Inkjet recording method, inkjet recording device, and ink set

Abstract

To provide an inkjet recording method which can record an image excellent in scratch resistance, and is excellent in discharge stability of ink from a recording head.SOLUTION: An inkjet recording method discharges first ink and second ink from an inkjet type recording head and records an image on a recording medium, so that a region to which the first ink is imparted and a region to which the second ink is imparted are at least partially overlapped with each other, wherein the first ink contains a halogenated phthalocyanine pigment, a content (mass%) of wax particles in the first ink is 0 mass% or more and 0.01 mass% or less based on the first ink total mass, the second ink contains a pigment other than the halogenated phthalocyanine pigment, and a content (mass%) of wax particles in the second ink exceeds 0.01 mass% based on the second ink total mass.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] An inkjet recording device ejects minute ink droplets from nozzles of a recording head to record an image on a recording medium. Ink comes in colors such as black, cyan, magenta, and yellow, and in order to express a wide range of colors, ink droplets of these different colors are overlapped to record. One method for improving the scratch resistance of the image thus obtained is known to be adding wax to the ink. Patent Document 1 describes an ink set in which wax is added as a gelling agent to inks of various colors, such as a green ink containing a pigment having a copper phthalocyanine structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 200031 Summary of the Invention [Problem to be solved by the invention]

[0004] According to the study by the present inventors, even when using the wax described in Patent Document 1, the dispersion stability of the wax or the dispersion stability of the pigment due to the influence of the wax may decrease depending on the ink components, resulting in a decrease in ejection stability from the recording head. In particular, it was found that the decrease in the ejection stability of the ink becomes more significant when the wax is used together with a halogenated phthalocyanine pigment, which is often used as a coloring material for green ink.

[0005] Therefore, an object of the present invention is to provide an inkjet recording method using an ink containing a halogenated phthalocyanine pigment and an ink containing a pigment other than the halogenated phthalocyanine pigment, which can record an image having excellent abrasion resistance and has excellent ink ejection stability from a recording head. Another object of the present invention is to provide an inkjet recording apparatus and an ink set for use in the inkjet recording method. [Means for solving the problem]

[0006] That is, according to the present invention, there is provided an inkjet recording method for ejecting the first ink and the second ink from an inkjet recording head to record an image on a recording medium so that an area to which the first ink is applied and an area to which the second ink is applied at least partially overlap, the inkjet recording method being characterized in that the first ink contains a halogenated phthalocyanine pigment, and the content (mass %) of wax particles in the first ink is 0 mass % or more and 0.01 mass % or less based on the total mass of the first ink, and the second ink contains a pigment other than the halogenated phthalocyanine pigment, and the content (mass %) of wax particles in the second ink exceeds 0.01 mass % based on the total mass of the second ink. Effect of the Invention

[0007] According to the present invention, in an inkjet recording method using an ink containing a halogenated phthalocyanine pigment and an ink containing a pigment other than the halogenated phthalocyanine pigment, it is possible to provide an inkjet recording method capable of recording an image having excellent abrasion resistance and excellent ink ejection stability from a recording head. Also, according to the present invention, it is possible to provide an inkjet recording apparatus and an ink set used in this inkjet recording method. [Brief description of the drawings]

[0008] [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

[0009] 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.

[0010] The present inventors have investigated the fact that the ejection stability from a recording head decreases when a halogenated phthalocyanine pigment and wax particles are used. As a result, it is considered that this is because, among the dispersion component and polar component that constitute the surface free energy of the halogenated phthalocyanine pigment, the polar component in particular is smaller than that of pigments of other colors, and therefore the halogenated phthalocyanine pigment has the characteristic of easily adsorbing a dispersant that disperses wax particles. Thus, with inks containing halogenated phthalocyanine pigments, it is difficult to achieve both abrasion resistance and ejection stability.

[0011] The present inventors have therefore conducted research and found that the following configuration can achieve both abrasion resistance and ejection stability, and have arrived at the present invention. First, even if the first ink contains a halogenated phthalocyanine pigment, the content of wax particles can be set to 0% by mass or more and 0.01% by mass or less based on the total mass of the first ink, thereby suppressing a decrease in ejection stability. Furthermore, it has been found that the abrasion resistance of an image can be improved by applying to a recording medium this first ink and a second ink containing a pigment other than a halogenated phthalocyanine pigment and wax particles exceeding 0.01% by mass based on the total mass of the ink so as to overlap at least partially. The presence of wax particles near the surface of an image improves the abrasion resistance, but the reason that this does not depend on the order in which the inks are applied is thought to be because wax has a small specific gravity and is easily moved to the vicinity of the surface during drying of the ink.

[0012] As explained above, the effects of the present invention can be achieved by the synergistic effects of the various components.

