Inkjet recording method, inkjet recording device, and set of aqueous ink and aqueous reaction liquid

Abstract

To provide an inkjet recording method which suppresses image unevenness when ink and a reaction liquid are applied and an image is recorded, suppresses blurring of an image when the image is continuously recorded, and can suppress image unevenness of a write-out part of the image when the image is recorded after stopping for a fixed time.SOLUTION: An inkjet recording method records an image on a recording medium using an aqueous reaction liquid containing aqueous ink and a reaction agent, wherein the reaction agent contains a cationic resin, the cationic resin contains a first cationic resin having a peak in a region of a molecular weight of 100,000 or more and 500,000 or less, and a second cationic resin having a peak in a region of a molecular weight of 2,000 or more and less than 100,000, in molecular weight distribution measured by GPC, and a content (mass%) of the second cationic resin is 0.01 time or more and 8.0 time or less in a mass ratio to a content (mass%) of the first cationic resin.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method, an inkjet recording apparatus, and a set of an aqueous ink and an aqueous reaction liquid. [Background technology]

[0002] It is known that an inkjet recording device ejects minute ink droplets from nozzles of a recording head to record an image on a recording medium. In recent years, there has been a demand for recording images on recording media that have low ink absorbency (e.g., art paper having a coating layer, etc., hereinafter also referred to as low-absorbency recording media) or recording media that do not absorb ink (e.g., plastic film, etc., hereinafter also referred to as non-absorbency recording media). In addition, the use of aqueous inks as inks has been considered from the viewpoints of environment and safety.

[0003] Up until now, practical image quality has been obtained using water-based inks as described above on recording media with high ink absorption such as plain paper. However, on recording media with low ink absorption or non-absorbent recording media, the ink droplets that land on the recording media are hardly absorbed or are hardly absorbed at all, so that the image is hardly fixed by absorbing the ink. As a result, the ink droplets coalesce on the recording media, causing bleeding and unevenness in the image, making it difficult to obtain practical image quality.

[0004] To address the above-mentioned issues, it has been proposed to use a reaction liquid containing a cationic substance that reacts with solids such as pigments and resins in the ink to cause aggregation or thickening (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-224955 [Patent Document 2] International Publication No. 2019 / 116536 Summary of the Invention [Problem to be solved by the invention]

[0006] Using the reaction liquid and ink described in Patent Documents 1 and 2, an image was printed on a low-absorbency recording medium by applying the ink and reaction liquid using an inkjet recording head, and the result was that the bleeding and unevenness of the image was reduced.

[0007] However, according to the study by the present inventors, when a large number of images are continuously recorded using the above-mentioned reaction liquid and ink, it has been found that the images become faint.Furthermore, it has been found that when the above-mentioned reaction liquid is ejected again after a certain period of pause in the ejection operation, ejection failure occurs at the start of the image, and as a result, image unevenness occurs at the start of the image.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method capable of suppressing image unevenness when an image is recorded by applying ink and a reaction liquid to a recording medium by ejection from an inkjet recording head, suppressing blurring of the image when images are continuously recorded, and further suppressing image unevenness at the start of writing of the image when an image is recorded after a certain period of rest. Another object of the present invention is to provide an inkjet recording device used in this inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, the inkjet recording method comprising: a reaction liquid applying step of ejecting the aqueous reaction liquid from an inkjet recording head and applying it to the recording medium; and an ink applying step of ejecting the aqueous ink from an inkjet recording head and applying it to the recording medium so as to overlap at least a portion of the area of ​​the recording medium to which the aqueous reaction liquid is applied, the inkjet recording method being characterized in that the reactant contains a cationic resin, the cationic resin contains a first cationic resin having a peak in a molecular weight range of 100,000 to 500,000 inclusive and a second cationic resin having a peak in a molecular weight range of 2,000 to less than 100,000 inclusive in terms of molecular weight distribution measured by gel permeation chromatography (GPC), and the content (mass%) of the second cationic resin is 0.01 to 8.0 times the content (mass%) of the first cationic resin in terms of mass ratio. Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method capable of suppressing image unevenness when an image is recorded by applying ink and a reaction liquid to a recording medium by ejection from an inkjet recording head, suppressing blurring of images when continuously recorded and printed, and further suppressing image unevenness at the start of writing when an image is recorded after a certain period of rest. Also, according to the present invention, it is possible to provide an inkjet recording device used in this inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 2] FIG. 2 is a perspective view showing an example of a liquid application device. [Diagram 3] FIG. 2 is a cross-sectional perspective view showing an example of a discharge element substrate. [Figure 4]FIG. 2 is a schematic diagram showing an example of a liquid supply system. [Diagram 5] FIG. 13 is a schematic diagram showing another example of the heating unit. [Figure 6] FIG. 11 is a schematic diagram showing another example of the fixing unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, the aqueous ink and reaction liquid for inkjet printing may be simply referred to as "ink" and "reaction liquid." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified. When "(meth)acrylic acid" and "(meth)acrylate" are written, they mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

[0013] In the present invention, the order of application of the reaction liquid and the ink is not particularly limited. However, it is preferable to apply the reaction liquid to the recording medium and then the ink, since this makes it easier to obtain the effects of the present invention. Hereinafter, an example will be described in which the reaction liquid is applied to the recording medium and then the ink is applied.

[0014] The present inventors have conducted research to suppress image unevenness, which is particularly likely to occur when a reaction liquid and ink are applied to a low-absorbency or non-absorbency recording medium using an inkjet recording device. As a result, it has been found that image unevenness occurs due to the flow of ink that has landed on the recording medium. In order to suppress the flow of ink, it is important to promote the aggregation and thickening of the ink. Therefore, the present inventors have conducted further research using a reaction liquid containing a cationic resin in order to promote the aggregation and thickening of the ink and suppress image unevenness.

[0015] As a result, it was found that although image unevenness could be suppressed by using the reaction liquid and ink containing the cationic resin, when a large number of images were continuously recorded, blurred images occurred. When the cause of the blurred images was analyzed, it was found that solidified matter was accumulated on the discharge port surface of the recording head, which is the liquid application device on the ink side, and this caused poor ink discharge and blurred images. Then, as a result of further analysis, it was found that when the reaction liquid and ink are discharged from the inkjet recording head, small droplets (so-called satellites) generated by the breakage of the main droplets are generated as droplets of the reaction liquid in addition to the main droplets. The inventors of the present invention speculated that the satellites did not land on the recording medium but floated, adhered to the discharge port surface on the ink side, and came into contact with the ink to generate the solidified matter. Therefore, in order to reduce the generation of satellites of the reaction liquid, it was necessary to make it difficult to break up the main droplets of the reaction liquid when they were discharged from the recording head, and a study was conducted. As a result, it was found that the generation of satellites can be reduced by using a cationic resin with a relatively high molecular weight. In other words, the present inventors speculate that the use of a cationic resin with a relatively high molecular weight enhances the spinnability of the droplets of the reaction liquid due to the formation of hydrogen bonds between the cationic resins, thereby suppressing the fragmentation of the droplets. Specifically, it was found that the use of a first cationic resin having a peak in the molecular weight range of 100,000 to 500,000 in the molecular weight distribution measured by GPC as the cationic resin reduces the generation of satellites in the reaction liquid and suppresses blurring of images.

[0016] However, when using a reaction liquid containing the first cationic resin with a high molecular weight, it was found that when the ejection operation of the reaction liquid by the recording head is stopped for a certain period of time and then ejected again, image unevenness occurs at the starting portion of the image. The inventors speculate that this is because the water in the reaction liquid inside the ejection port of the recording head evaporates during the certain period of pause, causing a significant increase in the viscosity of the reaction liquid inside the ejection port, making it impossible to eject the reaction liquid at the starting portion of the image.

[0017] As a result of intensive research into the above problem, it has been found that the unevenness of the image at the start of writing after a certain period of pause can be suppressed by using a second cationic resin with a relatively low molecular weight in addition to the first cationic resin with a high molecular weight. Specifically, it has been found that it is important to use a second cationic resin with a peak in the molecular weight range of 2000 to less than 100,000 in the molecular weight distribution measured by GPC in combination with the first cationic resin. That is, by using a first cationic resin with a high molecular weight in combination with a second cationic resin with a low molecular weight, the increase in viscosity during water evaporation can be suppressed compared to the case where the first cationic resin with a high molecular weight is used alone. Therefore, the ejection property of the reaction liquid after a certain period of pause is improved, and the unevenness of the image at the start of writing can be suppressed.

[0018] In addition, in order to solve the above problem, the content ratio of the first cationic resin and the second cationic resin in the reaction solution is also important. Specifically, the content (mass%) of the second cationic resin needs to be 0.01 times or more and 8.0 times or less in mass ratio to the content (mass%) of the first cationic resin. By making the content (mass%) of the second cationic resin 0.01 times or more in mass ratio to the content (mass%) of the first cationic resin, image unevenness at the start of writing of the image can be suppressed. In addition, by making the content (mass%) of the second cationic resin 8.0 times or less in mass ratio to the content (mass%) of the first cationic resin, the generation of satellites can be suppressed and blurring of the image can be suppressed.

