Image recording method and image recording apparatus

Abstract

An image recording method includes a recording step in which a white ink containing water, a white pigment, and a resin is applied to one surface of an impermeable substrate by an inkjet method, and the applied white ink is heated and dried to record a white image, when the viscosity of a concentrated ink obtained by concentrating the white ink to 30% by mass is XmPa.s, and the rate of temperature rise from the start of heat drying to the passage of 5 seconds is Y DEG C / s, the product of X and Y is 30-280.

Description

Technical Field

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

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

[0003] For example, Patent Document 1 discloses the following printed matter manufacturing method as a printed matter manufacturing method for obtaining a printed matter with high-quality back-side printing.

[0004] In the printed matter manufacturing method disclosed in Patent Document 1, a first processing liquid containing a coagulant for aggregating color ink and white ink is applied to an impermeable medium, color ink is applied to the impermeable medium to which the first processing liquid is applied to print an image, and white ink is applied to the impermeable medium to which the color ink is applied. Here, when the total amount of the applied amount of the color ink and the applied amount of the white ink exceeds a threshold value, a second processing liquid containing at least a coagulant for aggregating the white ink is applied to the impermeable medium after the color ink is applied and before the white ink is applied.

[0005] Furthermore, Patent Document 2 discloses the following recording method as a recording method for ensuring lamination resistance in a backside printing mode on a transparent flexible packaging film.

[0006] The recording method disclosed in Patent Document 2 is a recording method for recording on a recording medium to be used by laminating a recording surface to be recorded, which includes: a non-white ink attachment process, in which an aqueous non-white ink composition containing a non-white colorant is attached to the recording medium; a white ink attachment process, in which an aqueous white ink composition containing a white colorant is attached to the recording medium subjected to the non-white ink attachment process; and a transparent ink attachment process, in which a transparent ink composition containing a resin is attached to the recording medium subjected to the white ink attachment process.

[0007] Patent Document 3 discloses the following inkjet printer as a combined front and back printing inkjet printer capable of performing either front printing or back printing with aqueous ink while continuously conveying a roll-shaped printing substrate at high speed.

[0008] The inkjet printer disclosed in Patent Document 3 comprises: a first white ink nozzle, which sprays white aqueous ink onto the surface of a roll-shaped printing substrate when printing on the surface; a first drum-type drying unit, which dries the white aqueous ink when printing on the surface; a second white ink nozzle, which sprays white aqueous ink onto the surface of a roll-shaped printing substrate when printing on the back; and a second drum-type drying unit, which dries the white aqueous ink when printing on the back.

[0009] Patent Document 1: International Publication No. 2020 / 137323

[0010] Patent Document 2: Japanese Patent Application Publication No. 2021-17005

[0011] Patent Document 3: International Publication No. 2019 / 131204 Summary of the invention

[0012] Technical issues to be solved by the invention

[0013] However, in an image recording method in which a white image is recorded by applying a white ink containing water, a white pigment and a resin to one surface of an impermeable substrate by an inkjet method and then heating and drying the applied white ink, there is sometimes a demand for further improvement in the concealability and adhesion of the recorded white image.

[0014] Here, the concealment of the white image refers to the performance of covering and hiding the color of the base on which the white image is recorded (for example, a non-permeable substrate, a colored image recorded before the white image, etc. The same applies hereinafter), and the adhesion of the white image refers to the adhesion of the white image relative to the base on which the white image is recorded.

[0015] The present invention has been completed in view of such a situation, and its object is to provide an image recording method and an image recording device, which can record a white image with excellent concealment and adhesion when a white image is recorded by applying white ink containing water, white pigment and resin to one surface of a non-permeable substrate by an inkjet method and heating and drying the applied white ink.

[0016] Means for solving technical problems

[0017] The present invention includes the following aspects.

[0018] <1> An image recording method, comprising:

[0019] The recording step is to apply white ink containing water, white pigment and resin to one surface of the non-permeable substrate by inkjet method and heat and dry the applied white ink to record a white image.

[0020] When the viscosity of the concentrated ink obtained by concentrating the white ink to reduce its mass by 30% at 32°C is X mPa·s and the temperature increase rate from the start of heat drying to 5 seconds is Y°C / s, the product of X and Y is 30-280.

[0021] <2> The image recording method according to <1>, wherein:

[0022] The product of X and Y is 40 to 200.

[0023] <3> The image recording method according to <1> or <2>, wherein:

[0024] The heating drying is performed by blowing hot air, and when the value obtained by dividing the wind speed of the hot air in m / s by the temperature of the hot air in ° C. is defined as Z, the product of X and Z is 2.0 to 10.0.

[0025] <4> The image recording method according to <3>, wherein:

[0026] The product of X and Z is 3.5 to 7.5.

[0027] <5> The image recording method according to any one of <1> to <4>, wherein:

[0028] The value obtained by dividing the film thickness of the white ink applied to one surface of the impermeable substrate after heat drying by the film thickness of the white ink applied to one surface of the impermeable substrate before heat drying is 0.10 to 0.20.

[0029] <6> The image recording method according to any one of <1> to <5>, wherein:

[0030] The film thickness of the white ink applied to one surface of the non-permeable substrate after heating and drying is 1.30 μm to 1.80 μm. <7> The image recording method according to any one of <1> to <6>, wherein

[0031] The recording step further includes a step of conveying the non-permeable substrate to which the white ink is applied by a conveying member in a configuration where the conveying member contacts the white ink,

[0032] The method further includes a winding step of winding up the non-permeable substrate on which the white image is recorded after the recording step.

[0033] The average contact surface pressure between the transport member and the white ink from the application of the white ink to the winding of the impermeable substrate was 750 N / m 2 ~4000N / m 2 .

[0034] <8> The image recording method according to any one of <1> to <7>, wherein:

[0035] The recording step further includes a step of applying a coloring ink containing water, a coloring pigment, and a resin to one surface of the non-permeable substrate by an inkjet method to record a coloring image.

[0036] <9> The image recording method according to <8>, wherein:

[0037] The colored image is recorded before the white image and is disposed between the non-permeable substrate and the white image.

[0038] <10> The image recording method according to any one of <1> to <9>, further comprising, before the recording step, applying a pretreatment liquid containing water and a coagulant to one surface of the non-permeable substrate,

[0039] In the recording step, white ink is applied to the area on one surface to which the pretreatment liquid is applied, thereby recording a white image.

[0040] <11> An image recording device used in the image recording method according to any one of <1> to <10>, the image recording device comprising:

[0041] An inkjet head for imparting the white ink onto one surface of a non-permeable substrate; and

[0042] A heating and drying device is used to heat and dry the white ink applied.

[0043] The product of the above X and the above Y is 30-280.

[0044] Effects of the Invention

[0045] According to one embodiment of the present invention, an image recording method and an image recording device are provided, which can record a white image with excellent concealment and adhesion when a white ink containing water, white pigment and resin is applied to one surface of a non-permeable substrate by an inkjet method and the applied white ink is heated and dried to record a white image. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a diagram conceptually showing an example of an image recording device used to implement the image recording method of the present invention. DETAILED DESCRIPTION

[0047] In the present invention, a numerical range expressed using "to" indicates a range including the numerical values ​​before and after "to" as the minimum value and the maximum value, respectively.

[0048] In the numerical ranges recorded in stages in this specification, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical ranges recorded in this specification, the upper limit or lower limit recorded in a certain numerical range can also be replaced by the value shown in the embodiments.

[0049] In the present invention, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0050] In the present invention, a combination of two or more preferred aspects is a more preferred aspect.

[0051] In the present invention, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0052] In the present invention, the “image” refers to the ink film itself when no pre-treatment liquid is used, and refers to a laminated film of the pre-treatment liquid film and the ink film when a pre-treatment liquid is used.

[0053] In the present invention, "image recording" means the formation of an image.

[0054] The concept of "image" in the present invention also includes a solid image.

[0055] In the present invention, the expression "applying ink to one surface of the substrate" includes a method of directly applying ink to one surface of the substrate and a method of directly applying ink to the surface of layer A when, for example, layer A is formed on one surface of the substrate.

[0056] In the present invention, unless otherwise specified, “upstream side” refers to the upstream side in the conveying direction of the impermeable substrate, and unless otherwise specified, “downstream side” refers to the downstream side in the conveying direction of the impermeable substrate.

[0057] [Image recording method]

[0058] The image recording method of the present invention (hereinafter, also referred to as "recording method") comprises:

[0059] The recording step is to apply white ink containing water, white pigment and resin to one side (hereinafter also referred to as "front side" or "recording side") of the non-permeable substrate by inkjet method and heat and dry the applied white ink to record a white image.

[0060] When the viscosity of the concentrated ink obtained by concentrating the white ink to reduce its mass by 30% at 32°C is X mPa·s and the temperature increase rate from the start of heat drying to 5 seconds is Y°C / s, the product of X and Y is 30-280.

[0061] According to the recording method of the present invention, a white image having excellent concealment property (ie, the property of covering and hiding the base color) and adhesion property (ie, adhesion to a non-permeable substrate) can be recorded.

[0062] Specifically, in the recording method of the present invention, when the product of X and Y (hereinafter also referred to as "product (X*Y)") is 30 or more, the concealment of the obtained white image is improved, and when the product (X*Y) is 280 or less, the adhesion of the obtained white image is improved.

[0063] The reason why the concealment property of the white image is improved when the product (X*Y) is 30 or more is considered to be as follows.

[0064] X (i.e., the viscosity of the concentrated ink obtained by concentrating the white ink to reduce the mass by 30% at 32° C.) is a viscosity that simulates the viscosity of the white ink when dried by heat drying. It is considered that if X is too small, the white pigment is easily precipitated in the film formed by the white ink (hereinafter also referred to as the white ink film), and as a result, the film thickness of the white ink film becomes thin, and the concealability of the white image tends to decrease.

[0065] It is considered that if Y (i.e., the temperature increase rate from the start of heat drying to 5 seconds) is too small, drying (i.e., solvent volatilization) becomes slow, the white pigment is easily precipitated in the white ink film, and the hiding power of the white image tends to decrease.

[0066] With respect to these tendencies, it is considered that by setting the product (X*Y) to 30 or more, precipitation of the white pigment in the white ink film is suppressed, and as a result, the hiding property of the obtained white image can be ensured.

[0067] The reason why the adhesion of the obtained white image is improved when the product (X*Y) is 280 or less is considered to be as follows.

[0068] It is considered that as X increases, the concealment of the white image is improved, but the film thickness of the white ink film increases, the film quality tends to decrease, and the adhesion of the white image tends to decrease.

[0069] Furthermore, when Y is too large, drying becomes too fast, and skinning is likely to occur on the white ink film, and the drying inside the white ink film is insufficient, so that the adhesion of the white image tends to decrease.

[0070] With regard to these trends, it is considered that by setting the product (X*Y) to 280 or less, skinning of the white ink film, insufficient drying inside, and reduction in film quality can be suppressed, and as a result, adhesion of the obtained white image (adhesion to the non-permeable substrate) can be ensured.

[0071] <Product(X*Y)>

[0072] As described above, in the recording method of the present invention, the product (X*Y) is 30-280.

[0073] When the product (X*Y) is 30 or more, the concealment property of the obtained white image is improved.

[0074] When the product (X*Y) is 280 or less, the adhesion of the obtained white image is improved.

[0075] The product (X*Y) is preferably 40-200.

[0076] When the product (X*Y) is 40 or more, the concealment property of the obtained white image is further improved.

[0077] When the product (X*Y) is 280 or less, the adhesion of the obtained white image is further improved.

