying method used as a pretreatment liquid; for example, the same method exemplified as the drying method for white ink can be applied.

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

[0346] <Winding Process>

[0347] The recording method of the present invention includes a winding process of winding a non-permeable substrate on which a white image is recorded under tension P.

[0348] Regarding the winding process, there are no particular limitations, and it can be carried out using a known winding device that includes a winding core.

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

[0350] <Image Recording Device>

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

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

[0353] The winding unit includes a winding device that winds the non-permeable substrate on which the white image is recorded under tension, and performs the winding process described above.

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

[0355] The image recording apparatus described above can achieve the same effect as the image recording method of the present invention described above.

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

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

[0358] like Figure 1 As shown, the inkjet recording apparatus involved in this example is an example of an inkjet recording apparatus equipped with a transport mechanism for transporting resin substrate in a roll-to-roll manner. It is an apparatus in which a non-permeable substrate A1, which is rolled into a roll shape, is unwound by an unwinding device R1. The unwound non-permeable substrate A1 is transported in the direction of the arrow under tension and passes sequentially through a pretreatment liquid application device P1, a pretreatment liquid drying zone DP1, a first inkjet head IJ1, a first drying zone D1, a second inkjet head IJ2, and a drying zone D2. Finally, it is wound up by a winding device R2 including a core under tension P.

[0359] The non-permeable substrate A1 is conveyed under tension and wound up under tension P. The tension during conveying can be the same as the tension P during winding, or it can be a different tension. Furthermore, the tension can vary depending on the position of the conveying direction, or it can be the same tension.

[0360] The image recording apparatus described in this example may have a tension adjustment mechanism for adjusting the tension on a non-permeable substrate.

[0361] Examples of tension adjustment mechanisms include:

[0362] A powder brake is installed in the unwinding device R1 and / or the winding device R2.

[0363] Tension adjustment rollers (dancer rollers) installed along the conveying path; and

[0364] Control devices that control tension by adjusting various conditions of the image recording device (e.g., tension controllers).

[0365] Furthermore, the image recording device involved in this example may be equipped with a tension measuring mechanism (e.g., a tension meter) for measuring the tension of a non-permeable substrate.

[0366] In addition, due to Figure 1 This is a conceptual diagram, thus simplifying the transport path of the non-permeable substrate A1, and illustrating it as if the non-permeable substrate A1 is transported in one direction. However, in reality, it goes without saying that the transport path of the non-permeable substrate A1 can be curved.

[0367] As a conveying method for non-permeable substrate A1, various web conveying methods such as cylinders and rolls can be appropriately selected.

[0368] Relative to the unwinding device R1 used to unwind the non-permeable substrate A1, a pretreatment liquid application device P1, a pretreatment liquid drying zone DP1, a first inkjet head IJ1, a first drying zone D1, a second inkjet head IJ2, and a drying zone D2 are sequentially arranged on the downstream side of the conveying direction of the non-permeable substrate A1, starting from the upstream side of the conveying direction of the non-permeable substrate A1.

[0369] The pretreatment liquid is applied by the pretreatment liquid application device P1, the first inkjet head IJ1 and the second inkjet head IJ2 respectively.

[0370] At this time, at least one of the following can be performed: heating and drying of the pretreatment liquid in the pretreatment liquid drying zone DP1, heating and drying of the first ink in the first drying zone D1, and heating and drying of the second ink in the second drying zone D2.

[0371] In the first drying zone D1, in addition to the heating and drying of the first ink, the pretreatment liquid can also be heated and dried.

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

[0373] Furthermore, if the resin substrate is passed through each drying zone at room temperature, the heating and drying process can be omitted.

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

[0375] Upstream of the pretreatment liquid application device P1, a surface treatment section (not shown) may be provided for performing surface treatment (preferably corona treatment) on at least one of the front and back surfaces of the non-permeable substrate A1.

[0376] Furthermore, a cooling zone may be provided downstream of the second drying zone D2 to cool the recorded multicolor images (i.e., multicolor images including white images and colored images).