[0019] Furthermore, if the reaction liquid contains a cationic resin having a peak in a region of molecular weight less than 100,000 instead of the first cationic resin, the occurrence of satellites cannot be sufficiently suppressed, and the level of image blur required by the present invention cannot be achieved. On the other hand, if the reaction liquid contains a cationic resin having a peak in a region of molecular weight more than 500,000 instead of the first cationic resin, the viscosity inside the discharge port after a certain period of inactivity increases too much, and the reaction liquid cannot be discharged normally when writing an image, resulting in image unevenness at the start of writing the image.

[0020] Furthermore, if the reaction liquid contains, instead of the second cationic resin, a cationic resin having a peak in a region of molecular weight less than 2000, the generation of satellites cannot be sufficiently suppressed, and the suppression of image blurring at the level required by the present invention cannot be achieved. Also, if the reaction liquid contains, instead of the second cationic resin, a cationic resin having a peak in a region of molecular weight of 100,000 or more, the viscosity inside the discharge port after a certain period of pause increases too much, preventing the reaction liquid from being normally discharged at the time of writing, and causing image unevenness at the writing start portion.

[0021] In addition, the image unevenness caused by using the above-mentioned ink and reaction liquid is a phenomenon that is particularly likely to occur when a low-absorbency or non-absorbency recording medium is used as the recording medium. In this specification, a low-absorbency recording medium is a recording medium that is not absorbent within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 4mL / m 2 More than 10mL / m 2 A non-absorbent recording medium is one that is absorbent within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 0mL / m 2 More than 4mL / m 2 That is, low absorbency and non-absorbency recording media refer to recording media that are less than 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2 The penetration speed of ink or reaction liquid is relatively fast (30 msec from the start of contact in the Bristow method). 1 / 2 Water absorption up to 10mL / m 2In the case of plain paper, which is an absorbent recording medium having a water absorption of 100% or more, the reaction liquid penetrates the recording medium immediately after it is applied to the recording medium. After that, the ink applied to the recording medium comes into contact with the reaction liquid, and the pigment and the aqueous medium also penetrate into the recording medium while coagulating. Therefore, the ink does not flow on the surface of the recording medium, so there is almost no movement of the pigment, and image unevenness is unlikely to occur. On the other hand, in the case of low-absorbency and non-absorbency recording media that hardly absorb ink or reaction liquid, the reaction liquid hardly penetrates, so the reaction liquid and ink are present on the surface of the low-absorbency and non-absorbency recording media. Therefore, the ink is likely to flow on the surface of the recording medium, and image unevenness is likely to occur. However, in the present invention, even when a low-absorbency and non-absorbency recording medium that is likely to cause image unevenness is used, the ink is sufficiently thickened by contact with the reaction liquid, so that the ink is unlikely to flow and image unevenness is unlikely to occur.

[0022] <Inkjet recording method, inkjet recording apparatus, and set of aqueous ink and aqueous reaction liquid> The inkjet recording method of the present invention (hereinafter, also simply referred to as "recording method") is an inkjet recording method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink. The recording method includes a reaction liquid applying step of ejecting the aqueous reaction liquid from an inkjet recording head and applying it to the recording medium. The recording method further includes an ink applying step of ejecting the aqueous ink from an inkjet recording head and applying it to the recording medium so as to overlap at least a part of the area of ​​the recording medium to which the aqueous reaction liquid is applied. The reactant includes a cationic resin. The cationic resin includes a first cationic resin having a first peak in a molecular weight range of 100,000 to 500,000 and a second cationic resin having a second peak in a molecular weight range of 2,000 to less than 100,000 in a molecular weight distribution measured by gel permeation chromatography (GPC) of the reaction liquid, and the content (mass%) of the second cationic resin is 0.01 to 8.0 times the content (mass%) of the first cationic resin in terms of mass ratio.

[0023] The inkjet recording apparatus (hereinafter also simply referred to as "recording apparatus") of the present invention is an inkjet recording apparatus used in an inkjet recording method for recording an image on a recording medium using an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink. This recording apparatus is a recording apparatus that is suitably used in the above-mentioned recording method. This recording apparatus has an inkjet type reaction liquid application means that ejects the aqueous reaction liquid and applies it to the recording medium. Furthermore, this recording apparatus has an inkjet type ink application means that ejects the aqueous ink and applies it to the recording medium so as to overlap at least a portion of the area of ​​the recording medium to which the aqueous reaction liquid is applied.

[0024] The set of aqueous ink and aqueous reaction liquid of the present invention (hereinafter, also simply referred to as "set") is a set used in an inkjet recording method in which an image is recorded on a recording medium using an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink. This set is a set that is suitably used in the above-mentioned recording method. The form of the set includes a set of multiple ink cartridges each containing multiple inks (reaction liquids) independently, and a state of an ink cartridge formed integrally by combining multiple ink containing sections each containing multiple inks (reaction liquids). The set of the present invention is not limited to the above form and may be in any form as long as it is configured so that the inks and reaction liquids can be used in combination.

[0025] The recording method and recording apparatus of the present invention will be described in detail below.

[0026] (Inkjet recording device) The inkjet recording apparatus will be described in detail below with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of the inkjet recording apparatus of the present invention. The inkjet recording apparatus of this embodiment is an inkjet recording apparatus that records an image on a recording medium using ink and a reaction liquid containing a reactant that reacts with the ink. The X direction, Y direction, and Z direction respectively indicate the width direction (total length direction), depth direction, and height direction of the inkjet recording apparatus. The recording medium is transported in the X direction.

[0027] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured to include a recording unit 1000, a heating unit 2000, a fixing unit 3000, a cooling unit 4000, an inverting unit 5000, and a paper discharge unit 6000. In the recording unit 1000, various liquids such as reaction liquid and ink are applied by a liquid application unit 1200 to a recording medium 1100 conveyed from a paper feed unit 1400 by a conveying member 1300. In the heating unit 2000, the liquid applied to the recording medium 1100 is heated by a heating unit 2100, and volatile components such as water in the liquid are evaporated and dried. In the fixing unit 3000, a fixing member 3100 is brought into contact with the area of ​​the recording medium 1100 to which the liquid has been applied, and heated to promote fixing of the image to the recording medium 1100. The recording medium 1100 is then cooled by a cooling member 4100 of the cooling unit 4000. When an image is to be recorded on the back side following the front side (recording surface), the recording medium 1100 is first inverted by an inversion device 5100 of an inversion section 5000. Next, an image is recorded on the back side in the same manner as the front side, and then the recording medium is transported by a transport member 6100 of a paper discharge section 6000 and stacked and stored in a recording medium storage section 6200.

[0028] Any recording medium may be used as the recording medium 1100. For example, recording media having ink absorbency (permeability) such as recording media without a coating layer, such as plain paper, uncoated paper, and synthetic paper, and recording media with a coating layer, such as printing paper, glossy paper, and art paper, may be used. In addition, recording media having no permeability, such as films or sheets made of resin materials such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), may be used. The basis weight (g / m2) of the recording medium 1100 may be determined by the following formula: 2) is 30g / m 2 More than 500g / m 2 It is preferable that the thickness is less than 50 g / m 2 More than 450g / m 2 It is even more preferable that:

[0029] [Recording Section] The recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a reaction liquid applying device 1201 which is a reaction liquid applying means and an ink applying device 1202 which is an ink applying means. The reaction liquid applying device 1201 is an inkjet type ejection head (recording head) and ejects a reaction liquid to apply it to the recording medium. The reaction liquid applying device 1201 may apply the reaction liquid either before or after the ink application as long as it can contact the ink on the recording medium 1100. However, in order to record high-quality images on various recording media having different liquid absorption characteristics, it is preferable to apply the reaction liquid before the ink application. The ink applying device 1202 is an inkjet type ejection head (recording head) and ejects ink to apply it to the recording medium. The ejection method of the ejection head as the liquid applying device 1200 can be exemplified by a method of ejecting liquid by generating film boiling in the liquid by an electrothermal converter to form bubbles, a method of ejecting liquid by an electromechanical converter, and the like.

[0030] The liquid deposition device 1200 is a line head extending in the Y direction, and has ejection ports arranged in a range that covers an image recording area of ​​the widest usable recording medium. The ejection head has an ejection port surface 1207 (FIG. 3) on which ejection ports are formed on its lower side (the recording medium 1100 side), and the ejection port surface faces the recording medium 1100 at a very small distance of about a few millimeters.

[0031] A plurality of ink applicators 1202 may be provided to apply ink of each color to the recording medium 1100. For example, when recording images of each color using yellow ink, magenta ink, cyan ink, and black ink, four ink applicators 1202 for ejecting the above four types of ink are arranged side by side in the X direction. Hereinafter, the ink and the reaction liquid may be collectively referred to as "liquid".

[0032] Fig. 2 is a perspective view showing an example of a liquid application device. The liquid application device 1200 shown in Fig. 2 is a line head, and a plurality of ejection element substrates 1203 each having an ejection port array are arranged in a straight line. The ejection element substrate 1203 has a plurality of ejection port arrays arranged thereon.

