Ink jet recording method, ink jet recording apparatus, and set of aqueous ink and aqueous reaction liquid

Abstract

To provide an ink jet recording method capable of recording an image on a low- to non-absorbent recording medium, where the image includes a low gloss area having excellent abrasion resistance and a high gloss area having high quality and suppressed bleeding, the image having a glossiness that is partially controlled.SOLUTION: In an ink jet recording method, an aqueous ink containing a pigment, resin particles and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink are ejected from an ink jet recording head and applied to a non-absorbent recording medium to record an image. The ink jet recording method includes a gas blowing step of blowing gas to the recording medium to reduce liquid components, where the aqueous reaction liquid contains a first reaction liquid, and a second reaction liquid having a reaction strength with the aqueous ink lower than that of the first reaction liquid, and the image includes a low gloss area formed by applying the first reaction liquid and the aqueous ink, and a high gloss area formed by applying the second reaction liquid and the aqueous ink.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, inkjet recording methods have been increasingly used in the sign and display field, such as for printing posters and large-sized advertisements. One of the features of inkjet recording devices used in this field is that they have a larger printing area than home inkjet recording devices. Furthermore, because they need to be eye-catching, inks capable of printing highly color-developing images are required. Furthermore, images with partially controlled glossiness are expected to be eye-catching because the difference in gloss enhances the impression.

[0003] In the field of signs and displays, polyvinyl chloride sheets and polyethylene terephthalate (PET) sheets are often used as recording media. These recording media have no or almost no water-based ink absorbing layer on the recording surface, and are referred to as non-absorbent recording media (recording media that do not absorb water-based ink) or low-absorbent recording media (recording media that have low absorbency for water-based ink). Even on such non-absorbent and low-absorbent recording media, there is a demand for the ability to record high-quality images with reduced bleeding. To meet this demand, it is necessary to rapidly thicken and fix the ink applied to the recording medium and control the ink so that it is not repelled by the recording medium.

[0004] Furthermore, methods of recording images on non-absorbent recording media or low-absorbent recording media (hereinafter collectively referred to as "non-absorbent recording media") include using solvent-based inks containing organic solvents as the main component and curable inks containing polymerizable monomers. However, in recent years, there has been a growing need for recording methods that use aqueous inks in order to reduce environmental impact and improve safety.

[0005] One method for recording images on a non-absorbent recording medium using aqueous ink is to evaporate the water content of the ink on the surface of the recording medium. While this method is advantageous in terms of running costs, it tends to reduce productivity as the recording speed decreases. For this reason, methods have been proposed in which a reaction liquid that aggregates the components in the ink is used in combination with the ink. For example, a recording method has been proposed that uses a first reaction liquid containing an aggregating agent that aggregates the components in the first ink and a second reaction liquid containing an aggregating agent that aggregates the components in the second ink (Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-147405 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Document 1 does not describe partial control of the glossiness of an image. The present inventors studied images recorded on a non-absorbent recording medium using the recording method proposed in Patent Document 1. As a result, it was found that although partial control of glossiness was possible to a certain extent, bleeding in the high-gloss areas of the image was not necessarily suppressed. Furthermore, it was found that the abrasion resistance of the low-gloss areas was also insufficient, leaving room for improvement.

[0008] Therefore, an object of the present invention is to provide an inkjet recording method capable of recording an image with partially controlled glossiness, including a low-gloss area with excellent abrasion resistance and a high-quality high-gloss area with reduced bleeding, on a low- to non-absorbent recording medium. Another object of the present invention is to provide an inkjet recording apparatus used in the inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording method in which an aqueous ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink, are ejected from an inkjet recording head and applied to a recording medium to record an image, the method comprising: an air blowing step of blowing air onto the recording medium to reduce liquid components; the aqueous reaction liquid includes a first reaction liquid and a second reaction liquid that has a lower reaction strength with the aqueous ink than the first reaction liquid; the image includes a low-gloss portion formed by applying the first reaction liquid and the aqueous ink; and a high-gloss portion formed by applying the second reaction liquid and the aqueous ink; and the recording medium is subjected to a Bristow method in which the ink is blown onto the recording medium within 30 msec from the start of contact. 1 / 2 Water absorption up to 10mL / m 2 An inkjet recording method is provided, characterized in that: [Effects of the Invention]

[0010] According to the present invention, there is provided an inkjet recording method capable of recording an image with partially controlled glossiness, including a low-gloss area with excellent abrasion resistance and a high-quality high-gloss area with reduced bleeding, on a low- to non-absorbent recording medium. Furthermore, according to the present invention, there is provided an inkjet recording apparatus used in the inkjet recording method, and a set of an aqueous ink and an aqueous reaction liquid. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view schematically illustrating an embodiment of an inkjet recording apparatus of the present invention. [Figure 2] 1 is a side view schematically illustrating an embodiment of an inkjet recording apparatus of the present invention. [Figure 3] 1 is a schematic diagram illustrating an embodiment of an inkjet recording apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in further detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink and reaction liquid as dissociated ions, but for convenience it will be expressed as "containing a salt." In addition, aqueous inks and aqueous reaction liquids for inkjet printing may be simply referred to as "ink" and "reaction liquid." Unless otherwise specified, physical property values ​​are values ​​at room temperature (25°C) and normal pressure (1 atmosphere). When "(meth)acrylic acid" and "(meth)acrylate" are written, they mean "acrylic acid, methacrylic acid" and "acrylate, methacrylate," respectively.

[0013] The reaction strength of the reaction liquid with the ink is determined relatively by the viscosity of the mixture obtained by mixing the reaction liquid and ink. Specifically, assume that the viscosity (Pa·s) of the mixture obtained by mixing 100 parts by mass of ink with 7 parts by mass of reaction liquid is higher than the viscosity (Pa·s) of the mixture obtained by mixing 100 parts by mass of the same ink with 7 parts by mass of another reaction liquid. In this case, the reaction strength of this reaction liquid can be determined to be higher than the reaction strength of other reaction liquids. Note that the above mass ratio of the reaction liquid and ink mixture assumes the situation when the reaction liquid and ink come into contact on the recording medium.

[0014] The present inventors first investigated the reasons why the quality of high-gloss areas and the abrasion resistance of low-gloss areas in images recorded using two types of reaction liquid and ink are insufficient. To improve the glossiness of an image, it is necessary to reduce the reaction strength between the ink and the reaction liquid and lower the height of the dots formed. Lowering the dot height reduces the unevenness of the image surface, thereby improving the glossiness of the image. On the other hand, lowering the reaction strength between the ink and the reaction liquid reduces the pinning performance of the dots formed, making the image quality more likely to deteriorate.

[0015] As a result of further investigation, the inventors discovered that a step of blowing air onto a recording medium to which a reaction liquid and ink have been applied to reduce the liquid components on the recording medium (including water and water-soluble organic solvents in the reaction liquid and ink) can be provided, leading to the present invention. By providing a step of blowing air, it is possible to promote thickening due to drying of the reaction product between the ink and the reaction liquid, thereby improving the quality of the recorded image.

