Inkjet recording method and inkjet recording apparatus

Abstract

An ink jet recording method includes a step of applying ink to a conveyed recording medium and heating and drying the applied ink, and heating and drying the ink using a heating and drying device including a heating roller and a guide roller in contact with the ink applied to the recording medium. The ink contains water, a pigment, a resin and a wax, the total content of the pigment, the resin and the wax is 5.0-11.0 mass% with respect to the total amount of the ink, the drying temperature of the ink during heating and drying is 120 DEG C or more and the melting point of the wax or less, and the ratio RaX / Cw of the content Cw mass% of the wax with respect to the total amount of the ink and the surface roughness Ra of the outer peripheral surface of the guide roller is 1.0-4.0.

Description

Technical Field

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus. Background Art

[0002] Various studies related to inkjet recording methods have been conducted.

[0003] For example, Patent Document 1 discloses a drying device that can be used for drying ink in an inkjet recording method, and dries a drying object to which a liquid is applied and conveyed as a drying device capable of shortening the drying time. The drying device includes: one or more first heating members that heat the drying object; and one or more second heating members that heat the drying object heated by the first heating member. One or more of the first heating members include a first heating member having a heating temperature higher than that of the second heating member. Patent Document 1 also discloses at least one guide roller that contacts the liquid application surface of the drying object to which the liquid is applied and guides the drying object.

[0004] In addition, Patent Document 2 discloses a printing device including: a printing unit that attaches ink to a printing surface of a long printing medium being conveyed; and a drying mechanism that heats the printing medium carried out from the printing unit to dry the ink. The drying mechanism includes: at least first to fourth direction-changing rollers that contact the back surface of the printing medium carried out from the printing unit where no ink is attached and change the conveyance direction of the printing medium; a printing surface contact roller that is disposed on the downstream side in the conveyance direction of the fourth direction-changing roller, contacts the printing surface of the printing medium, and changes the conveyance direction of the printing medium; and at least first to third heating units that heat the printing medium guided by the first to fourth direction-changing rollers and the printing surface contact roller.

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-16355

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2022-037537 Summary of the Invention

[0007] Technical Problem to be Solved by the Invention

[0008] When using a heat drying device including a guide roller that contacts ink applied to a recording medium (for example, the drying device described in Patent Document 1 and the drying mechanism described in Patent Document 2 above) and performing high-speed inkjet recording (specifically, inkjet recording in which the conveyance speed of the recording medium is fast and the heating temperature during heat drying of the ink is high), it is sometimes difficult to balance suppressing a decrease in ejection performance from the inkjet head and suppressing scratches in the obtained image (hereinafter, also referred to as image scratches).

[0009] An object of one aspect of the present invention is to provide an inkjet recording method and an inkjet recording apparatus capable of suppressing a decrease in ink ejection performance and suppressing image scratches.

[0010] Means for Solving the Technical Problem

[0011] The present invention includes the following aspects.

[0012] <1> An inkjet recording method, comprising the steps of:

[0013] while conveying a recording medium at a conveyance speed of 60 m / min or more, applying ink to the recording medium by an inkjet method; and

[0014] while conveying the recording medium to which ink has been applied at a conveyance speed of 60 m / min or more, heating and drying the ink applied to the recording medium to obtain an image,

[0015] The heating and drying is performed using a heating and drying device,

[0016] The heating and drying device includes:

[0017] a heating roller that contacts a non-ink-applied surface of the recording medium to which ink has been applied and heats the ink applied to the recording medium through the recording medium; and

[0018] a guide roller that contacts an ink-applied surface of the recording medium to which ink has been applied and guides the recording medium to which ink has been applied,

[0019] The ink contains water, a pigment, a resin, and wax,

[0020] The total content of the pigment, resin, and wax relative to the total amount of the ink is 5.0% by mass to 11.0% by mass,

[0021] The drying temperature of the ink during heating and drying is 120°C or higher and lower than the melting point of the wax,

[0022] When the content of wax relative to the total amount of the ink is set to Cw% by mass and the arithmetic mean roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is set to RaX μm, the RaX / Cw ratio is 1.0 to 4.0.

[0023] <2> The inkjet recording method according to <1>, wherein when the content of wax relative to the total amount of the ink is set to Cw% by mass and the total content of the pigment, resin, and wax relative to the total amount of the ink is set to Ct% by mass, the Cw / Ct ratio is 0.10 to 0.30.

[0024] <3> The inkjet recording method according to <1> or <2>, wherein when the content of wax relative to the total amount of the ink is Cw mass% and the content of resin relative to the total amount of the ink is Cp mass%, the Cw / Cp ratio is 0.50 to 1.50.

[0025] <4> The inkjet recording method according to any one of <1> to <3>, wherein the dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.03 to 0.10.

[0026] <5> The inkjet recording method according to any one of <1> to <4>, wherein the guide roller includes a surface layer containing a fluororesin.

[0027] <6> The inkjet recording method according to any one of <1> to <5>, wherein the conveyance speeds of the recording medium during ink application and during heat drying are both 100 m / min or more.

[0028] <7> The inkjet recording method according to any one of <1> to <6>, wherein in the TOF-SIMS analysis of the surface of the image, the peak intensity of wax is stronger than the peak intensity of the pigment.

[0029] <8> The inkjet recording method according to any one of <1> to <7>, wherein

[0030] the resin contains resin particles,

[0031] the content of the resin particles relative to the total amount of the ink is 0.3 mass% to 5.0 mass%.

[0032] <9> An inkjet recording apparatus for the inkjet recording method according to any one of <1> to <8>, and including an inkjet head for applying the above-mentioned ink to the above-mentioned recording medium and the above-mentioned heat drying apparatus.

[0033] Effects of the Invention

[0034] According to one aspect of the present invention, there is provided an inkjet recording method and an inkjet recording apparatus capable of suppressing a decrease in the ejection property of ink and capable of suppressing image scratches. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a diagram conceptually showing an example of an inkjet recording apparatus used in the inkjet recording method of the present invention.

[0036] Figure 2 is Figure 1 an enlarged explanatory view of the heat drying apparatus in the inkjet recording apparatus related to the example shown. DETAILED DESCRIPTION

[0037] In this specification, the numerical range indicated by "~" means a range that includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0038] In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the upper limit value or the lower limit value of another numerically described range. Moreover, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range can also be replaced with the value shown in the examples.

[0039] In this specification, regarding the amounts of the respective components in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition.

[0040] In this specification, a combination of two or more preferred modes is a more preferred mode.

[0041] In this specification, the term "process" includes not only independent processes, but also, even when it cannot be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved, it is also included in this term.

[0042] In this specification, "image" refers to all films, and "image recording" refers to the formation of an image (i.e., a film). Moreover, the concept of "image" in this specification also includes a solid image.

[0043] In this specification, "(meth)acrylate" is a concept that includes both acrylate and methacrylate, and "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid.

[0044] 〔Inkjet recording method〕

[0045] The inkjet recording method of the present invention (hereinafter, also simply referred to as "recording method") is the following inkjet recording method, which includes the following steps:

[0046] A step of conveying a recording medium at a conveyance speed of 60 m / min or more and, at the same time, applying ink to the recording medium by an inkjet method; and

[0047] A step of conveying the recording medium to which ink has been applied at a conveyance speed of 60 m / min or more and, at the same time, heating and drying the ink applied to the recording medium to obtain an image,

[0048] The heating and drying is performed using a heating and drying device.

[0049] The heating and drying device includes:

[0050] A heating roller that contacts the non-ink-applied surface of a recording medium with ink applied thereto and heats the ink applied to the recording medium through the recording medium; and

[0051] A guide roller that contacts the ink-applied surface of a recording medium with ink applied thereto and guides the recording medium with ink applied thereto,

[0052] The ink contains water, a pigment, a resin, and wax,

[0053] The total content of the pigment, resin, and wax relative to the total amount of the ink is 5.0 mass% to 11.0 mass%,

[0054] The drying temperature of the ink during heat drying is 120°C or higher and below the melting point of the wax,

[0055] When the content of wax relative to the total amount of the ink is set to Cw mass% and the average roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is set to RaX μm, the RaX / Cw ratio is 1.0 to 4.0.

[0056] In the recording method of the present invention, when using a heat drying device including the above guide roller and performing high-speed inkjet recording (specifically, inkjet recording with a conveyance speed of the recording medium of 60 m / min or more and a heating temperature during heat drying of the ink of 120°C or more), it is possible to suppress a decrease in the ejection property of the ink from the inkjet head and to suppress image scratches (i.e., scratches in the obtained image).

[0057] Specifically, in the recording method of the present invention, by setting the total content of the pigment, resin, and wax relative to the total amount of the ink to 11.0 mass% or less, a decrease in the ejection property of the ink can be suppressed.

[0058] Moreover, in the recording method of the present invention, by setting the drying temperature of the ink during heat drying to be below the melting point of the wax, image scratches can be suppressed. It is considered that the reason is that when the drying temperature of the ink with a total content of the pigment, resin, and wax of 11.0 mass% or less exceeds the melting point of the wax, the wax penetrates into the interior of the ink film (i.e., the film formed by the ink applied to the recording medium. The same applies hereinafter). As a result, the pigment is exposed on the surface of the ink film, and the dynamic friction coefficient of the ink film sometimes increases. In contrast, in the recording method of the present invention, it is considered that by setting the drying temperature of the ink to be below the melting point of the wax, the phenomenon of the wax penetrating into the interior of the ink film can be suppressed, and as a result, image scratches can be suppressed.

[0059] Furthermore, in the recording method of the present invention, by setting the RaX / Cw ratio to 1.0 or more, a decrease in the ejection property of the ink can be suppressed. It is considered that the reason is that when the RaX / Cw ratio is 1.0 or more, the content of wax relative to the total amount of the ink, i.e., Cw mass%, decreases.

[0060] Further, in the recording method of the present invention, image scratches can be suppressed by setting the RaX / Cw ratio to 4.0 or less. It is considered that the reason is that when the RaX / Cw ratio is 4.0 or less, the surface roughness Ra of the outer peripheral surface of the guide roller, namely RaX, decreases, and as a result, the dynamic friction coefficient of the outer peripheral surface of the guide roller decreases.

