Inkjet recording method and inkjet recording apparatus

Abstract

An inkjet recording method includes: a step of applying an ink; and a step of heating and drying the ink by using a heating and drying device, the heating and drying device comprising: a heating roller; and a guide roller that is in contact with ink applied to the recording medium, guides the recording medium, and causes the ink non-applied surface of the recording medium to be in contact with the heating roller, the ink containing water, a pigment, a pigment dispersion resin, and an acrylic resin that is a resin other than the pigment dispersion resin, the product of the acid value AmgKOH / g of the acrylic resin and the dynamic friction coefficient B of the outer peripheral surface of the guide roller is 1.0-5.0.

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 carried out.

[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] However, in inkjet recording, when using a heat drying device including a guide roller that contacts the ink applied to a recording medium (for example, the drying device described in Patent Document 1 above and the drying mechanism described in Patent Document 2 above), image defects sometimes occur. On the other hand, when attempting to suppress image defects using the components in the ink, the ejectability of the inkjet head sometimes decreases.

[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 image defects and suppressing a decrease in the ejection property of ink.

[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] a step of applying ink to a recording medium by an inkjet method; and

[0014] a step of heating and drying the ink applied to the recording medium while conveying the recording medium to which the ink has been applied,

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

[0016] The heating and drying device includes:

[0017] a heating roller that contacts the 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

[0018] a guide roller that contacts the 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,

[0019] The ink contains water, a pigment, a pigment dispersion resin, and an acrylic resin as an adhesive resin,

[0020] When the acid value of the acrylic resin is represented in units of mgKOH / g as A and the dynamic friction coefficient of the outer peripheral surface of the guide roller is represented as B, the product of A and B is 1.0 to 5.0.

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

[0022] the acid value of the acrylic resin is 20 mgKOH / g to 80 mgKOH / g.

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

[0024] When the acid value of the acrylic resin is represented in units of mgKOH / g as A and the drying temperature of the ink in the heating and drying is represented in units of °C as T1, the ratio of A / T1 is 0.50 or less.

[0025] <4> The inkjet recording method according to any one of <1> to <3>, wherein

[0026] When the glass transition temperature of the acrylic resin expressed in °C is set as T2 and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set as B, the T2 / B ratio is 1000 or more.

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

[0028] When the weight average molecular weight of the acrylic resin is set as C and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set as B, the value obtained by dividing the C / B ratio by 1000 is 100 or more.

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

[0030] When the glass transition temperature of the acrylic resin expressed in °C is set as T2 and the drying temperature of the ink in the heat drying expressed in °C is set as T1, the absolute value of the difference between T2 and T1 is 60 or less.

[0031] <7>The inkjet recording method according to any one of <1> to <6>, wherein,

[0032] The guide roller includes a surface layer containing a fluororesin.

[0033] <8>The inkjet recording method according to any one of <1> to <7>, wherein,

[0034] The dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.03 to 0.08.

[0035] <9>The inkjet recording method according to any one of <1> to <8>, wherein,

[0036] The arithmetic mean roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is 2 μm to 8 μm.

[0037] <10>The inkjet recording method according to any one of <1> to <9>, wherein,

[0038] The glass transition temperature of the acrylic resin expressed in °C is 50°C or more.

[0039] <11>The inkjet recording method according to any one of <1> to <10>, wherein,

[0040] The weight average molecular weight of the acrylic resin is 5000 to 150000.

[0041] <12>The inkjet recording method according to any one of <1> to <11>, wherein,

[0042] The acrylic resin includes a structural unit derived from styrene.

[0043] <13>According to the inkjet recording method according to any one of <1> to <12>, wherein,

[0044] The acrylic resin is a water-soluble resin.

[0045] <14>According to the inkjet recording method according to any one of <1> to <13>, wherein,

[0046] The ink further contains a silicone-based surfactant.

[0047] <15>According to the inkjet recording method according to any one of <1> to <14>, wherein,

[0048] The heating and drying device includes a plurality of heating rollers,

[0049] Further includes the following conveyance path as the conveyance path for conveying the recording medium to which the ink is applied:

[0050] The first conveyance path, the recording medium to which the ink is applied is conveyed while being in contact with the plurality of heating rollers; and

[0051] The second conveyance path, the recording medium after passing through the first conveyance path is conveyed while being in contact with at least one of the plurality of heating rollers that are in contact on the first conveyance path again by being guided by a guide roller.

[0052] <16>An inkjet recording device for the inkjet recording method according to any one of <1> to <15>, and includes an inkjet head for applying the above ink to the above recording medium and the above heating and drying device.

[0053] Advantages of the Invention

[0054] According to one aspect of the present invention, there is provided an inkjet recording method and an inkjet recording device capable of suppressing image defects and suppressing a decrease in the ejection property of ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Is a diagram conceptually showing an example of an inkjet recording device used in the inkjet recording method of the present invention.

[0056] Figure 2 Is Figure 1 An enlarged explanatory diagram of the heating and drying device in the inkjet recording device related to the shown example. DETAILED DESCRIPTION

[0057] In this specification, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0058] 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 other numerically described ranges. Further, 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.

[0059] 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.

[0060] In this specification, a combination of two or more preferred modes is a more preferred mode.

[0061] In this specification, the term "step" includes not only an independent step, but also, even in cases where it cannot be clearly distinguished from other steps, as long as the intended purpose of the step can be achieved, it is included in this term.

[0062] In this specification, "image" refers to all films, and "image recording" refers to the formation of an image (i.e., a film). Further, the concept of "image" in this specification also includes a solid image.

[0063] 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.

[0064] [[Inkjet recording method]]

[0065] The inkjet recording method of the present invention (hereinafter, also simply referred to as "recording method") is an inkjet recording method including the following steps:

[0066] A step of applying ink to a recording medium by an inkjet method; and

[0067] A step of heating and drying the ink applied to the recording medium while conveying the recording medium to which the ink has been applied,

[0068] The heating and drying is performed using the following heating and drying device,

[0069] The heating and drying device includes:

[0070] A heating roller that contacts the non-ink-applied surface (i.e., the surface on the side opposite to the side to which the ink has been applied) 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

[0071] The guide roller contacts the ink-applied surface (i.e., the surface on the side where ink is applied) of the ink-applied recording medium and guides the ink-applied recording medium.

[0072] The ink contains water, pigments, pigment-dispersing resins, and an acrylic resin as a binder resin (hereinafter, also simply referred to as "acrylic resin").

[0073] When the acid value of the acrylic resin is represented in units of mgKOH / g as A and the dynamic friction coefficient of the outer peripheral surface of the guide roller is B, the product of A and B is 1.0 to 5.0.

[0074] The recording method of the present invention is an image recording method using a heat drying device including the above-described guide roller, which can record an image with suppressed image defects and can suppress a decrease in the ink ejection property from the inkjet head.

[0075] It is considered that this effect is obtained by the product of A and B being in the range of 1.0 to 5.0. Hereinafter, the mechanism of the obtainable effect will be described.

[0076] It is considered that when the acid value of the acrylic resin, that is, A, is too large, the amount of residual moisture increases during the drying process of the ink, and the abrasion resistance of the ink in the state of insufficient drying decreases. As a result, image defects are likely to occur due to the contact between the ink on the recording medium and the guide roller. It is considered that by reducing A, image defects can be suppressed.

[0077] On the other hand, it is considered that when the acid value of the acrylic resin, that is, A, is too small, the re-dissolubility of the acrylic resin in the ink is insufficient. As a result, a film or precipitate of the ink remains near the nozzles of the inkjet head, and sometimes the ink ejection property may decrease. It is considered that by increasing A, a decrease in the ink ejection property can be suppressed.

