Inkjet recording method, inkjet recording device and aqueous ink

Abstract

To provide an inkjet recording method capable of suppressing cockling of a recording medium having ink absorption property, and recording an image having excellent fastness.SOLUTION: There is provided an inkjet recording method comprising: an ink applying step; a drying step; and a fixing step, where an aqueous ink includes resin particles and wax particles, and a glass transition temperature (Tg(°C)) of the resin particles, a melting point (Tm) of the wax particles and a surface temperature (Td(°C)) of the recording medium heated in the drying step, satisfy a relationship of a following formula (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In the inkjet recording method, an image is formed by directly or indirectly applying ink containing a coloring material onto a recording medium such as paper.

[0003] At this time, cockling may occur due to the recording medium absorbing an excessive amount of the liquid components in the ink. Therefore, a method is known in which a drying device is used to dry the recording medium with hot air or infrared rays in order to quickly remove the liquid components in the ink.

[0004] In addition, a method has been proposed in which an ink containing resin particles is applied to a recording medium, and the recording medium is fixed by a fixing device, thereby forming a film of the resin particles contained in the ink on the recording medium to record an image. By using this method, it is possible to improve the robustness of the recorded image by forming the resin particles into a film.

[0005] As an inkjet recording method in which a drying device and a fixing device are combined as described above, Patent Document 1 has been proposed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-188624 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the inkjet recording method described in Patent Document 1, which combines a drying device and a fixing device, if the resin particles are heated to a temperature above their glass transition temperature during heat drying, the resin particles turn into a film. As a result, it was found that there is a problem in that water and solvents in the ink remain in the ink that constitutes the image, reducing the robustness of the image.

[0008] In addition, when the ink is heated above the melting point of the wax particles during fixing by contact heating, the wax particles melt and become more mobile, which reduces the number of wax particles present on the surface of the image formed by the ink, resulting in a decrease in the robustness of the image.

[0009] It is therefore an object of the present invention to provide an inkjet recording method capable of recording images having excellent fastness while suppressing cockling of an ink-absorbent recording medium, and an inkjet recording apparatus and a water-based ink for use in the inkjet recording method. [Means for solving the problem]

[0010] That is, according to the present invention, there is provided an inkjet recording method including an ink application step of ejecting an aqueous ink from a recording head of an inkjet recording system and applying the ink to a recording medium having ink absorbency, a drying step of heating the recording medium to which the aqueous ink has been applied in a non-contact manner to dry the aqueous ink, and a fixing step of heating the recording medium after the drying step with a fixing member to fix the aqueous ink to the recording medium, the aqueous ink comprising resin particles and wax particles, and a glass transition temperature (T g (° C.), the melting point of the wax particles (T m ), and the surface temperature of the recording medium heated in the drying process (T d (° C.) satisfies the relationship of the following formula (1):

[0011]

number

[0012] (In formula (1), λ CH is the thermal conductivity of the fixing material (W / m K), C CH is the heat capacity of the fixing material (J / m 3 ·K), T CH is the surface temperature of the fixing member just before it comes into contact with the recording medium (°C), and λ paper is the thermal conductivity of the recording medium (W / m K), C paper is the heat capacity of the recording medium (J / m 3 ·K), T paper is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.) Effect of the Invention

[0013] According to the present invention, it is possible to provide an inkjet recording method capable of recording an image having excellent fastness while suppressing cockling of an ink-absorbent recording medium.

[0014] Furthermore, according to the present invention, it is possible to provide an inkjet recording apparatus and a water-based ink for use in the inkjet recording method. [Brief description of the drawings]

[0015] [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

[0016] 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.

[0017] The present inventors have investigated a method for recording an image having excellent fastness while suppressing cockling of an ink-absorbent recording medium. As a result, they have inferred that it is important to reduce the amount of liquid components in the ink in the drying process and to make it difficult for wax particles to melt in the fixing process after the drying process. And, to achieve this, the present inventors have found that it is effective to satisfy the requirement of the following formula (1).