[0013] <Inkjet recording method, inkjet recording apparatus, and ink set> The inkjet recording method (hereinafter also simply referred to as "recording method") of the present invention has the following characteristics. It is an inkjet recording method in which the first ink and the second ink are ejected from an inkjet recording head to record an image on a recording medium such that an area to which the first ink is applied and an area to which the second ink is applied at least partially overlap. The first ink contains a halogenated phthalocyanine pigment, and the content (mass%) of wax particles in the first ink is 0% by mass or more and 0.01% by mass or less based on the total mass of the ink. The second ink contains a pigment other than the halogenated phthalocyanine pigment, and the content (mass%) of wax particles in the second ink exceeds 0.01% by mass based on the total mass of the ink.

[0014] The inkjet recording apparatus (hereinafter, also simply referred to as "recording apparatus") of the present invention has the following features. The inkjet recording apparatus uses an inkjet recording method in which the first ink and the second ink are ejected from an inkjet recording head to record an image on a recording medium such that an area to which the first ink is applied and an area to which the second ink is applied at least partially overlap. The first ink contains a halogenated phthalocyanine pigment, and the content (mass%) of wax particles in the first ink is 0% by mass or more and 0.01% by mass or less based on the total mass of the ink. The second ink contains a pigment other than the halogenated phthalocyanine pigment, and the content (mass%) of wax particles in the second ink exceeds 0.01% by mass based on the total mass of the ink.

[0015] The ink set of the present invention has the following characteristics. The ink set uses an inkjet recording method in which the first ink and the second ink are ejected from an inkjet recording head to record an image on a recording medium such that an area to which the first ink is applied and an area to which the second ink is applied at least partially overlap. The first ink contains a halogenated phthalocyanine pigment, and the content of wax particles in the first ink is 0% by mass or more and 0.01% by mass or less based on the total mass of the ink. The second ink contains a pigment other than the halogenated phthalocyanine pigment, and the content of wax particles in the second ink exceeds 0.01% by mass based on the total mass of the ink.

[0016] (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.

[0017] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured to include a recording unit 1000, a heating unit 2000, a fixing unit 3000, a cooling unit 4000, an inverting unit 5000, and a paper discharge unit 6000. In the recording unit 1000, various liquids including ink are applied by a liquid application unit 1200 to a recording medium 1100 conveyed from a paper feed unit 1400 by a conveying member 1300. In the heating unit 2000, the liquid applied to the recording medium 1100 is heated by a heating unit 2100, and volatile components such as water in the liquid are evaporated and dried. In the fixing unit 3000, a fixing member 3100 is brought into contact with the area of ​​the recording medium 1100 to which the liquid has been applied, and heated to promote fixing of the image to the recording medium 1100. The recording medium 1100 is then cooled by a cooling member 4100 of the cooling unit 4000. When an image is to be recorded on the back side following the front side (recording surface), the recording medium 1100 is first inverted by an inversion device 5100 of an inversion section 5000. Next, an image is recorded on the back side in the same manner as the front side, and then the recording medium is transported by a transport member 6100 of a paper discharge section 6000 and stacked and stored in a recording medium storage section 6200.

[0018] Any recording medium may be used as the recording medium 1100. For example, recording media having ink absorbency (permeability) such as recording media without a coating layer, such as plain paper, uncoated paper, and synthetic paper, and recording media with a coating layer, such as printing paper, glossy paper, and art paper, may be used. In addition, recording media having no permeability, such as films or sheets made of resin materials such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), may be used. The basis weight (g / m2) of the recording medium 1100 may be determined by the following formula: 2 ) is 30g / m 2 More than 500g / m 2 It is preferable that the thickness is less than 50 g / m 2 More than 450g / m 2 It is even more preferable that:

[0019] [Recording Section] The recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a reaction liquid applying device 1201 and an ink applying device 1202. The reaction liquid applying device 1201 shown in FIG. 1 is an example of a unit using an inkjet type ejection head. In addition, 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 it can come into contact with the ink on the recording medium 1100. However, in order to record high-quality images on various recording media having different liquid absorption characteristics, it is preferable to apply the reaction liquid before the ink is applied. An inkjet type 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 can be exemplified by 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.

[0020] 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.

[0021] 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".

[0022] Furthermore, the first ink and the second ink are applied to the recording medium so that they at least partially overlap, but the order of application does not matter. This is because the wax particles in the ink have a low specific gravity, and so regardless of the depth of the ink layer that constitutes the image, the wax particles will move toward the surface when the ink dries. However, regardless of the influence of drying conditions, in order to have many wax particles present on the surface of the ink layer that constitutes the image and to improve abrasion resistance, it is preferable to apply the second ink, which contains a higher amount of wax particles, after applying the first ink. In other words, it is preferable to apply the first ink and the second ink to the recording medium in this order.