[0078] Moreover, it is considered that when the dynamic friction coefficient B of the outer peripheral surface of the guide roller is too large, image defects are likely to occur due to the contact between the ink on the recording medium and the guide roller. It is considered that by reducing B, image defects can be suppressed.

[0079] Based on the above viewpoints, in the recording method of the present invention, the product of A and B (i.e., A×B) is limited to the range of 1.0 to 5.0.

[0080] By the product of A and B being 1.0 or more, a decrease in the ink ejection property can be suppressed.

[0081] By the product of A and B being 5.0 or less, image defects can be suppressed.

[0082] <Heat drying device X>

[0083] 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:

[0084] 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

[0085] 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.

[0086] As described above, in the recording method using the heating and drying device X, image defects sometimes occur due to the guide roller that contacts the ink-applied surface.

[0087] Regarding this point, in the recording method of the present invention, by setting the product of A and B to 5.0 or less, even in the recording method using the heating and drying device X, image defects can be suppressed.

[0088] As an example of the heating and drying device X, the following heating and drying device X1 can be cited.

[0089] The heating and drying device X1 includes a plurality of heating rollers,

[0090] It also includes the following conveyance path as the conveyance path for conveying the recording medium with ink applied thereto:

[0091] A first conveyance path through which the recording medium with ink applied thereto is conveyed while contacting the plurality of heating rollers; and

[0092] A second conveyance path through which the recording medium after passing through the first conveyance path is conveyed while contacting at least one of the plurality of heating rollers that it contacted on the first conveyance path again through the guidance of the guide roller.

[0093] By including the second conveyance path through which the recording medium is conveyed while contacting at least one of the plurality of heating rollers that it contacted on the first conveyance path again, the heating and drying device X1 can efficiently perform the heating and drying of the ink.

[0094] 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, increasing the conveyance speed), etc.

[0095] Regarding a specific example of the heating and drying device X, it will be described later (refer to Figure 2 ).

[0096] <Guide roller>

[0097] 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.

[0098] In the present invention, the dynamic friction coefficient of the outer peripheral surface of the guide roll represented by "B" (hereinafter, also referred to as "dynamic friction coefficient (B)") is preferably 0.03 to 0.22, more preferably 0.03 to 0.13, and still more preferably 0.03 to 0.08.

[0099] The dynamic friction coefficient (B) of the outer peripheral surface of the guide roll in the present invention is a value measured by the following method.

[0100] Using a polyurethane rubber ball indenter with an outer diameter of 3 / 8 inch and a rubber hardness of 90 degrees as the measurement indenter, measure the frictional force (gf) of the outer peripheral surface of the guide roll under the conditions of a test load of 50 gf, a speed of 10 mm / second, and a measurement distance of 50 mm. Calculate 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. Calculate the value obtained by dividing the average value of the obtained frictional force (gf) by the test load (gf) as the dynamic friction coefficient of the outer peripheral surface of the guide roll.

[0101] In the following examples, the above measurement was performed using a surface property tester (such as "HAIDON 14FW" manufactured by Shinto Scientific Co., Ltd.).

[0102] The guide roll preferably includes a surface layer containing a fluororesin.

[0103] Thereby, it is easy to reduce the dynamic friction coefficient (B), and thus it is easier to achieve that the product of A and B is 5.0 or less.

[0104] Examples of the fluororesin include the following:

[0105] Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),

[0106] Polytetrafluoroethylene (PTFE),

[0107] Tetrafluoroethylene-hexafluoropropylene copolymer (FEP),

[0108] Ethylene-tetrafluoroethylene copolymer (ETFE),

[0109] Polyvinylidene fluoride (PVDF),

[0110] Polychlorotrifluoroethylene (PCTFE) and

[0111] Tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE).

[0112] The fluororesin contained in the surface layer may be only one kind or two or more kinds.

[0113] The fluororesin contained in the surface layer preferably contains PTFE.

[0114] There is no particular limitation on the core material of the guide roll when the surface layer containing the fluororesin is included as the guide roll.

[0115] Examples of the core material include aluminum, aluminum alloy, stainless steel, etc.

[0116] The surface layer containing the fluororesin can be formed, for example, by coating a primer material on the core material, coating (applying) the fluororesin thereon, and sintering by heat treatment.

[0117] Moreover, the guide roll including the surface layer containing the fluororesin can also be formed by fitting a heat-shrinkable fluororesin hose over the core material and heat-shrinking it with warm air.

[0118] The layer thickness of the surface layer containing the fluororesin is, for example, 100 μm or more, preferably 100 μm to 1000 μm, and more preferably 100 μm to 500 μm.

[0119] The arithmetic mean roughness Ra (hereinafter, also simply referred to as "Ra" or "surface roughness Ra") defined in JIS B0601:2013 of the outer peripheral surface of the guide roll is preferably 2 μm to 15 μm, and more preferably 2 μm to 8 μm.

[0120] When the Ra of the outer peripheral surface of the guide roll is 15 μm or less, it is easy to reduce the dynamic friction coefficient (B), and thus it is easier to achieve that the product of A and B is 5.0 or less.

[0121] When the Ra of the outer peripheral surface of the guide roll is 2 μm or more, the manufacturing applicability of the guide roll is excellent.

[0122] Here, when the guide roll includes the above surface layer, the outer peripheral surface of the guide roll means the surface of the surface layer.

[0123] <Heating roll>

[0124] The heating and drying device X includes a heating roll 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.

[0125] There is no particular limitation on the heating roll, and a known heating roll can be used.

[0126] 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 in the roll body can be cited.

[0127] Examples of the metal as the material of the roll body include aluminum, aluminum alloy, stainless steel, etc.

[0128] Regarding the heating roller, reference can be made, for example, to Japanese Patent Application Laid-Open No. 2020-16355 (paragraphs 0032 to 0037, FIG. 3).

[0129] <Heating drum>

[0130] The heating and drying device X may include a heating drum 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.

[0131] For example, the heating and drying device X1 may include a heating drum 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 between the first conveyance path and the second conveyance path.

[0132] Thereby, the heating and drying of the ink can be performed more efficiently.

[0133] Regarding the heating drum, reference can also be made, for example, to the structure of the heating roller described in Japanese Patent Application Laid-Open No. 2020-16355 (paragraphs 0032 to 0037, FIG. 3).

[0134] The preferred embodiment of the heating drum is the same as that of the heating roller.

[0135] The diameter of the heating drum is preferably larger than that of the heating roller.

[0136] 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.

[0137] Thereby, the heating and drying of the ink can be performed more efficiently.

[0138] <Hot air drying device>

[0139] 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.

[0140] For example, in the case where a 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.

[0141] <Inkjet recording device including the heating and drying device X>

[0142] The recording method of the present invention can be implemented using an inkjet recording device including the above-described heating and drying device X and an inkjet head.

[0143] Regarding this inkjet recording device, reference can be made, for example, to Japanese Patent Application Laid-Open No. 2020-16355.

[0144] Hereinafter, the above inkjet recording apparatus will be described with reference to the accompanying drawings.

[0145] In the accompanying drawings and the description thereof in the present invention, the same reference numerals are given to substantially the same components (for example, elements or parts), and redundant descriptions may sometimes be omitted.

[0146] Figure 1 FIG. 100 conceptually shows an example of an inkjet recording apparatus used in the inkjet recording method of the present invention.

[0147] As Figure 1 shown, the inkjet recording apparatus 100 includes an ink application unit 111, and the ink application unit 111 includes inkjet heads 111A to 111D that eject and apply ink to a continuous paper 110 as a recording medium.

