Inkjet recording method, inkjet recording device, and ink set

Abstract

To provide an inkjet recording method that can suppress the occurrence of image unevenness when a first ink, which is a white ink, and a second ink, which is a non-white ink, are applied in that order to a low-to-non-absorbent recording medium. [Solution] The method includes a first ink application step of applying a first ink to a low-to-non-absorbent recording medium, a drying step of drying at least a portion of the liquid component of the first ink to form a first image, and a second ink application step of applying a second ink so as to overlap at least a portion of the first image to record an image. The first ink contains inorganic particles and first resin particles, and the total pore volume of the inorganic particles is 0.03 cm³. 3 The amount is 1 / g or more. The second ink contains pigment. The second ink application step is performed by a drying step, 30 msec from the start of contact in the Bristow method of the first image. 1 / 2 The water absorption capacity up to 1.0 mL / m² is 1.0 mL / m². 2 This will be done after the above steps have been completed.

Description

[Technical Field]

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

[0002] In recent years, inkjet recording methods have been used in fields such as commercial printing to record white images on non-white recording media such as transparent films, translucent films, and colored paper using white ink. In particular, when using low-to-non-absorbent recording media, where the ink has low or no ink absorption, the ink hardly penetrates the recording media, causing the applied ink to migrate on the recording media and resulting in image unevenness. Furthermore, when two or more types of ink are applied to a recording media, bleeding may occur due to contact between the inks.

[0003] There is a proposed inkjet recording method for recording images with suppressed bleeding by applying a reaction solution containing a coagulant and components that form an ink-receiving layer, along with two types of ink, to a low-to-non-absorbent recording medium (see Patent Document 1). There is also a proposed printing method for suppressing bleeding when recording images on a film, which is a low-to-non-absorbent recording medium, by applying color ink and white ink, and controlling the surface tension of the white ink (see Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-071738 [Patent Document 2] Japanese Patent Publication No. 2020-164571 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present inventors investigated a recording method in which white ink and non-white ink (color ink) are applied in that order to a low-to-non-absorbent recording medium, with reference to the descriptions in Patent Documents 1 and 2. As a result, it was found that image unevenness may occur.

[0006] Therefore, an object of the present invention is to provide an inkjet recording method that can suppress the occurrence of image unevenness when a first ink, which is a white ink, and a second ink, which is a non-white ink, are applied in that order to a low-to-non-absorbent recording medium. Another object of the present invention is to provide an inkjet recording apparatus and an aqueous ink used in the above inkjet recording method. [Means for solving the problem]

[0007] The above objective is achieved by the present invention as follows. Specifically, the inkjet recording method according to the present invention involves ejecting a first ink and a second ink, which are aqueous inks, from an inkjet recording head, and performing the Bristow method from the start of contact for 30 msec. 1 / 2 Water absorption capacity up to W m (mL / m 2 ) is 10.0 mL / m² 2 An inkjet recording method for recording an image on a recording medium, comprising: a first ink application step of applying the first ink to the recording medium; a drying step of drying at least a portion of the liquid component of the first ink applied to the recording medium to form a first image; and a second ink application step of applying the second ink so as to overlap at least a portion of the first image to record the image, wherein the first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume (cm³) of the inorganic particles is measured by a nitrogen adsorption desorption method. 3 ( / g) is 0.03cm 3 The amount is 1 / g or more, the second ink contains a pigment and is an ink of a different color from the first ink, and the second ink application step is performed by the drying step, 30 msec from the start of contact in the Bristow method of the first image. 1 / 2 Water absorption capacity up to W1 (mL / m³)2 ) at 1.0 mL / m 2 and then perform it.

Advantages of the Invention

[0008] According to the present invention, when a first ink which is a white ink and a second ink which is a non-white ink are applied to a low to non-absorbent recording medium in this order, it is possible to provide an inkjet recording method capable of suppressing the occurrence of image unevenness. Further, according to another embodiment of the present invention, it is possible to provide an inkjet recording apparatus and an aqueous ink used in the inkjet recording method.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic diagram for explaining an example of the image recording process. [Figure 2] It is a schematic diagram for explaining an example of the image recording process. [Figure 3] It is a side view schematically showing an embodiment of the inkjet recording apparatus of the present invention. [Figure 4] It is a perspective view schematically showing an embodiment of the inkjet recording apparatus of the present invention. [Figure 5] It is a side view schematically showing an embodiment of the inkjet recording apparatus of the present invention.

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in more detail by giving preferred embodiments. In the present invention, when the compound is a salt, although the salt is dissociated into ions in the ink, for convenience, it is expressed as "containing a salt". Further, an aqueous ink for inkjet and an aqueous reaction solution may be simply described as "ink" and "reaction solution". Physical property values are values at normal temperature (25 ° C) and normal pressure (1 atm) unless otherwise specified. In the present invention, for convenience, the density of the aqueous ink is 1 g / cm 3It shall be treated as (1 g / mL). Hereinafter, inks of colors other than white ink may be referred to as "non-white ink". For convenience, in this invention, the density of the water-based ink shall be 1 g / cm³. 3 Treat as (1g / mL).

[0011] The inventors investigated the factors causing image unevenness in images recorded on a low-to-non-absorbent recording medium by applying a first ink, which is a white ink, and a second ink, which is an ink of a different color (non-white ink), in that order. Here, the water-based white ink used in inkjet recording methods usually contains a colorant suitable for making white ink, and resin particles to ensure the strength of the recorded image, such as scratch resistance. In a white image recorded by applying white ink to a recording medium, the colorant is bound by the resin.

[0012] When applying non-white ink to overlap areas where white ink is applied, thereby recording a non-white image on a white background, the liquid component of the non-white ink does not easily penetrate the white ink layer, and convection and evaporation of the liquid component of the non-white ink are likely to occur on the white ink layer. Furthermore, the white ink layer repels the non-white ink, causing the colorant of the non-white ink to move from its intended position. Due to these factors, images recorded by applying non-white ink to overlap areas where white ink is applied are prone to unevenness. This is particularly true in the Bristow method, from the start of contact for 30 msec. 1 / 2 The water absorption capacity up to 10.0 mL / m² is 10.0 mL / m². 2 When using low-to-non-absorbent recording media, the liquid component of non-white ink is not easily absorbed not only by the white ink layer but also by the recording media. Consequently, image unevenness becomes more pronounced.

[0013] The present inventors investigated the configuration of an inkjet recording method that can suppress the occurrence of image unevenness when recording an image on a low to non-absorbent recording medium by applying white ink and then non-white ink in that order. As a result, they found that the occurrence of image unevenness can be suppressed by satisfying the following requirements (i) to (iv), leading to the present invention. (i) The process includes a first ink application step of applying a first ink to a recording medium, and a second ink application step of applying a second ink so as to overlap at least a portion of the area to which the first ink has been applied (this area is the "first image" described later in (iv)) to record an image. (ii) The first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume measured by nitrogen adsorption desorption of the inorganic particles is 0.03 cm³. 3 It is 1 / g or more. (iii) The second ink contains a pigment and is a different color from the first ink. (iv) After the first ink application step, there is a drying step in which at least a portion of the liquid component of the first ink applied to the recording medium is dried to form the first image. The second ink application step is performed by the drying step, and the first image is formed in the Bristow method from the start of contact for 30 msec. 1 / 2 Water absorption capacity up to W1 (mL / m³) 2 ) 1.0 mL / m² 2 This will be done after the above steps have been completed.

[0014] Figures 1 and 2 are schematic diagrams illustrating an example of the image recording process. The first ink, which is white ink, has a total pore volume of 0.03 cm³ as measured by nitrogen adsorption desorption. 2 The first ink contains inorganic particles 1 and first resin particles 2, with a concentration of 0.03 cm³ or more. When the first ink is applied to the recording medium, an ink film is formed in which the inorganic particles 1 and first resin particles 2 in the ink are densely packed, as shown in Figure 1. Subsequently, in the drying process, at least a portion of the liquid component of the first ink applied to the recording medium is reduced by drying. The inorganic particles 1 have a total pore volume of 0.03 cm³ as measured by nitrogen adsorption desorption. 3These are porous particles with the characteristic of being 1 / g or more. When at least a portion of the liquid component of the first ink decreases during the drying process, the liquid component held by the porous particles decreases, so voids originating from the porous inorganic particles 1 are created in the ink film formed on the recording medium by the first ink. In addition, since the first ink contains first resin particles, the solid content of the first ink is higher and the liquid component is lower compared to when the resin particles are not present. These factors work together to increase the efficiency of the drying process, and the liquid component is rapidly reduced from the ink film formed on the recording medium by the first ink. As a result, the first image formed by drying at least a portion of the liquid component of the first ink becomes more readily able to absorb new liquid components due to the voids originating from the inorganic particles.

[0015] Next, a second ink containing pigment is applied so as to overlap at least a portion of the first image. In this case, the first image is obtained 30 msec from the start of contact in the Bristow method. 1 / 2 The water absorption capacity W1 is 1.0 mL / m². 2 The above conditions must be met. Since the first image that satisfies these requirements readily absorbs liquid components, the liquid components of the second ink applied to the first image are quickly absorbed into the voids originating from the inorganic particles in the first image. As a result, the pigment concentration and viscosity of the second ink increase rapidly, making it less likely for the second ink to be repelled by the first image, thus suppressing pigment movement and preventing image unevenness. On the other hand, in the Bristow method, 30 msec from the start of contact 1 / 2 The water absorption capacity W1 is 1.0 mL / m². 2 If the value is less than this, the first image cannot quickly absorb the liquid component of the second ink, and the second ink is easily repelled by the first image. As a result, pigment migration cannot be suppressed, and image unevenness occurs.

[0016] In the recording methods described in the aforementioned Patent Documents 1 and 2, the amount of water absorbed by the white ink layer is small, which is thought to have resulted in uneven image absorption because the liquid components of the color ink were not easily absorbed. The small amount of water absorbed by the white ink layer is due to the small amount of inorganic particles in the white ink, as well as the small amount of ink applied.

[0017] <Inkjet recording method, inkjet recording device, and ink set> The present invention relates to an inkjet recording method that records an image on a low-to-non-absorbent recording medium by ejecting a first ink and a second ink, which are aqueous inks, from an inkjet recording head. The low-to-non-absorbent recording medium is used in the Bristow method from the start of contact for 30 msec. 1 / 2 Water absorption capacity up to W m (mL / m 2 ) is 10.0 mL / m² 2 The method is as follows: This method comprises the following steps: a first ink application step of applying a first ink to a recording medium; a drying step of drying at least a portion of the liquid component of the first ink applied to the recording medium to form a first image; and a second ink application step of applying a second ink so as to overlap at least a portion of the first image to record an image. The first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume (cm³) of the inorganic particles is measured by nitrogen adsorption desorption. 3 ( / g) is 0.03cm 3 The amount is 1 / g or more. Furthermore, the second ink contains a pigment and is a different color from the first ink. The second ink application process is carried out by a drying process, 30 msec from the start of contact in the Bristow method of the first image. 1 / 2 Water absorption capacity up to W1 (mL / m³) 2 ) 1.0 mL / m² 2 This will be done after the above steps have been completed.

[0018] The inkjet recording apparatus of the present invention is an apparatus that records an image on a recording medium by ejecting first and second water-based inks from an inkjet recording head, and is suitably used in the above-described recording method. In the present invention, there is no need to include a step of curing the image by irradiation with active energy rays or the like.

[0019] Furthermore, the ink set of the present invention is an ink set comprising a first ink and a second ink, both of which are water-based inks, used in an inkjet recording method in which an image is recorded on a recording medium by ejecting ink from an inkjet recording head. The ink is also suitably used in the above-described recording method.