[0018]

number

[0019] The surface temperature T of the recording medium heated during the drying process d is the glass transition temperature T g By lowering the viscosity of the ink, it is possible to promote evaporation of liquid components such as water in the ink and their penetration into the recording medium. As a result, the amount of liquid components in an image formed by the ink is reduced, and the robustness of the image can be improved.

[0020] In the fixing process after the drying process, the recording medium is brought into contact with a fixing member, whereby the water-based ink is heated and fixed to the recording medium. At this time, the fixing member and recording medium used satisfy the above formula (1). The temperature of the water-based ink heated by the fixing process becomes approximately the same as the contact surface temperature between the fixing member and the recording medium. The contact surface temperature between the fixing member and the recording medium can be calculated from the surface temperature, thermal conductivity, and heat capacity just before the two objects come into contact, as described in Reference 1 (Japan Society of Mechanical Engineers. Heat Transfer Engineering. Maruzen Co., Ltd., 2005, page 43). Specifically, the contact surface temperature can be calculated by the following formula (1-1).

[0021]

number

[0022] (In formula (1-1), λ CH is the thermal conductivity of the fixing material (W / m K), C CH is the heat capacity of the fixing material (J / m 3 ·K), T CH is the surface temperature of the fixing member just before it comes into contact with the recording medium (°C), and λ paper is the thermal conductivity of the recording medium (W / m K), C paper is the heat capacity of the recording medium (J / m 3 ·K), T paper is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.) Therefore, by using a fixing member and a recording medium that satisfy formula (1), the water-based ink can be fixed at a temperature higher than the glass transition temperature T g The toner is heated and fixed to a temperature equal to or higher than this temperature. This causes the resin particles to melt and form a film, improving the fastness of the image.

[0023] In addition, in the fixing process, the water-based ink is heated and fixed at a temperature lower than the melting point of the wax particles. This allows the wax particles to be exposed to the surface of the image without melting. This reduces the surface energy of the image and the friction coefficient of the image surface, thereby improving the fastness of the image.

[0024] <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 an inkjet recording method having an ink application step, a drying step, and a fixing step. The ink application step is a step of ejecting water-based ink from a recording head of an inkjet recording system and applying the ink to a recording medium having ink absorbency. The drying step is a step of heating the recording medium to which the water-based ink has been applied in a non-contact manner to dry the water-based ink. The fixing step is a step of heating and fixing the water-based ink to the recording medium by contacting the recording medium after the drying step with a fixing member. The water-based ink contains resin particles and wax particles. The glass transition temperature (T g (℃), melting point of wax particles (T m ), and the surface temperature of the recording medium heated in the drying process (T d (°C)) satisfies the relationship of the following formula (1).

[0025]

number

[0026] (In formula (1), λ CH is the thermal conductivity of the fixing material (W / m K), C CH is the heat capacity of the fixing material (J / m 3 ·K), T CH is the surface temperature of the fixing member just before it comes into contact with the recording medium (°C), and λ paper is the thermal conductivity of the recording medium (W / m K), C paper is the heat capacity of the recording medium (J / m 3 ·K), T paper is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.) The inkjet recording apparatus (hereinafter also simply referred to as "recording apparatus") of the present invention is an inkjet recording apparatus used in an inkjet recording method having an ink application step, a drying step, and a fixing step. The ink application step is a step of ejecting water-based ink from a recording head of the inkjet recording method and applying the ink to a recording medium having ink absorbency. The drying step is a step of heating the recording medium to which the water-based ink has been applied in a non-contact manner to dry the water-based ink.

[0027] The fixing step is a step in which the recording medium after the drying step is brought into contact with a fixing member, whereby the water-based ink is heated and fixed to the recording medium. The water-based ink contains resin particles and wax particles. The glass transition temperature (T g (℃), melting point of wax particles (T m ), and the surface temperature of the recording medium heated in the drying process (T d (°C)) satisfies the relationship of the following formula (1).