[0033] FIG. 3 is a cross-sectional perspective view showing an example of a discharge element substrate. The discharge element substrate 1203 shown in FIG. 3 includes a discharge port forming member 1206 having a discharge port 1204 opened therein, and a substrate 1205 having discharge elements (not shown) disposed thereon. The discharge port forming member 1206 and the substrate 1205 are laminated to form a first flow path 1208 and a second flow path 1209 through which liquid flows. The first flow path 1208 is a region from an inlet 1212 through which liquid flows in from an inflow path 1210 to a portion between the discharge port 1204 and the discharge element (FIG. 4, liquid chamber 1508). The second flow path 1209 is a region from a portion between the discharge port 1204 and the discharge element (FIG. 4, liquid chamber 1508) to an outlet 1213 through which liquid flows out to an outlet path 1211. For example, by creating a pressure difference between the inlet 1212 and the outlet 1213, such as the inlet 1212 having a high pressure and the outlet 1213 having a low pressure, liquid can be made to flow from the high pressure to the low pressure (in the direction of the arrow in FIG. 3). The liquid that has passed through the inlet 1210 and the inlet 1212 enters the first flow path 1208. Then, the liquid that has passed through the portion between the outlet 1204 and the ejection element (liquid chamber 1508 in FIG. 4) flows through the second flow path 1209 and the outlet 1213 to the outlet path 1211.

[0034] [Supply system] FIG. 4 is a schematic diagram showing an example of a supply system for liquid such as ink. The supply unit 1500 of the liquid deposition apparatus 1200 shown in FIG. 4 is configured to include a first circulation pump (high pressure side) 1501, a first circulation pump (low pressure side) 1502, a sub-tank 1503, and a second circulation pump 1505. The sub-tank 1503 connected to a main tank 1504, which is a liquid storage unit, has an air communication port (not shown) and can discharge air bubbles mixed in the liquid to the outside of the circulation system. The sub-tank 1503 is also connected to a refill pump 1506. The liquid is consumed in the liquid deposition apparatus 1200 by discharging (discharging) the liquid from the discharge port for image recording, suction recovery, etc. The refill pump 1506 transfers the liquid corresponding to the consumed amount from the main tank 1504 to the sub-tank 1503.

[0035] The first circulation pump (high pressure side) 1501 and the first circulation pump (low pressure side) 1502 cause the liquid in the liquid deposition device 1200, which is caused to flow out from a connection part (inlet part) 1507, to flow into a sub tank 1503. It is preferable to use a positive displacement pump having a quantitative liquid delivery capability as the first circulation pump (high pressure side) 1501, the first circulation pump (low pressure side) 1502, and the second circulation pump 1505. Examples of such a positive displacement pump include a tube pump, a gear pump, a diaphragm pump, and a syringe pump. When the ejection element substrate 1203 is driven, the first circulation pump (high pressure side) 1501 and the first circulation pump (low pressure side) 1502 can cause the liquid to flow from a common inlet channel 1514 toward a common outlet channel 1515.

[0036] The negative pressure control unit 1509 includes two pressure adjustment mechanisms with mutually different control pressures. The pressure adjustment mechanism (high pressure side) 1510 and the pressure adjustment mechanism (low pressure side) 1511 are connected to a common inflow channel 1514 and a common outflow channel 1515 in the ejection element substrate 1203 via a supply unit 1513 provided with a filter 1512 for removing foreign matter from the liquid. The ejection element substrate 1203 is provided with the common inflow channel 1514, the common outflow channel 1515, and the inflow channel 1210 and the outflow channel 1211 that communicate with the liquid chamber 1508, which is a portion between the ejection port 1204 and the ejection element (not shown). Since the inflow channel 1210 and the outflow channel 1211 communicate with the common inflow channel 1514 and the common outflow channel 1515, respectively, a flow (arrow in FIG. 4) occurs in which part of the liquid flows from the common inflow channel 1514 through the inside of the liquid chamber 1508 to the common outflow channel 1515. The arrows in Fig. 3 indicate the flow of liquid inside the liquid chamber 1508. That is, as shown in Fig. 3, the liquid in the first flow path 1208 flows into the second flow path 1209 via the gap between the ejection port 1204 and the ejection element.

[0037] 4, a pressure adjustment mechanism (high pressure side) 1510 is connected to the common inflow channel 1514, and a pressure adjustment mechanism (low pressure side) 1511 is connected to the common outflow channel 1515, so that a pressure difference occurs between the inflow channel 1210 and the outflow channel 1211. As a result, a pressure difference also occurs between an inlet 1212 (FIG. 3) communicating with the inflow channel 1210, and an outlet 1213 (FIG. 3) communicating with the outflow channel 1211. When liquid is caused to flow by the pressure difference between the inlet 1212 and the outlet 1213, it is preferable to control the flow velocity (mm / s) of the liquid to be 0.1 mm / s or more and 10.0 mm / s or less.

[0038] [Transport system] As shown in FIG. 1, the recording unit 1000 is configured to include a liquid applying device 1200 and a conveying member 1300 that conveys the recording medium 1100. The liquid applying device 1200 applies a reaction liquid and ink to a desired position of the recording medium 1100 conveyed by the conveying member 1300. Each liquid applying device 1200 receives an image signal of recording data and applies the necessary reaction liquid and ink to each position. FIG. 1 shows the conveying member 1300 in the form of a conveying belt, but a spur, a conveying drum, or the like may be used as long as it has the function of conveying the recording medium 1100. In order to improve the conveying accuracy, a material that can fix the recording medium 1100 can be used as the conveying member 1300. Specifically, a method of providing a hole in the conveying member 1300 and fixing the recording medium 1100 by sucking from the back side, a method of forming the conveying member 1300 from an appropriate material and fixing the recording medium 1100 by electrostatic adsorption, etc. can be mentioned.

[0039] [Heating section] As shown in Fig. 1, the heating section 2000 is configured to include a heating device 2100 and a transport member 2200. The recording medium 1100, to which the reaction liquid and ink have been applied and an image has been recorded, is heated by the heating device 2100 while being transported by the transport member 2200, thereby evaporating and drying the liquid components of the image. It is preferable to further include a drying step between the ink application step and the fixing step, in which the recording medium to which the ink has been applied is heated in a non-contact manner to dry the ink. By including such a drying step, deformation (cockling and curling) of the recording medium 1100 can be effectively suppressed.

[0040] The heating device 2100 may have any configuration as long as it can heat the recording medium 1100, and various conventionally known devices such as a hot air dryer or heater can be used. Among them, the use of a non-contact heater such as an electric heating wire or infrared heater is preferable from the standpoint of safety and energy efficiency. In addition, if a mechanism for blowing hot air with a built-in fan for spraying heated gas onto the recording medium 1100 is used, the drying efficiency can be easily improved.

[0041] Regarding the method of heating, the recording medium 1100 may be heated from the side (recording surface (front side)) to which the reaction liquid and the ink are applied, or from the back side, or from both sides. The conveying member 2200 may be provided with a heating function. FIG. 1 shows the conveying member 2200 using a conveying belt, but a spur, conveying drum, or the like may be used as long as it has the function of conveying the recording medium 1100. From the viewpoint of suppressing deformation of the recording medium 1100 due to heating, it is preferable to have a configuration in which the recording medium 1100 is conveyed while being in close contact with the conveying member 2200 by blowing air from the heating unit 2000, or to have a mechanism for fixing the recording medium to the conveying member 2200. Specifically, a method of providing a hole in the conveying member 2200 and fixing the recording medium 1100 by suction from the back side, a method of forming the conveying member 2200 from an appropriate material, and fixing the recording medium 1100 by electrostatic adsorption, etc. can be mentioned.

[0042] The heating temperature is preferably set so as to quickly evaporate the liquid components and not to over-dry the recording medium 1100 in terms of suppressing deformation of the recording medium. The temperature of the drying means can be set so that the recording medium reaches a desired temperature, taking into consideration the conveying speed and the environmental temperature. Specifically, the temperature of the drying means (such as hot air) is preferably set to 40°C or higher and 100°C or lower, and more preferably 60°C or higher and 80°C or lower. In addition, when the recording medium 1100 is heated by blowing heated gas, the wind speed is preferably set to 1 m / s or higher and 100 m / s or lower. The temperature of the wind such as the hot air can be measured using a K-type thermocouple thermometer. A specific measuring device can be, for example, the product name "AD-5605H" (manufactured by A&D).

[0043] Fig. 5 is a schematic diagram showing another example of the heating section. Here, the difference from the heating section shown in Fig. 1 and described above will be described. The heating section 2000 shown in Fig. 5 includes a first heating device 2101 and a second heating device 2102, and a first conveying member 2201 and a second conveying member 2202 arranged opposite the first heating device 2101 and the second heating device 2102, respectively.