[0023] Furthermore, the mass ratio of the amounts of the first ink and the second ink applied per unit area of ​​the recording medium (amount of the first ink applied:amount of the second ink applied) is preferably 9.5:0.5 to 4.5:5.5. This is because if the ratio of the amount of the second ink applied is 9.5:0.5 to 4.5:5.5, the abrasion resistance is improved without impairing the color development of the first ink. By having the mass ratio of the amount of the first ink applied to the amount of the second ink applied within the above range, it is possible to achieve both abrasion resistance and color development at a higher level.

[0024] 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.

[0025] 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.

[0026] [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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] [Transport system] As shown in FIG. 1, the recording unit 1000 is configured to include a liquid applying device 1200 and a conveying member 1300 that conveys the recording medium 1100. The liquid applying device 1200 applies a reaction liquid and ink to a desired position of the recording medium 1100 conveyed by the conveying member 1300. Each liquid applying device 1200 receives an image signal of recording data and applies the necessary reaction liquid and ink to each position. FIG. 1 shows the conveying member 1300 in the form of a conveying belt, but a spur, a conveying drum, or the like may be used as long as it has the function of conveying the recording medium 1100. In order to improve the conveying accuracy, a material that can fix the recording medium 1100 can be used as the conveying member 1300. Specifically, a method of providing a hole in the conveying member 1300 and fixing the recording medium 1100 by sucking from the back side, a method of forming the conveying member 1300 from an appropriate material and fixing the recording medium 1100 by electrostatic adsorption, etc. can be mentioned.

[0031] [Heating section] As shown in Fig. 1, the heating section 2000 is configured to include a heating device 2100 and a transport member 2200. The recording medium 1100, to which the reaction liquid and ink have been applied and an image has been recorded, is heated by the heating device 2100 while being transported by the transport member 2200, thereby evaporating and drying the liquid components of the image. It is preferable to further include a drying step between the ink application step and the fixing step, in which the recording medium to which the ink has been applied is heated in a non-contact manner to dry the ink. By including such a drying step, deformation (cockling and curling) of the recording medium 1100 can be effectively suppressed.

[0032] The heating device 2100 may have any configuration as long as it can heat the recording medium 1100, and various conventionally known devices such as a hot air dryer and a heater can be used. Among them, the use of a non-contact heater such as an electric heating wire or infrared heater is preferable from the standpoint of safety and energy efficiency. In addition, if a mechanism for blowing hot air with a built-in fan for spraying heated gas onto the recording medium 1100 is used, the drying efficiency can be easily improved.

[0033] 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.

[0034] The heating temperature is preferably set so as to quickly evaporate the liquid components and not to over-dry the recording medium 1100 in terms of suppressing deformation of the recording medium. The temperature of the drying means can be set so that the recording medium reaches a desired temperature, taking into consideration the conveying speed and the environmental temperature. Specifically, the temperature of the drying means (such as hot air) is preferably set to 40°C or higher and 100°C or lower, and more preferably 60°C or higher and 80°C or lower. In addition, when the recording medium 1100 is heated by blowing heated gas, the wind speed is preferably set to 1 m / s or higher and 100 m / s or lower. The temperature of the wind such as the hot air can be measured using a K-type thermocouple thermometer. A specific measuring device can be, for example, the product name "AD-5605H" (manufactured by A&D).

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] [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 on the recording medium 1100 and the fixing member 3100 come into close contact with each other, and the image is fixed on the recording medium 1100. When a liquid such as ink containing resin particles and coloring material is used, the resin particles are softened and form a film mainly by heating in the fixing unit 3000 , and the coloring material can be bound onto the recording medium 1100 .

[0040] 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.).

[0041] When the ink contains resin particles, if the temperature of the fixing member 3100 is set to a temperature equal to or higher than the glass transition temperature of the resin particles in the ink, the resin particles soften and are more likely to form a film, improving the scratch resistance of the image. 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.

[0042] The nip pressure of the fixing member 3100 and the conveying member 3200, i.e., the pressure applied to the recording medium when it passes through the contact-type heating and pressing mechanism, is preferably 10 Pa to 1,000 Pa, more preferably 10 Pa to 500 Pa. Also, 10 Pa to 400 Pa is particularly preferable.

[0043] 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.

[0044] 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.

[0045] [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).

[0046] [Inverted part] When performing double-sided recording, the recording medium 1100 is inverted using the inversion unit 5000 (FIG. 1). The recording medium 1100 with an image recorded on its recording surface (front side) passes through the cooling unit 4000, is branched and transported, and is inverted by the inversion device 5100. The inverted recording medium 1100 is transported to the paper feeder 1400 of the recording unit 1000 with liquid applied to its back side (the side opposite to the recording surface (front side)).