[0020] The inkjet recording method and inkjet recording apparatus of the present invention (hereinafter also simply referred to as "recording method and recording apparatus") will be described in detail below.

[0021] Figure 3 is a schematic side view showing one embodiment of the inkjet recording apparatus of the present invention. The inkjet recording apparatus A shown in Figure 3 is an inkjet recording apparatus that records an image on a recording medium wound in a roll shape using a reaction liquid containing a reactant that reacts with ink and ink. The X, Y, and Z directions represent the width (overall length), depth, and height directions of the inkjet recording apparatus, respectively. The recording medium is transported in the X direction.

[0022] The inkjet recording apparatus A of the embodiment shown in Figure 3 is configured to include a first recording unit 1100, a first drying unit 2000, a second recording unit 1200, a second drying unit 2300, and a paper discharge unit 4000. In the first recording unit 1100, a white image is recorded by applying various liquids, including the first ink, to the recording medium 1000, which has been transported from the paper feed device 1400 by the transport member 1300, using the first liquid application device 1101 (first ink application step). In the first drying unit 2000, the recording medium 1000 is transported along the first transport member 2200 while maintaining tension. At this time, in the first drying unit 2000, the liquid including the first ink applied to the recording medium 1000 is dried by blowing air from the first drying device 2100, etc., and the liquid components such as water in the ink are evaporated to dry it (drying step).

[0023] In the second recording unit 1200, similar to the first ink, various liquids, including the second ink, are applied by the second liquid application device 1201 to record a non-white image on a white background (second ink application step). In the second drying unit 2300, the recording medium 1000 is transported along the second transport member 2500 while maintaining tension. At this time, in the second drying unit 2300, the liquid including the second ink applied to the recording medium 1000 is dried by blowing air from the second drying device 2400, etc., to evaporate liquid components such as water in the ink and dry it. Although not shown in Figure 3, a cooling step may be further performed to cool the recording medium 1000 after the drying steps in the first drying unit 2000 and the second drying unit 2300.

[0024] The recording medium 1000 on which the image is recorded is transported in the paper discharge section 4000 while being supported by a support member 4100, and then wound up by a winding device 4200. The recording device shown in Figure 3 is a configuration in which an image is recorded on a roll-shaped recording medium, but the recording medium is not limited to a roll shape, and a sheet-shaped recording medium can also be used by changing the recording medium transport method and the paper discharge device.

[0025] [Records Department] The recording unit consists of a first recording unit 1100 that dispenses a liquid containing a first ink, and a second recording unit 1200 that dispenses a liquid containing a second ink. The first recording unit 1100 has a first liquid dispensing device 1101. The first liquid dispensing device 1101 is configured to include a first reaction liquid dispensing device 1102 and a first ink dispensing device 1103. The second recording unit 1200 has a second liquid dispensing device 1201. The second liquid dispensing device 1201 is configured to include a second reaction liquid dispensing device 1202 and a second ink dispensing device 1203.

[0026] The first reaction solution dispenser 1102 and the second reaction solution dispenser 1202 shown in Figure 3 are examples of units using an inkjet ejection head. Other reaction solution dispensers may be configured using gravure coaters, offset coaters, die coaters, blade coaters, etc. The application methods of the first reaction solution dispenser 1102 and the second reaction solution dispenser 1202 may be the same or different. The application of the reaction solution by the first reaction solution dispenser 1102 and the second reaction solution dispenser 1202 may be before or after ink application, as long as the reaction solution can come into contact with the ink on the recording medium 1000. However, in order to record high-quality images on various recording media with different liquid absorption characteristics, it is preferable to apply the reaction solution before ink application. The first ink dispenser 1103 and the second ink dispenser 1203 use an inkjet ejection head (recording head). The dispensing methods of the dispensing heads of the first liquid dispensing device 1101 and the second liquid dispensing device 1201 include a method of dispensing liquid by generating film boiling in the liquid using an electro-thermal converter and forming bubbles, and a method of dispensing liquid using an electro-mechanical converter. The dispensing methods of the first ink dispensing device 1103 and the second ink dispensing device 1203 may be the same or different. In addition, the first reaction solution used in combination with the first ink and the second reaction solution used in combination with the second ink may be the same or different.

[0027] The first liquid dispensing device 1101 and the second liquid dispensing device 1201 are line heads extending in the Y direction, with discharge ports arranged to cover the image recording area of ​​the maximum usable width of the recording medium. The discharge head has a discharge port surface with discharge ports formed below it (towards the recording medium 1000), and the discharge port surface faces the recording medium 1000 at a very small distance of a few millimeters.

[0028] The following explanation will use the case where the first ink is ejected from the first ink dispenser 1103 and the second ink is ejected from the second ink dispenser 1203 as an example. Multiple second ink dispensers 1203 may be provided to dispense each color of ink onto the recording medium 1000. For example, when recording images of each color using yellow ink, magenta ink, cyan ink, and black ink as the second ink, four second ink dispensers 1203, each ejecting these four types of ink, are arranged in a line in the X direction. The color tones and application order of the first and second inks are not limited to the above. Hereinafter, the ink and reaction solution may be collectively referred to as "liquid".

[0029] [Conveyor System] As shown in Figure 3, the first recording unit 1100 is configured to include a first liquid application device 1101 and a transport member 1300 for transporting the recording medium 1000. The first liquid application device 1101 applies the reaction liquid and ink to desired positions on the recording medium 1000 transported by the transport member 1300. The first reaction liquid application device 1102 and the first ink application device 1103 receive the image signal of the recorded data and apply the reaction liquid and ink to predetermined positions, respectively. The second recording unit 1200 is configured to include a second liquid application device 1201 and a transport member 1300 for transporting the recording medium 1000, and similarly applies the reaction liquid and ink to predetermined positions, respectively.

[0030] If the recording medium 1000 is in sheet form, a transport member 1300 capable of fixing and transporting the recording medium 1000 can be used. Specifically, this can involve using a transport belt, spurs, or transport cylinder, providing holes in the transport member 1300, and fixing the recording medium 1000 by suction from the back side; or forming the transport member 1300 from an appropriate material and fixing the recording medium 1000 by electrostatic attraction.

[0031] [Drying section] As shown in Figure 3, the first drying unit 2000 is configured with a first drying device 2100 and a first transport member 2200. Similarly, the second drying unit 2300 is configured with a second drying device 2400 and a second transport member 2500. In the first drying unit 2000, the recording medium 1000 to which the first ink has been applied is transported by the first transport member 2200, and the liquid component of the first ink is dried by the first drying device 2100, thereby evaporating the liquid component in the ink. In the drying process, it is not necessary to evaporate all of the liquid component of the first ink. Also, in the second drying unit 2300, the recording medium 1000 to which the first ink and the second ink have been applied is transported by the second transport member 2500, and the liquid component of the second ink is dried by the second drying device 2400, thereby evaporating the liquid component in the ink. In the drying process, it is not necessary to evaporate all of the liquid component of the second ink.

[0032] The first drying apparatus 2100 and the second drying apparatus 2400 can have any configuration as long as they can dry at least a portion of the liquid components on the recording medium 1000, and known devices such as fans and heaters can be used. By drying the recording medium 1000 while heating it, the liquid components of the first and second inks can be dried more efficiently. When using a heating device as the drying apparatus, it is preferable to use a non-contact heater such as an electric heating wire or infrared heater from the standpoint of safety and energy efficiency. By blowing heated gas onto the recording medium 1000 using fans built into the first drying apparatus 2100 and the second drying apparatus 2400, the drying efficiency can be further increased. Based on the transport speed and ambient temperature, conditions such as the temperature of the drying means can be set so that the recording medium reaches the desired temperature.

[0033] If the first drying apparatus 2100 and the second drying apparatus 2400 are equipped with a blower, it is preferable to blow air from the side of the recording medium 1000 to which the liquid has been applied (the recording surface (front)). Furthermore, if the first drying apparatus 2100 and the second drying apparatus 2400 are heating devices, the recording medium 1000 may be heated from the front side, from the back side, or from both sides. In addition, the first transport member 2200 and the second transport member 2500 may also be equipped with a heating function.

[0034] In the first drying section 2000 and the second drying section 2300, when drying the recording medium 1000 while heating, a temperature T is set to be equal to or higher than the glass transition temperature Tg (°C) or melting point Tm (°C) of the first resin particles in order to melt the first resin particles of the first ink. H It is preferable to heat at (°C). That is, the drying temperature T H The temperature (°C) is preferably set according to the glass transition temperature Tg (°C) or melting point Tm (°C) of the first resin particles. If the first resin particles are crystalline resin, they have a glass transition temperature Tg (°C) and a melting point Tm (°C), so it is preferable to heat them to a temperature above the melting point Tm (°C) in order to melt the first resin particles. Specifically, the drying temperature T in the first drying section 2000 HThe drying temperature (°C) is preferably 70°C or higher, more preferably 80°C or higher, and particularly preferably 90°C or higher. H The temperature (°C) is preferably 200°C or lower, more preferably 150°C or lower, and particularly preferably 130°C or lower, from the viewpoint of the heat resistance temperature of the recording medium. H Preferably, (°C) is less than the glass transition temperature Tg (°C) or melting point Tm (°C) of the inorganic particle 1.

[0035] Drying temperature T H (°C) represents the highest temperature reached by the recording medium (surface) during the drying process. Drying temperature T H The temperature in degrees Celsius (°C) can be measured using, for example, a contact thermometer that brings a thermocouple or the like into contact with the recording medium, or a non-contact infrared thermometer. In the embodiment described later, the temperature on the surface of the recording medium was measured using a non-contact thermometer (product name "Non-contact infrared thermometer digital radiation temperature sensor FT-H20", manufactured by Keyence) from a position 10 cm vertically upward from the surface of the recording medium.

[0036] Figure 2 shows the drying temperature T. H This is a schematic diagram illustrating an example of the image recording process when (°C) is set to be equal to or higher than the glass transition temperature Tg (°C) or melting point Tm (°C) of the first resin particle. H By setting the drying temperature (°C) to be equal to or greater than the glass transition temperature Tg(°C) or melting point Tm(°C) of the first resin particle, the first resin particle 2 melts. The resin produced by the melting of the first resin particle 2 penetrates into the voids originating from the inorganic particle 1, and voids 4 are formed where the first resin particle 2 was located (Figure 2). Drying temperature T H (°C) is the glass transition temperature Tg of inorganic particle 1. I (°C) or melting point Tm IIf the temperature is below (°C), the inorganic particles 1 do not melt. The resin generated by the melting of the first resin particles penetrates the voids originating from the inorganic particles 1, forming a binder 3 which is a mixture of particles 1 and the melted particles. The white image recorded in this way has voids 4 inside. The air present in the voids 4 has a low refractive index, and the incident light is scattered due to the refractive index difference between the binder 3 and the voids 4, thus a white image with high opacity can be obtained.

[0037] [Paper output section] After image recording, the recording medium 1000 is stored in the paper discharge unit 4000 (Figure 3). After recording in the first recording unit 1100, the recording medium 1000 passes through the first drying unit 2000, then records in the second recording unit 1200, and then passes through the second drying unit 2300 before being transported by the transport member 4100. The recording medium 1000 is finally stored in a rolled state by the paper discharge device 4200. Two or more paper discharge devices 4200 may be provided to accommodate different recording materials, for example.

[0038] Figure 4 is a schematic perspective view showing another embodiment of an inkjet recording device, different from that shown in Figure 3. Figure 5 is a side view of Figure 4. The recording device of the embodiment shown in Figures 4 and 5 includes an inkjet recording head 22 that ejects ink. The recording head may be equipped with a mechanism (temperature control mechanism) for heating the aqueous ink ejected from the recording head. If a 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.