[0078] "X" in the product (X*Y) is the viscosity (in mPa·s) at 32°C of the concentrated ink obtained by concentrating the white ink until the mass is reduced by 30%.

[0079] Here, “concentration” means to remove a part of the solvent (that is, water and, when contained, a water-soluble organic solvent. The same shall apply hereinafter) in the white ink.

[0080] That is, the concentrated ink is an ink obtained by removing (for example, distilling off) 30% of the solvent from the white ink relative to the total mass of the white ink.

[0081] The viscosity of the concentrated ink at 32° C. is measured using a viscometer (for example, TV-22 viscometer manufactured by TOKI SANGYO CO., LTD.).

[0082] In the recording method of the present invention, by setting the degree of concentration (i.e., solvent removal) of the white ink used to obtain "X" to "30% reduction", the accuracy of the relationship between the product (X*Y) and the effect (hiddenness and adhesion of the white image) is improved.

[0083] It is considered that if the concentration (ie, solvent removal) degree is set to, for example, "20% or less reduction" instead of "30% reduction", the fluidity of the white ink is not lost and the accuracy of the relationship between the product (X*Y) and the effect is insufficient.

[0084] If the degree of concentration (ie, solvent removal) is set to, for example, "40% or more reduction" instead of "30% reduction", it may be difficult to distinguish the difference in fluidity of the white ink, and the relationship between the product (X*Y) and the effect may be insufficiently accurate.

[0085] "X" in the product (X*Y) is preferably 10.0 to 20.0, more preferably 10.0 to 19.0, and further preferably 11.0 to 17.0.

[0086] "Y" in the product (X*Y) is the temperature increase rate (unit: °C / s) from the start point of heat drying to the time when 5 seconds have passed.

[0087] The temperature increase rate refers to the rate at which the surface temperature of the white ink film subjected to heat drying increases.

[0088] The surface temperature of the white ink film is measured using a non-contact thermometer (for example, FT-H20 manufactured by KEYENCE CORPORATION).

[0089] In the present invention, by defining "Y" as the temperature increase rate from the start time of heat drying until "5 seconds" have passed, the accuracy of the relationship between the product (X*Y) and the effect is improved.

[0090] When Y is defined as being shorter than when “5 seconds” has elapsed (for example, “3 seconds or less”), it is considered that the accuracy of the temperature increase rate is insufficient.

[0091] When Y is set to a time longer than "5 seconds" (for example, "7 seconds or longer"), the temperature rise may become insensitive, and it is also considered that the speed accuracy is insufficient.

[0092] "Y" in the product (X*Y) is preferably 1.0 to 25.0, more preferably 1.5 to 20.0, and even more preferably 2.0 to 15.0.

[0093] <Recording process>

[0094] The recording step is a step of applying white ink containing water, white pigment and resin to the front surface of the non-permeable substrate by an inkjet method and heating and drying the applied white ink to record a white image.

[0095] (Impermeable substrate)

[0096] In the present invention, the impermeability of the impermeable substrate refers to a property in which the water absorption rate measured in accordance with ASTM D570-98 (2018) for 24 hours is 2.5% or less. Here, the "%" as the unit of water absorption rate is a mass basis. The above water absorption rate is preferably 1.0% or less, and more preferably 0.5% or less.

[0097] Examples of the material of the non-permeable substrate include glass, metals (e.g., aluminum, zinc, copper, etc.) and resins (e.g., polyvinyl chloride, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, nylon, acrylic resin, etc.).

[0098] The material of the impermeable substrate is preferably resin. That is, the impermeable substrate is preferably an impermeable substrate.

[0099] Among them, from the viewpoint of versatility, the material of the impermeable substrate is preferably polypropylene, polyethylene, polyethylene terephthalate, nylon, acrylic resin or polyvinyl chloride.

[0100] The shape of the impermeable substrate is preferably sheet-like (film-like) or plate-like. Examples of the impermeable substrate having such a shape include glass plates, metal plates, resin sheets (resin films), paper laminated with plastic, paper laminated or vapor-deposited with metal, and plastic sheets (plastic films) laminated or vapor-deposited with metal.

[0101] Examples of the resin-made impermeable substrate include resin sheets (resin films), and specific examples include flexible packaging materials for packaging food and the like, and floor guides for large retail stores.

[0102] Examples of the impermeable substrate include sheet-shaped (film-shaped) or plate-shaped impermeable substrates and woven fabrics (textiles) and nonwoven fabrics formed of impermeable fibers.

[0103] The thickness of the impermeable substrate is preferably 0.1 μm to 1,000 μm, more preferably 0.1 μm to 800 μm, and further preferably 1 μm to 500 μm.

[0104] At least one of the front side and the back side of the impermeable substrate may be subjected to a surface treatment.

[0105] As surface treatment, corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (such as UV treatment) and flame treatment can be cited, but it is not limited to these. Corona treatment can be carried out using a corona treatment machine (product name "PS-10S", manufactured by Shinko Electric & Instrumentation Co., Ltd.).

[0106] The conditions for the surface treatment may be appropriately selected depending on the type of the impermeable substrate and the like.

[0107] Furthermore, the surface energy of the back surface of the impermeable substrate can be adjusted by adjusting the presence or absence of surface treatment on the back surface of the impermeable substrate and the conditions for surface treatment, thereby adjusting ΔE and the ΔE / P ratio.

[0108] The impermeable substrate may be a transparent impermeable substrate.

[0109] Here, having transparency means that the transmittance of visible light with a wavelength of 400 nm to 700 nm is 80% or more (preferably 90% or more).

[0110] When the impermeable substrate is a transparent impermeable substrate, the image can be easily visually recognized from the image rear side of the impermeable substrate through the impermeable substrate.

[0111] For example, in the case where the impermeable substrate is a transparent impermeable substrate, when recording is performed on the impermeable substrate in a manner in which a pattern image such as characters or graphics, i.e., a colored image, and a white image (e.g., a solid image) as a background image are arranged in sequence when viewed from the impermeable substrate side, it is easy to visually recognize the colored image (e.g., a pattern image such as characters or graphics) with the white image (e.g., a solid image) as the background from the image back side of the impermeable substrate through the impermeable substrate.

[0112] In the present invention, the "coloring" in the coloring ink and the coloring pigment refers to a color (for example, cyan, magenta, yellow, etc.) or black (hereinafter also referred to as Black).

[0113] 〔White ink〕

[0114] White ink contains water, white pigment and resin.

[0115] Next, the white ink will be described.

[0116] -water-

[0117] White ink contains water.

[0118] The content of water is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, and particularly preferably 50% by mass or more, based on the total amount of the white ink.

[0119] The upper limit of the water content relative to the total amount of the white ink can be appropriately determined according to the contents of other components, and is, for example, 99% by mass, preferably 95% by mass, and more preferably 90% by mass.

[0120] -White pigment-

[0121] White ink contains at least one white pigment.

[0122] Examples of the white pigment include inorganic pigments such as titanium dioxide, barium sulfate, calcium carbonate, silicon dioxide, zinc oxide, zinc sulfide, mica, talc, and pearl.

[0123] The white pigment is preferably titanium dioxide, barium sulfate, calcium carbonate or zinc oxide, more preferably titanium dioxide.

[0124] From the perspective of concealment, the average primary particle size of the white pigment is preferably 150 nm or more, more preferably 200 nm or more, and from the perspective of ink ejection properties, the average primary particle size of the white pigment is preferably 400 nm or less, more preferably 350 nm or less.

[0125] Here, the concealment property refers to the property of covering and hiding the base on which the white image is formed (for example, the front surface of the non-permeable substrate or a colored image recorded on the front surface before the white image) with the white image.

[0126] In the present invention, the average primary particle size of the white pigment is a value measured using a transmission electron microscope (TEM). Specifically, it is a value obtained by selecting any 50 white pigments present in the visual field observed by TEM to measure 50 primary particle sizes and averaging them. As a transmission electron microscope, a transmission electron microscope 1200EX manufactured by JEOL Ltd. can be used.

[0127] From the viewpoint of image density and ejection properties, when the ink contains a white pigment, the content of the white pigment is preferably 2 to 25% by mass, more preferably 5 to 25% by mass, and even more preferably 10 to 20% by mass relative to the total amount of the ink.

[0128] -Resin-

[0129] White ink contains at least one resin.

[0130] The resin in the white ink contributes to the film-forming property of the white ink (ie, the formability of the white ink film).

[0131] The weight average molecular weight (Mw) of the resin is preferably 1,000 to 300,000, more preferably 2,000 to 200,000, and further preferably 5,000 to 100,000.

[0132] In the present invention, unless otherwise specified, the weight average molecular weight (Mw) refers to a value measured by gel permeation chromatography (GPC).

[0133] In the measurement by gel permeation chromatography (GPC), HLC (registered trademark)-8020GPC (TOSOH CORPORATION) was used as a measuring apparatus, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mmID×15 cm, TOSOH CORPORATION) columns were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, as measurement conditions, the sample concentration was set to 0.45 mass%, the flow rate was set to 0.35 ml / min, the sample injection volume was set to 10 μl, and the measurement temperature was set to 40° C., and the RI detector was used for the measurement.

[0134] The calibration curve was prepared using eight samples of "TSK standard, polystyrene" produced by TOSOH Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0135] As the resin, there can be mentioned a pigment dispersion resin which is a pigment dispersant.

[0136] Examples of the resin include resin particles.

[0137] The white ink may contain at least one pigment dispersion resin.

[0138] The pigment dispersion resin is a resin having a function of dispersing a pigment.

[0139] The pigment dispersing resin may be a random copolymer or a block copolymer.

[0140] The pigment dispersion resin may have a cross-linked structure.

[0141] The ink can be prepared using a pigment dispersion containing a pigment and a pigment dispersing resin.

[0142] As the pigment dispersion resin, for example, a known polymer dispersant such as the polymer dispersants described in paragraphs 0029 to 0106 of International Publication No. 2021 / 221069 can be used.

[0143] When the white ink contains a pigment dispersion resin, the ratio of the content of the pigment in the ink to the content of the pigment dispersion resin is preferably 1:0.04 to 1:3, more preferably 1:0.05 to 1:1, and even more preferably 1:0.05 to 1:0.5 on a mass basis.

[0144] When the white ink contains a pigment dispersion resin, the content of the pigment dispersion resin is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and even more preferably 0.5 to 2.5% by mass, based on the total amount of the ink.

[0145] The white ink may contain at least one type of resin particles.

[0146] The resin constituting the resin particles is preferably a water-insoluble resin. The "water-insoluble" in the water-insoluble resin refers to a property that the amount of the resin that dissolves in 100 g of distilled water at 25°C is less than 2 g.

[0147] 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.

[0148] In the present invention, the volume average particle size refers to a value measured by a laser diffraction / scattering particle size distribution analyzer.

[0149] As a measuring apparatus, a particle size distribution measuring apparatus "Microtrac MT-3300II" (made by Nikkiso Co., Ltd.) is mentioned, for example.

[0150] The resin particles are preferably at least one selected from the group consisting of acrylic resin particles, ester resin particles, a mixture of acrylic resin particles and ester resin particles, composite particles containing acrylic resin and ester resin, styrene acrylic resin particles, and polyurethane resin particles.

[0151] In the present invention, acrylic resin refers to a polymer (homopolymer or copolymer) containing at least one raw material monomer selected from the group consisting of acrylic acid, acrylic acid derivatives (such as acrylic acid esters), methacrylic acid and methacrylic acid derivatives (such as methacrylic acid esters).

