Inkjet recording method, inkjet recording apparatus, and ink set

Abstract

To provide an inkjet recording method capable of recording a high quality image suppressed in generation of bleeding and irregularity when recording on a hardly- or non-absorptive recording medium by one pass.SOLUTION: There is provided an inkjet recording method of respectively discharging any of a clear ink, a reaction liquid, and a pigment ink of an aqueous liquid composition from a recording head to apply onto a recording medium so as to record an image. Application of each liquid composition to a unit region is done by one relative scanning of the recording head and the recording medium. The clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reagent, and the pigment ink contains a pigment. The inkjet recording method includes: a clear ink-applying process of applying the clear ink onto the recording medium; a drying process of drying the clear ink applied onto the recording medium; a reaction liquid-applying process of applying the reaction liquid onto the recording medium; and a pigment ink-applying process of applying the pigment ink onto the recording medium, in this order.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Inkjet recording methods are increasingly using not only ink-absorbent recording media such as plain paper and inkjet glossy paper, but also poorly absorbent or non-absorbent recording media with low ink absorption. Examples of poorly absorbent or non-absorbent recording media include coated recording media such as printing paper and art paper, and films and sheets made of resin materials such as plastic. The use of aqueous pigment inks is becoming more common due to environmental and safety considerations. Studies have been conducted to stabilize image quality when recording by ejecting aqueous pigment inks onto non-absorbent recording media. When recording images by ejecting aqueous pigment inks onto non-absorbent recording media, ink droplets that adhere to the recording media rarely penetrate into the recording media. As a result, adjacent ink droplets may coalesce, resulting in unevenness or bleeding. Various countermeasures have been investigated. Patent Document 1 discusses the use of a reaction liquid containing a polyvalent metal salt, a reactant that aggregates aqueous ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-134853 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors conducted a study using the aqueous ink and reaction liquid described in Patent Document 1. In recent years, in order to produce a large number of printed materials in a short period of time, there has been an increasing demand for recording methods using a line-type recording head (line head) in which ejection ports are provided across the entire width of the recording medium. The present inventors conducted a study on recording an image using the aqueous ink and reaction liquid using a line head. As a result, they found that when the aqueous ink composition and reaction liquid described in Patent Document 1 are ejected from a line head onto a non-absorbent recording medium to perform recording, unevenness and bleeding of the image may occur.

[0005] Therefore, an object of the present invention is to provide an inkjet recording method, an inkjet recording apparatus, and an ink set that are capable of recording high-quality images with reduced bleeding and unevenness when recording in one pass on a poorly to non-absorbent recording medium. [Means for solving the problem]

[0006] The above object can be achieved by the following invention: That is, the inkjet recording method according to the present invention is an inkjet recording method in which a clear ink, a reaction liquid, and an ink, all of which are aqueous liquid compositions, are ejected from a recording head and applied to a recording medium so that at least a portion of the areas to which the clear ink, the reaction liquid, and the ink are applied overlap each other, thereby recording an image, 1 / 2 Water absorption up to 10mL / m 2the clear ink, the reaction liquid, and the ink are applied to a unit area of ​​the recording medium in a single relative scan of the recording head and the recording medium, the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the ink, and the ink contains a pigment, and the method comprises, in this order: a clear ink application step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid application step of applying the reaction liquid to the recording medium; and an ink application step of applying the ink to the recording medium. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an inkjet recording method, an inkjet recording apparatus, and an ink set that can record high-quality images with reduced unevenness and bleeding when recording in one pass on a poorly to non-absorbent recording medium. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus of the present invention. [Figure 2] FIG. 1 is a perspective view illustrating an example of a liquid deposition device. [Figure 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. [Figure 5] FIG. 10 is a schematic diagram showing another example of the heating unit. [Figure 6] FIG. 10 is a schematic diagram showing another example of the fixing unit. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in further detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the liquid composition (clear ink, reaction liquid, pigment ink) dissociated into ions, but for convenience, it will be expressed as "containing a salt." In addition, aqueous liquid compositions (ink, reaction liquid) for inkjet printing may be simply referred to as "liquid composition," "ink (clear ink or pigment ink containing no colorant)," or "reaction liquid." In addition, when there is no need to distinguish between "clear ink" and "pigment ink," they may be collectively referred to as "ink." Unless otherwise specified, physical property values ​​are values ​​at room temperature (25°C) and normal pressure (1 atmosphere). When "(meth)acrylic acid" or "(meth)acrylate" is used, it means "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

[0010] The present inventors have investigated the causes of unevenness and bleeding, resulting in a decrease in image quality, when the ink and reaction liquid described in Patent Document 1 are ejected from a line head onto a poorly to non-absorbent recording medium and recording is performed in a "single pass." In one-pass recording, the liquid composition is applied to a unit area of ​​the recording medium by a single relative scan of the line head and the recording medium, and the unit area can be set as any area, such as "one pixel," corresponding to the resolution of the recording head.

[0011] Since poorly to non-absorbent recording media hardly absorb liquid compositions, when ink or reaction liquid adheres to the surface of the recording medium, the droplets remain on the surface for a relatively long period of time without being absorbed by the recording medium. As a result of studies by the present inventors, it was found that the longer the time between when the reaction liquid adheres to the recording medium and when the ink adheres to the recording medium, the more likely it is that unevenness will occur in the image. This is thought to be because the reaction liquid is repelled and moves on the surface of the recording medium, so that the ink does not adhere to the position where it overlaps with the reaction liquid, and ink droplets that have not undergone aggregation due to the reaction liquid come into contact with each other, causing unevenness.

[0012] It was also found that image bleeding occurs at the edges of images and in boundary regions of images printed with multiple pigment inks. When multiple pigment inks are applied to a recording medium after a reaction liquid has been applied to the recording medium, the reaction liquid is attracted to the pigment ink that was applied first, resulting in a state in which no reaction liquid is present at the adhesion position of the pigment ink that was applied later. It is thought that bleeding occurs because the pigment ink that was applied later does not come into contact with the reaction liquid and does not sufficiently aggregate.

[0013] As described above, both image unevenness and bleeding can be said to be problems that occur when single-pass printing is performed because the reaction liquid is not present at the intended position on the printing medium. As a result of studies by the present inventors, when multi-pass printing is performed, it is possible to adjust the time from when the reaction liquid is ejected onto the printing medium until the ink is ejected to be shorter, and therefore the problems of image unevenness and bleeding that occur in single-pass printing are less likely to occur.

[0014] In light of the above phenomenon, the present inventors investigated a method for suppressing image unevenness and bleeding when applying a reaction liquid and a pigment ink in that order to a poorly to non-absorbent recording medium and recording an image. As a result, they found that image unevenness and bleeding can be suppressed by the configuration of the present invention, in which each liquid composition is applied in the following order. First, a clear ink containing a resin but no colorant is applied in advance so as to overlap at least a portion of the area where the reaction liquid is applied. Thereafter, a drying process is performed to dry at least a portion of the liquid components of the clear ink, and then the reaction liquid is applied so as to overlap at least a portion of the area where the clear ink is applied. Next, a pigment ink is applied so as to overlap at least a portion of the area where the clear ink or reaction liquid is applied. The clear ink may contain a reactant such as a resin or a polyvalent metal salt that reacts with the pigment ink.