[0061] <Heating and Drying Device X>

[0062] The heating and drying device (hereinafter, also referred to as "heating and drying device X") used in the recording method of the present invention includes:

[0063] a heating roller that contacts the non-ink-applied surface of the recording medium with ink applied thereto and heats the ink applied to the recording medium through the recording medium; and

[0064] a guide roller that contacts the ink-applied surface of the recording medium with ink applied thereto and guides the recording medium with ink applied thereto.

[0065] As described above, in the recording method using the heating and drying device X, image scratches sometimes occur due to the guide roller that contacts the ink-applied surface.

[0066] In this regard, in the recording method of the present invention, although it is a recording method using the heating and drying device X, image scratches can be suppressed.

[0067] The following conditions are considered to contribute to the effect of suppressing image scratches by the recording method of the present invention:

[0068] The ink contains wax;

[0069] The drying temperature of the ink is equal to or lower than the melting point of the wax; and

[0070] The RaX / Cw ratio is 4.0 or less.

[0071] As an example of the heating and drying device X, the following heating and drying device X1 can be cited.

[0072] The heating and drying device X1 includes a plurality of heating rollers,

[0073] and further includes the following conveying path as the conveying path for conveying the recording medium with ink applied thereto:

[0074] a first conveying path through which the recording medium with ink applied thereto is conveyed while contacting the plurality of heating rollers; and

[0075] a second conveying path through which the recording medium after passing through the first conveying path is conveyed while contacting at least one of the plurality of heating rollers that contacted on the first conveying path again through the guidance of the guide roller.

[0076] The heating and drying device X1 can efficiently heat and dry the ink by including a second transfer path that is transferred while contacting at least one of the plurality of heating rollers that contact again on the first transfer path.

[0077] Therefore, the heating and drying device X1 is advantageous in terms of miniaturization of the size of the heating and drying device, shortening of the heating and drying time (for example, high-speed transfer speed), etc.

[0078] The heating and drying device X1 may further include a heating drum that contacts the non-ink-applied surface of the recording medium with ink applied thereto between the first transfer path and the second transfer path and heats the ink applied to the recording medium through the recording medium.

[0079] Thereby, the heating and drying of the ink can be performed more efficiently.

[0080] When the heating and drying device X1 includes a heating drum, the heating temperature of at least one of the plurality of heating rollers can be made higher than the heating temperature of the heating drum.

[0081] Thereby, the heating and drying of the ink can be performed more efficiently.

[0082] Regarding a specific example of the heating and drying device X, it will be described later (refer to Figure 2 ).

[0083] <Guide Roller>

[0084] The heating and drying device X includes a guide roller that contacts the ink-applied surface of the recording medium with ink applied thereto and guides the recording medium with ink applied thereto.

[0085] (RaX)

[0086] The arithmetic mean roughness Ra (that is, the above RaX; hereinafter, also simply referred to as "RaX") specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is preferably 2 μm to 15 μm, more preferably 2 μm to 8 μm.

[0087] When RaX of the outer peripheral surface of the guide roller is 15 μm or less, the dynamic friction coefficient is easily reduced, so image scratches can be further suppressed.

[0088] When RaX of the outer peripheral surface of the guide roller is 2 μm or more, it is easier to manufacture the guide roller.

[0089] Here, when the guide roller includes a surface layer described later, the outer peripheral surface of the guide roller refers to the surface of the surface layer.

[0090] In the following embodiments, RaX of the outer peripheral surface of the guide roller was measured using a SURFCOM 1500SD3 manufactured by Tokyo Seimitsu Co., Ltd.

[0091] The dynamic friction coefficient of the outer peripheral surface of the guide roller is preferably 0.03 to 0.22, more preferably 0.03 to 0.13, still more preferably 0.03 to 0.10, and still more preferably 0.03 to 0.08.

[0092] When the dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.22 or less, image scratches can be further suppressed.

[0093] When the dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.03 or more, it is easier to manufacture the guide roller.

[0094] The dynamic friction coefficient of the outer peripheral surface of the guide roller in the present invention refers to the value measured by the following method.

[0095] A polyurethane rubber ball indenter with an outer diameter of 3 / 8 inch and a rubber hardness of 90 degrees is used as the measurement indenter. Under the conditions of a test load of 50 gf, a speed of 10 mm / second, and a measurement distance of 50 mm, the frictional force (gf) of the outer peripheral surface of the guide roller is measured. The average value of the frictional force (gf) measured during the period from 0.4 seconds after the start of measurement to 1.0 second after the start of measurement is obtained. The value obtained by dividing the average value of the obtained frictional force (gf) by the test load (gf) is used as the dynamic friction coefficient of the outer peripheral surface of the guide roller.

[0096] In the following embodiments, the above measurement was performed using a surface property tester (such as "HAIDON 14FW" manufactured by Shinto Scientific Co., Ltd.).

[0097] The guide roller preferably includes a surface layer containing a fluororesin.

[0098] Thereby, it is easy to reduce the dynamic friction coefficient of the outer peripheral surface of the guide roller.

[0099] Examples of the fluororesin include the following:

[0100] Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),

[0101] Polytetrafluoroethylene (PTFE),

[0102] Tetrafluoroethylene-hexafluoropropylene copolymer (FEP),

[0103] Ethylene-tetrafluoroethylene copolymer (ETFE),

[0104] Polyvinylidene fluoride (PVDF),

[0105] Polychlorotrifluoroethylene (PCTFE) and

[0106] tetrafluoroethylene - hexafluoropropylene - perfluoroalkyl vinyl ether copolymer (EPE).

[0107] The fluororesin contained in the surface layer can be only one kind, or two or more kinds.

[0108] The fluororesin contained in the surface layer preferably includes PTFE.

[0109] There is no particular limitation on the core material of the guide roll when the guide roll includes a surface layer containing a fluororesin.

[0110] Examples of the core material include aluminum, aluminum alloy, stainless steel, etc.

[0111] The surface layer containing a fluororesin can be formed, for example, by coating a primer material on the core material, coating (applying) a fluororesin thereon, and sintering by heat treatment.

[0112] Moreover, the guide roll including a surface layer containing a fluororesin can also be formed by fitting a heat - shrinkable fluororesin hose onto the core material and heat - shrinking it with warm air.

[0113] The layer thickness of the surface layer containing a fluororesin is, for example, 100 μm or more, preferably 100 μm to 1000 μm, more preferably 100 μm to 500 μm.

[0114] <Heating roll>

[0115] The heating and drying device X includes a heating roll that contacts the non - ink - applied surface of the recording medium to which ink is applied and heats the ink applied to the recording medium through the recording medium.

[0116] There is no particular limitation on the heating roll, and a known heating roll can be used.

[0117] As a known heating roll, for example, a heating roll including a metal roll body and a heat source (for example, a halogen lamp) built into the roll body can be cited.

[0118] Examples of the metal as the material of the roll body include aluminum, aluminum alloy, stainless steel, etc.

[0119] Regarding the heating roll, for example, reference can be made to Japanese Unexamined Patent Application Publication No. 2020 - 16355 (paragraphs 0032 to 0037, Figure 3).

[0120] <Heating drum>

[0121] The heating and drying device X can include a heating drum that contacts the non - ink - applied surface of the recording medium to which ink is applied and heats the ink applied to the recording medium through the recording medium.

[0122] For example, the heating and drying device X1 may include a heating drum between the first transfer path and the second transfer path that contacts the non-ink-applied surface of the recording medium with ink applied thereto and heats the ink applied to the recording medium through the recording medium.

[0123] Thereby, the heating and drying of the ink can be performed more efficiently.

[0124] Regarding the heating drum, for example, reference can also be made to the structure of the heating roller described in Japanese Patent Laid-Open No. 2020-16355 (paragraphs 0032 to 0037, FIG. 3).

[0125] The preferred mode of the heating drum is the same as the preferred mode of the heating roller.

[0126] The diameter of the heating drum is preferably larger than the diameter of the heating roller.

[0127] When the heating and drying device X (for example, the heating and drying device X1) includes a heating drum, the heating temperature of at least one of the plurality of heating rollers can be made higher than the heating temperature of the heating drum.

[0128] Thereby, the heating and drying of the ink can be performed more efficiently.

[0129] <Hot air drying device>

[0130] The heating and drying device X may include a hot air drying device (for example, a dryer, etc.) that blows hot air onto the ink-applied surface of the recording medium to dry the ink.

[0131] For example, when the plurality of heating rollers are arranged in an arc shape, a plurality of dryers as the hot air drying device can be arranged outside the heating rollers arranged in an arc shape.

[0132] <Inkjet recording device including the heating and drying device X>

[0133] The recording method of the present invention can be implemented using an inkjet recording device including the above-mentioned heating and drying device X and an inkjet head.

[0134] Regarding this inkjet recording device, for example, reference can be made to Japanese Patent Laid-Open No. 2020-16355.

[0135] Hereinafter, the above inkjet recording device will be described with reference to the accompanying drawings.

[0136] In the accompanying drawings and their descriptions in the present invention, the same reference numerals are given to substantially the same elements (for example, components or parts), and repeated descriptions may sometimes be omitted.

[0137] Figure 1This is a diagram conceptually showing an inkjet recording apparatus 100 as an example of an inkjet recording apparatus used in the inkjet recording method of the present invention.

[0138] As Figure 1 shown, the inkjet recording apparatus 100 includes an ink application unit 101, and the ink application unit 101 includes inkjet heads 111A to 111D that eject and apply ink to a continuous paper 110 as a recording medium.

[0139] In the ink application unit 101, for example, full-line inkjet heads 111A, 111B, 111C, and 111D corresponding to four colors are arranged in order from the upstream side in the conveyance direction of the continuous paper 110. Each nozzle 111 applies, for example, black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink to the continuous paper 110.

[0140] In addition, the types and numbers of colors are not limited to this.

[0141] The ink ejected from each nozzle 111 contains water, pigments, resins, and waxes.

[0142] The continuous paper 110 is unwound from the original roll 102, sent out by the conveyance roller 112 of the conveyance unit 103 onto a conveyance guide member 113 disposed opposite to the ink application unit 101, and conveyed (moved) under the guidance of the conveyance guide member 113.