[0377] The first inkjet head IJ1 and the second inkjet head IJ2 can be reciprocating inkjet heads, but from the viewpoint of high-speed image recording, it is preferable to have a row head with multiple nozzles arranged in the width direction of the non-permeable substrate A1 in the shape of a long strip film.

[0378] The first inkjet head IJ1 and the second inkjet head IJ2 can be either a single unit or multiple units.

[0379] As an example of the combination of the first inkjet head IJ1 and the second inkjet head IJ2, the following combination can be given: the first inkjet head IJ1 is four inkjet heads corresponding to the four colors of cyan, magenta, yellow and black (note: these four inkjet heads are arranged along the transport 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 given: the first inkjet head IJ1 is one inkjet head corresponding to white (i.e., white), and the second inkjet head IJ2 is four inkjet heads corresponding to the four colors of cyan, magenta, yellow and black (Note: these four inkjet heads are arranged along the transport direction of the resin substrate).

[0381] In inkjet recording using the image recording device described in this example,

[0382] First, the non-permeable substrate A1, which is wound into a roll shape, is unwound by the unwinding device R1.

[0383] The released non-permeable substrate A1 is conveyed along the direction of the arrow in the block under tension.

[0384] The pretreatment liquid is applied to the non-permeable substrate A1 using the pretreatment liquid application device P1.

[0385] Next, the pretreatment solution is dried at the pretreatment solution drying zone DP1 as needed.

[0386] Next, the first ink (i.e., either colored ink or white ink) is applied through the first inkjet head IJ1.

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

[0388] Next, the second ink (i.e., the other of the colored ink and white ink) is applied through the second inkjet head IJ2.

[0389] Next, the second ink is dried in the second drying zone D2 as needed.

[0390] Thus, a multicolor image can be obtained, which includes a first image (i.e., either the colored image or the white image) derived from the first ink and a second image (i.e., the other of the colored image or the white image) derived from the second ink.

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

[0392] In this example, the surface energy difference ΔE (mJ / m²) between the back surface of the non-permeable substrate A1 and the surface of the white image is... 2 The value obtained by dividing the tension P (N / m) of the winding device R2 before it is connected is ΔE / P, which is adjusted to 0.06 to 0.60.

[0393] Therefore, in the non-permeable substrate A1 after winding, it is possible to suppress roll deviation and adhesion of white images.

[0394] In this case, when 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 positioned between the non-porous substrate and the white image, the white image becomes the upper layer, and therefore the entire surface of the white image contacts the back side of the non-porous substrate. As a result, the contact area between the white image and the back side of the non-porous substrate becomes larger, and therefore, the adhesion suppression effect of the multi-colored images is superior compared to the case where the colored image is the upper layer.

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

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

[0397] Example

[0398] The following are embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0399] <Preparation of Pretreatment Solution>

[0400] The pretreatment solution was prepared by mixing the ingredients shown below.

[0401] -Composition of the 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 weight

[0410] Triisopropanolamine (pH adjuster)

[0411] …0.2% by mass

[0412] • BYK024 (BYK Corporation) [Defoamer]

[0413] …0.01% by mass

[0414] Ultrapure water

[0415] …the pretreatment solution becomes 100% by mass of the remainder.

[0416] <Preparation of White Ink W1>

[0417] White ink W1 was prepared by mixing the following ingredients.

[0418] -Composition of white ink W1-

[0419] The following white pigment dispersion

[0420] …12% by mass, based on the content of white pigment.

[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-based 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] …based on the content of colloidal silica particles, it is 0.1% by mass.

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

[0436] …based on the content of styrene-acrylic resin particles, it is 5.0% by mass.

[0437] ·water

[0438] …the white ink constitutes a 100% mass surplus.

[0439] (Preparation of white pigment dispersion)

[0440] -Synthesis of Pigment Dispersant P1-

[0441] Add 965 g of dipropylene glycol to a 5000 mL three-necked flask equipped with a stirrer and cooling tube, and heat to 85 °C under a nitrogen atmosphere.

[0442] The following were 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 peroxide-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 additions were complete, the mixture was allowed to react for an additional 2 hours. 1 H-NMR confirmed the disappearance of the monomer.

