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

Abstract

To provide an inkjet recording method capable of recording an image excellent in sharpness, even when a plurality of ink is imparted to a hardly absorbable to non-absorbable recording medium in a superposed manner.SOLUTION: An inkjet recording method discharges first ink, second ink, a first reaction liquid and a second reaction liquid from a recording head, applies them to a recording medium in a superposed manner in at least a partial region of the recording medium, and records an image. The inkjet recording method includes: a first reaction liquid application step of applying the first reaction liquid to the recording medium; a first ink application step of applying the first ink to the recording medium after the first reaction liquid application step; a second ink application step of applying the second ink to the recording medium after the first ink application step; and a second reaction liquid application step of applying the second reaction liquid to the recording medium after the first ink application step. Surface tension of the second reaction liquid is higher than surface tension of the first reaction liquid.SELECTED DRAWING: None

Description

[Technical field]

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

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

[0003] In the sign and display field, poorly absorbing recording media that do not absorb ink and non-absorbing recording media that do not absorb ink are often used, the surfaces of which are formed of vinyl chloride, polyethylene terephthalate, etc., and have almost no ink absorption. Hereinafter, these recording media may be collectively referred to as "poorly to non-absorbing recording media". When recording an image on a poorly to non-absorbing recording medium, since the recording medium does not absorb ink easily or does not absorb ink, it is required to reduce ink bleeding and improve the sharpness of the image. In other words, in the inkjet recording method for recording on a poorly to non-absorbing recording medium, it is important to suppress bleeding and improve the sharpness of the image by preventing ink dots from being repelled by the recording medium. For this purpose, it is necessary to rapidly thicken and fix the ink after it is applied to the recording medium.

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

[0005] Methods for recording on poorly to non-absorbent recording media using aqueous ink include a method of evaporating liquid components of the ink, such as water, on the surface of the poorly to non-absorbent recording media, and a method of using a reaction liquid that aggregates the ink components. The former is advantageous in terms of running costs because there is no need to provide a means for applying the reaction liquid, but the recording speed cannot be increased, resulting in poor productivity. For this reason, methods that use a reaction liquid have been considered (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-044724 A [Patent Document 2] JP 2015-147405 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present inventors, referring to the description of Patent Document 1, applied the reaction liquid twice when applying the first ink and the second ink to a poorly to non-absorbent recording medium to record an image, and evaluated various characteristics. In addition, the first reaction liquid, the second reaction liquid, the first ink, and the second ink described in Patent Document 2 were used to record on a poorly to non-absorbent recording medium, and various characteristics were evaluated. As a result, in all cases examined, it was found that there was a difference in the appearance of the image of the second ink between an image of the second reaction liquid and the second ink applied over the area where the first reaction liquid and the first ink were applied, and an image where only the second reaction liquid and the second ink were applied. Specifically, it was found that the composition of the reaction liquid was not suitable for each ink, and as a result, when the second reaction liquid and the second ink were applied to the area where the first reaction liquid and the first ink were applied, the second ink was easily bled, and the sharpness of the image was insufficient.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording an image with excellent sharpness even when a plurality of inks are applied in layers to a poorly to non-absorbent recording medium. Another object of the present invention is to provide an inkjet recording device used in the inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method for recording an image by ejecting from a recording head a first ink which is an aqueous ink containing at least one particulate substance selected from the group consisting of a pigment and resin particles, a second ink which is an aqueous ink containing a pigment, a first reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink, and a second reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink, and applying the first reaction liquid to a recording medium so as to overlap each other in at least a partial region of the recording medium, the inkjet recording method comprising: a first reaction liquid applying step of applying the first reaction liquid to the recording medium, a first ink applying step of applying the first ink to the recording medium after the first reaction liquid applying step, a second ink applying step of applying the second ink to the recording medium after the first ink applying step, and a second reaction liquid applying step of applying the second reaction liquid to the recording medium after the first ink applying step, 1 / 2 Water absorption up to 10mL / m 2 The inkjet recording method is characterized in that the second reaction liquid has a higher surface tension than the first reaction liquid. Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method capable of recording an image with excellent sharpness even when a plurality of inks are applied in layers to a poorly to non-absorbent recording medium. Also, according to the present invention, it is possible to provide an inkjet recording device used in the inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 2] 1 is a side view diagrammatically illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 3] FIG. 1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus of the present invention. [Figure 4] FIG. 2 is a perspective view showing an example of a liquid application device. [Diagram 5] FIG. 2 is a cross-sectional perspective view showing an example of a discharge element substrate. [Figure 6] FIG. 2 is a schematic diagram showing an example of a liquid supply system. [Figure 7] FIG. 13 is a schematic diagram showing another example of the heating unit. [Figure 8] FIG. 11 is a schematic diagram showing another example of the fixing unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0013] The present inventors have investigated the reason why image sharpness cannot be obtained when an image is recorded using a reaction liquid and two kinds of inks as described in Patent Document 1, or when an image is recorded using two kinds of reaction liquids and two kinds of inks as described in Patent Document 2. When an image is recorded using a plurality of inks on a poorly to non-absorbent recording medium, there are two cases: a case where another ink is applied over an area where ink has already been applied, and a case where ink is applied to an area where ink has not yet been applied. In this case, when another ink is applied to an area where ink has already been applied, unlike a case where ink is applied to an area where ink has not yet been applied, even if the same amount of ink is applied, the ink is likely to bleed and the line width is likely to become thick. As a result, image sharpness cannot be obtained. When the present inventors investigated the reason why ink is likely to bleed, it was found that the newly applied ink not only sinks into the already formed ink layer, but also diffuses to the surface of the ink layer, that is, bleeds. It was also found that this phenomenon cannot be sufficiently suppressed even by using a reaction liquid.

[0014] Therefore, the inventors further investigated the composition and characteristics of the pigment and reaction liquid, and the conditions for applying them, and found that the sharpness of an image can be improved by using a specific first ink, a specific second ink, a first reaction liquid, and a second reaction liquid, applying them to a recording medium in a specific order, and adjusting the magnitude relationship of the surface tension between the first reaction liquid and the second reaction liquid.

[0015] That is, the inkjet recording method of the present invention has the following features. First, the first ink is an aqueous ink containing at least one particulate material selected from the group consisting of pigments and resin particles. The second ink is an aqueous ink containing a pigment. The first reaction liquid is an aqueous reaction liquid containing a reactant that reacts with at least one ink selected from the group consisting of the first ink and the second ink. The second reaction liquid is an aqueous reaction liquid containing a reactant that reacts with at least one ink selected from the group consisting of the first ink and the second ink. These first ink, second ink, first reaction liquid, and second reaction liquid are each ejected from a recording head and applied to a recording medium so as to overlap each other in at least a part of the recording medium to record an image. The method includes a first reaction liquid application step of applying the first reaction liquid to the recording medium, and a first ink application step of applying the first ink to the recording medium after the first reaction liquid application step. Furthermore, the method includes a second ink application step of applying the second ink to the recording medium after the first ink application step, and a second reaction liquid application step of applying the second reaction liquid to the recording medium after the first ink application step. The recording medium used in this case is a recording medium that is 1 / 2 Water absorption up to 10mL / m 2 The surface tension of the second reaction liquid is higher than the surface tension of the first reaction liquid. The present inventors speculate that the mechanism by which the above-mentioned configuration can improve the sharpness of an image is as follows.

