Inkjet recording method and inkjet recording apparatus

Abstract

To provide an inkjet recording method which has excellent discharge stability and can record a fluorescent image excellent in color development and scratch resistance.SOLUTION: There is provided an inkjet recording method which comprises: a recording step of ejecting an aqueous ink from a recording head of an inkjet system to apply the aqueous ink to a recording medium; and a heating step of heating the recording medium to which the aqueous ink is applied at a temperature TH(°C). The aqueous ink contains first resin articles and second resin particles, the first resin particles are dyed by at least one fluorescent dye selected from the group consisting of a basic dye, a disperse dye and an oil-soluble dye and contains a cyano group-containing unit, the second resin particles do not include a color material, the temperature TH(°C) is lower than the glass transition temperature Tg1(°C) of the first resin particles and higher than the glass transition temperature Tg2(°C) of the second resin particles.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus used therefor.

Background Art

[0002] In the printing industry, an expansion of the expressible color gamut is demanded. Examples of color gamut standards include PANTONE certification (X-rite), Japan Color certification (Japan Printing Machinery Manufacturers Association), DIC Color Guide certification (DIC), Kaleido certification (Toyobo Ink), and the like. In recent years, for color gamut expansion, inkjet recording apparatuses that employ special inks other than the basic colors of cyan, magenta, and yellow, and high-brightness special color inks have come to be used.

[0003] Another one of the other needs in the printing industry is the production of recorded matter with a vivid color tone that attracts people's attention. For example, posters, POPs, and other posted materials, and the packaging of food and beverage products are required to be recorded in vivid colors in order to attract customers' attention. And it can be said that fluorescent colors are effective in meeting such needs.

[0004] Currently, offset printing is the mainstream method for recording fluorescent color images. However, when recording a fluorescent color image by single-pass offset printing, it is difficult to obtain vivid color development, so it has been common to perform double-pass or more overprinting. Therefore, the method of recording a fluorescent color image with excellent color development by overprinting has problems in terms of productivity and cost.

[0005] Also, in the case of digital recording using an electrophotographic method, it is possible to record a fluorescent color image with high color development using liquid toner. However, since the electrophotographic method has restrictions on the recording medium, for example, it is difficult to apply it to textile recording, expand it to large sizes, and apply it to thick materials.

[0006] In contrast, digital recording using an inkjet method can be applied to various recording media by taking advantage of the fact that the recording head that ejects ink does not come into contact with the recording media (non-contact). However, since ink is ejected from micron-order minute nozzles by applying mechanical energy or thermal energy, it is easily subject to restrictions on the physical properties of the ink such as viscosity. In particular, many of the materials that affect the performance of ink, such as colorants and resins, are solids, and in order to add these materials to the ink, they need to be dissolved or dispersed in a liquid medium such as water or an organic solvent. Therefore, there are restrictions on the amount added to the ink. The same applies to fluorescent colorants such as fluorescent dyes. Even if an attempt is made to add a sufficient amount of fluorescent colorant to the ink in order to record an image with excellent color development, restrictions will occur in terms of the physical properties of the ink.

[0007] In addition, posters, POPs, and other posted materials recorded using a fluorescent material are required to have scratch resistance that can withstand the friction between the recording media that occurs during recording and external friction that occurs when installed outdoors or the like. However, ink for inkjet contains a large amount of liquid components such as water and water-soluble organic solvents. When attempting to record an image with excellent scratch resistance using ink for inkjet, restrictions are likely to occur on the type of water-soluble organic solvent and the content of the liquid components.

[0008] In order to solve these problems, for example, a recording method using an ink containing an organic fluorescent pigment containing a fluorescent dye and a resin has been proposed (Patent Document 1). In addition, a printing method using an ink containing particles of a thermoplastic resin containing a dye has been proposed (Patent Document 2).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

[0010] However, it has been found that even with the methods proposed in Patent Documents 1 and 2, it is difficult to stably record fluorescent images that have both good color development and scratch resistance.

[0011] Therefore, an object of the present invention is to provide an inkjet recording method that is capable of recording fluorescent images with excellent ejection stability, color development, and scratch resistance. Another object of the present invention is to provide an inkjet recording apparatus for use in this inkjet recording method. [Means for solving the problem]

[0012] In other words, according to the present invention, the recording step involves ejecting aqueous ink from an inkjet recording head and applying it to a recording medium, and then heating the recording medium to which the aqueous ink has been applied at a temperature T H An inkjet recording method comprising a heating step of heating at (°C), wherein the aqueous ink contains first resin particles and second resin particles, the first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes and oil-soluble dyes and contain cyano group-containing units, and the second resin particles do not contain colorants, and the temperature T H An inkjet recording method is provided, characterized in that (°C) is lower than the glass transition temperature Tg1 (°C) of the first resin particle and higher than the glass transition temperature Tg2 (°C) of the second resin particle. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an inkjet recording method that can record fluorescent images with excellent ejection stability, color development, and scratch resistance. Furthermore, according to the present invention, it is possible to provide an inkjet recording apparatus for use in this inkjet recording method. [Brief explanation of the drawing]

[0014] [Figure 1] This figure schematically shows one embodiment of the inkjet recording apparatus of the present invention, where (a) is a perspective view of the main part of the inkjet recording apparatus and (b) is a perspective view of the head cartridge. [Figure 2] This is a schematic cross-sectional view showing an example of a heating device. [Modes for carrying out the invention]

[0015] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when a compound is a salt, the salt exists in the ink dissociated into ions, but for convenience, it will be expressed as "contains a salt." Also, water-based ink for inkjet applications may be simply referred to as "ink." Unless otherwise specified, physical properties are values ​​at room temperature (25°C). In the present invention, the "unit" constituting the resin means a repeating unit derived from one monomer. When "(meth)acrylic acid," "(meth)acrylate," and "(meth)acryloyl" are written, they refer to "acrylic acid, methacrylic acid," "acrylate, methacrylate," and "acryloyl, methacryloyl," respectively.

[0016] The inventors of this invention have investigated an inkjet recording method using water-based ink that can record fluorescent images with excellent ejection stability, color development, and scratch resistance. Regarding the color development of the image, the focus of the investigation was on expanding the color gamut in the high-brightness region, which is difficult to express with basic colors. To expand the color gamut in the high-brightness region, it is preferable to use a fluorescent dye as a colorant. In order to add a fluorescent dye as a colorant to the ink, it is essential to dye the fluorescent dye onto resin particles. When the fluorescent dye is dyed onto resin particles, the fluorescent dye is fixed to the resin particles, so it is possible to suppress the decrease in image brightness due to density quenching, which is characteristic of fluorescent materials, and to improve the water resistance of the image.

[0017] Common methods for dyeing resin particles with fluorescent dyes include (i) an addition-condensation mass resin pulverization method, in which a mass of resin is condensed and dyed, and then pulverized to obtain particles; and (ii) a method in which resin particles are produced by emulsion polymerization in an aqueous system and then dyed. Resin particles obtained by method (i) are on the order of microns in size and have low water dispersibility, making them difficult to use as inks for inkjet recording methods. On the other hand, resin particles obtained by method (ii) are applicable to aqueous systems and their size can be controlled to the nano-order, making them excellent for inkjet applications.

[0018] To record images with excellent color development using ink containing resin particles dyed with fluorescent dyes, it is important to use resin particles that have been dyed by strong interactions with the fluorescent dyes. Therefore, cyano group-containing units are incorporated into the resin that forms the resin particles. Fluorescent dyes, such as oil-soluble dyes and disperse dyes, dye the resin particles through dipole interactions. Specifically, the dipole interactions between the highly polar parts of the oil-soluble dye or disperse dye molecule (such as nitrogen, sulfur, and oxygen atoms) and the cyano groups in the resin particle molecule allow the oil-soluble dye or disperse dye to stably dye the resin particles. Furthermore, positively charged fluorescent dyes, such as basic dyes, dye resin particles formed from resin containing cyano group-containing units through electrostatic interactions with negatively polarized cyano groups. Thus, by using fluorescent dyes such as basic dyes, disperse dyes, and oil-soluble dyes, resin particles containing cyano group-containing units can be dyed through strong interactions. And by using ink containing resin particles dyed through such strong interactions, images with excellent color development can be recorded.

[0019] Furthermore, we considered incorporating a heating process to heat the recorded image, expecting that the resin particles (first resin particles) dyed with fluorescent dye, which are attached to the recording medium, would fuse together upon heating, forming a film on the image and improving scratch resistance. However, the heating temperature T H When (°C) is lower than the glass transition temperature Tg1(°C) of the first resin particle, and T HIn any case where T(℃) is higher than Tg1(℃), it was difficult to achieve the desired abrasion resistance. T H When T(℃) was lower than Tg1(℃), the molecular chains of the resin constituting the first resin particles were in a state where they did not undergo micro-Brownian motion, that is, a glassy state. Therefore, it is considered that the first resin particles could not fuse. Also, T H When T(℃) was higher than Tg1(℃), the molecular chains of the resin constituting the first resin particles were in a state of micro-Brownian motion, that is, a rubbery state. Therefore, it is considered that the first resin particles fused. However, since the formed film was smooth, the contact area with the abraded material increased, and it is considered that the film was easily scraped off.