[0039] The inkjet recording device shown in Figure 4 can perform so-called multi-pass recording, in which ink is applied to a unit area of ​​the recording medium by multiple relative scans between the recording head and the recording medium. The unit area can be set to any area, such as one pixel or one band. This device can apply the first ink and the second ink to the unit area of ​​the recording medium by different relative scans. This allows for a time interval before the first and second inks come into contact with each other, and dries at least a portion of the liquid component of the first ink, resulting in a water absorption amount W1 (mL / m²). 2 ) 1.0 mL / m² 2 Making it even larger than this is easily achievable.

[0040] A drying device (Figure 5) for performing a drying process is provided upstream or downstream of the transport direction of the recording medium 10, which intersects with the main scanning direction in which the recording head 22 reciprocates. After the first ink is applied to the recording medium 10, and before the second ink is applied, the drying device 28 dries at least a portion of the liquid component of the first ink (drying process). In the drying process, it is not necessary to dry all of the liquid component of the first ink, and when the second ink is applied to the first image from which at least a portion of the liquid component has evaporated, the amount of water absorbed W1 (mL / m³) is reduced. 2 ) is 1.0 mL / m² 2 The above is sufficient. The drying apparatus 28 can have any configuration as long as it can promote the evaporation of the liquid component of the first ink on the recording medium 10, and known devices such as a fan or other blower, or a heater or other heating device can be used. Drying temperature T H The temperature (°C) should be set in the same way as in the case of the inkjet recording device shown in Figure 3.

[0041] In the recording apparatus shown in Figures 4 and 5, a heater 25 supported by a frame (not shown) is positioned downstream of the recording head 22 in the sub-scanning direction A, relative to the position where the recording head 22 reciprocates in the main scanning direction B. The heater 25 heats the ink-coated recording medium 10. Examples of heaters 25 include sheath heaters and halogen heaters. The heater 25 is covered by a heater cover 26. The heater cover 26 is a component that efficiently irradiates the recording medium 10 with the heat generated by the heater 25. The heater cover 26 also serves to protect the heater 25. After the second ink is applied, the heater 25 evaporates the liquid component in the ink, drying the image. Drying temperature T H The temperature (°C) should be set in the same way as in the case of the inkjet recording device shown in Figure 3.

[0042] After image recording, the recording medium 10 is wound up by the take-up spool 27 to form a roll-shaped winding medium 24. The recording apparatus shown in Figures 4 and 5 records images on a roll-shaped recording medium, but the recording medium is not limited to a roll shape. By changing the recording medium transport method and the paper discharge device, a sheet-shaped recording medium can also be used.

[0043] (Recording medium) As the recording medium, a low-absorption or non-absorption recording medium (low to non-absorption recording medium) is used. In this specification, "low to non-absorption recording medium" refers to a recording medium that, in the Bristow method, lasts for 30 msec from the start of contact. 1 / 2 Water absorption capacity up to W m (mL / m 2 ) is 10 mL / m² 2 The following recording media are referred to. The Bristow method is a widely used method for measuring the amount of liquid absorbed in a short time and is also adopted by the Japan Paper & Pulp Technology Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51, "Paper and Paperboard - Liquid Absorbency Test Method - Bristow Method," of the "JAPAN TAPPI Paper & Pulp Test Methods 2000 Edition." Recording media with an ink-receiving layer for inkjet recording (glossy paper, matte paper, etc.) and plain paper without a coating layer have the above water absorption amount Wm 10 mL / m² 2 It is a "highly absorbent recording medium" that exceeds [a certain limit].

[0044] Examples of low-absorption recording media include recording media without an ink-receiving layer and recording media with a thin ink-receiving layer. Examples of printing papers include art paper, fine coated paper, medium coated paper, fine lightweight coated paper, medium lightweight coated paper, lightly coated paper, and cast coated paper. Examples of non-absorbent recording media include recording media without an ink-receiving layer and recording media with a thin ink-receiving layer. Examples of plastics include plastic films and materials such as paper on which plastic is coated. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene. Other examples include glass, metal, and ceramic. Among these, materials such as plastic films and materials such as paper on which plastic is coated are preferred. In this specification, "recording media" means an object on which an image is recorded as a recording, not a transfer medium.

[0045] Since the first ink is a white ink capable of recording images such as white, it is preferable to use a recording medium other than white, such as a transparent film, a translucent film, or colored paper. Here, "white" refers to the same characteristics as the "white" of the first ink described later.

[0046] (First ink) The first ink used in the recording method is a white, water-based inkjet ink containing inorganic particles and first resin particles. Here, "white ink" includes inks that do not appear white in their ink state but are capable of recording white images. White refers to CIEL * a * b * Lightness (L) in a color system * ) and chromaticity (a * , b * ) are, respectively, 70 ≤ L *≤100, -4.5 ≤a * ≤2.0, -6.0 ≤b * This means the value is within the range of ≤2.5. The components that make up the ink will be explained in detail below.

[0047] [Inorganic particles] The first ink contains inorganic particles. The inorganic particles may be colorants or non-colorful particles such as resin particles. In particular, since a white image is to be recorded, it is preferable to use colorless or white inorganic particles. The total pore volume of the inorganic particles, as measured by nitrogen adsorption desorption, is 0.03 cm³. 3 The amount must be at least / g. The total pore volume of inorganic particles is determined by the nitrogen adsorption and desorption isotherm measured by the nitrogen adsorption and desorption method. The total pore volume of inorganic particles is 0.20 cm³. 3 It is preferable that the amount is 1 / g or more. Furthermore, the total pore volume of the particles should be 1.00 cm³. 3 It is preferable that it be less than or equal to / g, and 0.80cm 3 It is even more preferable that the amount be less than or equal to / g.

[0048] [Content] Content V of inorganic particles in the first ink I The (volume %) is preferably 1.5 volume% to 5.0 volume%, based on the total volume of the ink. Also, the content of inorganic particles in the first ink C I The (mass%) is preferably 5.0% by mass or more and 45.0% by mass or less, based on the total mass of the ink, and more preferably 5.0% by mass or more and 40.0% by mass or less.

[0049] [Particle size] Inorganic particles are typically dispersed in ink in the form of secondary particles, which are aggregates of two or more primary particles. The average primary particle diameter of inorganic particles is D. I The (nm) is preferably 150 nm or less, more preferably 50 nm or less, and particularly preferably 30 nm or less. Average primary particle diameter D of inorganic particles IThe (nm) is preferably 5 nm or greater. The average primary particle diameter of inorganic particles can be measured by observing the inorganic particles using a scanning electron microscope. Average primary particle diameter D of inorganic particles P0 (nm) can be calculated as the average value of the primary particle diameters of multiple inorganic particles (for example, 100 particles).

[0050] Inorganic particles are typically dispersed in ink as secondary particles formed by the aggregation of two or more primary particles. Volume-based cumulative 50% particle size D50 I Inorganic particles with small (nm) dimensions do not scatter visible light easily. Therefore, when using a first ink containing such inorganic particles, the opacity of the white image recorded by the first ink may be reduced. In addition, the color reproduction of a color image recorded with the second ink on top of a white image recorded with the first ink (hereinafter sometimes referred to as "non-white image on a white background") may be reduced. However, the total pore volume measured by nitrogen adsorption desorption is 0.03 cm³. 3 Inorganic particles with a density of 1 / g or more are porous materials, and the high refractive index of the air contained in the pores of the inorganic particles causes scattering of visible light. This tends to increase the opacity of images recorded by the first ink. It also tends to increase the color development of non-white images on a white background. In addition, as mentioned above, in the drying process, the temperature T is higher than the glass transition temperature Tg (°C) or melting point Tm (°C) of the first resin particles. H By heating at (°C), the first resin particles melt, creating voids. These voids allow for efficient scattering of incident light, further improving the opacity of images recorded with the first ink and the color development of non-white images on a white background.

[0051] Volume-based cumulative 50% particle size D50 of inorganic particles IThe (nm) is preferably between 5 nm and 250 nm, and more preferably between 5 nm and 200 nm. In this specification, "50% cumulative particle diameter based on volume" is the diameter of the particle that, when accumulated from the smallest particle diameter side, is the total volume of the measured particles in the particle diameter integration curve, and can be measured using a particle size distribution analyzer that uses dynamic light scattering. For example, measurement conditions include SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: non-spherical. As the particle size distribution analyzer, a particle size analyzer that uses dynamic light scattering (for example, product name "UPA-EX150", manufactured by Nikkiso) can be used. Of course, the particle size distribution analyzer and measurement conditions used are not limited to those described above.

[0052] 〔density〕 The density of the particles is preferably the same as or greater than that of the first resin particles. In particular, the density of the particles is preferably greater than that of the first resin particles. I (g / cm 3 ) is 1.00 g / cm³ 3 More than 5.00g / cm 3 Preferably, the following is true: 2.00 to 5.00 g / cm³ 3 It is even more preferable that the following is true: 4.00 to 5.00 g / cm³ 3 The following is particularly preferable:

[0053] [Refractive index] Since inorganic particles become part of the material that constitutes the white ink layer (binder), it is preferable to use those with a high refractive index. Specifically, it is preferable that the refractive index of the inorganic particles be between 2.0 and 3.0. Among these, it is preferable to use titanium dioxide, which has a relatively high refractive index, as the inorganic particles. The refractive index of titanium dioxide is preferably 2.1 or higher, and more preferably 2.5 or higher and 2.8 or lower.

[0054] [Preferred materials] The inorganic particles are preferably white pigments. Specifically, examples include titanium dioxide, calcium carbonate, aluminum oxide, calcium phosphate, barium sulfate, zirconium oxide, silicon dioxide, kaolin, clay, magnesium carbonate, calcium sulfate, magnesium sulfate, calcium hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, zinc oxide, synthetic amorphous silica, colloidal silica, wet silica, and dry silica. Among these, white pigments such as titanium dioxide, calcium carbonate, and aluminum oxide are preferred, with titanium dioxide being particularly preferred.

[0055] Titanium dioxide exists in three crystalline forms: rutile, anatase, and brookite. Among these, rutile titanium dioxide, which has low photocatalytic activity, is preferred. Industrial methods for producing titanium dioxide include the sulfuric acid method and the chlorine method; titanium dioxide produced by either method can be used. The particle surface of titanium dioxide may be coated with alumina or zirconia. Alternatively, the particle surface may be coated with inorganic oxides such as silica, zinc oxide, and zirconia; or organic substances such as polyols. Using titanium dioxide with a coated particle surface is expected to suppress photocatalytic activity and improve dispersibility. Calcium carbonate particles can be cubic or spindle-shaped. Among these, cubic calcium carbonate with a uniform shape is preferred. Aluminum oxide includes α-alumina, γ-alumina, and nanoalumina.

[0056] One method for dispersing inorganic particles is to apply energy (mechanical or thermal) to a liquid medium containing the inorganic particles to disperse them. Furthermore, from the viewpoint of stably maintaining the dispersion state of the inorganic particles, it is preferable to use a dispersant. For example, for inorganic particles with a low isoelectric point and a negative surface charge in an aqueous medium, such as dry silica, it is preferable to use a cationic resin as the dispersant. For inorganic particles with a positive surface charge, such as alumina hydrate, it is preferable to use an anionic component as the dispersant. Dispersion can also be achieved by physically adsorbing the dispersant onto the surface of the inorganic particles. Dispersants are preferable because they can effectively suppress the aggregation of inorganic particles due to intermolecular electrical repulsion and steric hindrance. Dispersants can be appropriately selected according to the characteristics of the inorganic particles, such as acids, alkalis, and resins. The content (mass%) of the dispersant in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the content (mass%) of the inorganic particles. If the dispersant content is less than 0.5% by mass, the dispersion state of inorganic particles tends to become unstable and may aggregate easily. Conversely, if the dispersant content exceeds 15.0% by mass, there is an excess of dispersant, which can also destabilize the dispersion state of inorganic particles and make them prone to aggregation.