[0016] In the present invention, an image is recorded using the first ink, the second ink, the first reaction liquid, and the second reaction liquid. There are two possible orders for applying each liquid. That is, (i) the first reaction liquid applying step, the first ink applying step, the second ink applying step, and the second reaction liquid applying step are performed in this order, or (ii) the first reaction liquid applying step, the first ink applying step, the second reaction liquid applying step, and the second ink applying step are performed in this order. By recording an image in this order, the first ink is aggregated by the first reaction liquid, and an overlapping image can be recorded by the second ink and the second reaction liquid, improving the sharpness of the image. The reason why such an effect is obtained will be explained.

[0017] The first ink applied after the first reaction liquid is an aqueous ink containing at least one particulate material selected from the group consisting of pigments and resin particles. When an image is recorded using such an ink, it is considered that a porous layer having many voids between particles is first formed on the recording medium because the particulate material is a component with a particle diameter. Therefore, when the second ink or the second reaction liquid containing a pigment is applied in layers, the liquid components of the second ink or the second reaction liquid are likely to penetrate into the porous layer of the first ink by capillary force. As a result, bleeding of the second ink can be suppressed.

[0018] In addition, the tendency of the second ink to bleed when it is applied over the first ink depends on the relationship between the second ink or the second reaction liquid and the surface tension of the first ink layer. As a result of the study by the present inventors, the first reaction liquid or the second reaction liquid contains a reactant that aggregates at least one ink component selected from the group consisting of the first ink and the second ink. For this reason, it was found that the relationship between the surface tensions of the reaction liquids is dominant in the tendency of the second ink to bleed. By having a higher surface tension of the second reaction liquid than the first reaction liquid, the second reaction liquid is more likely to remain on the layer of the first ink, and the second ink can be efficiently aggregated. As a result, even when the second ink is applied, bleeding is suppressed and the sharpness of the image can be improved. If the surface tension of the first reaction liquid is equal to or lower than the surface tension of the second reaction liquid, the second reaction liquid is less likely to remain on the layer of the first ink, and the aggregation of the second ink does not proceed efficiently. As a result, the second ink bleeds, and the sharpness of the image cannot be improved.

[0019] <Inkjet recording method, inkjet recording apparatus, and set of aqueous ink and aqueous reaction liquid> The inkjet recording method of the present invention (hereinafter, also simply referred to as "recording method") is a method in which an aqueous ink and an aqueous reaction liquid are discharged from an inkjet recording head by the action of thermal energy and applied to a recording medium to record an image. This method includes a first reaction liquid application step of applying a first reaction liquid to a recording medium, and a first ink application step of applying the first ink to the recording medium after the first reaction liquid application step. It also includes a second ink application step of applying a second ink to the recording medium after the first ink application step, and a second reaction liquid application step of applying the second reaction liquid to the recording medium after the first ink application step. The first reaction liquid is an aqueous reaction liquid containing a reactant that reacts with at least one ink selected from the group consisting of the first ink and the second ink. The second reaction liquid is an aqueous reaction liquid containing a reactant that reacts with at least one ink selected from the group consisting of the first ink and the second ink. The first ink, the second ink, the first reaction liquid, and the second reaction liquid are discharged from a recording head and applied to the recording medium so as to overlap each other in at least a partial area of ​​the recording medium to record an image. The recording medium used in this case is a recording medium that is 1 / 2 Water absorption up to 10mL / m 2 and the surface tension of the second reaction liquid is higher than the surface tension of the first reaction liquid.

[0020] The inkjet recording apparatus of the present invention (hereinafter, also simply referred to as "recording apparatus") is an apparatus used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid are ejected from an inkjet recording head by the action of thermal energy and applied to a recording medium to record an image. The recording apparatus of the present invention is an apparatus that is suitably used in the above-mentioned recording method. In the recording method and recording apparatus of the present invention, it is not necessary to cure the image by irradiation with active energy rays or the like.

[0021] The set of aqueous ink and aqueous reaction liquid of the present invention is a set used in an inkjet recording method in which an aqueous ink and an aqueous reaction liquid containing a reactant that reacts with the aqueous ink are ejected from a recording head to record an image on a recording medium. The set is preferably used in the above-mentioned recording method. The form of the set includes a set of multiple ink cartridges each containing multiple inks (reaction liquids) independently, and an ink cartridge formed integrally by combining multiple ink containing parts each containing multiple inks (reaction liquids). The set of the present invention is not limited to the above form and may be in any form as long as it is configured so that the inks and reaction liquids can be used in combination.

[0022] (Inkjet recording device) The inkjet recording apparatus will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the inkjet recording apparatus of the present invention. FIG. 2 is a side view showing an embodiment of the inkjet recording apparatus of the present invention. As shown in FIGS. 1 and 2, the recording apparatus of this embodiment includes an inkjet recording head 22 that ejects ink. The recording head 22 is a recording head that ejects ink by the action of thermal energy. The recording head that ejects ink by the action of thermal energy applies thermal energy to the ink by applying an electric pulse to an electrothermal conversion element, and ejects the ink from the ejection port. Here, a recording head that ejects ink by the action of thermal energy is taken as an example, but a recording head that ejects ink by the action of mechanical energy may also be adopted. The recording head may include a mechanism (temperature control mechanism) that heats the water-based ink ejected from the recording head. When the temperature control mechanism is provided, the heating temperature of the ink ejected from the recording head is preferably 35° C. or higher and 70° C. or lower. It is also preferable that the application of the first ink and the second ink, and the application of the first reaction liquid and the second reaction liquid to a unit area of ​​a recording medium are each performed by a plurality of relative scans of the recording head and the recording medium.

[0023] [Heating process] The recording method of the present invention may include a step of heating (heat treatment) the recording medium to which the ink has been applied. By heating the recording medium to which the ink has been applied, it is possible to promote drying and increase the strength of the image.

[0024] Examples of the means for heating the recording medium include known heating means such as a heater, air blowing means using air blowing such as a dryer, and a combination of these. Examples of the heating means include the above heating means, air blowing means, and a combination of these. Examples of the heat treatment method include a method of applying heat from the opposite side (back side) of the recording surface (ink application surface) of the recording medium using a heater, a method of applying warm or hot air to the recording surface of the recording medium, and a method of heating from the recording surface or back side using an infrared heater. A combination of these methods may also be used.

[0025] In order to enhance the abrasion resistance of the image, the heating temperature of the recording medium to which the ink and reaction liquid have been applied is preferably 50° C. or more and 90° C. or less. The heating temperature of the recording medium to which the ink has been applied may be read by a sensor incorporated in a position corresponding to the heating means of the recording device, or may be determined from the relationship between the amount of heat and the temperature of the recording medium, which is determined according to the type of ink and recording medium.