[0016] Specifically, the inkjet recording method of the present invention is a method of recording an image by ejecting an ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the ink, from an inkjet recording head and applying the ink to a recording medium. The reaction liquid includes a first reaction liquid and a second reaction liquid that has a lower reaction strength with the ink than the first reaction liquid. As described above, the inkjet recording method of the present invention includes an air blowing step in which air is blown onto the recording medium to reduce the liquid component. Furthermore, the recorded image includes a low-gloss area formed by applying the first reaction liquid and the ink, and a high-gloss area formed by applying the second reaction liquid and the ink. The inventors speculate as follows about the mechanism by which the above configuration makes it possible to record images with partially controlled glossiness, including low-gloss areas with excellent abrasion resistance and high-quality high-gloss areas with reduced bleeding, on low- to non-absorbent recording media.

[0017] To form a low-gloss area with a relatively low gloss, it is necessary to use a reaction liquid with high reaction strength in order to increase the dot height and increase the unevenness of the image surface. However, as the surface unevenness increases, the friction coefficient increases, which tends to reduce abrasion resistance. In response to this, a decrease in abrasion resistance in the low-gloss area can be suppressed by providing an air blowing process in which air is blown onto the recording medium to reduce the liquid component. It is believed that blowing air onto the surface of the recording medium to which the reaction liquid and ink have been applied volatilizes the water in the ink, increasing the proportion of water-soluble organic solvent and lowering the minimum film-forming temperature of the resin particles. This promotes melting of the resin particles, and the resin derived from the melted resin particles present in the convex areas of the image surface subsequently solidifies, thereby improving the strength of the convex areas of the image surface and improving abrasion resistance.

[0018] <Inkjet recording method, inkjet recording apparatus, and set of aqueous ink and aqueous reaction liquid> The inkjet recording method of the present invention is a method of recording an image by ejecting an aqueous ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink, from an inkjet recording head and applying them to a recording medium. The inkjet recording method of the present invention includes a step of blowing air onto the recording medium to reduce the liquid components. The aqueous reaction liquid includes a first reaction liquid and a second reaction liquid that has a lower reaction strength with the aqueous ink than the first reaction liquid. The image includes a low-gloss area formed by applying the first reaction liquid and the aqueous ink, and a high-gloss area formed by applying the second reaction liquid and the aqueous ink. The recording medium is then subjected to a Bristow method for 30 msec from the start of contact. 1 / 2 Water absorption up to 10mL / m 2 The following is the result.

[0019] The inkjet recording apparatus of the present invention is an apparatus used in an inkjet recording method in which the above-mentioned aqueous ink and aqueous reaction liquid are ejected from an inkjet recording head and applied to a recording medium to record an image. The inkjet recording apparatus of the present invention is an apparatus that is suitably used in the above-mentioned recording method. It is not necessary to provide a step of curing the image by irradiating it with active energy rays.

[0020] The set of aqueous ink and aqueous reaction liquid of the present invention is a set used in an inkjet recording method in which the aforementioned aqueous ink and aqueous reaction liquid are ejected from an inkjet recording head and applied to a recording medium to record an image. The set is suitable for use in the above-mentioned recording method. The form of the set includes a set of multiple ink cartridges, each containing multiple inks (reaction liquids) independently, and an ink cartridge formed by combining multiple ink reservoirs, each containing multiple inks (reaction liquids). The set of the present invention is not limited to the above form and may be in any form as long as it is configured to allow the inks and reaction liquids to be used in combination.

[0021] The inkjet recording method and inkjet recording apparatus (hereinafter also simply referred to as "recording method and recording apparatus") of the present invention will be described in detail below.

[0022] (Inkjet recording device) FIG. 1 is a perspective view schematically showing an embodiment of an inkjet recording apparatus of the present invention. FIG. 2 is a side view schematically illustrating one embodiment of an inkjet recording apparatus according to the present invention. As shown in FIGS. 1 and 2, the recording apparatus of this embodiment includes an inkjet recording head 22 that ejects ink. Examples of the recording head include a recording head that ejects ink and a reaction liquid by the action of mechanical energy and a recording head that ejects ink and a reaction liquid by the action of thermal energy. Of these, a recording head that ejects ink and a reaction liquid by the action of thermal energy is preferred. A recording head that ejects ink and a reaction liquid by the action of thermal energy is a thermal recording head that applies thermal energy to the ink and the reaction liquid by applying an electric pulse to an electrothermal transducer, thereby ejecting the ink and the reaction liquid from the ejection openings. This thermal recording head preferably includes a mechanism (temperature control mechanism) that heats the aqueous ink to a predetermined temperature before it is ejected from the recording head and applied to the recording medium. If a temperature control mechanism is included, the heating temperature of the ink ejected from the recording head is preferably between 35°C and 70°C. 1 and 2, the recording apparatus may be provided with an air blowing device, which is used in the air blowing step described below to blow air onto the recording medium 1 to reduce the liquid component. The air blowing device is disposed in the recording medium transport path. The air blowing device may be disposed either upstream or downstream of the recording head 22 in the recording medium transport direction.

[0023] [Blowing process] Fig. 3 is a schematic diagram showing one embodiment of an inkjet recording apparatus of the present invention. As shown in Fig. 3, a recording medium P is transported by a paper feed roller (not shown) in the direction indicated by arrow 700. Above the recording medium P, an air blower 701 is provided to blow air onto the recording medium. This air blower 701 is a drying mechanism for reducing the liquid components (such as water) in the reaction liquid and ink applied onto the recording medium, and is equipped with a heating element 702 for heating the gas (airflow) to be blown, and an air blowing section for blowing the heated gas onto the recording medium P. The heating element 702 may be any device that can control the temperature of the gas, and is preferably a device that has high heat transfer efficiency to the air.

[0024] The air blowing unit includes an air blower fan 703, an air duct 704, and an air exhaust unit 705. From the viewpoint of power consumption, the air blower fan 703 may be configured to circulate air within the air blower device 701 or to take in outside air. A temperature sensor (not shown) is provided within the air blower duct 704 to detect and control the temperature of the heating element 702. It is preferable to blow air toward the recording medium P from the upstream side in the transport direction of the recording medium P. It is more preferable that the air blower device 701 be positioned upstream of the recording head 22 in the transport direction of the recording medium P and blow air toward the recording medium P from the upstream side in the transport direction of the recording medium P. In this case, it is particularly preferable to blow air from the upstream side in the transport direction of the recording medium P in a substantially horizontal direction toward directly below the recording head 22. This allows the reaction liquid and ink to begin drying immediately after being ejected from the recording head 22, making it easier to dry the reaction liquid and ink quickly. Furthermore, blowing air toward the surface of the recording medium P may generate a large amount of steam depending on the amount of ink and reaction liquid on the recording medium P. If the drying device 701 is filled with steam, the drying efficiency may decrease. Therefore, the drying device 701 may be configured to collect the generated steam and discharge it to the outside.