[0152] The glass transition temperature (Tg) of the resin particles is preferably 50°C to 250°C, more preferably 50°C to 150°C, from the viewpoint of further improving the abrasion resistance of the image.

[0153] Here, the glass transition temperature (Tg) of the resin particles is preferably a measured Tg obtained by actual measurement. For the measurement method of the measured Tg, reference can be made to paragraph 0111 of Japanese Patent Application Laid-Open No. 2015-25076.

[0154] Regarding the resin particles, for example, paragraphs 0038 to 0114 of International Publication No. 2021 / 192720, paragraphs 0109 to 0120 of Japanese Patent Application Laid-Open No. 2015-25076, and the like can be referred to.

[0155] When the white ink contains resin particles, the content of the resin particles in the white ink is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, based on the total amount of the white ink.

[0156] -Water-soluble organic solvents-

[0157] The white ink preferably contains at least one water-soluble organic solvent.

[0158] This ensures the stability of ejection from the inkjet head.

[0159] The water-soluble organic solvent contained in the white ink may be one kind or two or more kinds.

[0160] In the present invention, the "water-soluble" in the "water-soluble organic solvent" refers to the property of dissolving 1 g or more in 100 g of water at 25°C.

[0161] The type of water-soluble organic solvent that can be contained in the white ink is not limited, and examples thereof include:

[0162] Monoalcohols having 1 to 4 carbon atoms;

[0163] 1,2-ethanediol (alias: ethylene glycol), 1,3-propylene glycol (alias: propylene glycol), 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol and other diols;

[0164] Triols such as propylene glycol, 1,2,6-hexanetriol, and trimethylolpropane;

[0165] Alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether;

[0166] Polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol, etc.;

[0167] Polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether, and the like; and

[0168] 2-pyrrolidone, N-methyl-2-pyrrolidone;

[0169] wait.

[0170] From the viewpoint of discharge stability, the water-soluble organic solvent in the white ink preferably contains at least one selected from the group consisting of glycols and alkylene glycol monoalkyl ethers.

[0171] The content of the water-soluble organic solvent is preferably 10% by mass to 40% by mass, and more preferably 15% by mass to 30% by mass, based on the total amount of the white ink.

[0172] -Surfactant-

[0173] The white ink may contain at least one surfactant.

[0174] Examples of the surfactant include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants.

[0175] As a preferable surfactant, an acetylene glycol-based surfactant which is a kind of nonionic surfactant can be mentioned.

[0176] As the acetylene glycol-based surfactant, for example, the acetylene glycol-based surfactants described in paragraphs 0070 to 0080 of International Publication No. 2017 / 149917 can be used.

[0177] Examples of acetylene glycol surfactants include:

[0178] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 2,4,7,9-tetramethyl-5-decyne-4,7-diol,

[0179] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 3,6-dimethyl-4-octyne-3,6-diol,

[0180] A polyalkylene oxide adduct (preferably a polyethylene oxide adduct) of 2,5,8,11-tetramethyl-6-dodecene-5,8-diol,

[0181] Polyalkylene oxide adduct (preferably polyethylene oxide adduct) of 2,5-dimethyl-3-hexyne-2,5-diol

[0182] wait.

[0183] Commercially available products of acetylene glycol-based surfactants include: Surfynol series (e.g., Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485), OLFINE series (e.g., OLFINE E1010, OLFINE E1020), Dynol series (e.g., Dynol 604), etc. manufactured by Air Products Ltd. or Nissin Chemical Co., Ltd.; ACETYLENOL manufactured by Kawaken Fine Chemicals Co., Ltd., etc.

[0184] Commercial products of acetylene glycol-based surfactants are also provided by The Dow Chemical Company, General Aniline & Film Corp., and the like.

[0185] As surfactants, there can be mentioned compounds listed as surfactants in JP-A-59-157636, pages 37 to 38, and Research Disclosure No. 308119 (1989). In addition, there can be mentioned fluorine (fluorinated alkyl) surfactants and silicone surfactants described in JP-A-2003-322926, JP-A-2004-325707, and JP-A-2004-309806.

[0186] When the white ink contains a surfactant, the content of the surfactant in the white ink can be appropriately adjusted in consideration of the surface energy of the white image to be recorded.

[0187] The content of the surfactant in the white ink is preferably 0.01% by mass to 5% by mass, more preferably 0.05% by mass to 3% by mass, and even more preferably 0.1% by mass to 2% by mass, based on the total amount of the white ink.

[0188] -Other ingredients-

[0189] The white ink may contain other components in addition to the above components.

[0190] As other components, for example, there can be mentioned known additives such as silicic acid compounds (for example, silicic acid compounds described in paragraphs 0058 to 0075 of Japanese Patent No. 5430316), urea, urea derivatives, wax, anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, mildewproofing agents, pH adjusters, defoaming agents, viscosity adjusters, dispersion stabilizers, and chelating agents.

[0191] -Physical properties-

[0192] From the viewpoint of improving discharge stability, the pH (25° C.) of the white ink is preferably 7 to 10, and more preferably 7.5 to 9.5. The pH of the ink can be measured by the same method as the pH of the pretreatment liquid.

[0193] The viscosity (32° C.) of the white ink is preferably 0.5 mPa·s to 30 mPa·s, more preferably 2 mPa·s to 20 mPa·s, further preferably 2 mPa·s to 15 mPa·s, and further preferably 3 mPa·s to 10 mPa·s.

[0194] The viscosity of the white ink is measured using a viscometer (for example, TV-22 type viscometer manufactured by TOKI SANGYO CO., LTD.).

[0195] The surface tension (25° C.) of the white ink is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 25 mN / m to 40 mN / m.

[0196] The surface tension is measured at 25° C. using a surface tensiometer, for example, by a plate method using an automatic surface tensiometer manufactured by Kyowa Interface Science Co., Ltd. (product name “CBVP-Z”).

[0197] (Provision of white ink)

[0198] The recording step includes a step of applying white ink to the front surface of the non-permeable substrate by an inkjet method.

[0199] There is no particular limitation on the method of ejecting white ink based on the inkjet method, and it may be a known method, for example, a charge control method that utilizes electrostatic attraction to eject ink, a drop-on-demand inkjet method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into a sound beam and irradiates the beam onto the ink to eject the ink using radiation pressure, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0200] As the inkjet method, the method described in Japanese Patent Publication No. 54-59936, i.e., the inkjet recording method, can be particularly effectively used. In this inkjet recording method, the ink subjected to the action of heat energy undergoes a rapid volume change, and the ink is ejected from the nozzle using the force generated by the state change. As the inkjet method, the method described in paragraphs 0093 to 0105 of Japanese Patent Publication No. 2003-306623 can also be applied.

[0201] The application of the white ink onto the front surface of the non-permeable substrate is performed by an inkjet method by ejecting the white ink from nozzles of an inkjet head.

[0202] As inkjet head methods, there are a reciprocating method in which a short serial head records while scanning in the width direction of the recording medium (i.e., non-permeable substrate, the same below) and a linear method in which a line head is used in which recording elements are arranged corresponding to the entire area of ​​one side of the recording medium.

[0203] In the linear method, by scanning the recording medium in a direction intersecting the arrangement direction of the recording elements, it is possible to record an image on the entire surface of the recording medium. In the linear method, there is no need for a transport system such as a carriage that scans the short strip-shaped nozzle in the reciprocating method. In addition, compared with the reciprocating method, in the linear method, there is no need for the movement of the carriage and the complex scanning control of the recording medium, and only the recording medium moves. Therefore, according to the linear method, it is possible to achieve higher speed image recording than in the reciprocating method.

[0204] The application of white ink is preferably performed using an inkjet head having a resolution of 300 dpi or more (more preferably 600 dpi or more, and even more preferably 800 dpi or more). Dpi is an abbreviation for dots per inch, and 1 inch is 2.54 cm.

[0205] From the viewpoint of obtaining a high-definition image, the ejection amount of the white ink is preferably 1 pL (picoliter) to 10 pL, and more preferably 1.5 pL to 6 pL.

[0206] (Drying of white ink)

[0207] In the recording step, the white ink applied to the front surface of the non-permeable substrate is heated and dried to obtain a white image.

[0208] There are no particular restrictions on the heating and drying method of the white ink, and examples thereof include infrared (IR) drying, warm air blowing (i.e., warm air drying, such as a dryer, etc.), and heating drying using a heating device (e.g., a heater, a hot plate, a heating roller, a heating furnace, etc.).

[0209] As the heat drying method, a method of combining two or more of these may be used.

[0210] Heat drying can be performed by heating the white ink from at least one of the front side and the back side of the impermeable substrate.

[0211] The heating temperature during heat drying of the white ink is preferably 35° C. or higher, more preferably 40° C. or higher, further preferably 50° C. or higher, and further preferably 60° C. or higher.

[0212] The upper limit of the heating temperature is not particularly limited, but is preferably 100°C, more preferably 90°C.

[0213] The heating time during heat drying of the white ink is not particularly limited, but is preferably 1 second to 180 seconds, more preferably 1 second to 120 seconds, and even more preferably 1 second to 60 seconds.

[0214] In the heat drying of the white ink, the temperature increase rate of the surface of the white ink from the start point of the heat drying to the time when 5 seconds have passed is "Y" in the above-mentioned product (X*Y).

[0215] The range of the product (X*Y) and the preferred range of "Y" are as described above.

[0216] The heat drying of the white ink is preferably performed by blowing warm air (ie, warm air drying).

[0217] Thereby, the abrasion resistance of the white image is further improved.

[0218] -Product(X*Z)-

[0219] In warm air drying, when the value obtained by dividing the wind speed of the warm air in m / s by the temperature of the warm air in ° C is set to "Z", the product of the aforementioned "X" (i.e., the viscosity of the concentrated ink obtained by concentrating the white ink until the mass is reduced by 30% at 32°C (in mPa·s)) and "Z" (hereinafter also referred to as "product (X*Z)") is preferably 0.5 to 18.0, more preferably 1.0 to 15.0, further preferably 2.0 to 10.0, and further preferably 3.5 to 7.5.

[0220] When the product (X*Z) is 0.5 or more, the abrasion resistance of the white image is further improved.

[0221] When the product (X*Z) is 18.0 or less, the abrasion resistance of the white image is further improved.

[0222] "Z" is preferably 0.04 to 1.20, more preferably 0.10 to 1.00, and further preferably 0.15 to 0.80.

[0223] -Ratio〔Dry film thickness / Wet film thickness〕-

[0224] In the present invention, the value obtained by dividing the film thickness of the white ink applied to the front surface of the impermeable substrate after heating and drying (hereinafter, also referred to as "dry film thickness" or "A"; unit: μm) by the film thickness of the white ink applied to the front surface of the impermeable substrate before heating and drying (hereinafter, also referred to as "wet film thickness" or "B"; unit: μm) (hereinafter, also referred to as "ratio [dry film thickness / wet film thickness]" or "A / B") is preferably 0.10 to 0.30, more preferably 0.10 to 0.25, and further preferably 0.10 to 0.20.

[0225] When the ratio [dry film thickness / wet film thickness] is 0.10 or more, the concealability of the white image is further improved.

[0226] When the ratio [dry film thickness / wet film thickness] is 0.30 or less, the adhesion of the white image is further improved.

[0227] The wet film thickness of the white ink is the film thickness of the white ink (ie, the white ink film) applied to the front surface of the non-permeable substrate before being subjected to heat drying.

[0228] The wet film thickness of the white ink was calculated as a numerical value with two decimal places in units of μm from the ejection amount [pL / pixel] of the ink ejected from the inkjet head and the resolution.