[0057] [Resin particles] The first ink contains first resin particles. By containing first resin particles together with inorganic particles, the recorded image is in a state where the inorganic particles are bound together by the resin, thereby ensuring image strength. Furthermore, by using a first ink containing first resin particles, the water content can be reduced by the amount of first resin particles. Therefore, the amount of water absorbed in the first image formed by drying at least a portion of the liquid component of the first ink applied to the recording medium after the first ink application process can be quickly reduced. This makes it easier to suppress the occurrence of image unevenness. The resin particles do not need to be "hollow particles" that have voids inside.

[0058] In this specification, "resin particles" refers to resins that exist in an insoluble state in the aqueous medium of ink, and more specifically, resins that can exist in the aqueous medium in a state in which particles whose particle size can be measured by dynamic light scattering are formed. In contrast, "water-soluble resins" refer to resins that exist in a dissolved state in the aqueous medium of ink. Whether or not a resin qualifies as "resin particles" can be determined according to the method shown below. First, a liquid containing the resin to be judged is prepared and diluted with pure water to prepare a sample so that the resin content is approximately 1.0%. Then, when the particle size of the resin in the sample is measured by dynamic light scattering, if particles with a particle size are measured, the resin is determined to be "resin particles" (i.e., "water-dispersible resin"). On the other hand, if particles with a particle size are not measured, the resin is determined not to be "resin particles" (i.e., "water-soluble resin"). The measurement conditions in this case can be, for example, SetZero: 30 seconds, Number of measurements: 10 times, Measurement time: 120 seconds, Shape: Spherical, Refractive index: 1.5, Density: 1.0. As a particle size distribution analyzer, a dynamic light scattering particle size analyzer (for example, product name "UPA-EX150," manufactured by Nikkiso) can be used. Of course, the particle size distribution analyzer and measurement conditions used are not limited to those mentioned above.

[0059] [Content] Content of first resin particles in first ink C R1 The (mass%) is preferably 2.5% to 17.0% by mass, and more preferably 2.5% to 14.0% by mass, based on the total mass of the ink. Also, the content of the first resin particles in the first ink is V. R1 The (volume %) is preferably 2.5 volume% to 17.0 volume%, and more preferably 2.5 volume% to 14.0 volume%, based on the total ink volume.

[0060] The content of the first resin particles in the first ink is V R1 (Volume %) represents the inorganic particle content V IThe volume ratio to (volume %) is preferably 0.3 times or more and 5.0 times or less, and more preferably 0.4 times or more and 4.5 times or less. If the above volume ratio exceeds 5.0 times, the amount of inorganic particles becomes relatively small, and the voids caused by the inorganic particles also decrease, so the amount of water absorbed W1 of the first image decreases, and the second ink may be repelled by the first image, making it difficult to sufficiently suppress image unevenness. Also, when voids are created by heating, the refractive index of the binder decreases, which reduces the opacity of the first image, so the color development of the color image recorded by applying the second ink on a white image recorded with the first ink may not be sufficient. On the other hand, if the above volume ratio is less than 0.3 times, deterioration such as cracks is likely to occur after the drying process and the application process of the second ink, and the color development of the non-white image on a white background may not be sufficient.

[0061] [Glass transition temperature / melting point] Drying temperature T in the drying process H If (°C) is set to be equal to or higher than the glass transition temperature Tg(°C) or melting point Tm(°C) of the first resin particles, the first resin particles can be melted. When the first resin particles melt, the resin generated by the melting of the first resin particles permeates into the voids originating from the inorganic particles, creating voids roughly corresponding to the size of the first resin particles. Furthermore, the resin permeates into the voids originating from the inorganic particles, causing the inorganic particles to bond together. These factors work together to increase the intensity of the image, making it less susceptible to deterioration such as cracking even after drying and the application of the second ink, and further improving the color development of non-white images on a white background.

[0062] Before performing the drying process, it is preferable that the first resin particles maintain their particle shape and are not melted. If the first resin particles are melted before the drying process, the mixing of the inorganic particles and the first resin particles will not proceed promptly, or the first resin particles will be prone to fusion, and the inorganic particles and the first resin particles will be unevenly distributed. Therefore, the first image may not be able to uniformly absorb the second ink, and image unevenness may not be sufficiently suppressed. Since the first resin particles maintain their particle shape and are not melted before the drying process, it is preferable that the first resin particles have the property of not substantially fusing at room temperature (25°C). Specifically, (i) the glass transition temperature Tg R (°C) of the first resin particles is 25°C or higher, or (ii) the resin forming the first resin particles is a crystalline resin and the melting point Tm R (°C) of the first resin particles is 25°C or higher. Satisfying (ii) may be described as "the melting point Tm R (°C) of the first resin particles is 25°C or higher".

[0063] Both the glass transition temperature Tg (°C) and the melting point Tm (°C) of the first resin particles are preferably 100°C or lower, and more preferably 80°C or lower. The glass transition temperature Tg (°C) and the melting point Tm (°C) of the first resin particles can be measured by a differential scanning calorimeter (DSC).

[0064] Whether the resin forming the first resin particles is an amorphous resin or a crystalline resin can be determined by measuring the crystallinity of the resin using a differential scanning calorimeter. A resin for which no melting peak is observed by the differential scanning calorimeter is determined to be an amorphous resin. Also, a resin for which a melting peak is observed is determined to be a crystalline resin. In the case of a crystalline resin, the heat of fusion can be obtained from the peak area, and the crystallinity can also be obtained from the ratio of the heat of fusion of the completely crystalline substance with a crystallinity of 100% obtained from theoretical calculations.

[0065] Whether the first resin particles have melted during the drying process can be easily determined, for example, by cutting a recording medium on which images before and after the drying process have been recorded and observing it with a scanning electron microscope. Alternatively, by measuring the particle size of the first resin particles in the image before the drying process, if the difference between the size of the voids in the image after the drying process and the particle size of the first resin particles is small (for example, within 10%), it can be determined that the first resin particles have melted and voids have formed. More simply, if spherical first resin particles disappear from the image after the drying process and voids approximately the same size as the first resin particles or where particles are connected are observed, it can be determined that the first resin particles have melted and voids have formed.

[0066] In the drying process, the following methods can be used to confirm that the first resin particles have melted and voids have formed due to the drying of the first image. First, the recording medium on which the image is recorded is cut, and an image of the cut surface is taken using a scanning electron microscope. Then, the captured image is binarized, and the ratio of the area of ​​the black portion corresponding to the voids to the entire image is calculated. If the area ratio of voids in the image obtained by this method is 5% or more, it can be determined that the first resin particles have melted and voids have formed due to the drying of the first image. From the viewpoint of scattering efficiency, the area ratio is preferably 10% or more, more preferably 20% or more, and preferably 60% or less.

[0067] [Cumulative 50% particle size based on volume] Vacancies are formed when the first resin particles melt and the melted resin penetrates the voids formed by multiple particles. The size of the vacancies formed greatly affects light scattering. The higher the scattering efficiency, the better the color rendering of non-white images on a white background. Therefore, from the viewpoint of further increasing the light scattering efficiency, the cumulative 50% particle diameter D50 of the first resin particles is set. R1 The (nm) wavelength is preferably between 80 nm and 400 nm, and more preferably between 150 nm and 250 nm.

[0068] 〔density〕 The density ρ of the first resin particles R (g / cm 3 ) is preferably 1.00 g / cm 3 or more and 2.00 g / cm 3 or less, more preferably 1.00 or more and 1.50 g / cm 3 or less.

[0069] 〔Refractive index〕 From the viewpoint of forming a high refractive index binder, it is preferable to use first resin particles having a refractive index that is relatively high. The refractive index of the first resin particles is preferably 1.5 or more, more preferably 1.6 or more, and preferably 2.5 or less.

[0070] 〔Acid value, weight average molecular weight〕 The acid value of the resin constituting the first 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 first 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 first resin particles do not necessarily need to encapsulate a colorant.

[0071] 〔Preferred materials〕 Examples of the resin for forming the first resin particles include acrylic resins, polyester resins, urethane resins, vinyl chloride resins, and styrene resins. Among them, from the viewpoint of inkjet characteristics, acrylic resins, polyester resins, and urethane resins are preferred. When using first resin particles formed of resins other than those described above, ejection may easily become unstable, and as a result, image unevenness may not be sufficiently suppressed. Among them, acrylic resins are preferred, and acrylic resins having units derived from styrene are more preferred. The acrylic resin may be a homopolymer formed of only one type of monomer unit or a copolymer formed of a plurality of types of monomer units. The resin for forming the first resin particles can be appropriately selected and used from the same resins as the resin composition for the "other resins" described later.

[0072] [Other resins] The first ink may further contain a resin other than the first resin particles described above (other resins). The content (mass%) of the resin (other resins) 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.

[0073] Other resins can be added to the ink to stabilize the dispersion of pigments, i.e., as resin dispersants or their auxiliary agents. They can also be added to the ink to improve various properties of the recorded image. Examples of resin forms include block copolymers, random copolymers, graft copolymers, and combinations thereof. The other resins may be either water-soluble resins or resin particles, but water-soluble resins are preferred.

[0074] [Composition of the resin] Examples of resins include acrylic resins, urethane resins, polyester resins, and olefin resins. Among these, acrylic resins and urethane resins are preferred, and acrylic resins composed of units derived from (meth)acrylic acid or (meth)acrylate are even more preferred.

[0075] As for acrylic resins, those having hydrophilic units and hydrophobic units as constituent units are preferred. In particular, resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one selected from the group consisting of monomers having aromatic rings and (meth)acrylic acid ester monomers are preferred. Especially preferred are resins having hydrophilic units derived from (meth)acrylic acid and hydrophobic units derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene. Because these resins readily interact with pigments, they can be suitably used as resin dispersants for dispersing pigments.

[0076] Hydrophilic units are units that have hydrophilic groups, such as anionic groups. Hydrophilic units can be formed, for example, by polymerizing hydrophilic monomers that have hydrophilic groups. Specific examples of hydrophilic monomers that have hydrophilic groups include acidic monomers having carboxylic acid groups, such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Cations that constitute salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. Hydrophobic units are units that do not have hydrophilic groups, such as anionic groups. Hydrophobic units can be formed, for example, by polymerizing hydrophobic monomers that do not have hydrophilic groups, such as anionic groups. Specific examples of hydrophobic monomers include monomers having aromatic rings, 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.

[0077] Urethane resins can be obtained, for example, by reacting polyisocyanate with a polyol. Alternatively, they may be obtained by further reacting a chain extender. Examples of olefin resins include polyethylene and polypropylene.

[0078] Polyester resins are typically composed of units derived from polyhydric alcohols and units derived from polyhydric carboxylic acids. Examples of polyhydric alcohols that become units constituting polyester resins through reaction include dihydric to tetrahydric polyhydric alcohols. Examples of polyhydric alcohols include polyhydric alcohols having aliphatic groups, polyhydric alcohols having aromatic groups, and sugar alcohols.