[0148] In the ink application unit 111, 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 head 111 applies, for example, black (K) ink, cyan (C) ink, magenta (M) ink, and yellow (Y) ink to the continuous paper 110.

[0149] In addition, the types and numbers of colors are not limited to this.

[0150] The ink ejected from each head 111 contains water, a pigment, a pigment dispersion resin, and an acrylic resin as a resin other than the pigment dispersion resin.

[0151] 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.

[0152] 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 winding roller 105.

[0153] 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-described heating and drying device X11 (i.e., the heating and drying device X1 including a heating drum).

[0154] Figure 2 FIG. 104 is an enlarged explanatory view of the heating and drying device 104.

[0155] As Figure 2As shown, the heating and drying device 104 includes a heating roller 11 (11A to 11J) and a heating drum 12 as heating components that contact the non-ink-applied surface of the continuous paper 110 and heat the continuous paper 110.

[0156] In addition, the diameters of the plurality of heating rollers 11 are smaller than the diameter of the heating drum 12.

[0157] The diameters of the plurality of heating rollers 11 may be the same or different.

[0158] The heating and drying device 104 includes guide rollers 13A to 13K that contact the ink-applied surface of the continuous paper 110 with ink applied thereto (specifically, the continuous paper 110 heated by the heating drum 12) and guide the continuous paper 110 with ink applied thereto.

[0159] Here, 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.

[0160] 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.

[0161] In the heating and drying device 104, a conveyance path for the continuous paper 110 is formed by the plurality of heating rollers 11 described above (that is, the heating rollers 11A to 11J. The same applies hereinafter), the heating drum 12, and the plurality of guide rollers 13 (that is, the guide rollers 13A to 13K. The same applies hereinafter).

[0162] Specifically, the continuous paper 110 is conveyed while contacting 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 conveyed while contacting the inner peripheral sides of the plurality of heating rollers 11 again.

[0163] 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.

[0164] And the heating drum 12, like the plurality of heating rollers 11, contacts the non-ink-applied surface side of the continuous paper 110 and heats and dries the ink applied to the continuous paper across the continuous paper 110.

[0165] The plurality of guide rollers 13 guide the continuous paper 110 to the plurality of heating rollers 11 while contacting the ink-applied surface side of the continuous paper 110.

[0166] And the heating and drying device 104 respectively includes:

[0167] 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 roller 11A in the heating and drying device 104; and Figure 2 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.

[0168] During the heating and drying in the heating and drying device 104, first, while the non-ink-applied surface of the continuous paper 110 is in contact with the plurality of heating rollers 11 arranged in an arc shape, the ink is heated through the continuous paper 110.

[0169] Next, while the non-ink-applied surface of the continuous paper 110 is in contact with the heating drum 12 arranged inside the plurality of heating rollers 11 arranged in an arc shape, the ink is heated through the continuous paper 110.

[0170] Then, the continuous paper 110 is guided again to the heating roller 11 by the guide roller 13. While the non-ink-applied surface of the continuous paper 110 is in contact with the heating roller 11 again, the ink is heated through the continuous paper 110.

[0171] Here, in the heating and drying device 104, the heating drum 12 can also be omitted.

[0172] In this case, for example, by changing the heating drum 12 to a guide roller with a smaller diameter, the non-ink-applied surface of the continuous paper 110 can be brought into contact with the heating roller 11 twice, similar to the heating and drying device 104.

[0173] As described above, the heating and drying device 104 includes:

[0174] a first transfer path 10A through which the continuous paper 110 with ink applied is transferred while being in contact with the plurality of heating rollers 11; and

[0175] 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 with the plurality of heating rollers 11 that it contacted on the first transfer path 10A again by being guided by the plurality of guide rollers 13.

[0176] Therefore, the heating and drying of the ink applied to the continuous paper 110 can be efficiently performed.

[0177] Therefore, in the heating and drying device 104, for example, shortening of the heating and drying device, miniaturization of the heating and drying device, etc. can be achieved.

[0178]

[0179] ​On the second conveyance path 10B, the continuous paper 110 does not necessarily have to contact all of the plurality of heating rollers 11 that contact on the first conveyance path 10A.

[0180] On the second conveyance path 10B, the continuous paper 110 only needs to contact at least a part of the plurality of heating rollers 11 that contact on the first conveyance path 10A.

[0181] The heating and drying device 104 includes a third conveyance path between the first conveyance path 10A and the second conveyance path 10B, in which the continuous paper 110 passing through the first conveyance path 10A is conveyed while contacting the heating drum 12.

[0182] Therefore, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0183] 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.

[0184] In this case, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0185] In the heating and drying device 104, a plurality of dryers (not shown), which are warm air drying devices for blowing warm air to the surface of the ink film, can be arranged outside the plurality of heating rollers 11 configured in an arc shape.

[0186] In this case, the heating and drying of the ink applied to the continuous paper 110 can be performed more efficiently.

[0187] 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 dispersion resin, and an acrylic resin as a resin other than the pigment dispersion resin.

[0188] 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, they guide the continuous paper 110.

[0189] 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 (that is, the acrylic resin as a resin other than the pigment dispersion 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.

[0190] In the inkjet recording method using the inkjet recording device 100, it is only necessary that at least one ink and at least one guide roller satisfy the relationship that the product (A×B) is 1.0 to 5.0.

[0191] <Ink

[0192] The ink in the present invention (i.e., the ink used in the recording method of the present invention; the same applies hereinafter) contains water, a pigment, a pigment-dispersing resin, and an acrylic resin as a binder resin.

[0193] The ink in the present invention may contain other components as needed.

[0194] (Water)

[0195] The ink in the present invention contains water.

[0196] 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.

[0197] The upper limit of the water content also depends on the amount 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.

[0198] (Pigment)

[0199] The ink in the present invention contains at least one pigment.

[0200] The pigment can be an organic pigment or an inorganic pigment.

[0201] 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.

[0202] As the azo pigment, for example, azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments can be cited.

[0203] 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.

[0204] As the dye chelate, for example, basic dye-type chelates and acid dye-type chelates can be cited.

[0205] 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.

[0206] As the pigment, for example, the pigments described in Shojiro Ito's "Encyclopedia of Pigments" (published in 2000), W. Herbst, K. Hunger's "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.

[0207] 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. Further, if the volume average particle diameter is 10 nm or more, the light resistance becomes good.

[0208] Moreover, 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.

[0209] The volume average particle diameter and the particle size distribution of the pigment are values measured using a particle size distribution measuring device (for example, Microtrac UPA (registered trademark) EX150 manufactured by Nikkiso Co., Ltd.).

[0210] The content of the pigment is preferably 1% by mass to 20% by mass, more preferably 1% by mass to 10% by mass, based on the total amount of the ink.

[0211] (Pigment-dispersing resin)

[0212] The ink in the present invention contains at least one pigment-dispersing resin.

[0213] In the present invention, the pigment-dispersing resin refers to a resin having a function of dispersing pigments.

[0214] The form of the pigment-dispersing resin is not particularly limited and may be any of a random resin, a block resin, and a graft resin.

[0215] The pigment-dispersing resin is preferably a resin having a crosslinked structure. It is considered that if the pigment-dispersing resin is a resin having a crosslinked structure, the pigment-dispersing resin is less likely to detach from the surface of the pigment, and the dispersion stability of the pigment is high.

[0216] In the present invention, the resin refers to a compound having a weight average molecular weight (Mw) of 1000 or more.

[0217] The method for measuring the weight-average molecular weight (Mw) in the present invention will be described later.

[0218] The resin having a crosslinked structure is not particularly limited as long as it has at least one crosslinked structure in the molecule.