[0028]

number

[0029] (In formula (1), λ CH is the thermal conductivity of the fixing material (W / m K), C CH is the heat capacity of the fixing material (J / m 3 ·K), T CH is the surface temperature of the fixing member just before it comes into contact with the recording medium (°C), and λ paper is the thermal conductivity of the recording medium (W / m K), C paper is the heat capacity of the recording medium (J / m 3 ·K), T paper is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.) The aqueous ink of the present invention (hereinafter, simply referred to as "ink") is an aqueous ink used in an inkjet recording method having an ink application step, a drying step, and a fixing step. The ink application step is a step of ejecting the aqueous ink from a recording head of an inkjet recording method and applying it to a recording medium having ink absorbency. The drying step is a step of heating the recording medium to which the aqueous ink has been applied in a non-contact manner to dry the aqueous ink. The fixing step is a step of heating and fixing the aqueous ink to the recording medium by contacting the recording medium after the drying step with a fixing member. The aqueous ink contains resin particles and wax particles. The glass transition temperature (T g (℃), melting point of wax particles (T m ), and the surface temperature of the recording medium heated in the drying process (T d (°C)) satisfies the relationship of the following formula (1).

[0030]

number

[0031] (In formula (1), λ CH is the thermal conductivity of the fixing material (W / m K), C CH is the heat capacity of the fixing material (J / m 3 ·K), T CH is the surface temperature of the fixing member just before it comes into contact with the recording medium (°C), and λ paper is the thermal conductivity of the recording medium (W / m K), C paper is the heat capacity of the recording medium (J / m 3 ·K), T paper is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.) (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.

[0032] The inkjet recording apparatus 100 of the embodiment shown in FIG. 1 is configured to include a recording unit 1000, a heating unit 2000, a fixing unit 3000, a cooling unit 4000, an inverting unit 5000, and a paper discharge unit 6000. In the recording unit 1000, various liquids are applied by a liquid application unit 1200 to a recording medium 1100 conveyed from a paper feeder 1400 by a conveying member 1300. In the heating unit 2000, the liquid applied to the recording medium 1100 is heated by a heating unit 2100, and volatile components such as water in the liquid are evaporated and dried. In the fixing unit 3000, a fixing member 3100 is brought into contact with the area of ​​the recording medium 1100 to which the liquid has been applied, and heated to promote fixing of the image to the recording medium 1100. The recording medium 1100 is then cooled by a cooling member 4100 of the cooling unit 4000. When an image is to be recorded on the back side following the front side (recording surface), the recording medium 1100 is first inverted by an inversion device 5100 of an inversion section 5000. Next, an image is recorded on the back side in the same manner as the front side, and then the recording medium is transported by a transport member 6100 of a paper discharge section 6000 and stacked and stored in a recording medium storage section 6200.

[0033] In the recording method and recording apparatus of the present invention, an ink-absorbent recording medium is used. The ink-absorbent recording medium is a recording medium that is absorbent for 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 5mL / m 2In the present invention, a recording medium that satisfies the above water absorption condition is defined as an "ink-absorbent recording medium." Recording media made of resins such as polyethylene terephthalate (PET) and polyvinyl chloride usually have a water absorption rate of 5 mL / m 2 Therefore, the recording medium does not absorb ink or has low ink absorption.

[0034] As for the recording medium 1100, 30 msec from the start of contact 1 / 2 Water absorption up to 5mL / m 2 A recording medium having the above ink absorbency (permeability) is used. 1 / 2 Water absorption up to 10mL / m 2 It is preferable that the surface roughness of the recording medium 1100 is greater than 100 nm. Examples of recording media that can be suitably used as recording media having ink absorbency (permeability) include recording media without a coating layer, such as plain paper, uncoated paper, and synthetic paper, and recording media with a coating layer (coated paper), such as printing paper, glossy paper, and art paper. As long as the coating layer has ink absorbency (permeability), the substrate of the recording medium may be a film or sheet made of resin, or paper provided with a resin layer (so-called resin-coated paper). The basis weight (g / m2) of the recording medium 1100 may be 100 nm. 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:

[0035] [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.