[0015] The inventors speculate as follows about the reason why applying each liquid composition to a recording medium in the above-mentioned order can suppress image unevenness and bleeding. First, by drying at least a portion of the liquid components of the clear ink, the viscosity of the clear ink increases, making it less likely to move on the recording medium and fixing the application position of the clear ink. After achieving this state, by applying a reaction liquid to at least a portion of the area where the clear ink has been applied, an anchoring effect occurs at the interface where the clear ink and the reaction liquid come into contact, making it less likely to move on the recording medium. Then, by applying a pigment ink, aggregation of the pigment ink by the reaction liquid is promoted.

[0016] If the area on the recording medium where the reaction liquid is applied does not overlap with the area where the clear ink is applied, the reaction liquid will move on the recording medium before the pigment ink is applied to the recording medium, preventing the pigment ink from coming into contact with the reaction liquid, which will prevent the pigment ink from coagulating, resulting in unevenness and bleeding in the image.

[0017] Even if the pigment ink is applied to the recording medium so that it overlaps only the clear ink without overlapping with the reaction liquid, unevenness and bleeding of the image can be suppressed. This is because the anchor effect at the interface where the clear ink and the pigment ink come into contact can suppress the movement and coalescence of ink droplets. However, because aggregation of the pigment ink can more effectively suppress unevenness and bleeding of the image, it is more preferable to apply the pigment ink so that it overlaps not only the clear ink but also the reaction liquid.

[0018] <Inkjet recording method, inkjet recording apparatus, and ink set> The inkjet recording method of the present invention (hereinafter also referred to simply as "recording method") has the following configuration: A clear ink, a reaction liquid, and a pigment ink, all of which are aqueous liquid compositions, are ejected from a recording head and applied to a recording medium so that at least a portion of the areas to which the clear ink, reaction liquid, and pigment ink are applied overlap each other, thereby recording an image. 1 / 2The water absorption rate is 10.0 mL / m 2 The clear ink, reaction liquid, and pigment ink are applied to a unit area of ​​the recording medium in a single relative scan of the recording head and recording medium. The clear ink contains a resin. The reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink. The pigment ink contains a pigment. The method includes, in this order, a clear ink application step of applying the clear ink to the recording medium, a drying step of drying the clear ink applied to the recording medium, a reaction liquid application step of applying the reaction liquid to the recording medium, and a pigment ink application step of applying the pigment ink to the recording medium. The inkjet recording apparatus of the present invention (hereinafter also simply referred to as "recording apparatus") is an inkjet recording apparatus used in the above-mentioned inkjet recording method. The ink set of the present invention (hereinafter also simply referred to as "ink set") is an ink set used in the above-mentioned inkjet recording method.

[0019] (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.

[0020] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured with 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, a liquid applying unit 1200 applies various liquids to a recording medium 1100 transported from a paper feeder 1400 by a transport member 1300. In the heating unit 2000, a heating unit 2100 heats the liquid applied to the recording medium 1100, evaporating volatile components such as water in the liquid and drying it. In the fixing unit 3000, a fixing member 3100 is brought into contact with and heated in the area of ​​the recording medium 1100 where the liquid has been applied, thereby promoting fixing of the image to the recording medium 1100. The recording medium 1100 is then cooled by a cooling member 4100 in a cooling unit 4000. When an image is to be recorded on the back side after the front side (recording surface), the recording medium 1100 is first inverted by the inverting device 5100 of the inverting unit 5000. Next, an image is recorded on the back side in the same manner as on the front side, and then the recording medium is transported by the transport member 6100 of the paper discharge unit 6000 and stacked and stored in the recording medium storage unit 6200.

[0021] [Recording Department] The recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a clear ink applying device 1201, a reaction liquid applying device 1202, and a pigment ink applying device 1203.

[0022] The clear ink applicator 1201 is disposed upstream of the reaction liquid applicator 1202 and the pigment ink applicator 1203 in the transport direction (X direction) of a transport member 1300 described below.

[0023] The reaction liquid deposition device 1202 shown in FIG. 1 is an example of a unit using an inkjet type ejection head. Alternatively, the reaction liquid deposition device may be configured using a gravure coater, offset coater, die coater, blade coater, or the like. The deposition of the reaction liquid by the reaction liquid deposition device 1202 must be performed after the deposition of the clear ink and before the deposition of the pigment ink. As the clear ink deposition device 1201 and the pigment ink deposition device 1203, inkjet type ejection heads (recording heads) are used. The ejection method of the ejection head serving as the liquid deposition device 1200 can be exemplified by a method in which film boiling is caused in the liquid by an electrothermal converter to form bubbles, and a method in which the liquid is ejected by an electromechanical converter.

[0024] The liquid deposition device 1200 is a line head extending in the Y direction, and has ejection ports arranged in a range that covers the image recording area of ​​the widest usable recording medium. The ejection head has an ejection port surface 1208 (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 several millimeters.

[0025] A plurality of pigment ink applicators 1203 may be provided to apply pigment ink of each color to the recording medium 1100. For example, when printing images of each color using yellow ink, magenta ink, cyan ink, and black ink, four pigment ink applicators 1203 for ejecting the above four types of pigment ink are arranged side by side in the X direction.

[0026] Fig. 2 is a perspective view showing an example of a liquid deposition apparatus. The liquid deposition apparatus 1200 shown in Fig. 2 is a line head, and has a plurality of ejection element substrates 1204, each having an ejection port array, arranged in a straight line. The ejection element substrate 1204 has a plurality of ejection port arrays arranged thereon.

[0027] FIG. 3 is a cross-sectional perspective view showing an example of an ejection element substrate. The ejection element substrate 1204 shown in FIG. 3 includes an ejection port forming member 1207 having ejection ports 1205 formed therein, and a substrate 1206 on which ejection elements (not shown) are disposed. The ejection port forming member 1207 and the substrate 1206 are stacked together to form a first flow path 1209 and a second flow path 1210 through which liquid flows. The first flow path 1209 is a region extending from an inlet 1213, through which liquid flows from an inlet channel 1211, to a portion between the ejection port 1205 and the ejection element (liquid chamber 1508 in FIG. 4). The second flow path 1210 is a region extending from a portion between the ejection port 1205 and the ejection element (liquid chamber 1508 in FIG. 4) to an outlet 1214 through which liquid flows out to an outlet channel 1212. For example, by creating a pressure difference between the inlet 1213 and the outlet 1214, such as a high-pressure inlet 1213 and a low-pressure outlet 1214, liquid can be made to flow from the high-pressure side to the low-pressure side (in the direction of the arrow in FIG. 3). The liquid that has passed through the inlet 1211 and the inlet 1213 enters the first flow path 1209. Then, the liquid that has passed through the portion between the ejection port 1205 and the ejection element (liquid chamber 1508 in FIG. 4) flows through the second flow path 1210 and the outlet 1214 to the outlet 1212.

[0028] [Supply system] FIG. 4 is a schematic diagram showing an example of a supply system for each liquid composition (clear ink, reaction liquid, and pigment 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, which is connected to a main tank 1504 serving as a liquid storage unit, has an air vent (not shown) and is capable of discharging 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 an amount of liquid corresponding to the consumed amount from the main tank 1504 to the sub-tank 1503.

[0029] 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 has been discharged 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 capacity 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 1204 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.