[0446] The resulting reaction solution was heated to 70°C, and 248.02 g of a 50% (w / w) potassium hydroxide aqueous solution was added. Then, 107.48 g of dipropylene glycol and 75.52 g of pure water were added and the mixture was stirred to obtain a 37% (w / w) solution of the random polymer. This random polymer was used as pigment dispersant P1.

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

[0448] Preparation of white pigment dispersion-

[0449] Pigment dispersant P1 (150 parts by mass) was dissolved in water to prepare a polymer solution with a concentration of 25% by mass of pigment dispersant P1.

[0450] A mixture was prepared by mixing 96 parts by mass of the above 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. A potassium hydroxide aqueous solution was added to the obtained mixture to adjust the pH to 8.7 after neutralization.

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

[0452] Next, the obtained white pigment dispersion (uncrosslinked dispersion) PD1 was ultrafiltered using an ultrafiltration apparatus (cross-flow ultrafilter (UF), manufactured by Sartorius) at a flow rate of 600 mL / min for the influent of deion-exchanged water. The liquid temperature was maintained at 25°C, and three ultrafiltration cycles were performed, with each cycle consisting of one times the volume of the prepared liquid. Deion-exchanged water was then added to the ultrafiltered liquid to obtain an ultrafiltered dispersion with a white pigment concentration of 45% by mass and a pigment dispersant concentration of 3.6% by mass P1.

[0453] Relative to 136 parts by mass of the ultrafiltration dispersion, 1.35 parts by mass of trimethylolpropane polyglycidyl ether (product name "Denacol EX-321", manufactured by Nagase ChemteX Corporation) as a crosslinking agent and 14.5 parts by mass of boric acid aqueous solution (boric acid concentration: 4% by mass) were added. After reacting at 70°C for 6 hours, the mixture was cooled to 25°C. This process crosslinked pigment dispersant P1 in the dispersion to form pigment dispersant P1a as a crosslinking polymer dispersant, resulting in a white pigment dispersion (crosslinked dispersion) containing white pigment dispersed in pigment dispersant P1a.

[0454] Ion-exchanged water was added to the obtained crosslinked dispersion to achieve a pigment concentration of 15% by mass. The crosslinked dispersion with added ion-exchanged water was then flowed at a flow rate of 600 mL per minute into an ultrafiltration apparatus (cross-flow ultrafiltration (UF), manufactured by Sartorius) equipped with a polyethersulfone (PESU) membrane (micropore size: 0.1 μm). The liquid temperature was adjusted to 25°C, and ultrafiltration was performed three times, with each pass consisting of one volume fraction of the produced liquid. Next, ion-exchanged water was added to achieve a white pigment concentration of 45% by mass. This yielded a white pigment dispersion.

[0455] The pigment dispersant P1a contained in the white pigment dispersion has an acid value of 144 mg KOH / g. Furthermore, the concentration of pigment dispersant P1a is 3.6% by mass.

[0456] <White ink W2~W7>

[0457] The composition of the ink was changed as shown in Table 1 below. Otherwise, white inks W2 to W7 were prepared in the same manner as white ink W1.

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

[0459] In addition, empty columns in Table 1 indicate that the corresponding ingredients are not present.

[0460] <Preparation of Cyan Ink C1>

[0461] The composition of the ink was changed as shown in Table 1 below. Otherwise, cyan ink C1 was prepared in the same manner as white ink W1.

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

[0463] [Table 1]

[0464]

[0465] -Detailed information on the ingredients in Table 1-

[0466] • White pigment…the white pigment in the aforementioned white pigment dispersion

[0467] • Cyan pigment… Cyan pigment in APD4000 Cyan (manufactured by Fujifilm ImagingColorants 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…A silicone surfactant manufactured by BYK Corporation.

[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 based on solid components (colloidal silica particles).

[0476] • SuperFlex…SuperFlex 460. An aqueous dispersion of urethane resin particles manufactured by DKS Co., Ltd. The contents in Table 1 are based on solids (resin particles).