[0025] The air blower 701 may be any of various conventionally known devices as long as it can dry to some extent the liquid components contained in the reaction liquid, ink, etc. applied to the recording medium P and increase the viscosity of the reaction liquid, ink, and their reactants. Among these, it is preferable to use a mechanism incorporating an air blower fan 703 in order to send (blow) an air current to the surface of the recording medium P.

[0026] In the drying process, the ink and reaction liquid do not become sufficiently viscous. Therefore, in order to prevent the air blown from the ink ejection surface side of the recording medium P from affecting the surface shape of the ink and reaction liquid, it is preferable to blow air in a direction approximately horizontal to the ink ejection surface of the recording head 22. Furthermore, multiple sending and discharging units 705 may be arranged along the transport direction of the recording medium P.

[0027] The temperature in the air blowing step can be set so that the recording medium P reaches the desired temperature, taking into consideration the transport speed of the recording medium P and the ambient temperature. Specifically, it is preferable to blow an airflow of 15°C or higher and 60°C or lower onto the recording medium, and it is more preferable to blow an airflow of 25°C or higher and 60°C or lower onto the recording medium. Furthermore, it is preferable that the temperature of the recording medium in the drying step be less than 50°C. It is also preferable to blow an airflow of 1.0 m / s or higher and 10.0 m / s or lower onto the recording medium P. The temperature of the blown airflow can be measured, for example, using a K-type thermocouple thermometer. A specific example of a measuring device is the "AD-5605H" (manufactured by A&D).

[0028] [Heating process] The recording method of the present invention preferably includes a heating step after the air blowing step, in which the recording medium is heated to a temperature higher than that of the air blowing step to dry it. In the heating step, the ink and its aggregates, which have been thickened to a certain extent in the air blowing step, are heated quickly enough to prevent them from flowing, thereby fixing them to the recording medium. As shown in FIG. 3, the heating device 706 is a mechanism having a similar configuration to the air blowing device 701. The heating device 706 may be any device capable of further removing the liquid components that have been removed to a certain extent by drying with the air blowing device 701. In particular, from the viewpoint of energy efficiency, it is preferable to use a mechanism incorporating a fan for blowing high-temperature gas (hot air) onto the recording medium P. In FIG. 3, reference numerals 707, 708, 709, and 710 denote a heating element, a blower fan, an air duct, and an air exhaust section, respectively.

[0029] The heating temperature in the heating device 706 is preferably set to a temperature that does not cause excessive drying, from the viewpoint of quickly evaporating the liquid components and suppressing deformation of the recording medium P. In particular, it is preferable to heat to a temperature higher than the minimum film-forming temperature of the resin particles contained in the ink. Furthermore, when using ink containing wax particles, it is preferable to heat to a temperature lower than the minimum film-forming temperature of the wax particles. The minimum film-forming temperature is the minimum temperature required for the resin particles or wax particles to form a film. Specifically, a dispersion of resin particles or wax particles is applied onto a thermally conductive plate with a temperature gradient and dried to form a film of resin particles or wax particles. The minimum film-forming temperature is then determined as the temperature at the lowest point on the thermally conductive plate within the non-whitened region of the formed film.

[0030] The means for heating the recording medium is not particularly limited, and examples thereof include known heating means such as a heater, air blowing means using air such as a dryer, and a combination of these. That is, the inkjet recording apparatus preferably includes a mechanism (heating means) for heating the recording medium to which the ink and reaction liquid have been applied. Examples of heating means include the above-mentioned heating means, air blowing means, and a combination of these. Examples of heat treatment methods include applying heat from the side (backside) opposite to the recording surface (ink-applied surface) of the recording medium using a heater or the like, applying warm or hot air to the recording surface of the recording medium, and heating from the recording surface or backside using an infrared heater.

[0031] In order to improve the scratch resistance of the image, the heating temperature of the recording medium to which the ink and reaction liquid have been applied is preferably 50° C. or higher and 90° C. or lower. The heating temperature of the recording medium to which the ink and reaction liquid have been applied may be read by a sensor incorporated in a position corresponding to the heating means of the recording device, or may be determined from the relationship between the amount of heat determined in advance according to the type of ink and recording medium and the temperature of the recording medium.

[0032] In the recording device shown in FIGS. 1 and 2, a heater 25, which is a heating device, is supported by a frame (not shown) and is located downstream in the sub-scanning direction A from the position where the recording head 22 reciprocates in the main scanning direction B. The recording medium 1 to which ink has been applied can be heated by the heater 25. Specific examples of the heater 25 include a sheath heater and a halogen heater. The heater 25 is covered by a heater cover 26. The heater cover 26 is a member for efficiently irradiating the heat generated by the heater 25 onto the recording medium 1. The heater cover 26 also protects the heater 25. The recording medium 1 to which ink ejected from the recording head 22 has been applied is taken up by a take-up spool 27 to form a roll-shaped taken-up medium 24.

[0033] (Recording medium) In the recording method and recording device of the present invention, a non-absorbent recording medium (a low to non-absorbent recording medium) is used as the recording medium. The non-absorbent recording medium is a recording medium that is absorbed within 30 msec from the start of contact in the Bristow method described in JAPAN TAPPI Paper Pulp Test Method No. 51, "Liquid Absorbency Test Method for Paper and Paperboard." 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2 In the present invention, a recording medium that satisfies the above-mentioned condition of water absorption amount is defined as a "low to non-absorbent recording medium." Inkjet recording media (glossy paper, matte paper, etc.) having an ink-receiving layer formed of inorganic particles and plain paper having no coating layer have a water absorption amount of 10 mL / m or less. 2 It is an "absorbent recording medium" that exceeds this.

[0034] Examples of non-absorbent recording media that can be used include plastic films, recording media in which a plastic film is bonded to the recording surface of a substrate, and recording media in which an organic resin coating layer is provided on the recording surface of a substrate containing cellulose pulp. Of these, plastic films are preferred, and recording media in which an organic resin coating layer is provided as an organic resin layer on the recording surface of a substrate containing cellulose pulp are also preferred.

[0035] When the ink used in the recording method and recording apparatus of the present invention is applied to a non-absorbent recording medium, components such as water and water-soluble organic solvents volatilize, concentrating the resin particles. This promotes fusion between the concentrated resin particles, improving the abrasion resistance of the recorded image. In contrast, when the ink is applied to a recording medium with high liquid component absorption, fusion between the resin particles is less likely to be promoted, resulting in insufficient improvement in the abrasion resistance of the image. Note that the recording medium in this specification does not refer to a transfer medium, but rather to a recording medium on which an image is recorded as a recorded product.

[0036] (ink) The ink is a water-based ink for inkjet printing containing a pigment, resin particles, and a water-soluble organic solvent. The components constituting the ink will be described in detail below.

[0037] [Colorant] The ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably 0.1% to 15.0% by mass, and more preferably 1.0% to 10.0% by mass, based on the total mass of the ink.

[0038] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, dioxazine, and perinone.