[0143] The continuous paper 110 to which ink has been applied by the ink application unit 101 passes through the heating and drying device 104, is conveyed by the discharge roller 118, and is wound around the take-up roller 105.

[0144] The heating and drying device 104 is an example of the heating and drying device used in the recording method of the present invention. More specifically, it is an example of the above-mentioned heating and drying device X1 (that is, the heating and drying device X1 including a heating drum).

[0145] Figure 2 This is an enlarged explanatory diagram of the heating and drying device 104.

[0146] As Figure 2 shown, the heating and drying device 104 includes heating rollers 11 (11A to 11J) and a heating drum 12 as heating members that come into contact with the non-ink-applied surface of the continuous paper 110 and heat the continuous paper 110.

[0147] In addition, the diameters of the plurality of heating rollers 11 are smaller than the diameter of the heating drum 12.

[0148] The diameters of the plurality of heating rollers 11 may be the same or different.

[0149] The heating and drying device 104 includes guide rollers 13A to 13K that are in contact with the ink-applied surface of the continuous paper 110 (specifically, the continuous paper 110 heated by the heating drum 12) and guide the continuous paper 110 with ink applied thereto.

[0150] Herein, the guide roller 13A is a guide roller that guides the continuous paper 110 heated by the heating drum 12 to the heating roller 11J.

[0151] The guide rollers 13B to 13K are respectively guide rollers that guide the continuous paper 110 guided by the guide roller 13A into contact with the heating rollers 11I to 11A.

[0152] In the heating and drying device 104, a conveyance path for the continuous paper 110 is formed by the above-described plurality of heating rollers 11 (that is, heating rollers 11A to 11J. The same applies hereinafter.), the heating drum 12, and the plurality of guide rollers 13 (that is, guide rollers 13A to 13K. The same applies hereinafter.).

[0153] Specifically, the continuous paper 110 is conveyed while being in contact with the outer peripheral sides of the plurality of heating rollers 11 arranged in an arc shape at a position upstream of the heating drum 12, and after passing through the heating drum 12, is guided by the plurality of guide rollers 13 and is conveyed while being in contact with the inner peripheral sides of the plurality of heating rollers 11 again.

[0154] At this time, the plurality of heating rollers 11 also contact the non-ink-applied surface side of the continuous paper 110 upstream of the heating drum 12 and after passing through the heating drum 12, and heat and dry the ink applied to the continuous paper across the continuous paper 110.

[0155] And, the heating drum 12 also contacts the non-ink-applied surface side of the continuous paper 110 in the same manner as the plurality of heating rollers 11, and heat and dry the ink applied to the continuous paper across the continuous paper 110.

[0156] The plurality of guide rollers 13 guide the continuous paper 110 to the plurality of heating rollers 11 while being in contact with the ink-applied surface side of the continuous paper 110.

[0157] And, the heating and drying device 104 respectively includes: guide rollers 17A to 17D for guiding the continuous paper 110 conveyed in the arrow direction from the ink application unit 101 into the heating and drying device 104 to the heating roller 11A; and a plurality of guide rollers 17E and 17D for guiding the continuous paper 110 heated by the plurality of heating rollers 11 and the heating drum 12 out of the heating and drying device 104. Figure 2 Herein, the guide rollers 17A to 17D guide the continuous paper 110 conveyed in the arrow direction from the ink application unit 101 into the heating and drying device 104 to the heating roller 11A; and the plurality of guide rollers 17E and 17D guide the continuous paper 110 heated by the plurality of heating rollers 11 and the heating drum 12 out of the heating and drying device 104.

[0158] In the heat drying in the heat drying device 104, first, while the ink non-imparting surface of the continuous paper 110 is brought into contact with a plurality of heating rollers 11 arranged in an arc shape, the ink is heated across the continuous paper 110.

[0159] Next, while the ink non-imparting surface of the continuous paper 110 is brought into contact with a heating drum 12 arranged inside a plurality of heating rollers 11 arranged in an arc shape, the ink is heated across the continuous paper 110.

[0160] Then, the continuous paper 110 is guided again to the heating roller 11 by the guide roller 13. While the ink non-imparting surface of the continuous paper 110 is brought into contact with the heating roller 11 again, the ink is heated across the continuous paper 110.

[0161] Here, in the heat drying device 104, the heating drum 12 can also be omitted.

[0162] In this case, for example, by changing the heating drum 12 to a guide roller with a smaller diameter, the ink non-imparting surface of the continuous paper 110 can be brought into contact with the heating roller 11 twice in the same manner as the heat drying device 104.

[0163] As described above, the heat drying device 104 includes: a first transfer path 10A through which the continuous paper 110 with ink imparted is transferred while being in contact with a plurality of heating rollers 11; and a second transfer path 10B through which the continuous paper 110 after passing through the first transfer path 10A is transferred while being in contact again with the plurality of heating rollers 11 that it contacted on the first transfer path 10A by being guided by a plurality of guide rollers 13.

[0164] Therefore, the ink imparted to the continuous paper 110 can be efficiently heat-dried.

[0165] Therefore, in the heat drying device 104, for example, shortening of the heat drying device, miniaturization of the heat drying device, etc. can be achieved.

[0166] On the second transfer path 10B, the continuous paper 110 does not necessarily have to be in contact with all of the plurality of heating rollers 11 that it contacted on the first transfer path 10A.

[0167] On the second transfer path 10B, the continuous paper 110 only needs to be in contact with at least a part of the plurality of heating rollers 11 that it contacted on the first transfer path 10A.

[0168] The heat drying device 104 includes a third transfer path between the first transfer path 10A and the second transfer path 10B through which the continuous paper 110 that has passed through the first transfer path 10A is transferred while being in contact with the heating drum 12.

[0169] Therefore, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0170] In the heating and drying device 104, the heating temperature of at least one of the plurality of heating rollers 11 can be made higher than the heating temperature of the heating drum 12.

[0171] In this case, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0172] In the heating and drying device 104, a plurality of dryers (not shown), which are warm air drying devices that blow warm air onto the surface of the ink film, can be arranged outside the plurality of heating rollers 11 configured in an arc shape.

[0173] In this case, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0174] In the inkjet recording method using the inkjet recording device 100, each ink applied from the inkjet heads 111A to 111D contains water, a pigment, a pigment-dispersing resin, and an acrylic resin as a resin other than the pigment-dispersing resin.

[0175] Moreover, while the guide rollers 13A to 13K, 17E, and 17F in the heating and drying device 104 of the inkjet recording device 100 are in contact with the ink application surface of the recording medium to which the ink is applied, the continuous paper 110 is guided.

[0176] In the inkjet recording method using the inkjet recording device 100, the product (A×B) of the acid value A (unit: mgKOH / g) of the above acrylic resin (i.e., the acrylic resin as a resin other than the pigment-dispersing resin) in each ink and the dynamic friction coefficient B of the outer peripheral surface of the guide roller is 1.0 to 5.0.

[0177] In the inkjet recording method using the inkjet recording device 100, it is sufficient that at least one ink and at least one guide roller satisfy the relationship that the RaX / Cw ratio is 1.0 to 4.0.

[0178] <Recording Medium>

[0179] The recording medium in the recording method of the present invention is not particularly limited, and for example, so-called coated paper used in general offset printing or the like can be cited. The coated paper is provided with a coating layer by coating a coating material on the surface of a high-quality paper, neutral paper, etc. that are usually not surface-treated and mainly composed of cellulose.

[0180] The coated paper can generally be commercially available coated paper. For example, as the coated paper, general printing coated paper can be used. Specifically, coated papers (A2, B2) such as "OK TOP COAT+" manufactured by OJIPAPER CO., LTD., "AURORA COAT" and "U-LITE" manufactured by Nippon Paper Industries Co., Ltd., and art paper (A1) such as "Tokubishi Art" manufactured by Mitsubishi Paper Mills Limited can be cited.

[0181] The recording medium can be a low water-absorbing recording medium or a non-water-absorbing recording medium.

[0182] In the present invention, the low water-absorbing recording medium means that the water absorption coefficient Ka is 0.05 mL / m 2 ·ms 1 / 2 ~0.5 mL / m 2 ·ms 1 / 2 of the recording medium, preferably 0.1 mL / m 2 ·ms 1 / 2 ~0.4 mL / m 2 ·ms 1 / 2 and more preferably 0.2 mL / m 2 ·ms 1 / 2 ~0.3 mL / m 2 ·ms 1 / 2 .

[0183] Moreover, the non-water-absorbing recording medium means that the water absorption coefficient Ka is less than 0.05 mL / m 2 ·ms 1 / 2 of the recording medium.

[0184] The water absorption coefficient Ka has the same meaning as that described in JAPAN TAPPI Pulp Test Method No. 51:2000 (issued by Japan Technical Association of the Pulp and Paper Industry). Specifically, the absorption coefficient Ka is calculated by the difference in the amount of water transferred at a contact time of 100 ms and a contact time of 900 ms using an automatic scanning liquid absorber KM500Win (manufactured by KUMAGAI RIKI KOGYO Co., Ltd.).

[0185] The non-water-absorbing recording medium is preferably a resin substrate. As the resin substrate, for example, a substrate formed by molding a thermoplastic resin into a sheet can be cited.

[0186] The resin substrate preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene or polyimide.

[0187] The resin substrate can be a transparent resin substrate, a colored resin substrate, or a metal vapor deposition treatment can be performed on at least a part thereof, etc.

[0188] The shape of the resin substrate is not particularly limited, but a sheet-like resin substrate is preferred, and from the viewpoint of the productivity of the printed matter, a resin substrate that can be formed into a roll by winding the sheet-like resin substrate is more preferred.

[0189] <Recording medium conveyance speed>

[0190] In the recording method of the present invention, the conveyance speed of the recording medium during ink application and during heat drying is both 60 m / minute or more.

[0191] Thereby, high-speed inkjet recording can be achieved.

[0192] Moreover, in high-speed inkjet recording that satisfies the above conveyance speed, the ejection property of the ink tends to decrease.

[0193] Therefore, in high-speed inkjet recording that satisfies the above conveyance speed, the ejection property improvement effect resulting from the provisions such as "the RaX / Cw ratio is 1.0 or more" in the recording method of the present invention can be significantly exhibited.