[0477] The contents listed in Table 1 for the aqueous dispersion of styrene-acrylic resin particles manufactured by Covestro Coating Resins are based on solids (resin particles).

[0478] <Preparation of Image Recording Device>

[0479] As an image recording device for evaluation, the one described in the aforementioned example was prepared. Figure 1 The image recording device shown.

[0480] A concave plate coating machine was used as the pretreatment liquid application device P1.

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

[0482] The IJ1, the first inkjet head, is equipped with a cyan inkjet head.

[0483] The IJ2 is equipped with a white inkjet head as the second inkjet head.

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

[0485] • Inkjet head: Uses a 1200dpi (dots per inch, 1 inch is 2.54cm) / 20-inch width piezo full line head (total number of nozzles 2048).

[0486] • Ink drop volume: Set to 2.0 pL.

[0487] • Drive frequency: Set to 30kHz.

[0488] The drying method for both drying zone D1 and drying zone D2 is warm air drying.

[0489] An air-cooled 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) is assembled inside the inkjet recording device. This tension controller controls the tension applied to the non-permeable substrate (especially the tension P at the take-up section, as described later) during inkjet recording.

[0491] <Preparation of Non-Opermeable Substrates>

[0492] The following non-permeable substrates were prepared as non-permeable substrates for evaluation.

[0493] In the embodiments and comparative examples described below, any one of the following non-permeable substrates was used (see Table 2 for details).

[0494] • P2161… PYLEN FILM-OT OPP film manufactured by Toyobo Co., Ltd. Thickness is 25μm or 40μm.

[0495] • PET…Futamura Chemical Co., Ltd. manufactures PET films called “Futamura Polyester Film FE2001”. Thicknesses are 12μm, 25μm, or 50μm.

[0496] • Backside treatment of PET… This film is obtained by corona treatment of the backside of “Taigaku Polyester Film FE2001” (12μm thick) manufactured by Futamura Chemical Co., Ltd. The corona treatment was performed using a “Corona Master PS-10S” corona treatment apparatus manufactured by Shinko Electric & Instrumentation Co., Ltd., at a processing voltage of 15kV and a processing speed of 100mm / s.

[0497] • FOR-AQ…Futamura Chemical Co., Ltd. manufactures OPP membranes called "Taige Polypropylene Membranes". The thickness is 25μm.

[0498] • Nylon…UNITIKA LTD. manufactures nylon film “ON-25”. Thickness is 25μm.

[0499] [Example 1]

[0500] <Image Recording>

[0501] Using the aforementioned image recording apparatus, a non-permeable substrate (P2161, 25 μm thick), the aforementioned pretreatment liquid, and the aforementioned white ink W1, inkjet recording was performed to obtain a substrate with an image. In Example 1, cyan ink was not used, and the treatment of the first inkjet head IJ1 and the first drying zone D1 was not performed.

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

[0503] The released non-permeable substrate is conveyed under tension.

[0504] The gravure coating machine, which serves as a pretreatment liquid application device P1, applies a pretreatment liquid to the conveyed non-permeable substrate.

[0505] Next, the pretreatment solution is dried at the pretreatment solution drying zone DP1.

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

[0507] Next, white ink W1 is applied in a solid image shape to the area of ​​the non-permeable substrate that has been treated with the pretreatment liquid through the second inkjet head IJ2.

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

[0509] Through the above operations, a white image (solid image) originating from white ink W1 is recorded on the conveyed non-permeable substrate, resulting in an image-bearing substrate.

[0510] Next, after air cooling, the obtained substrate with the image is wound up by a winding device R2 including a core to obtain a roll of substrate with the image.

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

[0512] The amount of pretreatment solution administered was set to 1.7 g / m³. 2 .

[0513] The amount of white ink applied was set to 3.8 g / m³. 2 .

[0514] The drying conditions for the pretreatment solution were set at 40°C for 3 seconds.

[0515] The drying conditions for white ink are set at 70°C for 20 seconds (hereinafter, this drying condition will be referred to as "control").