[0036] 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.

[0037] 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".

[0038] The thickness of the ink applied to the recording medium is preferably 10 μm or less.

[0039] 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.

[0040] 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.

[0041] [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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] [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.

[0046] [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. Between the ink application step and the fixing step, there is further a drying 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.

[0047] 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.

[0048] 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.

[0049] The surface temperature T of the recording medium heated during the drying process d is the surface temperature of the recording medium immediately after passing through the heating device. The surface temperature of the recording medium can be determined using a radiation thermometer.

[0050] A specific example of the radiation thermometer is the product name "Radiation Thermometer IT-545S" (manufactured by Horiba, Ltd.). The surface temperature T d is the glass transition temperature T of the resin particles. g lower than (i.e., T g >T d This makes it possible to improve the robustness of the image. It is preferable to set the heating temperature so that the liquid component is quickly evaporated and the recording medium 1100 is not overdried in order to prevent deformation of the recording medium 1100. Specifically, the surface temperature T dThe 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, 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 hot air can be measured using a K-type thermocouple thermometer. A specific example of a measuring device is the product name "AD-5605H" (manufactured by A&D). In particular, the surface temperature T of the heated recording medium in the drying process is preferably 1 m / s or higher and 100 m / s or lower. d is lower than the melting point of the wax particles, which can improve the robustness of the image.

[0051] Furthermore, the removal rate of the liquid components of the reaction liquid and ink in the drying step is preferably 70% by mass or more based on the total mass of the reaction liquid and ink, which can suppress deformation of the recording medium.

[0052] The removal rate of the liquid components of the reaction liquid and the ink can be determined as follows.

[0053] First, the amount of moisture in the reaction liquid and ink before and after drying by heating was measured using an infrared moisture content meter, and the moisture removal rate was calculated from each measured value. The amount of organic solvent in the reaction liquid and ink before and after drying was also measured by measuring the content of each organic solvent in the reaction liquid and ink collected from the recording medium 1100 by liquid chromatography, and the total organic solvent removal rate was calculated from each measured value. The moisture removal rate and the organic solvent removal rate were added together to obtain the liquid component removal rate.

[0054] However, when a non-volatile organic solvent with a boiling point much higher than that of water, such as glycerin, is contained, it will not evaporate when heated and dried at 60°C to 120°C, so the moisture removal rate measured by the infrared moisture meter was used as the liquid component removal rate.

[0055] 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.

[0056] 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).

[0057] 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.

[0058] 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.

[0059] [Fixing section] As shown in FIG. 1, the fixing unit 3000 is a contact-type heating and pressurizing mechanism having a fixing member 3100 as a fixing belt such as an endless belt and a conveying member 3200. In the fixing unit 3000, the recording medium 1100 is conveyed by the conveying member 3200, and the fixing member 3100 is brought into contact with the recording medium 1100 under pressure, and the liquid such as the reaction liquid or ink applied to the recording medium 1100 is heated. In this way, an image can be fixed on the recording medium 1100. From the recording medium 1100 on which an image has been recorded, the liquid components of the reaction liquid or ink permeate the recording medium 1100 or evaporate by passing through the heating unit 2000, and then the image is fixed in the fixing unit 3000, completing the image. By heating and pressurizing the recording medium 1100 sandwiched between the fixing member 3100 and the conveying member 3200, the image of the recording medium 1100 and the fixing member 3100 come into close contact with each other, and the image is fixed on the recording medium 1100. When a liquid such as ink containing resin particles and coloring material is used, the resin particles are softened and form a film mainly by heating in the fixing unit 3000 , and the coloring material can be bound onto the recording medium 1100 .