[0219] 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 (NMR), infrared spectroscopy (IR), and thermal analysis, it is possible to comprehensively determine the presence or absence of a crosslinked structure.

[0220] 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.

[0221] In the present invention, "water-soluble" means a property of dissolving 1 g or more in 100 g of water at 25°C. As "water-soluble", a property of dissolving 3 g or more (more preferably 10 g or more) in 100 g of water at 25°C is preferred.

[0222] In addition, even if the uncrosslinked resin is water-soluble, the crosslinked resin is not necessarily water-soluble.

[0223] Examples of the uncrosslinked resin include vinyl resins, acrylic resins, polyurethane resins, and polyester resins. The uncrosslinked resin is preferably an acrylic resin.

[0224] The uncrosslinked resin is preferably a resin having a functional group that can be crosslinked by a crosslinking agent. Examples of the functional group that can be crosslinked 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 that can be crosslinked 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.

[0225] 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.

[0226] Examples of the carboxyl group-containing monomer include (meth)acrylic acid, β-carboxyethyl acrylate, fumaric acid, itaconic acid, maleic acid, and crotonic acid.

[0227] From the viewpoints of crosslinkability and dispersibility, the carboxyl group-containing monomer is preferably (meth)acrylic acid or β-carboxyethyl acrylate, more preferably (meth)acrylic acid.

[0228] 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 still more preferably 10% by mass to 30% by mass, based on the total amount of the uncrosslinked resin.

[0229] 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.

[0230] The structural unit derived from the hydrophobic monomer contained in the copolymer may be only one kind or two or more kinds.

[0231] Examples of the hydrophobic monomer include (meth)acrylic esters having an alkyl group with 1 to 20 carbon atoms, (meth)acrylic esters having an aromatic ring (e.g., benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc.), styrene, and styrene derivatives.

[0232] 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 still more preferably 70% by mass to 90% by mass, based on the total amount of the uncrosslinked resin.

[0233] The uncrosslinked resin is preferably a random copolymer containing at least one of a structural unit derived from a carboxyl group-containing monomer, a structural unit derived from a (meth)acrylic ester having an alkyl group with 1 to 20 carbon atoms, and a structural unit derived from a (meth)acrylic ester having an aromatic ring, more preferably a random copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from a (meth)acrylic ester having an aromatic ring, and still more preferably a copolymer containing a structural unit derived from (meth)acrylic acid and a structural unit derived from benzyl (meth)acrylate.

[0234] 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 still more preferably 7,000 to 100,000.

[0235] 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.

[0236] The crosslinking agent used for crosslinking the uncrosslinked resin is preferably a compound having two or more reaction sites with the uncrosslinked resin (e.g., a resin having a carboxyl group). The crosslinking agent may be used alone or in combination of two or more.

[0237] A preferred combination of a crosslinking agent and an 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 preferred to form a crosslinked structure using a crosslinking agent after dispersing the pigment with the uncrosslinked resin.

[0238] 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, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and trimethylolpropane triglycidyl ether.

[0239] 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.

[0240] The crosslinking agent can also be a commercially available product.

[0241] Examples of commercially available products include Denacol EX-321, EX-821, EX-830, EX-850, and EX-851 (manufactured by Nagase ChemteX Corporation).

[0242] From the viewpoints of the crosslinking reaction rate and the dispersion stability after crosslinking, the molar ratio of the reactive site (e.g., epoxy group) in the crosslinking agent to the reactive site (e.g., carboxyl group) 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.

[0243] The mixing ratio of the pigment and the pigment-dispersing 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.

[0244] (Acrylic resin as the binder resin)

[0245] The ink in the present invention contains at least one acrylic resin as the binder resin.

[0246] In the present invention, the binder resin refers to a resin contained in the ink other than the above-mentioned pigment-dispersing resin.

[0247] In the present invention, the acrylic resin refers to a resin containing at least one of a structural unit derived from (meth)acrylic acid and a structural unit derived from (meth)acrylate.

[0248] The acrylic resin as the binder resin preferably contains at least one structural unit derived from styrene.

[0249] The content of the structural unit derived from styrene relative to the total amount of the acrylic resin as the binder resin is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and still more preferably 10% by mass to 30% by mass.

[0250] The acrylic resin as the binder resin preferably contains at least one structural unit derived from methacrylic acid.

[0251] The structural unit derived from methacrylic acid preferably contains at least one of a carboxyl group and a salt of a carboxyl group. As the salt of a carboxyl group, an alkali metal salt is preferred, and a sodium salt or a potassium salt is more preferred.

[0252] The content of the structural unit derived from methacrylic acid relative to the total amount of the acrylic resin as the binder resin is preferably 1% by mass to 20% by mass, more preferably 2% by mass to 15% by mass.

[0253] The acrylic resin as the binder resin preferably contains at least one structural unit derived from methacrylate.

[0254] As the methacrylate, an alkyl ester of methacrylic acid is preferred, and methyl methacrylate or ethyl methacrylate is more preferred.

[0255] The content of the structural unit derived from methacrylate relative to the total amount of the acrylic resin as the binder resin is preferably 20% by mass to 90% by mass, more preferably 30% by mass to 85% by mass.

[0256] The acrylic resin as the binder resin may contain at least one structural unit derived from acrylate.

[0257] As the acrylate, an alkyl ester of acrylic acid is preferred, and 2-ethylhexyl acrylate is more preferred.

[0258] The content of the structural unit derived from acrylate relative to the total amount of the acrylic resin as the binder resin is preferably 0% by mass to 40% by mass, more preferably 0% by mass to 30% by mass, still more preferably 0% by mass to 20% by mass, and still more preferably 0% by mass to 10% by mass.

[0259] - Acid value (A) -

[0260] In the present invention, the acid value of the acrylic resin as the binder resin is sometimes represented by "A".

[0261] From the viewpoint of further reducing image defects and ejection properties, the acid value (A) of the acrylic resin as the binder resin is preferably 10 mgKOH / g to 100 mgKOH / g, more preferably 20 mgKOH / g to 80 mgKOH / g, still more preferably 25 mgKOH / g to 70 mgKOH / g, and still more preferably 30 mgKOH / g to 60 mgKOH / g.

[0262] In the present invention, the acid value of the acrylic resin as the binder resin is sometimes represented by "A".

[0263] - Glass transition temperature (T2) -

[0264] In the present invention, the glass transition temperature of the acrylic resin as the binder resin is sometimes represented by "T2".

[0265] The glass transition temperature (T2) of the acrylic resin as the binder resin is preferably 5 °C or higher, more preferably 30 °C or higher, and still more preferably 50 °C or higher.

[0266] There is no particular limitation on the upper limit of T2. For example, it is 150 °C, preferably 130 °C, and still more preferably 120 °C.

[0267] As a preferred range of T2, for example, 5 °C to 150 °C can be cited.

[0268] In the present invention, the glass transition temperature (T2) of the acrylic resin as the binder resin refers to the calculated Tg calculated by the following formula (1).

[0269] 1 / Tg = ∑(Xi / Tgi)…(1)

[0270] Here, the polymer to be calculated is assumed to be copolymerized from n monomer components from i = 1 to n. Xi is the mass fraction of the i-th monomer (∑Xi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. Among them, ∑ takes the sum from i = 1 to n. In addition, the value of the glass transition temperature of the homopolymer of each monomer (Tgi) uses the value in Polymer Handbook (3rd Edition) (written by J. Brandrup, E. H. Immergut (Wiley-Interscience, 1989)).

[0271] - Weight-average molecular weight (C) -

[0272] In the present invention, the weight-average molecular weight of the acrylic resin as the binder resin is sometimes represented by "C".