[0516] <Measurement of Surface Energy and Calculation of Surface Energy Difference ΔE>

[0517] Just before the aforementioned image recording was about to begin (specifically, one hour before or after the start time of image recording), the surface energy (i.e., the dispersed component γ) of the back side of the non-permeable substrate was measured in advance using the aforementioned method. S d Hydrogen bond component γ S h and surface energy γ S ).

[0518] After the image recording was wound up (specifically, within 1 hour after winding), the substrate with the image was unwound, and the surface energy (i.e., the dispersed component γ) of the white image in the substrate with the image was measured using the aforementioned 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 / m²) was calculated using the aforementioned method. 2 ).

[0520] The results are shown in Table 2.

[0521] <Calculation of ΔE / P ratio>

[0522] The ΔE / P ratio was calculated based on the surface energy difference ΔE and the tension P of the winding section.

[0523] The results are shown in Table 2.

[0524] <Evaluation>

[0525] By recording the images described above, images were recorded for 1000m of non-permeable substrate, resulting in a substrate roll with images for 1000m of non-permeable substrate.

[0526] The following evaluation was performed using the obtained substrate roll with the image.

[0527] The results are shown in Table 2.

[0528] (Adhesion of white images)

[0529] The substrate with the image was unwound, and the adhesion of the white image was evaluated at a position approximately 100m from the end of the winding, according to the following evaluation criteria.

[0530] In the following evaluation criteria, the best level of adhesion suppression for white images is AA.

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

[0532] AA: No peeling sound from unwinding was heard at a position approximately 100m from the end of the winding, and no transfer material was detected on the back of the non-permeable substrate.

[0533] A: At a position about 100m from the end of the winding, a peeling sound caused by the unwinding can sometimes be heard, but no transfer material was found on the back of the non-permeable substrate.

[0534] B: At a position approximately 100m from the end of the winding, a peeling sound caused by the unwinding of the winding was heard continuously, but no transfer material was detected on the back of the non-permeable substrate.

[0535] C: At a position approximately 100m from the end of the winding, a colorless and transparent transfer material was confirmed on the back of the non-permeable substrate.

[0536] D: At a position approximately 100m from the end of the winding, a white image transfer was confirmed on the back of the non-permeable substrate.

[0537] (Roll-up deviation of non-permeable substrate)

[0538] In evaluating the adhesion of white images, the imaged substrate roll was observed, and the maximum value of the distance (offset) between the axial end of the roll core and the width direction end of the non-permeable substrate was measured. The measurement result was taken as the roll offset of the non-permeable substrate. Based on the roll offset of the non-permeable substrate, the roll offset of the non-permeable substrate was evaluated according to the following evaluation criteria.

[0539] In the following evaluation criteria, the best grade for suppressing roll deviation in non-permeable substrates is AA.

[0540] Evaluation criteria for roll misalignment of non-permeable substrates-

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

[0542] A: The roll deviation of the non-permeable substrate is greater than 0.5mm and less than 1.0mm.

[0543] B: The roll deviation of the non-permeable substrate is greater than 1.0 mm and less than 2.0 mm.

[0544] C: The roll deviation of the non-permeable substrate is greater than 2.0 mm and less than 3.0 mm.

[0545] D: The roll deviation of the non-permeable substrate is 3.0 mm or more.

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

[0547] At least one of the following was changed to be as shown in Table 2: the type of white ink, the drying conditions of the white ink, the type of non-permeable substrate, the thickness of the non-permeable substrate, and the tension P of the winding section. Otherwise, the same operation as in Example 1 was performed.

[0548] The results are shown in Table 2.

[0549] Regarding the drying conditions for white ink, "strong drying" refers to drying at 75°C for 20 seconds, while "weak drying" refers to drying at 65°C for 20 seconds.

[0550] [Example 8]

[0551] Between the drying of the pretreatment liquid and the application of white ink, the application of cyan ink C1 based on the first inkjet head IJ1 and the drying of cyan ink C1 at the first drying zone D1 were added. Otherwise, the same operation as in Example 2 was performed.

[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 was applied, and white ink W1 is applied in a solid image and in an overlapping manner to the cyan ink C1 applied to the above-mentioned area (i.e., the solid cyan image).