[0060] The fixing member 3100 can 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 can be provided at a location separate from the fixing member 3100. These methods may also be combined. If necessary, the conveying member 3200 may be heated. Alternatively, a fixing roller or the like may be used as the fixing member 3100.

[0061] 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 a radiation thermometer is a product called "Radiation Thermometer IT-545S" (manufactured by Horiba, Ltd.).

[0062] The ink contains resin particles and wax particles. In the fixing step, a fixing member and a recording medium that satisfy the relationship of the following formula (1) are used.

[0063]

number

[0064] In addition, the λ CH , said C CH , said λ paper , and the C paper It is preferable that the relationship of the following formula (2) is satisfied, whereby the robustness of the image can be further improved.

[0065]

number

[0066] Thermal conductivity λ of fixing material CH is preferably 0.10 W / m K or more and 20.00 W / m K or less, and more preferably 0.26 W / m K or more and 15.10 W / m K or less. CH is 1.00 x 10 6 J / m 3 ·K or more 5.00×10 6 J / m 3 ·K or less is preferable, and 1.55×10 6 J / m 3 ·K or more 3.86×10 6 J / m 3 It is more preferable that the surface temperature T of the fixing member immediately before contacting the recording medium is equal to or lower than 1 K. CHThe thermal conductivity λ of the recording medium is preferably 70° C. or more and 120° C. or less. paper is preferably 0.05 W / m K or more and 0.10 W / m K or less, and more preferably 0.06 W / m K or more and 0.08 W / m K or less. paper is 1.00 x 10 6 J / m 3 ·K or more 3.00×10 6 J / m 3 ·K or less is preferable, and 1.17×10 6 J / m 3 ·K or more 2.24×10 6 J / m 3 It is more preferable that the surface temperature T of the recording medium immediately before contacting the fixing member is equal to or lower than 1 K. paper It is preferable that the temperature is 40°C or higher and 80°C or lower.

[0067] The nip pressure of the fixing member 3100 and the conveying member 3200, i.e., the pressure applied to the recording medium when passing through the contact-type heating and pressing mechanism, is preferably 10 Pa or more and 1000 Pa or less. Furthermore, the nip pressure of the fixing member 3100 and the conveying member 3200 is more preferably 10 Pa or more and 500 Pa or less, and even more preferably 10 Pa or more and 400 Pa or less. By setting the nip pressure within the above range, the wax particles are prevented from being excessively pressed into the image, and the robustness of the image can be improved. The pressure applied to the recording medium when passing through the contact-type heating and pressing mechanism (the nip pressure of the fixing member 3100 and the conveying member 3200) can be measured using, for example, a surface pressure measurement film. A specific example of the surface pressure measurement film is the product name "Prescale" (manufactured by Fujifilm), and an appropriate model number can be selected according to the pressure range.

[0068] 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.

[0069] The fixing member 3100 constituting the contact-type heating and pressing mechanism is preferably a fixing belt such as an endless belt. When a fixing belt is used as the fixing member 3100, the contact time between the fixing member 3100 and the recording medium 1100 can be set longer. This makes it possible to more fully melt and fix the resin particles in the ink, further improving the robustness of the image.

[0070] 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.

[0071] [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).

[0072] [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)).

[0073] [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.

[0074] <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.

[0075] [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 can destabilize 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 promote the aggregation of the ink. Examples of the reactant include cationic components such as polyvalent metal ions and cationic resins, and organic acids. The reactant may be used alone or in combination of two or more.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] [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.

[0080] [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.

[0081] [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.

[0082] <Ink> The ink used in the recording method of the present invention is a water-based ink for ink-jet recording, which contains resin particles and wax particles. Each component of the ink will be described in detail below.

[0083] [Colorant] The ink preferably contains a coloring material. Pigments or dyes can be used as the coloring material. The content (mass %) of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] The dye preferably has an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes. The dye may be used alone or in combination of two or more. The coloring material is preferably a pigment, and more preferably a resin-dispersed pigment or a self-dispersed pigment.