[0194] Here, the conveyance speed of the recording medium during ink application and during heat drying may be the same or different.

[0195] The upper limit of the conveyance speed of the recording medium is, for example, 200 m / minute.

[0196] The conveyance speed of the recording medium during ink application and during heat drying is preferably both 100 m / minute or more.

[0197] In this case, the ejection property improvement effect resulting from the provisions such as "the RaX / Cw ratio is 1.0 or more" in the recording method of the present invention can be more significantly exhibited.

[0198] <Ink drying temperature>

[0199] In the recording method of the present invention, the drying temperature of the ink during heat drying is 120°C or more and below the melting point of the wax.

[0200] In the present invention, the drying temperature of the ink is the maximum temperature reached on the surface of the ink film, and it refers to the value measured by a non-contact thermometer.

[0201] In the following examples, FT-H20 manufactured by KEYENCE CORPORATION was used as the non-contact thermometer to measure the drying temperature of the ink.

[0202] By setting the drying temperature of the ink during heat drying to 120°C or higher, high-speed inkjet recording can be achieved.

[0203] Moreover, in high-speed inkjet recording where the above drying temperature is usually satisfied, image scratches are likely to occur.

[0204] However, in the recording method of the present invention, by setting the drying temperature of the ink during heat drying to be below the melting point of the wax and setting the RaX / Cw ratio to 4.0 or less, as described above, the phenomenon of the wax penetrating into the interior of the ink film can be suppressed. As a result, image scratches can be suppressed.

[0205] From the viewpoint of further suppressing image scratches, the drying temperature of the ink during heat drying is more preferably "(melting point of the wax) - 5°C" or less.

[0206] <TOF-SIMS analysis of the surface of the image>

[0207] In the recording method of the present invention, in the TOF-SIMS analysis (Time-of-Flight Secondary Ion Mass Spectrometry) of the surface of the recorded image, it is preferable that the peak intensity of the wax is stronger than the peak intensity of the pigment.

[0208] Thereby, the phenomenon of the wax penetrating into the interior of the ink film can be further suppressed, and thus image scratches can be further suppressed.

[0209] In the following examples, a time-of-flight secondary ion mass spectrometer (TOF-SIMS) "PHI nano TOF II" manufactured by ULVAC-PHI, Inc. TM " is used for TOF-SIMS analysis.

[0210] <Ink>

[0211] The ink in the present invention (that is, the ink used in the recording method of the present invention. The same applies hereinafter.) contains water, a pigment, a pigment dispersion resin, and a wax.

[0212] The ink in the present invention may contain other components as needed.

[0213] (Water)

[0214] The ink of the present invention contains water.

[0215] Relative to the total amount of the ink, the content of water is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40% by mass or more.

[0216] The upper limit of the water content also depends on the amounts of other components. As the upper limit of the water content relative to the total amount of the ink, for example, 90% by mass, 80% by mass, etc. can be cited.

[0217] (Pigment)

[0218] The ink in the present invention contains at least one pigment.

[0219] The pigment can be an organic pigment or an inorganic pigment.

[0220] As the organic pigment, for example, azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black can be cited. Among them, the organic pigment is preferably an azo pigment or a polycyclic pigment.

[0221] As the azo pigment, for example, azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments can be cited.

[0222] As the polycyclic pigment, for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments can be cited.

[0223] As the dye chelate, for example, basic dye type chelates and acid dye type chelates can be cited.

[0224] As the inorganic pigment, for example, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black can be cited.

[0225] As the pigment, for example, the pigments described in "Encyclopedia of Pigments" edited by Shojiro Ito (published in 2000), W. Herbst, K. Hunger "Industrial Organic Pigments", Japanese Patent Laid-Open No. 2002-12607, Japanese Patent Laid-Open No. 2002-188025, Japanese Patent Laid-Open No. 2003-26978, and Japanese Patent Laid-Open No. 2003-342503 can be cited.

[0226] The volume average particle diameter of the pigment is preferably 10 nm to 200 nm, more preferably 10 nm to 180 nm, and still more preferably 10 nm to 150 nm. If the volume average particle diameter is 200 nm or less, the color reproducibility becomes good, and when recording an image by an inkjet recording method, the ejection property is improved. And if the volume average particle diameter is 10 nm or more, the light resistance becomes good.

[0227] Furthermore, the particle size distribution of the pigment is not particularly limited and may be either a wide particle size distribution or a monodisperse particle size distribution. Also, two or more pigments having a monodisperse particle size distribution may be mixed and used.

[0228] The volume average particle size and particle size distribution of the pigment are values measured using a particle size distribution measuring device (e.g., Microtrac UPA (registered trademark) EX150 manufactured by Nikkiso Co., Ltd.).

[0229] The content of the pigment is preferably 1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, relative to the total amount of the ink.

[0230] (Resin)

[0231] The ink in the present invention contains at least one resin.

[0232] Examples of the resin in the ink include a pigment dispersion resin, resin particles, and a water-soluble resin.

[0233] - Pigment dispersion resin -

[0234] The resin in the ink may contain at least one pigment dispersion resin.

[0235] In the present invention, the pigment dispersion resin refers to a resin having a function of dispersing pigments.

[0236] The form of the pigment dispersion resin is not particularly limited and may be any one of a random resin, a block resin, and a graft resin.

[0237] The pigment dispersion resin is preferably a resin having a crosslinked structure. It is considered that if the pigment dispersion resin is a resin having a crosslinked structure, the pigment dispersion resin is less likely to detach from the surface of the pigment, and the dispersion stability of the pigment is high.

[0238] In the present invention, the resin refers to a compound having a weight average molecular weight (Mw) of 1000 or more.

[0239] In the present invention, the weight average molecular weight (Mw) represents a value measured by gel permeation chromatography (GPC).

[0240] When measuring by gel permeation chromatography (GPC), HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) is used as the measuring device, three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) are used as columns, and THF (tetrahydrofuran) is used as the eluent. During the measurement, the sample concentration is set to 0.45% by mass, the flow rate is set to 0.35 ml / min, the sample injection volume is set to 10 μL, the measurement temperature is set to 40°C, and an RI detector is used. The calibration curve is prepared from eight samples of "standard sample TSK standard, polystyrene (polystyrene)" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0241] The resin having a crosslinked structure is not particularly limited as long as it has at least one crosslinked structure in the molecule.

[0242] Regarding whether the resin contained in the ink has a crosslinked structure, it can be determined, for example, by the following method. First, the resin is separated from the ink using a separation method such as solvent extraction. By analyzing the separated resin using various analytical methods such as nuclear magnetic resonance method (NMR), infrared spectroscopy (IR), and thermal analysis method, the presence or absence of a crosslinked structure can be comprehensively determined.

[0243] The resin having a crosslinked structure (hereinafter, also referred to as "crosslinked resin") is formed, for example, by crosslinking an uncrosslinked resin (hereinafter, also referred to as "uncrosslinked resin") using a crosslinking agent. The uncrosslinked resin is preferably a water-soluble resin.

[0244] In the present invention, "water-soluble" means the property of dissolving 1 g or more in 100 g of water at 25°C. As "water-soluble", the property of dissolving 3 g or more (more preferably 10 g or more) in 100 g of water at 25°C is preferred.

[0245] In addition, even if the uncrosslinked resin is water-soluble, the crosslinked resin is not necessarily water-soluble.

[0246] Examples of the uncrosslinked resin include vinyl resin, acrylic resin, polyurethane resin, and polyester resin. The uncrosslinked resin is preferably an acrylic resin.

[0247] The uncrosslinked resin is preferably a resin having a functional group capable of being crosslinked by a crosslinking agent. Examples of the functional group capable of crosslinking include a carboxyl group or its salt, an isocyanate group, and an epoxy group. Among them, from the viewpoint of improving the dispersibility of the pigment, the functional group capable of crosslinking is preferably a carboxyl group or its salt, and particularly preferably a carboxyl group. That is, the uncrosslinked resin is preferably a resin containing a carboxyl group.

[0248] The uncrosslinked resin is preferably a copolymer containing a structural unit derived from a monomer containing a carboxyl group (hereinafter referred to as "carboxyl group-containing monomer"). The structural unit derived from the carboxyl group-containing monomer contained in the copolymer may be only one kind, or two or more kinds. The copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred.

[0249] Examples of the carboxyl group-containing monomer include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0250] From the viewpoints of crosslinkability and dispersibility, the carboxyl group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, and more preferably (meth)acrylic acid.

[0251] Relative to the total amount of the uncrosslinked resin, the content of the structural unit derived from the carboxyl group-containing monomer is preferably 5% by mass to 40% by mass, more preferably 10% by mass to 35% by mass, and further preferably 10% by mass to 30% by mass.

[0252] The uncrosslinked resin preferably contains, in addition to the structural unit derived from the carboxyl group-containing monomer, a structural unit derived from a hydrophobic monomer.

[0253] The structural unit derived from the hydrophobic monomer contained in the copolymer may be only one kind, or two or more kinds.

[0254] Examples of the hydrophobic monomer include (meth)acrylate having an alkyl group with 1 to 20 carbon atoms, (meth)acrylate having an aromatic ring (for example, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), styrene, and styrene derivatives.

[0255] Relative to the total amount of the uncrosslinked resin, the content of the structural unit derived from the hydrophobic monomer is preferably 60% by mass to 95% by mass, more preferably 65% by mass to 90% by mass, and further preferably 70% by mass to 90% by mass.

[0256] The uncrosslinked resin is preferably a random copolymer containing a structural unit derived from a carboxyl group-containing monomer and at least one of a structural unit derived from a (meth)acrylate having an alkyl group with 1 to 20 carbon atoms and a structural unit derived from a (meth)acrylate having an aromatic ring. More preferably, it is a random copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from a (meth)acrylate having an aromatic ring. Further preferably, it is a copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from benzyl (meth)acrylate.

[0257] The weight average molecular weight (Mw) of the uncrosslinked resin is not particularly limited, but from the viewpoint of the dispersibility of the white pigment, it is preferably 3,000 to 300,000, more preferably 5,000 to 200,000, and further preferably 7,000 to 100,000.

[0258] The preferred range of the weight average molecular weight of the crosslinked resin is the same as the preferred range of the weight average molecular weight of the uncrosslinked resin.

