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

Abstract

To provide an inkjet recording method capable of recording an image having suppressed unevenness when recording an image on a low-absorbing recording medium by one-pass method.SOLUTION: There is provided an inkjet recording method for recording an image on a low-absorbing recording medium using an aqueous ink and an aqueous reaction liquid containing a reaction agent reacting with the ink, by imparting the ink and the reaction liquid by one-pass method. The method comprises: a step of imparting the reaction liquid to the recording medium; and a step of imparting the ink to the recording medium so as to overlap with at least a part of the area in which the reaction liquid on the recording medium is imparted. The ink comprises a pigment. The reaction liquid contains a cationic resin having a quaternary ammonium salt structure and the surface tension of a liquid in which the surfactant of the reaction liquid is replaced by water at 25°C is 60 mN / m or more.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] An inkjet recording device is a device that ejects minute ink droplets from the ejection ports 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 absorbency for water-based ink or that barely absorb water-based ink. Examples of recording media that have low absorbency for water-based ink (hereinafter also referred to as "low absorbency recording media") include recording media having a coating layer such as art paper and coated paper. Examples of recording media that barely absorb water-based ink (hereinafter also referred to as "non-absorbency recording media") include plastic films.

[0003] As for the ink, the use of aqueous inks containing pigments (hereinafter also referred to as "pigment inks") has been considered from the viewpoints of environmental and safety aspects. Up until now, high-definition image quality has been obtained using pigment inks on recording media that easily absorb aqueous inks, such as recording media without a coating layer (e.g., plain paper, etc.). In contrast, for low-absorbency recording media or non-absorbency recording media, applied ink droplets are unlikely to penetrate into the recording media, so adjacent ink droplets are applied while the ink has not yet been fixed by penetration. As a result, the ink droplets coalesce and cause bleeding and unevenness, making it difficult to obtain high-definition image quality.

[0004] To address the above-mentioned issues, a reaction liquid (also called a treatment liquid) containing a polyvalent metal salt that reacts with components such as pigments in the ink to cause aggregation and thickening is used (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-012443 A [Patent Document 2] JP 2012-233161 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, with the increasing speed of printing, methods of applying ink to a printing medium by a so-called one-pass method and printing an image are being considered in order to produce a large amount of printed matter in a short time. The one-pass method is a method in which liquid such as ink or a reaction liquid is applied to a unit area of ​​a printing medium by a single relative scan between the printing head and the printing medium. In printing by the one-pass method, an image is printed on a unit area of ​​the printing medium by only a single relative scan between the printing head and the printing medium.

[0007] The present inventors performed one-pass printing on a low-absorbency recording medium using the reaction liquid and ink proposed in Patent Documents 1 and 2. As a result, it was found that if an image is recorded by applying the reaction liquid to the recording medium prior to the ink, and then applying the ink to the recording medium in a one-pass manner, the image may have high and low density areas, resulting in unevenness in the image.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording an image with suppressed unevenness when recording an image on a low-absorbency recording medium by a single pass method. Another object of the present invention is to provide an inkjet recording apparatus and a set of an aqueous ink and a reaction liquid for use in the inkjet recording method. [Means for solving the problem]

[0009] That is, according to the present invention, a water-based ink and a water-based reaction liquid containing a reactant that reacts with the water-based ink are used, and the reaction is carried out in a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 4mL / m 2More than 10mL / m 2 The present invention provides an inkjet recording method for recording an image on a recording medium that is described below by applying the aqueous ink and the reaction liquid to a unit area in a single relative scan of an inkjet ejection head and the recording medium, the inkjet recording method comprising: a reaction liquid application step of applying the reaction liquid to the recording medium; and an ink application step of applying the aqueous ink to the recording medium so as to overlap at least a portion of the area on the recording medium to which the reaction liquid is applied, the aqueous ink containing a pigment, the reaction liquid containing a cationic resin having a quaternary ammonium salt structure, and the surface tension of the liquid obtained by replacing the surfactant of the reaction liquid with water at 25°C is 60 mN / m or more. Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method capable of recording an image with reduced unevenness when recording an image on a low-absorbency recording medium by a single pass method. Also, according to the present invention, it is possible to provide an inkjet recording apparatus used in the inkjet recording method, and a set of an aqueous ink and a 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 for inkjet and the reaction liquid may be simply referred to as "ink" and "reaction liquid". The 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. In the present invention, the "unit" constituting the resin means a repeating unit derived from one monomer.

[0013] When an image is recorded by a two-liquid reaction system using a reaction liquid and an ink, the reaction liquid is generally applied to a recording medium, and then the ink is applied. In the inkjet recording method of the present invention, the order of application of the reaction liquid and the ink is not limited to the above order. 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, the order of application of the reaction liquid to the recording medium and then the ink will be described as an example.

[0014] The present inventors have conducted research to solve the image unevenness that occurs when an image is recorded on a low-absorbency recording medium by applying the reaction liquid and ink to the recording medium in a one-pass manner using an inkjet recording device. First, in order to understand the behavior of the reaction liquid and ink on the recording medium, the state of the droplets after the reaction liquid and ink are applied to the recording medium was observed. As a result, it was found that the reaction liquid quickly begins to permeate into the recording medium after it is applied to the recording medium. The reaction liquid present on the surface of the recording medium is reduced due to the permeation of the reaction liquid into the recording medium, so that the reaction liquid applied to the recording medium does not come into sufficient contact with the ink applied to the recording medium later. Therefore, the ink applied to the recording medium so as to overlap at least a part of the region on the recording medium where the reaction liquid is applied remains on the surface of the recording medium in a state of insufficient coagulation and insufficient thickening. It is presumed that the unevenness in the image occurs when the ink convection occurs on the surface of the recording medium, causing the pigment to move.

[0015] In one-pass printing, it is necessary to print an image of a unit area by one relative scan of the print head and the print medium. Therefore, in one-pass printing, a large amount of ink is applied at once, compared to multi-pass printing, in which the reaction liquid or ink is applied to the print medium in multiple divided applications to print an image. Therefore, it takes time for the ink to thicken upon contact with the reaction liquid, which makes it easy for ink convection to occur on the surface of the print medium, and as a result, it is thought that unevenness is likely to occur in the printed image.

[0016] The inventors of the present invention considered that in order to suppress the penetration of the reaction liquid into the recording medium, it would be effective to increase the surface tension of the reaction liquid immediately after it is applied to the recording medium. Therefore, first, a reaction liquid with an increased surface tension was prepared by adjusting the amount of surfactant, and an image was recorded. However, immediately after the reaction liquid was applied to the recording medium, most of the reaction liquid penetrated into the recording medium, and image unevenness could not be suppressed.