[0020] From the above results, it was found that in order to improve the abrasion resistance of the image, it is necessary to form convex portions on the film so that the contact area with the abraded material becomes small. As a method of forming convex portions on the film, second resin particles not dyed with the fluorescent dye are further added to the ink, and T H It was found effective to set T(℃) lower than Tg1(℃) and higher than the glass transition temperature Tg2(℃) of the second resin particles. The mechanism by which convex portions are formed on the film is presumed as follows. T H When T(℃) is higher than Tg2(℃), the molecular chains of the resin constituting the second resin particles become rubbery, and the second resin particles fuse to form a film. On the other hand, since the molecular chains of the resin constituting the first resin particles are in a glassy state, the first resin particles maintain their particle shape. Therefore, it is presumed that convex portions derived from the first resin particles are formed on the surface of the film formed by the second resin particles.

[0021] T HIf the temperature (°C) is higher than either Tg1(°C) or Tg2(°C), both the molecular chains of the resin constituting the first resin particle and the molecular chains of the resin constituting the second resin particle become rubbery. As a result, the molecular chains of the resin constituting each particle become entangled, and the first and second resin particles fuse together to form a film. However, because no protrusions are formed on the film, the abrasion resistance decreases. In addition, due to the entanglement of the molecular chains of the resin constituting the first resin particle and the molecular chains of the resin constituting the second resin particle, some of the fluorescent dye that was coloring the first resin particle migrates to the second resin particle. Consequently, if the second resin particle does not contain cyano group-containing units, the color development of the image decreases.

[0022] <Inkjet recording method and inkjet recording device> The present invention provides an inkjet recording method comprising a recording step of ejecting aqueous ink from an inkjet recording head and applying it to a recording medium, and a recording of the recording medium to which the aqueous ink has been applied at a temperature T H The process includes a heating step of heating at (°C). The water-based ink contains first resin particles and second resin particles. The first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes, and also contain cyano group-containing units. The second resin particles do not contain colorants. H (°C) is lower than the glass transition temperature Tg1(°C) of the first resin particle and higher than the glass transition temperature Tg2(°C) of the second resin particle.

[0023] Furthermore, the inkjet recording apparatus of the present invention comprises an aqueous ink, an inkjet recording head that ejects the aqueous ink and applies it to a recording medium, and a recording medium to which the aqueous ink has been applied at a temperature T H The device includes a heating means that heats to (°C). Details of the inkjet recording apparatus that can be used in the inkjet recording method of the present invention will be described below with reference to the drawings.

[0024] Figure 1 is a schematic diagram showing one embodiment of the inkjet recording apparatus of the present invention, where (a) is a perspective view of the main part of the inkjet recording apparatus and (b) is a perspective view of the head cartridge. The inkjet recording apparatus is provided with a transport means (not shown) for transporting the recording medium 32 and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 comprises recording heads 38 and 40 and is configured to hold an ink cartridge 42. While the head cartridge 36 is transported along the carriage shaft 34 in the main scanning direction, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, the recording medium 32 is transported in the sub-scanning direction by the transport means (not shown), and an image is recorded on the recording medium 32.

[0025] Methods for ejecting water-based ink from the recording head include methods that impart mechanical energy to the ink and methods that impart thermal energy to the ink. Among these, it is preferable to employ a method that imparts thermal energy to the ink to eject it.

[0026] Temperature T of the water-based ink applied to the recording medium I (°C) is preferably lower than the glass transition temperature Tg2(°C) of the second resin particle. I If Tg2(°C) is above Tg2(°C), the second resin particles may fuse together near the ejection port of the recording head, causing clogging and potentially slightly reducing ejection stability. I The difference in (°C) is preferably greater than 0°C and 50°C or less, more preferably between 1°C and 50°C, and particularly preferably between 1°C and 30°C.

[0027] The inkjet recording device applies the aqueous ink to the recording medium at a temperature T I It is preferable to have means to control (°C). IMeans for controlling the temperature (°C) include, for example, an ink temperature regulating heater positioned to contact the recording head, and an ink ejection heater. To control (heat or warm) the ink temperature using the ink ejection heater, for example, a current that does not cause ink ejection can be repeatedly applied. The ink temperature can be read, for example, by a temperature sensor installed on the recording head. Water-based ink temperature T I The temperature (°C) is preferably between 30°C and 80°C, and more preferably between 40°C and 60°C.

[0028] Heating temperature T of a recording medium coated with water-based ink H It is preferable that (°C) is 10°C or more higher than the glass transition temperature Tg2(°C) of the second resin particle. H If the temperature difference between (°C) and Tg2(°C) is less than 10°C, the second resin particles may not fuse sufficiently, and the image's scratch resistance may be slightly reduced. H The difference between (°C) and Tg2(°C) is preferably 70°C or less, and more preferably 30°C or less. Also, the heating temperature T of the recording medium coated with water-based ink. H The temperature (°C) is preferably 10°C or more lower than the glass transition temperature Tg1 (°C) of the first resin particle. H If the temperature difference between (°C) and Tg1(°C) is less than 10°C, some of the first resin particles may fuse together, reducing the protrusions on the film and slightly decreasing the scratch resistance of the image. H The difference in (°C) is preferably 70°C or less, and more preferably 40°C or less.

[0029] Figure 2 shows a recording medium coated with water-based ink at temperature T HThis is a schematic cross-sectional view showing an example of a heating device for heating at (°C). The heating device shown in Figure 2 is a film heating type heating and pressure fixing device. In a film heating type heating device, a low heat capacity heating element can be used, which is a linear heating element with a low heat capacity made into a thin film. This enables power saving and shortening of wait time (quick start), and also suppresses the temperature rise of parts of the device other than the heating device. In addition, in a film heating type heating device, the fixing point and the separation point can be set separately, so offset can be effectively suppressed. Furthermore, various problems of other types of heating devices can be reduced.

[0030] As shown in Figure 2, the heating device includes a heating element 56, such as a ceramic heater, fixedly supported on a support. A fixing film 51, such as a heat-resistant film, is brought into close contact with the heating element 56 by a pressure rotating body such as a pressure roller 52 and is slidably transported. A pressure contact nip section (fixing nip section) N is formed between the heating element 56 and the pressure roller 52 via the fixing film 51. A recording object P to which an image is to be fixed is introduced between the fixing film 51 and the pressure roller 52 that form this pressure contact nip section N. The recording object P is then transported while being held by the fixing film 51, and the heat from the heating element 56 is applied to the surface of the recording object P via the fixing film 51 at the pressure contact nip section N, thereby heating it. After passing through the pressure contact nip section N, the recording object P separates from the surface of the fixing film 51 and is transported to the left in Figure 2.

[0031] The heating element 56 of the heating device shown in Figure 2 is a linear heating element composed of: (a) a heat-resistant, insulating, and highly thermally conductive substrate 57 with an elongated shape whose longitudinal direction is perpendicular to the transport direction a of the fixing film 51 and the recording material P; (b) a heating resistor 55 provided along the longitudinal direction of the substrate 57 at the center of the short side on the surface side of the substrate 57; (c) power supply electrodes (not shown) provided at both ends of the heating resistor 55 in the longitudinal direction; (d) a heat-resistant overcoat layer 58 that protects the surface of the heating element 56; and (e) a temperature sensing element 54 such as a thermistor provided on the back side of the substrate 57 to detect the temperature of the heating element 56.

[0032] In the heating device shown in Figure 2, the heating element 56 is fixed by adhesive bonding to a heater support (not shown) that has rigidity and heat insulation properties, with the side on which the heat-generating resistor 55 is provided facing downwards (towards the recording medium). The heating element 56 heats up as the entire heat-generating resistor 55 heats up due to power supplied from electrodes 60 provided at both ends of the heat-generating resistor 55. The heating state of the heating element 56 is detected by a temperature sensing element 54 such as a thermistor and fed back to a temperature control circuit (not shown), which controls the power supply to the heat-generating resistor 55 so that the heating element 56 is maintained at a predetermined temperature. In other words, when the recording medium is heated, the power supply to the heat-generating resistor 55 is controlled so that the detection output of the temperature sensing element 54 remains constant. In addition to a ceramic heater, a heating device utilizing an alternating magnetic field can also be used as the heating element 56.

[0033] The fixing film 51 shown in Figure 2 is in the shape of an endless belt. The fixing film 51 can be rotated and conveyed by the frictional force between the drive roller and the inner surface of the fixing film 51. In addition to the above, other methods for conveying the fixing film 51 include using the pressure roller 52 as the drive roller, or using a drive roller other than the pressure roller 52 that is in contact with the outer surface of the fixing film 51 to rotate and convey it. Alternatively, the fixing film 51 may be made into a long roll and conveyed by unwinding it.