[0026] In the recording device shown in FIGS. 1 and 2, a heater 25 supported by a frame (not shown) is disposed downstream in the sub-scanning direction A from the position where the recording head 22 reciprocates in the main scanning direction B. The recording medium 1 to which ink has been applied can be heated by the heater 25. Specific examples of the heater 25 include a sheath heater and a halogen heater. The heater 25 is covered by a heater cover 26. The heater cover 26 is a member for efficiently irradiating the heat generated by the heater 25 to the recording medium 1. Furthermore, the heater cover 26 is also a member for protecting the heater 25. The recording medium 1 to which ink has been applied ejected from the recording head 22 is wound by a take-up spool 27 to form a roll-shaped wound medium 24.

[0027] 3 is a schematic diagram showing one embodiment of an 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.

[0028] The inkjet recording apparatus 100 of the embodiment shown in FIG. 3 is configured to include a first recording unit 1000, a heating unit 2000, a fixing unit 3000, a cooling unit 4000, a second recording unit 5000, an inverting unit 6000, and a paper discharge unit 7000. In the first recording unit 1000, various liquids 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. After that, the recording medium 1100 is cooled by a cooling member 4100 of the cooling unit 4000. In the second recording section 5000, various liquids are applied to the recording medium 1100 by a liquid application device 5200. When an image is to be recorded on the back side following the front side (recording surface), the recording medium 1100 is first inverted by an inversion device 6100 of the inversion section 6000. Next, after an image is recorded on the back side in the same manner as for the front side, the recording medium is transported by a transport member 7100 of the paper discharge section 7000 and stacked and stored in the recording medium storage section 7200.

[0029] [Recording Section] The first recording unit 1000 includes a liquid applying device 1200. The liquid applying device 1200 includes a reaction liquid applying device 1201 and an ink applying device 1202. The reaction liquid applying device 1201 shown in FIG. 3 is an example of a unit using an inkjet type discharge 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 is applied by the reaction liquid applying device 1201 before the first ink is applied. An inkjet type discharge head (recording head) is used as the ink applying device 1202. The discharge method of the discharge head as the liquid applying device 1200 may include a method of discharging liquid by causing film boiling in the liquid by an electrothermal converter to form bubbles, and a method of discharging liquid by an electromechanical converter. From the viewpoint of image quality, it is preferable that the time until the reaction liquid and the ink come into contact is short. Specifically, it is preferable that the time from the application of the reaction liquid to the application of the ink is 2500 milliseconds or less. Here, the time from when the reaction liquid is applied to when the first ink is applied may be the same as or different from the time from when the reaction liquid is applied to when the second ink is applied. This time can be appropriately changed by adjusting the distance between the means for applying the reaction liquid and the means for applying the ink, or by adjusting the conveying speed of the recording medium. The time from when the reaction liquid is applied to when the ink is applied is preferably 100 milliseconds or more, and more preferably 200 milliseconds or more.

[0030] 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 1206 (FIG. 5) 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.

[0031] 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".

[0032] The second recording section 5000 includes a liquid applying device 5200. The liquid applying device 5200 includes a reaction liquid applying device 5201 and an ink applying device 5202. The second recording section may include the same components as those of the first recording section. The first recording section and the second recording section may not be separated as shown in FIG. 3. For example, the first recording section may include a plurality of reaction liquid applying devices 1201 and ink applying devices 1202, and the recording medium may be returned to the first recording section after the cooling section 4000 using a mechanism for returning the recording medium to the first recording section, and each liquid may be applied. In that case, the reaction liquid applying device 1201 and the ink applying device 1202 used when passing through the first recording section 1000 for the first time may be different from the reaction liquid applying device 1201 and the ink applying device 1202 used when passing through the second time. The reaction liquid applying device 5201 may apply the reaction liquid before or after the application of the second ink. In particular, it is preferable that the reaction liquid is applied by the reaction liquid application device 5201 before the application of the second ink. In other words, it is preferable that the recording method of the present invention performs the first reaction liquid application step, the first ink application step, the second reaction liquid application step, and the second ink application step in this order. This is because, by applying the second reaction liquid before the application of the second ink, the aggregation of the second ink begins early, and bleeding of the image can be further suppressed. As a result, the sharpness of the image can be further improved.

[0033] Fig. 4 is a perspective view showing an example of a liquid application device. The liquid application device 1200 shown in Fig. 4 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.

[0034] FIG. 5 is a cross-sectional perspective view showing an example of a discharge element substrate. The discharge element substrate 1203 shown in FIG. 5 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. 6, liquid chamber 1508). The second flow path 1209 is a region from a portion between the discharge port 1204 and the discharge element (FIG. 6, 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 a high-pressure inlet 1212 and a low-pressure outlet 1213, liquid can flow from the high-pressure side to the low-pressure side (in the direction of the arrow in FIG. 5). 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. 6) flows through the second flow path 1209 and the outlet 1213 to the outlet path 1211.

[0035] [Supply system] FIG. 6 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. 6 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.

[0036] 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.

[0037] 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. 6) is generated in which a 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. 5 indicate the flow of liquid inside the liquid chamber 1508. That is, as shown in Fig. 5, 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.

[0038] 6, 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. 5) communicating with the inflow channel 1210, and an outlet 1213 (FIG. 5) 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.

[0039] [Transport system] As shown in FIG. 3, the first recording unit 1000 is configured to include a liquid applying device 1200 and a conveying member 1300 that conveys the recording medium 1100. The liquid applying device 1200 applies a reaction liquid and ink to a desired position of the recording medium 1100 conveyed by the conveying member 1300. Each liquid applying device receives an image signal of recording data and applies the necessary reaction liquid and ink to each position. FIG. 3 shows the conveying member 1300 in the form of a conveying belt, but a spur, a conveying drum, or the like may be used as long as it has the function of conveying the recording medium 1100. In order to improve the conveying accuracy, a member that can fix the recording medium 1100 can be used as the conveying member 1300. Specifically, a method of providing a hole in the conveying member 1300 and suctioning from the back side to fix the recording medium 1100, a method of forming the conveying member 1300 from an appropriate material and electrostatically adsorbing the recording medium 1100, and the like can be mentioned. The second recording unit 5000 can also be configured in the same manner as the first recording unit 1000.

[0040] [Heating section] As shown in Fig. 3, 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.

[0041] 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.

[0042] 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.

[0043] 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).

[0044] Fig. 7 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. 7 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.

[0045] 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. 3) 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. 3) 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).

[0046] An air knife 2300 is disposed between the transport member 1300 (FIG. 3) 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. 3). 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. 3), and to suppress transport failures.

[0047] 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.

[0048] [Fixing section] As shown in FIG. 3, the fixing unit 3000 is a contact-type heating and pressurizing mechanism having a fixing member 3100 as a fixing belt such as an endless belt and a conveying member 3200. In the fixing unit 3000, the recording medium 1100 is conveyed by the conveying member 3200, and the fixing member 3100 is brought into contact with the recording medium 1100 under pressure, and the liquid such as the reaction liquid or ink applied to the recording medium 1100 is heated. In this way, an image can be fixed on the recording medium 1100. From the recording medium 1100 on which an image has been recorded, the liquid components of the reaction liquid or ink permeate the recording medium 1100 or evaporate by passing through the heating unit 2000, and then the image is fixed in the fixing unit 3000, completing the image. By heating and pressurizing the recording medium 1100 sandwiched between the fixing member 3100 and the conveying member 3200, the image of the recording medium 1100 and the fixing member 3100 come into close contact with each other, and the image is fixed on the recording medium 1100. When a liquid such as ink containing resin particles and coloring material is used, the resin particles are softened and formed into a film mainly by heating in the fixing unit 3000, and the coloring material can be bound onto the recording medium 1100. The recording method and recording apparatus of the present invention do not need to have a fixing unit. In that case, the recording medium may be dried and fixed in the heating unit.