[0259] The crosslinking agent used for crosslinking the uncrosslinked resin is preferably a compound having two or more reaction sites with the uncrosslinked resin (for example, a resin having a carboxyl group). Only one kind of crosslinking agent may be used, or two or more kinds may be used.

[0260] The preferred combination of the crosslinking agent and the uncrosslinked resin is a combination of a compound having two or more epoxy groups (i.e., an epoxy compound having two or more functional groups) and a resin having a carboxyl group. In this combination, a crosslinked structure is formed by the reaction of the epoxy group and the carboxyl group. It is preferable to form a crosslinked structure using the crosslinking agent after dispersing the pigment with the uncrosslinked resin.

[0261] Examples of the epoxy compound having two or more functional groups include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0262] Among them, the epoxy compound having two or more functional groups is preferably polyethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, or trimethylolpropane triglycidyl ether.

[0263] The crosslinking agent may also be a commercially available product.

[0264] Examples of commercially available products include Denacol EX-321, EX-821, EX-830, EX-850, and EX-851 (manufactured by Nagase ChemteX Corporation).

[0265] From the viewpoints of the crosslinking reaction rate and the dispersion stability after crosslinking, the molar ratio of the reactive sites (e.g., epoxy groups) in the crosslinking agent to the reactive sites (e.g., carboxyl groups) in the uncrosslinked resin is preferably 1:1.1 to 1:10, more preferably 1:1.1 to 1:5, and further preferably 1:1.1 to 1:3.

[0266] The mixing ratio of the pigment to the pigment dispersion resin is preferably 1:0.02 to 1:2 by mass, more preferably 1:0.03 to 1:1.5, and further preferably 1:0.04 to 1:1.

[0267] - Resin particles -

[0268] From the viewpoint of further suppressing image scratches, the resin in the ink preferably contains at least one kind of resin particles.

[0269] Thereby, the abrasion resistance of the image is further improved.

[0270] The resin particles contain resin and may also contain a core material other than resin, etc., but are preferably resin particles composed only of resin.

[0271] As the resin particles, particles composed of an acrylic resin, particles composed of a polyester resin, particles composed of a polyurethane resin, or particles composed of a polyolefin resin are preferred, and particles composed of an acrylic resin are more preferred.

[0272] In the present invention, the acrylic resin means a resin containing at least one of a structural unit derived from (meth)acrylic acid and a structural unit derived from (meth)acrylate.

[0273] Regarding the resin particles, for example, reference can be made to paragraphs 0038 to 0114 of International Publication No. 2021 / 192720, paragraphs 0109 to 0120 of Japanese Unexamined Patent Application Publication No. 2015-25076, etc.

[0274] From the viewpoint of further improving the abrasion resistance of the image, the glass transition temperature (Tg) of the resin particles is preferably 90°C to 250°C, and more preferably 100°C to 230°C.

[0275] Here, the glass transition temperature (Tg) of the resin particles applies the measured Tg obtained by actual measurement. Regarding the measurement method of the measured Tg, reference can be made to paragraph 0111 of Japanese Unexamined Patent Application Publication No. 2015-25076.

[0276] When the ink of the present invention contains resin particles, the content of the resin particles relative to the total amount of the ink is preferably 0.1% by mass to 10.0% by mass, more preferably 0.3% by mass to 8.0% by mass, still more preferably 0.3% by mass to 5.0% by mass, still more preferably 0.3% by mass to 3.0% by mass, and still more preferably 0.5% by mass to 1.0% by mass.

[0277] When the content of the resin particles relative to the total amount of the ink is 0.1% by mass or more, image scratches can be further suppressed.

[0278] The ink of the present invention containing resin particles can also be prepared using a commercially available resin emulsion (i.e., an aqueous dispersion of resin particles).

[0279] Examples of commercially available resin emulsions include A-810 (SANSUI Co., Ltd.), A-995 (SANSUI Co., Ltd.), HIROS-X·NE-2186 (SEIKO PMC CORPORATION), HIROS-X·TE-1048 (SEIKO PMC CORPORATION), Cybinol SK-202 (SAIDEN CHEMICAL INDUSTRY CO., LTD.), TOCRYL W-1048 (TOYOCHEM CO., LTD.), WC-M-1217 (ARAKAWA CHEMICAL INDUSTRIES, LTD.), WC-M-1219 (ARAKAWA CHEMICAL INDUSTRIES, LTD.), N985(A)-1 (Emulsion Technology Co., Ltd.), Neocryl A-1105 (DSM coating resins Ltd.), Acryte SE-810A, Acryte SE-953A-2, Acryte SE-1658F, Acryte SE-2974F, Acryte SE-2978F (TAISEI FINE CHEMICAL CO,., LTD.), Luck Star 7132-C (DIC), ST200 (NIPPON SHOKUBAI CO., LTD.), Mowinyl 972 (Japan Coating Resin co., ltd.), and the like.

[0280] -Water-soluble resin-

[0281] The resin in the ink may contain at least one water-soluble resin.

[0282] The definition of "water-soluble" in the water-soluble resin is as described above.

[0283] As the water-soluble resin, for example, the same resins as the above-mentioned uncrosslinked resins can be cited.

[0284] (Wax)

[0285] The ink in the present invention contains at least one wax.

[0286] Wax is a component that serves as the basis for suppressing image scratches in the recording method of the present invention.

[0287] As the wax, natural waxes and synthetic waxes can be cited.

[0288] As the natural wax, petroleum waxes, vegetable waxes, animal-vegetable waxes, etc. can be cited.

[0289] As the petroleum wax, paraffin wax, microcrystalline wax, petrolatum, etc. can be cited.

[0290] As the vegetable wax, carnauba wax, candelilla wax, rice wax, wood wax, etc. can be cited.

[0291] As the animal-vegetable wax, lanolin, beeswax, etc. can be cited.

[0292] As the synthetic wax, synthetic hydrocarbon waxes, modified waxes, resin waxes, etc. can be cited.

[0293] As the synthetic hydrocarbon wax, polyethylene (PE) wax, polypropylene (PP) wax, Fischer-Tropsch wax, etc. can be cited.

[0294] As the modified wax, paraffin wax derivatives, montan wax derivatives, microcrystalline wax derivatives, fatty acid amide wax derivatives, etc. can be cited.

[0295] As the resin wax, acrylic wax, urethane wax, etc. can be cited.

[0296] The melting point of the wax is preferably 170 °C or lower, more preferably 100 °C to 170 °C, further preferably 100 °C to 160 °C, and further preferably 110 °C to 150 °C.

[0297] The melting point in the present invention refers to the temperature at the peak of endothermic absorption in the measurement using a differential scanning calorimeter (DSC: Differential scanning calorimetry), for example, a differential scanning calorimeter (product name "EXSTAR6220", manufactured by Hitachi High-Tech Science Corporation).

[0298] The ink of the present invention can be prepared using commercially available water dispersions of wax.

[0299] Examples of commercially available products of the aqueous dispersion of wax include the following:

[0300] Hi-Tech E-6314 and Hi-Tech E-9015 manufactured by Toho Chemical Industry Co.,Ltd.;

[0301] Nopcoat PEM17 manufactured by SAN NOPCO LIMITED;

[0302] Chemipearl (registered trademark) W4005 manufactured by Mitsui Chemicals,Inc.;

[0303] AQUACER515, AQUACER531, AQUACER552, and AQUACER593 manufactured by BYK Japan KK.;

[0304] Cellosol 524 etc. manufactured by CHUKYO YUSHI CO.,LTD.

[0305] - Content of wax (Cw) relative to the total amount of the ink -

[0306] The content of wax (Cw) relative to the total amount of the ink is preferably 0.2% by mass to 5.0% by mass, more preferably 0.5% by mass to 3.0% by mass, and still more preferably 0.7% by mass to 2.5% by mass.

[0307] In the present invention, the content of wax (% by mass) relative to the total amount of the ink is sometimes represented by "Cw".

[0308] (Silicone surfactant)

[0309] The ink in the present invention may contain at least one silicone surfactant. Thereby, image scratches can be further suppressed.

[0310] As the silicone surfactant, a polyether-modified silicone surfactant is preferred, and a compound represented by the following formula (D1) is more preferred.

[0311] [Chemical formula 1]

[0312]

[0313] In formula (D1), R 1 each independently represents an alkyl group or a hydroxyl group having 1 to 3 carbon atoms, R 2 represents an alkanediyl group having 2 to 5 carbon atoms, R 3represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a hydroxyl group, PO represents a propyleneoxy group, and EO represents an ethyleneoxy group. a, b, m and n represent the average addition molar numbers of each unit, a is 0 to 10, b is 1 to 50, m is 1 to 500, and n is 1 to 50.

[0314] In addition, in formula (D1), the arrangement of PO and EO can be a block copolymer arrangement or a random copolymer arrangement.

[0315] In formula (D1), the arrangement of the structural unit marked with subscript m and the structural unit marked with subscript n can be a block copolymer arrangement or a random copolymer arrangement.

[0316] R 1 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group.

[0317] R 2 is preferably an alkanediyl group having 3 or 4 carbon atoms, more preferably a trimethylene group.

[0318] R 3 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group.

[0319] More preferably, a is 0, b is 1 to 15, m is 1 to 10, and n is 1 to 5. Further preferably, a is 0, b is 3 to 10, m is 1 to 3, and n is 1 to 3.

[0320] As the silicone-based surfactant, commercially available products can also be used.

[0321] Examples of commercially available products of the silicone-based surfactant include the following:

[0322] BYK-302, BYK-307, BYK-331, BYK-333, BYK-345, BYK-347, BYK-348, BYK-349, BYK-378, BYK-3400, BYK-3450, BYK-3451, BYK-3455, BYK-3760 (manufactured by BYK Japan KK.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-644, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020 (manufactured by Shin-Etsu Chemical Co., Ltd.), SILFACE SAG002, SILFACE SAG005, SILFACE SAG008, SILFACE SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.), TEGOWet KL245, TEGOWet 240, TEGOWet 250, TEGOWet 260, TEGOWet 270, TEGOWet 280 (manufactured by EVONIK Corporation), etc.

[0323] These commercially available products are all compounds represented by formula (D1).

