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

Abstract

To provide an inkjet recording method which is excellent in scratch resistance of an image imparted in a superposed state, even when being recorded on a non-absorptive recording medium.SOLUTION: An inkjet recording method discharges an aqueous reaction liquid containing aqueous ink and a reaction agent reactive with the aqueous ink from a recording head, and records an image on a recording medium. The inkjet recording method includes: a first ink imparting step of imparting first ink so as to be overlapped with at least a part of a region to which the aqueous reaction liquid of the recording medium is imparted; a drying step of drying the recording medium; and a second ink imparting step of imparting second ink so as to be overlapped with at least a part of a region to which the aqueous reaction liquid and the first ink are imparted, in this order. The first ink contains a pigment, resin particles, a wax, and a nonionic dispersant for dispersing the wax, the second ink contains a pigment and resin particles, and the aqueous reaction liquid contains a polyvalent metal salt.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, inkjet recording methods have been increasingly used in the field of sign and display, such as printing posters and large-format advertisements. In this field, inkjet recording devices are characterized by a larger recording area than home inkjet recording devices. In addition, since images need to be eye-catching, inks that can record images with high color development are required.

[0003] In the sign and display field, non-absorbent recording media, whose surfaces are made of polyvinyl chloride (PVC) or polyethylene terephthalate (PET), and whose surfaces have almost no ink absorption, are often used. For this reason, it is necessary to suppress bleeding of images on non-absorbent recording media. Hereinafter, recording media whose surfaces have almost no ink absorption will also be referred to as "non-absorbent recording media." In the inkjet recording method for recording on non-absorbent recording media, it is important to suppress bleeding by preventing ink dots from being repelled by the recording medium. To achieve this, it is necessary to rapidly thicken the ink after it is applied to the recording medium and fix it to the recording medium.

[0004] As a method for recording on a non-absorbent recording medium, a recording method using a solvent-based ink containing an organic solvent as a main component or a curable ink containing a polymerizable monomer is known. However, in recent years, from the viewpoints of environmental load and safety, there is an increasing need for a recording method that can record on a non-absorbent recording medium using a water-based ink.

[0005] Methods of recording on non-absorbent recording media using aqueous ink include a method of evaporating the water content of the ink on the surface of the non-absorbent recording media, and a method of using a reaction liquid that aggregates the ink components. The former is advantageous in terms of running costs because there is no need to provide a means for applying the reaction liquid, but it is necessary to slow down the recording speed, which reduces productivity. For this reason, a method using a reaction liquid has been considered (see Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-147405 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors performed recording on a non-absorbent recording medium using the first reaction liquid, the second reaction liquid, the first ink, and the second ink described in Patent Document 1, and evaluated various properties. As a result, it was found that although a certain degree of image quality was obtained, the scratch resistance of the images applied in layers was insufficient.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method which produces images with excellent abrasion resistance even when recorded on a non-absorbent recording medium. Another object of the present invention is to provide an inkjet recording apparatus and a set of an aqueous ink and an aqueous reaction liquid for use in the inkjet recording method. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method for ejecting an aqueous ink and an aqueous reactive liquid containing a reactant that reacts with the aqueous ink from a recording head to record an image on a recording medium, the aqueous ink including a first ink and a second ink, the method comprising the steps of: a reaction liquid applying step of applying the aqueous reactive liquid to the recording medium; a first ink applying step of applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reactive liquid is applied; a drying step of drying the recording medium; and a second ink applying step of applying the second ink so as to overlap at least a portion of an area to which the aqueous reactive liquid and the first ink are applied, in this order, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax, the second ink contains a pigment, and resin particles, the aqueous reactive liquid contains a polyvalent metal salt, and the first ink is allowed to dry within 30 msec from the start of contact of the recording medium in a Bristow method. 1 / 2 Water absorption up to 10mL / m 2 There is provided an ink jet recording method characterized in that: Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method that provides excellent abrasion resistance of images applied in layers even when recorded on a non-absorbent recording medium. 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 an aqueous reaction liquid. [Brief description of the drawings]

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

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

[0013] The present inventors first investigated the reason why the image could not be abrasion-resistant in the inkjet recording method using two kinds of reaction liquids and two kinds of inks described in Patent Document 1. When an image is recorded on a non-absorbent recording medium using a reaction liquid, unlike an absorbent recording medium, the ink components hardly penetrate into the inside of the recording medium, so that the unreacted reaction agent remains on the surface of the recording medium. Therefore, it is considered that the reaction agent is in a state of being precipitated on the surface of the recording medium after the first reaction liquid and the first ink are applied. In particular, when a polyvalent metal salt is used as the first reaction liquid, it is found that crystals are more likely to be formed on the surface of the recording medium than organic acids and cationic resins that are commonly used as reaction agents, and the smoothness of the image is low. And, when an image is recorded by applying ink on such an uneven image, the unevenness of the formed crystals of the polyvalent metal salt affects the ink layer, and as a result, it is considered that the abrasion resistance of the image applied in layers is reduced.

[0014] Therefore, the present inventors further investigated ways to suppress the deposition of polyvalent metal salts on the image surface, and found that the scratch resistance of the ink applied in layers can be improved by adding a specific wax to the ink and providing a process for drying the image.

[0015] That is, the inkjet recording method of the present invention has the following characteristics. First, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax. The second ink contains a pigment and resin particles. The water-based ink contains a polyvalent metal salt. The recording medium is subjected to a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 10mL / m 2 The method includes, in this order, a step of applying a reaction liquid, a step of applying a first ink, a step of drying the recording medium, and a step of applying a second ink. The present inventors speculate that the mechanism by which the above configuration can improve the scratch resistance of the second ink (the ink applied in a layered manner) is as follows.

[0016] The first ink contains, in addition to the pigment and resin particles, wax and a nonionic dispersant for dispersing the wax. That is, the wax is dispersed by the nonionic dispersant. Therefore, when the reaction liquid and the first ink come into contact with each other on the recording medium, the pigment and resin particles aggregate and thicken, while the wax dispersed by the nonionic dispersant does not aggregate and is less likely to affect the thickening. As a result, it is considered that the wax maintains a dispersed state in the liquid even when it comes into contact with the reaction liquid. Since the wax has a relatively small specific gravity and is highly hydrophobic, it is oriented toward the gas-liquid interface. Then, by carrying out a drying process for drying the recording medium before applying the second ink, it is considered that the evaporation of the liquid components proceeds with the wax oriented at the gas-liquid interface, and the surface of the ink layer is covered with the wax. As a result, it is possible to suppress the precipitation of the polyvalent metal salt in the reaction liquid on the surface of the ink layer, and improve the scratch resistance of the image applied in layers. If a drying step is not performed before the application of the second ink, the precipitation of crystals of the polyvalent metal salt on the surface of the ink layer cannot be prevented, and the scratch resistance of the image applied in layers cannot be obtained.