[0049] 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.).

[0050] The first ink described below contains resin particles and particles (wax particles) formed of wax. Therefore, when the temperature of the fixing member 3100 is set to a temperature equal to or higher than the glass transition temperature of the resin particles in the ink, the resin particles soften and are easily formed into a film, and the scratch resistance of the image can be improved. In addition, it is preferable to set the temperature of the fixing member 3100 lower than the melting point of the wax that constitutes the wax particles. This makes it easier for the wax, which is prevented from melting, to remain on the surface of the image, and the scratch resistance of the image can be improved.

[0051] The nip pressure of the fixing member 3100 and the conveying member 3200, i.e., the pressure applied to the recording medium when it passes through the contact-type heating and pressing mechanism, is preferably from 10 Pa to 1,000 Pa, and more preferably from 10 Pa to 500 Pa. Also, it is particularly preferably from 10 Pa to 400 Pa. The time required for the recording medium to pass through the contact-type heating and pressing mechanism (nip time) is preferably from 0.25 seconds to 5.0 seconds, more preferably from 0.5 seconds to 4.0 seconds, and particularly preferably from 1.0 seconds to 3.0 seconds.

[0052] FIG. 8 is a schematic diagram showing another example of the fixing unit. Here, the difference from the fixing unit shown in FIG. 3 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 nip time, temperature, pressure, etc. of the recording medium caused by these.

[0053] [Cooling section] The cooling section 4000 is configured to include a cooling member 4100 and a conveying member 4200 (FIG. 3). The cooling section 4000 cools the recording medium 1100, which has passed through the heating section 2000 and the fixing section 3000 and is heated to a high temperature. 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 increase the 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).

[0054] The above-mentioned heating section, fixing section, and cooling section may be provided after the second recording section 5000. In that case, they may have the same configuration as those described above, or may have different configurations.

[0055] [Inverted part] When performing double-sided recording, the recording medium 1100 is inverted using the inversion unit 6000 (FIG. 3). The recording medium 1100 with an image recorded on its recording surface (front side) passes through the cooling unit 4000, is branched and transported, and is inverted by the inversion device 6100. The inverted recording medium 1100 is transported to the paper feeder 1400 of the recording unit 1000 with liquid applied to its back side (the side opposite to the recording surface (front side)).

[0056] [Paper output section] After the image is recorded, the recording medium 1100 is stored in a paper discharge section 7000 (FIG. 3). 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 7100, and is finally stored in a stacked state in a recording medium storage section 7200. Two or more recording medium storage sections 7200 may be provided to store different recorded materials, etc.

[0057] (Recording medium) In the recording method and recording device of the present invention, a poorly to non-absorbent recording medium is used. A poorly to non-absorbent recording medium is defined as follows. That is, in the Bristow method described in JAPAN TAPPI Paper Pulp Test Method No. 51 "Liquid Absorbency Test Method for Paper and Paperboard", 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2 The following recording media are used. In the present invention, a recording medium that satisfies the above water absorption condition is defined as a "hardly to non-absorbent recording medium." Inkjet recording recording media (glossy paper, matte paper, etc.) having a coating layer (ink receiving layer) formed of inorganic particles, and plain paper having no coating layer are "absorbent recording media" having the above water absorption amount exceeding 10 mL / m2.

[0058] Examples of poorly to non-absorbent recording media include plastic films; recording media in which a plastic film is bonded to the recording surface of a substrate; and recording media in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp. Among these, plastic films are preferred, and recording media in which a resin coating layer is provided on the recording surface of a substrate containing cellulose pulp are also preferred. The basis weight (g / m2) of the recording medium 1100 is preferably 30 g / m2 or more and 500 g / m2 or less, and more preferably 50 g / m2 or more and 450 g / m2 or less.

[0059] When the ink used in the recording method and recording apparatus of the present invention is applied to a poorly to non-absorbent recording medium, the liquid components such as water evaporate and the resin particles are concentrated. This promotes fusion between the concentrated resin particles, improving the strength of the recorded image. In contrast, when the ink is applied to a recording medium with high absorbency of the liquid components, the fusion between the resin particles is not promoted, so the strength of the image does not improve. In this specification, the recording medium does not mean a transfer body, but a recording medium on which an image as a recorded matter is recorded.

[0060] <First reaction solution> The recording method of the present invention includes a first reaction liquid application step of applying a first reaction liquid, which is an aqueous reaction liquid containing a reactant that reacts with at least one aqueous ink selected from the group consisting of a first ink and a second ink, to a recording medium. Each component used in the first reaction liquid will be described in detail below.

[0061] [Reactants] The first reaction liquid contains a reactant, which 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). 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. Among them, it is preferable that the first reaction liquid contains a polyvalent metal salt. The reactant may be used alone or in combination of two or more.

[0062] The content (mass %) of the polyvalent metal salt in the first 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 this specification, when the polyvalent metal salt is a hydrate, the "content (mass %) of the polyvalent metal salt in the reaction liquid means the "content (mass %) of the anhydrous polyvalent metal salt" excluding water as the hydrate.

[0063] 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 - and the like organic anions.

[0064] As the reactant of the first reaction liquid, it is preferable to use magnesium sulfate among polyvalent metal salts. In other words, the polyvalent metal salt in the first reaction liquid is preferably magnesium sulfate. This is because the speed at which solid components of the ink, such as particulate matter, are aggregated can be easily adjusted by the content of the reactant in the reaction liquid and the amount of the reaction liquid applied. When magnesium sulfate is used as the reactant, the content (mass %) of magnesium sulfate in the first reaction liquid is preferably 1.0 mass % or more and 15.0 mass % or less, and more preferably 2.0 mass % or more and 10.0 mass % or less, based on the total mass of the reaction liquid.

[0065] As described above, the reactant may be used alone or in combination of two or more. In particular, from the viewpoint of increasing the cohesive force of the ink, it is preferable that the reactant of the first reaction liquid further contains a cationic resin. The content (mass %) of the cationic resin in the first reaction liquid is preferably 0.1 mass % or more and 10.0 mass % or less, and more preferably 0.2 mass % or more and 5.0 mass % or less, based on the total mass of the reaction liquid. Of these, it is particularly preferable that it is 0.5 mass % or more and 5.0 mass % or less.

[0066] 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 structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. 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.

[0067] 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 first reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0068] [Aqueous medium] The first reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. Examples of the aqueous medium used in the reaction liquid include the same aqueous medium that can be contained in the ink, which will be described later. The content (mass%) of the water-soluble organic solvent in the first 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 first water-soluble organic solvent preferably contains a specific water-soluble hydrocarbon compound, which will be described later. The content (mass%) of the water-soluble hydrocarbon compound in the first 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 first reaction liquid is preferably 50.0 mass% or more and 95.0 mass% or less, based on the total mass of the reaction liquid.