[0324] The content of the silicone-based surfactant relative to the total amount of the ink is preferably 0.01% by mass to 3.0% by mass, more preferably 0.02% by mass to 2.0% by mass, and still more preferably 0.05% by mass to 1.5% by mass.

[0325] (Surfactants other than silicone-based surfactants)

[0326] The ink in the present invention may contain at least one surfactant other than the silicone-based surfactant (hereinafter, also referred to as other surfactants).

[0327] Examples of other surfactants include acetylene glycol-based surfactants, alkylene oxide adducts of alcohols, etc.

[0328] As the acetylene glycol-based surfactant, for example, a compound represented by the following formula (A1) is preferably used.

[0329] [Chemical formula 2]

[0330]

[0331] In formula (A1), R1 and R4 each independently represent an alkyl group having 3 to 10 carbon atoms, and R2 and R3 each independently represent a methyl group or an ethyl group.

[0332] a, b, c, and d represent the average addition mole numbers of the respective units, and are each 0 to 50.

[0333] Preferred examples of the acetylene diol-based surfactant include the following:

[0334] An acetylene diol selected from the group consisting of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyn-3,6-diol, 2,5,6,11-tetramethyl-6-dodecyn-5,8-diol, 2,5-dimethyl-3-hexyn-2,5-diol, and 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol; and

[0335] An ethylene oxide adduct of the above acetylene diol, etc.

[0336] The acetylene diol-based surfactant can be synthesized, for example, by reacting acetylene with a ketone or an aldehyde corresponding to the target acetylene diol.

[0337] The acetylene diol-based surfactant can be obtained, for example, by the methods described on pages 94 to 107 of "New Surfactant Introduction" (published by Sanyo Chemical Industries, Ltd. in 1992), written by Takehiko Fujimoto, revised edition.

[0338] Examples of commercially available products of the acetylene diol-based surfactant include Surfynol 104E (HLB value 4), Surfynol 104H (HLB value 4), Surfynol 104A (HLB value 4), Surfynol 104PA (HLB value 4), Surfynol 104PG-50 (HLB value 4), Surfynol 104S (HLB value 4), Surfynol 420 (HLB value 4), Surfynol 440 (HLB value 8), Surfynol 465 (HLB value 13), Surfynol 485 (HLB value 17), Surfynol SE (HLB value 6), Surfynol SE-F (HLB value 6), Surfynol 61 (HLB value 6), Surfynol 82 (HLB value 4), Surfynol DF110D (HLB value 3), Dynol 604 (HLB value 8), Dynol 607 (HLB value 8), Surfynol 2502 (HLB value 8), Surfynol TG (HLB value 9), OLFINE E1004 (HLB value: 7 - 9), OLFINE E1010 (HLB value: 13 - 14) (manufactured by Evonik Industries AG), ACETYLENOL E00, ACETYLENOL E13T, ACETYLENOL E40, ACETYLENOL E60, ACETYLENOL E100, ACETYLENOL E200 (manufactured by Kawaken Fine Chemicals Co., Ltd.), etc.

[0339] As the alkylene oxide adduct of an alcohol, an ethylene oxide adduct of an alcohol or an adduct of ethylene oxide and propylene oxide of an alcohol is preferred, and an ethylene oxide adduct of an alcohol is more preferred.

[0340] As the alkylene oxide adduct of an alcohol, the compound represented by the following formula (2) is further preferred.

[0341] R3O - [(EO) m / (PO) n -H... Formula (2)

[0342] In formula (2), R3 represents a hydrocarbon group having 6 or more and 30 or less carbon atoms, EO represents an ethoxy group, and PO represents a propoxy group.

[0343] In formula (2), m and n represent the average addition molar numbers, m is 2 or more and 100 or less, n is 0 or more and 50 or less, and the sum of m and n is 2 or more and 120 or less.

[0344] In formula (2), “(EO) m / (PO) n ” This notation indicates that the configuration of EO and PO can be that of a random copolymer or that of a block copolymer. At the position marked as “(EO) m / (PO) n ”, the addition order of EO and PO is arbitrary.

[0345] In formula (2), when n is 2 or more, the compound represented by formula (2) can be a block copolymer or a random copolymer. When the compound represented by formula (2) is a block copolymer, a compound having an oxyethylene group on the hydroxyl side, that is, RO-(PO)(EO)-H, is preferred.

[0346] Moreover, when the compound represented by formula (2) is a block copolymer, it can be a triblock copolymer of RO-(EO)(PO)(EO)-H.

[0347] As commercially available products of alkylene oxide adducts of alcohols,

[0348] As ethylene oxide adducts of lauryl alcohol, EMULGEN 102 (HLB: 6.3, average number of moles of EO added: 2), EMULGEN 103 (HLB: 8.1, average number of moles of EO added: 3), EMULGEN103 (HLB: 9.7, average number of moles of EO added: 4), EMULGEN 108 (HLB: 12.1, average number of moles of EO added: 6), EMULGEN 109P (HLB: 13.6, average number of moles of EO added 8), EMULGEN 120 (HLB: 15.3, average number of moles of EO added: 13), EMULGEN 147 (HLB: 16.3, average number of moles of EO added: 17), EMULGEN 150 (HLB: 18.4, average number of moles of EO added: 44), etc. manufactured by Kao Corporation can be cited,

[0349] As ethylene oxide adducts of secondary alcohols having 12 carbon atoms, Tergitol TMN-3 (HLB: 8.1, average number of moles of EO added: 3), Triton HW-1000 (HLB: 10, average number of moles of EO added: 6), Tergitol TMN-6 (HLB: 13.1, average number of moles of EO added: 8), Tergitol TMN-100X (HLB: 14.0, average number of moles of EO added: 9), Tergitol TMN-10 (HLB: 14.4, average number of moles of EO added: 10), etc. manufactured by Dow Chemical Company can be cited.

[0350] In addition, as commercially available products of alkylene oxide adducts of alcohols, EMULGEN 707 (ethylene oxide adduct of secondary alcohols having 11 to 15 carbon atoms, HLB: 12.1, average number of moles of EO added: 6), EMULGEN 220 (ethylene oxide adduct of linear primary alcohols having 16 to 18 carbon atoms, HLB: 14.2, average number of moles of EO added: 13), etc. manufactured by Kao Corporation can also be cited.

[0351] The content of other surfactants relative to the total amount of the ink is preferably 0.01% by mass to 5.0% by mass, more preferably 0.02% by mass to 4.0% by mass, and still more preferably 0.1% by mass to 3.0% by mass.

[0352] (Water-soluble organic solvent)

[0353] The ink in the present invention may contain at least one water-soluble organic solvent.

[0354] Thereby, the ejection property of the ink can be further improved.

[0355] In the present invention, "water-soluble" in "water-soluble organic solvent" means the property of dissolving 1 g or more in 100 g of water at 25°C.

[0356] The types of water-soluble organic solvents that can be contained in the ink are not limited. For example, the following can be cited:

[0357] Monohydric alcohols having 1 to 4 carbon atoms;

[0358] Diols such as 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol;

[0359] Triols such as glycerol, 1,2,6-hexanetriol, trimethylolpropane;

[0360] Alkylene diols such as ethylene glycol, propylene glycol (alias 1,2-propanediol);

[0361] Alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether;

[0362] Polyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol;

[0363] Polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether;

[0364] 2-pyrrolidone, N-methyl-2-pyrrolidone, etc.

[0365] The water-soluble organic solvent in the ink preferably contains at least one selected from the group consisting of alkylene glycols and alkylene glycol monoalkyl ethers.

[0366] Relative to the total amount of the ink, the content of the water-soluble organic solvent is preferably 10% by mass to 50% by mass, more preferably 15% by mass to 40% by mass.

[0367] (Other components)

[0368] The ink in the present invention may contain other components in addition to the above components as needed.

[0369] As other components, for example, colloidal silica, wax, inorganic salts, solid wetting agents (such as urea), anti-fading agents, emulsion stabilizers, penetration promoters, ultraviolet absorbers, preservatives, mildew inhibitors, pH regulators, defoamers, viscosity regulators, dispersion stabilizers, rust inhibitors, chelating agents, water-soluble high molecular compounds, etc. can be cited.

[0370] (Physical properties of the ink)

[0371] - Viscosity -

[0372] The viscosity of the ink in the present invention is preferably 1.2 mPa·s to 15.0 mPa·s, more preferably 2.0 mPa·s to 13.0 mPa·s, and further preferably 2.5 mPa·s to 10.0 mPa·s.

[0373] The viscosity of the ink is measured at a temperature of 30 °C using a rotational viscometer (for example, the product name "VISCOMETER TV-22" manufactured by Toki Sangyo Co., Ltd.).

[0374] - pH -

[0375] From the viewpoint of the storage stability of the ink, the pH of the ink in the present invention is preferably 6.0 to 11.0, more preferably 7.0 to 10.0, and further preferably 7.0 to 9.5.

[0376] The pH of the ink is measured at a temperature of 25 °C using a pH meter (for example, the product name "WM-50EG" manufactured by DKK-TOA CORPORATION).

[0377] <RaX / Cw ratio>

[0378] As described above, the ratio of the arithmetic mean roughness Ra of the outer peripheral surface of the guide roller, that is, RaX, to the content of wax relative to the total amount of the ink, that is, Cw mass%, (i.e., RaX / Cw ratio) is 1.0 to 4.0.

[0379] The RaX / Cw ratio is preferably 1.3 to 3.5, more preferably 1.4 to 3.0.

[0380] When the RaX / Cw ratio is 1.3 or more, the decrease in the ejection property of the ink can be further suppressed.

[0381] When the RaX / Cw ratio is 3.5 or less, image scratching can be further suppressed.

[0382] <Cw / Ct ratio>

[0383] In the recording method of the present invention, when the content of wax relative to the total amount of the ink is Cw mass%, and the total content of pigment, resin, and wax relative to the total amount of the ink is Ct mass%, the Cw / Ct ratio is preferably 0.05 to 0.35, more preferably 0.09 to 0.35, and further preferably 0.10 to 0.30.

[0384] When the Cw / Ct ratio is 0.05 or more, image scratching can be further suppressed.

[0385] When the Cw / Ct ratio is 0.35 or less, the decrease in the ejection property of the ink can be further suppressed.