[0017] Furthermore, when a reactant other than a polyvalent metal salt (such as a cationic resin or an organic acid) is used as the reactant, crystals are unlikely to precipitate on the surface of the ink layer or do not precipitate at all, so the above problem does not arise. In other words, the problem of the scratch resistance of the images applied in layers is a problem that arises specifically when a polyvalent metal salt is used as the reactant.

[0018] <Inkjet recording method, inkjet recording apparatus, and water-based ink> The inkjet recording method of the present invention (hereinafter, also simply referred to as "recording method") is a method in which an aqueous ink and an aqueous reaction liquid are ejected from an inkjet recording head by the action of thermal energy, and applied to a recording medium to record an image. The recording method of the present invention includes, in this order, a reaction liquid application step of applying the aqueous reaction liquid to the recording medium, a first ink application step of applying a first ink so as to overlap at least a part of the area of ​​the recording medium to which the aqueous reaction liquid is applied, a drying step of drying the recording medium, and a second ink application step of applying a second ink so as to overlap at least a part of the area to which the aqueous reaction liquid and the first ink are applied. The first ink is an aqueous ink containing a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax. The second ink is an aqueous ink containing a pigment and resin particles. The aqueous reaction liquid contains a polyvalent metal salt. The recording medium is subjected to a drying test within 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 10mL / m 2 The recording medium is as follows:

[0019] The inkjet recording apparatus of the present invention (hereinafter, also simply referred to as "recording apparatus") is an apparatus used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid are ejected from an inkjet recording head by the action of thermal energy and applied to a recording medium to record an image. The recording apparatus of the present invention is an apparatus that is suitably used in the above-mentioned recording method. In the recording method and recording apparatus of the present invention, it is not necessary to cure the image by irradiation with active energy rays or the like.

[0020] The set of aqueous ink and aqueous reaction liquid of the present invention is a set used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink are ejected from a recording head to record an image on a recording medium. The set is preferably used in the above-mentioned recording method. The form of the set includes a set of multiple ink cartridges each containing multiple inks (reaction liquids) independently, and an ink cartridge formed integrally by combining multiple ink containing parts each containing multiple inks (reaction liquids). The set of the present invention is not limited to the above form and may be in any form as long as it is configured so that the inks and reaction liquids can be used in combination.

[0021] (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.

[0022] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured to include a first recording section 1000, a heating section 2000, a fixing section 3000, a cooling section 4000, a second recording section 5000, an inversion section 6000, and a paper discharge section 7000. In the first recording section 1000, various liquids are applied by a liquid application device 1200 to a recording medium 1100 conveyed from a paper feeder 1400 by a conveying member 1300. In the heating section 2000, the liquid applied to the recording medium 1100 is heated by a heating device 2100, and volatile components such as water in the liquid are evaporated and dried. In the fixing section 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 section 4000. In the second recording section 5000, various liquids are applied to the recording medium 1100 by a liquid application device 5200. 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 6100 of the inversion section 6000. Next, after an image is recorded on the back side in the same manner as for the front side, the recording medium is transported by a transport member 7100 of the paper discharge section 7000 and stacked and stored in the recording medium storage section 7200.

[0023] [Recording Section] The first 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. The reaction liquid applying device 1201 shown in FIG. 1 is an example of a unit using an inkjet type ejection head. Alternatively, the reaction liquid applying device may be configured using a gravure coater, an offset coater, a die coater, a blade coater, or the like. The reaction liquid may be applied by the reaction liquid applying device 1201 either before or after the ink application as long as the reaction liquid 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 ejection head (recording head) is used as the ink applying device 1202. The ejection method of the ejection head as the liquid applying device 1200 may include a method of ejecting liquid by generating film boiling in the liquid by an electrothermal converter to form bubbles, and a method of ejecting liquid by an electromechanical converter. From the viewpoint of image quality, it is preferable that the time until the reaction liquid and the ink come into contact is short. Specifically, it is preferable that the time from the application of the reaction liquid to the application of the ink is 2500 milliseconds or less. Here, the time from the application of the reaction liquid to the application of the first ink may be the same as or different from the time from the application of the reaction liquid to the application of the second ink. This time can be appropriately changed by adjusting the distance between the means for applying the reaction liquid and the means for applying the ink, or by adjusting the conveying speed of the recording medium. It is preferable that the time from the application of the reaction liquid to the application of the ink is 100 milliseconds or more, and more preferably 200 milliseconds or more.

[0024] It is preferable that the aqueous ink and the aqueous reaction liquid are applied to a unit area of ​​the recording medium by one relative scan of the recording head and the recording medium. This type of recording method is also called one-pass recording or single-pass recording. This type of recording method allows the wax to be present on the ink layer surface more efficiently than multi-pass recording, in which application is performed by multiple relative scans of the recording head and the recording medium.

[0025] 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.

[0026] 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".

[0027] The second recording section 5000 includes a liquid applying device 5200. The liquid applying device 5200 includes a reaction liquid applying device 5201 and an ink applying device 5202. The second recording section may include the same components as those of the first recording section. The first recording section does not need to be separated from the second recording section as shown in FIG. 1. For example, the first recording section may include a plurality of reaction liquid applying devices 1201 and ink applying devices 1202, and the recording medium may be returned to the first recording section after the cooling section 4000 using a mechanism for returning the recording medium to the first recording section, and then recording may be performed. In that case, the reaction liquid applying device 1201 and the ink applying device 1202 used when passing through the first recording section 1000 for the first time may be different from the reaction liquid applying device 1201 and the ink applying device 1202 used when passing through the second time.

[0028] 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.

[0029] 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.

[0030] [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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] [Transport system] As shown in FIG. 1, the first 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 member 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 suctioning from the back side to fix the recording medium 1100, a method of forming the conveying member 1300 from an appropriate material and electrostatically adsorbing the recording medium 1100, and the like can be mentioned. The second recording unit 5000 can also be configured in the same manner as the first recording unit 1000.

[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, 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 conveyed by the conveying member 2200, thereby evaporating the liquid components of the image and drying it. In other words, the recording medium is dried by the heating section 2000. In particular, as shown in FIG. 1, 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.

[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 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 viewpoint of safety and energy efficiency. Furthermore, if a mechanism for blowing hot air with a built-in fan is used to inject heated gas onto the recording medium 1100, the drying efficiency can be easily improved. Therefore, the drying process is preferably an air blowing process in which the recording medium is dried by blowing hot air onto it.

[0037] 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.

[0038] 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 is at 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 (°C) of the hot air in the blowing process is preferably 60°C or higher and 90°C or lower. The temperature of the air 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).

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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.

[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 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 formed into a film mainly by heating in the fixing unit 3000, and the coloring material can be bound onto the recording medium 1100. The recording method and recording apparatus of the present invention do not need to have a fixing unit. In that case, the recording medium may be dried and fixed in the heating unit.

[0044] 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.).