[0229] The dry film thickness of the white ink is the film thickness of the white ink film before being heated and dried.

[0230] In other words, the dry film thickness of the white ink is the film thickness of the white image.

[0231] The dry film thickness was measured by taking a scanning electron microscope (SEM) image (magnification 10,000 times) of a cross section of an image record (i.e., an impermeable substrate with a white image). The dry film thickness was measured in μm units as a numerical value with two decimal places.

[0232] When the recording method of the present invention includes the winding step described later, the dry film thickness of the white ink is measured by unwinding the image recorded material (i.e., the non-permeable substrate with the white image) wound up in the winding step and measuring the film thickness of the white image on the unwound image recorded material.

[0233] The dry film thickness of the white ink is preferably 0.60 μm to 2.50 μm, more preferably 0.80 μm to 2.00 μm, further preferably 1.00 μm to 2.00 μm, and further preferably 1.30 μm to 1.80 μm.

[0234] When the dry film thickness of the white ink is 0.60 μm or more, the concealability of the white image is further improved.

[0235] When the dry film thickness of the white ink is 2.50 μm or less, the adhesion of the white image is further improved.

[0236] The recording step may further include a step of conveying the impermeable substrate to which the white ink is applied by a conveying member in a configuration in which the conveying member contacts the white ink.

[0237] In this case, the conveyance of the impermeable substrate can be carried out by a conveying member (for example, a conveying member described below) in contact with the white ink (that is, the front side of the impermeable substrate). Figure 1 The conveying roller T1 in the embodiment of the present invention and the conveying member (for example, the conveying roller T2 described below) in contact with the back side of the impermeable substrate Figure 1This is done using the conveying roller T2).

[0238] Furthermore, the transport by the transport member is not only performed during the recording step, but can also be performed throughout the entire process of the recording method of the present invention.

[0239] The recording step further includes a step of conveying the impermeable substrate to which the white ink is applied by a conveying member in a configuration in which the conveying member contacts the white ink, and in the case where the recording method of the present invention further includes a winding step of winding up the impermeable substrate on which the white image is recorded after the recording step, the average contact surface pressure between the conveying member and the white ink (i.e., the white ink film) from the application of the white ink to the winding up of the impermeable substrate is preferably 375 N / m 2 ~4500N / m 2 , more preferably 500N / m 2 ~4500N / m 2 , more preferably 750N / m 2 ~4000N / m 2 .

[0240] When the average contact surface pressure is 375N / m 2 When the above amount is exceeded, the transportability of the impermeable substrate is further improved.

[0241] When the average contact surface pressure is 4500N / m 2 When the thickness of the white image is less than 0.5 μm, it is possible to suppress a reduction in the film thickness of the white image due to contact with the transport member, and as a result, the concealability of the white image is further improved.

[0242] Here, when there is only one transport member in contact with the white ink film, the average contact surface pressure between the transport member and the white ink film is equal to the contact surface pressure between the one transport member and the white ink film.

[0243] When there are a plurality of transport members in contact with the white ink film, the average contact surface pressure between the transport members and the white ink film is the arithmetic average of the contact surface pressures between the respective transport members and the white ink film.

[0244] When a transport roller is used as the transport member, the contact surface pressure between the transport roller and the white ink film is obtained by dividing the tension (N / m) of the impermeable substrate transported by the transport roller by the roller radius (m) of the transport roller.

[0245] (Record of colored images)

[0246] The recording step may further include a step of applying a coloring ink containing water, a coloring pigment, and a resin to the front surface of the non-permeable substrate by an inkjet method to record a coloring image.

[0247] According to this aspect, a multi-color image including a white image and a colored image can be recorded on the front surface of the impermeable substrate.

[0248] In this method, only one coloring ink can be used to record only one coloring image (for example, one of a cyan image, a magenta image, a yellow image, and a black image), or more than two coloring inks can be used to record more than two coloring images (for example, two or more of a cyan image, a magenta image, a yellow image, and a black image).

[0249] The preferred embodiment of applying the colored ink is the same as the preferred embodiment of applying the white ink.

[0250] In the recording step, the color ink applied to the front surface of the non-permeable substrate may be heated and dried as necessary to obtain a color image. The preferred method for heating and drying the color ink in this case is the same as the preferred method for heating and drying the white ink.

[0251] The colored image may be recorded before or after the white image.

[0252] As a method of recording a colored image before a white image, for example, a method of placing a colored image (e.g., a pattern image such as characters or graphics) between the front surface of the impermeable substrate and the white image (e.g., a solid image) can be cited. This method is a method of visually recognizing the colored image (e.g., a pattern image such as characters or graphics) with the white image (e.g., a solid image) as a background from the back side of the impermeable substrate through the impermeable substrate.

[0253] As a method of recording a colored image after a white image, for example, a method of placing a colored image (e.g., a pattern image such as characters or graphics) on a white image (e.g., a solid image) is mentioned. This method is a method in which the colored image (e.g., a pattern image such as characters or graphics) on the upper layer side with the white image (e.g., a solid image) on the lower layer side as a background is visually recognized from the front side of the impermeable substrate.

[0254] From the viewpoint of more effectively exerting the effects of the recording method of the present invention, the colored image is preferably recorded before the white image and disposed between the front surface of the non-permeable substrate and the white image.

[0255] -Coloring ink-

[0256] The coloring ink for recording a coloring image contains water, a coloring pigment (ie, a color or black pigment), and a resin.

[0257] Preferred aspects of the colored ink are the same as those of the aforementioned preferred aspects of the white ink, except for the type of pigment.

[0258] The coloring pigment may be any of commercially available organic pigments and inorganic pigments.

[0259] Examples of coloring pigments include pigments described in "Encyclopedia of Pigments" edited by Seijiro Ito (published in 2000), "Industrial Organic Pigments" by W. Herbst, K. Hunger, JP-A-2002-12607, JP-A-2002-188025, JP-A-2003-26978, and JP-A-2003-342503.

[0260] Furthermore, the coloring pigment may be a water-insoluble pigment that can be dispersed in water using a dispersant, or may be a self-dispersible pigment.

[0261] The self-dispersible pigment is a pigment that can be dispersed in water without using a dispersant.

[0262] Self-dispersible pigments are compounds in which at least one selected from the group consisting of hydrophilic groups such as carbonyl, hydroxyl, carboxyl, sulfonyl, and phosphoric acid groups and salts thereof is chemically bonded to the pigment surface directly or via other groups.

[0263] From the viewpoint of the density of the colored image and the ejection properties of the colored ink, the content of the colored pigment in the colored ink is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 1 to 10% by mass, relative to the total amount of the ink.

[0264] <Pre-treatment liquid application step>

[0265] The recording method of the present invention may further include a step of applying a pretreatment liquid containing water and a coagulant to the front surface of the impermeable substrate before the recording step (hereinafter also referred to as a "pretreatment liquid applying step").

[0266] In this case, in the recording step, the white ink is applied to the area on the front surface to which the pretreatment liquid is applied by an inkjet method, thereby recording the white image.

[0267] According to the embodiment including the pre-treatment liquid application step, the components of the white ink are aggregated by the action of the aggregating agent applied in advance to the front surface, which is advantageous in terms of the image quality of the white image.

[0268] In the embodiment including the pre-treatment liquid applying step, the above-mentioned colored image may be recorded in addition to the white image.

[0269] In this case, the color ink is applied to the area on the front surface to which the pretreatment liquid is applied by inkjet method to record the color image. Thus, the components of the color ink are aggregated by the action of the aggregating agent, which is advantageous in terms of the image quality of the color image.

[0270] As mentioned above, the colored image can be recorded on the upper side of the white image (the side away from the non-permeable substrate) or on the lower side of the white image (the side close to the non-permeable substrate. That is, between the front side of the non-permeable substrate and the white image), preferably on the lower side of the white image.

[0271] (Pretreatment liquid)

[0272] The pretreatment liquid contains water and a coagulant.

[0273] -water-

[0274] The pretreatment liquid contains water.

[0275] The content of water is preferably 50% by mass or more, more preferably 60% by mass or more, based on the total amount of the pretreatment liquid.

[0276] The upper limit of the water content depends on the amounts of other components, but is preferably 90% by mass or less, and more preferably 80% by mass or less, based on the total amount of the pretreatment liquid.

[0277] - Coagulant -

[0278] The pretreatment liquid contains at least one coagulant.

[0279] The aggregating agent in the pretreatment liquid aggregates the components in the ink on the front surface of the non-permeable substrate, thereby improving the image quality.

[0280] The coagulant is preferably at least one selected from the group consisting of organic acids, polyvalent metal compounds, metal complexes, and cationic polymers.

[0281] Preferred examples of the coagulant include those described in paragraphs 0122 to 0130 of International Publication No. 2020 / 195360.

[0282] Hereinafter, preferred embodiments of each of the organic acid, the polyvalent metal compound, the metal complex, and the cationic polymer that can be used as the coagulant will be described.

[0283] --Organic Acids--

[0284] Examples of the organic acid include organic compounds having an acidic group.

[0285] Examples of the acidic group include a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfonic acid group, a sulfinic acid group, and a carboxyl group.

[0286] Among them, from the viewpoint of the aggregation speed of the ink, the acidic group is preferably a phosphoric acid group or a carboxyl group, and more preferably a carboxyl group.

[0287] It is preferred that at least a part of the acidic groups be dissociated in the pretreatment liquid.

[0288] Examples of the organic compound having a carboxyl group include (meth)acrylic acid, poly(meth)acrylic acid, acetic acid, formic acid, benzoic acid, glycolic acid, malonic acid, malic acid (preferably DL-malic acid), maleic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, fumaric acid, citric acid, tartaric acid, phthalic acid, 4-methylphthalic acid, lactic acid, pyrrolidonecarboxylic acid, pyranonecarboxylic acid, pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid, coumaric acid, thiophenecarboxylic acid and nicotinic acid.

[0289] Among them, from the viewpoint of the aggregation speed of the ink, the organic compound having a carboxyl group is preferably a divalent or higher-valent carboxylic acid (hereinafter also referred to as a polyvalent carboxylic acid), and more preferably a dicarboxylic acid.

[0290] 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.

[0291] The organic acid preferably has a low pKa (eg, 1.0 to 5.0). Thus, the surface charge of particles such as pigments and resin particles in the ink dispersed and stabilized by weakly acidic functional groups such as carboxyl groups is reduced by contact with an organic acid with a lower pKa, thereby reducing dispersion stability.

[0292] The organic acid preferably has a low pKa, high solubility in water, and a valence of 2 or more. Furthermore, the organic acid more preferably has a high buffering capacity in a pH region lower than the pKa of the functional group (eg, carboxyl group) that stabilizes particle dispersion in the ink.

[0293] --Multivalent Metal Compounds--

[0294] Examples of the polyvalent metal compound include polyvalent metal salts.

[0295] Examples of the polyvalent metal salt include organic acid polyvalent metal salts and inorganic acid polyvalent metal salts.

[0296] As the organic acid polyvalent metal salt, polyvalent metal salts of the above-mentioned organic acids (for example, formic acid, acetic acid, benzoic acid, etc.) are preferred.

[0297] As the inorganic acid polyvalent metal salt, a nitrate polyvalent metal salt, a hydrochloride polyvalent metal salt or a thiocyanate polyvalent metal salt is preferred.

[0298] Examples of polyvalent metal salts include salts of alkaline earth metals of Group 2 of the periodic table (e.g., magnesium and calcium), salts of transition metals of Group 3 of the periodic table (e.g., lanthanum), salts of metals of Group 13 of the periodic table (e.g., aluminum), and salts of lanthanides (e.g., neodymium).