[0039] Pigment dispersion methods that can be used include resin-dispersed pigments that use a resin as a dispersant and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface. Also available are resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microencapsulated pigments in which the pigment particle surface is coated with a resin or the like. Among these, it is preferable to use resin-dispersed pigments in which a resin as a dispersant is physically adsorbed onto the pigment particle surface, rather than resin-bonded pigments or microencapsulated pigments. In other words, it is preferable for the pigment to be one that is dispersed by the action of a resin dispersant.

[0040] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin described below, particularly a water-soluble resin, can be used. The content (mass %) of the pigment in the ink is preferably 0.3 to 10.0 times the mass ratio of the content of the resin dispersant.

[0041] Self-dispersing pigments can be used in which anionic groups such as carboxylic acid groups, sulfonic acid groups, and phosphonic acid groups are bonded to the surface of pigment particles directly or via another atomic group (-R-). The anionic group can be either an acid type or a salt type. If the anionic group is a salt type, it can be either partially dissociated or completely dissociated. When the anionic group is a salt type, examples of the cation that serves as the counter ion include alkali metal cations, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include linear or branched alkylene groups having 1 to 12 carbon atoms; arylene groups such as phenylene and naphthylene; carbonyl groups; imino groups; amide groups; sulfonyl groups; ester groups; and ether groups. Furthermore, combinations of these groups may also be used.

[0042] Inorganic oxides such as titanium oxide react with water molecules in ink to form hydroxyl groups (hereinafter also referred to as "surface hydroxyl groups"). For this reason, in the case of aqueous inkjet inks, titanium oxide is typically surface-treated with inorganic oxides such as alumina or silica to further improve the storage stability of the ink while utilizing the surface hydroxyl groups. The surface hydroxyl groups of particulate titanium oxide (titanium oxide particles) have properties specific to the inorganic oxide used in the surface treatment, and the isoelectric point, which is an indicator of the acid strength of the inorganic oxide, varies depending on the type of inorganic oxide. Therefore, the surface of titanium oxide particles reflects the properties of the inorganic oxide (surface treatment agent) used in the surface treatment, and the surface charge of titanium oxide particles is strongly dependent on the pH of the aqueous medium, the type of surface treatment agent, and the amount of surface treatment agent used.

[0043] Titanium oxide is a white pigment that exists in three crystal forms: rutile, anatase, and brookite. Of these, rutile titanium oxide is preferred. Examples of industrial methods for producing titanium oxide include the sulfuric acid method and the chlorine method. Titanium oxide may be obtained by any of these methods.

[0044] Titanium oxide may be surface-coated (surface-treated) with an inorganic oxide or an organic substance. In particular, titanium oxide surface-treated with alumina and silica is preferred. The use of surface-treated titanium oxide is expected to suppress photocatalytic activity and improve dispersibility. "Alumina" herein refers collectively to aluminum oxides, such as aluminum oxide. Furthermore, "silica" herein refers collectively to silicon dioxide and substances composed of silicon dioxide. Most of the alumina and silica coating titanium oxide exists in the form of silicon dioxide and aluminum oxide. The proportions of alumina and silica in titanium oxide particles, i.e., the coating amounts of alumina and silica, can be measured, for example, by quantitative analysis of aluminum and silicon elements using inductively coupled plasma (ICP) emission spectrometry. In this case, assuming that all atoms coating the surface are in the form of oxides, the obtained values ​​of aluminum and silicon can be converted into oxides (alumina and silica) for calculation.

[0045] Surface treatment methods for titanium oxide include wet treatment methods and dry treatment methods. For example, titanium oxide can be dispersed in a liquid medium and then reacted with a surface treatment agent such as sodium aluminate or sodium silicate for surface treatment. By appropriately changing the ratio of these surface treatment agents, desired properties can be adjusted. In addition to alumina and silica, inorganic oxides such as zinc oxide and zirconia; and organic substances such as polyols can also be used for surface treatment, as long as the effects of the present invention are not impaired.

[0046] [Resin particles] The ink contains resin particles. The content (mass%) of resin particles in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. The content (mass%) of resin particles in the ink is preferably 1.5 times or more, and more preferably 1.7 times or more, the mass ratio relative to the pigment content (mass%). Furthermore, the above mass ratio is preferably 10.0 times or less. The resin particles are present in the ink in a dispersed state, i.e., in the form of a resin emulsion.

[0047] In this specification, "resin particles" refers to a resin that is present in a state in which it is not dissolved in the aqueous medium of the ink, and more specifically, refers to a resin that can be present in the aqueous medium in the form of particles whose particle diameter can be measured by dynamic light scattering. In contrast, "water-soluble resin" refers to a resin that is present in a state in which it is dissolved in the aqueous medium of the ink. "Resin particles" can also be referred to as "water-dispersible resin (water-insoluble resin)."

[0048] Whether a certain resin corresponds to "resin particles" can be determined according to the method shown below. First, a liquid containing the resin to be determined is prepared and diluted with pure water so that the resin content is approximately 1.0% to prepare a sample. Then, when the particle size of the resin in the sample is measured by dynamic light scattering, if particles having a particle size are measured, the resin is determined to be "resin particles" (i.e., a "water-dispersible resin"). On the other hand, if particles having a particle size are not measured, the resin is determined not to be "resin particles" (i.e., a "water-soluble resin"). The measurement conditions in this case can be, for example, as follows: [Measurement conditions] SetZero:30s Number of measurements: 3 Measurement time: 120 seconds Shape: true spherical Refractive index: 1.6 Density: 1.0

[0049] As the particle size distribution measuring device, a particle size analyzer using a dynamic light scattering method (for example, trade name "Nanotrac WAVEII-Q" (manufactured by Microtrac Bell)) can be used. Of course, the particle size distribution measuring device and measurement conditions used are not limited to those described above. Furthermore, the average particle diameter (50% cumulative particle diameter on a volume basis) of pigment or wax particles can be measured using the above-described device and conditions. The average particle diameter of resin particles is the diameter of the particle that is 50% cumulatively calculated from the smallest particle diameter on a particle diameter cumulative curve, based on the total volume of the measured particles.

[0050] The average particle size of the resin particles (volume-based cumulative 50% particle size (D50)) measured by dynamic light scattering is preferably 60 nm or more and 180 nm or less. By using an ink containing resin particles with an average particle size within the above range, the scratch resistance of the recorded image can be further improved.

[0051] The acid value of the resin constituting the resin particles is preferably 5 mgKOH / g or more and 100 mgKOH / g or less. The weight average molecular weight of the resin constituting the resin particles is preferably 1,000 or more and 2,000,000 or less. The resin particles do not need to contain a colorant.

[0052] The glass transition temperature of the resin particles is preferably 40° C. or higher and 120° C. or lower, and more preferably 50° C. or higher and 100° C. or lower. The glass transition temperature of the resin particles can be measured using a differential scanning calorimeter (DSC).

[0053] The resin constituting the resin particles can be appropriately selected from the same constituting units of the water-soluble resins described below, such as acrylic resins, urethane resins, polyester resins, and various copolymers. Examples of copolymers include styrene-acrylic resin, styrene-butadiene resin, polyether-polyurethane resin, and polyester-polyurethane resin.