[0079] Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol (1,2-ethanediol), neopentyl glycol (2,2-dimethyl-1,3-propanediol), 1,3-propanediol, 1,4-butanediol, benzenediol, and 2,2-bis(4-hydroxyphenyl)propane (bisphenol A); trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric alcohols such as pentaerythritol. Oligomers (low-molecular-weight polymers with a molecular weight of 1,000 or less) can also be used as polyhydric alcohols. It is preferable to use dihydric or trihydric polyhydric alcohols because it facilitates the adjustment of the weight-average molecular weight of the polyester resin.

[0080] Polycarboxylic acids that form units derived from polycarboxylic acids that constitute polyester resins through reactions include divalent to tetravalent polycarboxylic acids. Examples of polycarboxylic acid structures include polycarboxylic acids having aliphatic groups, polycarboxylic acids having aromatic groups, and nitrogen-containing polycarboxylic acids. Examples of polycarboxylic acids include divalent carboxylic acids such as glutaric acid, adipic acid, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; trivalent carboxylic acids such as trimellitic acid; and tetravalent carboxylic acids such as ethylenediaminetetraacetic acid. Oligomers (low molecular weight polymers with a molecular weight of 1,000 or less) can also be used as polycarboxylic acids. It is preferable to use divalent or trivalent polycarboxylic acids because it is easy to adjust the weight-average molecular weight and acid value of the polyester resin.

[0081] [Physical properties of other resins] The acid value of the water-soluble resin is preferably 100 mg KOH / g or more and 250 mg KOH / g or less. The weight-average molecular weight of the water-soluble resin is preferably 3,000 or more and 15,000 or less. Furthermore, the acid value of the resin constituting the resin particles is preferably 5 mg KOH / g or more and 100 mg KOH / g or less. The weight-average molecular weight of the resin constituting the resin particles is preferably 100,000 or more and 3,000,000 or less. The resin particles do not need to contain a colorant.

[0082] [Aqueous medium] The first ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain an aqueous medium which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass%) in the first 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 water-soluble organic solvent content (mass%) in the first ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used.

[0083] As for water-soluble organic solvents, those with a boiling point of 250°C or lower are preferred, and those with a boiling point of 230°C or lower are more preferred. Water-soluble organic solvents with a boiling point of 250°C or lower tend to evaporate quickly during the drying process. On the other hand, water-soluble organic solvents with a boiling point exceeding 250°C tend to remain in the first image, and the drying process may require a longer time to reduce the amount of water absorbed W1 in the first image.

[0084] [Other ingredients] The first ink may further contain water-soluble organic compounds that are solid at 25°C, such as urea and its derivatives, trimethylolpropane, and trimethylolethane. The content (by mass) of water-soluble organic compounds that are solid at 25°C in the first ink is preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the ink. In addition to the above components, the first ink may also contain various other components as needed. Examples of other components include various additives such as wax particles, surfactants, defoamers, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, mold inhibitors, antioxidants, and reduction inhibitors. However, it is preferable that the first ink does not contain the reagents used in the reaction solution.

[0085] [Ink properties] The first ink is an aqueous ink for use in an inkjet system. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. 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 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0086] [Water absorption amount W1 in the first image] The first image, formed by drying at least a portion of the liquid component of the first ink applied to the recording medium, has a water absorption amount W1 (mL / m²) before the second ink is applied. 2 ) 1.0 mL / m² 2 It is necessary to increase this further. The water absorption amount W1 of the first image at the time the second ink is applied should be 1.0 mL / m². 2 If the amount is less than 2.0 mL / m², the liquid component of the second ink cannot be absorbed, causing the pigment to migrate and resulting in unevenness in the image. The water absorption amount W1 at the time the second ink is applied is 2.0 mL / m². 2 Preferably, the concentration is 30.0 mL / m² or higher, and also 30.0 mL / m². 2The following is preferable: The amount of water absorbed W1 in the first image at the time the second ink is applied is 1.0 mL / m². 2 The methods described above can be broadly divided into two categories. If the amount of first ink applied is constant, the volume of voids derived from inorganic particles should be increased. If the composition of the first ink is constant, the amount of first ink applied should be increased. When the volume of voids derived from inorganic particles is increased, the intensity of the first image decreases, and deterioration such as cracks is likely to occur after the drying process and the application of the second ink, and the color development of non-white images on a white background may not be sufficiently obtained. Also, when the amount of first ink applied is increased, the liquid component of the first ink becomes difficult to dry, so the drying process may need to be extended in order to reduce the amount of water absorbed W1 of the first image.

[0087] In the Bristow method for the first image, 30 msec from the start of contact 1 / 2 Water absorption capacity up to W1 (mL / m³) 2 The amount of water absorbed by the recording medium can be measured by the Bristow method, similar to the amount of water absorbed by the recording medium. The amount of water absorbed by the first image at the time the second ink is applied is preferably determined by applying the first ink to the recording medium, changing the drying process conditions, and measuring the amount of water absorbed by the first ink, and understanding the value and the trend of change. Then, it is preferable to determine the timing of applying the second ink when operating the recording device to record the image.

[0088] [Amount of first ink applied] Amount of first ink applied A1 (mL / m²) 2 ) can be set appropriately according to the image data, but 1 mL / m 2 More than 50mL / m 2 Preferably, it is 10 mL / m² 2 More than 45mL / m 2 It is even more preferable that the amount of first ink applied A1 (mL / m²) is as follows. 2 ) is the amount of second ink applied A2 (mL / m²) 2 It is preferable that it be larger than ).

[0089] (Second ink) The second ink used in the recording method of the present invention is a water-based ink containing a pigment and of a different color from the first ink, which is a white ink. The second ink may be any color other than white, and can be various colors such as black, cyan, magenta, yellow, or special colors (e.g., red, green, blue). The components that make up the ink will be described in detail below.

[0090] [Pigments] The second ink contains a pigment as a coloring agent. If the coloring agent is a dye, the ink in which the dye is dissolved will penetrate into the voids formed by multiple inorganic particles in the first image, resulting in unevenness in the image. By using a pigment as the coloring agent, the penetration of the coloring agent into the first image is effectively suppressed, allowing the pigment to be present on the first image. The pigment content (mass%) in the second ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the second ink.

[0091] Specific examples of pigments include inorganic particles such as carbon black and metal oxides; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, and dioxazine.

[0092] As for the dispersion method of the pigment, resin-dispersed pigments using a resin as a dispersant, and self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles can be used. In addition, resin-bonded pigments in which organic groups containing resin are chemically bonded to the surface of the pigment particles, and microcapsule pigments in which the surface of the pigment particles is coated with resin or the like can be used. It is also possible to use a combination of pigments with different dispersion methods from among these. In particular, it is preferable to use self-dispersing pigments in which hydrophilic groups are bonded to the surface of the pigment particles, or resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the surface of the pigment particles.

[0093] As a resin dispersant for dispersing pigments in an aqueous medium, it is preferable to use one that can disperse pigments in the aqueous medium through the action of anionic groups. As the resin dispersant, a resin having anionic groups can be used, and it is preferable to use a resin such as those described later, and among them, a water-soluble resin. The pigment content (mass%) in the second ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the resin dispersant content (mass%).

[0094] Self-dispersing pigments can be those in which anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are bonded directly to the particle surface of the pigment or via other atomic groups (-R-). The anionic group may be either acidic or salt-type, and if it is salt-type, it may be in a partially dissociated state or a fully dissociated state. When the anionic group is salt-type, examples of cations that become counterions include alkali metal cations, ammonium, and organic ammonium. Specific examples of other atomic groups (-R-) include linear or branched alkylene groups with 1 to 12 carbon atoms; arylene groups such as phenylene and naphthylene groups; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Combinations of these groups may also be used.

[0095] Pigment volume-based cumulative 50% particle size D50 P The (nm) is preferably between 20 nm and 300 nm, and more preferably between 60 nm and 200 nm. D50 is the cumulative 50% particle size based on the volume of the pigment. P If the particle size is less than 20 nm, the pigment of the second ink may be incorporated into voids caused by inorganic particles in the first image recorded with the first ink, resulting in insufficient color development of non-white images on a white background. Conversely, if the particle size is greater than 300 nm, the pigment particles may be too large, resulting in low color development efficiency and insufficient color development of non-white images on a white background. (D50: Cumulative 50% particle size based on pigment volume) PThis can be measured using a particle size analyzer that employs dynamic light scattering (for example, product name "UPA-EX150," manufactured by Nikkiso). Of course, the particle size distribution analyzer and measurement conditions used are not limited to those mentioned above.

[0096] [resin] The second ink can contain a resin. By using an ink containing a resin, it is possible to record images with improved scratch resistance. The resin can be added to the ink to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. It can also be added to the ink to improve various properties of the recorded image. Examples of resin forms include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be either a water-soluble resin or resin particles.

[0097] The resin content (mass%) 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 second ink.

[0098] The second ink preferably contains resin particles (second resin particles). An ink containing second resin particles allows for a higher resin content while suppressing an increase in ink viscosity, thus reducing the liquid component content in the second ink. This allows for a rapid increase in the viscosity of the second ink when applied to the first image, more effectively suppressing image unevenness and further improving the color reproduction of non-white images on a white background.

[0099] The resin used to form the second resin particles can be appropriately selected from those with the same composition as the "other resins" used in the first ink described above. Among these, acrylic resins and urethane resins are preferred.

[0100] [Aqueous medium] The second ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain an aqueous medium which is water or a mixed solvent of water and a water-soluble organic solvent. Deionized water or ion-exchanged water is preferably used as the water. The water content (mass%) in the 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 water-soluble organic solvent content (mass%) in the second ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used.

[0101] As for water-soluble organic solvents, those with a boiling point of 250°C or lower are preferred, and those with a boiling point of 230°C or lower are more preferred. Water-soluble organic solvents with a boiling point of 250°C or lower tend to evaporate quickly during the drying process. Water-soluble organic solvents with a boiling point exceeding 250°C tend to remain in the image, inhibiting light scattering and reducing the opacity, which may result in insufficient color development of non-white images on a white background.

[0102] [Other ingredients] The second ink may further contain water-soluble organic compounds that are solid at 25°C, such as urea and its derivatives, trimethylolpropane, and trimethylolethane. The content (by mass) of water-soluble organic compounds that are solid at 25°C in the second ink is preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the ink. In addition to the above components, the second ink may also contain various other components as needed. Examples of other components include various additives such as wax particles, surfactants, defoamers, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, mold inhibitors, antioxidants, and reduction inhibitors. However, it is preferable that the second ink does not contain the reagents used in the reaction solution.

[0103] [Ink properties] The second ink is an aqueous ink for use in an inkjet system. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. 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 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0104] [Amount of second ink applied] Amount of second ink applied A2 (mL / m²) 2 ) is the amount of water absorbed in the first image W1 (mL / m³). 2 The ratio to ) is preferably 20.0 times or less, and more preferably 15.0 times or less. If the ratio exceeds 20.0 times, the first image may not be able to sufficiently absorb the liquid component of the second ink, the pigment of the second ink may easily move on the first image, and unevenness may occur in the image. Amount of second ink applied A2 (mL / m²) 2 ) is the amount of water absorbed in the first image W1 (mL / m³). 2 The ratio to the second ink is preferably 0.1 times or more, and more preferably 1.0 times or more. Amount of second ink A2 (mL / m²) 2 ) can be set appropriately according to the image data, but 1 mL / m 2 More than 50mL / m 2 Preferably, it is 1 mL / m² 2 More than 20mL / m 2 The following is even more preferable:

[0105] (Reaction solution) The recording method of the present invention preferably includes a first reaction solution application step of applying an aqueous reaction solution containing a reactant that reacts with a first ink to a recording medium, or a second reaction solution application step of applying an aqueous reaction solution containing a reactant that reacts with a second ink to a recording medium. In particular, it is preferable to have the reaction solution application step before the ink application step, or to perform the ink application step and the reaction solution application step in parallel. Furthermore, it is especially preferable to have both the first reaction solution application step and the second reaction solution application step. In this specification, a reaction solution used with the first ink may be referred to as the first reaction solution, and a reaction solution used with the second ink may be referred to as the second reaction solution, but when it is common to both reaction solutions, it will simply be referred to as "reaction solution".