[0017] Generally, a liquid containing a surfactant that acts to reduce surface tension when an interface is formed will experience a decrease in surface tension over time after it is applied to an object such as a recording medium, that is, after the interface is formed, as the surfactant orients toward the interface.

[0018] The inventors confirmed the timing of the reaction liquid permeating into the low-absorbency recording medium, and found that the reaction liquid starts permeating into the recording medium before the surfactant is oriented at the interface. The surface tension adjusted using a surfactant indicates the surface tension after the surfactant is oriented at the interface, that is, the surface tension after the reaction liquid has already started permeating into the recording medium. Therefore, it is presumed that the permeation of the reaction liquid immediately after it is applied to the recording medium could not be suppressed.

[0019] The present inventors considered that in order to suppress the penetration of the reaction liquid into the recording medium, it is important to increase the surface tension of the liquid immediately after the interface is formed, that is, before the surfactant is oriented at the interface. In the present invention, as a method for simulating the surface tension of the reaction liquid immediately after the interface is formed, the surface tension of a reaction liquid in which the surfactant is replaced with water is measured.

[0020] The present inventors used the above-mentioned measurement method to prepare a reaction liquid in which the surface tension of the liquid in which the surfactant is replaced with water is increased immediately after it is applied to the recording medium, and recorded an image and examined it. As a result, it was found that image unevenness can be improved by making the surface tension of the reaction liquid in which the surfactant is replaced with water 60 mN / m or more at 25°C. However, the target level was still not reached.

[0021] The present inventors considered that suppressing the convection of the ink on the surface of the recording medium is effective in further improving image unevenness, and considered that it is important to increase the viscosity when the reaction liquid and the ink are mixed on the recording medium. As a result of the inventors' investigation, it was found that the viscosity of the mixture of the reaction liquid and the ink can be significantly increased by using a cationic resin having a quaternary ammonium salt structure as a reactant contained in the reaction liquid. It is presumed that the viscosity of the mixture of the reaction liquid and the ink is rapidly increased because a network structure is formed by the interaction between an anionic component (anionic group, etc.) that contributes to the dispersion of the pigment in the ink and the cationic group of the cationic resin in the reaction liquid. As a result, it is possible to suppress the convection of the ink on the surface of the recording medium and thereby suppress image unevenness.

[0022] The above-mentioned image unevenness is a phenomenon that occurs specifically when a low-absorbency recording medium is used as the recording medium. In this specification, the low-absorbency recording medium is a recording medium that is used for a period of time 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 In the case of plain paper or the like, which is a recording medium through which ink or reaction liquid permeates relatively quickly, the reaction liquid permeates quickly immediately after being applied to the recording medium, and then, after the ink applied to the recording medium comes into contact with the reaction liquid, the pigment and aqueous medium also permeate into the recording medium while flocculating. Therefore, ink convection does not occur on the surface of the recording medium, so there is almost no movement of the pigment, and an image with reduced unevenness can be obtained. On the other hand, in the case of a non-absorbing recording medium in which ink or reaction liquid is hardly absorbed, the reaction liquid hardly permeates, so the reaction liquid and ink come into sufficient contact on the surface of the non-absorbing recording medium, and the ink thickens sufficiently, so that ink convection is unlikely to occur and image unevenness is unlikely to occur. In this specification, a non-absorbing recording medium refers to a recording medium that is capable of being used for a period of time within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 4mL / m 2 In addition, an 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 10mL / m 2It means a recording medium that is super.

[0023] <Inkjet recording method and inkjet recording apparatus> The inkjet recording method of the present invention (hereinafter, also simply referred to as the "recording method") is a method of recording an image on a low-absorbency recording medium (hereinafter, sometimes simply referred to as the "recording medium") using an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink. In this recording method, the ink and the reaction liquid are applied to a unit area of ​​the recording medium using an inkjet ejection head, and an image is recorded by performing a single relative scan between the ejection head and the recording medium. This recording method includes a reaction liquid application step of applying the reaction liquid to the recording medium, and an ink application step of applying ink to the recording medium so as to overlap at least a part of the area on the recording medium to which the reaction liquid is applied. In addition, the inkjet recording device of the present invention (hereinafter, also simply referred to as the "recording device") is a device used in the above inkjet recording method. In addition, the set of the ink and reaction liquid of the present invention is a set used in the above inkjet recording method.

[0024] The ink in the recording method and recording apparatus of the present invention contains a pigment. The reaction liquid in the recording method and recording apparatus of the present invention contains a cationic resin having a quaternary ammonium salt structure, and the surface tension of the liquid obtained by replacing the surfactant of the reaction liquid with water at 25° C. is 60 mN / m or more. The recording medium in the recording method and recording apparatus of the present invention is a recording medium that is 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 The recording medium is as follows:

[0025] (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.

[0026] 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 are applied by a liquid application unit 1200 to a recording medium 1100 conveyed from a paper feeder 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.

[0027] [Recording Section] The recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a reaction liquid applying device 1201 and an ink applying device 1202. An inkjet type discharge head is used as the reaction liquid applying device 1201. The reaction liquid applied by the reaction liquid applying device 1201 may be applied either before or after the ink application as long as it can come into contact with 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 is applied. An inkjet type discharge head (recording head) is used as the ink applying device 1202. The discharge method of the discharge head as the liquid applying device 1200 can be exemplified by a method of discharging liquid by generating film boiling in the liquid by an electrothermal converter to form bubbles, a method of discharging liquid by an electromechanical converter, and the like.

[0028] Since the reaction liquid permeates the recording medium over time after it is applied to the recording medium, the shorter the time between the application of the reaction liquid and the application of the ink, the easier it is for the reaction liquid and the ink to come into contact with each other, and the easier it is to suppress image unevenness. Therefore, it is preferable that the time between the application of the reaction liquid to the recording medium in the reaction liquid application step and the application of the ink to the recording medium in the ink application step is 1,100 msec or less. The time is preferably 100 msec or more, and more preferably 500 msec or more.

[0029] 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.

[0030] 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".

[0031] 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.

[0032] 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.

[0033] [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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] [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 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.

[0038] [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.

[0039] 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 and a 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 and image unevenness can be more easily suppressed.

[0040] 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.

[0041] 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).

[0042] (drying process) The recording method of the present invention preferably includes a drying step in which the recording medium to which the reaction liquid and ink have been applied is dried using a heating device 2100. It is more preferable that the drying means in the drying step is hot air having a wind speed of 40 m / s or less. If the wind speed of the hot air is 40 m / s or less, image movement due to wind pressure is small, and image unevenness can be further suppressed. The wind speed of the hot air is preferably 10 m / s or more, and more preferably 20 m / s or more.