[0054] The reactivity of the resin particles can be controlled, for example, by adjusting the density of the anionic groups on the surface of the resin particles, the acid value of the resin particles, etc. Increasing the density of the carboxylic acid groups of the resin particles or increasing the acid value of the resin particles can increase the viscosity of the mixture obtained by mixing the ink and the reaction liquid.

[0055] [Water-soluble resin] The ink may contain a water-soluble resin (hereinafter also simply referred to as "resin"). The use of ink containing a water-soluble resin can further improve the scratch resistance of the recorded image. The water-soluble resin can be added to the ink (i) to stabilize the pigment dispersion, i.e., as a resin dispersant or its auxiliary. It can also be added to the ink (ii) to improve various properties of the recorded image. Examples of the form of the water-soluble resin include block copolymers, random copolymers, graft copolymers, and combinations thereof.

[0056] The resin content (mass %) in the ink is preferably 0.1% to 20.0% by mass, and more preferably 0.5% to 15.0% by mass, based on the total mass of the ink.

[0057] [Resin Composition] Examples of the resin include acrylic resins, urethane 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 more preferred.

[0058] The acrylic resin is preferably one having a hydrophilic unit and a hydrophobic unit as constituent units. Among these, a resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of a monomer having an aromatic ring and a (meth)acrylic acid ester-based monomer is preferred. A resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is particularly preferred. These resins are likely to interact with pigments, and can therefore be suitably used as resin dispersants for dispersing pigments.

[0059] The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Specific examples of hydrophilic monomers having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, and anionic monomers such as anhydrides and salts of these acidic monomers. Examples of cations constituting the salts of acidic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit not having a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer not having a hydrophilic group such as an anionic group. Specific examples of hydrophobic monomers include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0060] The urethane resin can be obtained by reacting, for example, polyisocyanate with a polyol. Alternatively, a chain extender may be further added to the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0061] [Resin properties]

[0062] The water-soluble resin preferably has an acid value of 100 mgKOH / g or more and 250 mgKOH / g or less, and a weight-average molecular weight of 3,000 or more and 15,000 or less.

[0063] [Wax particles] The ink can contain particles formed from wax (wax particles). By using an ink containing wax particles, it is possible to record images with further improved abrasion resistance. The wax may be a composition containing components other than wax, or may be wax itself. The wax particles may be dispersed using a dispersant such as a surfactant or a water-soluble resin. One type of wax may be used alone, or two or more types may be used in combination. The content (mass %) of wax particles in the ink is preferably 1.0% by mass or more and 5.0% by mass or less, and more preferably 1.5% by mass or more and 3.0% by mass or less, based on the total mass of the ink.

[0064] In a narrow sense, wax is an ester of a water-insoluble higher monohydric or dihydric alcohol and a fatty acid, and includes animal waxes and vegetable waxes but excludes oils and fats. In a broad sense, wax includes high-melting-point fats, mineral waxes, petroleum waxes, and blends and modified products of various waxes. In the recording method of the present invention, any wax in the broad sense can be used without particular limitation. Wax in the broad sense can be classified into natural waxes, synthetic waxes, blends thereof (blended waxes), and modified products thereof (modified waxes).

[0065] Examples of natural waxes include animal waxes, vegetable waxes, mineral waxes, and petroleum waxes. Examples of animal waxes include beeswax, spermaceti, and wool wax (lanolin). Examples of vegetable waxes include palm wax, carnauba wax, candelilla wax, rice wax, Japan wax, oryza sativa wax, and sugarcane wax. Examples of mineral waxes include montan wax, ozokerite, ceresin, and lignite wax. Examples of petroleum waxes include paraffin, microcrystalline wax, and petrolatum.

[0066] Examples of synthetic waxes include hydrocarbon waxes such as Fischer-Tropsch wax and polyolefin wax (e.g., polyethylene wax, polypropylene wax). Compounded waxes are mixtures of the above waxes. Modified waxes are those obtained by modifying the above waxes through oxidation, hydrogenation, alcohol modification, acrylic modification, or urethane modification. Examples of modified waxes include paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. Examples of hydrogenated waxes include castor wax and opal wax.

[0067] The wax is preferably solid at room temperature (25°C). The melting point (°C) of the wax is preferably 40°C or higher and 120°C or lower, and more preferably 50°C or higher and 100°C or lower. The melting point of the wax can be measured in accordance with the test method described in 5.3.1 (Melting Point Test Method) of JIS K 2235:1991 (Petroleum Wax). In the case of microcrystalline wax, petrolatum, and mixtures of multiple waxes, more accurate measurement can be achieved by using the test method described in 5.3.2. The melting point of the wax is easily affected by properties such as molecular weight (the higher the molecular weight, the higher the melting point), molecular structure (linear chains have a high melting point, and branched chains have a lower melting point), crystallinity (the higher the crystallinity, the higher the melting point), and density (the higher the crystallinity, the higher the melting point). Therefore, by controlling these properties, it is possible to obtain a wax having a desired melting point. The melting point of the wax in the ink can be measured, for example, by ultracentrifuging the ink, separating the wax, washing and drying it, and then measuring it in accordance with the test method described above.

[0068] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. Preferably, deionized water or ion-exchanged water is used as the water. The water content (mass %) in the ink is preferably 50.0 mass % or more and 95.0 mass % or less, based on the total mass of the ink.

[0069] The ink contains a water-soluble organic solvent. After the ink is applied to a non-absorbent recording medium, the water evaporates and decreases during an air blowing process, concentrating the water-soluble organic solvent and resin particles. This promotes fusion between the concentrated resin particles, improving the scratch resistance of the recorded image. As the water-soluble organic solvent, any solvent that can be used in inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing solvents, and sulfur-containing solvents, can be used. The water-soluble organic solvent may be used alone or in combination of two or more. The content (mass %) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, based on the total mass of the ink.

[0070] The vapor pressure of the water-soluble organic solvent at 25°C and 1 atmosphere is preferably 1.0 kPa or less. If the vapor pressure is too high, the solvent may evaporate before sufficiently coming into contact with the resin particles in the ink, and the effect of improving the scratch resistance of the image may not be sufficiently achieved.

[0071] [Other ingredients] The ink may contain various other components as needed. Examples of other components include various additives such as antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and antireducing agents. However, it is preferable that the ink does not contain the reactants contained in the reaction liquid.

[0072] [Ink properties] The ink is an aqueous ink used in inkjet printing. 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. Furthermore, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0073] (Reaction solution) The reaction liquid used in the recording method of the present invention is a liquid containing a reactant that reacts with the ink, and is an aqueous reaction liquid for inkjet use that is used together with the ink. The recording method of the present invention, for example, includes a step of applying the reaction liquid to a recording medium. In particular, it is preferable to apply the reaction liquid before applying the ink to the recording medium, or to apply the ink and the reaction liquid in parallel. Each component used in the reaction liquid will be described in detail below.

[0074] [Reactant] The reaction liquid reacts with the ink upon contact with it to aggregate the components in the ink (components having anionic groups, such as resins, surfactants, and self-dispersing pigments), and contains a reactant, such as an organic acid, a polyvalent metal salt, or a cationic resin.