[0106] By applying the first reaction solution in a manner that overlaps with the area to which the first ink is applied, the inorganic particles and first resin particles of the first ink aggregate. When the inorganic particles aggregate, the pore volume of the aggregate is increased, which further increases the water absorption amount W1 of the first image and further effectively suppresses image unevenness. Based on the reactivity of the first ink and the first reaction solution, the ratio of the application amounts can also be changed to control the water absorption amount W1 of the first image to a desired value.

[0107] Furthermore, by applying the second reaction solution in a manner that overlaps with the area to which the second ink is applied, the pigment and other components of the second ink aggregate. When the pigment aggregates, the ink becomes thicker, and solid-liquid separation occurs between the liquid components of the ink and the aggregated material. This allows the pigment of the second ink to be efficiently fixed onto the first image, further effectively suppressing image unevenness.

[0108] The first and second reaction solutions may have different compositions depending on the characteristics of the first and second inks, or they may be a common reaction solution for both inks. The components used in the reaction solutions will be described in detail below.

[0109] [Reactive agent] The reaction solution reacts with the ink upon contact, causing the components in the ink (components with anionic groups, such as resins) to aggregate, and contains a reactant. The presence of the reactant destabilizes the state of the components with anionic groups in the ink when the ink and reactant come into contact on the recording medium, thereby promoting ink aggregation. Examples of reactants include organic acids, polyvalent metal salts, and cationic resins.

[0110] Examples of polyvalent metal ions that make up polyvalent metal salts include Ca 2+ Cu 2+ Ni 2+ Mg 2+ Sr 2+ Ba 2+ , and Zn 2+ Divalent metal ions such as Fe 3+ , Cr 3+ , Y 3+ , and Al 3+ Examples of trivalent metal ions include the following. To include polyvalent metal ions in the reaction solution, a water-soluble polyvalent metal salt (which may also be a hydrate) composed of a polyvalent metal ion and an anion can be used. Examples of anions that make up a polyvalent metal salt include Cl - , Br - , I - , - 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 - C2H5COO - CH3CH(OH)COO - , C2H4(COO -)2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - Examples of organic anions include the following. When polyvalent metal ions are used as a reactant, the content (mass%) of the polyvalent metal salt in the reaction solution is preferably 1.0% by mass or more and 40.0% by mass or less, based on the total mass of the reaction solution. In this specification, when the polyvalent metal salt is a hydrate, the "content (mass%) of the polyvalent metal salt" in the reaction solution means the "content (mass%) of the anhydrous polyvalent metal salt" excluding water as the hydrate.

[0111] The reaction solution containing an organic acid has buffering capacity in the acidic range (pH less than 7.0, preferably pH 2.0 to 5.0), which efficiently converts the anionic groups of components present in the ink into acidic forms and aggregates them. Examples of organic acids include monocarboxylic acids and their salts such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrole carboxylic acid, furanic acid, picolinic acid, nicotinic acid, thiophene carboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and their salts or hydrogen salts 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 their salts or hydrogen salts such as citric acid and trimellitic acid; and tetracarboxylic acids and their salts or hydrogen salts such as pyromellitic acid. When using an organic acid as a reactant, the content (by mass) of the organic acid in the reaction solution is preferably 1.0% by mass or more and 50.0% by mass or less, based on the total mass of the reaction solution.

[0112] Examples of cationic resins include resins having the structure of primary to tertiary amines and resins having the structure of quaternary ammonium salts. Specifically, examples include resins having the structures of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. To improve solubility in the reaction solution, cationic resins can be used in combination with acidic compounds, or cationic resins can be subjected to quaternization treatment. When a cationic resin is used as a reactant, the content (mass%) of the cationic resin in the reaction solution is preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the reaction solution.

[0113] [Aqueous medium] The reaction solution is an aqueous reaction solution containing at least water as an aqueous medium. The aqueous medium used in the reaction solution may contain the aforementioned water-soluble organic solvent that can be incorporated into the ink. In particular, the water-soluble organic solvent used in the first reaction solution is preferably one with a boiling point of 250°C or lower, and more preferably one with a boiling point of 230°C or lower. Water-soluble organic solvents with a boiling point of 250°C or lower evaporate quickly during the drying process, further improving the color development of non-white images on a white background. Water-soluble organic solvents with a boiling point exceeding 250°C tend to remain in the first image, so the drying process may take longer in order to reduce the amount of water absorbed W1 in the first image.

[0114] [Other ingredients] The reaction solution may contain various other components as needed. Examples of other components include those similar to those mentioned above that can be included in the ink.

[0115] [Physical properties of the reaction solution] The reaction solution is an aqueous solution applied to an inkjet system. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the reaction solution at 25°C is preferably 20 mN / m or more and 60 mN / m or less. 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, and more preferably 6.0 or more and 9.0 or less. [Examples]

[0116] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0117] <Measurement of physical properties> (density) The densities of inorganic particles and resin particles were measured using the Gay-Lussac type pycnometer method in accordance with JIS Z 8807.

[0118] (Total pore volume) A water dispersion of particles was dried at 60°C to obtain a powder. Approximately 0.10 g of the obtained particles was placed in a 3 / 8-inch inner diameter cell and set in a sample pretreatment device (product name "VacPrep 061", manufactured by Micromerities). The particles were dried by degassing while heating at 60°C until the torr was less than 20 ml, thereby obtaining a sample. The pore volume distribution of the obtained sample was measured using a Micromerities automatic specific surface area / pore distribution analyzer (product name "TriStar II", manufactured by Shimadzu Corporation) by nitrogen adsorption desorption method. From the measured pore volume distribution, the value of the nitrogen desorption side was taken as the total pore volume.

[0119] (Cumulative 50% particle size based on volume) Using a particle size analyzer based on dynamic light scattering (product name "UPA-EX150", manufactured by Nikkiso), the cumulative 50% particle size (D50) based on volume of inorganic and resin particles was determined. P and D50 R We measured it.

[0120] (Glass transition temperature, melting point) The glass transition temperature Tg and melting point Tm of resin particles were measured using a differential scanning calorimeter (DSC). A sample for measurement was prepared by drying an aqueous dispersion of resin particles at 60°C, placing 2 mg of the resin particles in an aluminum container, and sealing it. Thermal analysis was performed on the prepared sample using a differential scanning calorimeter (product name "DSC-2500", manufactured by TA instruments) according to the temperature program shown below. In this specification, the glass transition temperature of resin particles is defined as follows: That is, the temperature at the intersection of a straight line extended from two points on the low-temperature side of the heating curve (horizontal axis: temperature, vertical axis: heat) in the following temperature program (4) or (5) to the high-temperature side, and a tangent line drawn at the point where the slope of the step-like change portion of the curve is maximum, is determined. The temperature obtained in this way was defined as the "glass transition temperature of the resin particles". Furthermore, the melting point of the resin particles was measured using the same method as in (1) to (4) below, except that the upper temperature limit in (4) was changed. The peak top of the endothermic peak in the heating curve was defined as the "melting point Tm of the particles".

[0121] [Temperature Program] (1) Heat from -40°C to 200°C at a rate of 10°C / min. (2) Hold at 200°C for 5 minutes (3) Cooling from 200°C to -40°C at a rate of 10°C / min (4) Heat from -40°C to 200°C at a rate of 10°C / min. (5) Heat from -40°C to 150°C at a rate of 10°C / min

[0122] <Preparation of inorganic particles> The following inorganic particles were prepared. A mixing and stirring machine (product name "TK Robomix", manufactured by Primix) was used as the disperser. The characteristics of the inorganic particles are shown in Table 1.

[0123] (Inorganic particles 1) 200.5 parts of deionized water, 4.5 parts of 2,2',2"-nitrilotriethanol, and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above-mentioned disperser, the mixture was pre-dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 150.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above-mentioned disperser and dispersed at 2,700 rpm for 5 hours. After that, an appropriate amount of deionized water was added to obtain an aqueous dispersion of inorganic particles 1 with a particle content of 30.0%.

[0124] (Inorganic particles 2) 224.3 parts of deionized water, 12.7 parts of an aqueous solution of acrylic resin (product name "BYK-154", manufactured by Big Chemie, resin content 42.0%), and 63.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above disperser, the mixture was pre-dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 150.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above disperser and dispersed at 2,000 rpm for 5 hours. After that, an appropriate amount of deionized water was added to obtain an aqueous dispersion of inorganic particles 2 with a particle content of 20.0%.

[0125] (Inorganic particles 3) 222.7 parts of deionized water, 1.2 parts of acetic acid, 13.1 parts of an aqueous solution of acrylic resin (product name "Aron A-210", manufactured by Toagosei, resin content 43.0%), and 63.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above disperser, the mixture was dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 150.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above disperser and dispersed at 1,360 rpm for 1 hour. After that, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 3 with a particle content of 20.0%.

[0126] (Inorganic particles 4) 185.0 parts of deionized water, 20.0 parts of an aqueous solution of acrylic resin (product name "BYK-190", manufactured by Big Chemie, resin content 40.0%), and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. The mixture was dispersed at 750 rpm for 30 minutes using the above-mentioned disperser. Then, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 4 with a particle content of 30.0%.

[0127] (Inorganic particles 5) 200.5 parts of deionized water, 4.5 parts of 2,2',2"-nitrilotriethanol, and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above-mentioned disperser, the mixture was dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 150.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above-mentioned disperser and dispersed at a rotation speed of 2,700 rpm for 5 hours. After that, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 5 with a particle content of 30.0%.

[0128] (Inorganic particles 6) 200.5 parts of deionized water, 4.5 parts of 2,2',2"-nitrilotriethanol, and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above-mentioned disperser, the mixture was dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 150.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above-mentioned disperser and dispersed at a rotation speed of 1,350 rpm for 5 hours. After that, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 6 with a particle content of 30.0%.

[0129] (Inorganic particles 7) 200.5 parts of deionized water, 4.5 parts of 2,2',2"-nitrilotriethanol, and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. Using the above-mentioned disperser, the mixture was dispersed at 750 rpm for 30 minutes to obtain a pre-dispersion. Next, 150.0 mL of the pre-dispersion obtained above and 225.0 mL (bulk volume) of 0.05 mm diameter beads were placed in the above-mentioned disperser and dispersed at a rotation speed of 2,700 rpm for 5 hours. After that, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 7 with a particle content of 30.0%.

[0130] (Inorganic particles 8) 200.5 parts of deionized water, 4.5 parts of 2,2',2"-nitrilotriethanol, and 95.0 parts of inorganic particles of the type shown in Table 1 were mixed. The mixture was dispersed at 750 rpm for 30 minutes using the above-mentioned disperser. Then, an appropriate amount of deionized water was added to obtain a dispersion of inorganic particles 8 with a particle content of 30.0%.

[0131] [Table 1]

[0132] <Preparation of resin particles> The following resin particles were prepared. The properties of the resin particles are shown in Table 2.