[0030] The negative pressure control unit 1509 has two pressure adjustment mechanisms, each set to a different control pressure. The pressure adjustment mechanism (high pressure side) 1510 and the pressure adjustment mechanism (low pressure side) 1511 are connected to a common inlet channel 1514 and a common outlet channel 1515 in the ejection element substrate 1204, respectively, via a supply unit 1513 provided with a filter 1512 that removes foreign matter from the liquid. The ejection element substrate 1204 is provided with the common inlet channel 1514, the common outlet channel 1515, and inlet channels 1211 and outlet channels 1212 that communicate with a liquid chamber 1508, which is a portion between the ejection port 1205 and the ejection element (not shown). Because the inlet channel 1211 and the outlet channel 1212 communicate with the common inlet channel 1514 and the common outlet channel 1515, respectively, a flow (indicated by an arrow in FIG. 4 ) occurs in which part of the liquid flows from the common inlet channel 1514 through the interior of the liquid chamber 1508 to the common outlet 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 1209 flows to the second flow path 1210 via the gap between the ejection port 1205 and the ejection element.

[0031] 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 1211 and the outflow channel 1212. As a result, a pressure difference also occurs between an inlet 1213 (FIG. 3) communicating with the inflow channel 1211 and an outlet 1214 (FIG. 3) communicating with the outflow channel 1212. When liquid is caused to flow by the pressure difference between the inlet 1213 and the outlet 1214, the flow velocity (mm / s) of the liquid is preferably controlled to be 0.1 mm / s or more and 10.0 mm / s or less.

[0032] [Transport system] As shown in FIG. 1, the recording unit 1000 includes a liquid deposition device 1200 and a transport member 1300 that transports the recording medium 1100. The liquid deposition device 1200 deposits clear ink, reaction liquid, and pigment ink at desired positions on the recording medium 1100 transported by the transport member 1300. Each liquid deposition device receives image signals from the recording data and deposits the required clear ink, reaction liquid, and pigment ink at each position. While FIG. 1 shows the transport member 1300 in the form of a transport belt, a spur, transport drum, or other device capable of transporting the recording medium 1100 may also be used. To improve transport accuracy, the transport member 1300 may be configured to hold the recording medium 1100 in place. Specifically, the transport member 1300 may be provided with holes that allow suction from the rear side to fix the recording medium 1100, or the transport member 1300 may be formed of an appropriate material and electrostatically adsorbed to fix the recording medium 1100.

[0033] [Drying section] As shown in FIG. 1, the recording apparatus 100 includes a drying unit 1600 between the clear ink applicator 1201 and the reaction liquid applicator 1202. The drying unit 1600 dries the liquid component of the clear ink applied by the clear ink applicator 1201. The drying unit 1600 can be configured to blow air toward the recording surface of the recording medium 1100, an infrared (IR) heater, or a platen heater or belt heater that heats the recording medium 1100 by contacting the back surface of the recording medium 1100. If the drying unit 1600 is an air blowing unit, it may blow room temperature air toward the recording medium 1100 to dry the liquid component of the clear ink, or it may blow heated air. Alternatively, the distance and transport time between the clear ink applicator 1201 and the reaction liquid applicator 1202 may be set so that a certain amount of the liquid component of the clear ink is dried, without drying by a drying unit. For example, the time from when the clear ink is applied to a specific position on the recording medium until the reaction liquid is applied can be set to 10 seconds or more and 50 seconds or less.

[0034] The drying time may be adjusted as appropriate. If the drying time is too short, the liquid components will not dry sufficiently, and the effect of fixing the position of the clear ink will not be realized, while if the drying time is too long, it may lead to deformation of the recording medium. In the case of clear ink containing a resin, if it is heated for a long time at a temperature higher than the glass transition temperature of the resin particles, the unevenness caused by the resin particles may be smoothed out, reducing the anchoring effect on the reaction liquid. Therefore, it is preferable to dry the clear ink to the extent that the uneven shape of the resin particles remains. Methods for adjusting the degree of drying include lowering the heating temperature, blowing air without heating, or increasing the transport speed of the recording medium 1100 to shorten the drying time.

[0035] [Heating section] As shown in FIG. 1, the heating section 2000 is configured to include a heating device 2100 and a conveying member 2200. The recording medium 1100, onto which clear ink, reaction liquid, and pigment ink have been applied and an image has been recorded, is heated by the heating device 2100 while being conveyed by the conveying member 2200, thereby evaporating and drying the liquid components of the image. It is preferable to further include a drying step between the pigment ink application step and the fixing step, in which the recording medium onto which the pigment ink has been applied is heated in a non-contact manner to dry the pigment ink. By including such a drying step, deformation (cockling and curling) of the recording medium 1100 can be effectively suppressed.

[0036] The heating device 2100 may have any configuration as long as it can heat the recording medium 1100, and various conventionally known devices such as a hot air dryer or heater can be used. Among these, 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. Furthermore, if a mechanism for blowing hot air with a built-in fan is used to spray heated gas onto the recording medium 1100, drying efficiency can be easily improved.

[0037] The heating method may be from the side of the recording medium 1100 on which the clear ink, reaction liquid, and pigment ink are applied (recording surface (front side)), or from the back side, or from both sides. The conveying member 2200 may also be provided with a heating function. While FIG. 1 shows the conveying member 2200 using a conveying belt, a spur, conveying drum, or other device capable of conveying the recording medium 1100 may also be used. From the viewpoint of suppressing deformation of the recording medium 1100 due to heating, it is preferable to use a configuration in which the recording medium 1100 is conveyed while being tightly attached to the conveying member 2200 by blowing air from the heating unit 2000, or to provide a mechanism for fixing the recording medium to the conveying member 2200. Specifically, examples include a method in which holes are provided in the conveying member 2200 and the recording medium 1100 is fixed by suction from the back side, or a method in which the conveying member 2200 is formed of an appropriate material and the recording medium 1100 is fixed by electrostatic adsorption.

[0038] The heating temperature is preferably set so as to quickly evaporate the liquid components while avoiding excessive drying in order to prevent deformation of the recording medium 1100. The temperature of the drying means can be set so that the recording medium reaches a desired temperature, taking into account the conveyance speed and ambient 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. Furthermore, when the recording medium 1100 is heated by blowing heated gas, the air speed is preferably set to 1 m / s or higher and 100 m / s or lower. The temperature of the hot air or other air can be measured using a K-type thermocouple thermometer. A specific example of a measuring device is the "AD-5605H" (manufactured by A&D).

[0039] Fig. 5 is a schematic diagram showing another example of a heating section. Here, differences from the heating section shown in Fig. 1 and described above will be described. Heating section 2000 shown in Fig. 5 includes first heating device 2101, second heating device 2102, and first conveying member 2201 and second conveying member 2202 arranged opposite first heating device 2101 and second heating device 2102, respectively.

[0040] The first conveying member 2201 does not have a mechanism for suctioning and fixing the recording medium 1100. The recording medium 1100 is conveyed by pressing the recording medium 1100 against the first conveying member 2201 using warm air from the first heating device 2101. This allows the recording medium 1100 to be transferred accurately 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 deviations in conveyance due to slight differences in conveyance speed between the conveying member 1300 (FIG. 1) and the first conveying member 2201. On the other hand, the second conveying member 2202 uses a conveying belt with holes that allow gas to pass through, and conveys the recording medium 1100 while fixing it to the second conveying member 2202 using a suction mechanism (not shown).

[0041] Air knives 2300 are 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 knives 2300 prevents the leading edge of the transported recording medium 1100 from lifting up. This prevents 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), thereby preventing transport problems from occurring.

[0042] The first heating device 2101 and the second heating device 2102 can have the same configuration as the above-described heating device 2100. The temperatures of the first heating device 2101 and the second heating device 2102 and the wind speeds 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.