[0047] [Paper output section] After the image is recorded, the recording medium 1100 is stored in a paper discharge section 6000 (FIG. 1). After single-sided or double-sided recording is performed, the recording medium 1100 passes through the cooling section 4000, is transported by a transport member 6100, and is finally stored in a stacked state in a recording medium storage section 6200. Two or more recording medium storage sections 6200 may be provided to store different recorded materials, etc.

[0048] (Reaction solution) The recording method of the present invention preferably further comprises a reaction liquid application step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink to the recording medium prior to the ink application step. Each component used in the reaction liquid will be described in detail below.

[0049] [Reactants] The reaction liquid reacts with the ink when it comes into contact with the ink, and aggregates the components in the ink (components having anionic groups, such as resins, surfactants, and self-dispersing pigments), and contains a reactant. The presence of the reactant destabilizes the state of the components having anionic groups in the ink when the ink and the reactant come into contact with each other on the recording medium, and can promote the aggregation of the ink. Examples of the reactant include cationic components such as polyvalent metal ions and cationic resins, and organic acids.

[0050] The reactants may be used alone or in combination of two or more.

[0051] 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 - In the case where a polyvalent metal ion is used as a reactant, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.0 mass% or more and 20.0 mass% or less based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of the polyvalent metal salt" in the reaction solution means the "content (mass%) of the anhydride of the polyvalent metal salt" excluding water as the hydrate.

[0052] 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.

[0053] 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.

[0054] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. The aqueous medium used in the reaction liquid can be the same as the aqueous medium that can be contained in the ink described later. The aqueous medium used in the reaction liquid can contain the water-soluble organic solvent that can be contained in the ink described later. The content (mass%) of the water-soluble organic solvent in the reaction liquid is preferably 1.0 mass% or more and 45.0 mass% or less based on the total mass of the reaction liquid. The water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound described later. The content (mass%) of the water-soluble hydrocarbon compound in the reaction liquid is preferably 1.0 mass% or more and 20.0 mass% or less based on the total mass of the reaction liquid. In addition, the content (mass%) of water in the reaction liquid is preferably 50.0 mass% or more and 95.0 mass% or less based on the total mass of the reaction liquid.

[0055] [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.

[0056] [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.

[0057] (ink) The inks used in the recording method of the present invention are a first ink containing a halogenated phthalocyanine pigment and wax particles in an amount of 0% by mass or more and 0.01% by mass or less based on the total mass of the first ink, and a second ink containing a pigment other than a halogenated phthalocyanine pigment and wax particles in an amount of more than 0.01% by mass based on the total mass of the second ink. Both the first ink and the second ink are water-based inks for inkjet printing. The components used in the first ink and the second ink are described in detail below. Hereinafter, when the term "ink" is simply used, it is understood to refer to both the "first ink" and the "second ink".

[0058] [Colorant] The first ink contains a halogenated phthalocyanine pigment as a coloring material. This is because this pigment is more likely to cause dispersion instability of wax particles when wax particles are added than other pigments. Specific examples of halogenated phthalocyanine pigments include CI Pigment Green 7, CI Pigment Green 36, CI Pigment Green 37, and CI Pigment Green 58. Among the above, from the viewpoint of ejection stability and color development, the halogenated phthalocyanine pigment is preferably at least one selected from the group consisting of CI Pigment Green 7, CI Pigment Green 36, and CI Pigment Green 58. Furthermore, it is more preferable that the halogenated phthalocyanine pigment is at least one selected from the group consisting of Pigment Green 7 and CI Pigment Green 36.

[0059] The second ink contains a pigment other than the halogenated phthalocyanine pigment (i.e., a pigment different from the halogenated phthalocyanine pigment) as a coloring material. This is because the first ink cannot contain sufficient wax particles for scratch resistance, and the second ink uses a pigment that can contain wax particles to compensate for this. Specific examples of pigments other than the halogenated phthalocyanine pigment contained in the second ink include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo pigments, non-halogenated phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, imidazolone pigments, diketopyrrolopyrrole pigments, and dioxazine pigments.

[0060] The second ink may be of one type or of two or more types.

[0061] When it is desired to express a green color tone with high saturation using the first ink and the second ink, it is preferable to use a pigment having a coloring property in the cyan region (cyan pigment) or a pigment having a coloring property in the yellow region (yellow pigment) as the pigment contained in the second ink. In this case, it is more preferable that the pigment contained in the second ink is at least one selected from the group consisting of non-halogenated phthalocyanine pigments and azo pigments. It is further preferable that the pigment contained in the second ink is at least one selected from the group consisting of CI Pigment Blue 15:3 and CI Pigment Yellow 74. In this case, when there is one type of second ink, it is preferable that the second ink is an ink containing at least one of a cyan pigment and a yellow pigment. In addition, when there are two or more types of second inks, it is preferable that the second ink contains at least one of an ink containing a cyan pigment and an ink containing a yellow pigment.