[0034] A release layer is provided on the surface layer of the fixing film 51. The release layer can be formed from a water-repellent material such as a mixture of fluororubber and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The pressure roller 52 is constructed by laminating a metal core 52a, an elastic layer 52b, a fluororubber layer 52c, and a fluororesin layer 52d in that order from the inside. The pressure roller 52 is pressed against the surface of the heating element 56 via the fixing film 51 with a predetermined pressing force by bearing means and biasing means (not shown). When the pressure roller 52 is used as a drive roller for the fixing film 51, rotational force is transmitted from the drive means (not shown) to drive the pressure roller 52 to rotate counterclockwise.

[0035] In the inkjet recording method of the present invention, the recording medium is heated to a temperature T H The image may be recorded by ejecting ink from the recording head while heating at (°C), or the recording medium may be heated to a temperature of T after the image has been recorded by ejecting ink from the recording head. H The recording medium may be heated to (°C). H When recording an image while heating (°C), the recording medium should be heated to a temperature of T H This also includes cases where the recording medium is preheated to (°C) before recording the image. That is, the recording medium is heated to a temperature of T at or near the location where ink is applied to the recording medium, preferably at least downstream of the recording head in the transport direction. H The process only needs to include a step of heating at (°C).

[0036] Methods for heating a recording medium include heating the surface of the recording medium (the image recording surface); heating the back surface of the recording medium (the surface opposite to the image recording surface); and combining these methods. Furthermore, the heating element may or may not be in contact with the recording medium. Specific methods for heating a recording medium include the following: (i) A method in which a nickel alloy heater is placed at the bottom of a platen made of an aluminum alloy that is resistant to thermal deformation and manufactured by die casting, the platen is heated by the heater, and the surface of the recording medium is heated by the platen. (ii) A method of heating the back surface of the recording medium with the platen described above. (iii) A method for heating the surface of a recording medium using a sheathed heater or halogen heater and a heat reflector. (iv) A method of heating the recording medium by applying hot air with a hair dryer or the like. (v) A method of heating a recording medium by pressing a heating plate against it. (vi) A method of heating a recording medium by passing it between a pair of rollers, a pair of belts, or a heating and pressurizing device comprising a belt positioned on the recording surface side of the recording medium and a holding roller positioned on the opposite side of the recording surface.

[0037] temperature T HSpecific methods for measuring and controlling (°C) include the following: Based on the surface temperature of the recording medium measured by a sensor placed upstream of the heating element, the temperature of the heating element is changed to control the temperature T H There is a method to control the temperature (°C). Alternatively, the surface temperature of the recording medium (or image) measured by a sensor placed downstream of the heating element can be fed back to the control means to change the temperature of the heating element, thereby controlling the temperature T H There is a way to control the temperature (°C). H The temperature (°C) can be measured using a non-contact radiation thermometer or similar device placed at an appropriate location corresponding to the heating point. The heating temperature T of a recording medium coated with water-based ink. H The temperature (°C) is preferably 40°C to 120°C, more preferably 60°C to 120°C, and particularly preferably 65°C to 110°C.

[0038] Examples of recording media 32 include the following: • Recording media with a coated layer, such as glossy paper, semi-glossy paper, matte paper, and art paper (inkjet-specific paper). • Recording media (printing paper) used in offset printing, such as art paper and coated paper. A recording medium in which a resin material (film or sheet) is bonded to a substrate such as paper. • Resin media (resin sheets, resin films, synthetic paper) that do not have an absorbent layer (receiving layer). Recording media without a coating layer, such as plain paper, and fabrics are not desirable because their large pore size allows the first resin particles to easily penetrate the interior, which can reduce the color reproduction of the image.

[0039] (Water-based ink) The inkjet recording method of the present invention uses an aqueous ink containing first resin particles and second resin particles. The components and physical properties of the ink and methods for measuring them will be described in detail below.

[0040] [Resin particles] In this specification, "resin particles" means resin that is dispersed in an aqueous medium and can exist in the aqueous medium in a state having particle size. Therefore, the resin particles exist in a dispersed state in the ink, that is, in the state of a resin emulsion.

[0041] Whether a resin is "resin particles" or not can be determined by the following method. First, a liquid containing resin (resin solids content: 10% by mass) is prepared, neutralized with an alkali (such as sodium hydroxide or potassium hydroxide) with an acid value equivalent to the resin's value. Next, the prepared liquid is diluted 10 times (by volume) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if particles with a defined particle size are measured, the resin can be determined to be "resin particles". The measurement conditions in this case can be, for example, SetZero: 30 seconds, Number of measurements: 3, Measurement time: 180 seconds, Shape: Spherical, Refractive index: 1.59.

[0042] 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. Measuring particle size using neutralized resin is to confirm that particles are still formed even when the resin is sufficiently neutralized and in a state where particle formation is less likely. Even under such conditions, resin with a granular shape exists in a granular state even in water-based ink.

[0043] [1] First resin particle The first resin particles are the main colorants of the ink. The ink may also contain colorants such as pigments and dyes (including dyes that do not exhibit fluorescence, basic dyes, disperse dyes, and fluorescent dyes other than oil-soluble dyes), but it is usually not necessary to include such colorants. It should be noted that even if organic pigments are used as the colorants of the ink instead of the first resin particles, it is not possible to obtain an image scratch resistance level comparable to that obtained when the first resin particles are used. This is because, when organic pigments are used as colorants, during the process of the ink fixing to the recording medium, the organic pigments have a high specific gravity and tend to sink downwards in the direction of gravity of the ink dots compared to other components such as the second resin particles. As a result, the convex portions of the height necessary to obtain scratch resistance are not formed on the film.

[0044] The first resin particles contain cyano group-containing units. The monomers that become cyano group-containing units through polymerization are preferably those having one polymerizable functional group, such as an ethylenically unsaturated bond, within the molecule. Specifically, examples include acrylonitrile, methacrylonitrile, chloroacrylonitrile, and 2-cyanoethyl (meth)acrylate. The monomers that become cyano group-containing units through polymerization are preferably those that do not have anionic or aromatic groups, and have a molecular weight of 300 or less, and more preferably a molecular weight of 200 or less. Among these, acrylonitrile and methacrylonitrile are particularly preferred because they exhibit good reactivity during polymerization and the resulting first resin particles have excellent stability.

[0045] The proportion (mass%) of cyano group-containing units in the first resin particles is preferably 15.0% by mass or more, more preferably 15.0% by mass or more and 60.0% by mass or less, and particularly preferably 15.0% by mass or more and 52.0% by mass or less. If the proportion of cyano group-containing units in the first resin particles is too low, the interaction between the cyano groups of the first resin particles and the second resin particles tends to weaken. As a result, the first resin particles may easily detach from the film due to abrasion, and the scratch resistance of the image may be slightly reduced.

[0046] The first resin particle is preferably a resin particle having a so-called core-shell structure, having a core portion and a shell portion covering the core portion. Furthermore, it is preferable to use a first resin particle having a shell portion formed of a resin containing anionic group-containing units. By adopting a core-shell structure, it is easy to control the amount of anionic groups present in the shell portion. This can increase the hydrophilicity of the first resin particle, easily resolve clogging of the discharge port, and improve adhesion recovery. The anionic group-containing units may be included in the resin forming the core portion.

[0047] In an anionic group-containing unit, the anionic group is preferably one that has one polymerizable functional group, such as an ethylenically unsaturated bond, within the molecule. Specifically, examples include carboxylic acid groups, phenolic hydroxyl groups, and phosphate ester groups. Among these, carboxylic acid groups are preferred because they provide good stability for the first resin particles in the ink. Examples of monomers that become anionic group-containing units through polymerization include (meth)acrylic acid, p-vinylbenzoic acid, 4-vinylphenol, β-carboxyethyl (meth)acrylate, phosphoric acid (2-hydroxyethyl methacrylate) ester, 2-hydroxyethyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate. Among monomers that become anionic group-containing units through polymerization, those that do not have aromatic groups or cyano groups, and those with a molecular weight of 300 or less are preferred, and those with a molecular weight of 200 or less are even more preferred. Among these, (meth)acrylic acid is particularly preferred. Furthermore, it is preferable that the anionic group in the anionic group-containing unit is only a carboxylic acid group. The anionic group may be in either an acidic or salt form, and if it is in the salt form, it may be in either a partially dissociated or fully dissociated state. When the anionic group is in the salt form, examples of cations that become counterions include alkali metal cations, ammonium, and organic ammonium.