[0069] [Other ingredients] The first reaction liquid may contain various other components as necessary. Examples of other components include the same components that can be contained in the ink as described below. However, surfactants are not included in the water-soluble organic solvent.

[0070] [Physical properties of reaction solution] The first reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical property values. Specifically, the surface tension of the reaction liquid at 25°C is preferably 15 mN / m to 60 mN / m, more preferably 20 mN / m to 60 mN / m, and particularly preferably 20 mN / m to 45 mN / m. Of these, it is particularly preferable that it is 25 mN / m to 45 mN / m. In this specification, the surface tension of the ink (first ink, second ink) and the reaction liquid (first reaction liquid, second reaction liquid) is the "static surface tension" measured by the plate method. The surface tension of the ink and the reaction liquid can be measured as the static surface tension, for example, using a Wilhelmy type surface tensiometer (product name "Automatic Surface Tensiometer CBVP-Z", manufactured by Kyowa Interface Science).

[0071] The viscosity of the reaction solution at 25° C. is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the reaction solution at 25° C. is preferably 5.0 or more and 9.5 or less, more preferably 6.0 or more and 9.0 or less.

[0072] <Second reaction solution> The recording method of the present invention includes a second reaction liquid application step of applying a second reaction liquid, which is an aqueous reaction liquid containing a reactant that reacts with at least one aqueous ink selected from the group consisting of the first ink and the second ink, to a recording medium. Each component used in the second reaction liquid will be described in detail below.

[0073] [Reactants] The second 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. Among them, it is preferable that the second reaction liquid contains a polyvalent metal salt. The reactant may be used alone or in combination of two or more.

[0074] The content (mass %) of the polyvalent metal salt in the second 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 this specification, when the polyvalent metal salt is a hydrate, the "content (mass %) of the polyvalent metal salt in the reaction liquid means the "content (mass %) of the anhydrous polyvalent metal salt" excluding water as the hydrate.

[0075] 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 - , SO42- , 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 - and the like organic anions.

[0076] As the reactant of the second reaction liquid, it is preferable to use magnesium sulfate among polyvalent metal salts. That is, it is preferable that the polyvalent metal salt in the second reaction liquid is magnesium sulfate. This is because the speed at which solid components of the ink, such as particulate matter, are aggregated can be easily adjusted by the content of the reactant in the reaction liquid and the amount of the reaction liquid applied. When magnesium sulfate is used as the reactant, the content (mass%) of magnesium sulfate in the second reaction liquid is preferably 1.0 mass% or more and 15.0 mass% or less, based on the total mass of the reaction liquid, and more preferably 2.0 mass% or more and 10.0 mass% or less. The content (mass%) of magnesium sulfate in the second reaction liquid is preferably 0.8 times or more and 3.5 times or less, and more preferably 1.5 times or more and 3.5 times or less, in terms of mass ratio to the content (mass%) of magnesium sulfate in the first reaction liquid.

[0077] As described above, the reactant may be used alone or in combination of two or more. In particular, from the viewpoint of increasing the cohesive force of the ink, it is preferable that the second reaction liquid further contains a cationic resin. The content (mass %) of the cationic resin in the second reaction liquid is preferably 0.1 mass % or more and 10.0 mass % or less, and more preferably 0.2 mass % or more and 5.0 mass % or less, based on the total mass of the reaction liquid. Of these, it is particularly preferable that it is 0.5 mass % or more and 5.0 mass % or less.

[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 structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. 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.

[0079] 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 second reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0080] [Aqueous medium] The second reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. Examples of the aqueous medium used in the reaction liquid include the same aqueous medium as that which can be contained in the ink, which will be described later. The content (mass%) of the water-soluble organic solvent in the second reaction liquid is preferably 25.0 mass% or less, more preferably 10.0 mass% or less, and particularly preferably 5.0 mass% or less, based on the total mass of the reaction liquid. The content (mass%) of the water-soluble organic solvent in the second reaction liquid may be 0.0 mass%. In other words, the second reaction liquid may not substantially contain a water-soluble organic solvent. By setting the content of the water-soluble organic solvent within the above range, the proportion of water in the second reaction liquid increases by the amount of the water-soluble organic solvent reduced. As a result, the dynamic surface tension is likely to be high, and the second ink is less likely to spread when applied on the layer of the first ink. As a result, the bleeding of the second ink can be further suppressed, and the sharpness of the image can be further improved. In addition, when the first ink contains resin particles, the minimum image film temperature of the resin particles can be lowered by reducing the amount of the water-soluble organic solvent. Therefore, the layer of the first ink becomes soft, and bleeding of the image can be suppressed. The content (mass %) of water in the second reaction liquid is preferably 50.0 mass % or more and 95.0 mass % or less based on the total mass of the reaction liquid.

[0081] [Other ingredients] The second reaction liquid may contain various other components as necessary. Examples of other components include the same components that can be contained in the ink as described below. However, surfactants are not included in the water-soluble organic solvent.

[0082] [Physical properties of reaction solution] The second reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical property values. Specifically, the surface tension of the reaction liquid at 25°C is preferably 15 mN / m to 60 mN / m, more preferably 20 mN / m to 60 mN / m, and particularly preferably 20 mN / m to 45 mN / m. Of these, it is particularly preferable that it is 25 mN / m to 60 mN / m. In addition, the surface tension of the second reaction liquid must be higher than that of the first reaction liquid. Of these, the difference between the surface tension of the second reaction liquid and the surface tension of the first reaction liquid is preferably 0.5 mN / m to 15.0 mN / m, and more preferably 2.0 mN / m to 15.0 mN / m. The viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s to 10.0 mPa·s. The pH of the reaction solution 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.

[0083] <First ink> The first ink used in the recording method of the present invention is an aqueous inkjet ink containing at least one particulate material selected from the group consisting of pigments and resin particles. In other words, the first ink may be an ink that does not contain a pigment but contains resin particles. Such an ink is also called a clear ink. Each component used in the first ink will be described in detail below.

[0084] [Particulate matter] The first ink contains at least one particulate material selected from the group consisting of pigments and resin particles. The resin particles as particulate material include resin particles formed of acrylic resins, urethane resins, olefin resins, etc., and wax particles. The content (mass%) of the particulate material in the first ink is preferably 8.0% by mass or more based on the total mass of the ink. By making the content of the particulate material 8.0% by mass or more, the number of pores formed by the pigments and resin particles increases, and the capillary force acting on the second ink becomes stronger, so that the sharpness of the image can be further improved. The content (mass%) of the particulate material in the first ink is preferably 40.0% by mass or less, and more preferably 30.0% by mass or less.

[0085] [Pigment] The particulate matter in the first ink may be a pigment. The pigment content (mass %) in the ink is preferably 0.1% to 20.0% by mass, more preferably 0.5% to 20.0% by mass, and particularly preferably 0.2% to 15.0% by mass, based on the total mass of the ink. Of these, 1.0% to 15.0% by mass is particularly preferred.

[0086] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide, and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, etc. The pigments may be used alone or in combination of two or more.