[0062] In addition, when it is desired to express a green tone with low saturation using the first ink and the second ink, it is preferable to use a pigment having color development in the black region (black pigment) or a pigment having color development in the magenta region (magenta pigment) as the pigment contained in the second ink. In this case, when there is one type of second ink, it is preferable that the second ink is an ink containing at least one of a black pigment and a magenta pigment. In particular, it is more preferable that the pigment contained in the second ink is at least one selected from the group consisting of carbon black, quinacridone pigment, and azo pigment. It is further preferable that the pigment contained in the second ink is at least one selected from the group consisting of carbon black, Pigment Red 122, and Pigment Red 150. In addition, when there are two or more types of second ink, it is preferable that the second ink contains at least one of an ink containing a black pigment and an ink containing a magenta pigment.

[0063] The content (mass %) of the coloring material in the ink is preferably from 0.5 to 15.0% by mass, and more preferably from 1.0 to 10.0% by mass, based on the total mass of the ink.

[0064] 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.

[0065] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin having an anionic group can be used, and a resin as described below, especially a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0066] 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.

[0067] [resin] The ink can contain a resin. By using an ink containing a resin, an image with improved scratch resistance can be recorded. The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary.

[0068] Also, (ii) pigments can be added to the ink to improve various properties of the recorded image.

[0069] The content (mass %) of the resin in the ink is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 0.5% by mass or more and 15.0% by mass or less, based on the total mass of the ink. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin may be used alone or in combination of two or more kinds.

[0070] [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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution.

[0075] When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, and measurement time: 180 seconds. In addition, a particle size analyzer using dynamic light scattering (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as the particle size distribution measuring device.

[0076] Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0077] 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.

[0078] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, and more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D 50 ) is preferably 50 nm or more and 500 nm or less. The volume-based cumulative 50% particle diameter of the resin particles is the diameter of the particles that is 50% of the total volume of the measured particles when integrated from the small particle diameter side in a particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above. The glass transition temperature of the resin particles is preferably 40° C. or more and 120° C. or less, and more preferably 50° C. or more and 100° C. or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not need to contain a coloring material.

[0079] [Wax particles] The ink may contain particles formed from wax (wax particles).

[0080] The content (mass%) of wax particles in the first ink is 0% by mass or more and 0.01% by mass or less based on the total mass of the first ink, and the content (mass%) of wax particles in the second ink is more than 0.01% by mass based on the total mass of the second ink. As a result, the first ink cannot contain more than 0.01% by mass of wax particles due to the reason of ejection stability, but the second ink contains wax particles in an amount that compensates for this, so that an image with excellent abrasion resistance can be recorded. Furthermore, in order to improve the ejection stability of the first ink, the content (mass%) of wax particles in the first ink is preferably 0% by mass based on the total mass of the ink (i.e., the first ink does not contain wax particles). In addition, in order to improve the abrasion resistance, the content (mass%) of wax particles in the second ink is preferably 0.5% by mass or more based on the total mass of the ink. In addition, there is no particular limit on the upper limit of the content of wax particles in the second ink, but it can be, for example, 10.0% by mass or less.

[0081] In addition, the content (mass%) of the wax particles in the second ink is preferably 0.3 to 2.2 times the content (mass%) of the pigment in the second ink in terms of mass ratio. By setting the content of the wax particles in the above range, it is possible to achieve high levels of both improved abrasion resistance, improved ink ejection stability, and improved color development of the image.

[0082] 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).

[0083] 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.

[0084] 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.

[0085] When the ink contains wax particles, the wax particles are preferably dispersed in the ink by a dispersant. As the dispersant for dispersing the wax in the ink, a dispersant such as a surfactant or a resin can be used. Among them, the dispersant is preferably an anionic dispersant or a nonionic dispersant. It is particularly preferable to use an anionic dispersant and a nonionic dispersant in combination.

[0086] Examples of the anionic dispersant include surfactants such as carboxylates, sulfonates, sulfates, and phosphates, and resins having anionic functional groups such as ethylene-acrylic acid copolymers. Among the above anionic dispersants, it is preferable to use ethylene-acrylic acid copolymers from the viewpoint of dispersion stability.

[0087] Nonionic dispersants include polyoxyethylene alkyl ether dispersants (general formula: RO-(C2H4O) n -H), polyoxypropylene alkyl ether dispersant (general formula: RO-(C3H6O) n-H), and polyoxyethylene polyoxypropylene alkyl ether dispersants (general formula: RO-[(C2H4O) m -(C3H6O) n ]-H) and other polyoxyalkylene alkyl ether dispersants.