[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 from 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 the occurrence of transport failure.

[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 from 10 Pa to 1,000 Pa, and more preferably from 10 Pa to 500 Pa. Also, it is particularly preferably from 10 Pa to 400 Pa. 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.

[0051] 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.

[0052] [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).

[0053] [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)).

[0054] [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.

[0055] (Recording medium) The recording medium used is a recording medium with low absorbency for water-based ink (low-absorbency recording medium). As mentioned above, a low-absorbency recording medium is a recording medium that is absorbent for water-based ink 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 The recording medium is one that is as follows. The Bristow method is described in JAPAN TAPPI Paper Pulp Test Method No. 51, "Testing Method for Liquid Absorbency of Paper and Paperboard." Examples of low-absorbency recording media include recording media that do not have an ink-receiving layer, such as uncoated paper and synthetic paper, and recording media that have an ink-receiving layer, such as recording media with a thin ink-receiving layer. Specific examples of these include art paper, fine coated paper, medium coated paper, fine lightweight coated paper, medium lightweight coated paper, micro-coated paper, cast coated paper, and printing paper. The basis weight (g / m2) of the recording medium 1100 is 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:

[0056] <Reaction solution> The recording method of the present invention preferably includes a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink to a recording medium. 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, and causes the components in the ink (components having anionic groups, such as resins, surfactants, and self-dispersing pigments) to aggregate, and contains a reactant. The presence of the reactant destabilizes the state of the components having anionic groups in the ink when the ink and the reactant come into contact with each other on the recording medium, and can promote the aggregation of the ink. The reaction liquid used in the recording method of the present invention contains, as a reactant, a cationic resin having a quaternary ammonium salt structure (sometimes simply referred to as "cationic resin" in this specification).

[0058] [Cationic resin] A cationic resin refers to a resin having a cationic moiety in the molecular chain. The reaction liquid used in the recording method of the present invention contains a cationic resin having a quaternary ammonium salt structure as a cationic moiety. Since the cationic resin, which is the reactant, has a quaternary ammonium cation as a cationic moiety, it can stably maintain a cationic state even if a pH change occurs when it comes into contact with ink, and therefore it is easy to interact with an anionic component in the ink.

[0059] The counter anion of the cationic group of the cationic resin is a chloride ion (Cl - ) and other halide ions are preferred. As counter anions, ethyl sulfate ion (C2H5SO4 - ), but the halide ion has a smaller ion size than these, and is less likely to interfere with the interaction between the cationic moiety and the anionic components in the ink. Among the halide ions, the chloride ion is particularly preferred.

[0060] The weight average molecular weight of the cationic resin is preferably 3,000 or more and 50,000 or less, more preferably 4,000 or more and 30,000 or less. When the weight average molecular weight of the cationic resin is 3,000 or more, preferably 4,000 or more, the mixed viscosity with the ink becomes high, and the effect of suppressing image unevenness is further enhanced. On the other hand, when the weight average molecular weight of the cationic resin is 50,000 or less, preferably 30,000 or less, the mixed viscosity when contacting with the ink does not become too high, the unevenness of the surface of the recorded image is suppressed, and the effect of suppressing image unevenness is further enhanced. The weight average molecular weight of the cationic resin can be measured by gel permeation chromatography (GPC).

[0061] The structure of the quaternary ammonium salt of the cationic resin is preferably a unit represented by the following general formula (1): The unit represented by general formula (1) is a unit derived from a diallyldialkylammonium salt.

[0062] TIFF2024076960000001.tif45170

[0063] In the general formula (1), R1 and R2 each independently represent an alkyl group; - represents a counter anion with the quaternary ammonium cation, and n represents a repeating unit. The number of carbon atoms in the alkyl group represented by R1 and R2 is preferably 1 to 6, and more preferably 1 to 3. Of these, a methyl group and an ethyl group are more preferable. X - Examples of the counter anion represented by include a chloride ion, a methyl sulfate ion, an ethyl sulfate ion, etc., and among these, as described above, a chloride ion is preferred. The repeating unit represented by n is preferably a number such that the weight average molecular weight of the cationic resin having the unit represented by general formula (1) falls within the above-mentioned range.

[0064] Among the units represented by the general formula (1), R1 and R2 in the general formula (1) are methyl groups, X - Cl - In addition, in the general formula (1), R1 is a methyl group, R2 is an ethyl group, and X is a unit derived from diallyldimethylammonium chloride. - C2H5SO4 - Preferred are units derived from diallyl methyl ethyl ammonium ethyl sulfate, which is a unit of the formula: Diallyl dimethyl ammonium chloride is particularly preferred. Since a unit derived from diallyl dimethyl ammonium chloride has a quaternary ammonium cation in the side chain, it is less susceptible to steric hindrance than a unit having a quaternary ammonium cation in the main chain. This makes it easier to interact with an anion component in the ink, which further enhances the effect of suppressing image unevenness.

[0065] The charge density (meq / g) of the cationic resin can be measured by the following method. The charge density is a value calculated from the amount of potassium polyvinyl sulfate solution required to reach the isoelectric point measured by colloid titration for an aqueous solution of cationic resin at pH 7, and indicates the amount of charge per gram of cationic resin. The charge density can be measured by a method known as colloid titration. The principle and measurement method are described below. In the examples described later, the charge density (meq / g) was measured by the following measurement method, and the amount of cationic groups (mmol / g) was calculated.

[0066] (principle) Toluidine blue (TB) is a basic dye that is not adsorbed by positive colloids that have amino groups, but is immediately adsorbed by negative colloids and changes color to reddish purple. Using this phenomenon, for example, TB is added to an aqueous solution of cationic resin, and a dilute solution of potassium polyvinyl sulfate (PVSK) is added dropwise. PVSK then reacts preferentially with the cationic groups, and initially there is no color change in TB, but once the equivalence point is passed, the excess PVSK reacts with TB, and the solution changes color from blue to reddish purple. By using TB as an indicator, the charge density can be calculated from the amount of PVSK consumed.