[0299] As the polyvalent metal salt, a calcium salt, a magnesium salt or an aluminum salt is preferred, and a calcium salt or a magnesium salt is more preferred.

[0300] As the polyvalent metal compound, an organic acid polyvalent metal salt is preferred, and an organic acid calcium salt or an organic acid magnesium salt is more preferred.

[0301] It is preferred that at least a part of the polyvalent metal compound is dissociated into polyvalent metal ions and counter ions in the pretreatment liquid.

[0302] --Metal Complexes--

[0303] The metal complex preferably contains at least one selected from the group consisting of zirconium, aluminum, and titanium as a metal element.

[0304] The metal complex is preferably a metal complex containing at least one selected from the group consisting of acetate, acetylacetonate, methyl acetoacetate, ethyl acetoacetate, octanediol, butoxyacetylacetone, lactate, lactate ammonium salt and triethanolaminate as a ligand.

[0305] The metal complex may be a commercially available product. Various organic ligands, especially various multidentate ligands capable of forming metal chelate catalysts, are commercially available. Therefore, the metal complex may be a metal complex prepared by combining commercially available organic ligands and metals.

[0306] --Cationic polymers--

[0307] The cationic polymer is preferably a homopolymer of a cationic monomer having a primary or tertiary amino group or a quaternary ammonium salt group, or a copolymer or polycondensate of a cationic monomer and a non-cationic monomer. The cationic polymer may be used in the form of a water-soluble polymer or a water-insoluble polymer (ie, latex particles).

[0308] Examples of the cationic polymer include polyvinyl pyridinium salts, polyalkylaminoethyl acrylates, polyalkylaminoethyl methacrylates, polyvinylimidazoles, polyethyleneimine, polybiguanide, polyguanidine, polyallylamine, and derivatives thereof.

[0309] From the viewpoint of the viscosity of the pretreatment liquid, the cationic polymer preferably has a small weight average molecular weight. When the pretreatment liquid is applied to an impermeable substrate by inkjet recording, it is preferably 1,000 to 500,000, more preferably 1,500 to 200,000, and further preferably 2,000 to 100,000. When the weight average molecular weight is 1,000 or more, it is advantageous from the viewpoint of the coagulation rate. When the weight average molecular weight is 500,000 or less, it is advantageous from the viewpoint of ejection reliability. However, when the pretreatment liquid is applied to an impermeable substrate by a method other than inkjet recording, it is not limited thereto.

[0310] The content of the coagulant in the pretreatment liquid is preferably 0.1 to 40% by mass, more preferably 0.1 to 30% by mass, further preferably 1 to 20% by mass, and further preferably 1 to 10% by mass, based on the total amount of the pretreatment liquid.

[0311] -Resin-

[0312] The pretreatment liquid may contain at least one resin.

[0313] The resin in the pretreatment liquid contributes to the film-forming property of the pretreatment liquid (ie, the film-forming property based on the pretreatment liquid).

[0314] As the resin in the pretreatment liquid, the same resin as the resin in the ink (for example, resin particles) can be used.

[0315] The content of the resin in the pretreatment liquid is not particularly limited.

[0316] The content of the resin is preferably 0.5% by mass to 30% by mass, more preferably 1% by mass to 20% by mass, and particularly preferably 1% by mass to 15% by mass, based on the total amount of the pretreatment liquid.

[0317] -Water-soluble organic solvents-

[0318] The pretreatment liquid may contain at least one water-soluble organic solvent.

[0319] As the water-soluble organic solvent in the pretreatment liquid, the same water-soluble organic solvent as that which can be contained in the ink can be used.

[0320] -additive-

[0321] The ink may contain additives such as a surfactant, a water-soluble resin, a co-sensitizer, an ultraviolet absorber, an antioxidant, an anti-fading agent, a conductive salt, and an alkaline compound as necessary.

[0322] -Physical properties-

[0323] The pH of the pretreatment liquid is preferably 2.0 to 7.0, and more preferably 2.0 to 4.0. The pH of the pretreatment liquid is measured by the same method as the pH of the ink.

[0324] From the viewpoint of coating properties of the pretreatment liquid, the viscosity of the pretreatment liquid is preferably 0.5 to 10 mPa·s, more preferably 1 to 5 mPa·s. The viscosity is a value measured using a viscometer at 25° C. The viscosity of the pretreatment liquid is measured by the same method as the viscosity of the ink.

[0325] The surface tension of the pretreatment liquid is preferably 60 mN / m or less, more preferably 20 mN / m to 50 mN / m, and further preferably 30 mN / m to 45 mN / m. The surface tension is a value measured at a temperature of 25° C. The surface tension of the pretreatment liquid is measured by the same method as the surface tension of the ink.

[0326] (Method of applying pretreatment liquid)

[0327] The method for applying the pretreatment liquid is not particularly limited, and examples thereof include known methods such as a coating method, a dipping method, and an inkjet recording method.

[0328] Examples of the coating method include known coating methods using a bar coater, extrusion die coater, air knife coater, blade coater, rod coater, knife coater, extrusion coater, reverse roll coater, and the like.

[0329] (Drying of pretreatment liquid)

[0330] The pretreatment liquid applying step may include a step of drying the pretreatment liquid applied to the front surface of the non-permeable substrate.

[0331] The method for drying the pretreatment liquid is not particularly limited, and for example, the same method as exemplified as the method for drying the white ink can be applied.

[0332] The preferred range of drying conditions (for example, heating temperature and heating time) of the pretreatment liquid is the same as the preferred range of drying conditions of the white ink.

[0333] <Coiling process>

[0334] The recording method of the present invention may include a winding step of winding up the non-permeable substrate on which the white image is recorded.

[0335] The winding step is not particularly limited, and can be performed using a known winding device including a winding core.

[0336] The recording method of the present invention may include other steps besides the above steps.

[0337] <Image recording device>

[0338] The image recording device used in the image recording method of the present invention comprises:

[0339] An inkjet head for imparting the white ink to one surface of the non-permeable substrate; and

[0340] A heating and drying device is used to heat and dry the white ink applied.

[0341] In the image recording device,

[0342] The product of the above X and the above Y is 30-280.

[0344] According to the above-mentioned image recording device, the same effects as those of the above-mentioned image recording method of the present invention can be achieved.

[0345] <An example of an image recording device>

[0346] Figure 1 This is a diagram conceptually showing an example of an image recording device used in the image recording method of the present invention.

[0347] like Figure 1 As shown, the image recording device involved in this example is an example of an image recording device having a conveying mechanism for conveying a non-permeable substrate in a roll-to-roll manner, which is a device as follows: a non-permeable substrate A1 in the shape of a long film wound into a roll is unwound by an unwinding device R1, and the unwound non-permeable substrate A1 is conveyed in the direction of the block arrow under a tension applied thereto, so that it passes through the pre-treatment liquid imparting device P1, the pre-treatment liquid drying area DP1, the first inkjet head IJ1, the first drying area D1, the second inkjet head IJ2 and the drying area D2 in sequence, and then is conveyed by conveying rollers T1 and T2 as conveying components, and finally is wound up by the winding device R2.

[0348] The impermeable substrate A1 may be conveyed under a tension applied thereto, and the tension may be different depending on the position in the conveying direction, or may be the same tension.

[0349] The image recording apparatus according to this example may include a tension adjustment mechanism for adjusting the tension of the impermeable substrate.

[0350] As the tension adjustment mechanism, there are:

[0351] A powder brake (Powder Brake) provided on the unwinding device R1 and / or the winding device R2;

[0352] A dancer roller disposed in the conveying path; and

[0353] A control device (e.g., a tension controller) that controls each tension by adjusting each condition of the image recording device

[0354] wait.

[0355] In addition, due to Figure 1 This is a conceptual diagram, and the conveying path of the impermeable substrate A1 is simplified. The diagram shows that the impermeable substrate A1 is conveyed in one direction between the unwinding device R1 and the conveying roller T1. However, the conveying path of the impermeable substrate A1 may be curved.

[0356] As a conveyance method of the impermeable substrate A1, various web conveyance methods such as a drum and a roll can be appropriately selected.

[0357] Relative to the unwinding device R1 for unwinding the non-permeable substrate A1, on the downstream side of the conveying direction of the non-permeable substrate A1, the pretreatment liquid applying device P1, the pretreatment liquid drying area DP1, the first inkjet head IJ1, the first drying area D1, the second inkjet head IJ2, the drying area D2, the conveying roller T1 and the conveying roller T2 are arranged in sequence from the upstream side of the conveying direction of the non-permeable substrate A1.

[0358] The pretreatment liquid applying device P1 , the first inkjet head IJ1 , and the second inkjet head IJ2 respectively apply the pretreatment liquid, apply the first ink, and apply the second ink.

[0359] At this time, at least one of heating and drying the pretreatment liquid in the pretreatment liquid drying area DP1, heating and drying the first ink in the first drying area D1, and heating and drying the second ink in the second drying area D2 may be performed.

[0360] In the first drying zone D1, in addition to heating and drying the first ink, the pre-treatment liquid can also be heated and dried substantially.

[0361] In the second drying zone D2, in addition to heating and drying the second ink, the pretreatment liquid and / or the first ink may be heated and dried. In this case, at least one of the pretreatment liquid drying zone DP1 and the first drying zone D1 may be omitted.

[0362] Furthermore, if the impermeable substrate is passed through each drying zone while the temperature of each drying zone is set to room temperature, heating and drying in each drying zone can be omitted.

[0363] In this example, the first ink is either a color ink for recording a color image or a white ink for recording a white image, and the second ink is the other of the color ink and the white ink.

[0364] Coloring ink contains water, coloring pigment and resin.

[0365] White ink contains water, white pigment and resin.

[0366] The white ink used in the image recording method of the present invention may be used as the first ink in this example, or may be used as the second ink in this example.

[0367] Relative to the pretreatment liquid imparting device P1, a surface treatment unit (not shown) for performing surface treatment (preferably corona treatment) on at least one of the front side (i.e., image recording side) and the back side (i.e., image non-recording side) of the non-permeable substrate A1 can be provided on the upstream side.

[0368] Furthermore, a cooling zone for cooling the recorded multi-color image (ie, the multi-color image including the white image and the colored image) may be provided downstream of the second drying zone D2.

[0369] The first inkjet head IJ1 and the second inkjet head IJ2 may be reciprocating inkjet heads, but from the viewpoint of increasing the speed of image recording, a line head having a plurality of ejection ports (nozzles) arranged in the width direction of the long film-shaped non-permeable substrate A1 is preferred.

[0370] The number of each of the first inkjet head IJ1 and the second inkjet head IJ2 may be only one or a plurality.

[0371] As an example of a combination of the first inkjet head IJ1 and the second inkjet head IJ2, for example, the following combination can be cited: the first inkjet head IJ1 is four inkjet heads corresponding to four colors of cyan, magenta, yellow and black (Note: these four inkjet heads are arranged along the conveying direction of the non-permeable substrate), and the second inkjet head IJ2 is one inkjet head corresponding to white (i.e., white).

[0372] Furthermore, as another example of the combination of the first inkjet head IJ1 and the second inkjet head IJ2, the following combination can also be cited: the first inkjet head IJ1 is an inkjet head corresponding to white (i.e., white), and the second inkjet head IJ2 is four inkjet heads corresponding to four colors of cyan, magenta, yellow and black (Note: these four inkjet heads are arranged along the conveying direction of the non-permeable substrate).