[0088] Examples of polyoxyethylene alkyl ether dispersants 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.

[0089] Examples of polyoxypropylene alkyl ether dispersants include polyoxypropylene butyl ether, polyoxypropylene myristyl ether, polyoxypropylene cetyl ether, and polyoxypropylene stearyl ether.

[0090] Examples of polyoxyethylene polyoxypropylene alkyl ether dispersants include polyoxyethylene polyoxypropylene butyl ether, polyoxyethylene polyoxypropylene lauryl ether, polyoxyethylene polyoxypropylene cetyl ether, and polyoxyethylene polyoxypropylene stearyl ether.

[0091] The content (mass%) of the dispersant in the ink is preferably 0.5% by mass or less based on the content (mass%) of the wax contained in the wax particles in the ink. By making the content of the dispersant 0.5% by mass or less, the scratch resistance of the image can be further improved. There is no particular lower limit for the content (mass%) of the dispersant in the ink, but it can be, for example, 0.01% by mass or more.

[0092] [Aqueous medium] The ink used in the recording method of the present invention is an aqueous ink containing at least water as an aqueous medium. The ink can 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.

[0093] [Water-soluble hydrocarbon compounds] The water-soluble organic solvent contained in the ink preferably contains a specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain having three or more carbon atoms substituted with two or more hydrophilic groups selected from the group consisting of hydroxyl groups, amino groups, and anionic groups. However, the hydrocarbon chain may be interrupted by a sulfonyl group or an ether group. When the hydrocarbon chain has three or four carbon atoms, the hydrophilic group contains an anionic group, or the hydrocarbon chain is interrupted by a sulfonyl group.

[0094] 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.

[0095] 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.

[0096] [Other ingredients] The ink may contain various other components as necessary. Examples of other components include various additives such as defoamers, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the ink does not contain a reactant to be contained in the reaction liquid.

[0097] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0098] In addition, it is preferable that the absolute value of the difference in hue angle between the first ink and the second ink is 100° or less. This is because the range of expressible colors is expanded by adding the second ink to the color of the first ink, and the color gamut is increased. There is no particular limit to the lower limit of the absolute value of the difference in hue angle between the first ink and the second ink, but it can be, for example, 5° or more. The hue angle can be measured by a general spectrophotometer, and the measurement target can be, for example, an aqueous solution in which the ink is diluted 2000 times by mass. In addition, when there are two or more types of second ink, the absolute value of the difference in hue angle can be measured in the same manner as when there is one type of second ink, except that the second ink is a mixture of two or more types of ink. EXAMPLES

[0099] 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.

[0100] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. A mixture was obtained by mixing 10.0 parts of a pigment (CI Pigment Green 7, described as "PG7" in Table 1), 15.0 parts of the aqueous solution of resin 1, and 75.0 parts of pure water. 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.

[0101] After centrifuging to remove coarse particles, the mixture was filtered under pressure using a cellulose acetate filter (Advantec) with a pore size of 3.0 μm to prepare Pigment Dispersion 1 with a pigment content of 10.0% and a resin dispersant (Resin 1) content of 3.0%.

[0102] (Pigment dispersion 2) Pigment dispersion 2 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Green 36 (referred to as "PG36" in Table 1). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0103] (Pigment dispersion 3) Pigment dispersion 3 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Green 58 (referred to as "PG58" in Table 1). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0104] (Pigment Dispersion 4) Pigment dispersion 4 was prepared with a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0% in the same manner as for pigment dispersion 1, except that the pigment was changed to CI Pigment Green 24 (referred to as "PG24" in Table 1). Note that CI Pigment Green 24 is not a halogenated phthalocyanine pigment.

[0105] (Pigment Dispersion 5) Pigment dispersion 5 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Blue 15:3 (referred to as "PB15:3" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0106] (Pigment Dispersion 6) Pigment dispersion 6 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 74 (referred to as "PY74" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0107] (Pigment Dispersion 7) Pigment Dispersion 7 was prepared using the same procedure as for Pigment Dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 155 (referred to as "PY155" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (Resin 1) content was 3.0%.

[0108] (Pigment Dispersion 8) Pigment dispersion 8 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to carbon black (referred to as "CB" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0109] (Pigment Dispersion 9) Pigment dispersion 9 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 150 (referred to as "PR150" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0110] (Pigment Dispersion 10) Pigment dispersion 10 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 122 (referred to as "PR122" in Tables 2 and 3). The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0111] <Preparation of wax particles> (Dispersion of wax particles 1) A copolymer of ethylene and acrylic acid was synthesized by a conventional method, neutralized with a neutralizing agent of equimolar amount to the acid value, and an appropriate amount of ion-exchanged water was added to prepare an aqueous solution of an anionic dispersant with a 20.0% content of ethylene-acrylic acid copolymer as a dispersant. The acid value of the dispersant was 120mgKOH / g and the weight average molecular weight was 8000.