[0043] [Fixing section] As shown in FIG. 1 , the fixing unit 3000 is a contact-type heating and pressurizing mechanism having a fixing member 3100, such as an endless belt, as a fixing 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, thereby heating the clear ink, reaction liquid, and pigment ink applied to the recording medium 1100. This fixes an image to the recording medium 1100. After the image is recorded on the recording medium 1100, the liquid components of the clear ink, reaction liquid, and pigment ink permeate into the recording medium 1100 or evaporate as they pass through the heating unit 2000, and are then fixed in the fixing unit 3000, completing the image. Heating and pressurizing the recording medium 1100 sandwiched between the fixing member 3100 and the conveying member 3200 bring the image on the recording medium 1100 into close contact with the fixing member 3100, thereby fixing the image to the recording medium 1100. When a pigment ink containing resin particles and a pigment is used, the resin particles are softened and form a film mainly by heating in the fixing unit 3000 , and the color material can be bound onto the recording medium 1100 .

[0044] The fixing member 3100 can be heated by installing a heat source such as a halogen heater inside the roller that drives the fixing member 3100 (as a fixing belt). Another method involves installing a heat source such as an infrared heater in a location separate from the fixing member 3100. These methods may also be combined. If necessary, the conveying member 3200 may also be heated. The temperature of the fixing member 3100 can be set to a desired temperature on the surface of the recording medium, taking into account the conveying speed and ambient temperature. Specifically, the temperature of the fixing member 3100 is preferably set to between 50°C and 120°C, and more preferably between 60°C and 110°C. 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. An example of a radiation thermometer is the "Radiation Thermometer IT-545S" (manufactured by Horiba, Ltd.).

[0045] When the pigment ink contains resin particles, setting the temperature of the fixing member 3100 to a temperature equal to or higher than the glass transition temperature of the resin particles in the pigment ink softens the resin particles, facilitating film formation and improving the scratch resistance of the image. When the pigment 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 makes up the wax particles. This prevents the wax from melting and makes it easier for it to remain on the surface of the image, improving the scratch resistance of the image.

[0046] The nip pressure of the fixing member 3100 and the conveying member 3200, i.e., the pressure applied to the recording medium as it passes through the contact-type heating and pressurizing 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 pressurizing 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 second to 3.0 seconds.

[0047] FIG. 6 is a schematic diagram showing another example of a fixing unit. Here, differences from the fixing unit shown in FIG. 1 and described above are explained. The fixing unit 3000 shown in FIG. 6 is a contact-type heating and pressurizing mechanism including multiple fixing rollers 3101 and multiple conveying members 3201 arranged opposite these fixing rollers 3101. An image is fixed to the recording medium 1100 with pigmented ink applied thereto by passing between the fixing rollers 3101 and the conveying members 3201. The degree of image fixation to the recording medium can be adjusted by controlling the number of fixing rollers 3101 and the conveying members 3201, the nip time, temperature, pressure, etc. of the recording medium.

[0048] [Cooling section] The cooling unit 4000 is configured with a cooling member 4100 and a conveying member 4200 (FIG. 1). The cooling member 4000 cools the recording medium 1100, which has been heated to a high temperature after passing through the heating unit 2000 and the fixing unit 3000. The cooling member 4100 may have any configuration capable of cooling the recording medium 1100, and methods such as air cooling and water cooling can be used. Among these, blowing unheated gas is preferable from the standpoint of safety and energy efficiency. Furthermore, using a blowing mechanism with a built-in fan to spray gas onto the recording medium 1100 can easily improve cooling efficiency. The temperature of the cooling means can be set so that the image on the recording medium reaches the desired temperature, taking into account the conveyance speed and ambient temperature. Specifically, the temperature of the cooling means (such as an air blower) is preferably 20°C to 60°C, and more preferably 25°C to 50°C. When cooling by blowing gas, the air speed is preferably 1 m / s to 100 m / s. By setting such conditions, it is possible to prevent deformation of the recording medium 1100 loaded in the paper discharge unit 6000, which will be described later, and image sticking (blocking).

[0049] [Inverted part] When double-sided recording is performed, the recording medium 1100 is inverted using the inverting 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 then branched and transported, and is inverted by the inverting 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)).

[0050] [Paper output section] After image recording, the recording medium 1100 is stored in the paper discharge unit 6000 (FIG. 1). After single-sided or double-sided recording, the recording medium 1100 passes through the cooling unit 4000, is transported by a transport member 6100, and is finally stored in a stacked state in a recording medium storage unit 6200. Two or more recording medium storage units 6200 may be provided to store different recorded materials, etc.

[0051] <Recording Media> In the present invention, a recording medium that is poorly to non-absorbent is used. This recording medium is a recording medium that is hard to absorb liquids within 30 msec from the start of contact in the Bristow method described in JAPAN TAPPI Paper Pulp Test Method No. 51 "Liquid Absorbency Test Method for Paper and Paperboard." 1 / 2 Water absorption up to 10.0L / m 2 In the present invention, a recording medium that satisfies the above-mentioned condition of water absorption amount is defined as a "hardly to non-absorbent recording medium." Inkjet recording media (glossy paper, matte paper, etc.) having a coating layer (ink receiving layer) formed of inorganic particles, and plain paper having no coating layer, have a water absorption amount of 10.0 mL / m or more. 2 It is an "absorbent recording medium" that exceeds

[0052] As the poorly absorbent recording medium, a recording medium such as printing paper or art paper having a thinner coating layer than the above-mentioned recording medium for inkjet recording can be used. Also, as the non-absorbent recording medium, a plastic film can be used; a recording medium in which a plastic film is adhered to the recording surface of a substrate. The basis weight (g / m) of the recording medium 1100 can be 2 ) is 30g / m 2 More than 500g / m 2 Preferably, it is 50 g / m or less. 2 More than 450g / m 2 It is even more preferable that:

[0053] <Clear ink> The clear ink used in the recording method of the present invention is a liquid composition prepared separately from the reaction liquid and pigment ink described below, and is a colorless ink that does not contain coloring materials such as dyes or pigments. Each component used in the clear ink will be described in detail below.

[0054] The clear ink may contain a reactant that can be contained in the reaction liquid. When a clear ink containing a reactant is used, it is preferable to use a resin that can coexist with the reactant in the clear ink, taking into account the ejection properties from the recording head. Examples of such resins include those that are weakly reactive with the reactant or that do not react with the reactant. For example, when the clear ink contains a reactant such as a polyvalent metal salt, it is preferable to use a resin that does not have an ionic group or a cationic resin as the resin. Furthermore, the clear ink can also contain a cationic resin as a resin that also functions as a reactant. In this case, the resin that is an essential component of the clear ink may be only a cationic resin.

[0055] [resin] The clear ink contains a resin. Examples of the resin include the same resins that can be contained in pigment inks, which will be described later. The resin contained in the clear ink is preferably resin particles. By using resin particles, when the clear ink is applied to a recording medium, unevenness resulting from the resin particles is likely to occur on the surface of the ink droplets of the clear ink. When the reaction liquid is applied in this state, the anchoring effect of the reaction liquid by the clear ink is enhanced, and unevenness and bleeding of the image can be more effectively suppressed.

[0056] The resin content (% by mass) in the clear ink is preferably 5.00% by mass or more, and more preferably 10.00% by mass or more, based on the total mass of the ink. If the resin content is less than 5.00% by mass, the difference in unevenness caused by the clear ink tends to be small, the anchoring effect of the reaction liquid is reduced, and the effect of suppressing image unevenness and bleeding may not be sufficiently achieved. The resin content (% by mass) in the clear ink is preferably 25.00% by mass or less, and more preferably 20.00% by mass or less, based on the total mass of the ink.