[0133] (Resin particles 1-3, 6-9) A solution was prepared by mixing 0.2 parts potassium persulfate and 74.0 parts deionized water. An emulsion was also prepared by mixing the monomers (in parts) shown in Table 1 and 0.3 parts of a reactive surfactant. The abbreviations for the monomers are: St: styrene, 2EHA: 2-ethylhexyl acrylate, MMA: methyl methacrylate, AA: acrylic acid. A nonionic surfactant (product name "Adekaria Soap ER-20", manufactured by ADEKA, number of ethylene oxide units: 20) was used as the reactive surfactant. Under a nitrogen atmosphere, the emulsion was added dropwise to the solution over 1 hour, polymerized at 80°C with stirring for 3 hours, and then stirred for a further 2 hours. After cooling to 25°C, deionized water and potassium hydroxide aqueous solution were added to adjust the pH to 8.0, and then an appropriate amount of deionized water was added to adjust the solid content to obtain aqueous dispersions of each resin particle.

[0134] (Resin particles 4) For the aqueous dispersion of resin particles 4, an aqueous dispersion of polyurethane resin particles (product name "Superflex 300", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

[0135] (5 resin particles) A mixture of 498 parts terephthalic acid, 498 parts isophthalic acid, 876 parts adipic acid, and 2,280 parts bisphenol A was placed in a reaction vessel set up in an autoclave, and the mixture was heated at 250°C and 13 kPa for 6 hours to carry out the esterification reaction. Next, 0.8 parts antimony trioxide and 0.15 parts phosphoric acid were added as catalysts, and the temperature was raised to 270°C. After that, the pressure in the reaction vessel was gradually reduced to 13 Pa over 1.5 hours. The polycondensation reaction was continued for 4 hours while maintaining the reduced pressure of 270°C and 13 Pa, and then nitrogen gas was introduced into the reaction vessel to return to atmospheric pressure. After lowering the temperature to 265°C, 15 parts trimellitic acid was added, and the polymerization reaction was carried out by heating at 265°C for 2 hours to obtain polyester resin 1.

[0136] A stirrer (product name "Tornado Standard SM-101 (manufactured by AS ONE)") was set up in a 2L beaker. 150 parts of the polyester resin 1 obtained above and 350 parts of tetrahydrofuran were added to this beaker, and the mixture was stirred at 25°C to dissolve the resin. Next, a 5% sodium hydroxide aqueous solution was added to achieve a 100% neutralization rate of the acid groups of the resin, and the mixture was stirred for 30 minutes to obtain a slurry. 700 parts of deionized water were added dropwise to the beaker at a rate of 20 mL / min while stirring at 25°C and 150 rpm. After raising the temperature to 60°C, the tetrahydrofuran was removed under reduced pressure, and some of the water was further removed. Next, the beaker was placed in an 85°C water bath, and the contents were stirred for 2 hours to perform heat treatment. After filtering the contents through a 150-mesh wire mesh, an appropriate amount of deionized water was added to obtain an aqueous dispersion of resin particles 5 with a resin content of 30.0%.

[0137] [Table 2]

[0138] <Preparation of Pigment Dispersion> A pigment dispersion was prepared using the following procedure. The pigment and resin content in the obtained pigment dispersion, and the cumulative 50% particle size D50 based on the volume of the pigment were determined. P This is shown in Table 3.

[0139] (Pigment dispersion 1) To a solution prepared by dissolving 5 parts concentrated hydrochloric acid in 5.5 parts water, 1.5 parts of 4-amino-1,2-benzenedicarboxylic acid was added while the solution was cooled to 5°C. Next, the container of this solution was placed in an ice bath to keep the solution below 10°C, and a solution prepared by dissolving 1.8 parts sodium nitrite in 9 parts 5°C water was added. After stirring this solution for another 15 minutes, 6.0 parts of carbon black (product name "NIPex160IQ", manufactured by Orion Engineered Carbons) with a DBP oil absorption of 128 mL / 100 g was added under stirring. After stirring for another 15 minutes, the resulting slurry was filtered through filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec), and the particles were thoroughly washed with water. The particles were dried in an oven at 110°C to prepare a self-dispersing pigment. Furthermore, an appropriate amount of deionized water was added to the obtained self-dispersing pigment to disperse it so that the pigment content was 10.0%, and a dispersion was prepared. Subsequently, the counterions of the anionic groups were replaced from sodium ions to potassium ions using an ion exchange method to obtain pigment dispersion 1.

[0140] (Pigment dispersion 2) An acrylic resin (product name "Joncryl 683", manufactured by BASF) was dissolved in deionized water with sodium hydroxide equimolar to the acid value to prepare an aqueous solution of resin dispersant with a resin content of 20.0%. A mixture of 10.0 parts pigment, 25.0 parts of the aqueous solution of resin dispersant, and 65.0 parts water was placed in a sand grinder and dispersed for 1 hour. As the pigment, carbon black (product name "NIPex160IQ", manufactured by Orion Engineered Carbons) with a DBP oil absorption of 128 mL / 100 g was used. Subsequently, the mixture was centrifuged and pressure filtered through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm, and an appropriate amount of deionized water was added to obtain pigment dispersion 2. The resin content in pigment dispersion 2 was 5.0%.

[0141] (Pigment dispersion 3) 7.0 parts of pigment (CI pigment blue 15:3), 14.0 mmol of monosodium salt of ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid, 40.0 mmol of nitric acid, and 200.0 parts of pure water were mixed. Next, the mixture was mixed using a Silverson mixer at 25°C and 6,000 rpm. After 30 minutes, 40.0 mmol of sodium nitrite dissolved in a small amount of deionized water was slowly added to the mixture. The temperature of the mixture reached 60°C upon addition of sodium nitrite, and the mixture was reacted at this temperature for 1 hour. Then, an aqueous sodium hydroxide solution was added to adjust the pH of the mixture to 10. 20.0 parts of deionized water were added, and diafiltration was performed using a spectrum membrane. Next, an appropriate amount of deionized water was added to obtain pigment dispersion 3.

[0142] (Pigment dispersion 4) 7.0 parts of pigment (CI Pigment Red 122), 14.0 mmol of monosodium salt of ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid, 40.0 mmol of nitric acid, and 200.0 parts of deionized water were mixed. Next, the mixture was mixed using a Silverson mixer at 25°C and 6,000 rpm. After 30 minutes, 40.0 mmol of sodium nitrite dissolved in a small amount of deionized water was slowly added to the mixture. The temperature of the mixture reached 60°C upon addition of sodium nitrite, and the mixture was reacted at this temperature for 1 hour. Then, an aqueous sodium hydroxide solution was added to adjust the pH of the mixture to 10. 20.0 parts of deionized water were added, and diafiltration was performed using a spectrum membrane. Next, an appropriate amount of deionized water was added to obtain pigment dispersion 4.

[0143] (Pigment dispersions 5 and 6) The pigment type was changed to carbon black (product name "BLACK PEARLS880", manufactured by Cabot) with a DBP oil absorption capacity of 105 mL / 100 g. Additionally, by changing the stirring conditions, the cumulative 50% particle size D50 of the pigment was increased based on volume. P The following was adjusted. Aside from these steps, pigment dispersions 5 and 6 were obtained using the same procedure as for pigment dispersion 1.

[0144] (Pigment dispersion 7) The pigment type was changed to carbon black (product name "MONARCH700", manufactured by Cabot) with a DBP oil absorption capacity of 122 mL / 100 g. Additionally, by changing the stirring conditions, the cumulative 50% particle size D50 of the pigment was increased based on volume. P The following was adjusted. Aside from these steps, pigment dispersion 7 was obtained using the same procedure as for pigment dispersion 1.

[0145] (Pigment dispersion 8) The pigment type was changed to carbon black (product name "TOKABLACK#5500", manufactured by Tokai Carbon) with a DBP oil absorption capacity of 155 mL / 100 g. Additionally, by changing the stirring conditions, the cumulative 50% particle size D50 of the pigment was increased based on volume. P The following was adjusted. Aside from these steps, pigment dispersion 8 was obtained using the same procedure as for pigment dispersion 1.

[0146] [Table 3]

[0147] <Preparation of the first ink> The components (in %) shown in the upper section of Tables 4 and 5 were mixed, and potassium hydroxide (included in the amount of deionized water used) was added to adjust the pH of the ink to within the range of 7 to 9. Each ink was prepared by pressure filtration through a 3.0 μm pore size microfilter (manufactured by Fujifilm). In Tables 4 and 5, "Surfinol 465" is the trade name of a nonionic surfactant (acetylene glycol ethylene oxide adduct) manufactured by Nisshin Chemical Industry Co., Ltd. The characteristics of each ink are shown in the lower section of Tables 4 and 5.

[0148] [Table 4]

[0149] [Table 5]

[0150] <Preparation of the second ink> Each component shown in Table 6 (unit: %) was mixed, and potassium hydroxide (included in the amount of deionized water used) was added to adjust the pH of the ink to within the range of 8 to 9. Each ink was prepared by pressure filtration through a 3.0 μm pore size microfilter (manufactured by Fujifilm). In Table 6, "Surfinol 465" is the trade name of a nonionic surfactant (acetylene glycol ethylene oxide adduct) manufactured by Nisshin Chemical Industry Co., Ltd.

[0151] [Table 6]

[0152] <Preparation of reaction solution> (Reaction solution 1) 7.0 parts of magnesium sulfate heptahydrate, 20.0 parts of 1,2-butanediol, 0.5 parts of nonionic surfactant (product name "Surfinol 465", manufactured by Nisshin Chemical Industry Co., Ltd.), and 72.5 parts of deionized water were mixed and thoroughly stirred. Then, the mixture was pressure filtered through a 3.0 μm pore size cellulose acetate filter (manufactured by Advantec) to obtain reaction solution 1.

[0153] (Reaction solution 2) 5.0 parts magnesium sulfate heptahydrate, 37.0 parts liquid containing cationic resin, 20.0 parts 1,2-butanediol, 0.5 parts nonionic surfactant (product name "Surfinol 465", manufactured by Nisshin Chemical Industry Co., Ltd.), and 37.5 parts deionized water were mixed and thoroughly stirred. As the liquid containing cationic resin, "Unisense FPA100L" (manufactured by Senka, cationic resin content: 27.0%) was used. Subsequently, the mixture was subjected to pressure filtration through a cellulose acetate filter with a pore size of 3.0 μm (manufactured by Advantec Co., Ltd.) to obtain reaction solution 2.

[0154] <Preparing the recording medium> The following recording media were prepared. • Recording medium 1: Polyethylene terephthalate film (product name "Ultra-Transparent PET Film GIY-0305", manufactured by Lintec, 30 msec from the start of contact in the Bristow method)1 / 2 Water absorption capacity up to W m : 10.0 mL / m² 2 (Within the following range) • Recording medium 2: High-transparency polyvinyl chloride (product name "3M Scotchcal Clear Graphic Film IJ8150", manufactured by 3M, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption capacity up to W m : 10.0 mL / m² 2 (Within the following range) • Recording medium 3: Black coated paper (product name "FSPG Color B", manufactured by Daio Paper Corporation, 30 msec from the start of contact in the Bristow method) 1 / 2 Water absorption capacity up to W m : 10.0 mL / m² 2 (Within the following range) • Recording medium 4: High-quality paper (product name "Colored High-Quality Paper, Black, Thick"), manufactured by Takeo, 30 msec from the start of contact in the Bristow method 1 / 2 Water absorption capacity up to W m : 10.0 mL / m² 2 (It is super)

[0155] <Rating> The reaction solution and ink obtained above were used to evaluate the following items. In this invention, "AA," "A," and "B" were considered acceptable levels in the evaluation criteria for each item shown below, and "C" was considered an unacceptable level. The evaluation conditions and evaluation results are shown in Tables 7 and 8.