[0067] (Method of measuring charge density) (1) Accurately weigh the sample (0.05-0.15 g as solids) into a 100 mL measuring flask, and add ion-exchanged water up to the mark. (2) Transfer 10 mL of this sample solution to a 50 mL beaker using a volumetric pipette. (3) The pH of the sample solution can be adjusted appropriately by adding a few drops of a dilute ammonia solution or acetic acid solution. (4) Place the beaker on a magnetic stirrer, insert a rotor, and gently stir. (5) When 2-3 drops of TB solution are added, the solution turns blue (sky blue), but (6) when 1 / 500 PVSK is dropped into the beaker using a 10 mL burette, a precipitate forms near the equivalence point, and the solution becomes cloudy. (7) Further drop PVSK, and when the liquid phase changes color from blue to reddish purple, stop dropping PVSK and read the burette scale. Calculate the charge density using the following formula.

[0068] TIFF2024076960000002.tif25170V: Titration volume (mL) of 1 / 500 PVSK aqueous solution S: Sample collection amount (g) N: Sample solid content (mass%)

[0069] The content (mass%) of the cationic resin (solid content) having a quaternary ammonium salt structure in the reaction solution is preferably 0.10 mass% or more and 10.00 mass% or less based on the total mass of the reaction solution, more preferably 0.20 mass% or more and 5.00 mass% or less, and even more preferably 0.30 mass% or more and 3.00 mass% or less.

[0070] The reaction solution may contain other reactants, if necessary, in addition to the cationic resin described above. Examples of the other reactants include cationic components such as polyvalent metal ions and organic acids.

[0071] [Polyvalent metal salts] The reaction liquid preferably contains a polyvalent metal salt as a reactant in addition to the cationic resin having the above-mentioned quaternary ammonium salt structure. The polyvalent metal salt is ionically dissociated into polyvalent metal ions and anions in the aqueous reaction liquid, and the polyvalent metal ions react with the aqueous ink. When the cationic resin and the polyvalent metal salt are used in combination, the lower molecular weight polyvalent metal ions react quickly with the anion components in the ink to form aggregates, and then the cationic resin having the quaternary ammonium salt structure reacts. This can shorten the time it takes for the ink to thicken, thereby enhancing the effect of suppressing image unevenness.

[0072] Examples of polyvalent metal ions 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 Al3+ Examples of the trivalent metal ions include trivalent metal ions such as Cl. In order to incorporate polyvalent metal ions into the reaction solution, a polyvalent metal salt (which may be a hydrate) formed by combining a polyvalent metal ion with an anion can be used. In other words, a polyvalent metal salt that generates polyvalent metal ions in the reaction solution can be added to the reaction solution. Examples of the anion in the polyvalent metal salt include 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 - , C2H4(COO - )2, CH3CH(OH)COO - , C6H5COO - , C6H4(COO - )2, and CH3SO3 - The reaction solution may contain one or more polyvalent metal salts. Among the polyvalent metal salts, magnesium sulfate is preferably used.

[0073] When a polyvalent metal salt is used as a reactant in addition to the cationic resin, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 0.05% by mass or more and 20.00% by mass or less based on the total mass of the reaction solution. The content (mass%) of the polyvalent metal salt is more preferably 1.00% by mass or more and 15.00% by mass or less. 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.

[0074] [Organic acid] 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 1.00 mass % or more and 50.00 mass % or less based on the total mass of the reaction liquid.

[0075] [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 below. The aqueous medium used in the reaction liquid can contain a water-soluble organic solvent that can be contained in the ink described below. The content (mass%) of water in the reaction liquid is preferably 80.00 mass% or more and 99.50 mass% or less, and more preferably 85.00 mass% or more and 99.00 mass% or less, based on the total mass of the reaction liquid.

[0076] Examples of water-soluble organic solvents that can be suitably contained in the reaction liquid include alkanediols such as 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; amino acids such as β-alanine and trimethylglycine; 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. One or more of these can be contained in the reaction liquid.

[0077] The water-soluble organic solvent as described above has the function of lowering the surface tension of the liquid immediately after the interface is formed. Since the surface tension of the liquid in which the surfactant of the reaction liquid is replaced with water at 25°C must be 60 mN / m or more, the water-soluble organic solvent can be used within the range that satisfies this requirement. The surface tension of the liquid in which the surfactant of the reaction liquid is replaced with water is preferably 64 mN / m or more. The surface tension of the liquid in which the surfactant of the reaction liquid is replaced with water is the surface tension value of the liquid prepared by mixing the components in the reaction liquid except for the surfactant. The surface tension of the liquid in which the surfactant of the reaction liquid is replaced with water at 25°C is preferably 74 mN / m or less. The surface tension of the liquid in which the surfactant of the reaction liquid is replaced with water at 25°C is the static surface tension measured by the platinum plate method.

[0078] When the composition of the reaction liquid is unknown, it is necessary to quantify the aqueous medium contained in the reaction liquid. Specifically, first, the amount of water and water-soluble organic solvent contained in the reaction liquid is measured. 2 g of the reaction liquid is weighed into a petri dish and left to dry in an oven at 110 ° C. for 24 hours. The mass after drying is measured, and the solid content (1) is calculated by "mass after drying / mass before drying x 100". The amount (2) of water and water-soluble organic solvent contained in the reaction liquid can be calculated by calculating 100-(1). Next, the amount of water-soluble organic solvent in the reaction liquid is quantified. The reaction liquid is diluted with methanol or the like, and the amount of water-soluble organic solvent contained in the reaction liquid is quantified by gas chromatography mass spectrometry. The total amount of water-soluble organic solvent is (3). The content of water in the reaction liquid can be calculated from (2)-(3). From the composition quantified as above, it is preferable to mix the water-soluble organic solvent and water to prepare an aqueous medium excluding the surfactant, and add a component other than the aqueous medium such as a cationic resin to prepare a liquid in which the surfactant of the reaction liquid is replaced with water. By measuring the surface tension of this liquid, it is possible to estimate the surface tension immediately after the interface is formed.

[0079] The reaction liquid may not contain a water-soluble organic solvent, and the content (mass%) of the water-soluble organic solvent in the reaction liquid is preferably 10.00 mass% or less based on the total mass of the reaction liquid. When the reaction liquid contains a water-soluble organic solvent, the content (mass%) of the water-soluble organic solvent in the reaction liquid is more preferably 1.00 mass% or more and 10.00 mass% or less, and even more preferably 1.00 mass% or more and 5.00 mass% or less.

[0080] (Surfactant) The reaction liquid may contain various surfactants. A surfactant is a molecule having a hydrophobic portion and a hydrophilic portion, and significantly reduces the static surface tension of the liquid. Examples of the surfactant include a hydrocarbon-based surfactant, a fluorosurfactant, and a silicone-based surfactant. One or more of these may be contained in the reaction liquid. These surfactants may be nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Specific examples of the surfactant include hydrocarbon-based surfactants such as ethylene oxide adducts of acetylene glycol, polyethylene glycol alkyl ethers, and polyoxyethylene polyoxypropylene block polymers; fluorosurfactants such as perfluoroalkylethylene oxide adducts; and silicone-based surfactants such as polyether-modified siloxane compounds. Among them, it is preferable that the reaction liquid contains a hydrocarbon-based surfactant. The content (mass%) of the surfactant in the reaction liquid is preferably 0.01 mass% or more and 5.00 mass% or less based on the total mass of the reaction liquid.