[0048] The first resin particles may also contain aromatic group-containing units and units derived from crosslinking agents, in addition to the cyano group-containing units and anionic group-containing units. Preferred monomers that become aromatic group-containing units through polymerization are those having one polymerizable functional group, such as an ethylenically unsaturated bond, within the molecule. Specifically, examples include styrene, vinyltoluene, p-fluorostyrene, p-chlorostyrene, α-methylstyrene, 2-vinylnaphthalene, 9-vinylanthracene, 9-vinylcarbazole, phenyl(meth)acrylate, benzyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, 2,4-diamino-6-((meth)acryloyloxy)ethyl-1,3,5-triazine, 2-naphthyl(meth)acrylate, 9-anthryl(meth)acrylate, and (1-pyrenyl)methyl(meth)acrylate. The monomers that become aromatic group-containing units through polymerization are preferably those that do not have anionic or cyano groups, and have a molecular weight of 300 or less, and more preferably those with a molecular weight of 200 or less. Among these, styrene and its derivatives are even more preferred, and styrene and vinyltoluene are particularly preferred, because they exhibit good reactivity during polymerization and the resulting first resin particles have excellent stability.

[0049] As the crosslinking agent that constitutes the unit derived from the crosslinking agent, at least one type of crosslinking agent may be used, but it is preferable to use two or more types of crosslinking agents. When the crosslinking agent contains two or more types of crosslinking agents, it is preferable that at least one of the crosslinking agents is a crosslinking agent having a glycidyl group. A crosslinking agent having a glycidyl group crosslinks by reacting with anionic groups such as carboxylic acid groups. This suppresses an excessive increase in the hydrophilicity of the first resin particles and improves the ink's adhesion recovery. Furthermore, by using two or more types of crosslinking agents, a dense crosslinked structure can be formed that more efficiently suppresses an excessive increase in the hydrophilicity of the first resin particles.

[0050] Examples of crosslinking agents that become units derived from the crosslinking agent through polymerization include compounds having two or more polymerizable functional groups, such as ethylenically unsaturated bonds, within their molecules. Examples of such crosslinking agents include diene compounds, difunctional (meth)acrylates, trifunctional (meth)acrylates, tetrafunctional (meth)acrylates, and divinylbenzene.

[0051] As a crosslinking agent, one with a molecular weight of over 200 is preferred, one with a molecular weight of over 300 is more preferred, and one with a molecular weight of 400 or more is particularly preferred. Furthermore, as a crosslinking agent, a compound having two ethylenically unsaturated bonds in its molecule is preferred. By using a compound having two ethylenically unsaturated bonds in its molecule as a crosslinking agent, aggregation of the first resin particles caused by excessive crosslinking is suppressed, and first resin particles with a more uniform particle size can be obtained. Among compounds having two ethylenically unsaturated bonds in their molecule, difunctional (meth)acrylates such as divinylbenzene and ethylene glycol di(meth)acrylate are even more preferred.

[0052] Examples of crosslinking agents having a glycidyl group include (mono, di, poly)ethylene glycol diglycidyl ether, (mono, di, poly)propylene glycol diglycidyl ether, (mono, di, poly)glycerol polyglycidyl ether, sorbitol polyethylene glycol diglycidyl ether, pentaerythritol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and neopentyl glycol diglycidyl ether. Among these, ethylene glycol diglycidyl ether is preferred because it can form a high-density crosslinked structure and has a significant effect in suppressing excessive hydrophilicity of the first resin particles.

[0053] A surfactant can be used when manufacturing the first resin particles. Manufacturing the first resin particles in the presence of a surfactant is preferable because it tends to stabilize the particle size and shape of the resulting first resin particles. However, non-reactive surfactants may easily peel off from the first resin particles. If the surfactant peels off in the ink, it may affect the physical properties of the ink, potentially reducing ejection stability. For this reason, a reactive surfactant is preferred as the surfactant used when manufacturing the first resin particles.

[0054] As the reactive surfactant, it is preferable to use a compound in which polymerizable functional groups such as (meth)acryloyl groups, maleyl groups, vinyl groups, and allyl groups are bonded to the interior or terminal of a molecule composed of a hydrophilic part and a hydrophobic part. Examples of the hydrophilic part include polyoxyalkylene chains such as ethylene oxide chains and propylene oxide chains. Examples of the hydrophobic part include alkyl, aryl, and combinations thereof. The hydrophilic and hydrophobic parts may be bonded via linking groups such as ether groups. As the reactive surfactant, a molecular weight of more than 200 is preferred, a molecular weight of more than 300 is more preferred, and a molecular weight of 400 or more is particularly preferred.

[0055] The first resin particles may further contain units other than those described above, as long as the effects of the present invention are not impaired. Preferably, the units other than those described above have one polymerizable functional group in their molecule, and specifically, units derived from ethylenically unsaturated monomers can be mentioned.

[0056] Examples of ethylenically unsaturated monomers include alkenes such as ethylene and propylene; alkyl(meth)acrylates such as methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl(meth)acrylate, and hexadecyl(meth)acrylate; monocyclic(meth)acrylates such as cyclopropyl(meth)acrylate, cyclohexyl(meth)acrylate, cyclooctyl(meth)acrylate, and cyclodecyl(meth)acrylate; bicyclic(meth)acrylates such as isobornyl(meth)acrylate and norbornyl(meth)acrylate; and adamantyl(meth)acrylate. Examples include tricyclic (meth)acrylates such as cyclopentanyl (meth)acrylate and dicyclopentenyloxyethyl (meth)acrylate; nonionic hydrophilic group-containing (meth)acrylates such as methoxy(mono, di, tri, poly)ethylene glycol (meth)acrylate; and aromatic group-containing (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2,4-diamino-6-((meth)acryloyloxy)ethyl-1,3,5-triazine, 2-naphthyl (meth)acrylate, 9-anthryl (meth)acrylate, and (1-pyrenyl)methyl (meth)acrylate. Preferably, ethylenically unsaturated monomers lack anionic groups, cyano groups, or aromatic groups, and have a molecular weight of 300 or less; more preferably have a molecular weight of 200 or less. Among these, alkenes with 1 to 22 carbon atoms and alkyl (meth)acrylates with 1 to 22 carbon atoms in the alkyl group are preferred. Furthermore, alkyl (meth)acrylates with 1 to 12 carbon atoms in the alkyl group are even more preferred, and methyl (meth)acrylate and ethyl (meth)acrylate are particularly preferred, as they allow for easy adjustment of the physical properties of the resin particles and enable the production of resin particles with excellent polymerization stability.

[0057] The glass transition temperature Tg1 (°C) of the first resin particle is preferably 50°C to 160°C, and more preferably 60°C to 120°C. The glass transition temperature of the resin particle was measured using a differential scanning calorimetry instrument with dried resin particles as the measurement sample.

[0058] The cumulative 50% particle size (D50) of the volume-based particle size distribution of the first resin particles is preferably 50 nm to 250 nm, and more preferably 100 nm to 200 nm. The cumulative 50% particle size (D50) of the volume-based particle size distribution can be measured by the same method as the method for determining whether or not a particle is a resin particle as described above. The content (mass%) of the first resin particles in the ink is preferably 1.0% by mass to 10.0% by mass, based on the total mass of the ink.

[0059] Specific gravity of the first resin particle (g / cm³) 3 ) is 1.20 g / cm³ 3 The following is preferable: Specific gravity of the first resin particles (g / cm³) 3 ) is 1.20 g / cm³ 3 If the specific gravity is too high, the first resin particles tend to sink downwards in the direction of gravity of the ink dots during the process of the ink fixing to the recording medium. As a result, the protrusions originating from the first resin particles formed on the film may not become sufficiently high, which may reduce the scratch resistance of the image. Specific gravity of the first resin particles (g / cm³) 3 ) is 1.00 g / cm³ 3 More than 1.20g / cm 3 Preferably, it is 1.10 g / cm³. 3 More than 1.20g / cm 3 It is even more preferable that the following is the case: Also, 1.05 g / cm³. 3 More than 1.20g / cm 3 The following is particularly preferable:

[0060] The first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes. In this specification, "fluorescent dye" refers to a dye that emits fluorescence when excited by ultraviolet or visible light. Whether or not a dye is a "fluorescent dye" can be determined, for example, by the following method: A sample obtained by dissolving the dye in a liquid capable of dissolving the dye is irradiated with ultraviolet light (ultraviolet light) of a slightly visible long wavelength (approximately 315-400 nm) using a black light or the like. If light of a different color from the ultraviolet light irradiated by the black light can be visually observed, the dye can be determined to be a "fluorescent dye" that exhibits fluorescence. A commercially available black light (for example, product name "SLUV-4" (manufactured by AS ONE), etc.) can be used.

[0061] The fluorescent dye in the first resin particles stained with the fluorescent dye can be analyzed, for example, according to the following procedure: Prepare a sample by dissolving the resin particles, which have been extracted from the ink according to a conventional method, in an organic solvent such as chloroform. Isolate the fluorescent dye from the prepared sample using HPLC (high-performance liquid chromatography). Analyze the isolated dye using common structural analysis techniques such as nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS).