[0373] In inkjet recording using the image recording apparatus according to this example,

[0374] First, the long film-shaped impermeable substrate A1 wound into a roll is unwound by the unwinding device R1.

[0375] The released impermeable substrate A1 is conveyed in the direction of the block arrow under a tension.

[0376] The pretreatment liquid applying device P1 applies the pretreatment liquid to the transported non-permeable substrate A1.

[0377] Next, the pre-treatment liquid is dried in the pre-treatment liquid drying area DP1 as required.

[0378] Next, the first ink (that is, either the color ink or the white ink) is applied by the first inkjet head IJ1.

[0379] Next, the first ink is dried in the first drying area D1 as needed.

[0380] Next, the second ink (that is, the other of the color ink and the white ink) is applied by the second inkjet head IJ2.

[0381] Next, the second ink is dried in the second drying area D2 as necessary.

[0382] Thus, a multi-color image including a first image derived from the first ink (ie, one of the colored image and the white image) and a second image derived from the second ink (ie, the other of the colored image and the white image) can be obtained.

[0383] Next, the obtained multi-color image is cooled as necessary, and the impermeable substrate A1 having the multi-color image recorded thereon is transported to the winding device R2 by transport rollers T1 and T2 as transport members, and finally wound up by the winding device R2.

[0384] Of the transport rollers T1 and T2, the transport roller T1 transports the impermeable substrate A1 in contact with the front side of the impermeable substrate A1, and the transport roller T2 transports the impermeable substrate A1 in contact with the back side of the impermeable substrate A1.

[0385] The transport roller T1 is an example of a transport member disposed between application of white ink and winding of the impermeable substrate A1 and in contact with the white ink. The image recording apparatus according to this example may include a transport member other than the transport roller T1 in contact with the white ink.

[0386] The preferred range of the average contact surface pressure between the transport member and the white ink from the application of the white ink to the winding of the impermeable substrate is as described above.

[0387] In addition, the application and drying of the pretreatment liquid in this example can be omitted.

[0388] Furthermore, in this example, it is possible to record only a white image instead of a colored image.

[0389] Example

[0390] Examples of the present invention are described below, but the present invention is not limited to the following examples.

[0391] <Preparation of pretreatment solution>

[0392] The following components were mixed to prepare a pretreatment liquid.

[0393] - Composition of pretreatment solution -

[0394] Glutaric acid (coagulant)

[0395] ……6.1% by mass

[0396] Propylene glycol (PG) (water-soluble organic solvent)

[0397] ……20% by mass

[0398] ·OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.)〔Surfactant〕

[0399] ……0.5% by mass

[0400] SUPER FLEX 500M (DKS Co., Ltd.)〔Aqueous dispersion of urethane resin particles〕

[0401] ……7.0% by mass

[0402] ·Triisopropanolamine (pH adjuster)

[0403] ……0.2% by mass

[0404] BYK024 (BYK)〔Defoaming agent〕

[0405] ……0.01% by mass

[0406] Ultrapure water

[0407] ...the remainder of the pretreatment liquid is 100% by mass

[0408] <Preparation of white ink>

[0409] (Preparation of white ink W1)

[0410] The following components were mixed to prepare white ink W1.

[0411] - Composition of white ink W1 -

[0412] ·The following white pigment dispersion 1

[0413] ...The content of white pigment is 17% by mass

[0414] Propylene glycol (PG) (water-soluble organic solvent)

[0415] ……28% by mass

[0416] Propylene glycol monomethyl ether (PGmME) [water-soluble organic solvent]

[0417] ……5% by mass

[0418] ·OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.) [Acetylene glycol surfactant]

[0419] ……0.60% by mass

[0420] BYK-3450 (BYK)〔Silicone surfactant〕

[0421] ……0.75% by mass

[0422] BYK024 (BYK)〔Defoaming agent〕

[0423] ……0.02% by mass

[0424] SOLSPERSE 43000 (manufactured by The Lubrizol Corporation) [Polymer dispersant]

[0425] ……0.75% by mass

[0426] ·Joncryl JDX-6180 (manufactured by BASF)〔Water-soluble polymer〕

[0427] ……1.1% by mass

[0428] ·PVP-K15 (Polyvinylpyrrolidone K15)

[0429] ……0.12% by mass

[0430] ·SNOWTEX XS (manufactured by Nissan Chemical Corporation) [Colloidal silica dispersion]

[0431] ...The content of colloidal silica particles is 0.1% by mass

[0432] ·water

[0433] ...white ink as a whole is 100% by mass.

[0434] (Preparation of White Pigment Dispersion Liquid 1 (Containing Block Polymer Dispersant))

[0435] -Synthesis of Block Polymer Dispersant 1-

[0436] Referring to Synthesis Example 8 of Japanese Patent Application Laid-Open No. 2015-83688, a block polymer dispersant 1 was synthesized as a pigment dispersant for white pigment dispersion 1. The details are shown below.

[0437] Add the mixture to a 1L separable flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube.

[0438] Diethylene glycol dimethyl ether (266 parts by mass; polymerization solvent),

[0439] 2-iodo-2-cyanopropane (6.2 parts by mass; polymerization initiator compound),

[0440] Methyl methacrylate (MMA) (120 parts by mass; monomer),

[0441] Acrylic acid (AA) (28.8 parts by mass; monomer),

[0442] Cyclohexyl methacrylate (CHMA) (67.2 parts by mass; monomer),

[0443] Azobisdimethylisovaleronitrile (7.9 parts by mass) and

[0444] 2-tert-butyl-4,6-dimethylphenol (0.7 parts by mass; catalyst),

[0445] The mixture was stirred while nitrogen gas was flowing.

[0446] Next, the temperature of the mixture in the reaction apparatus (reaction temperature) was raised to 70° C., and polymerization was performed for 3 hours to obtain a polymerization solution A containing an MMA / AA / CHMA copolymer.

[0447] After 3 hours, a portion of the polymerization solution A was sampled and the solid content was measured. The result was 42.0% by mass, confirming that most of the monomers had been polymerized.

[0448] Furthermore, the molecular weight of the MMA / AA / CHMA copolymer was measured by GPC, and as a result, the weight average molecular weight (Mn) was 7,500.

[0449] The acid value of the MMA / AA / CHMA copolymer was 101.0 mgKOH / g.

[0450] Next, a mixture of benzyl methacrylate (BzMA) (35.2 parts by mass; monomer) and V-65 (0.3 parts by mass; radical generator) was added to the polymerization solution A and polymerized at 70° C. for 3 hours to obtain a polymerization solution B containing the block polymer dispersant 1.

[0451] Here, the block polymer dispersant 1 is a block polymer including an A block which is an MMA / AA / CHMA copolymer and a B block which is a BzMA homopolymer.

[0452] The solid content of the obtained polymerization solution B was measured and found to be 43.2% by mass, and it was confirmed that most of the monomers were polymerized.

[0453] The block polymer dispersant 1 had an Mw of 8,500 and an acid value of 89.3 mgKOH / g.

[0454] - Preparation of white pigment dispersion 1 -

[0455] The block polymer dispersant 1 (136.4 parts by mass), butyl carbitol (163.6 parts by mass) and CI Pigment White 6 (trade name "JR-405", rutile titanium dioxide particles, manufactured by TAYCA CORPORATION) (450 parts by mass) as a white pigment were blended and stirred using a disperser. Next, the white pigment was fully dispersed using a horizontal media disperser to obtain an oily pigment dispersion. The average particle size of the white pigment dispersed in the oily pigment dispersion was 290 nm. The viscosity of the oily pigment dispersion was 86.3 m3 Pa·s.

[0456] Next, while stirring the above-mentioned oily pigment dispersion (700 parts by mass) using a dispersing machine, a mixed solution consisting of potassium hydroxide (4.0 parts by mass) and water (341 parts by mass) was slowly added thereto for neutralization. Then, a horizontal media dispersing machine was used to fully disperse the white pigment, thereby obtaining a pigment dispersion.

[0457] Next, the obtained pigment dispersion was ultrafiltered by flowing ion exchange water at a flow rate of 600 mL per minute using an ultrafiltration device (cross-flow ultrafilter (UF), manufactured by Sartorius). The liquid temperature was maintained at 25° C., and 10 ultrafiltrations were performed with 1 times the volume of the prepared liquid as 1. Ion exchange water was added to obtain a white pigment dispersion 1 having a concentration of 45% by mass of white pigment and a concentration of 3.7% by mass of block polymer dispersant 1.

[0458] (Preparation of white ink W2)

[0459] White ink W2 was prepared in the same manner as white ink W1 except that NEOCRYL A1091 (manufactured by Covestro Coating Resins) [aqueous dispersion of styrene acrylic resin particles] (content of styrene acrylic resin particles: 0.75% by mass) was added to the white ink.

[0460] (Preparation of white ink W3)

[0461] In the preparation of the white ink, white ink W3 was prepared in the same manner as white ink W1, except that NEOCRYL A1091 (manufactured by Covestro Coating Resins) [aqueous dispersion of styrene acrylic resin particles] was added (the content of styrene acrylic resin particles was 1.85% by mass) and Joncryl JDX-6180 (manufactured by BASF) was not used.

[0462] (Preparation of white ink W4)

[0463] White ink W4 was prepared in the same manner as in the preparation of white ink W2 except that the following white pigment dispersion 2 (containing a random polymer dispersant) was used instead of white pigment dispersion 1 (containing a block polymer dispersant).

[0464] (Preparation of White Pigment Dispersion Liquid 2 (Containing Random Polymer Dispersant))

[0465] -Synthesis of Random Polymer Dispersant 1-

[0466] 965 g of dipropylene glycol was added to a 5000 mL three-necked flask equipped with a stirrer and a cooling tube, and the mixture was heated to 85° C. under a nitrogen atmosphere.

[0467] Prepared respectively:

[0468] 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

[0469] Solution II was obtained by dissolving 17.69 g of tert-butyl peroxy(2-ethylhexanoate) (product name "PERBUTYL O", manufactured by NOF CORPORATION) in 221.17 g of dipropylene glycol.

[0470] Solution I was added dropwise to the three-necked flask over 4 hours, and solution II was added dropwise over 5 hours. After the addition was completed, they were allowed to react for a further 2 hours. 1 H-NMR confirmed the disappearance of the monomer.

[0471] The obtained reaction solution was heated to 70° C., 248.02 g of a 50% by mass potassium hydroxide aqueous solution was added thereto, and then 107.48 g of dipropylene glycol and 75.52 g of pure water were added thereto and stirred to obtain a 37% by mass solution of the random polymer dispersant 1.

[0472] pass 1 H-NMR confirmed the structural units constituting the obtained random polymer dispersant 1. Furthermore, the weight average molecular weight (Mw) was determined by GPC. The weight average molecular weight (Mw) of the obtained random polymer dispersant 1 was 8400, and the acid value was 221.7 mgKOH / g.

[0473] - Preparation of White Pigment Dispersion 2 (Containing Random Polymer Dispersant) -

[0474] The random polymer dispersant 1 (150 parts by mass) was dissolved in water to prepare a polymer solution having a random polymer dispersant 1 concentration of 25% by mass.

[0475] 96 parts by mass of the polymer solution, 300 parts by mass of CI Pigment White 6 (trade name "JR-405", rutile titanium dioxide particles, manufactured by TAYCA Co., Ltd.) as a white pigment, and 270 parts by mass of water were mixed to obtain a mixed solution. A potassium hydroxide aqueous solution was added to the obtained mixed solution to adjust the pH after neutralization to 8.7.