[0273] The weight-average molecular weight (C) of the acrylic resin as the binder resin is preferably from 4,000 to 300,000, more preferably from 4,000 to 200,000, and still more preferably from 5,000 to 150,000.

[0274] In the present invention, the weight-average molecular weight (Mw) represents a value measured by gel permeation chromatography (GPC).

[0275] When measuring by gel permeation chromatography (GPC), use HLC (registered trademark)-8020GPC (manufactured by Tosoh Corporation) as the measuring device, use three TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by Tosoh Corporation) as the columns, and use THF (tetrahydrofuran) as the eluent. And, in the measurement, set the sample concentration to 0.45 mass%, set the flow rate to 0.35 ml / min, set the sample injection volume to 10 μL and set the measurement temperature to 40 °C, and use an RI detector. The calibration curve is made from eight samples of "standard sample TSK standard, polystyrene (polystyrene)": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene" manufactured by Tosoh Corporation.

[0276] The acrylic resin as the binder resin can be a water-soluble resin or resin particles.

[0277] From the viewpoint of the ejection property of the ink, the acrylic resin as the binder resin is preferably a water-soluble resin.

[0278] The definition of "water-soluble" in the water-soluble resin is as described above.

[0279] The content of the acrylic resin as the binder resin relative to the total amount of the ink is preferably from 1 mass% to 20 mass%, more preferably from 1 mass% to 15 mass%, still more preferably from 1 mass% to 10 mass%, and still more preferably from 2 mass% to 8 mass%.

[0280] (Silicone surfactant)

[0281] The ink in the present invention preferably contains at least one silicone surfactant. Thereby, image defects can be further suppressed.

[0282] As the silicone surfactant, a polyether-modified silicone surfactant is preferred, and a compound represented by the following formula (D1) is more preferred.

[0283] [Chemical Formula 1]

[0284]

[0285] In formula (D1), R 1 each independently represents an alkyl group or a hydroxyl group having 1 to 3 carbon atoms, and R 2 represents an alkanediyl group having 2 to 5 carbon atoms, and R 3 represents a hydrogen atom, an alkyl group or a hydroxyl group having 1 to 3 carbon atoms, PO represents propyleneoxy, and EO represents ethyleneoxy. 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.

[0286] In addition, in formula (D1), the arrangement of PO and EO can be a block copolymer arrangement or a random copolymer arrangement.

[0287] 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.

[0288] R 1 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group.

[0289] R 2 is preferably an alkanediyl group having 3 or 4 carbon atoms, more preferably trimethylene.

[0290] R 3 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group.

[0291] 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.

[0292] As the silicone-based surfactant, commercially available products can also be used.

[0293] Examples of commercially available products of the silicone-based surfactant include the following:

[0294] 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, SILFACESAG503A (manufactured by Nissin Chemical Industry Co., Ltd.), TEGOWet KL245, TEGOWet 240, TEGOWet 250, TEGOWet 260, TEGOWet 270, TEGOWet 280 (manufactured by EVONIK Corporation), etc.

[0295] These commercially available products are all compounds represented by formula (D1).

[0296] The content of the silicone 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 0.03% by mass to 1.5% by mass.

[0297] (Surfactants other than silicone surfactants)

[0298] The ink in the present invention may contain at least one surfactant other than the silicone surfactant (hereinafter, also referred to as other surfactants).

[0299] Examples of other surfactants include acetylene glycol surfactants, alkylene oxide adducts of alcohols, etc.

[0300] As the acetylene glycol surfactant, for example, a compound represented by the following formula (A1) is preferably used.

[0301] [Chemical formula 2]

[0302]

[0303] 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.

[0304] a, b, c, and d represent the average addition molar numbers of the respective units, and are each 0 to 50.

[0305] Preferred examples of the acetylene diol-based surfactant include the following:

[0306] 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

[0307] An ethylene oxide adduct of the above acetylene diol, etc.

[0308] 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.

[0309] The acetylene diol-based surfactant can be obtained, for example, by the method described on pages 94 to 107 of "New Surfactant Introduction, Revised Edition" (published by Sanyo Chemical Industries, Ltd. in 1992) written by Takehiko Fujimoto, etc.

[0310] 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), 0LFINE E1004 (HLB value: 7 - 9), 0LFINE 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.

[0311] As the alkylene oxide adduct of an alcohol, the ethylene oxide adduct of an alcohol or the adduct of ethylene oxide and propylene oxide of an alcohol is preferred, and the ethylene oxide adduct of an alcohol is more preferred.

[0312] As the alkylene oxide adduct of an alcohol, the compound represented by the following formula (2) is further preferred.

[0313] R3O - [(EO) m / (PO) n -H... Formula (2)

[0314] 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.

[0315] In formula (2), m and n represent the average addition mole 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.

[0316] In formula (2), “(EO) m / (PO) n ” This notation indicates that the configuration of E0 and PO can be that of a random copolymer or that of a block copolymer. At the position marked as “(E0) m / (P0) n ”, the addition order of E0 and P0 is arbitrary.

[0317] 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, i.e., R0-(PO)(E0)-H, is preferred.

[0318] Moreover, when the compound represented by formula (2) is a block copolymer, it can be a triblock copolymer of R0-(E0)(P0)(E0)-H.

[0319] As commercially available products of alkylene oxide adducts of alcohols,

[0320] As ethylene oxide adducts of lauryl alcohol, examples include 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.

[0321] As ethylene oxide adducts of secondary alcohols having 12 carbon atoms, examples include 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.

[0322] 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.

[0323] 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 3.0% by mass.

[0324] (Water-soluble organic solvent)

[0325] The ink in the present invention may contain at least one water-soluble organic solvent.

[0326] Thereby, the ejection property of the ink can be further improved.

[0327] In the present invention, "water-soluble" in "water-soluble organic solvent" means a property of dissolving 1 g or more in 100 g of water at 25°C.

[0328] The types of water-soluble organic solvents that can be contained in the ink are not limited. For example, the following can be cited:

[0329] Monoalcohols having 1 to 4 carbon atoms;

[0330] 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;

[0331] Triols such as glycerol, 1,2,6-hexanetriol, trimethylolpropane;

[0332] Alkylene diols such as ethylene glycol, propylene glycol (alias 1,2-propanediol);

[0333] Alkylene glycol monoalkyl ethers such as ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether;

[0334] Polyalkylene diols such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol;

[0335] Polyalkylene glycol ethers such as diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glycerol ether;

[0336] 2-pyrrolidone, N-methyl-2-pyrrolidone, etc.

[0337] 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.

[0338] Relative to the total amount of the ink, the content of the water-soluble organic solvent is preferably 10% by mass to 40% by mass, more preferably 15% by mass to 30% by mass.

[0339] (Other components)

[0340] The ink in the present invention may contain other components in addition to the above components as needed.

[0341] 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-proof agents, pH adjusters, defoamers, viscosity regulators, dispersion stabilizers, rust inhibitors, chelating agents, water-soluble polymer compounds, etc. can be cited.

[0342] (Physical properties of the ink)

[0343] - Viscosity -

[0344] 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.

[0345] 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.).

[0346] - pH -

[0347] 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.

[0348] 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 DDK-TOA CORPORATION).

[0349] <The product of A and B>

[0350] As described above, in the recording method of the present invention, the product of the acid value of the acrylic resin expressed in units of mgKOH / g, that is, A, and the dynamic friction coefficient of the outer peripheral surface of the guide roller, that is, B, is 1.0 to 5.0.

[0351] The product of A and B is preferably from 1.0 to 3.5.