[0062] Basic dyes are fluorescent compounds that have an amino group or imino group (which may form a salt) in their molecular structure. Examples of compounds with an amino group or imino group in their molecular structure include "dyes whose names in the Color Index include 'basic'." The Color Index is a database of colorants compiled by the British Dye and Color Society and others. Examples of dye skeletons include xanthenes, azines, azoles, thiazoles, azos, diarylmethanes, triarylmethanes, acridines, coumarins, and methines. Among these, compounds with xanthene or coumarin skeletons are preferred, and compounds with a xanthene skeleton are even more preferred.

[0063] Specific examples of fluorescent basic dyes, indicated by their CI numbers or common names, include CI Basic Red 1, 1:1, 2, 4, 8, 11, 12, 13; CI Basic Violet 1, 3, 10, 11, 11:1, 14; Rhodamine 19, 575; CI Basic Yellow 1, 2, 9, 13, 24, 37, 40, 96; CI Basic Blue 7; CI Basic Green 1; and CI Fluorescent Brightener 363. Among these, CI Basic Red 1, 1:1; CI Basic Violet 11, 11:1; and CI Basic Yellow 40 are preferred due to their excellent color development.

[0064] Disperse dyes are fluorescent compounds that have low or no water solubility. Examples of "disperse dyes" include "dyes whose names in the color index include 'disperse'." Examples of dye skeletons include azo, coumarin, and anthraquinone. Among these, compounds with a coumarin or anthraquinone skeleton are preferred, and compounds with a coumarin skeleton are even more preferred.

[0065] Specific examples of fluorescent disperse dyes, indicated by their CI numbers, include CI Disperse Yellow 82, 186; CI Disperse Red 58, 60; and CI Disperse Orange 11. Among these, CI Disperse Yellow 82 is preferred due to its excellent color development.

[0066] Oil-soluble dyes are fluorescent compounds that have low or no water solubility. Examples of "oil-soluble dyes" include "dyes whose names in the color index include 'solvent'." Examples of dye skeletons include coumarin, xanthene, azo, aminoketone, and anthraquinone. Among these, compounds with a coumarin or xanthene skeleton are preferred, and compounds with a coumarin skeleton are even more preferred.

[0067] Specific examples of fluorescent oil-soluble dyes, indicated by their CI numbers, include CI Solvent Yellow 7, 43, 44, 85, 98, 131, 160:1, 172, 196; CI Solvent Red 43, 44, 45, 49, 149; and CI Solvent Orange 5, 45, 63, 115. Among these, CI Solvent Yellow 160:1 and 196 are preferred due to their excellent color development.

[0068] Preferably, the fluorescent dye contains two or more types of fluorescent dyes. The presence of multiple fluorescent dyes in the resin particles inhibits the crystallization of the fluorescent dyes, allowing the fluorescent dyes to interact efficiently with the resin particles at the molecular level and achieve a stable dyed state.

[0069] The amount of fluorescent dye in the ink (by mass%) is preferably 0.1% by mass or more and 5.0% by mass or less, based on the total mass of the ink. The proportion of fluorescent dye in the first resin particles (by mass%) is preferably 1.0% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 8.0% by mass or less. If the proportion of fluorescent dye in the first resin particles is too low, the color reproduction (saturation) of the image may be slightly reduced. On the other hand, if the proportion of fluorescent dye in the first resin particles is too high, the color reproduction (brightness) of the image may be slightly reduced due to density quenching.

[0070] [2]Second resin particles The second resin particles are resin particles formed from resin and do not contain colorants. The second resin particles may be in any of the following forms: emulsified or dispersed resin particles with a surfactant, self-dispersing resin particles, or core-shell type resin particles. Preferably, the second resin particles contain at least one of cyano group-containing units and units derived from (meth)acrylic acid esters. If neither the cyano group-containing units nor the units derived from (meth)acrylic acid esters are contained in the second resin particles, the dipole interaction between the cyano groups of the first resin particles and the second resin particles becomes less effective. As a result, the first resin particles are not strongly immobilized on the film formed by the second resin particles, and the first resin particles are more likely to detach from the film by abrasion, which may reduce the scratch resistance of the image.

[0071] Examples of monomers that become cyano group-containing units through polymerization include those similar to the monomers that constitute the cyano group-containing units contained in the first resin particles mentioned above.

[0072] The monomers that polymerize to form units derived from (meth)acrylic acid esters are preferably those that have one polymerizable functional group, such as an ethylenically unsaturated bond, within the molecule. Specifically, alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and hexadecyl (meth)acrylate; monocyclic (meth)acrylates such as cyclopropyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, and cyclodecyl (meth)acrylate; bicyclic (meth)acrylates such as isobornyl (meth)acrylate and norbornyl (meth)acrylate; tricyclic (meth)acrylates such as adamantyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; and β-carboxyethyl Examples include anionic group-containing (meth)acrylates such as methyl(meth)acrylate, phosphate (2-hydroxyethyl methacrylate) ester, 2-hydroxyethyl(meth)acrylate, and 3-hydroxypropyl(meth)acrylate; nonionic hydrophilic group-containing (meth)acrylates such as methoxy(mono, di, tri, poly)ethylene glycol(meth)acrylate; and aromatic group-containing (meth)acrylates such as phenyl(meth)acrylate, benzyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, 2,4-diamino-6-((meth)acryloyloxy)ethyl-1,3,5-triazine, 2-naphthyl(meth)acrylate, 9-anthryl(meth)acrylate, and (1-pyrenyl)methyl(meth)acrylate.

[0073] The second resin particles may further contain units other than those described above, as long as the effects of the present invention are not impaired. Specifically, examples include other aromatic group-containing units, units derived from crosslinking agents, anionic group-containing units, and units derived from ethylenically unsaturated monomers. Monomers that become these units through polymerization include those similar to the monomers that constitute the units contained in the first resin particles described above.

[0074] The glass transition temperature Tg2 (°C) of the second resin particles is preferably 30°C to 110°C, and more preferably 40°C to 100°C. The cumulative 50% particle diameter (D50) of the volume-based particle size distribution of the second resin particles is preferably 30 nm to 240 nm, and more preferably 70 nm to 120 nm. The content (mass%) of the second resin particles in the ink is preferably 1.0% to 20.0% by mass, and more preferably 1.0% to 15.0% by mass, based on the total mass of the ink.

[0075] It is preferable that the cumulative 50% particle size (D50) of the volume-based particle size distribution of the second resin particles is smaller than the cumulative 50% particle size (D50) of the volume-based particle size distribution of the first resin particles. If the cumulative 50% particle size (D50) of the volume-based particle size distribution of the second resin particles is greater than or equal to the cumulative 50% particle size (D50) of the volume-based particle size distribution of the first resin particles, the first resin particles tend to become embedded in the film formed by the fusion of the second resin particles. As a result, it becomes difficult for protrusions to form on the film, and the scratch resistance of the image may be slightly reduced.

[0076] The content (mass%) of the second resin particles in the ink is preferably 0.3 to 3.0 times the mass ratio of the content (mass%) of the first resin particles. If the above mass ratio is less than 0.3, the protrusions originating from the first resin particles formed on the film may become too high. As a result, the first resin particles may easily detach due to abrasion, and the scratch resistance of the image may decrease. On the other hand, if the above mass ratio is greater than 3.0, the first resin particles tend to become embedded in the film formed by the fusion of the second resin particles. Therefore, it becomes difficult for protrusions to form on the film, and the scratch resistance of the image may decrease slightly.

[0077] Specific gravity of the second resin particle (g / cm³) 3 ) is 1.00 g / cm³ 3 More than 1.20g / cm 3 Preferably, it is 1.10 g / cm³. 3 More than 1.20g / cm 3 It is even more preferable that the following is the case: Also, 1.05 g / cm³. 3 More than 1.20g / cm 3 The following is particularly preferable. Also, the specific gravity of the second resin particles (g / cm³) 3 ) is the specific gravity (g / cm³) of the first resin particle. 3 It is preferable that the specific gravity of the second resin particle (g / cm³) is lower than the specified gravity. 3 ) is the specific gravity (g / cm³) of the first resin particles. 3 If the specific gravity is above this level, the first resin particles, which have a lower specific gravity, tend to float upward in the direction of gravity of the ink dots during the process of the ink settling onto the recording medium. As a result, the protrusions originating from the first resin particles formed on the film may become too high, making the first resin particles more likely to detach due to abrasion, which may reduce the scratch resistance of the image.

[0078] When the first resin particles contain cyano group-containing units, and the second resin particles contain at least one of the cyano group-containing units and units derived from (meth)acrylic acid esters, the scratch resistance of the recorded image is particularly improved. The mechanism for this is presumed to be as follows: When the molecular chains of the resin constituting the second resin particles become rubbery and the molecular chains spread out to surround the first resin particles, dipole interactions act between the cyano groups of the first resin particles and the cyano groups or ester groups of the second resin particles. As a result, the first resin particles are strongly immobilized on the film formed by the second resin particles, and the detachment of the first resin particles from the film due to scratching is suppressed.