[0057] [Aqueous medium] The clear ink is an aqueous liquid composition containing at least water as the aqueous medium. Examples of aqueous media used in the clear ink include those similar to those that can be contained in the pigment ink described below. Like the reaction liquid and pigment described below, the clear ink also preferably contains a water-soluble organic solvent with a boiling point of less than 260°C. The aqueous medium used in the clear ink can contain the water-soluble organic solvent described below that can be contained in the pigment ink. The content (mass %) of the water-soluble organic solvent in the clear ink is preferably 1.00% by mass or more and 45.00% by mass or less, based on the total mass of the ink. Furthermore, the content (mass %) of water in the clear ink is preferably 50.00% by mass or more and 95.00% by mass or less, based on the total mass of the ink.

[0058] [Other ingredients] The clear ink may contain other components as needed, such as the same components that can be contained in pigment inks, which will be described later, and reactants that can be contained in reaction liquids.

[0059] [Clear ink properties] The clear ink is a water-based clear ink used in inkjet printing. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the clear ink at 25°C is preferably 20.0 mN / m or more and 60.0 mN / m or less. In particular, the surface tension of the clear ink is preferably 20.0 mN / m or more and 35.0 mN / m or less. Many low-to-non-absorbent recording media have low surface energy. When using such recording media, the low surface tension of the clear ink allows the clear ink to quickly wet and spread on the recording medium. This increases the area of ​​overlap with the next applied reaction liquid, thereby more effectively suppressing image unevenness and bleeding. The surface tension of the clear ink is the static surface tension measured using a surface tensiometer using the plate method. Furthermore, the viscosity of the clear ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the clear ink 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.

[0060] <Reaction solution> The recording method of the present invention includes a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the pigment ink to a recording medium. Hereinafter, each component used in the reaction liquid will be described in detail.

[0061] [Reactant] The reaction liquid reacts with the pigment ink upon contact with it, causing the components in the pigment ink (components with 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 with anionic groups in the pigment ink when the pigment ink and the reactant come into contact on the recording medium, thereby promoting the aggregation of the pigment ink. Examples of the reactant include cationic components such as polyvalent metal ions and cationic resins, and organic acids. One reactant may be used alone, or two or more may be used in combination.

[0062] Examples of polyvalent metal ions that constitute polyvalent metal salts include Ca. 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Sr 2+ , Ba 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+ Examples of the trivalent metal ions include trivalent metal ions such as Cl. To add polyvalent metal ions to the reaction solution, a water-soluble polyvalent metal salt (which may be a hydrate) formed by combining a polyvalent metal ion with an anion can be used. Examples of the anion 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 - , CH3CH(OH)COO - , C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 -Examples of organic anions include: magnesium sulfate, magnesium sulfate, and the like. Among polyvalent metal salts, magnesium sulfate is preferred because it has excellent aggregating properties for pigments and resin particles, is highly soluble in the liquid components constituting the reaction solution, and can improve the scratch resistance of the recorded image. When a polyvalent metal ion is used as a reactant, the content (mass %) of the polyvalent metal salt in the reaction solution is preferably 1.00 mass % or more and 20.00 mass % or less, and more preferably 1.00 mass % or more and 10.00 mass % or less, based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass %) of the polyvalent metal salt" in the reaction solution means the "content (mass %) of the anhydrous polyvalent metal salt," excluding water as the hydrate.

[0063] The organic acid-containing reaction solution has buffering properties in the acidic range (less than pH 7.0, preferably pH 2.0 to 5.0), thereby efficiently converting anionic groups present in the pigment ink into the acid form and causing them to aggregate. Examples of organic acids include monocarboxylic acids and salts thereof, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrolecarboxylic acid, furancarboxylic acid, picolinic acid, nicotinic acid, thiophenecarboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and 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 thereof, such as citric acid and trimellitic acid; and tetracarboxylic acids and salts thereof, such as pyromellitic acid. When an organic acid is used as a 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.

[0064] Examples of cationic resins include resins having a primary, secondary, or tertiary amine structure and resins having a quaternary ammonium salt structure. Specific examples include resins having structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. To enhance solubility in the reaction solution, the cationic resin can be used in combination with an acidic compound or the cationic resin can be subjected to a quaternization treatment. When a cationic resin is used as a reactant, the content (mass %) of the cationic resin in the reaction solution is preferably 0.10% by mass or more and 10.00% by mass or less, based on the total mass of the reaction solution.

[0065] Among the reactants described above, it is preferable to use a polyvalent metal salt, and it is particularly preferable to use magnesium sulfate. This is because, among reactants, polyvalent metal salts have a strong coagulating force for pigments and can effectively suppress bleeding of images. In particular, magnesium sulfate can efficiently coagulate pigments and resin particles that can be added to the ink, and has excellent solubility in the liquid components that make up the reaction liquid, making it effective in suppressing bleeding of images recorded with pigment ink.

[0066] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as the aqueous medium. Examples of aqueous media used in the reaction liquid include those similar to those that can be contained in pigment inks, as described below. The aqueous medium used in the reaction liquid can contain the water-soluble organic solvents that can be contained in pigment inks, as described below. The content (mass %) of the water-soluble organic solvent in the reaction liquid is preferably 1.00% by mass or more and 45.00% by mass or less, based on the total mass of the reaction liquid. The water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound, as described below. The content (mass %) of the water-soluble hydrocarbon compound in the reaction liquid is preferably 1.00% by mass or more and 20.00% by mass or less, based on the total mass of the reaction liquid. Furthermore, the content (mass %) of water in the reaction liquid is preferably 50.00% by mass or more and 95.00% by mass or less, based on the total mass of the reaction liquid.

[0067] The reaction liquid preferably contains a water-soluble organic solvent having a boiling point of less than 260°C. The boiling point of the water-soluble organic solvent is measured at 25°C and 1 atmospheric pressure. Water-soluble organic solvents having a boiling point of less than 260°C evaporate easily, so that the amount of liquid components remaining in the image layer formed from the pigment ink can be reduced, thereby further improving abrasion resistance. Specific examples of water-soluble organic solvents having a boiling point of less than 260°C include ethylene glycol (197°C), 1,2-propanediol (188°C), 1,3-propanediol (210°C), 1,2-butanediol (193°C), 1,3-butanediol (208°C), 1,4-butanediol (230°C), 1,3-butanediol (182°C), 1,2-pentanediol (206°C), 1,2-hexanediol (223°C), and 2-methyl-1,3-propanediol. Examples of suitable solvents include diol (214°C), diethylene glycol monomethyl ether (194°C), diethylene glycol monoethyl ether (202°C), diethylene glycol monoisopropyl ether (207°C), diethylene glycol monoisobutyl ether (229°C), diethylene glycol monobutyl ether (230°C), 1,5-pentanediol (242°C), diethylene glycol (245°C), and 2-pyrrolidone (245°C).

[0068] When a water-soluble organic solvent having a boiling point of 260°C or higher is contained in the reaction liquid, it is preferable to reduce its content, as described above, because, unlike water-soluble organic solvents having a boiling point of less than 260°C, the water-soluble organic solvent is less likely to evaporate. Specifically, the content (mass%) of the water-soluble organic solvent having a boiling point of 260°C or higher is preferably 1.00 mass% or less, based on the total mass of the reaction liquid. Of these, 0.50 mass% or less is more preferable, and 0.10 mass% or less is particularly preferable. The content of the water-soluble organic solvent having a boiling point of 260°C or higher may be 0.00 mass%. In other words, it is preferable that the reaction liquid does not substantially contain a water-soluble organic solvent having a boiling point of 260°C or higher.