[0044] The first conveying member 2201 does not have a mechanism for sucking and fixing the recording medium 1100. The recording medium 1100 is pressed against the first conveying member 2201 by hot air from the first heating device 2101 to convey the recording medium 1100. This allows the recording medium 1100 to be transferred with high precision from the conveying member 1300 (FIG. 1) to the first conveying member 2201, and from the first conveying member 2201 to the second conveying member 2202. Furthermore, it is possible to reduce conveyance deviations caused by slight differences in conveying speed between the conveying member 1300 (FIG. 1) and the first conveying member 2201. On the other hand, a conveying belt having holes that can pass gas is used as the second conveying member 2202, and the recording medium 1100 is conveyed while being fixed to the second conveying member 2202 by a suction mechanism (not shown).

[0045] An air knife 2300 is disposed between the transport member 1300 (FIG. 1) and the first transport member 2201, between the first transport member 2201 and the second transport member 2202, and between the second transport member 2202 and the transport member 3200 (FIG. 1). The air pressure of the air knife 2300 prevents the leading edge of the transported recording medium 1100 from floating up. This makes it possible to prevent the leading edge of the recording medium 1100 from colliding with the first heating device 2101, the second heating device 2102, and the fixing member 3100 (FIG. 1), and to suppress transport failures.

[0046] The first heating device 2101 and the second heating device 2102 can have the same configuration as the above-mentioned heating device 2100. The temperatures of the first heating device 2101 and the second heating device 2102 and the wind speed when blowing heated gas for heating may be the same or different. Furthermore, heating may be performed from the first conveying member 2201 and the second conveying member 2202 as necessary.

[0047] [Fixing section] As shown in FIG. 1, the fixing unit 3000 is a contact-type heating and pressurizing mechanism having a fixing member 3100 as a fixing belt such as an endless belt and a conveying member 3200. In the fixing unit 3000, the recording medium 1100 is conveyed by the conveying member 3200, and the fixing member 3100 is brought into contact with the recording medium 1100 under pressure, and the liquid such as the reaction liquid or ink applied to the recording medium 1100 is heated. In this way, an image can be fixed on the recording medium 1100. From the recording medium 1100 on which an image has been recorded, the liquid components of the reaction liquid or ink permeate the recording medium 1100 or evaporate by passing through the heating unit 2000, and then the image is fixed in the fixing unit 3000, completing the image. By heating and pressurizing the recording medium 1100 sandwiched between the fixing member 3100 and the conveying member 3200, the image of the recording medium 1100 and the fixing member 3100 come into close contact with each other, and the image is fixed on the recording medium 1100. When a liquid such as ink containing resin particles and coloring material is used, the resin particles are softened and form a film mainly by heating in the fixing unit 3000 , and the coloring material can be bound onto the recording medium 1100 .

[0048] The fixing member 3100 may be heated by providing a heat source such as a halogen heater inside a roller that drives the fixing member 3100 as a fixing belt. Alternatively, a heat source such as an infrared heater may be provided at a location separate from the fixing member 3100. These methods may be combined. If necessary, the conveying member 3200 may be heated. The temperature of the fixing member 3100 may be set so that the surface of the recording medium has a desired temperature, taking into account the conveying speed and the environmental temperature. Specifically, the temperature of the fixing member 3100 is preferably 50° C. or higher and 120° C. or lower, and more preferably 60° C. or higher and 110° C. or lower. The temperature of the contact-type heating and pressing mechanism (fixing member 3100) and the surface temperature of the recording medium immediately after passing through the contact-type heating and pressing mechanism can both be measured using a radiation thermometer. The radiation thermometer may be installed near the end (terminal end) of the contact-type heating and pressing mechanism. A specific example of the radiation thermometer is a product name "Radiation Thermometer IT-545S" (manufactured by Horiba, Ltd.).

[0049] When the ink contains resin particles, if the temperature of the fixing member 3100 is set to a temperature equal to or higher than the glass transition temperature of the resin particles in the ink, the resin particles soften and are more likely to form a film, improving the scratch resistance of the image. When the ink contains wax particles, it is preferable to set the temperature of the fixing member 3100 lower than the melting point of the wax that constitutes the wax particles. This makes it easier for the wax, which is prevented from melting, to remain on the surface of the image, improving the scratch resistance of the image.

[0050] The nip pressure of the fixing member 3100 and the conveying member 3200, i.e., the pressure applied to the recording medium when it passes through the contact-type heating and pressing mechanism, is preferably 10 Pa to 1,000 Pa, more preferably 10 Pa to 500 Pa. Also, 10 Pa to 400 Pa is particularly preferable.

[0051] The time required for the recording medium to pass through the contact-type heating and pressing mechanism (nip time) is preferably from 0.25 seconds to 5.0 seconds, more preferably from 0.5 seconds to 4.0 seconds, and particularly preferably from 1.0 seconds to 3.0 seconds.

[0052] FIG. 6 is a schematic diagram showing another example of the fixing unit. Here, the difference from the fixing unit shown in FIG. 1 and described above will be described. The fixing unit 3000 shown in FIG. 6 is a contact type heating and pressurizing mechanism including a plurality of fixing rollers 3101 and a plurality of conveying members 3201 arranged opposite to these fixing rollers 3101. An image is fixed on the recording medium 1100 to which a liquid such as ink has been applied by passing between the fixing rollers 3101 and the conveying members 3201. The degree of image fixing on the recording medium can be adjusted by controlling the number of fixing rollers 3101 and the conveying members 3201, the nipping time of the recording medium by these, the temperature, the pressure, and the like.

[0053] [Cooling section] The cooling section 4000 is configured to include a cooling member 4100 and a conveying member 4200 (FIG. 1). The cooling section 4000 cools the recording medium 1100, which has been heated to a high temperature after passing through the heating section 2000 and the fixing section 3000. The cooling member 4100 may have any configuration as long as it can cool the recording medium 1100, and methods such as air cooling and water cooling can be used. Among them, blowing unheated gas is preferable in terms of safety and energy efficiency. In addition, if a fan is built in to inject gas onto the recording medium 1100 and a mechanism for blowing air is used, it is easy to improve cooling efficiency. The temperature of the cooling means can be set so that the image on the recording medium has a desired temperature, taking into account the conveying speed and the environmental temperature. Specifically, the temperature of the cooling means (such as air blowing) is preferably 20° C. or higher and 60° C. or lower, and more preferably 25° C. or higher and 50° C. or lower. When cooling by blowing gas, the wind speed is preferably 1 m / s or higher and 100 m / s or lower. By setting such conditions, it is possible to suppress deformation of the recording medium 1100 loaded in the paper discharge unit 6000 described later and image sticking (blocking).

[0054] [Inverted part] When performing double-sided recording, the recording medium 1100 is inverted using the inversion unit 5000 (FIG. 1). The recording medium 1100 with an image recorded on its recording surface (front side) passes through the cooling unit 4000, is branched and transported, and is inverted by the inversion device 5100. The inverted recording medium 1100 is transported to the paper feeder 1400 of the recording unit 1000 with liquid applied to its back side (the side opposite to the recording surface (front side)).

[0055] [Paper output section] After the image is recorded, the recording medium 1100 is stored in a paper discharge section 6000 (FIG. 1). After single-sided or double-sided recording is performed, the recording medium 1100 passes through the cooling section 4000, is transported by a transport member 6100, and is finally stored in a stacked state in a recording medium storage section 6200. Two or more recording medium storage sections 6200 may be provided to store different recorded materials, etc.

[0056] (Reaction solution) The recording method of the present invention has a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink to a recording medium. In particular, it is preferable to perform the reaction liquid application step before the ink application step. Hereinafter, each component used in the reaction liquid will be described in detail.

[0057] [Reactants] The reaction liquid reacts with the ink when it comes into contact with the ink, coagulating the components in the ink (components having anionic groups such as resins, surfactants, and self-dispersing pigments), and contains a reaction agent, which includes a cationic resin.

[0058] [Cationic Resin] As described above, the cationic resin includes a first cationic resin having a peak in a molecular weight region of 100,000 or more and 500,000 or less in a molecular weight distribution measured by GPC, and a second cationic resin having a peak in a molecular weight region of 2,000 or more and less than 100,000.

[0059] Furthermore, it is more preferable that the second cationic resin has a peak in the molecular weight range of 10,000 or more and less than 100,000 in the molecular weight distribution measured by GPC. When the peak position by GPC is 10,000 or more, the occurrence of satellites can be further suppressed, and image blurring can be further suppressed. On the other hand, when the peak position by GPC is less than 100,000, the viscosity in the discharge port after a certain period of pause does not increase too much, and the discharge of the reaction liquid at the time of writing can be further improved.

[0060] The molecular weight distribution of the cationic resin by GPC may be measured by directly measuring the cationic resin before preparing the reaction solution, or may be measured from the prepared reaction solution. When measuring the molecular weight distribution of the cationic resin by GPC from the prepared reaction solution, the following procedure is followed. First, the reaction solution containing the cationic resin is used as a sample, and the molecular weight distribution is measured using GPC in the same manner as when the cationic resin is directly measured. In the obtained molecular weight distribution, substances contained in each molecular weight region are separated to separate substances with different molecular weights. In addition, the mass ratio of the substances with each molecular weight is obtained from the area (peak area) of each molecular weight region in the obtained molecular weight distribution. The structure of the separated substance is identified using a nuclear magnetic resonance device (NMR device). In this way, the structure and content of the cationic resin having each molecular weight distribution in the reaction solution can be confirmed.