[0075] [Organic acid] The organic acid-containing reaction solution has buffering properties in the acidic range (less than pH 7.0, preferably pH 2.0 to 5.0), thereby efficiently converting anionic groups present in the ink into the acid form and causing them to aggregate. Examples of organic acids include monocarboxylic acids and salts thereof, such as formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrolecarboxylic acid, furancarboxylic acid, picolinic acid, nicotinic acid, thiophenecarboxylic acid, levulinic acid, and coumaric acid; dicarboxylic acids and salts thereof, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, and tartaric acid; tricarboxylic acids and salts thereof, such as citric acid and trimellitic acid; and tetracarboxylic acids and salts thereof, such as pyromellitic acid. The content (mass %) of the organic acid in the reaction liquid is preferably 1.0 mass % or more and 50.0 mass % or less based on the total mass of the reaction liquid.

[0076] [Polyvalent metal salts] Polyvalent metal salts are compounds composed of divalent or higher metal ions (polyvalent metal ions) and anions. Polyvalent metal salts dissociate in the reaction solution to form polyvalent metal ions, which aggregate dispersed pigments and other materials by the action of anionic groups in the ink. Examples of polyvalent metal ions 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 anions constituting polyvalent metal salts include trivalent metal ions such as Cl. - , Br - , I - , ClO - , ClO2 - , ClO3 - , ClO4 - , NO2 - , NO3 -, SO4 2- , CO3 2- , HCO3 - , PO4 3- , HPO4 2- , and H2PO4 - Inorganic anions such as HCOO - , (COO - )2, COOH(COO - ), CH3COO - , CH3CH(OH)COO - , C2H4(COO - )2, C6H5COO - , C6H4(COO - )2, and CH3SO3 - Examples of organic anions include:

[0077] Specific examples of polyvalent metal salts include calcium carbonate, such as heavy calcium carbonate and light calcium carbonate, calcium nitrate, calcium chloride, calcium sulfate, magnesium sulfate, calcium hydroxide, magnesium chloride, magnesium carbonate, barium sulfate, barium chloride, zinc carbonate, zinc sulfide, aluminum silicate, calcium silicate, magnesium silicate, copper nitrate, calcium acetate, magnesium acetate, aluminum acetate, aluminum sulfate, calcium methanesulfonate, calcium lactate, magnesium lactate, calcium propionate, calcium acetate, calcium pantothenate, and calcium gluconate. These polyvalent metal salts may contain water of hydration. The content (mass %) of the polyvalent metal salt in the reaction solution is preferably 1.0% by mass or more and 20.0% by mass or less, based on the total mass of the reaction solution.

[0078] [Cationic Resin] Cationic resins have cationic moieties in their structure and aggregate dispersed pigments and other components via the action of anionic groups in the ink. Examples of cationic resins include resins with primary, secondary, or tertiary amine structures and resins with quaternary ammonium salt structures. Specific examples include resins with structures of vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, guanidine, diallyldimethylammonium chloride, and alkylamine-epichlorohydrin condensates. To enhance solubility in the reaction solution, the cationic resin can be used in combination with an acidic compound or subjected to a quaternization treatment. 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.

[0079] [Aqueous medium] The reaction liquid is an aqueous reaction liquid containing at least water as an aqueous medium. Examples of the aqueous medium used in the reaction liquid include the same aqueous media as those that can be contained in the ink.

[0080] It is preferable that the Hansen SP value (HSP1) of the resin particles in the ink and the Hansen SP value (HSP2) of the water-soluble organic solvent in the reaction liquid satisfy the relationship of the following formula (1): Using resin particles and a water-soluble organic solvent that satisfy the relationship of the following formula (1) effectively promotes the dissolution and swelling of the resin particles, thereby improving film-forming properties and further improving the scratch resistance of the recorded image. |HSP1-HSP2|≦5.0 (1)

[0081] In this specification, the Hansen SP value (HSP1) of resin particles is a value measured by dynamic light scattering, and the Hansen SP value (HSP2) of water-soluble organic solvents is a value measured by computer software Hansen Solubility Parameters in Practice 4th Edition 4.1.07 (HSPiP).

[0082] [Other ingredients] The reaction liquid may contain various other components as needed, including the same components as those that can be contained in the ink.

[0083] [Physical properties of reaction solution] The reaction liquid is an aqueous reaction liquid applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the reaction liquid at 25°C is preferably 20 mN / m or more and 60 mN / m or less. Furthermore, the viscosity of the reaction liquid at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the reaction liquid at 25°C is preferably 5.0 or more and 9.5 or less, and more preferably 6.0 or more and 9.0 or less.

[0084] [Reaction strength of reaction solution] The reaction liquid includes a first reaction liquid and a second reaction liquid having a lower reactivity with the ink than the first reaction liquid. The image recorded by the recording method of the present invention includes a low-gloss area formed by applying the first reaction liquid and the ink, and a high-gloss area formed by applying the second reaction liquid and the ink. The viscosity (Pa·s) of the first mixture obtained by mixing 100 parts by mass of ink and 7 parts by mass of the first reaction liquid is preferably 2.0 times or more relative to the viscosity (Pa·s) of the second mixture obtained by mixing 100 parts by mass of ink and 7 parts by mass of the second reaction liquid. This ratio is more preferably 2.0 times or more and 5.0 times or less. By using first and second reaction liquids with a ratio of 2.0 times or more, an image with more controlled glossiness can be recorded.

[0085] In the examples described below, the viscosity of the mixtures (first mixture, second mixture) obtained by mixing the ink and the reaction liquid was measured using the following procedure. First, the mixture obtained by mixing the ink and the reaction liquid at a predetermined mass ratio (100 mass parts of aqueous ink to 7 mass parts of aqueous reaction liquid) was stirred for 10 seconds using a vortex mixer (product name "TUBE MIXER TM-2N", manufactured by AS ONE) at a setting of 10. After stirring, the viscosity of the mixture can be measured using an E-type viscometer (product name "RE-80L", manufactured by Toki Sangyo).