[0476] Next, the neutralized mixed solution was dispersed for 3 hours using a bead mill (bead diameter: 0.1 mmφ, zirconia beads), thereby obtaining a white pigment dispersion A (uncrosslinked dispersion) PD1 in which a white pigment was dispersed in the pigment dispersant P1.

[0477] Next, the obtained white pigment dispersion (uncrosslinked dispersion) PD1 was ultrafiltered using an ultrafiltration device (cross-flow ultrafilter (UF), manufactured by Sartorius) by flowing ion exchange water at a flow rate of 600 mL per minute. The liquid temperature was maintained at 25° C., and 1 times the volume of the prepared liquid was taken as 1 time, and ultrafiltration was performed 3 times. Ion exchange water was added to the ultrafiltered liquid to obtain a white pigment dispersion 2 having a concentration of 45% by mass of white pigment and a concentration of 3.6% by mass of random polymer dispersant 1.

[0478] <Viscosity measurement of white ink and concentrated ink>

[0479] The viscosity of each of the white inks W1 to W4 and the viscosity of the concentrated ink (X) were measured, and the concentration thickening ratio (%) was calculated from the viscosity and the viscosity of the concentrated ink.

[0480] Table 1 shows these results.

[0481] These viscosities were measured using a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd. under the condition of 32°C.

[0482] Also, the concentrated ink was prepared by heating the white ink and distilling off the solvent (ie, water and a water-soluble organic solvent) until the mass was reduced by 30%.

[0483] [Table 1]

[0484]

[0485] <Preparation of Colored Ink>

[0486] As color inks, cyan ink, black ink, magenta ink, and yellow ink were prepared.

[0487] Each ink was prepared by mixing the components in the composition of each ink shown below.

[0488] -Composition of cyan ink-

[0489] ·APD4000 Cyan (manufactured by Fujifilm Imaging Colorants Ltd.)〔Cyan pigment dispersion〕

[0490] ...with a cyan pigment content of 4.0% by mass

[0491] Propylene glycol monomethyl ether (PGmME) [water-soluble organic solvent]

[0492] ……3% by mass

[0493] Propylene glycol (PG) (water-soluble organic solvent)

[0494] ……20% by mass

[0495] Neocryl A-1105 (manufactured by DSM) [Acrylic resin particle dispersion]

[0496] ...The content of the resin particles is 5.0% by mass

[0497] ·OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.) [Acetylene glycol surfactant]

[0498] ……1.0% by mass

[0499] BYK3450 (manufactured by BYK)〔Silicone surfactant〕

[0500] ……1.0% by mass

[0501] PVPK15 (Polyvinylpyrrolidone K15)

[0502] ……0.15% by mass

[0503] ·ST-XS (manufactured by Nissan Chemical Corporation) [Colloidal silica dispersion]

[0504] ...The content of colloidal silica particles is 0.05% by mass

[0505] ·water

[0506] ...The remainder of the total ink is 100% by mass

[0507] - Composition of black ink -

[0508] APD4000 Black (manufactured by Fujifilm Imaging Colorants Ltd.)

[0509] ...The content of pigment is 4.0% by mass

[0510] Propylene glycol (PG) (water-soluble organic solvent)

[0511] ……20% by mass

[0512] Propylene glycol monomethyl ether (water-soluble organic solvent)

[0513] ……1.0% by mass

[0514] Neocryl A-1105 (acrylic resin particle dispersion) (manufactured by DSM)

[0515] ...The content of the resin particles is 5.0% by mass

[0516] Olfine E1010 (acetylene glycol surfactant manufactured by Nissin Chemical Co., Ltd.)

[0517] ……1.0% by mass

[0518] BYK3450 (silicone surfactant manufactured by BYK)

[0519] ……1.0% by mass

[0520] PVPK15 (Polyvinylpyrrolidone K15)

[0521] ……0.15% by mass

[0522] ·ST-XS (colloidal silica dispersion) (manufactured by Nissan Chemical Corporation)

[0523] ...The content of colloidal silica particles is 0.05% by mass

[0524] ·water

[0525] ...The remainder of the total ink is 100% by mass

[0526] - Composition of magenta ink -

[0527] APD4000 Magenta (manufactured by Fujifilm Imaging Colorants Ltd.)

[0528] ...The content of pigment is 5.0% by mass

[0529] Propylene glycol (PG) (water-soluble organic solvent)

[0530] ……20% by mass

[0531] Propylene glycol monomethyl ether (water-soluble organic solvent)

[0532] ……1.0% by mass

[0533] Neocryl A-1105 (acrylic resin particle dispersion) (manufactured by DSM)

[0534] ...The content of the resin particles is 5.0% by mass

[0535] Olfine E1010 (acetylene glycol surfactant manufactured by Nissin Chemical Co., Ltd.)

[0536] ……1.0% by mass

[0537] BYK3450 (silicone surfactant manufactured by BYK)

[0538] ……1.0% by mass

[0539] PVPK15 (Polyvinylpyrrolidone K15)

[0540] ……0.15% by mass

[0541] ·ST-XS (colloidal silica dispersion) (manufactured by Nissan Chemical Corporation)

[0542] ...The content of colloidal silica particles is 0.05% by mass

[0543] ·water

[0544] ...The remainder of the total ink is 100% by mass

[0545] -Preparation of yellow ink-

[0546] ·APD4000 Yellow (manufactured by Fujifilm Imaging Colorants Ltd.)

[0547] ...The content of pigment is 4.0% by mass

[0548] Propylene glycol (PG) (water-soluble organic solvent)

[0549] ……20% by mass

[0550] Propylene glycol monomethyl ether (water-soluble organic solvent)

[0551] ……1.0% by mass

[0552] Neocryl A-1105 (acrylic resin particle dispersion) (manufactured by DSM)

[0553] ...The content of the resin particles is 5.0% by mass

[0554] Olfine E1010 (acetylene glycol surfactant manufactured by Nissin Chemical Co., Ltd.)

[0555] ……1.0% by mass

[0556] BYK3450 (silicone surfactant manufactured by BYK)

[0557] ……1.0% by mass

[0558] PVPK15 (Polyvinylpyrrolidone K15)

[0559] ……0.15% by mass

[0560] ·ST-XS (colloidal silica dispersion) (manufactured by Nissan Chemical Corporation)

[0561] ...The content of colloidal silica particles is 0.05% by mass

[0562] ·water

[0563] ...The remainder of the total ink is 100% by mass

[0564] <Preparation of image recording equipment>

[0565] As an image recording device, the aforementioned Figure 1 The image recording device shown.

[0566] As the pretreatment liquid applying device P1, a gravure coater was used.

[0567] The drying method in the pretreatment liquid drying zone DP1 is set to warm air drying.

[0568] As the first inkjet head IJ1, four inkjet heads, namely, a cyan inkjet head, a magenta inkjet head, a yellow inkjet head, and a black inkjet head, are arranged in this order from the upstream side (ie, the upstream side in the conveyance direction of the non-permeable substrate).

[0569] As the second inkjet head IJ2, a white inkjet head is arranged.

[0570] All inkjet heads and ink ejection conditions were as follows.

[0571] Inkjet head: A piezo full line head with a 1200 dpi (dot per inch: dots per inch, 1 inch is 2.54 cm) / 20 inch width (total number of nozzles: 2048) was used.

[0572] Ink ejection volume: set to 3.0 pL.

[0573] Drive frequency: set to 30kHz.

[0574] The drying method in the first drying zone D1 and the drying method in the second drying zone D2 are both set to warm air drying. The drying method in the second drying zone D2 is set to be switchable to infrared (IR) drying or heated drum drying.

[0575] As the transport roller T1 and the transport roller T2, anodized aluminum rollers (roller radius: 0.05 m) were used.

[0576] <Preparation of non-permeable substrate>

[0577] As an impermeable substrate, a polyethylene terephthalate (PET) substrate "Taikoku polyester film (thickness 25 μm)" manufactured by FUTAMURA CHEMICAL CO., LTD. was prepared.

[0578] The "Taikoku polyester film (thickness 25 μm)" is a roll body obtained by winding a long strip-shaped PET substrate having a thickness of 25 μm and a width of 800 mm into a roll shape.

[0579] [Test No. 1 to 44]

[0580] <Image Record>

[0581] The following inkjet recording was performed using the image recording apparatus, the pretreatment liquid, and the white ink as the second ink to obtain an image recorded material on a non-permeable substrate with a white image.

[0582] In this image recording, the color ink (that is, cyan ink, black ink, magenta ink, and yellow ink) as the first ink is not used.

[0583] As the second ink, any one of the white inks W1 to W4 described above was used (see Table 2 and Table 3).

[0584] First, the impermeable substrate is unwound from a roll by an unwinding device W1.

[0585] The released impermeable substrate is transported under tension.

[0586] The pretreatment liquid is applied to the front surface of the conveyed non-permeable substrate by a gravure coater as the pretreatment liquid applying device P1.

[0587] Next, the pretreatment liquid is dried in the pretreatment liquid drying area DP1.

[0588] Next, the second inkjet head IJ2 applies white ink as the second ink.

[0589] Next, the white ink as the second ink is dried in the second drying area D2.

[0590] Through the above operation, a white image was recorded on the front surface of the conveyed impermeable substrate, thereby obtaining an impermeable substrate with a white image, that is, an image recorded material.

[0591] Next, the obtained image recorded material is conveyed by the conveying rollers T1 and T2 and is wound up by the winding device W2 .

[0592] In the above inkjet recording, the conveying speed of the non-permeable substrate was set to 50 m / min.

[0593] The amount of pretreatment liquid applied was set to 3.0 g / m 2 .

[0594] The drying conditions of the pretreatment liquid were set to a warm air temperature of 80° C., a warm air velocity of 20 m / sec, and a drying time of 3 sec.

[0595] The amount of the second ink (white ink) applied was set to 3.0 g / m 2 .

[0596] The drying method and drying conditions (ie, the temperature increase rate, and the temperature and pressure of the warm air) of the second ink (white ink) are shown in Tables 2 and 3. The drying time was fixed at 40 seconds.

[0597] The temperature rise rate is the rate of increase in the surface temperature from the start of heat drying to the time when 5 seconds have passed. The temperature rise rate was measured by measuring the surface temperature of the white ink applied to the front surface of the non-permeable substrate.

[0598] <Measurement of dry film thickness and wet film thickness>

[0599] The film thickness of the white ink on the front side of the non-permeable substrate after the white ink is applied by the second inkjet head IJ2 and before drying in the second drying area D2 (wet film thickness (μm); B) is calculated based on the ejection volume [pL / pixel] and resolution of the ink ejected from the inkjet head in μm units as a value with two decimal places.

[0600] The film thickness of the white ink on the front side of the non-permeable substrate (dry film thickness (μm); A) was measured in μm units as a numerical value with two decimal places by unwinding the image recorded material from the wound image recorded material and taking a cross-sectional SEM image of the unwound image recorded material (magnification 10,000 times).

[0601] The value (A / B) was obtained by dividing the dry film thickness (A) by the wet film thickness (B).

[0602] These results are shown in Tables 2 and 3.

[0603] <Contact surface pressure with conveyor roller T1>

[0604] The contact surface pressure (N / m) between the white image and the conveying roller T1 was calculated by dividing the tension (N / m) of the impermeable substrate at the conveying roller T1 by the radius of the conveying roller T1 (i.e., 0.05 m). 2 ).

[0605] The results are shown in Tables 2 and 3.

[0606] <Evaluation>

[0607] The following evaluation was performed on the white image obtained by the above-mentioned image recording.