[0045] The first ink described below contains resin particles and particles (wax particles) formed of wax. Therefore, when 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. It is also 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.

[0046] 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.

[0047] 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.

[0048] [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).

[0049] The above-mentioned heating unit, fixing unit, and cooling unit may be provided after the second recording unit 5000. In this case, they may have the same configuration as the above-mentioned heating unit, fixing unit, and cooling unit, or may have different configurations.

[0050] [Inverted part] When performing double-sided recording, the recording medium 1100 is inverted using the inversion unit 6000 (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 6100. 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)).

[0051] [Paper output section] After the image is recorded, the recording medium 1100 is stored in a paper discharge section 7000 (FIG. 1). After single-sided or double-sided recording is performed, the recording medium 1100 passes through a cooling section 4000, is transported by a transport member 7100, and is finally stored in a stacked state in a recording medium storage section 7200. Two or more recording medium storage sections 7200 may be provided to store different recorded materials, etc.

[0052] (Recording medium) In the recording method and recording device of the present invention, a non-absorbent recording medium (a low to non-absorbent recording medium) is used. The low to non-absorbent recording medium is a recording medium that is absorbed 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 0mL / m 2 More than 10mL / m 2 In the present invention, a recording medium that satisfies the above-mentioned condition of water absorption amount is defined as a "low to non-absorbent recording medium". A recording medium for inkjet recording having a coating layer (ink receiving layer) formed of inorganic particles (glossy paper, matte paper, etc.) and plain paper having no coating layer have a water absorption amount of 10 mL / m 2 It is an "absorbent recording medium" that exceeds this.

[0053] Examples of low to non-absorbent recording media that can be used include plastic films; recording media in which a plastic film is adhered to the recording surface of a substrate; and recording media in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp. Of these, plastic films are preferred, and recording media in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp are also preferred. The basis weight (g / m2) of the recording medium 1100 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:

[0054] When the ink used in the recording method and recording apparatus of the present invention is applied to a non-absorbent recording medium, the liquid components such as water evaporate and the resin particles are concentrated. This promotes fusion between the concentrated resin particles, improving the strength of the recorded image. In contrast, when the ink is applied to a recording medium that has high absorbency of the liquid components, the fusion between the resin particles is not promoted, and the strength of the image is not improved. In this specification, the recording medium does not mean a transfer body, but a recording medium on which an image as a recorded matter is recorded.

[0055] <Reaction solution> The recording method of the present invention has a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the ink to a recording medium before the first ink application step. Also, a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the ink to a recording medium before the second ink application step may be included. In this case, the reaction liquid used for the first ink and the reaction liquid used for the second ink may be the same or different. Each component used in the reaction liquid will be described in detail below.

[0056] [Reactants] The reactive liquid reacts with the ink when it comes into contact with the ink, coagulating the components in the ink (components having anionic groups, such as resins, surfactants, and self-dispersing pigments), and contains a polyvalent metal salt as a reactive agent. The presence of the reactive agent can destabilize the state of the components in the ink having anionic groups when the ink and the reactive agent come into contact with each other on the recording medium, thereby promoting the coagulation of the ink.

[0057] Examples of polyvalent metal ions constituting polyvalent metal salts include Ca. 2+ , Cu 2+ , Ni 2+ , Mg 2+ , Sr 2+ , B.A. 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+In order to add a polyvalent metal ion 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 - Among them, it is preferable to use magnesium sulfate as the polyvalent metal salt from the viewpoint of excellent aggregation of the ink components and improvement of abrasion resistance. In other words, it is preferable that the polyvalent metal salt in the aqueous reaction liquid is magnesium sulfate. The reaction agent may be used alone or in combination of two or more kinds.

[0058] The content (mass%) of the polyvalent metal salt in the aqueous reaction liquid is preferably 10.0% by mass or less based on the total mass of the reaction liquid. It is also preferably 1.0% by mass or more, and more preferably 1.0% by mass or more and 5.0% by mass or less. In this specification, the "content (mass%) of the polyvalent metal salt" in the reaction liquid when the polyvalent metal salt is a hydrate means the "content (mass%) of the anhydride of the polyvalent metal salt" excluding water as the hydrate. If the content of the polyvalent metal salt exceeds 10.0% by mass, precipitation of the polyvalent metal salt may not be effectively suppressed even if wax is present. As a result, sufficient abrasion resistance may not be obtained.

[0059] The reactant may be an organic acid or a cationic resin other than the polyvalent metal salt. It is more preferable that the reaction solution further contains a cationic resin.

[0060] The reaction liquid containing an organic acid has a buffering ability in the acidic range (less than pH 7.0, preferably pH 2.0 to 5.0), and thus efficiently converts the anionic groups of the components present in the ink into an acid form and causes them to aggregate. Examples of the organic acid include monocarboxylic acids and salts thereof, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furan carboxylic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and salts and hydrogen salts thereof, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and salts and hydrogen salts thereof, such as citric acid and trimellitic acid; and tetracarboxylic acids and salts and hydrogen salts thereof, such as pyromellitic acid. When an organic acid is used as the reactant, the content (mass %) of the organic acid in the reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0061] Examples of cationic resins include resins having a structure of primary to tertiary amines and resins having a structure of quaternary ammonium salts. Specific examples include resins having a structure of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensate. In order to increase the solubility in the reaction solution, the cationic resin may be used in combination with an acidic compound or the cationic resin may be subjected to a quaternary treatment. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 0.1 mass% or more and 10.0 mass% or less based on the total mass of the reaction solution.

[0062] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. Examples of the aqueous medium used in the reaction liquid include the same aqueous medium that can be contained in the ink, which will be described later. The content (mass%) of the water-soluble organic solvent in the reaction liquid is preferably 1.0 mass% or more and 45.0 mass% or less, based on the total mass of the reaction liquid. The water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound, which will be described later. The content (mass%) of the water-soluble hydrocarbon compound in the reaction liquid is preferably 1.0 mass% or more and 20.0 mass% or less, based on the total mass of the reaction liquid. In addition, the content (mass%) of water in the reaction liquid is preferably 50.0 mass% or more and 95.0 mass% or less, based on the total mass of the reaction liquid.

[0063] [Other ingredients] The reaction liquid may contain various other components as necessary, including the same components as those that can be contained in the ink, which will be described later.

[0064] The reaction liquid preferably contains a water-soluble organic solvent having a boiling point of less than 260°C. By setting the boiling point to less than 260°C, evaporation of the water-soluble organic solvent is promoted. As a result, the amount of liquid components remaining in the ink film can be reduced, and the scratch resistance can be further improved. 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), 2-methyl-1,3-propanediol (223°C), and 2-methyl-1,3-propanediol (223°C). Examples of such polymers include 1,5-pentanediol (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).