[0086] The viscosity of the mixture can be controlled, for example, by adjusting the content of the reactant in the reaction solution, the content of the cationic resin, the molecular weight of the cationic resin, the cationic degree of the cationic resin, and the valence of the organic acid. The viscosity of the mixture can also be controlled by adjusting the composition of the ink used in combination. For example, when the ink contains a self-dispersed pigment, the viscosity of the mixture can be controlled by adjusting the density of carboxylic acid groups bonded to the pigment particle surface directly or via other atomic groups. When the ink contains a resin-dispersed pigment, the viscosity of the mixture can be controlled by adjusting the acid value of the resin dispersant used. Furthermore, the viscosity of the mixture can also be controlled by adjusting the acid value of the resin constituting the resin particles in the ink, the content of the resin particles, the acid value of the water-soluble resin, and the content of the water-soluble resin. For example, the viscosity of the mixture can be increased by increasing the density of the carboxylic acid groups in the self-dispersed pigment, increasing the acid value of the resin dispersant in the resin-dispersed pigment, increasing the acid value of the resin constituting the resin particles, or increasing the acid value of the water-soluble resin. [Example]

[0087] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded. The terms "parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0088] <Preparation of reaction solution> Each reaction solution was prepared by mixing the components (unit: %) shown in Tables 1 and 2, thoroughly stirring, and then filtering under pressure through a 3.0 μm pore size cellulose acetate filter (Advantec). When magnesium sulfate was used as a reactant, the amount of magnesium sulfate heptahydrate was shown in Tables 1 and 2. Details of each component in Tables 1 and 2 are given below. Polyquat 40u05NV: Aqueous solution of cationic resin, 40.0% concentration, manufactured by Katpol GmbH Acetylenol E100: Acetylene glycol surfactant, manufactured by Kawaken Fine Chemicals Proxel GXL(S): Preservative, manufactured by Arch Chemicals

[0089] TIFF2025169906000001.tif69170

[0090] TIFF2025169906000002.tif69170

[0091] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-ethyl acrylate-acrylic acid copolymer (resin dispersant) with an acid value of 150 mgKOH / g and a weight-average molecular weight of 8,000 was prepared. 20.0 parts of the resin dispersant were neutralized with potassium hydroxide in an amount equimolar to the acid value, and an appropriate amount of pure water was added to prepare an aqueous solution of the resin dispersant with a resin (solids) content of 20.0%. A mixture was obtained by mixing 10.0 parts of CI Pigment Blue 15:3, 15.0 parts of the resin dispersant aqueous solution, and 75.0 parts of pure water. The resulting mixture and 200 parts of 0.3 mm diameter zirconia beads were placed in a batch-type vertical sand mill (Imex) and dispersed for 5 hours with water cooling. After centrifuging to remove coarse particles, the mixture was pressure-filtered through a cellulose acetate filter (Advantec) with a pore size of 3.0 μm. This yielded Pigment Dispersion 1 with a pigment content of 10.0% and a resin dispersant content of 3.0%.

[0092] (Pigment dispersion 2) Pigment Dispersion Liquid 2 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the case of Pigment Dispersion Liquid 1 described above, except that CI Pigment Red 122 was used instead of CI Pigment Blue 15:3.

[0093] (Pigment dispersion 3) Pigment Dispersion Liquid 3 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the case of Pigment Dispersion Liquid 1 described above, except that CI Pigment Yellow 74 was used instead of CI Pigment Blue 15:3.

[0094] (Pigment dispersion 4) Pigment dispersion 4 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the case of pigment dispersion 1, except that carbon black was used instead of CI Pigment Blue 15:3.

[0095] (Pigment dispersion 5) 40.0 parts of rutile titanium dioxide, 1.2 parts of 3-(methoxy(polyoxyethylene)9-12)propyltrimethoxysilane, and ion-exchanged water for a total of 100.0 parts of the components were mixed and pre-dispersed using a homogenizer. The rutile titanium dioxide used was "TITANIX JR-800" (manufactured by Teika, surface treatment: alumina, silica). The mixture was then dispersed using 0.5 mm zirconia beads at 25°C in a paint shaker for 12 hours. The zirconia beads were filtered off, and an appropriate amount of ion-exchanged water was added as needed to obtain Pigment Dispersion 5, which had a pigment (titanium dioxide) content of 40.0%.

[0096] <Production of resin particles> (Resin particles 1) 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed in a four-neck flask equipped with a stirrer, reflux condenser, and nitrogen gas inlet tube. 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant were mixed to prepare an emulsion. The reactive surfactant used was "ADEKA REASOAP ER20" (manufactured by ADEKA, nonionic surfactant, number of moles of ethylene oxide group added: 20). Under a nitrogen atmosphere, the prepared emulsion was added dropwise to the four-neck flask over 1 hour, and a polymerization reaction was carried out for 2 hours with stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion of resin particles 1 with a resin particle (solid content) content of 25.0%. The average particle diameter of resin particles 1 was 180 nm.

[0097] (Resin particles 2) An aqueous dispersion of resin particles 2 having a resin particle (solid content) content of 25.0% was prepared in the same manner as for resin particles 1, except that the polymerization temperature was changed to 60° C. The average particle diameter of resin particles 2 was 200 nm.

[0098] (Resin particles 3) An aqueous dispersion of resin particles 3 having a resin particle (solid content) content of 25.0% was prepared in the same manner as for resin particles 1, except that the polymerization temperature was changed to 95° C. The average particle diameter of resin particles 3 was 60 nm.

[0099] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in Table 3, thoroughly stirring, and then filtering under pressure through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm. Details of each component in Table 3 are shown below. Acetylenol E100: Acetylene glycol surfactant, manufactured by Kawaken Fine Chemicals Proxel GXL(S): Preservative, manufactured by Arch Chemicals

[0100] TIFF2025169906000003.tif102170

[0101] <Preparing the recording medium> The following recording media 1 and 2 were prepared. Recording media 1 was used for recording 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 0mL / m 2 More than 10mL / m 2 On the other hand, recording medium 2 was measured at 30 msec from the start of contact in the Bristow method. 1 / 2 Water absorption up to 10mL / m 2 It is a recording medium that exceeds the Recording medium 1: Product name "Scotchcal Graphic Film IJ1220N", manufactured by 3M, material: polyvinyl chloride Recording medium 2: High-quality dedicated paper, product name "HR-101S", manufactured by Canon

[0102] <Evaluation> (Image recording) An inkjet recording device (product name "imagePROGRAF PRO-2000," manufactured by Canon) equipped with a recording head that ejects ink using thermal energy was prepared. The recording duty of this inkjet recording device is defined as 100% when one 4.0 ng ink droplet is deposited on a unit area of ​​1 / 1,200 inch x 1 / 1,200 inch. An air blower that blows air to reduce the liquid components on the recording medium to which the reaction liquid and ink are deposited, and a heating device that subsequently heats and dries the recording medium, were incorporated into the prepared inkjet recording device. The first reaction liquid, second reaction liquid, and ink combinations shown in Table 5 were filled into cartridges and then installed in the inkjet recording device. Using the inkjet recording device, the first reaction liquid, second reaction liquid, and ink were deposited in this order on the type of recording medium shown in Table 5. The first reaction liquid and second reaction liquid were deposited on separate areas of the recording medium so that they did not overlap. This resulted in a 5 cm x 5 cm solid image (low gloss area) using the first reaction liquid and ink, and a 5 cm x 5 cm solid image (high gloss area) using the second reaction liquid and ink. The printing duty for the first reaction liquid and the second reaction liquid was 50%, and the printing duty for the ink was 160%. The printing environment was a temperature of 25°C and a relative humidity of 50%. The printed image was then dried using a blower according to the drying method shown in Table 5. The air temperature and speed were measured on the recording medium. Details of the drying method are shown in Table 4. Note that the blower blew air toward the recording medium from the upstream side in the recording medium transport direction. In Table 4, when the blower was installed in a position upstream of the recording head in the recording medium transport direction, the air was blown from the upstream side in the recording medium transport direction, in a substantially horizontal direction, directly below the recording head. After drying, the printed image was heated using a heating device at the heating temperature shown in Table 5. In the present invention, the evaluation criteria for each item shown below were such that "A" and "B" were acceptable levels and "C" was unacceptable. The evaluation results are shown in Table 6.