[0608] The results are shown in Tables 2 and 3.

[0609] In the remarks column of Table 2 and Table 3, "Ex." and "Com." respectively indicate an Example and a Comparative Example (the same applies to Tables 4 and thereafter).

[0610] (Concealment)

[0611] The image recorded material was placed on the black part of the concealment test paper (JIS qualified product) manufactured by TP Giken Co., Ltd. in such a direction that the white image in the image recorded material was in contact with the black part, and the hiding power (%) of the white image was measured. The hiding power was measured using the x-rite eXact Advanced of X-Rite, Inc. (see https: / / www.xrite.co.jp / allproduct / qa / 99-exact / 588-pqa0111.html).

[0612] In the following evaluation criteria, the most excellent concealment level is A.

[0613] -Evaluation criteria for concealment-

[0614] A: The hiding power is 56.0% or more.

[0615] B: The hiding power is 54.5% or more and less than 56.0%.

[0616] C: The hiding power is 53.0% or more and less than 54.5%.

[0617] D: The hiding power is less than 53.0%.

[0618] (Adhesion)

[0619] The white image in the image recorded material was subjected to a cross hatch test in accordance with ISO 2409 (cross cut method), and the adhesion of the image was evaluated according to the following evaluation criteria.

[0620] In the following evaluation criteria, the most excellent image adhesion was rated as “A”.

[0621] In the 100-grid test, 25 square grids of 1 mm square were formed with a cutting interval of 1 mm.

[0622] In the following evaluation criteria, the ratio (%) of the lattices peeled off is a value obtained by the following formula: The total number of lattices in the following formula is 25.

[0623] The ratio of the peeled grid (%) = [(the number of peeled grids) / (the total number of grids)] × 100

[0624] In the following evaluation criteria, the most excellent adhesion was graded as A.

[0625] -Evaluation criteria for tightness-

[0626] A: The ratio (%) of the lattice peeling is 0% or more and 5% or less.

[0627] B: The ratio (%) of the lattice peeling is more than 5% and 15% or less.

[0628] C: The ratio (%) of the lattice peeling is more than 15% and is 35% or less.

[0629] D: The ratio (%) of the lattice peeling exceeds 35%.

[0630] (Unevenness within the surface)

[0631] The hiding power (%) of the white image was measured at 10 points in the width direction of the image recorded material by the above-mentioned hiding power measuring method. The maximum and minimum hiding power values ​​at the obtained 10 points were determined, and the value obtained by subtracting the minimum value from the maximum value was defined as Δ. Based on the value of Δ, the in-plane unevenness of the white image was evaluated according to the following evaluation criteria.

[0632] In the following evaluation criteria, the most excellent level in suppressing the in-plane unevenness was rated as A.

[0633] -Evaluation criteria for in-plane unevenness-

[0634] A: Δ less than 1.0

[0635] B: Δ is 1.0 or more and less than 2.0

[0636] C: Δ is 2.0 or more and less than 3.0

[0637] D: Δ is 3.0 or more

[0638] (Abrasion resistance)

[0639] The white image in the image recorded material was repeatedly rubbed with a paperweight wrapped with rubbing paper. OK TopKote 104 (manufactured by OOji Paper Co., Ltd.) was used as the rubbing paper. The rubbing operation was performed with a weight of 4.0N applied.

[0640] The color transfer from the solid image to the friction paper was observed with naked eyes, and the abrasion resistance of the image was evaluated according to the following evaluation criteria.

[0641] In the following evaluation criteria, the image most excellent in abrasion resistance was rated "A".

[0642] -Evaluation criteria for wear resistance-

[0643] A: At the point in time when 200 rubbing operations were completed, color shift from the solid image to the rubbing paper was not visually recognized.

[0644] B: At the time point when 200 rubbing operations were completed, color shift from the solid image to the rubbing paper was visually recognized, but at the time point when 100 rubbing operations were completed, color shift from the solid image to the rubbing paper was not visually recognized.

[0645] C: Color shift from the solid image to the rubbing paper was visually recognized at the time point when 100 rubbing operations were completed, but color shift from the solid image to the rubbing paper was not visually recognized at the time point when 20 rubbing operations were completed.

[0646] D: At the point in time when 20 rubbing operations were completed, color shift from the white image to the rubbing paper was visually recognized.

[0647] [Test No. 101-106]

[0648] The same operation as in Test No. 2 was performed except that the white ink shown in Table 4 was used as the white ink and the amount of the white ink applied was adjusted so that the wet film thickness (μm) became the value shown in Table 4.

[0649] The results are shown in Table 4.

[0650] [Test No. 201-228]

[0651] The same operation as in Test No. 2 was performed except that the conditions of the hot air drying (the temperature of the hot air and the wind speed of the hot air) were changed as shown in Table 5.

[0652] The results are shown in Table 5.

[0653] [Test No. 301-306]

[0654] The same operation as in Test No. 2 was performed except that the contact surface pressure between the white image and the transport roller T1 was changed as shown in Table 6 by adjusting the tension applied to the non-permeable substrate.

[0655] The results are shown in Table 6.

[0656] [Table 2]

[0657]

[0658] [Table 3]

[0659]

[0660] [Table 4]

[0661]

[0662] [Table 5]

[0663]

[0664] [Table 6]

[0665]

[0666] As shown in Tables 2 to 6, the examples (Ex.) having a product (X*Y) of 30 to 280 have excellent concealment of the white image compared to the comparative example (Com.) having a product (X*Y) of less than 30. It can be seen from Test No. 1 (Comparative Example) and Test Nos. 2, 5, 9 and 13 (all Examples) that the concealment effect can be obtained by making the product (X*Y) 30 or more regardless of the drying method.

[0667] Furthermore, each of the Examples (Ex.) has excellent adhesion of the white image compared to the Comparative Example (Com.) in which the product (X*Y) exceeds 280. As can be seen from Test No. 44 (Comparative Example) and Test Nos. 32, 36, 40, and 43 (all Examples), the effect of improving adhesion can be obtained by making the product (X*Y) 280 or less, regardless of the drying method.

[0668] For example, as can be seen from the comparison between Test No. 2 and Test No. 3, when the product (X*Y) is 40 or more, the concealment of the white image is further improved.

[0669] For example, as can be seen from the comparison between Test No. 33 and Test No. 34, when the product (X*Y) is 200 or less, the adhesion of the white image is further improved.

[0670] For example, from the comparison of test numbers 8, 12, and 16, it can be seen that when the heating and drying method is warm air drying, the abrasion resistance of the white image is further improved compared with the case where the heating and drying method is IR drying and heated drum drying.

[0671] For example, from the comparison between Test No. 205 and Test No. 206, it can be seen that when the heating drying method is warm air drying, when the product (X*Z) is 2.0 or more, the abrasion resistance of the white image is further improved.

[0672] For example, from the comparison between Test No. 214 and Test No. 215, it can be seen that when the heating drying method is warm air drying, when the product (X*Z) is 10.0 or less, the in-plane unevenness of the white image is further suppressed.

[0673] For example, from the comparison between Test No. 209 and Test No. 210, it can be seen that when the heating drying method is warm air drying, when the product (X*Z) is 3.5 or more, the abrasion resistance of the white image is further improved.

[0674] For example, from the comparison between Test No. 215 and Test No. 216, it can be seen that when the heating drying method is warm air drying, when the product (X*Z) is 7.5 or less, the in-plane unevenness of the white image is further suppressed.

[0675] For example, from the comparison between Test No. 11 and Test No. 12, it can be seen that when A / B, which is a value obtained by dividing the dry film thickness of the white ink by the wet film thickness, is 0.20 or less, the adhesion of the white image is further improved.

[0676] For example, as can be seen from the comparison between Test No. 29 and Test No. 30, when the dry film thickness of the white ink is 1.30 μm or more, the concealability of the white image is further improved.

[0677] For example, as can be seen from the comparison between Test No. 28 and Test No. 32, when the dry film thickness of the white ink is 1.80 μm or less, the adhesion of the white image is further improved.

[0678] For example, from the comparison between test number 305 and test number 306, it can be seen that when the contact surface pressure between the conveying roller T1 and the white ink is 4000 N / m 2 When the value is below , the concealment of the white image is further improved.

[0679] Although the evaluation is omitted, when the contact surface pressure between the conveying roller T1 and the white ink is 750 N / m 2 In the above case, the transport performance by the transport roller T1 is further improved.

[0680] In the above embodiment, a white image is recorded using the pretreatment liquid and the white ink as the second ink without using the colored ink (ie, cyan ink, black ink, magenta ink, and yellow ink) as the first ink.

[0681] In these embodiments, when at least one of the colored inks (i.e., cyan ink, black ink, magenta ink, and yellow ink) is used as the first ink to record a colored pattern image (characters, graphics, etc.), and then a white image (solid image) is recorded as a background image using a white ink as the second ink so as to cover the colored pattern image, a white image with excellent concealment and adhesion can be obtained as in the above-mentioned embodiments. In this case, when the first ink is set as the white ink and the second ink is set as the colored ink, a white image with excellent concealment and adhesion can be obtained as in the above-mentioned embodiments.

[0682] Furthermore, in the above-described embodiment, even when the application of the pre-treatment liquid is omitted, a white image with excellent concealability and adhesion can be obtained as in the above-described embodiment.

[0683] The disclosure of Japanese Patent Application No. 2022-150263 filed on September 21, 2022 is incorporated into this specification by reference in its entirety.

[0684] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually described as being incorporated by reference.

Claims

1. An image recording method, comprising: The recording step includes applying white ink containing water, white pigment and resin to one surface of the non-permeable substrate by inkjet method, and heating and drying the applied white ink to record a white image. When the viscosity of the concentrated ink obtained by concentrating the white ink to reduce its mass by 30% at 32°C is X mPa·s and the temperature increase rate from the start of the heat drying to 5 seconds is Y°C / s, the product of X and Y is 30-280.

2. The image recording method according to claim 1, wherein: The product of X and Y is 40-200.

3. The image recording method according to claim 1, wherein: The heating and drying is performed by blowing warm air, and when a value obtained by dividing a wind speed of the warm air in m / s by a temperature of the warm air in ° C. is defined as Z, a product of X and Z is 2.0 to 10.

0.

4. The image recording method according to claim 3, wherein: The product of X and Z is 3.5 to 7.

5.

5. The image recording method according to claim 1, wherein: A value obtained by dividing the film thickness of the white ink applied to one surface of the impermeable substrate after the heat drying by the film thickness of the white ink applied to one surface of the impermeable substrate before the heat drying is 0.10 to 0.

20.

6. The image recording method according to claim 5, wherein: The film thickness of the white ink applied to one surface of the impermeable substrate after the heat drying is 1.30 μm to 1.80 μm.

7. The image recording method according to claim 1, wherein: The recording step further includes a step of conveying the impermeable substrate to which the white ink is applied by a conveying member in a configuration where the conveying member contacts the white ink. After the recording step, the method further includes a winding step of winding up the non-permeable substrate on which the white image is recorded. The average contact surface pressure between the transport member and the white ink from the start of application of the white ink to the winding of the impermeable substrate was 750 N / m 2 ~4000N / m 2 .

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

9. The image recording method according to claim 8, wherein: The colored image is recorded before the white image and is disposed between the non-permeable substrate and the white image.

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

11. An image recording device, used in the image recording method according to any one of claims 1 to 10, the image recording device comprising: An inkjet head for imparting the white ink to one surface of the non-permeable substrate; and A heating and drying device is used to heat and dry the applied white ink. The product of X and Y is 30-280.

Images