[0554] The drying conditions for cyan ink C1 are set to 70°C for 20 seconds (i.e., "control").

[0555] [Comparative Examples 1-5]

[0556] At least one of the following was changed to be as shown in Table 2: the type of white ink, the drying conditions of the white ink, the type of non-permeable substrate, the thickness of the non-permeable substrate, and the tension P of the winding section. Otherwise, the same operation as in Example 1 was performed.

[0557] The results are shown in Table 2.

[0558]

[0559] As shown in Table 2, in Examples 1 to 12 with a ΔE / P ratio of 0.06 to 0.60, adhesion of the white image and roll-off of the non-permeable substrate were suppressed.

[0560] In contrast, in Comparative Examples 2 to 4, where the ΔE / P ratio was less than 0.06, adhesion of the white image was not suppressed.

[0561] Furthermore, in Comparative Examples 1 and 5, where the ΔE / P ratio exceeded 0.60, although the adhesion of the white image was suppressed, the roll-off of the non-permeable substrate was not suppressed.

[0562] The results of Examples 1, 5, 11 and 12 show that when ΔE is 5.0 to 25.0 (Examples 1 and 5), the roll-off of the non-permeable substrate can be further suppressed.

[0563] The results of Examples 1, 6, 7 and 10 show that when P is 30 to 150 (Examples 1, 6 and 10), the roll-off of the non-permeable substrate can be further suppressed.

[0564] The results of Examples 1 to 12 show that when the ΔE / P ratio is 0.10 or higher (Examples 2 to 9, 11 and 12), the adhesion of white images can be further suppressed.

[0565] The results of Examples 1 to 12 show that when the ΔE / P ratio is below 0.50 (Examples 1 to 6 and 8 to 11), the roll-off of the non-permeable substrate can be further suppressed.

[0566] [Modified Example of Example 8]

[0567] The cyan ink C1 in Example 8 was replaced with magenta ink M1 prepared as follows, and all other operations were performed in the same manner as in Example 8 (a variation of Example 8). As a result, the same evaluation results as in Example 8 were obtained in this variation.

[0568] <Preparation of Magenta Ink M1>

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

[0570] The above examples illustrate the application of a pretreatment solution before applying white ink, but the application of the pretreatment solution may be omitted.

[0571] When a white image is recorded directly or via a colored image on a non-permeable substrate without applying a pretreatment solution, the same effect as in the above-described embodiment group can be achieved by suppressing the adhesion of the white image and suppressing the roll-off of the non-permeable substrate.

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

[0573] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the same extent as the specific documents, patent applications and technical standards which are incorporated herein by reference.

Claims

1. An image recording method, comprising: The recording process involves applying white ink containing water and white pigment to one surface of a non-porous substrate using an inkjet printing method to record a white image. and In the winding process, the non-permeable substrate on which the white image is recorded is wound up under tension. When the other side of the non-permeable substrate is compared with the surface of the white image, the concentration is mJ / m 2 When the surface energy difference in units is set as ΔE and the tension in units of N / m is set as P, the value obtained by dividing ΔE by P, i.e., the ΔE / P ratio, is 0.06 to 0.

60.

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

3. The image recording method according to claim 2, wherein, The colored image is recorded before the white image and is positioned between one side 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 ranges from 5.0 to 25.

0.

5. The image recording method according to any one of claims 1 to 3, wherein, The value of P is 30 to 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, Prior to the recording step, the process further includes applying a pretreatment solution containing water and a coagulant to one surface of the non-permeable substrate. In the recording process, the white ink is applied to the area on one surface that has been treated with the pretreatment liquid to record the white image.

8. An image recording apparatus, used in the image recording method according to any one of claims 1 to 7, The image recording device includes: A recording unit includes an inkjet head for applying the white ink to one surface of the non-permeable substrate, and a recording process for recording the white image on one surface of the non-permeable substrate; and The winding unit includes a winding device that winds the non-porous substrate on which the white image is recorded under tension, and performs the winding process. The ΔE / P ratio is 0.06 to 0.60.

Images