[0081] [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.

[0082] [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 value. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less, and more preferably 23 mN / m or more and 35 mN / m or less. When the surface tension of the reaction liquid at 25°C is 23 mN / m or more, the reaction liquid is gradually leveled after being applied to the recording medium, so that the reaction liquid is less likely to penetrate into the recording medium, the contact with the ink is increased, and the effect of suppressing image unevenness is enhanced. Furthermore, when the surface tension of the reaction liquid at 25°C is 35 mN / m or less, the wettability of the ink and the reaction liquid is increased, and the reaction efficiency is increased, so that the effect of suppressing image unevenness is enhanced.

[0083] 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 2.7 mPa·s or less. When the viscosity of the reaction liquid at 25°C is 1.5 mPa·s or more, the penetration of the reaction liquid into the recording medium is suppressed, and the effect of suppressing image unevenness is enhanced. Furthermore, when the viscosity of the reaction liquid at 25°C is 2.7 mPa·s or less, the reaction liquid is easily diffused when it comes into contact with the ink and the cohesiveness is increased, so the effect of suppressing image unevenness is enhanced. The pH of the reaction liquid at 25°C is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0084] <Ink> The ink used in the recording method of the present invention is an aqueous inkjet ink containing a pigment as a coloring material. Each component used in the ink will be described in detail below. The ink does not need to be cured by active energy rays such as ultraviolet rays or electron beams, and therefore does not need to contain a monomer that polymerizes when irradiated with active energy rays.

[0085] [Colorant] The ink contains a pigment as a coloring material. The ink may further contain a dye as a coloring material. The ink may contain one or more types of coloring materials. The content (mass %) of the coloring material in the ink is preferably 0.50 mass % or more and 15.00 mass % or less, and more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the ink.

[0086] 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.

[0087] 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.

[0088] 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 it is preferable to use a resin as described below, especially a water-soluble resin. 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.

[0089] The self-dispersing pigment may be one in which an anionic group is bonded to the particle surface of the pigment directly or via another atomic group (-R-). Specific examples of the other atomic group (-R-) include linear or branched alkylene groups having 1 to 12 carbon atoms; arylene groups such as phenylene groups and naphthylene groups; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Groups that combine these groups may also be used.

[0090] It is preferable to use a dye having an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes.

[0091] Examples of the anionic group described in the description of the resin dispersant, the self-dispersing pigment, and the dye include a carboxylic acid group, a sulfonic acid group, and a phosphonic acid group. 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. The colorant contained in the ink is preferably a pigment, and more preferably a resin-dispersed pigment or a self-dispersed pigment.

[0092] The amount of anionic groups in the pigment (mmol / g) can be measured by the colloid titration method described above. From the viewpoint of easier suppression of image unevenness, the ratio of the amount of cationic groups in the reaction liquid (mmol / g) to the amount of anionic groups in the pigment in the ink (mmol / g) is preferably 2.0 or more. It is more preferable that the ratio of the amount of cationic groups in the reaction liquid to the amount of anionic groups in the pigment in the ink is 5.0 or more and 45.0 or less. The amount of cationic groups in the reaction liquid is determined from the amount of cationic groups in the cationic resin in the reaction liquid, or, when the reaction liquid contains a polyvalent metal salt in addition to the cationic resin, the total amount of the amount of cationic groups in the cationic resin and the amount of cationic groups in the polyvalent metal salt. The amount of cationic groups in the polyvalent metal salt can also be measured by the colloid titration method described above.

[0093] [resin] The ink can contain a resin. By using an ink containing a resin, an image with improved abrasion 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, or (ii) to improve various properties of the recorded image.

[0094] 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.

[0095] [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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] [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, the resin is present in an aqueous medium in a state in which it does not form particles whose particle size can be measured by a dynamic light scattering method. 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. Then, when the particle size of the resin in the sample solution is measured by a dynamic light scattering method, 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 times, and measurement time: 180 seconds. In addition, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as a particle size distribution measuring device. Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0100] 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.

[0101] 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 (D50 ) 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.

[0102] [Wax particles] The ink may contain particles formed of wax (wax particles). 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 0.10 mass % or more and 10.00 mass % or less, and more preferably 1.00 mass % or more and 5.00 mass % or less, based on the total mass of the ink.

[0103] 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).

[0104] 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.

[0105] 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.

[0106] [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, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the aqueous ink is preferably 50.00 mass% or more and 95.00 mass% or less based on the total mass of the ink. In addition, the content (mass%) of the water-soluble organic solvent in the aqueous ink is preferably 2.00 mass% or more and 40.00 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.

[0107] [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.

[0108] 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 from 1.00 mass % to 20.00 mass % based on the total mass of the ink.

[0109] 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.

[0110] [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.

[0111] [Ink properties] The ink is an aqueous 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, and more preferably 20 mN / m or more and 40 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, and more preferably 1.0 mPa·s or more and 7.0 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.

[0112] In addition, in the inkjet recording method using the reaction liquid and the ink, the reaction liquid and the ink are mixed on the recording medium, and the viscosity of the mixture increases to record an image, so that the viscosity of the mixture affects the image. It is preferable that the mass ratio of the amount of the reaction liquid applied to the amount of the ink applied to the recording medium (amount of the reaction liquid applied / amount of the ink applied) is in the range of 0.05 to 0.80, and the viscosity of the mixture obtained by mixing the ink and the reaction liquid is 10 times to 100 times the viscosity of the ink. If the viscosity of the mixture of the ink and the reaction liquid is 10 times or more the viscosity of the ink, the effect of suppressing image unevenness is further enhanced. Furthermore, if the viscosity of the mixture of the ink and the reaction liquid is 100 times or less the viscosity of the ink, the reactant does not become excessive, there is no precipitation in the image, and the effect of suppressing image unevenness is not impaired, and a good image can be obtained. The viscosity of the mixture of the ink and the reaction liquid can be measured at 25°C using a rotational viscometer. EXAMPLES

[0113] 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 invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0114] <Preparation of reaction solution> Cationic resins 1 to 7 shown in Table 1 were prepared. The charge density (meq / g) of the cationic resin was measured by the colloid titration method described above.