[0069] [Other ingredients] The reaction liquid may contain other components as needed, including the same components as those that can be contained in the pigment ink, which will be described later.

[0070] [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 its physical properties. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20.0 mN / m or more and 60.0 mN / m or less. The surface tension is the static surface tension determined by the plate method. Furthermore, the viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. 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.

[0071] <Pigment ink> The ink used in the recording method of the present invention is a pigment ink containing a pigment. The pigment ink may contain one or more types of pigment. Each component used in the pigment ink will be described in detail below.

[0072] [Colorant] The pigment content (mass %) in the pigment ink is preferably 0.50% to 15.00% by mass, and more preferably 1.00% to 10.00% by mass, based on the total mass of the ink.

[0073] 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. One type of pigment may be used alone, or two or more types may be used in combination.

[0074] As a pigment dispersion method, resin-dispersed pigments using a resin as a dispersant, and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface can be used. Also usable are resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microencapsulated pigments in which the pigment particle surface is coated with a resin or the like. It is also possible to use a combination of these pigments with different dispersion methods. In particular, it is preferable to use resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the pigment particle surface, rather than resin-bonded pigments or microencapsulated pigments.

[0075] As a resin dispersant for dispersing a pigment in an aqueous medium, it is preferable to use one that can disperse the pigment in an aqueous medium by the action of anionic groups. As the resin dispersant, a resin having anionic groups can be used, and it is preferable to use a resin such as those described below, especially a water-soluble resin. The content (mass %) of the pigment in the pigment ink is preferably 0.3 to 10.0 times the content (mass %) of the resin dispersant.

[0076] Self-dispersing pigments can be used in which an anionic group such as a carboxylic acid group, sulfonic acid group, or phosphonic acid group is bonded to the surface of the pigment particle directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and if it is a salt type, it may be either partially dissociated or completely dissociated. When the anionic group is a salt type, examples of the cation that serves as the counter ion include alkali metal cations, ammonium, and organic ammonium. 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 and naphthylene; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Furthermore, combinations of these groups may also be used.

[0077] [resin] The pigment ink may contain a resin. By using a pigment ink containing a resin, it is possible to record an image with improved scratch resistance. Resins can be added to the pigment ink (i) to stabilize the dispersion state of the pigment, i.e., as a resin dispersant or its auxiliary. Resins can also be added to the pigment ink (ii) to improve various properties of the recorded image.

[0078] The content (mass %) of the resin in the pigment ink is preferably 0.10% by mass or more and 20.00% by mass or less, and more preferably 0.50% by mass or more and 15.00% by mass or less, based on the total mass of the ink. Examples of the resin form 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. One type of resin may be used alone, or two or more types may be used in combination.

[0079] [Resin Composition] Examples of the resin include acrylic resins, urethane resins, olefin resins, etc. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are more preferred.

[0080] The acrylic resin is preferably one having a hydrophilic unit and a hydrophobic unit as constituent units. Among these, 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-based 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 a styrene and an α-methylstyrene monomer is preferred. These resins are likely to interact with pigments, and can therefore be suitably used as resin dispersants for dispersing pigments.

[0081] 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 hydrophilic monomers 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 hydrophobic monomers 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.

[0082] The urethane resin can be obtained by, for example, reacting a polyisocyanate with a polyol. Alternatively, a chain extender may be further added to the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0083] [Resin properties] As used herein, the term "water-soluble resin" means that when the resin is neutralized with an alkali equivalent to its acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether a resin is water-soluble or not can be determined according to the following method. First, a liquid (resin solids content: 10% by mass) containing the 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 (by volume) with pure water to prepare a sample solution. When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having the particle size are measured, the resin can be determined to be water-soluble. The measurement conditions can be, for example, Set Zero: 30 seconds, measurement count: 3, and measurement time: 180 seconds. Furthermore, a particle size distribution measuring device such as a particle size analyzer using dynamic light scattering (e.g., the "UPA-EX150" product, manufactured by Nikkiso) can be used. Of course, the particle size distribution measuring device and measuring conditions to be used are not limited to those described above.

[0084] The water-soluble resin preferably has an acid value of 100 mgKOH / g or more and 250 mgKOH / g or less, and a weight-average molecular weight of 3,000 or more and 15,000 or less.

[0085] 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, 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 resin particles is the diameter of the particles that is 50% when integrated from the small particle diameter side based on the total volume of the measured particles in a particle diameter integration curve. The volume-based cumulative 50% particle diameter of 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, 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 colorant.

[0086] The resin contained in the pigment ink is preferably resin particles. When resin particles are contained in the pigment ink, the pigment and resin particles form large aggregates when the pigment ink comes into contact with the reaction liquid, making it possible to more effectively suppress unevenness and bleeding in the image.

[0087] [Aqueous medium] The pigment ink used in the recording method of the present invention is an aqueous ink containing at least water as the aqueous medium. The pigment ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass %) in the pigment ink is preferably 50.00% to 95.00% by mass, based on the total mass of the ink. Furthermore, the water-soluble organic solvent content (mass %) in the pigment ink is preferably 2.00% to 40.00% by mass, based on the total mass of the ink. As the water-soluble organic solvent, any of those usable in 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. Like the reaction liquid, the pigment ink preferably contains a water-soluble organic solvent with a boiling point below 260°C.

[0088] [Other ingredients] The pigment ink may contain other components as needed. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and antireducing agents. However, it is preferable that the pigment ink does not contain the reactants contained in the clear ink or reaction liquid.

[0089] [Physical properties of pigment ink] The pigment ink is a water-based pigment ink used in inkjet printing. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the pigment ink at 25°C is preferably 20.0 mN / m or more and 60.0 mN / m or less. Furthermore, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less. [Example]

[0090] 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 as long as the gist of the invention is not exceeded. The terms "parts" and "%" used to describe the amounts of components are by mass unless otherwise specified.

[0091] <Preparation of resin particles> (Resin particles 1) A four-neck flask equipped with a stirrer, reflux condenser, and nitrogen gas inlet tube was charged with 78.8 parts of ion-exchanged water and 0.2 parts of potassium persulfate and mixed. An emulsion was prepared by mixing 15.7 parts of ethyl methacrylate, 9.1 parts of 2-(dimethylamino)ethyl methacrylate, and 0.5 parts of a reactive surfactant (Adeka Soap ER-20, manufactured by Adeka). Under a nitrogen atmosphere, the emulsion was added dropwise to the four-neck flask over 1 hour, and polymerization was carried out for 2 hours at 80°C with stirring. The resin (solids) content was adjusted to prepare an aqueous dispersion of resin particles 1 with a resin particle (solids) content of 40.0% and a glass transition temperature of 85°C.

[0092] (Resin particles 2) A four-neck flask equipped with a stirrer, reflux condenser, and nitrogen gas inlet tube was charged with 81.8 parts of ion-exchanged water and 0.2 parts of potassium persulfate and mixed. An emulsion was prepared by mixing 16.1 parts of butyl methacrylate, 1.6 parts of NOF Corp.'s "Blenmer PME1000" (product name), and 0.3 parts of a reactive surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd.'s "Aqualon KH-05"). Under a nitrogen atmosphere, the emulsion was added dropwise to the four-neck flask over 1 hour and allowed to polymerize for 2 hours with 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 adjust the resin particle (solids) content to prepare an aqueous dispersion of resin particles 2 with a resin content of 40.0% and a glass transition temperature of 70°C.