[0065] When a water-soluble organic solvent having a boiling point of 260° C. or more is contained, it is preferable to reduce the amount thereof as described above. Specifically, the content of the water-soluble organic solvent having a boiling point of 260° C. or more is preferably 1.0 mass% or less based on the total mass of the reaction liquid. In particular, it is more preferable that it is 0.5 mass% or less, and particularly preferable that it is 0.1 mass% or less. In addition, the content of the water-soluble organic solvent having a boiling point of 260° C. or more may be 0.0 mass%. In other words, it is preferable that the aqueous reaction liquid does not substantially contain a water-soluble organic solvent having a boiling point of 260° C. or more.

[0066] [Physical properties of reaction solution] The reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the 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.

[0067] <First ink> The first ink used in the recording method of the present invention is an inkjet water-based ink containing a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax. Each component of the first ink will be described in detail below.

[0068] [Colorant] The first ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably 0.5% to 20.0% by mass, and more preferably 1.0% to 15.0% by mass, based on the total mass of the ink.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0073] The cumulative 50% particle size (D 50) is preferably 50 nm or more and 300 nm or less, and more preferably 50 nm or more and 200 nm or less. The volume-based cumulative 50% particle diameter of a pigment is the diameter of a particle 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 a pigment can be measured using a dynamic light scattering particle size analyzer and under the measurement conditions described in the section [Resin] below.

[0074] The pigment of the first ink is preferably titanium oxide. Titanium oxide has a larger specific gravity than the other components in the ink, and therefore tends to sink into the ink layer. As a result, the wax can be more easily present on the surface of the ink layer.

[0075] Inorganic oxides such as titanium oxide react with water molecules constituting the aqueous medium in the aqueous ink to generate hydroxyl groups (hereinafter, sometimes referred to as "surface hydroxyl groups") on the surface. For this reason, in the case of aqueous inkjet inks, in order to utilize the generated surface hydroxyl groups while further improving the storage stability of the ink, the ink is generally used in a state where the ink is surface-treated with inorganic oxides such as alumina or silica. The surface hydroxyl groups of titanium oxide particles have properties specific to the inorganic oxide corresponding to the inorganic compound used in the surface treatment, and the isoelectric point, which is an indicator of the strength of the acid, differs depending on the type of inorganic compound. Therefore, although titanium oxide itself is an inorganic oxide, the surface of titanium oxide particles shows the properties of an inorganic oxide corresponding to the inorganic compound used in the surface treatment, and the surface charge of titanium oxide particles is strongly dependent on the pH of the aqueous medium, the type of surface treatment agent, and the amount of the surface treatment agent used.

[0076] Titanium oxide is a white pigment, and has three crystal forms: rutile, anatase, and brookite. Among them, rutile titanium oxide is preferred. Titanium oxide can be industrially produced by the sulfuric acid method and the chlorine method, and the titanium oxide used in the present invention may be produced by either method.

[0077] Titanium oxide may be surface-coated (surface-treated) with an inorganic oxide or an organic substance. In particular, titanium oxide surface-treated with alumina and silica is preferably used. The surface treatment is expected to suppress photocatalytic activity and improve dispersibility. In this specification, "alumina" is a general term for oxides of aluminum such as aluminum oxide. In this specification, "silica" is a general term for silicon dioxide or a substance composed of silicon dioxide. Most of the alumina and silica that coat titanium oxide are present in the form of silicon dioxide and aluminum oxide.

[0078] The ratio of alumina and silica in titanium oxide particles, i.e., the amount of alumina and silica coating, can be measured, for example, by quantitative analysis of aluminum and silicon elements by inductively coupled plasma (ICP) emission spectrometry. In this case, it is assumed that all atoms coating the surface are in the form of oxides, and the obtained values ​​of aluminum and silicon can be converted to the oxides, i.e., alumina and silica, to calculate the amount of alumina and silica.

[0079] Surface treatment methods for titanium oxide include wet treatment and dry treatment. For example, titanium oxide can be dispersed in a liquid medium and then reacted with a surface treatment agent such as sodium aluminate or sodium silicate to perform surface treatment, and the desired characteristics can be achieved by appropriately changing the ratio of these surface treatment agents. In addition to alumina and silica, inorganic oxides such as zinc oxide and zirconia, and organic substances such as polyols can also be used for surface treatment, as long as the effects of the present invention are not impaired.

[0080] [resin] The first ink contains resin particles. The first ink may further contain a water-soluble resin that can be dissolved in an aqueous medium. 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, and (ii) to improve various properties of the recorded image.

[0081] 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 used alone or in combination of two or more kinds.

[0082] [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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] [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.

[0087] 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.

[0088] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, and more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D 50) is preferably 50 nm or more and 300 nm or less, more preferably 50 nm or more and 200 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, 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.

[0089] [Wax particles] The first ink contains particles (wax particles) formed of wax. This wax is dispersed with a nonionic dispersant. That is, the first ink contains wax and a nonionic dispersant for dispersing the wax. 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 may be wax itself. One type of wax may be used alone, or two or more types may be used in combination. The total content (mass %) of the wax and the dispersant for dispersing the wax in the ink is preferably 0.1 mass % or more and preferably 10.0 mass % or less based on the total mass of the ink. In particular, it is more preferably 1.0 mass % or more and 5.0 mass % or less.

[0090] 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).

[0091] 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.

[0092] 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.

[0093] The cumulative 50% particle size (D 50 ) is preferably 50 nm or more and 500 nm or less, and more preferably 100 nm or more and 300 nm or less. The volume-based cumulative 50% particle diameter of the wax is the diameter of a particle 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 wax can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above.

[0094] Cumulative 50% particle size D of the pigment in the first ink based on volume P (nm), cumulative 50% particle diameter D of wax by volume W (nm), and the volume-based cumulative 50% particle diameter D of the resin particles EIt is preferable that (nm) satisfies the relationship of the following formula. By making the particle size of the resin particles equal to or smaller than the particle size of the pigment, the effect of scattered light by the resin particles is suppressed, and glossiness can be improved. In addition, by making the particle size of the pigment equal to or larger than the particle sizes of the other components, the pigment sinks in the ink layer and is more likely to be located in the lower layer, which makes it easier for the wax to be present on the surface of the ink layer. D P ≧D W ≧D E

[0095] [Nonionic dispersant] Examples of nonionic dispersants that can be used as dispersants for wax include compounds represented by the following general formula (1). These compounds are also called polyoxyalkylene alkyl ethers and polyoxyalkylene alkenyl ethers. Hereinafter, alkyl ethers and alkenyl ethers will be collectively referred to as alkyl ethers for convenience. R 1 -O-(R 2 O) n -H (In general formula (1), R 1 R represents an alkyl or alkenyl group having 4 to 40 carbon atoms. 2 each independently represents an ethylene group, a propylene group, or a butylene group; and n is 3 or more and 50 or less.

[0096] R 1 R represents an alkyl or alkenyl group having 4 to 40 carbon atoms. 2 each independently represents an ethylene group, a propylene group, or a butylene group. Among these, an ethylene group or a propylene group is preferable. n is 3 or more and 50 or less.