[0115] The weight average molecular weight of the cationic resin was measured using gel permeation chromatography (trade name "Waters ALLIANCE e2695", manufactured by Waters) under the following conditions in terms of polystyrene. Columns: Product names "Asahipak GF-310 HQ" and "Asahipak GF-510 HQ" (both manufactured by Showa Denko) Eluent: 0.5 mol / L acetic acid, 0.1 mol / L sodium nitrate - Delivery speed: 1.0mL / min Oven temperature: 40℃ Detector: Refractive index (RI) detector (product name "Wyatt Optilab rex Refractive Index Detector", manufactured by Wyatt Technology) The weight average 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).

[0116] TIFF2024076960000003.tif92170

[0117] The components (unit: %) shown in the upper part of Table 2 (Table 2-1 to Table 2-4) were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (Advantec) with a pore size of 3.0 μm to prepare each reaction solution. "Acetylenol E100" shown in Table 2 is the product name of a surfactant manufactured by Kawaken Fine Chemicals (same as in Table 3 below). "BYK-348" is the product name of a surfactant manufactured by BYK Japan. "Proxel GXL (S)" is the product name of a preservative manufactured by LONZA (same as in Table 3 below). The lower part of Table 2 shows the properties of the reaction solution, including the surface tension (mN / m) of the liquid in which the surfactant of the reaction solution was replaced with water at 25°C, as well as the surface tension (mN / m), viscosity (mPa·s), and amount of cationic groups R (mmol / g) of the reaction solution. The amount of cationic groups (mmol / g) of the reaction solution was measured as follows. The amount of cationic groups R (mmol / g) was calculated based on the content (%) of each of the polyvalent metal salt (magnesium sulfate) and the cationic resin from the charge amount (meq / g) of each of these components measured by the above-mentioned colloid titration method.

[0118] The surface tension of the liquid in which the surfactant of the reaction liquid was replaced with water at 25°C was measured for a sample prepared by mixing and stirring the components shown in Table 2 except for the surfactants (Acetylenol E100, BYK-348). The surface tension of the reaction liquid was measured for a sample prepared by mixing and stirring all the components shown in Table 2. The surface tension was measured using an automatic surface tensiometer (DY-300 type; manufactured by Kyowa Interface Science Co., Ltd.) by the platinum plate method. The viscosity of the reaction liquid was measured using an E-type viscometer (product name "RE-85L", manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and 50 rpm.

[0119] TIFF2024076960000004.tif168170

[0120] TIFF2024076960000005.tif168170

[0121] TIFF2024076960000006.tif169170

[0122] TIFF2024076960000007.tif168170

[0123] <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 then an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.00%. 15.0 parts of pigment (CI Pigment Blue 15:3), 22.5 parts of the aqueous solution of resin 1, and 62.5 parts of pure water were mixed to obtain a mixture. 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 centrifuging to remove coarse particles, the mixture was pressure-filtered with a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare pigment dispersion 1 with a pigment content of 15.00% and a resin dispersant (resin 1) content of 4.50%. The amount of anionic groups in the pigment in this pigment dispersion 1 was measured by the above-mentioned colloid titration method and was found to be 0.80 mmol / g.

[0124] (Pigment dispersion 2) 1.6 g of 4-amino-1,2-benzenedicarboxylic acid was added to a solution of 5.0 g of concentrated hydrochloric acid in 5.5 g of water while cooling 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 1.8 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, 6.0 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; manufactured by Advantis), 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 15.00%, 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. Then, the sodium ions in the pigment dispersion were replaced with potassium ions using an ion exchange method to obtain Pigment Dispersion 2, in which a self-dispersing pigment was dispersed on the surface of the pigment, with benzenedicarboxylic acid groups bonded to the pigment with potassium as the counter ion. The amount of anionic groups in the self-dispersing pigment was measured by the colloid titration method described above and found to be 0.40 mmol / g. The pigment content of the pigment dispersion 2 prepared above was 15.00%, and the average particle size of the pigment was 120 nm.

[0125] (Pigment dispersion 3) Pigment dispersion 3 was prepared with a pigment content of 15.00% and a resin dispersant (resin 1) content of 4.50% in the same manner as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 122. The amount of anionic groups of the pigment in this pigment dispersion 3 was measured by the colloid titration method described above and found to be 0.80 mmol / g.

[0126] (Pigment Dispersion 4) Except for changing the pigment to carbon black, pigment dispersion 4 having a pigment content of 15.00% and a resin dispersant (resin 1) content of 4.50% was prepared in the same manner as for pigment dispersion 1. The amount of anionic groups of the pigment in this pigment dispersion 4 was measured by the colloid titration method described above and found to be 0.80 mmol / g.

[0127] (Pigment Dispersion 5) Pigment dispersion 5 was prepared with a pigment content of 15.00% and a resin dispersant (resin 1) content of 4.50% in the same manner as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 74. The amount of anionic groups of the pigment in this pigment dispersion 5 was measured by the colloid titration method described above and found to be 0.80 mmol / g.

[0128] <Preparation of resin particles> (Resin particles 1) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 59.5 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 20.0 parts of 2-ethylhexyl methacrylate, 20.0 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "ADEKA REASOAP ER-20", manufactured by ADEKA) were mixed to prepare an emulsion. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over 1 hour, and a polymerization reaction was carried out for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion of resin particles 1 having a resin particle (solid content) content of 40.00% and a glass transition temperature of 72°C.

[0129] <Ink Preparation> Each component (unit: %) shown in the upper row of Table 3 was mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare each ink. The lower row of Table 3 shows the ink properties, such as the surface tension (mN / m) of the ink at 25° C. and the amount I (mmol / g) of anionic groups of the pigment in the ink. The surface tension of the ink was measured for a sample prepared by mixing and stirring all of the components shown in the upper row of Table 3. The surface tension is shown as a value measured by the platinum plate method using an automatic surface tensiometer (DY-300 type; manufactured by Kyowa Interface Science).