[0061] It is important that the content (mass%) of the second cationic resin is 0.01 to 8.0 times the content (mass%) of the first cationic resin in terms of the mass ratio. In order to further improve the suppression of image unevenness and blurring in the writing section, it is preferable that the content (mass%) of the second cationic resin is 0.01 to 0.30 times the content (mass%) of the first cationic resin in terms of the mass ratio.

[0062] Examples of the cationic resin include resins having a structure of primary to tertiary amines and resins having a structure of quaternary ammonium salts. Specific examples include resins having a structure of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensate. In order to increase the solubility in the reaction solution, the cationic resin may be used in combination with an acidic compound or the cationic resin may be subjected to a quaternary treatment. When the cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 0.1 mass% or more and 10.0 mass% or less based on the total mass of the reaction solution.

[0063] The counter anion of the cationic group of the cationic resin is preferably a chloride ion.

[0064] This is believed to be because, compared with ethyl sulfate ions, which are general-purpose counter anions of cationic groups, chloride ions have a smaller ion size and are less likely to interfere with the interaction between the cationic group and the anion components in the ink. As a result, color development can be further improved. In addition, the reaction liquid may contain ethyl sulfate ions and the like in addition to chloride ions derived from counter anions.

[0065] Both the first cationic resin and the second cationic resin preferably have a quaternary ammonium salt structure. When the cationic resin has a quaternary ammonium salt structure, the cationic resin has a quaternary ammonium ion as a cationic group, and can stably retain cationicity when in contact with ink, which makes it easier to interact with an anionic component in the ink.

[0066] It is preferable that the repeating structural units of the first cationic resin and the second cationic resin are the same (i.e., have only the same repeating structural units). If the repeating structural units are the same, association due to the formation of hydrogen bonds between the cationic resins is facilitated, and the spinning property of the droplets of the reaction liquid is improved, the division of the droplets is suppressed, and blurring of the image can be reduced.

[0067] Moreover, it is preferable that both the first cationic resin and the second cationic resin are polymers having a repeating structural unit represented by the following formula (1).

[0068] [ka]

[0069] (In the general formula (1), R1 and R2 each independently represent an alkyl group; X - represents a counter anion with the quaternary ammonium cation.) Moreover, the repeating structural unit is more preferably a diallyldimethylammonium chloride structure in which R1 and R2 in the above formula (1) are both methyl groups. The diallyldimethylammonium chloride structure has a quaternary ammonium salt in the resin side chain, so it is less susceptible to steric hindrance than when a quaternary ammonium salt is present in the main chain. This makes it easier to interact with the anion components in the ink, and improves the effect of suppressing image unevenness.

[0070] A polyvalent metal salt or an organic acid may be used as a reactant together with the cationic resin. Among them, it is preferable to use a polyvalent metal salt together with the cationic resin.

[0071] By using the cationic resin and the polyvalent metal salt in combination, when the reaction liquid and the ink contact on the recording medium, the polyvalent metal ions dissociated from the polyvalent metal salt have a faster diffusion speed than the cationic resin, and react with the anion components in the ink quickly, promoting aggregation. Furthermore, the cationic resin reacts so as to surround the aggregates, resulting in even larger aggregates. Therefore, it is possible to suppress the penetration of the coloring material into the recording medium, and image unevenness is suppressed.

[0072] The polyvalent metal salt is a compound composed of a divalent or higher metal ion (polyvalent metal ion) and an anion. The polyvalent metal salt dissociates in the reaction solution to become a polyvalent metal ion, and causes anionic components such as pigments dispersed by anionic groups in the ink to aggregate. The polyvalent metal salt may be a hydrate. Examples of the polyvalent metal ion that constitutes the polyvalent metal salt include Ca 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Sr 2+ , B.A. 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+ Examples of the anion include trivalent metal ions such as Cl. - , Br - , I - , ClO - , ClO2 - , ClO3 - , ClO4 - , NO2 - , NO3 - , SO4 2- , CO3 2- , HCO3 - , PO4 3- , HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO - )2, COOH(COO - ), CH3COO - , CH3CH(OH)COO -, C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - In the case where a polyvalent metal ion is used as a reactant, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.0 mass% or more and 20.0 mass% or less based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of the polyvalent metal salt" in the reaction solution means the "content (mass%) of the anhydride of the polyvalent metal salt" excluding water as the hydrate.

[0073] The reaction liquid containing an organic acid has a buffering ability in the acidic range (less than pH 7.0, preferably pH 2.0 to 5.0), and thus efficiently converts the anionic groups of the components present in the ink into an acid form and causes them to aggregate. Examples of the organic acid include monocarboxylic acids and salts thereof, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furan carboxylic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and salts and hydrogen salts thereof, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and salts and hydrogen salts thereof, such as citric acid and trimellitic acid; and tetracarboxylic acids and salts and hydrogen salts thereof, such as pyromellitic acid. When an organic acid is used as the reactant, the content (mass %) of the organic acid in the reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0074] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. The aqueous medium used in the reaction liquid can be the same as the aqueous medium that can be contained in the ink described later. The aqueous medium used in the reaction liquid can contain the water-soluble organic solvent that can be contained in the ink described later. The content (mass%) of the water-soluble organic solvent in the reaction liquid is preferably 1.0 mass% or more and 45.0 mass% or less based on the total mass of the reaction liquid. The water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound described later. The content (mass%) of the water-soluble hydrocarbon compound in the reaction liquid is preferably 1.0 mass% or more and 20.0 mass% or less based on the total mass of the reaction liquid. In addition, the content (mass%) of water in the reaction liquid is preferably 50.0 mass% or more and 95.0 mass% or less based on the total mass of the reaction liquid.

[0075] [Other ingredients] The reaction liquid may contain various other components as necessary, such as the other components that can be contained in the ink, which will be described later.

[0076] [Physical properties of reaction solution] The reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the static surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the dynamic surface tension of the reaction liquid at a life time of 10 ms is preferably 40 mN / m or less. There is no particular restriction on the lower limit of this dynamic surface tension, but it is preferable that it is, for example, 25 mN / m or more.

[0077] The dynamic surface tension of a reaction liquid at a lifetime of 10 ms can be measured by the maximum bubble pressure method. The maximum bubble pressure method is a method in which the maximum pressure required to release a bubble generated at the tip of a probe (capillary tube) immersed in the liquid to be measured is measured, and the surface tension of the liquid is calculated from this maximum pressure. In the maximum bubble pressure method, the lifetime is the time from when the surface of a new bubble is generated at the tip of the probe to when the maximum bubble pressure (the point at which the radius of curvature of the bubble is equal to the radius of the tip of the probe) is reached. The dynamic surface tension of the ink in this specification is a value measured at 25°C.

[0078] The viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less, and more preferably 1.5 mPa·s or more and 5.0 mPa·s or less. If it is 1.5 mPa·s or more, satellites can be further suppressed and image blurring can be improved. If it is 5.0 mPa·s or less, the viscosity inside the ejection port after a certain period of inactivity does not increase too much, the reaction liquid is easily ejected when writing begins, and image unevenness is less likely to occur.

[0079] The pH of the reaction solution at 25° C. is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.5 or less.

[0080] (ink) The ink used in the recording method of the present invention is a water-based ink for ink-jet recording. Each component of the ink will be described in detail below.

[0081] [Colorant] The ink preferably contains a coloring material. Pigments or dyes can be used as the coloring material. The content (mass %) of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0082] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, etc. The pigments may be used alone or in combination of two or more.

[0083] As the dispersion method of the pigment, a resin-dispersed pigment using a resin as a dispersant, a self-dispersed pigment in which a hydrophilic group is bonded to the pigment particle surface, etc. can be used. In addition, a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the pigment particle surface, and a microcapsule pigment in which the surface of the pigment particle is coated with a resin, etc. can be used. It is also possible to use a combination of pigments with different dispersion methods among these. In particular, it is preferable to use a resin-dispersed pigment in which a resin as a dispersant is physically adsorbed on the pigment particle surface, rather than a resin-bonded pigment or a microcapsule pigment.

[0084] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin having an anionic group can be used, and a resin as described below, especially a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0085] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0086] The dye preferably has an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes. The dye may be used alone or in combination of two or more. The coloring material is preferably a pigment, and more preferably a resin-dispersed pigment or a self-dispersed pigment.

[0087] [resin] The ink can contain a resin. By using an ink containing a resin, an image with improved scratch resistance can be recorded. The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary.

[0088] Also, (ii) pigments can be added to the ink to improve various properties of the recorded image.

[0089] The content (mass %) of the resin in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 0.5% by mass or more and 15.0% by mass or less, based on the total mass of the ink. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin may be used alone or in combination of two or more kinds.