[0087] As the dispersion method of the pigment, a resin-dispersed pigment using a resin as a dispersant, a self-dispersed pigment in which a hydrophilic group is bonded to the pigment particle surface, etc. can be used. In addition, a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the pigment particle surface, and a microcapsule pigment in which the surface of the pigment particle is coated with a resin, etc. can be used. It is also possible to use a combination of pigments with different dispersion methods among these. In particular, it is preferable to use a resin-dispersed pigment in which a resin as a dispersant is physically adsorbed on the pigment particle surface, rather than a resin-bonded pigment or a microcapsule pigment.

[0088] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin having an anionic group can be used, and it is preferable to use a resin as described below, especially a water-soluble resin. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0089] 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.

[0090] The pigment as particulate matter of the first ink is preferably titanium oxide. Titanium oxide has a relatively high surface free energy, which strengthens the capillary force acting on the second ink, which will be described later. As a result, bleeding of the second ink can be further suppressed.

[0091] Inorganic oxides such as titanium oxide react with water molecules constituting the aqueous medium in the aqueous ink to generate hydroxyl groups (hereinafter, sometimes referred to as "surface hydroxyl groups") on the surface. For this reason, in the case of aqueous inkjet inks, in order to utilize the generated surface hydroxyl groups while further improving the storage stability of the ink, the ink is generally used in a state where the ink is surface-treated with inorganic oxides such as alumina or silica. The surface hydroxyl groups of titanium oxide particles have properties specific to the inorganic oxide corresponding to the inorganic compound used in the surface treatment, and the isoelectric point, which is an indicator of the strength of the acid, differs depending on the type of inorganic compound. Therefore, although titanium oxide itself is an inorganic oxide, the surface of titanium oxide particles shows the properties of an inorganic oxide corresponding to the inorganic compound used in the surface treatment, and the surface charge of titanium oxide particles is strongly dependent on the pH of the aqueous medium, the type of surface treatment agent, and the amount of the surface treatment agent used.

[0092] Titanium oxide is a white pigment, and has three crystal forms: rutile, anatase, and brookite. Among them, rutile titanium oxide is preferred. Titanium oxide can be industrially produced by the sulfuric acid method and the chlorine method, and the titanium oxide used in the present invention may be produced by either method.

[0093] Titanium oxide may be surface-coated (surface-treated) with an inorganic oxide or an organic substance. In particular, titanium oxide surface-treated with alumina and silica is preferably used. The surface treatment is expected to suppress photocatalytic activity and improve dispersibility. In this specification, "alumina" is a general term for oxides of aluminum such as aluminum oxide. In this specification, "silica" is a general term for silicon dioxide or a substance composed of silicon dioxide. Most of the alumina and silica that coat titanium oxide are present in the form of silicon dioxide and aluminum oxide.

[0094] The ratio of alumina and silica in titanium oxide particles, i.e., the amount of alumina and silica coating, can be measured, for example, by quantitative analysis of aluminum and silicon elements by inductively coupled plasma (ICP) emission spectrometry. In this case, it is assumed that all atoms coating the surface are in the form of oxides, and the obtained values ​​of aluminum and silicon can be converted to the oxides, i.e., alumina and silica, to calculate the amount of alumina and silica.

[0095] Surface treatment methods for titanium oxide include wet treatment and dry treatment. For example, titanium oxide can be dispersed in a liquid medium and then reacted with a surface treatment agent such as sodium aluminate or sodium silicate to perform surface treatment, and the desired characteristics can be achieved by appropriately changing the ratio of these surface treatment agents. In addition to alumina and silica, inorganic oxides such as zinc oxide and zirconia, and organic substances such as polyols can also be used for surface treatment, as long as the effects of the present invention are not impaired.

[0096] [resin] The first ink may contain a resin. Resin particles may be used as the particulate matter of the first ink. The first ink may contain a water-soluble resin that can be dissolved in an aqueous medium. The resin may be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. Also, the resin may be added to the ink (ii) to improve various properties of the recorded image. Hereinafter, the water-soluble resin and the resin particles as the particulate matter may be collectively referred to as "resin".

[0097] The content (mass %) of the resin in the first ink is preferably 0.1% by mass or more and 20.0% by mass or less, and 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. When resin particles are used as the particulate material, the content (mass %) of the resin particles in the first ink is preferably 0.1% 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. One type of resin may be used alone, or two or more types may be used in combination.

[0098] [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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] [Resin properties] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, the resin is present in an aqueous medium in a state in which it does not form particles whose particle size can be measured by a dynamic light scattering method. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by a dynamic light scattering method, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3 times, and measurement time: 180 seconds. In addition, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used as a particle size distribution measuring device. Of course, the particle size distribution measuring device and the measurement conditions are not limited to those described above.

[0103] 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.

[0104] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 3,000,000 or less, more preferably 100,000 or more and 3,000,000 or less. The volume-based cumulative 50% particle diameter (D50) of the resin particles measured by dynamic light scattering 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 the particle diameter integration curve. The volume-based cumulative 50% particle diameter of the resin particles can be measured using the dynamic light scattering particle size analyzer and measurement conditions described above. The glass transition temperature of the resin particles is preferably 40°C or more and 120°C or less, more preferably 50°C or more and 100°C or less. The glass transition temperature (° C.) of the resin particles can be measured using a differential scanning calorimeter (DSC). The resin particles do not necessarily contain a coloring material.

[0105] [Wax particles] As the particulate material of the first ink, particles formed of wax (wax particles) can be used. By using an ink containing wax particles, an image with further 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 types. 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 0.5 mass % or more and 5.0 mass % or less, based on the total mass of the ink. Of these, it is particularly preferable that the content is 1.0 mass % or more and 5.0 mass % or less.

[0106] 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).

[0107] 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.

[0108] 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.

[0109] [Aqueous medium] The first ink used in the recording method of the present invention is an aqueous ink containing at least water as an aqueous medium. The first ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the first 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 first 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, may be used. The water-soluble organic solvent may be used alone or in combination of two or more.

[0110] [Other ingredients] The first ink may contain various other components as necessary. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the first ink does not contain a reactant to be contained in the reaction liquid.

[0111] [Ink properties] The first ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0112] <Second ink> The second ink used in the recording method of the present invention is a pigment-containing water-based ink for ink-jet recording. Each component of the second ink will be described in detail below.

[0113] [Colorant] The second ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably from 0.1 to 20.0% by mass, more preferably from 0.2 to 20.0% by mass, and particularly preferably from 1.0 to 15.0% by mass, based on the total mass of the ink.

[0114] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine. One type of pigment may be used alone, or two or more types may be used in combination. In particular, the pigment of the second ink is preferably at least one type selected from the group consisting of carbon black and organic pigments. This is because the surface free energy of the pigment is relatively low, and therefore the capillary force acting on the second ink is stronger.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] [resin] The second ink may contain a resin. The resin may be added to the ink (i) to stabilize the pigment dispersion state, i.e., as a resin dispersant or its auxiliary, or (ii) to improve various properties of the printed image.

[0119] The content (mass %) of the resin in the second ink is preferably 0.1% by mass or more and 20.0% by mass or less, and 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 of these. The resin may be used alone or in combination of two or more types.