[0352] <A / T1 ratio>

[0353] In the recording method of the present invention, when the acid value of the acrylic resin as the binder resin is set to A (expressed in units of mgKOH / g) and the drying temperature of the ink during heat drying in °C is set to T1, from the viewpoint of further suppressing image defects, the A / T1 ratio is preferably 0.70 or less, more preferably 0.60 or less, and still more preferably 0.50 or less.

[0354] The lower limit of the A / T1 ratio is not particularly limited, and the lower limit is, for example, 0.10.

[0355] In the present invention, the drying temperature of the ink during heat drying represented by T1 refers to the maximum temperature reached on the surface of the ink film during heat drying (that is, the film formed by the ink applied to the recording medium. The same applies hereinafter), and is a value measured using a non-contact thermometer.

[0356] In the following examples, FT-H20 manufactured by KEYENCE CORPORATION was used as the non-contact thermometer, and the drying temperature (T1) of the ink during heat drying was measured.

[0357] <T2 / B ratio>

[0358] In the recording method of the present invention, when the glass transition temperature of the acrylic resin as the binder resin in °C is set to T2 and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set to B, from the viewpoint of further suppressing image defects, the T2 / B ratio is preferably 100 or more, more preferably 800 or more, still more preferably 820 or more, and still more preferably 1000 or more.

[0359] The upper limit of the T2 / B ratio is not particularly limited, and the upper limit is, for example, 2500.

[0360] <(C / B ratio) / 1000>

[0361] In the recording method of the present invention, when the weight average molecular weight of the acrylic resin as the binder resin is set to C and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set to B, from the viewpoint of further suppressing image defects, the value obtained by dividing the C / B ratio by 1000, that is, "(C / B ratio) / 1000", is preferably 50 or more, more preferably 60 or more, and still more preferably 100 or more.

[0362] The upper limit of "(C / B ratio) / 1000" is not particularly limited, and the upper limit is, for example, 6000.

[0363] <Absolute value of the difference between T2 and T1>

[0364] In the recording method of the present invention, when the glass transition temperature of the acrylic resin as the binder resin represented in units of °C is set as T2, and the drying temperature of the ink during heat drying represented in units of °C is set as T1, from the viewpoint of further suppressing image defects, the absolute value of the difference between T2 and T1, that is, |T1 - T2| is preferably 120 or less, more preferably 70 or less, and still more preferably 60 or less.

[0365] <Recording medium>

[0366] 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 or the like which is usually not surface-treated and has cellulose as the main body.

[0367] The coated paper can usually be a 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 C0., 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.

[0368] The recording medium can be a low water absorption recording medium or a non-water absorption recording medium.

[0369] In the present invention, the low water absorption recording medium means a recording medium having a water absorption coefficient Ka of 0.05 mL / m 2 ·ms 1 / 2 ~0.5 mL / m 2 ·ms 1 / 2 Preferably, it is 0.1 mL / m 2 ·ms 1 / 2 ~0.4 mL / m 2 ·ms 1 / 2 More preferably, it is 0.2 mL / m 2 ·ms 1 / 2 ~0.3 mL / m 2 ·ms 1 / 2 .

[0370] Moreover, the non-water absorption recording medium means a recording medium having a water absorption coefficient Ka less than 0.05 mL / m 2 ·ms 1 / 2 of the recording medium.

[0371] The water absorption coefficient Ka has the same meaning as described in JAPAN TAPPI Pulp Test Method N0.51:2000 (Published by Japan Technical Association of the Pulp and Paper Industry). Specifically, the absorption coefficient Ka is calculated from the difference in the amount of water transferred at contact times of 100 ms and 900 ms using an automatic scanning liquid absorber KM500Win (manufactured by KUMAGAI RIKI KOGYO Co., Ltd.).

[0372] The non-absorbent 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.

[0373] The resin substrate preferably contains polypropylene, polyethylene terephthalate, nylon, polyethylene, or polyimide.

[0374] The resin substrate can be a transparent resin substrate, a colored resin substrate, or can be subjected to metal vapor deposition treatment on at least a part thereof, etc.

[0375] The shape of the resin substrate is not particularly limited, but a sheet-shaped 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-shaped resin substrate is more preferred.

[0376] Examples

[0377] Hereinafter, the present invention will be further specifically described using examples, but the present invention is not limited to the following examples as long as it does not exceed its gist.

[0378] When preparing each ink, each pigment dispersion and binder resin were previously prepared, and each ink was prepared using them.

[0379] <Synthesis of water-soluble resin as pigment dispersion resin precursor>

[0380] As a precursor of crosslinked resin 1 which is a pigment dispersion resin described later, water-soluble resin 1 (resin before crosslinking) was synthesized.

[0381] The following shows the details.

[0382] 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).

[0383] Furthermore, 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).

[0384] Next, isopropyl alcohol (187.5 parts by mass) was heated to 80°C under a nitrogen atmosphere, and a mixture of a monomer supply composition and an 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 to obtain a water-soluble resin 1 (methacrylic acid / benzyl methacrylate copolymer). The weight-average molecular weight of the obtained water-soluble resin 1 was about 30,000, and the acid value was 112 mgKOH / g.

[0385] <Preparation of Magenta Pigment Dispersion>

[0386] 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, obtaining an aqueous solution of water-soluble resin Q-1.

[0387] Water-soluble resin Q-1 is a neutralized product of water-soluble resin 1 in which the carboxyl group (-C(=0)OH group) in the above water-soluble resin 1 is changed to a -C(=0)ONa group.

[0388] An aqueous solution of water-soluble resin Q-1 (124 parts by mass), a magenta pigment (Pigment Red 122, Chromofine Red, 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 diameter was obtained, thereby obtaining a dispersion (uncrosslinked dispersion) in which the magenta pigment was dispersed by water-soluble resin Q-1. The pigment concentration of the magenta pigment in the uncrosslinked dispersion was 15% by mass.

[0389] 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 water-soluble resin Q-1 with the crosslinking agent.

[0390] Thus, a dispersion liquid (crosslinked dispersion liquid) in which the magenta pigment is dispersed by the crosslinked resin 1 as a pigment-dispersing resin was obtained. Here, the crosslinked resin 1 is a pigment-dispersing resin obtained by crosslinking the water-soluble resin Q-1 with the above crosslinking agent.

[0391] Next, ion-exchanged water was added to the obtained crosslinked dispersion liquid, and ultrafiltration was performed using a stirring type Ultra Holder (manufactured by ADVANTEC C0., LTD.) and an ultrafiltration filter (manufactured by ADVANTEC C0., LTD., cut-off molecular weight 50,000, Q0500076E ultrafilter). After purification so that the concentration of dipropylene glycol in the crosslinked dispersion liquid became 0.1 mass% or less, it was concentrated until the pigment concentration became 15 mass%, whereby a magenta pigment dispersion liquid (magenta pigment concentration 15 mass%) in which the magenta pigment was dispersed by the crosslinked resin 1 was obtained.

[0392] <Production of Aqueous Solution of Binder Resin P1 (Acrylic Water-Soluble Resin)>

[0393] 93.4 parts of butanol was charged into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and purged with nitrogen. The inside of the reaction vessel was heated to 110 °C, and a mixture of 8 parts of methacrylic acid, 15 parts of styrene, and 77 parts of methyl methacrylate as polymerizable monomers and 9 parts of V-601 (manufactured by Wako Pure Chemical, Ltd.) as a polymerization initiator was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the reaction was further continued at 110 °C for 3 hours, then 0.9 part of V-601 (manufactured by Wako Pure Chemical, Ltd.) was added, and the reaction was further continued at 110 °C for 1 hour to obtain a binder resin 1 as an acrylic resin.