[0090] [Resin Composition] Examples of the resin include acrylic resins, urethane resins, olefin resins, etc. Among them, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferred.

[0091] The acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. Among them, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of a monomer having an aromatic ring and a (meth)acrylic acid ester monomer is preferred. In particular, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one of styrene and α-methylstyrene is preferred. These resins are easily interacted with pigments, and therefore can be suitably used as a resin dispersant for dispersing pigments.

[0092] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0093] The urethane resin can be obtained by reacting, for example, polyisocyanate with a polyol. In addition, a chain extender may be further reacted with the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0094] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution.

[0095] When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, and measurement time: 180 seconds. In addition, a particle size analyzer using dynamic light scattering (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as the particle size distribution measuring device.

[0096] Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0097] The acid value of the water-soluble resin is preferably 100 mgKOH / g or more and 250 mgKOH / g or less, and the weight average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less.

[0098] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, and more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D 50 ) is preferably 50 nm or more and 500 nm or less. The volume-based cumulative 50% particle diameter of the resin particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in a particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above. The glass transition temperature of the resin particles is preferably 40° C. or more and 120° C. or less, and more preferably 50° C. or more and 100° C. or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not need to contain a coloring material.

[0099] [Wax particles] The ink may contain particles formed from wax (wax particles).

[0100] By using an ink containing wax particles, an image with improved abrasion resistance can be recorded. In this specification, the wax may be a composition containing components other than wax, or the wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or a resin. The wax may be used alone or in combination of two or more kinds. The content (mass %) of the wax particles in the ink is preferably 0.1 mass % or more and 10.0 mass % or less, and more preferably 1.0 mass % or more and 5.0 mass % or less, based on the total mass of the ink.

[0101] In the narrow sense, wax is an ester of a water-insoluble higher monohydric or dihydric alcohol and a fatty acid, and includes animal waxes and vegetable waxes, but does not include oils and fats. In the broad sense, wax includes high melting point fats, mineral waxes, petroleum waxes, and blends and modified products of various waxes. In the present invention, any wax in the broad sense can be used without particular restrictions. Wax in the broad sense can be classified into natural waxes, synthetic waxes, blends thereof (blended waxes), and modified products thereof (modified waxes).

[0102] Examples of natural waxes include animal waxes such as beeswax, spermaceti, and wool wax (lanolin); vegetable waxes such as wood wax, carnauba wax, sugarcane wax, palm wax, candelilla wax, and rice wax; mineral waxes such as montan wax; and petroleum waxes such as paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax and polypropylene wax). The blended wax is a mixture of the above-mentioned various waxes. The modified wax is a wax obtained by subjecting the above-mentioned various waxes to a modification treatment such as oxidation, hydrogenation, alcohol modification, acrylic modification, and urethane modification. One of the above waxes may be used alone, or two or more may be used in combination. The wax is preferably at least one selected from the group consisting of microcrystalline wax, Fischer-Tropsch wax, polyolefin wax, paraffin wax, and modified or blended products thereof. Among them, a blend of multiple types of wax is more preferable, and a blend of a petroleum wax and a synthetic wax is particularly preferable.

[0103] The wax is preferably solid at room temperature (25°C). The melting point (°C) of the wax is preferably 40°C or higher and 120°C or lower, and more preferably 50°C or higher and 100°C or lower. The melting point of the wax can be measured in accordance with the test method described in 5.3.1 (melting point test method) of JIS K2235:1991 (petroleum wax). In the case of microcrystalline wax, petrolatum, and a mixture of multiple types of wax, the test method described in 5.3.2 can be used to measure more accurately. The melting point of the wax is easily affected by characteristics such as molecular weight (the higher the molecular weight, the higher the melting point), molecular structure (the higher the melting point if the chain is straight, and the lower the melting point if there is branching), crystallinity (the higher the crystallinity, the higher the melting point), and density (the higher the crystallinity, the higher the melting point). Therefore, by controlling these characteristics, it is possible to obtain a wax having a desired melting point. The melting point of the wax in the ink can be measured in accordance with the above test method, for example, after the ink is subjected to ultracentrifugation, the wax separated is washed and dried.

[0104] [Aqueous medium] The ink used in the recording method of the present invention is an aqueous ink containing at least water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, it is preferable to use deionized water or ion-exchanged water.

[0105] The content (mass%) of water in the aqueous ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. The content (mass%) of water-soluble organic solvent in the aqueous ink is preferably 2.0% by mass or more and 40.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used. The water-soluble organic solvent may be used alone or in combination of two or more.

[0106] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent contained in the ink preferably contains a specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain having three or more carbon atoms substituted with two or more hydrophilic groups selected from the group consisting of hydroxyl groups, amino groups, and anionic groups. However, the hydrocarbon chain may be interrupted by a sulfonyl group or an ether group. When the hydrocarbon chain has three or four carbon atoms, the hydrophilic group contains an anionic group, or the hydrocarbon chain is interrupted by a sulfonyl group.

[0107] In the present invention, a hydrocarbon compound that is dissolved in water at 25°C at the content of the compound in the ink is considered to be "water-soluble". In other words, the solubility in water at 25°C is greater than the content in the ink. The fact that the hydrocarbon chain is interrupted by a sulfonyl group or an ether group means that a sulfonyl group (-S(=O)2-) or an ether group (-O-) is present in the middle of the hydrocarbon chain. Water-soluble hydrocarbon compounds have hydrogen-bonding groups such as hydroxyl groups, amino groups, anionic groups, sulfonyl groups, and ether groups. Therefore, by using an ink containing this hydrocarbon compound, cockling and curling of a recording medium on which an image is recorded can be suppressed. General hydrocarbon compounds having a hydrocarbon chain with a relatively small number of carbon atoms (3 or 4) tend to have a small molecular weight and a low vapor pressure. However, since the above water-soluble hydrocarbon compounds have anionic groups of hydrogen bonds or the hydrocarbon chain is interrupted by a sulfonyl group, they are difficult to evaporate due to inter- or intra-molecular interactions, and remain between fibers to suppress cockling and curling. The content (mass %) of the water-soluble hydrocarbon compound in the ink is preferably 1.0 mass % or more and 20.0 mass % or less based on the total mass of the ink.

[0108] The number of carbon atoms in the hydrocarbon chain constituting the water-soluble hydrocarbon compound is preferably from 3 to 50, and more preferably from 3 to 10. Examples of the anionic group include a sulfonic acid group and a carboxylic acid group. Specific examples of water-soluble hydrocarbon compounds include alkanediols such as 1,5-pentanediol and 1,6-hexanediol; amino acids such as alanine, β-alanine, trimethylglycine, amidosulfuric acid (also known as sulfamic acid), aminomethanesulfonic acid, taurine (also known as 2-aminoethanesulfonic acid), carbamic acid, glycine, aspartic acid, glutamic acid, sulfanilic acid, or salts of the above-mentioned acids, phenylalanine, leucine, isoleucine, threonine, tryptophan, valine, methionine, lysine, and arginine; sulfonyl compounds such as bis(2-hydroxyethyl)sulfone; alkylene glycols such as triethylene glycol, tetraethylene glycol, tripropylene glycol, and polyethylene glycols having a number average molecular weight of about 200 to 1,000; and sugars such as sorbitol, D-sorbitol, xylitol, trehalose, fructose, and D(+)-xylose. The water-soluble hydrocarbon compounds may be used alone or in combination of two or more.

[0109] [Other ingredients] The ink may contain various other components as necessary. Examples of other components include various additives such as defoamers, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the ink does not contain a reactant to be contained in the reaction liquid.

[0110] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less. EXAMPLES

[0111] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the present invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0112] The trade names of the cationic resins used in the examples and comparative examples, and the molecular weights at the peak positions in the molecular weight distributions of the cationic resins measured by gel permeation chromatography (GPC) are shown below. The measurement conditions for GPC are also shown below.

[0113] <Product name of cationic resin and molecular weight at peak position in molecular weight distribution measured by GPC> PAS-H-5L: Diallyldimethylammonium chloride polymer (manufactured by Nittobo Medical) (quaternary ammonium salt, concentration 28%, molecular weight at GPC peak position 30,000) PAS-J-81L: Diallyldimethylammonium chloride-acrylamide copolymer (manufactured by Nittobo Medical) (quaternary ammonium salt, concentration 25%, molecular weight at GPC peak position 10,000) Catiomaster PE-30: (Yokkaichi Chemical) (dimethylamine-ethylenediamine-epichlorohydrin resin, concentration 50%, molecular weight at GPC peak position 9,000) PAA-HCL-3L: Allylamine hydrochloride polymer (manufactured by Nittobo Medical) (primary amine, concentration 50%, molecular weight at GPC peak position 15,000) PAA-HCL-10L: Allylamine hydrochloride polymer (manufactured by Nittobo Medical) (primary amine, concentration 28%, molecular weight at GPC peak position 100,000) EPA-SK01: Polyamide polyamine-epichlorohydrin condensation resin (manufactured by Yokkaichi Chemical Co., Ltd.) (tertiary amine, concentration 12.5%, molecular weight at the GPC peak position of 200,000 or more) (Gel permeation chromatography (GPC) measurement conditions) Measurement equipment: Molecular weight measurement equipment (product name "Waters ALLIANCE e2695", manufactured by Waters) Columns: Asahipak "GF-310", Asahipak "GF-510" (all product names, manufactured by Showa Denko) Eluent: A mixture of 0.5mmol / L acetic acid solution and 0.1mmol / L sodium nitrate solution ·Flow rate: 1.0mL / min Oven temperature: 40℃ Detector: Refractive index (RI) detector (product name "Wyatt Optilab rex Refractive Index Detector", manufactured by Wyatt Technology) The molecular weight was calculated using a molecular weight calibration curve prepared using a molecular weight standard (product name "EasiCal Type PS-2 polystyrene", manufactured by Agilent Technology).