[0112] 14.0 parts of polyethylene wax, 14.0 parts of oxidized polyethylene wax, and 11.2 parts of dispersant were mixed, and the temperature and pressure were appropriately adjusted to obtain wax particles. An appropriate amount of pure water was further added to prepare a dispersion of wax particles 1 with a wax particle content (total of the wax content and the dispersant content) of 35.0%.

[0113] (Dispersion of wax particles 2) A dispersion liquid of wax particles 2 was prepared in the same manner as the dispersion liquid of wax particles 1 described above, except that the amount of the dispersant was changed to 2.8 parts.

[0114] (Dispersion of wax particles 3) A dispersion of wax particles 3 was prepared in the same manner as the dispersion of wax particles 1 described above, except that the amount of the dispersant was changed to 14.0 parts.

[0115] (Dispersion of wax particles 4) A dispersion of wax particles 4 was prepared in the same manner as for the dispersion of wax particles 1 described above, except that the amount of the dispersant was changed to 16.8 parts.

[0116] (Dispersion of wax particles 5) A dispersion liquid of wax particles 5 was prepared in the same manner as the dispersion liquid of wax particles 1 described above, except that the dispersant was changed from ethylene-acrylic acid copolymer to polyoxyethylene cetyl ether.

[0117] (Dispersion of wax particles 6) A dispersion of wax particles 6 was prepared in the same manner as the dispersion of wax particles 1 described above, except that the dispersant was changed from ethylene-acrylic acid copolymer to a mixture of 9.0 parts of ethylene-acrylic acid copolymer and 2.2 parts of polyoxyethylene cetyl ether.

[0118] <Preparation of resin particles> (Dispersion of 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 1 hour, and a polymerization reaction was carried out for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion of resin particles 1 with a resin particle (solid content) content of 25.0%.

[0119] <Preparation of the first ink and the second ink> The components (unit: %) shown in Tables 1 to 3 were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare each of the first inks and each of the second inks. "Acetylenol E100" is the trade name of a surfactant manufactured by Kawaken Fine Chemicals, and "Proxel GXL(S)" is the trade name of a preservative manufactured by Lonza.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Table 3]

[0123] <Evaluation> An inkjet recording apparatus 100 having the configuration shown in FIG. 1 was used to record an image on a recording medium according to the evaluation conditions shown in Table 4. Regarding the ink application order No. in Table 3, No. 1 represents the "order in which the first ink is applied and then the second ink is applied," and conversely, No. 2 represents the "order in which the second ink is applied and then the first ink is applied." In addition, as in Examples 6 to 10, when two types of ink (inks 8 and 9) were used as the second ink, the same amount of each was used so that the total amount of the applied second ink was the amount of the applied second ink. At this time, the two types of second ink were applied to the recording medium in the order of a yellow ink (ink 9) containing a yellow pigment and a cyan ink (ink 8) containing a cyan pigment. Art paper (Gloss PW8K, manufactured by Lintec) was used as the recording medium. In the inkjet recording apparatus 1 of this embodiment, an image recorded under the condition that one ink droplet of 3.0 ng is applied to a unit area of ​​1 / 1200 inch x 1 / 1200 inch is defined as having a recording duty of 100%. In the present invention, in the evaluation criteria for each of the following items, "AA", "A" and "B" were defined as acceptable levels, and "C" was defined as an unacceptable level. The evaluation results are shown on the right side of Table 4.

[0124] (Discharge stability) For the first ink, a 20 cm x 900 cm solid image with a print duty of 100% was printed on a print medium, and then a nozzle check pattern was printed on one sheet. The obtained nozzle check pattern was visually observed, and the ejection stability of the first ink was evaluated according to the following evaluation criteria. The second ink was also evaluated in the same manner. AA: The nozzle check pattern was printed correctly. A: The nozzle check pattern had slight distortion, but the lines were continuous. B: The nozzle check pattern was slightly distorted and some of the lines were missing. C: The nozzle check pattern was noticeably distorted and there were also non-ejections. (Abrasion resistance) A 20 cm x 20 cm solid image was recorded on a recording medium with a recording duty of 100% for the first ink and the second ink combined, so that the application rate ratio of the first ink to the second ink was as shown in Table 4. The evaluation image that had been dried using the inkjet recording device 1 was left for a further hour, and then rubbed eight times at different locations with a fingernail under a load of 600 g. The condition of scratches on the evaluation image was visually observed, and the abrasion resistance was evaluated according to the following evaluation criteria. AA: There were no visible scratches on the surface of the recording medium. A: There are 1-2 scratches that expose the surface of the recording medium. B: There are 3 to 4 scratches that expose the surface of the recording medium. C: There are five or more scratches that expose the surface of the recording medium. (Color development) A solid image with a print duty of 200% using only the first ink and a solid image with a print duty of 100% combining the first and second inks such that the application rate ratio of the first and second inks is shown in Table 4 were recorded on a recording medium. The evaluation images that had been dried using the inkjet recording apparatus 1 were left for an additional hour. The L of the two types of evaluation images was measured using a fluorescence spectrodensitometer (FD-7, manufactured by Konica Minolta). * , a * , b * were measured, where L * , a * , b * is the L standard defined by the CIE (International Commission on Illumination). * a * b * The values ​​are for the display system. The measurements for an image using only the first ink are L1 * , a1 * , b1 * , the measurements of the image using the first ink and the second ink are L2 * , a2 * , b2 * The measurement conditions were a light source D50 and a viewing angle of 2°. From the measured values, the color difference ΔE={(L1 * -L2 * ) 2 +(a1 * -a2 * )2 +(b1 * -b2 * ) 2} 1 / 2 The color development was evaluated according to the following evaluation criteria. AA: ΔE is less than 20 A: ΔE is 20 or more and less than 40 B: ΔE is 40 or more