[0089] [resin] The ink contains resin particles. By using an ink containing resin particles, an image having excellent fastness can be recorded. The ink may further contain a water-soluble resin that can be dissolved in an aqueous medium. The water-soluble 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 can also be added to the ink (ii) to improve various properties of the recorded image.

[0090] 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.

[0091] [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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] [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.

[0096] 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.

[0097] Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0098] 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.

[0099] 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 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 resin particles can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above.

[0100] Glass transition temperature T of resin particles g (℃) is the surface temperature T of the recording medium heated in the drying process. d (℃) is lower than the glass transition temperature T g The glass transition temperature (°C) is preferably 40°C or higher and 120°C or lower, more preferably 50°C or higher and 110°C or lower, and even more preferably 50°C or higher and 100°C or lower. The glass transition temperature (°C) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not need to contain a colorant.

[0101] The glass transition temperature of the resin particles in the ink can be measured, for example, by ultracentrifuging the ink, washing and drying the separated resin particles, and then using a differential scanning calorimeter. 50 ) can be measured, for example, by ultracentrifuging the ink, washing and drying the separated resin particles, and then using a particle size distribution measuring device. It can also be measured in the same manner using the aqueous dispersion of resin particles used to prepare the ink.

[0102] [Wax particles] The ink may contain particles formed from wax (wax particles).

[0103] By using an ink containing wax particles, an image with improved abrasion resistance can be recorded. In this specification, the wax may be a composition containing components other than wax, or the wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or a resin. The wax may be used alone or in combination of two or more kinds. The content (mass %) of the wax particles in the ink is preferably 0.1 mass % or more and 10.0 mass % or less, and more preferably 1.0 mass % or more and 5.0 mass % or less, based on the total mass of the ink.

[0104] 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).

[0105] 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.

[0106] The wax is preferably solid at room temperature (25° C.). The melting point T m (°C) is preferably 40°C or more and 120°C or less, more preferably 50°C or more and 120°C or less, and even more preferably 60°C or more and 120°C or less. 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 it is linear, and the lower the melting point if it is branched), crystallinity (the higher the crystallinity, the higher the melting point), and density (the higher the crystallinity, the higher the melting point).

[0107] Therefore, by controlling these properties, it is possible to obtain a wax having a desired melting point. The melting point of the wax in the ink can be measured, for example, by ultracentrifuging the ink, separating the wax, washing and drying it, and then measuring the melting point in accordance with the above-mentioned test method.

[0108] [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.

[0109] [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.

[0110] 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.

[0111] 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.

[0112] [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.

[0113] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less. EXAMPLES

[0114] 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.

[0115] <Preparation of reaction solution> The components shown below were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec Toyo) with a pore size of 3.0 μm to prepare each reaction liquid. Glutaric acid: 21.0% Potassium hydroxide: 2.0% Glycerin: 5.0% Megafac F444 (DIC): 5.0% Ion-exchanged water: 67.0%

[0116] <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 carbon black (product name "Monac 1100", manufactured by Cabot), 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. After centrifugal separation to remove coarse particles, the mixture was filtered under pressure using a cellulose acetate filter (Advantec Toyo) 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%.

[0117] <Preparation of resin particles> 20 parts of ethyl methacrylate, 3 parts of 2,2'-azobis(2-methylbutyronitrile), and 2 parts of n-hexadecane were mixed and stirred for 0.5 hours. This mixture was added dropwise to 75 parts of an 8% aqueous solution of styrene-butyl acrylate-acrylic acid copolymer (acid value: 130 mgKOH / g, weight average molecular weight (Mw): 7,000) and stirred for 0.5 hours. Next, ultrasonic waves were irradiated for 3 hours using an ultrasonic irradiation device. Subsequently, a polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere, and after cooling to room temperature, filtration was carried out to prepare a resin particle dispersion with a resin particle content of 25.0% by mass. The glass transition temperature T g is 85°C.