[0394] Next, after cooling the above binder resin 1 to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization, and then 100 parts of water was added for water solubilization. The obtained solution was heated to 100 °C or higher, and butanol was distilled off by azeotropic distillation of butanol and water, and adjusted so that the solid content became 50 mass%, whereby an aqueous solution of binder resin P1 (solid content 50 mass%) was obtained. Here, binder resin P1 is an acrylic water-soluble resin obtained by water solubilizing binder resin 1 (that is, an acrylic resin as a water-soluble resin. The same shall apply hereinafter).

[0395] The acid value (A), calculated Tg (T2), and weight-average molecular weight (C) of binder resin P1 are shown in Table 1, respectively.

[0396] <Production of Aqueous Solutions of Binder Resins P2 to P10 and P12 (Acrylic Water-Soluble Resins)>

[0397] The polymerizable monomer was changed to the monomers at the ratios described in Tables 1 and 2, and the amount of polymerization initiator V-601 was adjusted so as to achieve the weight-average molecular weight of each binder resin. Also, the amount of dimethylaminoethanol used in neutralization was adjusted so that the neutralization degree of the acrylic resin became 100%. Aqueous solutions (solid content: 50% by mass) of each of binder resins P2 to P10 and P12 were obtained in the same manner as the aqueous solution of binder resin P1.

[0398] The acid value (A), calculated Tg (T2), and weight-average molecular weight (C) of each of binder resins P2 to P10 and P12 are shown in Table 1.

[0399] <Preparation of Aqueous Dispersion of Binder Resin Particles P11>

[0400] As the aqueous dispersion of binder resin particles P11, an aqueous dispersion of styrene acrylic resin particles “QE-1042” (solid content: 40% by mass) manufactured by Seiko PMC Corporation was prepared.

[0401] The acid value (A), calculated Tg (T2), and weight-average molecular weight (C) of binder resin particles P11 are shown in Table 2.

[0402] There is no data (N.D.) on the constituent units and structural ratios in binder resin particles P11.

[0403] 〔Examples 1 to 24, Comparative Examples 1 to 3〕

[0404] <Preparation of Magenta Ink>

[0405] The respective components shown in Tables 1 and 2 were mixed to the contents (mass %) described in each table. Then, coarse particles were removed from the mixed solution using a 1-μm filter, and magenta inks for each example and each comparative example were prepared.

[0406] The details of the respective components described in Tables 1 and 2 are as follows.

[0407] The amounts of the respective components in Tables 1 and 2 are the amounts as solid components.

[0408] The amounts of water and organic solvents contained in components with a solid component concentration of not 100% by mass are included in the items of “water” and “organic solvent”.

[0409] The blanks in Tables 1 and 2 indicate that the corresponding components are not contained.

[0410] (Pigment Dispersion Liquid)

[0411] · Pigment dispersion liquid: The magenta pigment dispersion liquid prepared above (aqueous dispersion liquid with a pigment concentration of 15% by mass)

[0412] (Water-soluble organic solvent)

[0413] · PG: Propylene glycol (manufactured by ADEKA CORPORATION)

[0414] · 1,2-BDO: 1,2-Butanediol (manufactured by Mitsubishi Chemical Corporation)

[0415] · DEGmEE: Diethylene glycol ethyl ether (manufactured by Nippon Nyukazai Co., Ltd.)

[0416] · DEGiPrE: Diethylene glycol isopropyl ether (manufactured by Nippon Nyukazai Co., Ltd.)

[0417] (Surfactant)

[0418] · TEGO Wet 280: Polyether-modified silicone-based nonionic surfactant, manufactured by Evonik Industries AG)

[0419] · Surfynol 104: Acetylenic diol-based nonionic surfactant (propylene glycol dispersion with a solid component concentration of 50%, manufactured by Evonik Industries AG, trade name: Surfynol 104PG50)

[0420] · EMULGEN 120: Polyoxyethylene lauryl ether, nonionic surfactant (manufactured by Kao Corporation)

[0421] (Wax)

[0422] · Hi-Tech E-6314: Aqueous dispersion of polyethylene wax (aqueous dispersion with a solid component concentration of 35% by mass, manufactured by Toho Chemical Industry Co., Ltd.)

[0423] <Inkjet recording>

[0424] An inkjet recording device having the same structure as the Figure 1 shown inkjet recording device was prepared. As each inkjet head in the inkjet recording device, an inkjet recording linear head "KJ4B-1200" (manufactured by KYOCERA Corporation) was used.

[0425] The prepared magenta ink is ejected from one of the inkjet heads in the above inkjet recording apparatus and applied to the recording medium. While the recording medium with the ink applied is conveyed, the ink applied to the recording medium is heated and dried, thereby performing inkjet recording.

[0426] The detailed conditions for inkjet recording are as follows.

[0427] <Conditions for Inkjet Recording>

[0428] · Recording medium: Product name “OK TOP COAT”, manufactured by OJI PAPER CO., LTD. (Water absorption: 4.9 g / m 2 )

[0429] · Conveying mechanism of the recording medium: Roll-to-roll

[0430] · Temperature of the inkjet head: 32°C

[0431] · Resolution of the inkjet head: 1200×1200 [dpi (dot per inch)]

[0432] · Ejected droplet size of the ink: 3.0 [pL]

[0433] · Environment around the inkjet head: Temperature 25°C ± 1°C, relative humidity 25°C ± 5%

[0434] · Conveying speed: 80 [m / minute]

[0435] · Tension of the recording medium during conveyance: 60 N

[0436] · Recorded image: Solid image

[0437] · Heating method: Heating roller (heating temperature adjusted so that the temperature of the surface of the ink film becomes the “drying temperature (T1) (°C) of the ink during heating and drying” described in Tables 1 and 2), 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-applied surface of the recording medium.

[0438] · Guide roller, heating roller, heating drum: Prepared according to paragraphs 0063 to 0082 of Japanese Unexamined Patent Application Publication No. 2020-16355.

[0439] The following matters in inkjet recording are shown in Tables 1 and 2.

[0440] · Material of the surface layer of the guide roller

[0441] ·Coefficient of kinetic friction (B) of the outer peripheral surface of the guide roller

[0442] ·Surface roughness Ra (nm) of the guide roller

[0443] ·Product (A × B) of the acid value (A) of the acrylic resin as the binder resin and the coefficient of kinetic friction (B) of the outer peripheral surface of the guide roller

[0444] ·Ratio of the acid value (A) of the acrylic resin as the binder resin to the drying temperature (T1) (°C) of the ink during heat drying, i.e., A / T1 ratio

[0445] ·Ratio of the calculated Tg (T2) (°C) of the acrylic resin as the binder resin to the coefficient of kinetic friction (B) of the outer peripheral surface of the guide roller, i.e., T2 / B ratio

[0446] ·Value obtained by dividing the ratio of the weight average molecular weight (C) of the acrylic resin as the binder resin to the coefficient of kinetic friction (B) of the outer peripheral surface of the guide roller, i.e., C / B ratio, by 1000, i.e., (C / B ratio) / 1000

[0447] ·Absolute value of the difference between the drying temperature (T1) (°C) of the ink during heat drying and the calculated Tg (T2) (°C) of the acrylic resin as the binder resin, i.e., |T1 - T2|

[0448] <Evaluation of ink ejection property>

[0449] Using the above inkjet recording apparatus and the above magenta ink, a nozzle check pattern as a solid image with a Duty of 100% was continuously recorded in a region with a length of 5000 m of the recording medium. The last 10 m of the image recording section was cut out, and the number of nozzle missings was visually observed in the nozzle check pattern, and the ink ejection property was evaluated according to the following evaluation criteria.

[0450] In the following evaluation criteria, the grade with the most excellent ink ejection property is A.