[0079] [Method for manufacturing resin particles] Resin particles can be manufactured by conventionally known methods such as emulsion polymerization, miniemulsion polymerization, seed polymerization, and phase inversion emulsification. Methods for dyeing the first resin particles include polymerizing a monomer mixture containing a dissolved fluorescent dye to form resin particles; and adding the fluorescent dye to the resin particles and heating them. Among these, the method of adding the fluorescent dye to the resin particles and heating them is preferred because it can be applied to a wider variety of fluorescent dyes. It is preferable not to add dyeing aids (water-soluble resins, surfactants, etc.) during heating. Using a water-soluble resin as a dyeing aid may cause the resin to form a film that inhibits the redispersion of the resin particles, slightly reducing the ink's adhesion recovery. Furthermore, using a surfactant as a dyeing aid may affect the physical properties of the ink, slightly reducing the ink's discharge stability.

[0080] [Method for verifying resin particles] The composition of the resin particles can be verified according to the methods shown in (i) to (iii) below. The following describes a method for extracting, analyzing, and verifying resin particles from ink, but resin particles extracted from aqueous dispersions, etc., can be similarly analyzed and verified.

[0081] (i) Extraction of resin particles Density gradient centrifugation allows for the separation and extraction of resin particles from ink containing them. Within density gradient centrifugation, the density gradient sedimentation velocity method separates and extracts resin particles based on the difference in the sedimentation coefficients of the components. Furthermore, the density gradient sedimentation equilibrium method separates and extracts resin particles based on the difference in density of the components. This density gradient centrifugation method allows for the separation of first and second resin particles.

[0082] (ii) Confirmation and separation of the layered structure First, the resin particles are stained and immobilized with ruthenium tetroxide, and then embedded in epoxy resin for stable retention. Next, the resin particles embedded in the epoxy resin are cut with an ultramicrotome, and the cross-section is observed using a scanning transmission electron microscope (STEM). By observing the cross-section cut through the center of gravity of the resin particles, the layered structure of the resin particles can be confirmed. Using the resin particles embedded in epoxy resin as the analytical sample, STEM-EDX, which combines energy-dispersive X-ray spectroscopy (EDX), allows for quantitative analysis of the elements contained in the layers (core and shell) that make up the resin particles.

[0083] (iii) Analysis of the units (monomers) that make up each layer of resin The resin particles used as a sample for separating the resins of each layer may be in the form of a dispersion. Alternatively, the resin particles may be dried and formed into a film, which can then be used as the sample. After dissolving the resin particles to be used as a sample in an organic solvent, each layer is separated by gel permeation chromatography (GPC), and the resin constituting each layer is isolated. The isolated resin is then subjected to elemental analysis by combustion. Separately, the isolated resin is pretreated by acid decomposition (addition of hydrofluoric acid) or alkali fusion, and then the inorganic components are quantitatively analyzed by inductively coupled plasma atomic emission spectroscopy. By comparing the results of the elemental analysis and quantitative analysis of inorganic components with the results of the elemental quantitative analysis by STEM-EDX obtained in (ii) above, the layers of resin particles that constituted the isolated resin can be determined.

[0084] Furthermore, the separated resins are analyzed using nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption / ionization mass spectrometry (MALDI-MS). This allows us to determine the types and proportions of the units (monomers) and crosslinking components that make up the resin. In addition, by analyzing the separated resins using pyrolysis gas chromatography, it is possible to directly detect the monomers produced by depolymerization.

[0085] [Water-soluble resin] The ink may contain a water-soluble resin. The water-soluble resin is preferably an acrylic resin or a urethane resin, and more preferably an acrylic resin. The water-soluble resin preferably has aromatic group-containing units and anionic group-containing units. The water-soluble resin adsorbs onto the resin particles and assists in dispersion, thereby improving the ink discharge stability.

[0086] Furthermore, when the ink is stored for a long period of time, some of the fluorescent dyes adhering to the first resin particles migrate to the water-soluble resin through various interactions (electrostatic interactions, hydrophobic interactions, dipole interactions). When this phenomenon occurs, the amount of dye adhering to the resin particles decreases while the dye content in the ink remains constant. As a result, the density quenching that occurs between the dyes in the first resin particles is mitigated, further improving the color reproduction of the image.

[0087] The migration of dye to the water-soluble resin can be easily confirmed by the density gradient centrifugation method described above. In the case of ink that does not contain water-soluble resin, there is only one band of the first resin particles as the coloring component. In contrast, in the case of ink that contains water-soluble resin, there are two bands: one of the resin particles corresponding to the dye that has detached from the first resin particles, and another of the first resin particles as the coloring component.

[0088] As aromatic group-containing units and anionic group-containing units in water-soluble acrylic resins, the above-mentioned aromatic group-containing units and anionic group-containing units can be used. Water-soluble acrylic resins may further contain units other than aromatic group-containing units and anionic group-containing units (other units). Monomers constituting the other units include those having substituents such as alkoxy groups and hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate; 3-hydroxypropyl (meth)acrylate; methoxy(mono, di, tri, poly)ethylene glycol (meth)acrylate; alkenes such as ethylene and propylene; alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, and hexadecyl (meth)acrylate. Examples include monocyclic (meth)acrylates such as cyclopropyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclooctyl (meth)acrylate, and cyclodecyl (meth)acrylate; bicyclic (meth)acrylates such as isobornyl (meth)acrylate and norbornyl (meth)acrylate; and tricyclic (meth)acrylates such as adamantyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. The water-soluble acrylic resin may be a random copolymer, a block copolymer, or a graft copolymer.

[0089] As a water-soluble urethane resin, one can be obtained by reacting polyisocyanate with a component that reacts with it (such as a polyol having an acid group, a polyol without an acid group, or a polyamine). Alternatively, it may be obtained by further reacting it with a chain extender or crosslinking agent.

[0090] The acid value of the water-soluble resin is preferably 100 mg KOH / g or more and 180 mg KOH / g or less. The acid value of the water-soluble resin can be measured by titration. The weight-average molecular weight of the water-soluble resin in polystyrene terms, measured by gel permeation chromatography (GPC), is preferably 5,000 or more and 20,000 or less.

[0091] The content (mass%) of water-soluble resin in the ink is preferably 0.1% by mass or more and 5.0% by mass or less, based on the total mass of the ink. Furthermore, the content (mass%) of water-soluble resin is preferably 0.1 times or more and 2.0 times the total mass ratio of the content (mass%) of the first resin particles and the second resin particles.

[0092] The physical properties of water-soluble resins, such as composition, weight-average molecular weight, and acid value, can be measured according to conventionally known methods. Specifically, the physical properties of water-soluble resins can be measured by analyzing the precipitate and supernatant obtained by centrifuging the ink. While water-soluble resins can be analyzed in their ink state, it is preferable to analyze water-soluble resins extracted from the ink because this improves measurement accuracy. Specifically, it is preferable to add an excess acid (such as hydrochloric acid) to the supernatant obtained by centrifuging the ink at 75,000 rpm, and then analyze the precipitated resin after drying.

[0093] By analyzing the resin separated from the ink using high-temperature gas chromatography / mass spectrometry (high-temperature GC / MS), it is possible to identify the types of units that make up the water-soluble resin. Furthermore, nuclear magnetic resonance ( 13 By quantitatively analyzing the data using methods such as 13C-NMR or Fourier transform infrared spectrophotometer (FT-IR), the molecular weight and type of monomers constituting each unit can be determined.

[0094] The acid value of water-soluble resins can be measured by titration. Specifically, a sample for measurement is prepared by dissolving the water-soluble resin in tetrahydrofuran (THF). Then, the acid value of the water-soluble resin can be measured by potentiometric titration of the prepared sample using a potentiometric automatic titrator with potassium hydroxide ethanol titrant. For example, a potentiometric automatic titrator such as the "AT510" (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) can be used.

[0095] The weight-average molecular weight of water-soluble resins can be measured by gel permeation chromatography (GPC). The measurement conditions for GPC can be as follows: • Equipment: Alliance GPC 2695 (manufactured by Waters) • Column: Shodex KF-806M 4-row column (manufactured by Showa Denko) ·Mobile phase: THF (special grade) ·Flow rate: 1.0mL / min Oven temperature: 40.0℃ • Injection volume of sample solution: 0.1 mL • Detector: RI (Refractive Index) • Polystyrene standard samples: PS-1 and PS-2 (manufactured by Polymer Laboratories, 17 types with molecular weights of 7,500,000, 2,560,000, 841,700, 377,400, 320,000, 210,500, 148,000, 96,000, 59,500, 50,400, 28,500, 20,650, 10,850, 5,460, 2,930, 1,300, and 580).