[0130] TIFF2024076960000008.tif112170

[0131] <Recording Media> The recording media shown in Table 4 were prepared. The amount of water absorbed was measured at 30 msec from the start of contact in the Bristow method. 1 / 2 This indicates the amount of water absorbed up to

[0132] TIFF2024076960000009.tif83170

[0133] <Evaluation> Table 5 shows the recording conditions, and the left column of Table 6 shows the evaluation conditions. The types of reaction liquid and ink shown in the left column of Table 6 were combined to form a set of ink and reaction liquid. In Table 6, "R / I value (times)" is the ratio of the amount R (mmol / g) of cationic groups in the reaction liquid to the amount I (mmol / g) of anionic groups of the pigment in the ink. The reaction liquid and ink constituting this set were respectively filled in the reaction liquid applying device 1201 and the ink applying device 1202 of the inkjet recording device 100 having the configuration shown in FIG. 1. Using this inkjet recording device 100, an image was recorded under the conditions shown in the left columns of Tables 5 and 6. Specifically, the reaction liquid (recording duty 30%) and the ink (recording duty 100%) were applied to the recording medium in this order, and then hot air at 60°C was applied to the recording medium from the heating device 2100 to dry the image, and a solid image of 15 cm x 15 cm was recorded. In the inkjet recording device 100 used in this embodiment, an image recorded under conditions in which one 4.0 ng ink droplet is applied to a unit area of ​​1 / 1200 inch x 1 / 1200 inch is defined as having a recording duty of 100%. The "application time difference (msec)" shown in Table 5 is the time from when the reaction liquid is applied to the recording medium to when the ink is applied to the recording medium. In this embodiment, in the following evaluation criteria, "AAA", "AA", "A" and "B" were defined as acceptable levels, and "C" was defined as an unacceptable level. The evaluation results are shown in the right column of Table 6.

[0134] TIFF2024076960000010.tif83170

[0135] (Image unevenness) The image recorded as described above was left in an environment with a temperature of 23°C and a relative humidity of 50% for 24 hours. After that, the image was captured using a scanner (product name "OFFIRIO ES-10000G", manufactured by Seiko Epson) under the conditions of mode: professional, resolution: 300 dpi, and color: 24 bit. Using image / photo editing software (product name "Adobe Photoshop", manufactured by Adobe), a range of 200 pixels x 200 pixels was converted to grayscale. A reference image sample (a record without image unevenness) was prepared, cut out to 50 pixels x 100 pixels, and pasted on a new clipboard. The threshold value (T) of the boundary for two-tone correction was lowered by 1, and the point where it touched the bottom of the peak was set as the threshold value. Then, the evaluation image sample was cut out to 50 pixels x 100 pixels and pasted on a new clipboard to perform two-tone correction. The threshold value (T) obtained above was used as the threshold value for the boundary of the two-level gradation, and the ratio was obtained from the histogram. Image unevenness was evaluated according to the following evaluation criteria from the average value of the histogram ratios for the two types of recording media. AAA: The average ratio of the histogram was 99.8 or higher. AA: The average value of the histogram ratio was greater than or equal to 99.7 and less than 99.8. A: The average ratio of the histogram was greater than or equal to 99.6 and less than 99.7. B: The average ratio of the histogram was greater than or equal to 99.5 and less than 99.6. C: The average ratio of the histogram was less than 99.5.

[0136] TIFF2024076960000011.tif254170

[0137] The disclosure of this embodiment includes the following methods and configurations. (Method 1) Using an aqueous ink and an aqueous reaction solution containing a reactant that reacts with the aqueous ink, the ink is subjected to a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 4mL / m 2 More than 10mL / m2 An inkjet recording method for recording an image on a recording medium by performing a single relative scan of an inkjet ejection head and the recording medium on the unit area of ​​the recording medium, the method comprising: a reaction liquid applying step of applying the reaction liquid to the recording medium; an ink applying step of applying the water-based ink to the recording medium so as to overlap at least a portion of an area of ​​the recording medium to which the reaction liquid is applied, The water-based ink contains a pigment, The inkjet recording method according to claim 1, wherein the reaction liquid contains a cationic resin having a quaternary ammonium salt structure, and the surface tension of the reaction liquid obtained by replacing the surfactant in the reaction liquid with water at 25°C is 60 mN / m or more. (Method 2) The inkjet recording method according to Method 1, wherein the cationic resin has a weight average molecular weight of 4,000 or more. (Method 3) The inkjet recording method according to Method 1 or 2, wherein the structure of the quaternary ammonium salt of the cationic resin is a unit represented by the following general formula (1):

[0138] TIFF2024076960000012.tif45170 (In the general formula (1), R1 and R2 each independently represent an alkyl group, and X - represents a counter anion with the quaternary ammonium cation, and n represents a repeating unit.

[0139] (Method 4) The inkjet recording method according to any one of Methods 1 to 3, wherein the reaction liquid contains a polyvalent metal salt. (Method 5) The inkjet recording method according to any one of Methods 1 to 4, wherein the reaction liquid has a surface tension at 25° C. of 23 mN / m or more and 35 mN / m or less. (Method 6) The inkjet recording method according to any one of Methods 1 to 5, wherein the reaction liquid has a viscosity at 25° C. of 1.5 mPa·s or more and 2.7 mPa·s or less. (Method 7) The inkjet recording method according to any one of Methods 1 to 6, wherein the ratio of the amount (mmol / g) of the cationic groups in the reaction liquid to the amount (mmol / g) of the anionic groups in the pigment in the aqueous ink is 2.0 or more. (Method 8) The inkjet recording method according to any one of Methods 1 to 7, wherein the time from when the reaction liquid is applied to the recording medium in the reaction liquid application step to when the aqueous ink is applied to the recording medium in the ink application step is 1,100 msec or less. (Method 9) The inkjet recording method according to any one of Methods 1 to 8, further comprising a drying step of drying, by means of a heating device, the recording medium onto which the reaction liquid and the aqueous ink have been applied. (Method 10) The inkjet recording method according to Method 9, wherein the drying means in the drying step is hot air having a wind speed of 40 m / s or less. (Configuration 1) Using an aqueous ink and an aqueous reaction solution containing a reactant that reacts with the aqueous ink, the ink is subjected to a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 4mL / m 2 More than 10mL / m 2 An inkjet recording apparatus for use in an inkjet recording method, which records an image on a recording medium by applying the aqueous ink and the reaction liquid to a unit area by performing a single relative scan between an inkjet ejection head and the recording medium, comprising: the inkjet recording method includes a reaction liquid applying step of applying the reaction liquid to the recording medium, and an ink applying step of applying the water-based ink to the recording medium so as to overlap at least a portion of an area of ​​the recording medium to which the reaction liquid is applied, The water-based ink contains a pigment, The inkjet recording apparatus is characterized in that the reaction liquid contains a cationic resin having a quaternary ammonium salt structure, and the surface tension of the liquid obtained by replacing the surfactant of the reaction liquid with water at 25°C is 60 mN / m or more. (Configuration 2) Using an aqueous ink and an aqueous reaction solution containing a reactant that reacts with the aqueous ink, the ink is subjected to a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 4mL / m 2 More than 10mL / m 2 A set of an aqueous ink and a reaction liquid used in an inkjet recording method, in which the aqueous ink and the reaction liquid are applied to a unit area on a recording medium, which is one of the following, by performing a single relative scan between an inkjet ejection head and the recording medium, thereby recording an image, the inkjet recording method includes a reaction liquid applying step of applying the reaction liquid to the recording medium, and an ink applying step of applying the water-based ink to the recording medium so as to overlap at least a portion of an area of ​​the recording medium to which the reaction liquid is applied, The water-based ink contains a pigment, A set of an aqueous ink and a reaction liquid, characterized in that the reaction liquid contains a cationic resin having a quaternary ammonium salt structure, and the surface tension of a liquid obtained by replacing the surfactant of the reaction liquid with water at 25°C is 60 mN / m or more.