[0118] [Glass transition temperature of resin particles] The resin sample was prepared by drying the aqueous dispersion of resin particles. A differential scanning calorimeter (product name "Q200", manufactured by TA Instruments) was used to measure the glass transition temperature (T g (°C) was measured.

[0119] <Ink Preparation> The following components (unit: %) were mixed and thoroughly stirred, then pressure filtered through a cellulose acetate filter (Advantec Toyo) with a pore size of 3.0 μm to prepare black ink. "Acetylenol E100" is the product name of a surfactant manufactured by Kawaken Fine Chemicals. "Hi-Mic-2095" is the product name of a microcrystalline wax manufactured by Nippon Seiro. Pigment: 4.0% Resin particles: 6.0% Glycerin: 7.0% Polyethylene glycol (number average molecular weight (Mn): 1,000): 1.0% Surfactant (Acetylenol E100): 0.5% Wax (Hi-Mic-2095, melting point T m : 103℃): 1.0% Ion-exchanged water: 80.5%

[0120] <Evaluation> Using the inkjet recording apparatus 100 having the configuration shown in FIG. 1, an image was recorded on a recording medium under the recording conditions shown in Table 3. A hot air dryer was used as the heating device 2100 of the heating section 2000, and the surface temperature T d is the surface temperature T of the recording medium immediately before it comes into contact with the fixing member shown in Table 3. paper The surface temperature of the recording medium heated in this drying process was set to be the same as that of the recording medium heated in this drying process. d was measured using a radiation thermometer IT-545S (manufactured by Horiba, Ltd.). A fixing roller having a halogen heater as a heat source inside the roller was used as the fixing member 3100 of the fixing unit 3000. The type of material of the surface of the fixing member 3100, its thermal properties (thermal conductivity and heat capacity), and nip pressure are shown in Table 1.

[0121] [Table 1]

[0122] Before applying the ink, the reaction liquid was applied to the recording medium by the inkjet method. The amount of the reaction liquid applied was 2 g / m 2 The amount of ink applied was 32 g / m2 A solid image was recorded on the entire surface of the A4 size recording medium. The type of recording medium 1100 used, the presence or absence of a coating layer, and the thermal properties (thermal conductivity and heat capacity) are shown in Table 2. Recording media 1 and 3 were both recorded for 30 msec from the start of contact. 1 / 2 Water absorption up to 10mL / m 2 The recording medium 2 is in contact with the recording medium 2 for 30 msec. 1 / 2 Water absorption up to 5mL / m 2 More than 10mL / m 2 The following is the result.

[0123] [Table 2]

[0124] The recorded images were evaluated as follows. In the present invention, in the evaluation criteria for each item below, "AA", "A" and "B" were regarded as acceptable levels, and "C" was regarded as unacceptable. The evaluation results are shown in Table 4.

[0125] (Evaluation of robustness) A fastness test cloth (JIS L 0803 white cotton cloth for dye fastness test, model number 670101) with 50μL of artificial sweat (JIS L 0804 alkaline pH8.0) was wrapped around a 120g friction element of a Gakushin type friction fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.) and the image area was rubbed back and forth 1 to 10 times. The non-image area and the test cloth after the rub test were observed.

[0126] A: In a single double rub test, no ink was found on the test cloth.

[0127] B: A small amount of ink was adhered to the test cloth, and a small amount of ink was adhered to non-image areas due to rubbing, but it was not noticeable.

[0128] C: Ink was attached to the test cloth, and ink was significantly attached to non-image areas due to rubbing.

[0129] (Cock ring evaluation) The printed portions of the samples for evaluating cockling (A4 size full-page solid image) prepared in the examples and comparative examples were visually observed. The evaluation criteria were as follows:

[0130] A: No waviness was observed in the printed area.

[0131] B: Waviness was observed in the printed area, but was at a level that did not cause any problems in practical use.