[0096] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. The ink may further contain a water-soluble organic solvent as an aqueous medium. Deionized water or ion-exchanged water is preferred as the water. The water content (mass%) in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. Any of the water-soluble organic solvents commonly used in inks can be used as the water-soluble organic solvent. Examples include alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. The water-soluble organic solvent content (mass%) 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.

[0097] [Other additives] In addition to the components mentioned above, the ink may also contain, as necessary, water-soluble organic compounds that are solid at room temperature, such as polyhydric alcohols like trimethylolpropane and trimethylolethane, and urea derivatives like urea and ethylene urea. Furthermore, the ink may also contain, as necessary, various additives such as surfactants, pH adjusters, rust inhibitors, preservatives, fungicides, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents, and other resins.

[0098] [Ink properties] Since the ink is an aqueous ink used in an inkjet system, it is preferable to appropriately control its physical properties. Specifically, the surface tension of the ink at 25°C, as measured by the plate method, is preferably 20 mN / m to 60 mN / m, and more preferably 25 mN / m to 45 mN / m. The viscosity of the ink at 25°C is preferably 1.0 mPa·s to 10.0 mPa·s, and more preferably 1.0 mPa·s to 5.0 mPa·s. The pH of the ink at 25°C is preferably 7.0 to 10.0. [Examples]

[0099] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited 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.

[0100] <Preparation of aqueous dispersion of the first resin particles> A reaction vessel equipped with a stirring device was placed in a hot water bath. 1,178 parts of water were added to the reaction vessel, and the internal temperature was maintained at 70°C. Monomers were mixed according to the breakdown (%) shown in Table 1-1 to prepare 466 parts of monomer mixture for the core. In addition, 1.9 parts of potassium persulfate and 659 parts of water were mixed to prepare aqueous polymerization initiator solution 1. The monomer mixture for the core and aqueous polymerization initiator solution 1 were added dropwise to the reaction vessel in parallel over 60 minutes. After the dropwise addition was complete, stirring was continued and the reaction was allowed to proceed for another 30 minutes to synthesize particles that would become the core of the first resin particles.

[0101] Next, the monomers were mixed according to the breakdown (%) shown in Table 1-1 to prepare 80 parts of monomer mixture for the shell portion. In addition, aqueous solution 2 of the polymerization initiator was prepared by mixing 0.1 parts of potassium persulfate and 133 parts of water. The monomer mixture for the shell portion and aqueous solution 2 of the polymerization initiator were added dropwise to the reaction vessel containing the particles that would become the core portion, in parallel over 10 minutes. After the addition was complete, the reaction was continued by stirring at 80°C for 10 minutes to synthesize the shell portion, and first resin particles having a core-shell structure were synthesized in which the particles that would become the core portion were coated with the resin that would become the shell portion. However, shell portions were not synthesized for first resin particles 2, 4, 6, 8, 18, 19, and 25.

[0102] Subsequently, an appropriate amount of 8 mol / L potassium hydroxide aqueous solution was added to the reaction vessel to adjust the pH of the liquid to 8.5. Furthermore, the amount (parts) and breakdown (%) of fluorescent dye (powdered) shown in Table 1-2 were added, and the temperature was raised to 80°C. After that, the mixture was stirred for 2 hours to allow the fluorescent dye to stain the resin particles. Next, an appropriate amount of 8 mol / L potassium hydroxide aqueous solution was added to the reaction vessel to adjust the pH of the liquid to 8.5. An appropriate amount of water was further added to obtain aqueous dispersions of first resin particles 1 to 28, with a first resin particle content of 20.0%. For the aqueous dispersion of first resin particle 29, a pink fluorescent pigment (product name "SF-3017", manufactured by Shinloihi) was used, adjusted to have a resin particle content of 20.0%. For the aqueous dispersion of first resin particle 30, a pink fluorescent pigment (product name "SF-5017", manufactured by Shinloihi) was used, adjusted to have a resin particle content of 20.0%.

[0103] Percentage of cyano group-containing units in the first resin particle (mass%), particle size of the first resin particle (cumulative 50% particle size of the volume-based particle size distribution), glass transition temperature Tg1 (°C), specific gravity (g / cm³). 3 Table 1-2 shows the results. The particle size of the resin particles was measured using a dynamic light scattering particle size analyzer (product name "UPA-EX150", manufactured by Nikkiso) under the following conditions: SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. The methods for measuring the glass transition temperature and specific gravity of the resin particles are also shown below. Of the fluorescent dyes used, "CI Acid Red 52" and "CI Acid Yellow 73" do not belong to any of the categories of basic dyes, disperse dyes, or oil-soluble dyes.

[0104] [Method for measuring the glass transition temperature of resin particles] Stained resin particles were mixed with 1 mol / L hydrochloric acid in a 1:1 ratio (by mass) to precipitate the resin particles. The collected precipitate was washed three times with water and dried in an oven for 24 hours. The resulting dried material was dissolved in tetrahydrofuran (THF), and the THF solution was filtered through a 0.2 μm polytetrafluoroethylene filter. The recovered filtrate was dried at room temperature for 24 hours. The resulting dried material was collected, and the glass transition temperature was measured using a differential scanning calorimetry analyzer (product name "DSC2500", manufactured by TA Instruments Japan).

[0105] [Method for measuring the specific gravity of resin particles] Stained resin particles were mixed with 1 mol / L hydrochloric acid in a 1:1 ratio (by mass) to precipitate the resin particles. The collected precipitate was washed three times with water and dried in an oven for 24 hours. The resulting dried material was dissolved in tetrahydrofuran (THF), and the THF solution was filtered through a 0.2 μm polytetrafluoroethylene filter. The recovered filtrate was dried at room temperature for 24 hours. The resulting dried material was collected, and its specific gravity was measured using a hydrometer (product name "Automatic Hydrometer DSG-1", manufactured by Toyo Seiki Seisakusho).

[0106] The meanings of the abbreviations in Tables 1-1 and 1-2 are shown below. AN: Acrylonitrile • MAN: Methacrylonitrile St: Styrene BzMA: Benzyl methacrylate • MAA: Methacrylic acid • SR-10: α-Sulfo-ω-(1-alkoxymethyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl)ammonium salt (reactive surfactant, trade name "Adekaria Soap SR-10", manufactured by ADEKA) • EDMA: Ethylene glycol dimethacrylate • EX-810: Ethylene glycol diglycidyl ether (product name "Denacol EX-810", manufactured by Nagase ChemteX) BR1: CI Basic Red 1 BV11: CI Basic Violet 11 DY82: CI Disperse Yellow 82 ·SY196: CI Solvent Yellow 196 AR52:CI Acid Red 52 AY73: CI Acid Yellow 73

[0107] TIFF2023087653000001.tif228170

[0108] TIFF2023087653000002.tif217170

[0109] <Preparation of aqueous dispersion of the second resin particles> A reaction vessel equipped with a stirring device was placed in a hot water bath. 1,178 parts of water were added to the reaction vessel, and the internal temperature was maintained at 70°C. Monomers were mixed according to the breakdown (%) shown in Table 2 to prepare 466 parts of monomer mixture for the core. In addition, 1.9 parts of potassium persulfate and 659 parts of water were mixed to prepare aqueous polymerization initiator solution 3. The monomer mixture for the core and aqueous polymerization initiator solution 3 were added dropwise to the reaction vessel in parallel over 60 minutes. After the dropwise addition was complete, stirring was continued and the reaction was allowed to proceed for another 30 minutes to synthesize particles that would become the core of the second resin particles.

[0110] Next, the monomers in the breakdown (%) shown in Table 2 were mixed to prepare 80 parts of the monomer mixture for the shell portion. In addition, 0.1 parts of potassium persulfate and 133 parts of water were mixed to prepare aqueous solution 4 of the polymerization initiator. The monomer mixture for the shell portion and aqueous solution 4 of the polymerization initiator were added dropwise to the reaction vessel containing the particles that would become the core portion, in parallel over 10 minutes. After the addition was complete, the reaction was continued by stirring at 80°C for 10 minutes to synthesize the shell portion, and second resin particles having a core-shell structure were synthesized in which the particles that would become the core portion were coated with the resin that would become the shell portion. However, the shell portion was not synthesized for second resin particles 1, 4, and 7-18.

[0111] Subsequently, an appropriate amount of 8 mol / L potassium hydroxide aqueous solution was added to the reaction vessel to adjust the pH of the liquid to 8.5. An appropriate amount of water was further added to obtain aqueous dispersions of second resin particles 1-16 and 18 with a resin particle content of 20.0%. For the aqueous dispersion of second resin particle 17, the water was removed by vacuum distillation using a rotary evaporator to adjust the resin particle content to 40.0%. For the aqueous dispersion of second resin particle 19, a polyurethane dispersion (product name "Superflex 740", manufactured by Daiichi Kogyo Seiyaku) was used, which was adjusted to have a resin particle content of 20.0%.