[0120] The resin can be appropriately selected from those listed as usable for the first ink, and its properties can be determined in the same manner as those listed as usable for the first ink.

[0121] [Wax particles] The second ink may contain particles formed of wax (wax particles). By using an ink containing wax particles, an image with improved abrasion resistance can be recorded. In this specification, the wax may be a composition containing components other than wax, or the wax itself. The wax particles may be dispersed by a dispersant such as a surfactant or a resin. The wax may be used alone or in combination of two or more types. The content (mass %) of the wax particles in the second ink is preferably 0.1 mass % or more and 10.0 mass % or less, based on the total mass of the ink, and more preferably 0.5 mass % or more and 5.0 mass % or less. Of these, it is particularly preferable that the content is 1.0 mass % or more and 5.0 mass % or less.

[0122] The wax may be appropriately selected from those listed as usable for the first ink, and its properties may be determined in the same manner as those listed as usable for the first ink.

[0123] [Aqueous medium] The second ink used in the recording method of the present invention is an aqueous ink containing at least water as an aqueous medium. The second ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the second ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. The content (mass%) of the water-soluble organic solvent in the second ink is preferably 2.0% by mass or more and 40.0% by mass or less based on the total mass of the ink. The water-soluble organic solvent of the second ink may be appropriately selected from those listed as usable for the first ink. The water-soluble organic solvent may be used alone or in combination of two or more.

[0124] [Other ingredients] The second ink may contain various other components as necessary. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors. However, it is preferable that the second ink does not contain a reactant to be contained in the reaction liquid.

[0125] [Ink properties] The second ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0126] In order to easily suppress the wetting and spreading of the second ink applied on the first ink, the difference between the surface tension γ1 of the first ink and the surface tension γ2 of the second ink (γ2-γ1) is preferably -15.0 mN / m or more and 15.0 or less, and more preferably 2.0 mN / m or more and 15.0 or less. EXAMPLES

[0127] 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.

[0128] <Preparation of reaction solution> The components (unit: %) shown in the upper part of 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 the first and second reaction liquids, respectively. In Tables 1 to 3, "Catiomaster PDT-2" is the trade name of an amine-epichlorohydrin condensation polymer aqueous solution (cationic resin content: 60.0%) manufactured by Yokkaichi Synthetic. "Catiomaster PD7" is the trade name of an amine-epichlorohydrin condensation polymer aqueous solution (cationic resin content: 50.0%) manufactured by Yokkaichi Synthetic. "Acetylenol E100" is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. "BYK348" is the trade name of a silicone surfactant manufactured by BYK Chemie. "Proxel GXL (S)" is the trade name of a preservative manufactured by Arch Chemicals. The surface tension is shown in the lower part of Tables 1 and 2. The surface tension was measured at 25° C. using a Wilhelmy type surface tensiometer (product name "Automatic Surface Tensiometer CBVP-Z", manufactured by Kyowa Interface Science Co., Ltd.).

[0129] [Table 1]

[0130] [Table 2]

[0131] [Table 3]

[0132] <Preparation of pigment dispersion> (Pigment dispersion 1) 40.0 parts of titanium oxide, 1.2 parts of 3-(methoxy(polyoxyethylene)9-12)propyltrimethoxysilane, and ion-exchanged water with a total of 100.0 parts of the components were mixed and pre-dispersed using a homogenizer. Rutile-type titanium oxide (product name "TITANIX JR-403", surface treatment: alumina, silica) was used as the titanium oxide. Then, dispersion treatment was performed for 12 hours at 25°C using 0.5 mm zirconia beads with a paint shaker. The zirconia beads were filtered off, and an appropriate amount of ion-exchanged water was added as necessary to prepare pigment dispersion 1 with a pigment (titanium oxide particles) content of 40.0%.

[0133] (Pigment dispersion 2) 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%. 20.0 parts of pigment (carbon black), 30.0 parts of the aqueous solution of resin 1, and 50.0 parts of pure water were mixed to obtain a mixture. The obtained mixture and 200 parts of zirconia beads with a diameter of 0.3 mm were placed in a batch-type vertical sand mill (manufactured by Imex) and dispersed for 5 hours while cooling with water. After centrifuging to remove coarse particles, the mixture was pressure-filtered with a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare pigment dispersion 2 with a pigment content of 20.0% and a resin dispersant (resin 1) content of 6.0%.

[0134] (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 Blue 15:3. The pigment content was 20.0% and the resin dispersant (resin 1) content was 6.0%.

[0135] <Preparation of resin particles> (Resin particles 1) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant (trade name "Aqualon KH-05", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were mixed to prepare an emulsion. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over 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 40.0%.

[0136] (Resin particles 2) 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, 21.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, 3.0 parts of ethylene glycol dimethacrylate, 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 2 having a resin particle (solid content) content of 40.0%.

[0137] <Preparation of wax particles> Polyethylene wax (melting point 124°C), a dispersant, and ion-exchanged water were added to a container equipped with a stirrer, a thermometer, and a temperature controller. The temperature was raised to 160°C and stirred for 2 hours. A nonionic surfactant (product name "NIKKOL BC-10", manufactured by Nikko Chemicals, polyoxyethylene cetyl ether [number of ethylene oxide groups: 10]) was used as the dispersant. At this time, the cumulative 50% particle diameter (D 50The stirring conditions were adjusted so that the particle diameter was 180 nm. Thereafter, the temperature was cooled to 25° C., and an aqueous dispersion of wax particles with a wax particle (solid content) content of 35.0% was prepared.

[0138] <Ink Preparation> The components (unit: %) shown in the upper part of Tables 4 to 6 were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm to prepare the first ink and the second ink. However, for the ink using pigment dispersion 3, a cellulose acetate filter (manufactured by Advantech) with a pore size of 5.0 μm was used. In Tables 4 to 6, "Acetylenol E100" is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. "BYK348" is the trade name of a silicone surfactant manufactured by BYK Chemie. "Proxel GXL (S)" is the trade name of a preservative manufactured by Arch Chemicals. In Tables 4 to 6, the surface tension was measured using a Wilhelmy type surface tensiometer (trade name "Automatic Surface Tensiometer CBVP-Z", manufactured by Kyowa Interface Science) at 25°C.

[0139] [Table 4]

[0140] [Table 5]

[0141] [Table 6]

[0142] <Preparing the recording medium> The following recording media were prepared. Recording medium 1: Polyethylene terephthalate (PET) film (product name "PETWH50 PAT8LK", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption up to 2.5mL / m 2 ) Recording medium 2: Art paper (product name "Art PW8K", manufactured by Lintec, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption rate up to 9.5 mL / m 2 ) Recording medium 3: High-quality paper (product name "55PW8KCOC", manufactured by Lintec, 30 msec from the start of contact in the Bristow method 1 / 2 Water absorption rate up to 12.0 mL / m 2 ).