[0451] - Evaluation criteria for ink ejection property -

[0452] A: No nozzle missing.

[0453] B: The number of nozzle missings is 1 - 3.

[0454] C: The number of nozzle missings is 4 - 10.

[0455] D: The number of nozzle missings is 11 - 20.

[0456] E: The number of nozzle missings is more than 21.

[0457] Here, "nozzle missing" means that there is a nozzle that does not eject ink and there are white streaks.

[0458] <Evaluation of Image Defects>

[0459] Using the above inkjet recording apparatus and the above magenta ink, a solid image with a Duty of 100% was continuously recorded in an area of 10 m in length of the recording medium. A sample of A4 size was cut out from the image recording section. The solid image in the cut-out sample was observed visually and under a microscope. The observation range was set to the entire A4 size. Based on the observed results, the image defects were evaluated according to the following evaluation criteria.

[0460] In the following evaluation criteria, the grade with the best suppression of image defects is A.

[0461] - Evaluation Criteria for Image Defects -

[0462] A: No point defects are generated in microscopic observation.

[0463] B: Less than 3 point defects that cannot be visually confirmed but can be confirmed by microscopic observation.

[0464] C: Less than 10 point defects that cannot be visually confirmed but can be confirmed by microscopic observation.

[0465] D: More than 10 point defects that can be visually confirmed and are generated locally.

[0466] E: Point defects that can be visually confirmed are generated over the entire surface.

[0467]

[0468]

[0469] As shown in Table 1 and Table 2, in Examples 1 to 24 where the product (A × B) of the acid value (A) of the acrylic resin as the binder resin and the dynamic friction coefficient (B) of the outer peripheral surface of the guide roller is 1.0 to 5.0, image defects are suppressed and a decrease in ink ejection property is also suppressed.

[0470] In contrast, in Comparative Example 3 where the product (A × B) is less than 1.0, the ink ejection property decreases.

[0471] Moreover, in Comparative Examples 1 and 2 where the product (A × B) exceeds 5.0, image defects are obvious.

[0472] From the results of Examples 1 and 10, it can be seen that when the ratio of the acid value (A) of the acrylic resin to the drying temperature T1 (°C) of the ink during heat drying, i.e., the A / T1 ratio, is 0.50 or less (Example 1), image defects can be further suppressed.

[0473] From the results of Examples 11 to 13, it can be seen that when the ratio of the glass transition temperature (T2) of the acrylic resin to the dynamic friction coefficient (B) of the outer peripheral surface of the guide roller, i.e., the T2 / B ratio, is 1000 or more (Example 11), image defects can be further suppressed.

[0474] From the results of Examples 15 and 16, it can be seen that when the value obtained by dividing the ratio of the weight average molecular weight (C) of the acrylic resin to the dynamic friction coefficient (B) of the outer peripheral surface of the guide roller by 1000, i.e., (C / B ratio) / 1000, is 100 or more (Example 15), image defects can be further suppressed.

[0475] From the results of Examples 18 and 19, it can be seen that when the absolute value of the difference between the glass transition temperature (T2) of the acrylic resin and the drying temperature (T1) of the ink during heat drying, i.e., |T2 - T1|, is 60 or less (Example 18), image defects can be further suppressed.

[0476] From the results of Examples 2 and 14, it can be seen that when the guide roller includes a surface layer containing a fluororesin (Example 2), image defects can be further suppressed.

[0477] From the results of Examples 2, 6, 7, and 14, it can be seen that when the dynamic friction coefficient of the outer peripheral surface of the guide roller is 0.03 to 0.08 (Examples 2 and 6), image defects can be further suppressed.

[0478] From the results of Examples 1 and 20, it can be seen that when the surface roughness Ra of the outer peripheral surface of the guide roller is 2 μm to 8 μm (Example 1), image defects can be further suppressed.

[0479] From the results of Examples 11 to 13, it can be seen that when the glass transition temperature of the acrylic resin is 50°C or more (Example 11), image defects can be further suppressed.

[0480] From the results of Examples 21 and 22, it can be seen that when the weight average molecular weight of the acrylic resin is 5000 to 150000 (Example 21), the ink ejection property is further improved.

[0481] From the results of Examples 21 and 23, it can be seen that when the acrylic resin is a water-soluble resin (Example 21), the ink ejection property is further improved.

[0482] From the results of Examples 1 and 24, it can be seen that when the ink contains a silicone-based surfactant (Example 1), image defects can be further suppressed.

[0483] The entire content of the invention of Japanese Patent Application No. 2022-189591 filed on November 28, 2022 is incorporated herein by reference.

[0484] All documents, patent applications, and technical standards cited in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually set forth.

Claims

1. An inkjet recording method, comprising the following steps: A step of applying ink to a recording medium by an inkjet method; and A step of heating and drying the ink applied to the recording medium while conveying the recording medium to which the ink has been applied, wherein the heating and drying is performed by 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 pigment dispersion resin, and an acrylic resin as an adhesive resin, when the acid value of the acrylic resin expressed in units of mgKOH / g is set as A and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set as B, the product of A and B is 1.0 to 5.

0.

2. The inkjet recording method according to claim 1, wherein the acid value of the acrylic resin is 20 mgKOH / g to 80 mgKOH / g.

3. The inkjet recording method according to claim 1, wherein when the acid value of the acrylic resin expressed in units of mgKOH / g is set as A and the drying temperature of the ink in the heating and drying expressed in units of °C is set as T1, the ratio of A / T1 is 0.50 or less.

4. The inkjet recording method according to claim 1, wherein when the glass transition temperature of the acrylic resin expressed in units of °C is set as T2 and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set as B, the ratio of T2 / B is 1000 or more.

5. The inkjet recording method according to claim 1, wherein when the weight average molecular weight of the acrylic resin is set as C and the dynamic friction coefficient of the outer peripheral surface of the guide roller is set as B, the value obtained by dividing the ratio of C / B by 1000 is 100 or more.

6. The inkjet recording method according to claim 1, wherein when the glass transition temperature of the acrylic resin expressed in units of °C is set as T2 and the drying temperature of the ink in the heating and drying expressed in units of °C is set as T1, the absolute value of the difference between T2 and T1 is 60 or less.

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

8. 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.

08.

9. The inkjet recording method according to claim 1, wherein the arithmetic mean roughness Ra specified in JIS B0601:2013 of the outer peripheral surface of the guide roller is 2 μm to 8 μm.

10. The inkjet recording method according to claim 1, wherein the glass transition temperature of the acrylic resin expressed in units of °C is 50 °C or higher.

11. The inkjet recording method according to claim 1, wherein the weight average molecular weight of the acrylic resin is 5000 to 150000.

12. The inkjet recording method according to claim 1, wherein the acrylic resin contains a structural unit derived from styrene.

13. The inkjet recording method according to claim 1, wherein the acrylic resin is a water-soluble resin.

14. The inkjet recording method according to claim 1, wherein the ink further contains a silicone surfactant.

15. The inkjet recording method according to claim 1, wherein the heating and drying device includes a plurality of the heating rollers, and further includes the following conveyance path as a conveyance path for conveying the recording medium to which the ink is applied: a first conveyance path, in which the recording medium to which the ink is applied is conveyed while being in contact with the plurality of the heating rollers; and a second conveyance path, in which the recording medium after passing through the first conveyance path is conveyed while being in contact again with at least one of the plurality of the heating rollers that it contacted in the first conveyance path by being guided by the guide roller.

16. An inkjet recording apparatus, which is used for the inkjet recording method according to any one of claims 1 to 15, and includes an inkjet head that applies the ink to the recording medium and the heating and drying device.

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