[0114] In addition, even when the cationic resin was separated from the prepared reaction solution, the molecular weight at the peak position in the molecular weight distribution by GPC was obtained, which was the same as that of the cationic resin before the preparation of the reaction solution.

[0115] <Preparation of cationic resin> (Aqueous solution of cationic resin A) Into a four-neck flask equipped with a thermometer, a stirrer and a reflux condenser, 161.67 parts of a 60% by mass aqueous solution of diallyldimethylammonium chloride (trade name: DADMAC, manufactured by Tokyo Chemical Industry Co., Ltd.), 1.46 parts of sodium hypophosphite as a "chain transfer agent", and 32.3 parts of pure water were added. Then, this was heated to 60°C, and 0.39 parts of ammonium persulfate as a "polymerization initiator" was added. Further, while maintaining the temperature at 60°C, the mixture was heated for 10 hours to carry out a reaction, and a cationic resin A was obtained. Then, pure water was added to obtain an aqueous solution of cationic resin A with a concentration of 20%. The molecular weight at the peak position in the molecular weight distribution of this cationic resin A measured by gel permeation chromatography (GPC) was 2,000.

[0116] (Aqueous solutions of cationic resins B to J) The water solubility of cationic resins B to J was obtained in the same manner as in the preparation of the aqueous solution of cationic resin A, except that the amounts of DADMAC, sodium hypophosphite, ammonium persulfate, and water added were as shown in Table 1. The GPC peak positions of the obtained cationic resins B to J are shown in Table 1.

[0117] [Table 1]

[0118] (Aqueous solution of cationic resin K) 286g of monoallylamine was added dropwise to 550g of 35% hydrochloric acid while stirring at 5-10℃ under ice cooling. After the dropwise addition, water and hydrogen chloride were removed at 60℃ under reduced pressure using a rotary evaporator to obtain white crystals. The crystals were dried at 80℃ under reduced pressure to obtain 485g of monoallylamine hydrochloride. This monoallylamine hydrochloride was adjusted to a 70% aqueous solution, and 2,2'-azobis(2-amidinopropane) dihydrochloride, a radical initiator, was dissolved in 50g of this aqueous solution in an amount of 1 mol% relative to the monoallylamine hydrochloride, and 25g of 35% hydrochloric acid was added. Then, the mixture was left to stand for 40 hours at 60℃ to polymerize. After the polymerization was completed, the system was poured into a mixture of 1900g of acetone / 100g of methanol, and the resulting precipitate was filtered to obtain polyallylamine hydrochloride. This polyallylamine hydrochloride was dissolved in pure water to prepare a 40% aqueous solution, and hydrochloric acid was removed using ion exchange resin IRA900 (trade name, manufactured by Organo) that had been previously ion-exchanged with sodium hydroxide to obtain polyallylamine cationic resin K. Pure water was then added to obtain a 40% aqueous solution of cationic resin K. The molecular weight at the peak position in the molecular weight distribution of this cationic resin K measured by gel permeation chromatography (GPC) was 2,000.

[0119] (Cationic resin L, M) As shown in Table 2, the cationic resin was prepared in the same manner as cationic resin K, except that the amount of 2,2'-azobis(2-amidinopropane) dihydrochloride added was changed.

[0120] [Table 2]

[0121] <Preparation of reaction solution> The components shown in Tables 3 to 5 were mixed and thoroughly stirred, and then pressure filtered using a cellulose acetate filter (manufactured by Advantec Toyo) with a pore size of 3.0 μm to prepare each reaction liquid.

[0122] The viscosity of the ink and reaction liquid was measured using an E-type viscometer (product name "RE-85L", manufactured by TOKI) at a temperature of 25° C. and at 50 rpm.

[0123] Dynamic surface tension was measured at a life time of 10 ms using a dynamic surface tension measuring device (trade name "Bubble Pressure Tensiometer BP2" manufactured by KRUSS) using the maximum bubble pressure method. "TSF4446" is the trade name of a silicone oil manufactured by Momentive Performance Materials Japan, "Acetylenol E100" is the trade name of a surfactant manufactured by Kawaken Fine Chemicals, and "Proxel GXL(S)" is the trade name of a preservative manufactured by Lonza.

[0124] [Table 3]

[0125] [Table 4]

[0126] [Table 5]

[0127] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. A mixture was obtained by mixing 10.0 parts of pigment (CI Pigment Blue 15:3), 15.0 parts of the aqueous solution of resin 1, and 75.0 parts of pure water.

[0128] The obtained mixture and 200 parts of zirconia beads with a diameter of 0.3 mm were placed in a batch-type vertical sand mill (manufactured by Imex) and dispersed for 5 hours while cooling with water. After removing coarse particles by centrifugation, the mixture was filtered under pressure with a cellulose acetate filter with a pore size of 3.0 μm (manufactured by Advantec Toyo) to prepare pigment dispersion 1 with a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0129] (Pigment dispersion 2) Pigment dispersion 2 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 122. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0130] (Pigment dispersion 3) Pigment dispersion 3 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 74. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0131] (Pigment Dispersion 4) Pigment dispersion 4 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to carbon black. The pigment dispersion 4 had a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0132] (Pigment Dispersion 5) 1.6 g of 4-amino-1,2-benzenedicarboxylic acid was added to a solution of 5 g of concentrated hydrochloric acid in 5.5 g of water while cooling it to 5°C. Next, the container containing this solution was placed in an ice bath to keep the solution at 10°C or less, and a solution of 0.9 g of sodium nitrite dissolved in 9.0 g of water at 5°C was added to this. After stirring this solution for another 15 minutes, 6 g of CI Pigment Blue 15:3 was added under stirring. After stirring for another 15 minutes, the resulting slurry was filtered with filter paper (product name: Standard Filter Paper No. 2; Advantec Toyo Co., Ltd.), and the particles were thoroughly washed with water. This was dried in an oven at 110°C to prepare a self-dispersed pigment. Furthermore, water was added to the obtained self-dispersed pigment to disperse it so that the pigment content was 10.0%, and a dispersion was prepared. By the above method, a pigment dispersion in which a self-dispersed pigment with -C6H3-(COONa)2 groups introduced on the pigment particle surface was dispersed in water was obtained. Thereafter, the sodium ions in the pigment dispersion were replaced with potassium ions using an ion exchange method, thereby obtaining Pigment Dispersion 5 having a pigment content of 10.0 mass %, in which a self-dispersing pigment having benzenedicarboxylic acid groups bonded to the surface of the pigment and having a potassium counter ion was dispersed.

[0133] <Production of resin particles> (Resin particles 1) A solution was prepared by mixing 0.2 parts of potassium persulfate and 74.0 parts of ion-exchanged water in a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube. An emulsion was also prepared by mixing 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "Aqualon KH-05", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). The emulsion was added dropwise to the solution over 1 hour under a nitrogen atmosphere, polymerized while stirring at 80°C, and then stirred for another 2 hours. After cooling to room temperature (25°C), ion-exchanged water and an aqueous potassium hydroxide solution were added to obtain an aqueous dispersion of resin particles 1 with a resin particle content of 25.0%.

[0134] <Ink Preparation> Each component (unit: %) shown in Table 6 was mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec Toyo) with a pore size of 3.0 μm to prepare each ink. "Acetylenol E100" is the product name of a surfactant manufactured by Kawaken Fine Chemicals.

[0135] [Table 6]

[0136] <Evaluation> Image unevenness and image unevenness at the start of writing after ejection is stopped are evaluated by filling 1000 reaction liquid applicators 1201 and ink applicators 1202 with ink using an inkjet recording apparatus 100 having the configuration shown in Fig. 1. In the inkjet recording apparatus 100, an image recorded under the condition that one ink droplet of 4.0 ng is applied to a unit area of ​​1 / 1200 inch x 1 / 1200 inch is defined as having a recording duty of 100%.

[0137] Further, the image fading caused by the adhesion of the ink head ejection ports was evaluated as follows using a PIXUS Pro10S.

[0138] In the present invention, in the evaluation criteria for each of the following items, "AAA", "AA", "A" and "B" were defined as acceptable levels, and "C" was defined as an unacceptable level. The evaluation results are shown on the right side of Table 7.