[0132] C: The wavyness in the printed portion was noticeable, to a level that was problematic in practical use.

[0133] [Table 3]

[0134] [Table 4]

Claims

1. an ink application step of ejecting a water-based ink from a recording head of an ink-jet recording method onto a recording medium having ink absorbency; a drying step of heating the recording medium to which the water-based ink has been applied in a non-contact manner to dry the water-based ink; a fixing step of heating the water-based ink by contacting the recording medium after the drying step with a fixing member, thereby fixing the water-based ink on the recording medium, the water-based ink contains resin particles and wax particles, The glass transition temperature (T ｇ (° C.), the melting point of the wax particles (T ｍ ), and the surface temperature (T ｄ (° C.) satisfies the relationship of the following formula (1): [0010] (In formula (1), λ ＣＨ is the thermal conductivity of the fixing material (W / m K), C ＣＨ is the heat capacity of the fixing member (J / m ３ K), T ＣＨ is the surface temperature of the fixing member immediately before it comes into contact with the recording medium (°C), and λ ｐａｐｅｒ is the thermal conductivity of the recording medium (W / m K), C ｐａｐｅｒ is the heat capacity of the recording medium (J / m ３ K), T ｐａｐｅｒ is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.

2. Said λ ＣＨ , the above C ＣＨ , said λ ｐａｐｅｒ , and the C ｐａｐｅｒ The ink jet recording method according to claim 1 , wherein the relationship represented by the following formula (2) is satisfied: [0025]

3. Said T ｄ The ink-jet recording method according to claim 1, wherein the temperature is 40° C. or higher and 100° C. or lower.

4. The ink-jet recording method according to claim 1, further comprising a reaction liquid applying step of applying an aqueous reaction liquid containing a reactant that reacts with the aqueous ink onto a recording medium.

5. an ink application step of ejecting a water-based ink from a recording head of an ink-jet recording method onto a recording medium having ink absorbency; a drying step of heating the recording medium to which the water-based ink has been applied in a non-contact manner to dry the water-based ink; a fixing step of heating the water-based ink and fixing it on the recording medium by contacting the recording medium after the drying step with a fixing member, the water-based ink contains resin particles and wax particles, The glass transition temperature (T ｇ (° C.), the melting point of the wax particles (T ｍ ), and the surface temperature (T ｄ (° C.) satisfies the relationship of the following formula (1): [0030] (In formula (1), λ ＣＨ is the thermal conductivity of the fixing material (W / m K), C ＣＨ is the heat capacity of the fixing member (J / m ３ K), T ＣＨ is the surface temperature of the fixing member immediately before it comes into contact with the recording medium (°C), and λ ｐａｐｅｒ is the thermal conductivity of the recording medium (W / m K), C ｐａｐｅｒ is the heat capacity of the recording medium (J / m ３ K), T ｐａｐｅｒ is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.

6. an ink application step of ejecting a water-based ink from a recording head of an ink-jet recording method onto a recording medium having ink absorbency; a drying step of heating the recording medium to which the water-based ink has been applied in a non-contact manner to dry the water-based ink; a fixing step of heating the water-based ink to fix it on the recording medium by contacting the recording medium after the drying step with a fixing member, Contains resin particles and wax particles, The glass transition temperature (T ｇ (° C.), the melting point of the wax particles (T ｍ ), and the surface temperature (T ｄ (° C.) satisfies the relationship of the following formula (1): [0045] (In formula (1), λ ＣＨ is the thermal conductivity of the fixing material (W / m K), C ＣＨ is the heat capacity of the fixing member (J / m ３ K), T ＣＨ is the surface temperature of the fixing member immediately before it comes into contact with the recording medium (°C), and λ ｐａｐｅｒ is the thermal conductivity of the recording medium (W / m K), C ｐａｐｅｒ is the heat capacity of the recording medium (J / m ３ K), T ｐａｐｅｒ is the surface temperature (°C) of the recording medium just before it comes into contact with the fixing member.

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