[0097] Examples of polyoxyalkylene alkyl ethers include polyoxyethylene alkyl ethers (general formula (2): R 1 -O-(C2H4O) n -H), polyoxypropylene alkyl ether (general formula (3): R 1 -O-(C3H6O) n-H), polyoxyethylene-polyoxypropylene alkyl ether (general formula (4): R 1 -O-[(C2H4O) n1 -(C3H6O) n2 ]-H), polyoxybutylene alkyl ether (general formula (5): R 1 -O-(C4H8O) n Among them, polyoxyethylene alkyl ether and polyoxypropylene alkyl ether are preferable. These nonionic dispersants may be used alone or in combination of two or more. As described above, R 1 represents a hydrocarbon group (alkyl group or alkenyl group), and n (including each of the independent n1 and n2) represents the number of moles (number of repeating units) of alkylene oxide (ethylene oxide, propylene oxide, or butylene oxide) added.

[0098] Examples of polyoxyethylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene isostearyl ether, polyoxyethylene behenyl ether, and polyoxyethylene octyldodecyl ether.

[0099] Examples of polyoxypropylene alkyl ethers include polyoxypropylene butyl ether, polyoxypropylene myristyl ether, polyoxypropylene cetyl ether, and polyoxypropylene stearyl ether.

[0100] Examples of polyoxyethylene-polyoxypropylene alkyl ethers include polyoxyethylene-polyoxypropylene butyl ether, polyoxyethylene-polyoxypropylene lauryl ether, polyoxyethylene-polyoxypropylene cetyl ether, and polyoxyethylene-polyoxypropylene stearyl ether.

[0101] Among the polyoxyalkylene alkyl ethers, polyoxyethylene alkyl ethers are preferred. That is, the nonionic dispersant is preferably a compound represented by the following general formula (2). R 1 -O-(C2H4O) n -H···(2) (In general formula (2), R 1 represents an alkyl group or an alkenyl group having 4 or more and 40 or less carbon atoms; and n is 3 or more and 50 or less.

[0102] The number of moles of alkylene oxide added (n in the general formulas (1) and (2)) is 3 or more and 50 or less. In particular, it is preferably 10 or more and 40 or less. 1 The hydrocarbon group represented by R may be either linear or branched, and may be either saturated or unsaturated. 1 The hydrocarbon group represented by the following formula preferably has 5 or more and 30 or less carbon atoms.

[0103] The content (mass%) of the nonionic dispersant in the ink is preferably 0.01% by mass to 2.5% by mass, more preferably 0.1% by mass to 2.5% by mass, based on the total mass of the ink. Of these, the content (mass%) of the nonionic dispersant in the ink is more preferably 0.3% by mass to 1.5% by mass. The content (mass%) of the nonionic dispersant in the ink is preferably 0.10 times to 0.40 times the mass of the wax content (mass%).

[0104] [Anionic Dispersant] As a dispersant for wax, it is preferable to use an anionic dispersant in addition to a nonionic dispersant. As an anionic dispersant that can be used as a dispersant for wax, a compound having at least one anionic group selected from the group consisting of a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group can be used. Among them, the anionic group in the anionic dispersant is preferably a carboxylic acid group.

[0105] As the anionic dispersant, an anionic surfactant or a resin having an anionic group can be suitably used. Specific examples of the anionic surfactant include carboxylate, sulfonate, sulfate, and phosphate. More specifically, linear higher carboxylic acid (salt), sulfonic acid (salt), alkylbenzenesulfonate, alkyl sulfate, polyoxyethylene alkyl sulfate, and alkyl phosphate can be mentioned.

[0106] In addition, specific examples of resins having anionic groups include ethylene acrylic acid copolymers. Among them, the anionic dispersant having an anionic group is preferably an ethylene acrylic acid copolymer. In addition, as compounds having an anionic group, montanic acid, linoleic acid, or salts thereof (preferably potassium salts) can also be used.

[0107] The content (mass %) of the anionic dispersant in the ink is preferably from 0.01 to 2.5% by mass, more preferably from 0.02 to 2.0% by mass, and particularly preferably from 0.04 to 1.5% by mass, based on the total mass of the ink.

[0108] The content (mass%) of the anionic dispersant in the ink is preferably 0.10 to 0.50 times the content (mass%) of the nonionic dispersant in the ink, and the total content (mass%) of the nonionic dispersant and the anionic dispersant in the ink is preferably 0.15 to 0.50 times the content (mass%) of the wax in the ink.

[0109] [Aqueous medium] The first 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 50.0 mass% or more and 95.0 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 2.0 mass% or more and 40.0 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.

[0110] The first ink preferably contains a water-soluble organic solvent having a boiling point of less than 260° C., similar to the reaction liquid. By setting the boiling point to less than 260° C., the evaporation of the water-soluble organic solvent is promoted. As a result, the amount of liquid component remaining in the ink film can be reduced, and the scratch resistance can be further improved. As the water-soluble organic solvent having a boiling point of less than 260° C., any of those described above for the reaction liquid can be appropriately selected and used.

[0111] When a water-soluble organic solvent having a boiling point of 260° C. or higher is contained, it is preferable to reduce the amount thereof as described above. Specifically, the content of the water-soluble organic solvent having a boiling point of 260° C. or higher is preferably 1.0% by mass or less based on the total mass of the ink. In particular, it is more preferable that it is 0.5% by mass or less, and particularly preferable that it is 0.1% by mass or less. Furthermore, the content of the water-soluble organic solvent having a boiling point of 260° C. or higher may be 0.0% by mass. In other words, it is preferable that the water-based ink does not substantially contain a water-soluble organic solvent having a boiling point of 260° C. or higher.

[0112] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent contained in the first ink preferably contains a specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain with 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.

[0113] In the present invention, a hydrocarbon compound that is dissolved in water at 25°C at the content of the compound in the ink is considered to be "water-soluble". In other words, the solubility in water at 25°C is greater than the content in the ink. The fact that the hydrocarbon chain is interrupted by a sulfonyl group or an ether group means that a sulfonyl group (-S(=O)2-) or an ether group (-O-) is present in the middle of the hydrocarbon chain. Water-soluble hydrocarbon compounds have hydrogen-bonding groups such as hydroxyl groups, amino groups, anionic groups, sulfonyl groups, and ether groups. Therefore, by using an ink containing this hydrocarbon compound, cockling and curling of a recording medium on which an image is recorded can be suppressed. General hydrocarbon compounds having a hydrocarbon chain with a relatively small number of carbon atoms (3 or 4) tend to have a small molecular weight and a low vapor pressure. However, since the above water-soluble hydrocarbon compounds have anionic groups of hydrogen bonds or the hydrocarbon chain is interrupted by a sulfonyl group, they are difficult to evaporate due to inter- or intra-molecular interactions, and remain between fibers to suppress cockling and curling. The content (mass %) of the water-soluble hydrocarbon compound in the ink is preferably 1.0 mass % or more and 20.0 mass % or less based on the total mass of the ink.