[0386] <Ct>

[0387] In the recording method of the present invention, the total content (mass%) of pigment, resin, and wax relative to the total amount of the ink, that is, Ct, is 5.0 mass% to 11.0 mass%.

[0388] As described above, by setting Ct to 11.0 mass% or less, the decrease in the ejection property of the ink can be suppressed.

[0389] By setting Ct to 5.0 mass% or more, image scratching can be suppressed.

[0390] Ct is preferably 5.5 mass% to 10.0 mass%, more preferably 5.5 mass% to 8.0 mass%.

[0391] <Cw / Cp ratio>

[0392] In the recording method of the present invention, when the content of wax relative to the total amount of the ink is Cw mass%, and the content of resin relative to the total amount of the ink is Cp mass%, the Cw / Cp ratio is preferably 0.10 to 1.60, more preferably 0.50 to 1.50, and further preferably 0.50 to 1.30.

[0393] When the Cw / Cp ratio is 0.10 or more, image scratching can be further suppressed.

[0394] When the Cw / Cp ratio is 1.60 or less, the decrease in the ejection property of the ink can be further suppressed.

[0395] Examples

[0396] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist thereof.

[0397] When preparing each ink, each pigment dispersion and binder resin were prepared in advance, and each ink was prepared using them.

[0398] <Synthesis of water-soluble resin as a pigment dispersion resin precursor>

[0399] As a precursor of crosslinked resin 1 which is a pigment dispersion resin described later, water-soluble resin 1 (resin before crosslinking) was synthesized.

[0400] The detailed content is shown below.

[0401] A monomer supply composition was prepared by mixing methacrylic acid (172 parts by mass), benzyl methacrylate (828 parts by mass), and isopropyl alcohol (375 parts by mass).

[0402] Moreover, an initiator supply composition was prepared by mixing 2,2-azobis(2-methylbutyronitrile) (22.05 parts by mass) and isopropyl alcohol (187.5 parts by mass).

[0403] Next, isopropyl alcohol (187.5 parts by mass) was heated to 80°C under a nitrogen atmosphere, and a mixture of the monomer supply composition and the initiator supply composition was added dropwise thereto over 2 hours. After completion of the dropwise addition, the obtained solution was further maintained at 80°C for 4 hours and then cooled to 25°C. After cooling, the solvent was removed under reduced pressure, whereby water-soluble resin 1 (methacrylic acid / benzyl methacrylate copolymer) was obtained. The weight-average molecular weight of the obtained water-soluble resin 1 was about 30,000, and the acid value was 112 mgKOH / g.

[0404] <Preparation of cyan pigment dispersion>

[0405] The amount of methacrylic acid in the obtained water-soluble resin 1 (150 parts by mass) was neutralized with an aqueous potassium hydroxide solution in an amount of 0.8 equivalent. Then, ion-exchanged water was added to adjust the concentration to 25% by mass, and an aqueous solution of water-soluble resin Q-1 was obtained.

[0406] Water-soluble resin Q-1 is a neutralized product of water-soluble resin 1 in which the carboxyl group (-C(=O)OH group) in the above water-soluble resin 1 is changed to -C(=O)ONa group.

[0407] An aqueous solution of a mixed water-soluble resin Q-1 (124 parts by mass), a cyan pigment (Pigment Blue 15:3 (Phthalocyanine Blue-A220, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.)) (48 parts by mass), water (75 parts by mass), and dipropylene glycol (30 parts by mass) were mixed and dispersed using a bead mill (bead diameter 0.1 mmφ, zirconia beads) until the desired volume average particle size was obtained, thereby obtaining a dispersion (uncrosslinked dispersion) in which the cyan pigment was dispersed by the water-soluble resin Q-1. The pigment concentration of the cyan pigment in the uncrosslinked dispersion was 15% by mass.

[0408] To this uncrosslinked dispersion (136 parts by mass), trimethylolpropane polyglycidyl ether (product name “Denacol EX-321”, manufactured by Nagase ChemteX Corporation) (1.3 parts by mass) as a crosslinking agent and an aqueous boric acid solution (boric acid concentration: 4% by mass) (14.3 parts by mass) were added, and the mixture was reacted at 50°C for 6.5 hours and then cooled to 25°C, thereby crosslinking the water-soluble resin Q-1 with the crosslinking agent.

[0409] Thereby, a dispersion (crosslinked dispersion) in which the cyan pigment was dispersed by a crosslinked resin 1 as a pigment dispersion resin was obtained. Here, the crosslinked resin 1 is a pigment dispersion resin obtained by crosslinking the water-soluble resin Q-1 with the above crosslinking agent.

[0410] Next, ion-exchanged water was added to the obtained crosslinked dispersion, and ultrafiltration was performed using a stirring type Ultra Holder (manufactured by ADVANTEC CO., LTD.) and an ultrafiltration filter (manufactured by ADVANTEC CO., LTD., cut-off molecular weight 50,000, Q0500076E ultrafilter). After purification so that the concentration of dipropylene glycol in the crosslinked dispersion became 0.1% by mass or less, the dispersion was concentrated until the pigment concentration became 15% by mass, thereby obtaining a cyan pigment dispersion (cyan pigment concentration 15% by mass) in which the cyan pigment was dispersed by the crosslinked resin 1.

[0411] <Preparation of the aqueous dispersion of resin particles>

[0412] Into a three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, water (250 g), 12-methacrylamidododecanoic acid (6.7 g), potassium hydrogencarbonate (0.17 g), and isopropanol (20 g) were charged, and the temperature was raised to 85°C under a nitrogen stream. A mixed solution composed of 4,4'-azobis(4-cyanovaleric acid) (radical polymerization initiator, product name "V-501", manufactured by FUJIFILM Wako Pure Chemical Corporation) (0.11 g), potassium hydrogencarbonate (0.08 g), and water (9 g) was added thereto, and the mixture was stirred for 10 minutes. Subsequently, a monomer solution composed of styrene (14 g), benzyl methacrylate (14 g), methyl methacrylate (48 g), butyl methacrylate (3.3 g), and 2-hydroxyethyl methacrylate (14 g) was added dropwise to the above three-necked flask at a constant rate over 3 hours. Moreover, a mixed solution composed of V-501 (0.06 g), potassium hydrogencarbonate (0.04 g), and water (6 g) was added in two portions, immediately after the start of the dropwise addition of the above monomer solution and 1.5 hours after the start of the dropwise addition of the monomer solution. After completion of the dropwise addition of the monomer solution, the mixture was stirred for 1 hour. Subsequently, a mixed solution composed of V-501 (0.06 g), potassium hydrogencarbonate (0.04 g), and water (6 g) was added to the obtained reaction mixture, and the mixture was further stirred for 3 hours. The obtained reaction mixture was filtered through a 50-μm mesh sieve to obtain an aqueous dispersion of resin particles.

[0413] [Example 1]

[0414] <Preparation of Cyan Ink>

[0415] Each component was mixed according to the following composition to obtain a mixed solution. Subsequently, coarse particles were removed from the above mixed solution using a 1-μm filter to obtain cyan ink.

[0416] -Composition-

[0417] (Pigment)

[0418] · Cyan pigment dispersion (aqueous dispersion with a pigment concentration of 15% by mass)… an amount such that the content of the pigment in the ink becomes 3.0 parts by mass and the content of the pigment-dispersing resin becomes 0.9 part by mass

[0419] (Water-soluble organic solvent)

[0420] · Diethylene glycol monoethyl ether (DEGmEE) (manufactured by Daicel Corporation)… 15 parts by mass

[0421] · Propylene glycol (PG) (manufactured by ADEKA CORPORATION)… 20 parts by mass

[0422] (Resin particles)

[0423] · The dispersion of the resin particles prepared above (solid content concentration: 25% by mass)… The amount of the resin particles becomes 0.9 part by mass

[0424] (Surfactant)

[0425] · “Surfynol 104PG50” manufactured by Nissin Chemical Industry Co., Ltd. (solid content: 50% by mass) (acetylene glycol-based surfactant; 2,4,7,9-tetramethyl-5-decyn-4,7-diol)… 2.0 parts by mass

[0426] · “EMULGEN 108” manufactured by Kao Corporation (polyoxyethylene alkyl ether-based surfactant with the repeating number of polyoxyethylene being 6 and being lauryl alcohol ether)… 1.0 part by mass

[0427] · “BYK-345” manufactured by BYK (silicone-based surfactant having the structure represented by formula (D1), where a is 0, b is 5.9, m is 1.8, and n is 1 in formula (D1))… 0.4 part by mass

[0428] (Wax)

[0429] · “AQUACER 531” (PE wax emulsion) manufactured by BYK Japan KK. (solid content: 45% by mass)… The amount of the wax becomes 1.4 parts by mass

[0430] (Other components)

[0431] · Urea (manufactured by Nissan Chemical Corporation)… 2.0 parts by mass

[0432] · Water… The total amount becomes 100 parts by mass

[0433] <Inkjet recording>

[0434] An inkjet recording device having the same structure as the Figure 1 inkjet recording device shown was prepared. As each inkjet head in the inkjet recording device, an inkjet recording linear head “KJ4B-1200” (manufactured by KYOCERA Corporation) (1200 dpi high-image-quality model) was used.

[0435] The prepared magenta ink is ejected from one of the inkjet heads in the above-described inkjet recording apparatus and applied to a recording medium. While the recording medium with the applied ink is being conveyed, the ink applied to the recording medium is heated and dried, thereby performing inkjet recording.

[0436] The detailed conditions for inkjet recording are as follows.

[0437] <Conditions for Inkjet Recording>

[0438] · Recording medium: Product name “OK TOP COAT”, manufactured by OJIPAPER CO., LTD. (Water absorption: 4.9 g / m 2 )

[0439] · Conveying mechanism of the recording medium: Roll-to-roll

[0440] · Temperature of the inkjet head: 32°C

[0441] · Resolution of the inkjet head: 1200 × 1200 [dpi (dot per inch)]

[0442] · Size of the ejected ink droplets: 3.0 [pL]

[0443] · Environment around the inkjet head: Temperature 25°C ± 1°C, relative humidity 25°C ± 5%

[0444] · Conveying speed: 100 [m / min] both during ink application and during heating and drying

[0445] · Tension of the recording medium during conveyance: 60 N

[0446] · Recorded image: Solid image

[0447] · Heating method: Heating roller (heating temperature adjusted so that the temperature of the surface of the ink film becomes the “ink drying temperature” described in Table 1), heating drum (heating temperature 120°C), and a warm air drying device (not shown) (warm air temperature 130 [°C], wind speed 20 [m / s]). As the warm air drying device, a plurality of dryers are arranged outside the heating roller configured in an arc shape. Using these dryers, warm air is blown onto the ink application surface of the recording medium.