[0093] (Resin particles 3) A four-neck flask equipped with a stirrer, reflux condenser, and nitrogen gas inlet tube was charged with 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate and mixed. An emulsion was prepared by mixing 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "Aqualon KH-05" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Under a nitrogen atmosphere, the emulsion was added dropwise to the four-neck flask over 1 hour and allowed to polymerize for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide equimolar to the acid value of the resin particles were added to adjust the resin particle (solids) content to prepare an aqueous dispersion of resin particles 3 with a resin content of 40.0% and a glass transition temperature of 60°C.

[0094] <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 its acid value, and then an appropriate amount of pure water was added to prepare an aqueous solution of Resin 1 with a resin (solids) content of 20.0%. A mixture was obtained by mixing 15.0 parts of pigment (carbon black), 22.5 parts of the Resin 1 aqueous solution, and 62.5 parts of pure water. The resulting mixture and 200 parts of 0.3 mm diameter zirconia beads were placed in a batch-type vertical sand mill (Imex) and dispersed for 5 hours with water cooling. After centrifuging to remove coarse particles, the mixture was pressure-filtered through a 3.0 μm pore-size cellulose acetate filter (Advantec) to prepare Pigment Dispersion 1 with a pigment content of 15.0% and a resin dispersant (Resin 1) content of 4.5%.

[0095] (Pigment dispersion 2) Pigment Dispersion Liquid 2 was prepared using the same procedure as for Pigment Dispersion Liquid 1 described above, except that the pigment was changed to CI Pigment Blue 15:3. The pigment content was 15.0% and the resin dispersant (Resin 1) content was 4.5%.

[0096] <Preparation of clear ink> Each clear ink was prepared by mixing the components (unit: %) shown in the upper rows of Tables 1 and 2, thoroughly stirring, and then filtering under pressure using a 3.0 μm pore size filter (product name "Cellulose Acetate Filter", manufactured by Advantec). Details of the components in Tables 1 and 2 are as follows: Product name: "Sharol DC902P", manufactured by Daiichi Kogyo Seiyaku, cationic water-soluble resin Product name: Kuraray Poval PVA-103, manufactured by Kuraray, a water-soluble resin (polyvinyl alcohol) without ionic groups Acetylenol E100, a nonionic surfactant manufactured by Kawaken Fine Chemicals

[0097] The surface tension γ (mN / m) of the prepared clear ink was measured at 25° C. using an automatic surface tensiometer (product name "DY-300", manufactured by Kyowa Interface Science Co., Ltd.).

[0098] [Table 1]

[0099] [Table 2]

[0100] <Preparation of reaction solution> The components (unit: %) shown in Table 3 were mixed and thoroughly stirred, and then pressure filtered using a filter with a pore size of 3.0 μm (product name "Cellulose Acetate Filter" (manufactured by Advantec) to prepare each reaction solution. Details of the components in Table 3 are as follows. Acetylenol E100, a nonionic surfactant manufactured by Kawaken Fine Chemicals Product name: Proxel GXL(S), manufactured by Lonza, antifungal agent

[0101] [Table 3]

[0102] <Preparation of pigment ink> Each pigment ink was prepared by mixing the components (unit: %) shown in Table 4, thoroughly stirring, and then filtering under pressure using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm. "Acetylenol E100" is the trade name of a surfactant manufactured by Kawaken Fine Chemicals.

[0103] [Table 4]

[0104] <Recording Media> The following recording media were prepared: Recording medium 1: Polyethylene terephthalate (PET) film (product name "Lumirror T-60 Transparent", manufactured by Toray, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption rate up to 2.5 mL / m 2 ) Recording medium 2: Art paper (product name "Art PW8K", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption rate up to 9.5 mL / m 2 ) Recording medium 3: High-quality paper (product name "55PW8KCOC", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption rate up to 12.0 mL / m 2 )

[0105] <Image recording> The clear ink, reaction liquid, and pigment ink obtained above were combined to form an ink set as shown in Table 5. Images were recorded using this ink set as follows.

[0106] An example where "1" is entered in the recording head column of Table 5 will be described. The recording head 1200 shown in FIG. 2 was incorporated into the clear ink applicator 1201, reaction liquid applicator 1202, and pigment ink applicator 1203 of the recording apparatus 100 shown in FIG. 1 so that the arrangement direction of the ejection port array intersects the recording medium transport direction. Each recording head 1200 was filled with clear ink, reaction liquid, and pigment ink. When two types of pigment ink were used, in the pigment ink applicator 1203, pigment ink 1 was filled in the recording head located most upstream in the recording medium transport direction, and pigment ink 2 was filled in the recording head located most downstream in the transport direction.

[0107] The following describes an example where "2" is entered in the recording head column of Table 5. The recording head 11 described in Patent Document 1 was incorporated into the clear ink applicator 1201, the reaction liquid applicator 1202, and the pigment ink applicator 1203 of the recording apparatus 100 shown in FIG. 1. Each recording head 11 was filled with a clear ink, a reaction liquid, and a pigment ink. The recording head 11 described in Patent Document 1 is a multi-pass recording head that ejects each liquid composition while performing a main scan of the recording head in a direction intersecting the arrangement direction of the ejection port array, and applies ink to a unit area in multiple main scans.

[0108] Using the inkjet recording apparatus 100 having the above configuration, images were recorded and evaluated on a recording medium under the conditions shown in Table 5. The image was recorded on the recording medium in the following order: application of clear ink by the clear ink applicator 1201, drying of the clear ink by the drying unit 1600, application of reaction liquid by the reaction liquid applicator 1202, and application of pigment ink by the pigment ink applicator 1203. Examples in which any of the steps was not performed are marked with "-" in the corresponding column. A 5 cm x 10 cm solid image was recorded using the inkjet recording apparatus 100 having the above configuration. In this example, the print duty of an image recorded under the condition of applying one 3.0 ng droplet to a unit area of ​​1 / 1200 inch x 1 / 1200 inch is defined as 100%.

[0109] (1) The conditions for applying the clear ink were a-1: a printing duty of 40% or a-2: a printing duty of 20%, and the clear ink was applied to an area of ​​5 cm×10 cm.

[0110] (2) The clear ink was dried by the drying unit 1600 by blowing air onto the recording medium. The temperature and duration of the air blown at this time are shown in Table 5. In Example 20, after the clear ink was applied to a predetermined position on the recording medium, a 20-second wait was allowed for the clear ink to dry before the reaction liquid was applied.

[0111] (3) A reaction liquid was applied to the 5 cm x 10 cm area to which the clear ink had been applied under the following application conditions b to d. The printing duty of the reaction liquid was set to 20% in all cases. b: In the region a-1, the region to which the clear ink is applied is included in the region to which the reaction liquid is applied. c: In the region a-2, the region to which the clear ink is applied and the region to which the reaction liquid is applied only partially overlap, and there is a region where the region to which the clear ink is applied and the region to which the reaction liquid is applied do not overlap. d: In the region a-2, the region to which the clear ink is applied and the region to which the reaction liquid is applied do not overlap.

[0112] (4) Solid images of 5 cm x 5 cm each using pigment ink 1 and pigment ink 2 were printed adjacent to each other at a printing duty of 100%, overlapping the 5 cm x 10 cm area to which the clear ink and reaction liquid had been applied. In Example 2, a solid image of 5 cm x 10 cm was printed using pigment ink 1.