[0114] 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.

[0115] [Other ingredients] The first ink may contain various other components as necessary. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the first ink does not contain a reactant to be contained in the reaction liquid.

[0116] [Ink properties] The first ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0117] <Second ink> The second ink used in the recording method of the present invention is a water-based ink for ink-jet recording that contains a pigment and resin particles. Each component of the second ink will be described in detail below.

[0118] [Colorant] The second ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably 0.5% to 20.0% by mass, and more preferably 1.0% to 15.0% by mass, based on the total mass of the ink.

[0119] 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, and dioxazine. One type of pigment may be used alone, or two or more types may be used in combination. In particular, the pigment of the second ink is preferably at least one type selected from the group consisting of carbon black and organic pigments.

[0120] 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.

[0121] 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.

[0122] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0123] The cumulative 50% particle size (D 50) is preferably 50 nm or more and 300 nm or less, and more preferably 50 nm or more and 200 nm or less. The volume-based cumulative 50% particle diameter of a pigment is the diameter of a particle 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 a pigment can be measured using a dynamic light scattering particle size analyzer and under the measurement conditions described in the section [Resin] below.

[0124] [resin] The second ink contains resin particles. The second ink may further contain a water-soluble resin that can be dissolved in an aqueous medium. The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, i.e., as a resin dispersant or its auxiliary, and (ii) to improve various properties of the recorded image.

[0125] 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 used alone or in combination of two or more kinds.

[0126] The resin can be appropriately selected from those listed as usable for the first ink, and its properties can also be appropriately determined from those listed as usable for the first ink.

[0127] [Wax particles] The second ink preferably contains particles formed of wax (wax particles). The dispersant may be either a nonionic dispersant or a nonionic dispersant. In particular, like the first ink, the second ink preferably contains wax and a nonionic dispersant for dispersing the wax. By adding the wax to the second ink, the slipperiness of the ink layer formed of the second ink is improved, and the abrasion resistance can be further improved.

[0128] The wax can be appropriately selected from those listed as usable for the first ink, and its properties can also be appropriately determined from those listed as applicable to the first ink.

[0129] [Aqueous medium] The second 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 50.0 mass% or more and 95.0 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 2.0 mass% or more and 40.0 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.

[0130] The water-soluble organic solvent of the second ink can be appropriately selected from those listed as usable for the first ink. In particular, the second ink preferably contains a water-soluble organic solvent having a boiling point of less than 260°C, like the reaction liquid. By setting the boiling point to less than 260°C, the evaporation of the water-soluble organic solvent is promoted. As a result, the amount of liquid components remaining in the ink film can be reduced, and the abrasion resistance can be further improved. The water-soluble organic solvent having a boiling point of less than 260°C can be appropriately selected from those described for the reaction liquid.

[0131] When a water-soluble organic solvent having a boiling point of 260° C. or higher is contained, it is preferable to reduce the amount thereof as described above. Specifically, the content of the water-soluble organic solvent having a boiling point of 260° C. or higher is preferably 1.0% by mass or less based on the total mass of the ink. In particular, it is more preferable that it is 0.5% by mass or less, and particularly preferable that it is 0.1% by mass or less. Furthermore, the content of the water-soluble organic solvent having a boiling point of 260° C. or higher may be 0.0% by mass. In other words, it is preferable that the water-based ink does not substantially contain a water-soluble organic solvent having a boiling point of 260° C. or higher.

[0132] [Other ingredients] The second ink may contain various other components as necessary. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the second ink does not contain a reactant to be contained in the reaction liquid.

[0133] [Ink properties] The second ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less. EXAMPLES

[0134] 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.

[0135] <Method of measuring physical properties> (Determining whether the resin is a resin particle or not, cumulative 50% particle size based on volume of resin particles and wax particles) The liquid containing the resin was diluted with ion-exchanged water to prepare a sample with a resin content of about 1.0%. The volume-based cumulative 50% particle diameter D of the resin particles was measured for this sample using a particle size distribution analyzer that uses dynamic light scattering under the following measurement conditions: 50 The particle size distribution meter used was a Nanotrac WAVEII-Q (manufactured by Microtrac Bell). When particles with a particle size were measured using this measurement method, the resin was determined to be a "resin particle" (a "water-dispersible resin"). On the other hand, when particles with a particle size were not measured using this measurement method, the resin was determined not to be a "resin particle" (a "water-soluble resin"). When measuring the particle size of wax particles, the same procedure as above was carried out except that a liquid containing wax particles was used instead of a liquid containing resin, and the cumulative 50% particle size D based on volume of the wax particles was measured. 50 was measured.

[0136] [Measurement conditions]: SetZero:30s Number of measurements: 3 Measurement time: 120 seconds ·Shape: true spherical

[0137] (Cumulative 50% particle size based on pigment volume) The pigment dispersion was diluted with ion-exchanged water to prepare a sample with a pigment content of about 0.01%. The average particle diameter D of the pigment was measured for this sample using the particle size distribution meter described above under the following measurement conditions. 50 (Cumulative 50% particle size on a volume basis) was measured.

[0138] [Measurement conditions]: SetZero:30s Number of measurements: 3 Measurement time: 120 seconds ·Shape: Non-spherical

[0139] (Confirmation of surface treatment of titanium oxide particles) Using a liquid in which titanium oxide particles were added to nitric acid as a sample, quantitative analysis of aluminum and silicon elements was performed using an inductively coupled plasma (ICP) emission spectrometer. In this case, it was assumed that all atoms covering the surface were in the form of oxides, and the obtained values ​​of aluminum and silicon were converted to the oxides, i.e., alumina and silica, to calculate the mass ratio. In other words, if values ​​for aluminum and silicon were obtained, it means that the surface had been treated with alumina or silica.

[0140] (Melting point of wax particles) The melting point T of a wax made of a single component M The melting point (°C) was measured in accordance with the test method described in 5.3.1 (Melt point test method) of JIS K2235:1991 (petroleum wax). The melting point of a wax (wax mixture) composed of multiple components was measured in accordance with the test method described in 5.3.2 of JIS K2235:1991.

[0141] <Preparation of reaction solution> The components (unit: %) shown in Table 1 were mixed and thoroughly stirred, then pressure filtered through a cellulose acetate filter (Advantec) with a pore size of 3.0 μm to prepare each reaction solution. In Table 1, "Catiomaster PDT-2" is the trade name of an amine-epichlorohydrin condensation polymer aqueous solution (cationic resin content: 60.0%) manufactured by Yokkaichi Chemicals. "Acetylenol E100" is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. "Proxel GXL(S)" is the trade name of a preservative manufactured by Arch Chemicals.

[0142] [Table 1]

[0143] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. 15.0 parts of pigment (carbon black), 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 centrifugal separation 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 15.0% and a resin dispersant (resin 1) content of 4.5%. Cumulative 50% particle size D based on volume of pigment P was 90 nm.