[0448] · Guide roller, heating roller, heating drum: Prepared according to paragraphs 0063 to 0082 of Japanese Unexamined Patent Application Publication No. 2020-16355.

[0449] The following matters in inkjet recording are shown in Table 1.

[0450] · Drying temperature of the ink (temperature of the surface of the ink film)

[0451] · The drying temperature of the ink is below the melting point of the wax (Y... compliant, N... non-compliant)

[0452] · The surface roughness Ra (RaX) (μm) of the outer peripheral surface of the guide roller

[0453] · RaW / Cw

[0454] · Cw / Ct

[0455] · The amount of resin (Cp)

[0456] · Cw / Cp

[0457] · The dynamic friction coefficient of the outer peripheral surface of the guide roller

[0458] · The type of fluororesin in the surface layer of the guide roller

[0459] · The dynamic friction coefficient of the outer peripheral surface of the guide roller

[0460] · The surface roughness Ra (RaX) (μm) of the outer peripheral surface of the guide roller

[0461] · The TOF-SIMS analysis result of the image surface (wax > pigment) (Y... compliant, N... non-compliant)

[0462] <Evaluation of ink ejection property>

[0463] With an ink droplet volume of 3 pL and an ejection frequency of 24 kHz, the above-mentioned cyan ink was continuously ejected from all the nozzles of the above inkjet head for 45 minutes. In addition, at the start of this ejection, it was confirmed in advance that ink was ejected from all the nozzles.

[0464] After the 45-minute continuous ejection ended, the number of nozzles that could eject until the end (the number of ejection nozzles after the 45-minute continuous ejection) was counted. Using this number of ejection nozzles, the ink ejection rate was calculated by the following formula, and the ink ejection property was evaluated according to the following evaluation criteria.

[0465] The results are shown in Table 1.

[0466] Among the following evaluation criteria, the grade with the most excellent ink ejection property is A.

[0467] Ink ejection rate (%) = (the number of ejection nozzles after the 45-minute continuous ejection) / (the total number of nozzles) × 100

[0468] - Evaluation criteria for ejection property -

[0469] A: The ink ejection rate after the 45-minute continuous ejection is 98% or more.

[0470] B: The ink ejection rate after the 45-minute continuous ejection is 92% or more and less than 98%.

[0471] C: The ink ejection rate after 45 minutes of continuous ejection is less than 92%.

[0472] <Evaluation of Image Scratches>

[0473] Using the above inkjet recording apparatus and the above cyan ink, a solid image with a Duty of 100% was continuously recorded on a recording medium.

[0474] Five evaluators visually observed the obtained solid image, and each evaluator scored according to the following evaluation scores.

[0475] Next, the average value of the evaluation scores of the five evaluators was obtained, and based on the obtained average value, the image scratches were evaluated according to the following evaluation criteria.

[0476] The results are shown in Table 1.

[0477] - Evaluation Score -

[0478] 4: No scratches were observed in the image at all.

[0479] 3: Scratches were not visually observable, but could be observed to some extent when magnified.

[0480] 2: Some image scratches were visually observed.

[0481] 1: Image scratches accompanying conveyance were clearly observed.

[0482] - Evaluation Criteria for Image Scratches -

[0483] AA: The average value of the evaluation scores of the five evaluators is 4.0.

[0484] A: The average value of the evaluation scores of the five evaluators is 3.5 or more.

[0485] B: The average value of the evaluation scores of the five evaluators is 3.0 or more and less than 3.5.

[0486] C: The average value of the evaluation scores of the five evaluators is less than 3.0.

[0487] 〔Examples 2 to 11, Comparative Examples 1 to 4〕

[0488] The content of resin particles in the ink,

[0489] The content of wax particles (Cw) in the ink,

[0490] The type of wax in the ink,

[0491] The drying temperature of the ink (specifically, the heating temperature based on the heating roller),

[0492] The surface roughness Ra (RaX) of the outer peripheral surface of the guide roller,

[0493] the dynamic friction coefficient of the outer peripheral surface of the guide roller, and

[0494] the type of fluororesin in the surface layer of the guide roller

[0495] The above items were changed as shown in Table 1. Other than that, the same operations as in Example 1 were performed.

[0496] The results are shown in Table 1.

[0497] The details of the types of wax in Table 1 are as follows.

[0498] · AQ531… "AQUACER 531" (PE wax emulsion) manufactured by BYK Japan KK.

[0499] · AQ593… "AQUACER 593" (PP wax emulsion) manufactured by BYK Japan KK.

[0500] · E6314… "Hi-Tech E-6314" (PE wax emulsion) manufactured by Toho Chemical Industry Co., Ltd.

[0501] The types of fluororesin in the surface layer of the guide roller in Table 1 are as follows.

[0502] · FEP… Tetrafluoroethylene-hexafluoropropylene copolymer

[0503] · PTFE… Polytetrafluoroethylene

[0504]

[0505] As shown in Table 1,

[0506] the total content of the pigment, resin (i.e., pigment dispersion resin and resin particles), and wax relative to the total amount of the ink is 5.0 mass% to 11.0 mass%,

[0507] the drying temperature of the ink during heat drying is 120°C or higher and lower than the melting point of the wax,

[0508] When the content of the wax relative to the total amount of the ink is set as Cw mass% and the surface roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is set as RaX μm, the RaX / Cw ratio is 1.0 to 4.0.

[0509] In Examples 1 to 11, it was possible to suppress a decrease in the ejection property of the ink and to suppress image scratches.

[0510] In contrast, in Comparative Example 1 where the drying temperature of the ink during heat drying exceeded the melting point of the wax, image scratches occurred.

[0511] Moreover, in Comparative Example 2 where the total content of the pigment, resin (i.e., pigment-dispersed resin and resin particles), and wax exceeded 11.0% by mass relative to the total amount of the ink, the ejectability of the ink decreased.

[0512] Moreover, in Comparative Example 3 where the RaX / Cw ratio exceeded 4.0, image scratches occurred.

[0513] Moreover, in Comparative Example 4 where the RaX / Cw ratio was less than 1.0, the ejectability of the ink decreased.

[0514] From the results of Examples 8 and 9, it can be seen that when the Cw / Ct ratio is 0.10 or more (Example 8), image scratches can be further suppressed.

[0515] From the results of Examples 8 and 10, it can be seen that when the Cw / Ct ratio is 0.30 or less (Example 8), the decrease in the ejectability of the ink can be further suppressed.

[0516] From the results of Examples 8 and 9, it can be seen that when the Cw / Cp ratio is 0.50 or more (Example 8), image scratches can be further suppressed.

[0517] From the results of Examples 8 and 10, it can be seen that when the Cw / Cp ratio is 1.50 or less (Example 8), the decrease in the ejectability of the ink can be further suppressed.

[0518] From the results of Examples 8 and 9, it can be seen that when "wax / pigment" is "Y" in the TOF-SIMS analysis (i.e., when the peak intensity of the wax is stronger than the peak intensity of the pigment) (Example 8), image scratches can be further suppressed.

[0519] The entire contents of the invention of Japanese Patent Application No. 2022-189590 filed on November 28, 2022 are incorporated herein by reference.

[0520] 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 incorporated by reference were specifically and separately described.

Claims

1. An inkjet recording method, comprising the steps of: while conveying a recording medium at a conveyance speed of 60 m / min or more, applying ink to the recording medium by an inkjet method; and while conveying the recording medium to which the ink has been applied at a conveyance speed of 60 m / min or more, heating and drying the ink applied to the recording medium to obtain an image, wherein the heating and drying is performed using a heating and drying device, the heating and drying device includes: a heating roller that contacts a non-ink-applied surface of the recording medium to which the ink has been applied and heats the ink applied to the recording medium through the recording medium; and a guide roller that contacts an ink-applied surface of the recording medium to which the ink has been applied and guides the recording medium to which the ink has been applied, the ink contains water, a pigment, a resin, and wax, the total content of the pigment, the resin, and the wax is 5.0% by mass to 11.0% by mass relative to the total amount of the ink, the drying temperature of the ink during the heating and drying is 120°C or more and below the melting point of the wax, when the content of the wax is set to Cw% by mass relative to the total amount of the ink and the arithmetic mean roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is set to RaX μm, the RaX / Cw ratio is 1.0 to 4.

0.

2. The inkjet recording method according to claim 1, wherein, when the content of the wax is set to Cw% by mass relative to the total amount of the ink and the total content of the pigment, the resin, and the wax is set to Ct% by mass relative to the total amount of the ink, the Cw / Ct ratio is 0.10 to 0.

30.

3. The inkjet recording method according to claim 1, wherein, when the content of the wax is set to Cw% by mass relative to the total amount of the ink and the content of the resin is set to Cp% by mass relative to the total amount of the ink, the Cw / Cp ratio is 0.50 to 1.

50.

4. The inkjet recording method according to claim 1, wherein, the dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.03 to 0.

10.

5. The inkjet recording method according to claim 1, wherein, the guide roller includes a surface layer containing a fluororesin.

6. The inkjet recording method according to claim 1, wherein, the conveyance speed of the recording medium during ink application and during the heating and drying is 100 m / min or more.

7. The inkjet recording method according to claim 1, wherein, in TOF-SIMS analysis of the surface of the image, the peak intensity of the wax is stronger than the peak intensity of the pigment.

8. The inkjet recording method according to claim 1, wherein the resin contains resin particles, the content of the resin particles is 0.3% by mass to 5.0% by mass relative to the total amount of the ink.

9. An inkjet recording apparatus for use in the inkjet recording method according to any one of claims 1 to 8, and including an inkjet head for applying the ink to the recording medium and the heating and drying device.

Images