Claims

1. Using an aqueous reaction solution containing an aqueous ink and a reagent that reacts with the aqueous ink, the Bristow method was used for 30 msec from the start of contact. １／２ Up to 4 mL / m² of water absorption capacity ２ 10mL / m or more ２ An inkjet recording method for recording an image on a recording medium, wherein the aqueous ink and the reaction solution are applied to a unit area by a single relative scan between an inkjet ejection head and the recording medium, A reaction solution application step of applying the reaction solution to the recording medium, The process includes an ink application step of applying the aqueous ink to the recording medium such that it overlaps with at least a portion of the area on the recording medium to which the reaction solution is applied, The aforementioned aqueous ink contains a pigment, An inkjet recording method characterized in that the reaction solution contains a cationic resin having the structure of a quaternary ammonium salt, and the surface tension of the liquid obtained by replacing the surfactant in the reaction solution with water at 25°C is 60 mN / m or more.

2. The inkjet recording method according to claim 1, wherein the surface tension of the liquid obtained by replacing the surfactant in the reaction solution with water at 25°C is 74 mN / m or less.

3. The inkjet recording method according to claim 1, wherein the weight-average molecular weight of the cationic resin is 4,000 or more.

4. The inkjet recording method according to claim 3, wherein the weight-average molecular weight of the cationic resin is 50,000 or less.

5. The inkjet recording method according to claim 1, wherein the structure of the quaternary ammonium salt of the cationic resin is a unit represented by the following general formula (1). (In the above general formula (1), R １ and R ２ Each of these independently represents an alkyl group, X － (where n represents the counter anion with the quaternary ammonium cation, and n represents the repeating unit.)

6. The inkjet recording method according to claim 5, wherein R1 and R2 in the general formula (1) are methyl groups and X- is Cl-.

7. The inkjet recording method according to claim 1, wherein the content (mass%) of the cationic resin in the reaction solution is 0.10% by mass or more and 10.00% by mass or less, based on the total mass of the reaction solution.

8. The inkjet recording method according to claim 1, wherein the reaction solution contains a polyvalent metal salt.

9. The inkjet recording method according to claim 8, wherein the polyvalent metal salt comprises magnesium sulfate.

10. The inkjet recording method according to claim 8 or 9, wherein the content (mass%) of the polyvalent metal salt in the reaction solution is 0.05% by mass or more and 20.00% by mass or less, based on the total mass of the reaction solution.

11. The inkjet recording method according to claim 1, wherein the surface tension of the reaction solution at 25°C is 23 mN / m or more and 35 mN / m or less.

12. The inkjet recording method according to claim 1, wherein the viscosity of the reaction solution at 25°C is 1.5 mPa·s or more and 2.7 mPa·s or less.

13. The inkjet recording method according to claim 1, wherein the ratio of the amount of cationic groups (mol / g) of the reaction solution to the amount of anionic groups (mol / g) of the pigment in the aqueous ink is 2.0 or more.

14. The inkjet recording method according to claim 13, wherein the ratio of the amount of cationic groups (mol / g) in the reaction solution to the amount of anionic groups (mol / g) in the pigment in the aqueous ink is 5.0 or more and 45.0 or less.

15. The inkjet recording method according to claim 1, wherein the time from when the reaction solution is applied to the recording medium by the reaction solution application step until when the aqueous ink is applied to the recording medium by the ink application step is 1,100 msec or less.

16. The inkjet recording method according to claim 15, wherein the time from when the reaction solution is applied to the recording medium by the reaction solution application step until when the aqueous ink is applied to the recording medium by the ink application step is 100 msec or more.

17. The inkjet recording method according to claim 1, further comprising a drying step of drying the recording medium to which the reaction solution and the aqueous ink have been applied using a heating device.

18. The inkjet recording method according to claim 17, wherein the drying means in the drying step is hot air with a wind speed of 40 m / s or less.

19. Using a water-based ink and a water-based reaction liquid containing a reactive agent that reacts with the water-based ink, in the Bristow method, from the start of contact to 30 msec １／２ water absorption amount up to is 4 mL / m ２ or more and 10 mL / m ２ or less on a recording medium, the application of the water-based ink and the reaction liquid to a unit region is performed in one relative scan between an inkjet-type ejection head and the recording medium, and the inkjet recording apparatus is used in an inkjet recording method for recording an image, the inkjet recording apparatus comprising: The inkjet recording method includes a reaction solution application step of applying the reaction solution to the recording medium, and an ink application step of applying the aqueous ink to the recording medium such that it overlaps with at least a portion of the area on the recording medium to which the reaction solution is applied. The aforementioned aqueous ink contains a pigment, An inkjet recording apparatus characterized in that the reaction solution contains a cationic resin having the structure of a quaternary ammonium salt, and the surface tension of the liquid obtained by replacing the surfactant in the reaction solution with water at 25°C is 60 mN / m or more.

20. Using an aqueous reaction solution containing an aqueous ink and a reagent that reacts with the aqueous ink, the Bristow method was used for 30 msec from the start of contact. １／２ Up to 4 mL / m² of water absorption capacity ２ 10mL / m or more ２ A set of aqueous ink and reaction solution used in an inkjet recording method for recording an image on a recording medium, wherein the aqueous ink and reaction solution are applied to a unit area of ​​the recording medium in a single relative scan between an inkjet ejection head and the recording medium, The inkjet recording method includes a reaction solution application step of applying the reaction solution to the recording medium, and an ink application step of applying the aqueous ink to the recording medium such that it overlaps with at least a portion of the area on the recording medium to which the reaction solution is applied. The aforementioned aqueous ink contains a pigment, A set of aqueous ink and reaction solution, characterized in that the reaction solution contains a cationic resin having the structure of a quaternary ammonium salt, and the surface tension of the liquid obtained by replacing the surfactant in the reaction solution with water at 25°C is 60 mN / m or more.

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