[0125] [Table 4]

Claims

1. an inkjet recording method for recording an image on a recording medium by ejecting a first ink and a second ink from an inkjet recording head such that an area to which a first ink is applied and an area to which a second ink is applied at least partially overlap each other, the method comprising: the first ink contains a halogenated phthalocyanine pigment, and a content (mass %) of wax particles in the first ink is 0 mass % or more and 0.01 mass % or less based on a total mass of the first ink; an ink jet recording method, characterized in that the second ink contains a pigment other than a halogenated phthalocyanine pigment, and the content (mass %) of wax particles in the second ink exceeds 0.01 mass % based on the total mass of the second ink.

2. 2. The ink jet recording method according to claim 1, wherein the first ink and the second ink are applied to the recording medium in this order.

3. The ink jet recording method according to claim 1, wherein a content (mass %) of the wax particles in the second ink is 0.5 mass % or more based on the total mass of the ink.

4. 2. The inkjet recording method according to claim 1, wherein the content (mass %) of the wax particles in the second ink is 0.3 to 2.2 times the content (mass %) of the pigment in the second ink in terms of mass ratio.

5. 2. The ink jet recording method according to claim 1, wherein the wax particles in the second ink are dispersed by a dispersant.

6. The ink-jet recording method according to claim 5, wherein the dispersant contains an ethylene-acrylic acid copolymer.

7. 6. The inkjet recording method according to claim 5, wherein the content (mass %) of the dispersant in the second ink is 0.5 mass % or less based on the content (mass %) of the wax contained in the wax particles in the second ink.

8. 2. The ink jet recording method according to claim 1, wherein an absolute value of a difference in hue angle between the first ink and the second ink is 100° or less.

9. 2. The ink-jet recording method according to claim 1, wherein the pigment other than the halogenated phthalocyanine pigment in the second ink is at least one selected from the group consisting of C. I. Pigment Blue 15:3 and C. I. Pigment Yellow 74.

10. 2. The ink-jet recording method according to claim 1, wherein the halogenated phthalocyanine pigment in the first ink is at least one selected from the group consisting of C. I. Pigment Green 7, C. I. Pigment Green 36, and C. I. Pigment Green 58.

11. 2. The ink-jet recording method according to claim 1, wherein the halogenated phthalocyanine pigment in the first ink is at least one selected from the group consisting of C. I. Pigment Green 7 and C. I. Pigment Green 36.

12. an inkjet recording apparatus using an inkjet recording method for recording an image on a recording medium by ejecting a first ink and a second ink from an inkjet recording head such that an area to which a first ink is applied and an area to which a second ink is applied at least partially overlap each other, the first ink contains a halogenated phthalocyanine pigment, and a content (mass %) of wax particles in the first ink is 0 mass % or more and 0.01 mass % or less based on a total mass of the first ink; an ink jet recording apparatus, characterized in that the second ink contains a pigment other than a halogenated phthalocyanine pigment, and the content (mass %) of wax particles in the second ink exceeds 0.01 mass % based on the total mass of the second ink.

13. an ink set for use in an ink jet recording method in which the first ink and the second ink are ejected from an ink jet recording head to record an image on a recording medium such that an area to which the first ink is applied and an area to which the second ink is applied at least partially overlap each other, the first ink contains a halogenated phthalocyanine pigment, and a content of wax particles in the first ink is 0% by mass or more and 0.01% by mass or less based on a total mass of the first ink; an ink set comprising: a second ink containing a pigment other than the halogenated phthalocyanine pigment; and a content of wax particles in the second ink exceeding 0.01% by mass based on the total mass of the second ink.

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