[0143] <Evaluation> The first reaction liquid, the second reaction liquid, the first ink, and the second ink shown in Table 7 were filled into a cartridge as a set. The cartridge was set in an inkjet recording device (product name "imagePROGRAF PRO-2000", manufactured by Canon) equipped with a recording head that ejects ink by thermal energy. A heating device for drying the recording medium to which the reaction liquid and the ink were applied by blowing air was incorporated into the recording device at a position downstream of the recording head in the conveying direction of the recording medium. The surface temperature of the recording medium was then heated to 80°C by the heating device. Using this recording device, the first reaction liquid was applied to a recording medium of the type shown in Table 7 in an area of ​​5 cm x 5 cm with a recording duty of 30% for the first reaction liquid and a recording duty of 300% for the first ink. The time difference between the application of the first reaction liquid and the application of the first ink was adjusted to 500 milliseconds by the operating speed of the conveying member 1300. Thereafter, a second reaction liquid was applied at a printing duty of 25% so as to overlap the area where the first reaction liquid and the first ink were applied, and then a ruled line of 1 dot width was recorded using the second ink. In 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 printing duty of 100%.

[0144] In this example, image sharpness was evaluated from two perspectives (line width and lagnetness). The line width evaluation was performed to evaluate the macroscopic image sharpness and to evaluate the degree of bleeding in the entire image. The lagnetness evaluation was performed to evaluate the microscopic image sharpness such as the edges of the image. In the present invention, the following evaluation criteria for each item were used, with "AA", "A" and "B" being acceptable levels and "C" being unacceptable. The evaluation results are shown on the right side of Table 7.

[0145] In Table 5, the order of each step is indicated as 1 to 5. The details are shown below. 1: First reaction liquid application step → First ink application step → Second reaction liquid application step → Second ink application step 2: First reaction liquid application step → First ink application step → Second ink application step → Second reaction liquid application step 3: First ink application process → second ink application process 4: First ink application step → second reaction liquid application step → second ink application step 5: First reaction liquid application step → First ink application step → Second ink application step (Sharpness: Line width) For the resulting ruled lines, the line width of 10 points of the ruled lines recorded with the second ink was measured using an optical microscope (product name "Axio Imager.Z2", manufactured by Carl Zeiss) and the average value was calculated. The line width was then evaluated according to the following evaluation criteria. The thinner the ruled lines, the less likely the second ink applied on top of the first ink will bleed. AA: Line width was 25 μm or less A: The line width was more than 25 μm and less than 30 μm. B: The line width was more than 30 μm and 35 μm or less. C: The line width was greater than 35 μm.

[0146] (Sharpness:Ladjetness) For the obtained ruled lines, the lag-jetness value of the boundary between the ruled lines recorded with the second ink and the background (the area where the first ink was applied) was measured at 10 points, and the average value was calculated. The lag-jetness value is a value defined by ISO-13660, and was measured in edge measurement mode using a handheld image quality analyzer (product name "PIAS-II", manufactured by Quality Engineering Associates). The lag-jetness was evaluated according to the following evaluation criteria. The smaller the lag-jetness value, the more the color mixing of adjacent images is suppressed, that is, the more the bleeding of the image is suppressed, and the sharpness of the image is high. AA: The laggetness score was 10 or less. A: The laggetness value was greater than 10 and less than 15. B: The laggetness score was greater than 15 and less than 20. C: The laggettiness value was over 20.

[0147] [Table 7]

[0148] The evaluation results of the lag jetness of Reference Examples 1 and 2 were "AA" like Example 1, but Example 1 was superior.

Claims

1. a first ink which is an aqueous ink containing at least one particulate material selected from the group consisting of pigments and resin particles; a second ink which is a water-based ink containing a pigment; a first reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink; and a second reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink; from a recording head and applied to a recording medium so as to overlap each other in at least a partial area of ​​the recording medium, thereby recording an image, a first reaction liquid applying step of applying the first reaction liquid to the recording medium; a first ink applying step of applying the first ink to the recording medium after the first reaction liquid applying step; a second ink applying step of applying the second ink to the recording medium after the first ink applying step; and a second reaction liquid applying step of applying the second reaction liquid to the recording medium after the first ink applying step, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ is as follows: The ink-jet recording method, wherein the second reaction liquid has a higher surface tension than the first reaction liquid.

2. The inkjet recording method according to claim 1 , wherein the first reaction liquid applying step, the first ink applying step, the second reaction liquid applying step, and the second ink applying step are carried out in this order.

3. The inkjet recording method according to claim 1 , wherein the content (% by mass) of the particulate matter in the first ink is 8.0% by mass or more.

4. 2. The ink jet recording method according to claim 1, wherein the pigment serving as the particulate matter in the first ink is titanium oxide.

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

6. The inkjet recording method according to claim 1, wherein the content (mass %) of the water-soluble organic solvent in the second reaction liquid is 25.0 mass % or less based on the total mass of the reaction liquid.

7. The inkjet recording method according to claim 1 , wherein the reactant in the first reaction liquid and the second reaction liquid contains a polyvalent metal salt.

8. 8. The ink-jet recording method according to claim 7, wherein the polyvalent metal salt in the first reaction liquid and the second reaction liquid is magnesium sulfate.

9. The inkjet recording method according to claim 7 , wherein the reactants in the first reaction liquid and the second reaction liquid further contain a cationic resin.

10. a first ink which is an aqueous ink containing at least one particulate material selected from the group consisting of pigments and resin particles; a second ink which is a water-based ink containing a pigment; a first reactive liquid, which is an aqueous reactive liquid containing a reactive agent that reacts with at least one type of ink selected from the group consisting of the first ink and the second ink; and a second reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink; from a recording head and applied to a recording medium so as to overlap each other in at least a partial area of ​​the recording medium, thereby recording an image, a first reaction liquid applying step of applying the first reaction liquid to the recording medium; a first ink applying step of applying the first ink to the recording medium after the first reaction liquid applying step; a second ink applying step of applying the second ink to the recording medium after the first ink applying step; and a second reaction liquid applying step of applying the second reaction liquid to the recording medium after the first ink applying step, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ is as follows: The inkjet recording apparatus according to claim 1, wherein the second reaction liquid has a higher surface tension than the first reaction liquid.

11. a first ink which is an aqueous ink containing at least one particulate material selected from the group consisting of pigments and resin particles; a second ink which is a water-based ink containing a pigment; a first reactive liquid, which is an aqueous reactive liquid containing a reactive agent that reacts with at least one type of ink selected from the group consisting of the first ink and the second ink; and a second reaction liquid which is an aqueous reaction liquid containing a reactant which reacts with at least one ink selected from the group consisting of the first ink and the second ink; a set of an aqueous ink and an aqueous reaction liquid for use in an ink jet recording method in which the aqueous ink and the aqueous reaction liquid are each ejected from a recording head and applied to a recording medium so as to overlap each other in at least a partial area of ​​the recording medium to record an image, The inkjet recording method comprises: a first reaction liquid applying step of applying the first reaction liquid to the recording medium; a first ink applying step of applying the first ink to the recording medium after the first reaction liquid applying step; a second ink applying step of applying the second ink to the recording medium after the first ink applying step; and a second reaction liquid applying step of applying the second reaction liquid to the recording medium after the first ink applying step, 30 msec from the start of contact of the recording medium in the Bristow method １／２ Water absorption up to 10 mL / m ２ is as follows: A set of an aqueous ink and an aqueous reaction liquid, wherein the second reaction liquid has a higher surface tension than the first reaction liquid.

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