[0103] The viscosity (Pa s) of the first mixture obtained by mixing 100 parts of ink with 7 parts of the first reaction liquid and the viscosity (Pa s) of the second mixture obtained by mixing 100 parts of ink with 7 parts of the second reaction liquid were measured. The viscosity (Pa s) of the first mixture / viscosity (Pa s) of the second mixture (times) was then calculated. The calculated values ​​are shown in Table 5.

[0104] TIFF2025169906000004.tif221170

[0105] TIFF2025169906000005.tif228170

[0106] (Partial control of glossiness) Two fluorescent lamps, spaced 5cm apart and 10cm apart, were used as observation light sources, and the fluorescent lamps were projected onto the image from a distance of 2m. The shape of the fluorescent lamps projected onto the image was visually confirmed at an illumination angle of 45° and an observation angle of 45°, and the image clarity of the high-gloss and low-gloss areas was evaluated according to the evaluation criteria shown below. AA: Two fluorescent lamps spaced 5cm apart were clearly projected onto the image. A: The edges of the two projected fluorescent lights spaced 5cm apart were blurred, but the boundary was discernible. B: The boundary between two projected fluorescent lights spaced 5 cm apart was indistinguishable, but the boundary between two projected fluorescent lights spaced 10 cm apart was discernible. C: The boundary between the two projected fluorescent lights spaced 10cm apart was not visible.

[0107] The "rank of image clarity in high gloss areas" and the "rank of image clarity in low gloss areas" were compared, and the local control of gloss was evaluated according to the following evaluation criteria. A: The rank of image clarity in the high gloss area was two ranks higher than the rank of image clarity in the low gloss area. B: The rank of image clarity in the high gloss area was one rank higher than the rank of image clarity in the low gloss area. C: The rank of image clarity in the high gloss area was the same as or lower than the rank of image clarity in the low gloss area.

[0108] (Abrasion resistance of low gloss areas) A friction test was carried out using an abrasion resistance tester (manufactured by Tester Sangyo), an abrasion tester II (Gakushin type) conforming to JIS L 0849, in which the surface of the recorded image was rubbed back and forth 150 times with a load of 500 g using a white rubbing cloth (cotton) specified in JIS L 0 803. The image after the rub test was visually inspected, and the abrasion resistance of the low gloss area was evaluated according to the evaluation criteria shown below. A: No scratches were observed on the image after 150 strokes. B: Scratches were observed on the image after 150 reciprocal passes, but the white background of the recording medium was not visible. C: Scratches were observed on the image after 150 reciprocal passes, and the white background of the recording medium was visible.

[0109] (Prevents bleeding in high gloss areas) Using the inkjet recording device described above, the first reaction liquid, the second reaction liquid, and the ink were applied in the same recording pass to record a thin line with a line width of 4 pixels (input line width: 1 / 600 inch x 4 = 169 μm) and a recording duty of 200% on the recording medium. The line width (measured line width (μm)) of the recorded thin line was measured using a personal image quality evaluation system (product name "Personal IAS", manufactured by Quality Engineering Associates). The difference from the input line width was calculated using the following formula (2), and bleeding suppression in high-gloss areas was evaluated according to the evaluation criteria shown below. Difference from input line width (μm) = Measured line width (μm) - 169 (μm) (2) A: The difference from the input line width was 120 μm or less. B: The difference from the input line width was more than 120 μm and 140 μm or less. C: The difference from the input line width exceeded 140 μm.

[0110] TIFF2025169906000006.tif229170

Claims

1. An inkjet recording method in which an aqueous ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink, are ejected from an inkjet recording head and applied to a recording medium to record an image, a blowing step of blowing air onto the recording medium to reduce the liquid component, The aqueous reaction liquid is a first reaction solution, and a second reaction liquid having a lower reactivity with the aqueous ink than the first reaction liquid; Including, The image is a low-gloss portion formed by applying the first reaction liquid and the water-based ink; a high-gloss portion formed by applying the second reaction liquid and the water-based ink; and Including, The recording medium is １／２ Water absorption up to 10 mL / m ２ An inkjet recording method characterized by the following:

2. 2. The ink jet recording method according to claim 1, further comprising, after the air blowing step, a heating step of heating the recording medium to a temperature higher than that of the air blowing step to dry the recording medium.

3. The ink jet recording method according to claim 1, wherein air is blown onto the recording medium from the upstream side in the transport direction of the recording medium.

4. The ink jet recording method according to claim 1, wherein an air current having a temperature of 25° C. or higher and 60° C. or lower is blown onto the recording medium.

5. 2. The ink jet recording method according to claim 1, wherein an air current of 1.0 m / s or more and 10.0 m / s or less is blown onto the recording medium.

6. 2. The inkjet recording method according to claim 1, wherein the viscosity (Pa s) of a first mixture obtained by mixing 100 parts by mass of the aqueous ink and 7 parts by mass of the first reaction liquid is 2.0 times or more the viscosity (Pa s) of a second mixture obtained by mixing 100 parts by mass of the ink and 7 parts by mass of the second reaction liquid.

7. 7. The ink jet recording method according to claim 1, wherein the resin particles have a volume-based cumulative 50% particle diameter of 180 nm or less.

8. An inkjet recording apparatus for use in an inkjet recording method in which an aqueous ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink, are ejected from an inkjet recording head and applied to a recording medium to record an image, a blowing means for blowing air onto the recording medium to reduce the liquid component, The aqueous reaction liquid is a first reaction solution, and a second reaction liquid having a lower reactivity with the aqueous ink than the first reaction liquid; Including, The image is a low-gloss portion formed by applying the first reaction liquid and the water-based ink; a high-gloss portion formed by applying the second reaction liquid and the water-based ink; and Including, The recording medium is １／２ Water absorption up to 10 mL / m ２ An inkjet recording apparatus characterized by the following:

9. A set of an aqueous ink and an aqueous reaction liquid used in an inkjet recording method, in which an aqueous ink containing a pigment, resin particles, and a water-soluble organic solvent, and an aqueous reaction liquid that reacts with the aqueous ink are ejected from an inkjet recording head and applied to a recording medium to record an image, the inkjet recording method includes a blowing step of blowing air onto the recording medium to reduce a liquid component, The aqueous reaction liquid is a first reaction solution, and a second reaction liquid having a lower reactivity with the aqueous ink than the first reaction liquid; The image is a low-gloss portion formed by applying the first reaction liquid and the water-based ink; a high-gloss portion formed by applying the second reaction liquid and the water-based ink; and Including, The recording medium is １／２ Water absorption up to 10 mL / m ２ A set of an aqueous ink and an aqueous reaction liquid, characterized in that:

Images