[0113] (5) After the application of the clear ink, the reaction liquid, and the pigment ink was completed, the image recorded on the recording medium was heated by blowing hot air at 85° C. for 15 seconds onto the image.

[0114] [Table 5]

[0115] <Evaluation> The images recorded as described above were evaluated for each of the following items. In the present invention, "AA," "A," and "B" were considered acceptable levels, and "C" was considered unacceptable, based on the evaluation criteria for each item below. The evaluation results are shown in Table 6.

[0116] (Suppression of image unevenness) The solid image of the recorded matter obtained above was scanned using a scanner (product name "OFFIRIOES-10000G" manufactured by Epson) under the following conditions: Professional mode, resolution: 300 dpi, color: 24 bit. Using image processing software (product name "Photoshop" manufactured by Adobe), a 200 pixel x 200 pixel area was converted to grayscale, and the standard deviation obtained from the histogram was calculated. The suppression of image unevenness was evaluated according to the following criteria. The smaller the standard deviation, the more uniform the solid image and the better the suppression of image unevenness. AA: Standard deviation was less than 2.5 A: The standard deviation was 2.5 or more and less than 3.0. B: The standard deviation was 3.0 or more and less than 4.0. C: The standard deviation was 4.0 or more.

[0117] (Image bleeding suppression) The state of color mixing in the boundary region between pigment ink 1 and pigment ink 2 was observed under an optical microscope, and the suppression of image bleeding was evaluated according to the following criteria: In Example 2, the state of bleeding at the edge of the image was observed. AA: No color mixing occurred in the boundary area B: Color mixing occurred in the boundary area, but the boundary was continuous. C: Color mixing occurred in the boundary area, and the boundary was discontinuous. D: Color mixing occurred in the boundary area, making it difficult to distinguish the boundary.

[0118] [Table 6]

[0119] The disclosure of this embodiment includes the following methods and configurations.

[0120] (Method 1) An inkjet recording method in which a clear ink, a reaction liquid, and a pigment ink, all of which are aqueous liquid compositions, are ejected from a recording head to apply the ink to a recording medium so that an area to which at least one of the clear ink and the reaction liquid is applied and an area to which the pigment ink is applied at least partially overlap, thereby recording an image, 30 msec from the start of contact in the Bristow method of the recording medium 1 / 2 Water absorption up to 10.0 mL / m 2 is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

[0121] (Method 2) 2. The inkjet recording method according to claim 1, wherein the clear ink has a surface tension of 35.0 mN / m or less.

[0122] (Method 3) 3. The inkjet recording method according to any one of Methods 1 and 2, wherein the content (mass %) of the resin in the clear ink is 5.00 mass % or more based on the total mass of the ink.

[0123] (Method 4) 4. The inkjet recording method according to any one of Methods 1 to 3, wherein the resin of the clear ink contains resin particles.

[0124] (Method 5) 5. The inkjet recording method according to claim 4, wherein the resin particles of the clear ink are resin particles formed from an acrylic resin.

[0125] (Method 6) 6. The inkjet recording method according to any one of Methods 1 to 5, wherein the polyvalent metal salt in the reaction liquid is magnesium sulfate.

[0126] (Method 7) 7. The inkjet recording method according to any one of Methods 1 to 6, wherein the pigment ink further contains resin particles.

[0127] (Method 8) 8. The inkjet recording method according to any one of Methods 1 to 7, wherein in the drying step, the clear ink is dried by blowing hot air onto the recording medium.

[0128] (Method 9) 9. The inkjet recording method according to any one of Methods 1 to 8, wherein the region of the recording medium to which the clear ink is applied includes a region to which the reaction liquid is applied.

[0129] (Configuration 1) An inkjet recording device that records an image by ejecting a clear ink, a reaction liquid, and a pigment ink, all of which are aqueous liquid compositions, from a recording head, and applying the ink to a recording medium so that an area to which at least one of the clear ink and the reaction liquid is applied and an area to which the pigment ink is applied at least partially overlap, 30 msec from the start of contact in the Bristow method of the recording medium 1 / 2 Water absorption up to 10.0 mL / m 2 is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

[0130] (Configuration 2) an ink set including a clear ink, a reaction liquid, and a pigment ink, each of which is an aqueous liquid composition, for use in an inkjet recording method in which the clear ink, the reaction liquid, and the pigment ink are each ejected from a recording head and applied to a recording medium so that at least a portion of an area to which the clear ink, the reaction liquid, and the pigment ink are applied overlaps with each other, thereby recording an image; 30 msec from the start of contact in the Bristow method of the recording medium 1 / 2 Water absorption up to 10.0 mL / m 2 is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

Claims

1. An inkjet recording method in which a clear ink, a reaction liquid, and a pigment ink, all of which are aqueous liquid compositions, are ejected from a recording head to apply the ink to a recording medium so that an area to which at least one of the clear ink and the reaction liquid is applied and an area to which the pigment ink is applied at least partially overlap, thereby recording an image, 30 msec from the start of contact of the recording medium in the Bristow method １／２ The water absorption amount is 10.0 mL / m ２ is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

2. 2. The inkjet recording method according to claim 1, wherein the surface tension of the clear ink is 35.0 mN / m or less.

3. The inkjet recording method according to claim 1, wherein the content (% by mass) of the resin in the clear ink is 5.00% by mass or more based on the total mass of the ink.

4. The inkjet recording method according to claim 1 , wherein the resin of the clear ink contains resin particles.

5. 5. The ink jet recording method according to claim 4, wherein the resin particles of the clear ink are resin particles formed from an acrylic resin.

6. 2. The ink jet recording method according to claim 1, wherein the polyvalent metal salt in the reaction liquid is magnesium sulfate.

7. 2. The ink jet recording method according to claim 1, wherein the pigment ink further contains resin particles.

8. The inkjet recording method according to claim 1, wherein the clear ink is dried by blowing hot air onto the recording medium in the drying step.

9. 2. The inkjet recording method according to claim 1, wherein the area of ​​the recording medium to which the clear ink is applied includes an area to which the reaction liquid is applied.

10. An inkjet recording device that records an image by ejecting a clear ink, a reaction liquid, and a pigment ink, all of which are aqueous liquid compositions, from a recording head, and applying the ink to a recording medium so that an area to which at least one of the clear ink and the reaction liquid is applied and an area to which the pigment ink is applied at least partially overlap, 30 msec from the start of contact of the recording medium in the Bristow method １／２ The water absorption amount is 10.0 mL / m ２ is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

11. an ink set including a clear ink, a reaction liquid, and a pigment ink, each of which is an aqueous liquid composition, for use in an inkjet recording method in which the clear ink, the reaction liquid, and the pigment ink are each ejected from a recording head and applied to a recording medium so that at least a portion of an area to which the clear ink, the reaction liquid, and the pigment ink are applied overlaps with each other, thereby recording an image; 30 msec from the start of contact of the recording medium in the Bristow method １／２ The water absorption amount is 10.0 mL / m ２ is as follows: applying the clear ink, the reaction liquid, and the pigment ink to the unit area of ​​the recording medium by one relative scan of the recording head and the recording medium; the clear ink contains a resin, the reaction liquid contains a polyvalent metal salt as a reactant that reacts with the pigment ink, the pigment ink contains a pigment, a clear ink applying step of applying the clear ink to the recording medium; a drying step of drying the clear ink applied to the recording medium; a reaction liquid applying step of applying the reaction liquid to the recording medium; and a pigment ink applying step of applying the pigment ink to the recording medium, in this order.

Images