[0139] (Image unevenness of solid images) Using the combination of reaction liquid and ink shown in Table 7, a 15 cm x 15 cm solid image was recorded with a reaction liquid recording duty of 30% and an ink recording duty of 100%. The obtained image was left for 24 hours under conditions of a temperature of 23°C and a humidity of 50%, and then scanned using a scanner (manufactured by EPSON, product name: OFFIRIOES-10000G) under the conditions of mode: professional, resolution: 300 dpi, and color: 24 bit. Art paper (manufactured by Lintec, product name: Art PW8k, 30 msec from the start of contact in the Bristow method) was used as the recording medium.1 / 2 Water absorption up to: 9.5mL / m 2 ) was used.

[0140] Using Photoshop, a reference image sample (a recording that had no image unevenness) was prepared, a 50px x 100px area was cut out, converted to grayscale, and pasted into a new clipboard.

[0141] By performing two-level gradation for color correction, the threshold value (T) of the boundary for two-level gradation is lowered by 1, and the point where it touches the base of the peak is set as the threshold value.

[0142] The evaluation image sample was cut to a range of 50 x 100px, converted to grayscale, pasted into a new clipboard, and color-corrected to two gradations.

[0143] The threshold value (T) calculated above was used as the threshold value for the boundary of two-tone gradation, and the ratio (the number of pixels equal to or greater than the threshold value (T) out of 50 x 100px (i.e., the number of pixels containing color material)) was calculated from the histogram.

[0144] AAA: Histogram ratio is 99.6 or more AA: Histogram ratio is 99.5 or more and less than 99.6 A: The histogram ratio is 99.4 or more and less than 99.5 B: Histogram ratio is 99.3 or more and less than 99.4 C: Histogram ratio is less than 99.3 (Image unevenness at the beginning of printing after a pause in printing) Using the combination of reaction liquid and ink shown in Table 7, an image was recorded with a reaction liquid recording duty of 30% and an ink recording duty of 100%. In order to record this image, 10,000 drops of ink were discharged from all the nozzles of the recording head at a drive frequency of 5 kHz in an environment of 15°C temperature and 10% relative humidity. After providing a 0.5 inch blank, ink and reaction liquid were discharged under the same conditions to record a 15 cm x 15 cm solid image on the recording medium. Furthermore, the ink discharge was not stopped, and only the reaction liquid was stopped for a certain period of time (3 to 6 seconds), after which the reaction liquid was discharged from the same nozzle as above to record a 15 cm x 15 cm solid image again.

[0145] In this way, the states of the two solid images recorded before and after the reaction liquid was stopped for a certain period of time were visually checked, and the intermittent ejection stability was evaluated according to the following evaluation criteria. Art paper (Art PW8k made by Lintec) was used as the recording medium.

[0146] AA: The uniformity of the solid image after the ejection of the reaction liquid was paused for 6 seconds was equivalent to that before the ejection was paused. A: The uniformity of the solid image after the ejection of the reaction liquid was paused for 5 seconds was the same as that before the ejection was paused. B: The uniformity of the solid image after the ejection of the reaction liquid was paused for 4 seconds was the same as that before the ejection was paused. C: After the ejection of the reaction liquid was paused for 3 seconds, the solid image showed unevenness in the starting part of the reaction liquid compared to before the ejection was paused. (Blurred image due to head nozzle sticking) Using the combination of reaction liquid and ink shown in Table 7, a tank filled with the reaction liquid was installed in the PC tank mounting position of the PIXUS Pro10S, and tanks filled with the same ink were installed in the GY tank and PBK tank mounting positions, and printing was performed using the two color recording heads.

[0147] The printing was performed by one-pass forward printing, where the scanning direction of the recording head was from the cap mounting position (home position) to the tank replacement position, and an image was formed in one forward scanning operation, and no printing was performed in the return direction on the way back. In other words, printing was performed by a printing method in which the ink was always printed after the reaction liquid was applied.

[0148] In addition, in the inkjet recording apparatus 100, an image recorded under conditions in which one ink droplet is applied to a unit area of ​​1 / 1200 inch×1 / 1200 inch is defined as having a recording duty of 100%.

[0149] The recording duty of the reaction liquid was set to 30% and the recording duty of the ink was set to 100%, and a pattern for forming a solid image was continuously recorded on a certain number of sheets of A4 paper. After that, a 6-point Gothic font was printed using the above-mentioned amount of ink and reaction liquid applied, and it was confirmed whether or not ejection failure occurred due to the adhered matter formed on the ejection port surface of the head, and this was used to evaluate the adhesion. The recording was performed on a recording medium (plain paper, product name "CS-064F", manufactured by Canon). The evaluation criteria for adhesion are as follows. AAA: After recording on 200 sheets, no defects were found in the characters and the condition was good. AA: After recording on 150 sheets, no defects were found in the characters and the condition was good. A: After recording on 100 sheets, no defects were found in the characters and the condition was good. B: After recording on 50 sheets, no defects were found in the characters and the condition was good. C: After recording on 50 sheets, many defects were found in the characters.

[0150] [Table 7]

Claims

1. An inkjet recording method for recording an image on a recording medium using an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, comprising: a reaction liquid applying step of ejecting the aqueous reaction liquid from an inkjet recording head onto the recording medium; an ink applying step of applying the aqueous ink to the recording medium by ejecting the aqueous ink from an inkjet recording head so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied, the reactant comprises a cationic resin; The cationic resin has a molecular weight distribution measured by gel permeation chromatography (GPC) of: A first cationic resin having a peak in a molecular weight range of 100,000 to 500,000; and A second cationic resin having a peak in a molecular weight region of 2,000 or more and less than 100,000, an ink jet recording method, wherein the content (mass %) of the second cationic resin is 0.01 to 8.0 times the content (mass %) of the first cationic resin in terms of a mass ratio.

2. The inkjet recording method according to claim 1 , wherein the content (mass %) of the second cationic resin is 0.01 to 0.30 times the content (mass %) of the first cationic resin in terms of a mass ratio.

3. The ink jet recording method according to claim 1 , wherein the second cationic resin has a peak in a molecular weight region of 10,000 or more and less than 100,000 in a molecular weight distribution measured by GPC of the reaction liquid.

4. 2. The ink jet recording method according to claim 1, wherein the first cationic resin and the second cationic resin each have a quaternary ammonium salt structure.

5. 2. The ink jet recording method according to claim 1, wherein the first cationic resin and the second cationic resin have the same repeating structural unit.

6. 2. The ink jet recording method according to claim 1, wherein the first cationic resin and the second cationic resin are both polymers having a repeating structural unit represented by the following general formula (1): 【Chemistry 1】 (In the general formula (1), R １ and R ２ each independently represents an alkyl group; X － represents a counter anion with the quaternary ammonium cation.)

7. The ink-jet recording method according to claim 1 , wherein the reactant contains a polyvalent metal salt.

8. 2. The ink-jet recording method according to claim 1, wherein the reaction liquid has a dynamic surface tension of 40 mN / m or less at a life time of 10 ms.

9. 2. The ink-jet recording method according to claim 1, wherein the reaction liquid has a viscosity of 1.5 mPa.s or more and 5.0 mPa.s or less.

10. In the Bristow method of the recording medium, １／２ The amount of water absorbed is 10 mL / m ２ The ink jet recording method according to claim 1, wherein:

11. Using an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink, An inkjet recording apparatus for use in an inkjet recording method for recording an image on a recording medium, comprising: an inkjet type reaction liquid applying means for ejecting the aqueous reaction liquid and applying it to the recording medium; an ink jet type ink applying means for ejecting the water-based ink onto the recording medium so as to overlap at least a portion of an area of ​​the recording medium onto which the water-based reaction liquid is applied, the reactant comprises a cationic resin; The cationic resin has a molecular weight distribution measured by gel permeation chromatography (GPC) of: A first cationic resin having a peak in a molecular weight range of 100,000 to 500,000; and A second cationic resin having a peak in a molecular weight region of 2,000 or more and less than 100,000, an ink jet recording apparatus, wherein a content (mass %) of the second cationic resin is 0.01 to 8.0 times the content (mass %) of the first cationic resin in terms of a mass ratio.

12. A set of an aqueous ink and an aqueous reaction liquid used in an inkjet recording method for recording an image on a recording medium using an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink, comprising: a reaction liquid applying step of ejecting the aqueous reaction liquid from an inkjet recording head onto the recording medium; an ink applying step of applying the aqueous ink to the recording medium by ejecting the aqueous ink from an inkjet recording head so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied, the reactant comprises a cationic resin; The cationic resin has a molecular weight distribution measured by gel permeation chromatography (GPC) of: A first cationic resin having a peak in a molecular weight range of 100,000 to 500,000; and A second cationic resin having a peak in a molecular weight region of 2,000 or more and less than 100,000, A set of an aqueous ink and an aqueous reaction liquid, characterized in that the content (mass %) of the second cationic resin is 0.01 times or more and 8.0 times or less in mass ratio to the content (mass %) of the first cationic resin.

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