[0144] (Pigment dispersion 2) Except for changing the pigment to CI Pigment Blue 15:3, the same procedure as for Pigment Dispersion 1 described above was used to prepare Pigment Dispersion 2 with a pigment content of 15.0% and a resin dispersant (Resin 1) content of 4.5%. Cumulative 50% particle diameter D based on volume of pigmentP was 120 nm.

[0145] (Pigment dispersion 3) Commercially available rutile-type titanium oxide (product name "TITANIX JR-403", surface treatment: alumina, silica, D P 40.0 parts of 250 nm titanium dioxide, 1.2 parts of 3-(methoxy(polyoxyethylene)9-12)propyltrimethoxysilane, and ion-exchanged water for a total of 100.0 parts of the components were mixed and pre-dispersed using a homogenizer. Then, using 0.5 mm zirconia beads, dispersion treatment was carried out at 25°C for 12 hours using a paint shaker. The zirconia beads were filtered off, and an appropriate amount of ion-exchanged water was added as necessary to prepare pigment dispersion 3 with a titanium dioxide particle content of 40.0%.

[0146] <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, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 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.) were mixed to prepare an emulsion. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over a period of 1 hour, and a polymerization reaction was carried out for 2 hours while stirring. The polymerization temperature was set at 100° C., and the volume-based cumulative 50% particle diameter D E 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 with a resin particle (solid content) content of 25.0%. The volume-based cumulative 50% particle diameter D of resin particles 1 E was 120 nm.

[0147] <Preparation of aqueous dispersion of wax particles> (Water dispersion of wax particles 1 to 6) The components shown in Table 2 were mixed together, and the temperature and pressure were appropriately adjusted to disperse the wax. An appropriate amount of pure water was added to dilute the mixture, to obtain aqueous dispersions of wax particles 1 to 6, each of which had a total wax and dispersant content of 35.0%. In Table 2, polyoxyethylene (10) cetyl ether was used as the nonionic dispersant. Furthermore, ethylene acrylic acid copolymer (acid value: 120 mg KOH / g, weight average molecular weight: 8,000) was used as the anionic dispersant. The melting point T M (℃) and cumulative 50% particle diameter D on a volume basis W The values ​​(nm) are summarized on the right side of Table 2.

[0148] [Table 2]

[0149] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in Tables 3 and 4, thoroughly stirring, and then filtering under pressure with a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm. However, when Pigment Dispersion 3 was used, a cellulose acetate filter (manufactured by Advantech) with a pore size of 5.0 μm was used.

[0150] [Table 3]

[0151] [Table 4]

[0152] <Evaluation> The reaction liquid and the first ink of the types shown in Table 5 were filled in the storage parts communicating with the reaction liquid applying device 1201 and the ink applying device 1202 of the inkjet recording apparatus 100 configured as shown in FIG. 1. The second ink of the types shown in Table 5 was filled in the storage part communicating with the ink applying device 5202 of the inkjet recording apparatus 100 configured as shown in FIG. 1. In all of the examples, comparative examples, and reference examples, the reaction liquid 1 was filled in the storage part communicating with the reaction liquid applying device 5201 of the inkjet recording apparatus 100 configured as shown in FIG. 1. A solid image of 2 cm x 2 cm was recorded using the inkjet recording apparatus 100, in which the recording duty of the reaction liquid was 10% and the recording duty of the first ink was 100%. The time difference between the application of the reaction liquid and the application of the ink was adjusted to 500 milliseconds by adjusting the conveyance degree of the conveying member 1300. As a drying process (air blowing process), hot air having a temperature shown in Table 5 was applied to the recording medium for the time shown in Table 5. Thereafter, a 2 cm x 2 cm solid image was recorded so as to overlap the solid image, with the reaction liquid recording duty being 10% and the second ink recording duty being 100%. In this embodiment, an image recorded under the condition that one 3.0 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%. As the recording medium, a polyethylene terephthalate (PET) film (product name "Ultra-transparent PET film GIY-0305", manufactured by Lintec) was used. In the present invention, in the evaluation criteria for each item below, "AA", "A" and "B" were defined as acceptable levels, and "C" was defined as unacceptable levels. The evaluation results are shown on the right side of Table 5.

[0153] In Table 5, the order of each step is indicated as 1 to 3. The details are shown below. 1: reaction liquid application process → first ink application process → drying process → reaction liquid application process → second ink application process 2: Reaction liquid application process → First ink application process → Reaction liquid application process → Second ink application process 3: First ink application process → reaction liquid application process → drying process → reaction liquid application process → second ink application process

[0154] (Surface abrasion resistance) A friction test was conducted using an abrasion resistance tester (manufactured by Tester Sangyo), which is a friction tester II (Gakushin type) conforming to JIS L0849, and a white friction cloth (cotton) as specified in JIS L0803, by reciprocating the surface of the recorded image up to 300 times with a load of 200g. The image after the friction test was visually inspected and the surface abrasion resistance of the image was evaluated according to the evaluation criteria shown below. The evaluation of surface abrasion resistance assumes a situation in which a certain area is abraded during loading of the recording medium or post-processing, and evaluates the degree of abrasion resistance of the part close to the surface of the image. AA: No scratches were observed on the image even after 300 strokes A: Scratch marks were observed on the image after 300 strokes, but no scratches were observed on the image after 200 strokes. B: Scratch marks were observed on the image after 200 strokes, but no scratches were observed on the image after 100 strokes. C: Scratch marks were observed on the image even after 100 strokes.

[0155] (Nail abrasion resistance) A load of 300g was applied to the image and it was rubbed randomly with a fingernail eight times. The state of the image after rubbing was visually checked and the fingernail abrasion resistance of the image was evaluated according to the following evaluation criteria. The evaluation of fingernail abrasion resistance assumes a situation where the image is rubbed with a sharp object such as a fingernail, and evaluates the degree of abrasion resistance including the inside of the image. AA: Scratch marks were observed in 0 places A: Scratch marks were found in 1 to 2 places B: Scratch marks were found in 3 to 4 places C: Scratch marks were observed in 5 or more places.

[0156] [Table 5]

[0157] In Example 22, an image was recorded under the same evaluation conditions as in Example 1, except that the reaction liquid 1 was not applied before the application of the second ink. The evaluation results of the surface scratch resistance and fingernail scratch resistance were the same as in Example 1, being "AA".

[0158] The disclosure of this embodiment includes the following methods and configurations.