[0156] (Recording of images for evaluation) Using the reaction solutions and inks shown in Tables 7 and 8 as a set, evaluation images (solid images) were recorded under the following conditions. In this embodiment, the recording duty cycle of a solid image recorded under the condition of applying two droplets (reaction solution or ink) with a mass of 4.0 ng per drop to a unit area of ​​1 / 1,200 inch × 1 / 1,200 inch is defined as 100%. Using the recording devices shown in Tables 7 and 8, the reaction solutions and inks were applied to the recording media shown in Tables 7 and 8 in this order, overlapping each other, to record a solid image of size 50 mm × 50 mm. At this time, the amount of each reaction solution applied was 20% (by volume) of the amount of ink applied, and the amount of each ink applied was set to the values ​​shown in Tables 7 and 8. In Comparative Examples 3, 5, 7, and Reference Example 2, the second ink was applied without drying the first image by stopping the first drying unit 2100.

[0157] • Recording device 1: An inkjet recording device having the configuration shown in Figure 3 had a cartridge filled with the first reaction solution set in the first reaction solution dispenser 1102, and a cartridge filled with the first ink set in the first ink dispenser 1103. In addition, a cartridge filled with the second reaction solution set in the second reaction solution dispenser 1202, and a cartridge filled with the second ink set in the second ink dispenser 1203. A single-pass method was adopted in which the reaction solution and ink to a unit area were applied with a single relative scan between the recording head and the recording medium. In the first drying unit 2000, after the first reaction solution and the first ink were applied to the recording medium, air drying was performed so that the surface temperature of the recording medium reached the drying temperatures shown in Tables 7 and 8, and the first image was formed. Subsequently, the second reaction solution and the second ink were applied to the first image, and air drying was performed by the second drying unit 2300 so that the surface temperature of the recording medium reached 80°C, heating the surface temperature of the recording medium to this drying temperature.

[0158] • Recording device 2: An inkjet recording device having the configuration shown in Figure 4 was fitted with cartridges containing the first reaction solution, the second reaction solution, the first ink, and the second ink, respectively. A multi-pass method was used to apply the reaction solution and ink to a unit area through multiple relative scans of the recording head and the recording medium, with different scans for applying the first ink and the second ink. In the transport direction of the recording medium, a drying device provided downstream of the recording head was used to blow-dry the recording medium after the first reaction solution and the first ink had been applied to it, so that the surface temperature of the recording medium reached the drying temperatures shown in Tables 7 and 8, thereby forming the first image. Subsequently, the second reaction solution and the second ink were applied to the first image, and the recording medium was heated by heater 25 to a surface temperature of 80°C.

[0159] (Measurement of water absorption amount W1 in the first image) After applying the first reaction solution and the first ink to the recording medium under the conditions described above, the recording medium was air-dried under the conditions shown in Tables 7 and 8 to form the first image. Subsequently, the recording medium was ejected from the recording device without applying the second reaction solution and the second ink. For the first image immediately after ejection, a dynamic permeability test apparatus using the Bristow method (product name "Dynamic Permeability Tester", manufactured by Toyo Seiki Seisakusho) was used to test the Bristow method from the start of contact for 30 msec. 1 / 2 Water absorption capacity up to W1 (mL / m³) 2 ) was measured.

[0160] (Image inconsistency) If there was a release liner on the back of the recording medium, it was removed, and the recorded image was placed with the recording side facing up on a white polyethylene terephthalate film (product name "Lumirror #250-E20", manufactured by Toray). Using a scanner (product name "DR-C225II", manufactured by Canon), the image was read from the recording side, and the solid image was binarized to calculate the area percentage (%) of the parts recorded according to the input data (dark parts of the image). The reading conditions were color, 600 dpi. For the binarization process, after converting to 8-bit using the image processing software "ImageJ", the threshold value [(255 + Gtop) / 2] was set for the gradation value (Gtop) at the peak of the luminance histogram at white 255 / black 0. From the area above the threshold obtained in this way, the percentage (area ratio) was calculated, and image uniformity was evaluated according to the evaluation criteria shown below. In this example, an area ratio of 80.0% or more was judged to be "no image uniformity". AA: The area ratio was 95.0% or higher. A: The area ratio was between 90.0% and less than 95.0%. B: The area ratio was between 80.0% and less than 90.0%. C: The area ratio was less than 80.0%, resulting in unevenness in the image.

[0161] (Color development) If there was a release liner on the back of the recording medium, it was removed. With the recording side of the recorded image facing upwards, if there was a release liner on the back, it was removed, and the image was superimposed on a white polyethylene terephthalate film (product name "Lumirror #100-T60", manufactured by Toray). Using a fluorescence spectrophotometer (product name "FD-7", manufactured by Konica Minolta), the lightness (L) of the solid image in the CIELab color system was measured from the recording side. * ) and saturation (C *The following measurements were taken. The color reproduction was then evaluated according to the evaluation criteria shown below. Since the degree to which an image is perceived as darker differs depending on the hue of the ink, in this example, the evaluation criteria for color reproduction were set according to the hue of the ink. In the case of black ink, where the pigment is carbon black, a lower brightness indicates a darker image and good color reproduction. In the case of color inks, where the pigment is organic pigment (cyan ink containing CI pigment blue 15:3, magenta ink containing CI pigment red 122), a higher saturation indicates a more vivid image and good color reproduction.

[0162] [Evaluation Criteria for Black Ink] AA: Lightness L * was 9 or less A: Lightness L * It was greater than 9 and less than or equal to 10. B: Brightness L * It was greater than 10 and less than or equal to 11. C: Brightness L * The number was over 11

[0163] [Criteria for evaluating cyan ink] AA: Saturation C * The number was 65 or higher A: Saturation C * The number was between 60 and 65. B: Saturation C * The number was between 55 and 60. C: Saturation C * The number was less than 55.

[0164] [Evaluation Criteria for Magenta Ink] AA: Saturation C * The number was 75 or higher. A: Saturation C * The number was between 70 and 75. B: Saturation C * The number was between 65 and 70. C: Saturation C * The number was less than 65.

[0165] [Table 7]

[0166] [Table 8] [Explanation of Symbols]

[0167] 1 Inorganic particles 2 First resin particle 3. Binder (a mixture of resin and inorganic particles) 4. Holes

Claims

1. The first and second water-based inks are ejected from an inkjet recording head, and in the Bristow method, from the start of contact, 30 msec １／２ Water absorption capacity up to W ｍ (mL / m) ２ ) is 10.0 mL / m² ２ An inkjet recording method for recording an image on the following recording medium, A first ink application step of applying the first ink to the recording medium, A drying step to form a first image by drying at least a portion of the liquid component of the first ink applied to the recording medium, and The process includes a second ink application step of applying the second ink so as to overlap at least a portion of the first image to record the image, The first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume (cm³) of the inorganic particles is measured by nitrogen adsorption desorption. ３ ( / g) is 0.03 cm ３ / g or more, The second ink contains a pigment and is a different color from the first ink. The second ink application step is performed after the drying step such that the water absorption amount W １／２ from the start of contact to 30 msec １ in the Bristol method of the first image ２ is 1.0 mL / m ２ or more. An inkjet recording method characterized by this is provided.

2. The drying process is carried out at a temperature T (°C) or higher than the glass transition temperature Tg (°C) or melting point Tm (°C) of the first resin particles. Ｈ The inkjet recording method according to claim 1, performed at (°C).

3. The second ink application step is performed by the drying step, and in the Bristow method of the first image, 30 msec from the start of contact. １／２ Water absorption capacity up to W １ (mL / m) ２ ) 2.0 mL / min ２ The inkjet recording method according to claim 1, performed after the above steps have been taken.

4. Amount of the second ink applied ２ (mL / m) ２ ) is the amount of water absorbed W measured by the Bristow method. １ (mL / m) ２ The inkjet recording method according to claim 1, wherein the ratio to ) is 20.0 times or less.

5. Amount of the second ink applied ２ (mL / m) ２ ) is the amount of water absorbed W measured by the Bristow method. １ (mL / m) ２ The inkjet recording method according to claim 1, wherein the ratio to ) is 15.0 times or less.

6. The cumulative 50% particle size D50 of the first resin particles based on volume. Ｒ１ The inkjet recording method according to claim 1, wherein the (nm) is 80 nm or more and 400 nm or less.

7. The cumulative 50% particle size D50 of the aforementioned pigment based on volume. Ｐ The inkjet recording method according to claim 1, wherein the (nm) is 60 nm or more and 200 nm or less.

8. The content V of the first resin particles in the first ink Ｒ１ (by volume %) is the content of the inorganic particles V Ｉ The inkjet recording method according to claim 1, wherein the volume ratio to (volume %) is 0.3 times or more and 5.0 times or less.

9. The inkjet recording method according to claim 1, wherein the second ink further contains second resin particles.

10. The inkjet recording method according to claim 1, wherein the inorganic particles include titanium dioxide.

11. The inkjet recording method according to claim 1, wherein the resin forming the first resin particles is at least one selected from the group consisting of acrylic resins, polyester resins, and urethane resins.

12. The inkjet recording method according to claim 9, wherein the resin forming the second resin particles is at least one selected from the group consisting of acrylic resins and urethane resins.

13. Furthermore, the inkjet recording method according to claim 1, comprising at least one of the following steps: a first reaction solution application step of applying an aqueous reaction solution containing a reactant that reacts with the first ink to the recording medium, and a second reaction solution application step of applying an aqueous reaction solution containing a reactant that reacts with the second ink to the recording medium.

14. The inkjet recording method according to claim 13, comprising both the first reaction solution application step and the second reaction solution application step.

15. The first and second water-based inks are ejected from an inkjet recording head, and in the Bristow method, from the start of contact, 30 msec １／２ Water absorption capacity up to W ｍ (mL / m) ２ ) is 10.0 mL / m² ２ An inkjet recording device that records an image on the following recording medium, A first ink application means for applying the first ink to the recording medium, A drying means for drying at least a portion of the liquid component of the first ink applied to the recording medium to form a first image, and The device includes a second ink application means for recording the image by applying the second ink so as to overlap at least a portion of the first image, The first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume (cm³) of the inorganic particles is measured by nitrogen adsorption desorption. ３ ( / g) is 0.03 cm ３ / g or more, The second ink contains a pigment and is a different color from the first ink. The second ink application step is performed by drying at least a portion of the liquid component of the first ink, 30 msec from the start of contact in the Bristow method for the first image. １／２ Water absorption capacity up to W １ (mL / m) ２ ) 1.0 mL / min ２ An inkjet recording apparatus characterized by performing the above steps.

16. The ink is ejected from the inkjet recording head, and in the Bristow method, 30 msec from the start of contact. １／２ Water absorption capacity up to W ｍ (mL / m) ２ ) is 10.0 mL / m² ２ An ink set comprising a first water-based ink and a second water-based ink used in an inkjet recording method for recording an image on the following recording medium, The inkjet recording method includes a first ink application step of applying the first ink to the recording medium, A drying step to form a first image by drying at least a portion of the liquid component of the first ink applied to the recording medium, and The process includes a second ink application step of applying the second ink so as to overlap at least a portion of the first image to record the image, The first ink is a white ink containing inorganic particles and first resin particles, and the total pore volume of the inorganic particles, measured by nitrogen adsorption desorption, is 0.03 cm³. ３ / g or more, The second ink contains a pigment and is a different color from the first ink. The second ink application step is performed by the drying step, and in the Bristow method of the first image, 30 msec from the start of contact. １／２ Water absorption capacity up to W １ (mL / m) ２ ) 1.0 mL / min ２ An ink set characterized by being performed after the above steps have been taken.

Images