[0159] (Method 1) 1. An inkjet recording method for recording an image on a recording medium by ejecting an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink from a recording head, comprising: the water-based ink includes a first ink and a second ink, a reaction liquid applying step of applying the aqueous reaction liquid to the recording medium; a first ink applying step of applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; a drying step of drying the recording medium; a second ink applying step of applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method 1 / 2 Water absorption up to 10mL / m 2 An inkjet recording method, comprising the steps of:

[0160] (Method 2) The volume-based cumulative 50% particle diameter D of the pigment in the first ink P (nm), the cumulative 50% particle diameter D of the wax based on volume W (nm), and the volume-based cumulative 50% particle diameter D of the resin particles E(nm) satisfies the following formula: D P ≧D W ≧D E

[0161] (Method 3) 3. The inkjet recording method according to claim 1, wherein the total content (mass %) of the wax and the dispersant for dispersing the wax in the first ink is 1.0 mass % or more based on the total mass of the ink.

[0162] (Method 4) 4. The inkjet recording method according to any one of Methods 1 to 3, wherein the second ink further contains a wax and a nonionic dispersant for dispersing the wax.

[0163] (Method 5) The inkjet recording method according to any one of Methods 1 to 4, wherein the content (mass %) of the water-soluble organic solvent having a boiling point of 260° C. or higher in each of the first ink and the second ink is 1.0 mass % or less.

[0164] (Method 6) 6. The inkjet recording method according to any one of Methods 1 to 5, wherein the content (mass %) of the polyvalent metal salt in the aqueous reaction liquid is 10.0 mass % or less based on the total mass of the reaction liquid.

[0165] (Method 7) 7. The inkjet recording method according to any one of Methods 1 to 6, wherein the pigment of the first ink is titanium oxide.

[0166] (Method 8) 8. The inkjet recording method according to any one of Methods 1 to 7, wherein the pigment of the second ink is at least one selected from the group consisting of carbon black and organic pigments.

[0167] (Method 9) 9. The inkjet recording method according to any one of Methods 1 to 8, wherein the polyvalent metal salt in the aqueous reaction liquid is magnesium sulfate.

[0168] (Method 10) 10. The inkjet recording method according to any one of Methods 1 to 9, wherein the aqueous reaction liquid further contains a cationic resin.

[0169] (Method 11) 11. The inkjet recording method according to any one of Methods 1 to 10, wherein the application of the aqueous ink and the aqueous reaction liquid to a unit area of ​​the recording medium is performed by a single relative scan of the recording head and the recording medium.

[0170] (Method 12) the drying step is a blowing step of blowing hot air onto the recording medium to dry it, 12. The inkjet recording method according to any one of Methods 1 to 11, wherein the temperature (° C.) of the hot air in the air blowing step is 60° C. or higher and 90° C. or lower.

[0171] (Configuration 1) An inkjet recording apparatus used for recording an image on a recording medium by ejecting from a recording head an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, the ink comprising: the water-based ink includes a first ink and a second ink, a reaction liquid applying means for applying the aqueous reaction liquid to the recording medium; a first ink applying means for applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; A drying means for drying the recording medium; a second ink applying means for applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method 1 / 2 Water absorption up to 10mL / m 2 1. An inkjet recording apparatus comprising:

[0172] (Configuration 2) A set of an aqueous ink and an aqueous reaction liquid for use in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink are ejected from a recording head to record an image on a recording medium, comprising: the water-based ink includes a first ink and a second ink, the inkjet recording method includes a reaction liquid applying step of applying the aqueous reaction liquid to the recording medium; a first ink applying step of applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; a drying step of drying the recording medium; a second ink applying step of applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method 1 / 2 Water absorption up to 10mL / m 2 A set of an aqueous ink and an aqueous reaction liquid, characterized in that:

Claims

1. 1. An inkjet recording method for recording an image on a recording medium by ejecting an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink from a recording head, comprising: the water-based ink includes a first ink and a second ink, a reaction liquid applying step of applying the aqueous reaction liquid to the recording medium; a first ink applying step of applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; a drying step of drying the recording medium; a second ink applying step of applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ An inkjet recording method, comprising the steps of:

2. A volume-based cumulative 50% particle diameter D of the pigment in the first ink Ｐ (nm), the volume-based cumulative 50% particle diameter D of the wax Ｗ (nm), and the volume-based cumulative 50% particle diameter D Ｅ 2. The ink jet recording method according to claim 1, wherein (nm) satisfies the following formula: D Ｐ ≧D Ｗ ≧D Ｅ

3. The inkjet recording method according to claim 1 , wherein a total content (mass %) of the wax and the dispersant for dispersing the wax in the first ink is 1.0 mass % or more based on the total mass of the ink.

4. 2. The ink jet recording method according to claim 1, wherein the second ink further contains a wax and a nonionic dispersant for dispersing the wax.

5. The inkjet recording method according to claim 1 , wherein the content (mass %) of the water-soluble organic solvent having a boiling point of 260° C. or higher in each of the first ink and the second ink is 1.0 mass % or less.

6. 2. The ink jet recording method according to claim 1, wherein the content (mass %) of the polyvalent metal salt in the aqueous reaction liquid is 10.0 mass % or less based on the total mass of the reaction liquid.

7. 2. The ink jet recording method according to claim 1, wherein the pigment of the first ink is titanium oxide.

8. 2. The ink jet recording method according to claim 1, wherein the pigment of the second ink is at least one selected from the group consisting of carbon black and organic pigments.

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

10. The ink-jet recording method according to claim 1 , wherein the aqueous reaction liquid further contains a cationic resin.

11. 2. The inkjet recording method according to claim 1, wherein the application of the water-based ink and the water-based reactive liquid to the unit area of ​​the recording medium is performed by one relative scan of the recording head and the recording medium.

12. the drying step is a blowing step of blowing hot air onto the recording medium to dry it, 2. The ink jet recording method according to claim 1, wherein the temperature (°C) of the hot air in the air blowing step is 60°C or higher and 90°C or lower.

13. An inkjet recording apparatus used for recording an image on a recording medium by ejecting from a recording head an aqueous reaction liquid containing an aqueous ink and a reactant that reacts with the aqueous ink, the ink comprising: the water-based ink includes a first ink and a second ink, a reaction liquid applying means for applying the aqueous reaction liquid to the recording medium; a first ink applying means for applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; A drying means for drying the recording medium; a second ink applying means for applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ 1. An inkjet recording apparatus comprising:

14. A set of an aqueous ink and an aqueous reaction liquid for use in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink are ejected from a recording head to record an image on a recording medium, comprising: the water-based ink includes a first ink and a second ink, the inkjet recording method includes a reaction liquid applying step of applying the aqueous reaction liquid to the recording medium; a first ink applying step of applying the first ink so as to overlap at least a portion of an area of ​​the recording medium to which the aqueous reaction liquid is applied; a drying step of drying the recording medium; a second ink applying step of applying the second ink so as to overlap at least a part of an area to which the aqueous reaction liquid and the first ink are applied, the first ink contains a pigment, resin particles, wax, and a nonionic dispersant for dispersing the wax; the second ink contains a pigment and resin particles; The aqueous reaction liquid contains a polyvalent metal salt, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ A set of an aqueous ink and an aqueous reaction liquid, characterized in that:

Images