[0112] Particle size of the second resin particle (cumulative 50% particle size of the volume-based particle size distribution), glass transition temperature Tg2 (°C), specific gravity (g / cm³) 3 The results are shown in Table 2. The particle size, glass transition temperature, and specific gravity of the resin particles were measured using the same method as for the first resin particles.

[0113] The meanings of the abbreviations in Tables 2-1 to 2-2 are shown below. AN: Acrylonitrile St: Styrene • EMA: Ethyl methacrylate BzMA: Benzyl methacrylate • 2EHA: 2-Ethylhexyl methacrylate BMA: Butyl methacrylate • SR-10: α-Sulfo-ω-(1-alkoxymethyl-2-(2-propenyloxy)ethoxy)-poly(oxy-1,2-ethanediyl)ammonium salt (product name "Adekaria Soap SR-10", manufactured by ADEKA) • MAA: Methacrylic acid • EDMA: Ethylene glycol dimethacrylate • EX-810: Ethylene glycol diglycidyl ether (product name "Denacol EX-810", manufactured by Nagase ChemteX)

[0114] TIFF2023087653000003.tif142170

[0115] <Synthesis of water-soluble resins> A water-soluble acrylic resin, a random copolymer, was synthesized by polymerizing 60.0 parts of styrene, 21.6 parts of n-butyl acrylate, and 18.4 parts of methacrylic acid using a conventional method. After neutralizing the anionic groups by adding water containing potassium hydroxide equimolar to the acid value, an appropriate amount of water was further added to obtain a liquid containing the water-soluble resin with a resin content of 25.0%. The water-soluble resin was dissolved in tetrahydrofuran to prepare a sample for measurement, and the acid value of the water-soluble resin was measured by potentiometric titration using potassium hydroxide ethanol titrant with a potentiometric automatic titrator (product name "AT510", manufactured by Kyoto Electronics Manufacturing Co., Ltd.). As a result, the acid value of the water-soluble resin was 120 mgKOH / g. The weight-average molecular weight of the water-soluble resin in polystyrene equivalent, measured by GPC, was 10,000.

[0116] <Preparation of aqueous dispersions of organic pigments> Organic pigment (CI Pigment Red 122, specific gravity 1.40 g / cm³) 3 20.0 parts of the organic pigment and 24.0 parts of a liquid containing a water-soluble resin were mixed. Then, the mixture was dispersed for 5 hours using a batch-type vertical sand mill (manufactured by AIMEX) filled with 200 parts of zirconia beads with a diameter of 0.10 mm. Coarse particles were removed by centrifugation, and the mixture was pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to obtain an aqueous dispersion of the organic pigment. The organic pigment content (%) was 20.0%, the water-soluble resin content (%) was 6.0%, and the particle size of the organic pigment (cumulative 50% particle size of the volume-based particle size distribution) was 200 nm.

[0117] <Ink preparation> (Ink 1-53) Each ink was prepared by mixing the components listed below, stirring thoroughly, and then pressure filtering through a 3.0 μm pore size microfilter (manufactured by Fujifilm). In Tables 3-1 and 3-2, "Acetylenel E100" is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. The characteristics of the inks are shown in the lower section of Tables 3-1 and 3-2. The pH of all prepared inks was within the range of 8.5 to 9.0. • Aqueous dispersion of the first type of resin particles shown in Table 3: Usage amount (%) shown in Table 3 • Aqueous dispersion of the second type of resin particles shown in Table 3: Usage amount (%) shown in Table 3 • Liquid containing water-soluble resin: 10.0% Glycerin: 10.0% Trimethylolpropane: 10.0% • Acetyleneol E100: 1.0% • Pure water: Remaining volume (%) when the total amount of components reaches 100.0%

[0118] TIFF2023087653000004.tif214170

[0119] TIFF2023087653000005.tif212170

[0120] (Ink 54) The following components were mixed and thoroughly stirred, then pressure filtered through a 3.0 μm pore size microfilter (manufactured by Fujifilm) to prepare ink 54. The pH of the prepared ink was in the range of 8.5 to 9.0. • Aqueous dispersion of organic pigments: 25.0% • Aqueous dispersion of the second resin particle 1: 25.0% • Liquid containing water-soluble resin: 4.0% Glycerin: 10.0% Trimethylolpropane: 10.0% • Acetyleneol E100: 1.0% • Pure water: Remaining volume (%) when the total amount of components reaches 100.0%

[0121] <Rating> An inkjet recording device (product name "PIXUS Pro-10S", manufactured by Canon) equipped with a recording head that ejects ink using thermal energy was prepared. A heater for adjusting the ink temperature was attached to this inkjet recording device so as to contact the recording head in order to control the temperature of the ink applied to the recording medium. In addition, (i) a contact heating device having the configuration shown in Figure 2, and (ii) a non-contact heating dryer using hot air were installed. Each of the prepared inks was filled into an ink cartridge and set in the above inkjet recording device. In this inkjet recording device, an image recorded under the condition of applying 8 drops of 3.8 ng ± 10% ink to a unit area of ​​1 / 600 inch × 1 / 600 inch is defined as having a recording duty cycle of 100%. Recording media 1 to 6 were also prepared. Details of each recording medium are shown below. The recording environment was set to a temperature of 25°C and a relative humidity of 55%. In this invention, "A" and "B" were defined as acceptable levels and "C" as unacceptable levels in the evaluation criteria for each item below. The evaluation results are shown in Tables 4-1 and 4-2.

[0122] [Details of recording media 1-6] • Recording medium 1: Printing paper, product name "OK Topcoat", basis weight 127.9g, manufactured by Oji Paper Co., Ltd. • Recording medium 2: Glossy paper, product name "Canon Photo Paper Fine-grained Glossy Luster", manufactured by Canon. • Recording medium 3: Vinyl chloride film, product name "KSM-NBZ1370", manufactured by Kimoto. • Recording medium 4: Synthetic paper, "Yupo High Gloss GAR 110", manufactured by Yupo Corporation • Recording medium 5: 100% cotton white fabric • Recording medium 6: Plain paper, product name "GF-500", manufactured by Canon.

[0123] (Color development) Using the inkjet recording device described above, images containing the following gradation patterns were recorded on a recording medium according to the evaluation conditions shown in Tables 4-1 and 4-2. The gradation patterns consist of 2cm x 2cm solid images in which the amount of ink applied was gradually varied, with a maximum of 6 drops of ink applied to a 1 / 600 inch x 1 / 600 inch unit area. After the recorded images were left to stand for one day, the hue angle (H) and saturation (C) in the Lab color system were measured using a spectrophotometer (product name "X-RiteeXact" (M1 light source), manufactured by X-Rite). * ), and brightness (L * The following parameters were measured. The color reproduction of the images was then evaluated according to the evaluation criteria shown below. Brightness was evaluated using the value at a saturation of 50. However, if the maximum saturation did not reach 50, the data obtained by measuring the gradation pattern was extrapolated, and the calculated brightness was used for evaluation. The evaluation criteria were changed according to the hue angle because the preferred color tone perceived visually differs depending on the type of color.

[0124] [When the hue angle is between 0° and less than 180°] A: The maximum saturation was 60 or higher and the brightness was 80 or higher, or the maximum saturation was 50 or higher and the brightness was 85 or higher. B: The maximum saturation was between 50 and 60, and the brightness was between 80 and 85. C: Maximum saturation was less than 50, or brightness was less than 80.

[0125] [When the hue angle is between 180° and less than 360°] A: The maximum saturation was 60 or higher and the brightness was 70 or higher, or the maximum saturation was 50 or higher and the brightness was 75 or higher. B: The maximum saturation was between 50 and 60, and the brightness was between 70 and 75. C: The maximum saturation was less than 50, or the brightness was less than 70.

[0126] (Discharge stability) Using the inkjet recording device described above, five solid images measuring 19 cm x 26 cm with a 100% recording duty cycle were recorded onto a recording medium according to the evaluation conditions shown in Tables 4-1 and 4-2. Subsequently, the ejection ports of the recording head were observed using an optical microscope (Olympus). 100 ejection ports were randomly selected from those from which ink was ejected, and their ejection stability was evaluated according to the evaluation criteria shown below. A: Fewer than 10 outlets were found to have solid deposits. B: The number of outlets where solid deposits were observed was between 10 and 30. C: More than 30 outlets were found to have solid deposits.

[0127] (Abrasion resistance) Using the inkjet recording device described above, a solid image (200mm x 200mm) with a 100% recording duty cycle was recorded onto a recording medium according to the evaluation conditions shown in Tables 4-1 and 4-2 to obtain a recorded material. Using an abrasion resistance tester (manufactured by Imoto Seisakusho), a JSPS-type testing machine conforming to JIS L 0849, a friction test was performed on the solid image area one hour after recording, under the condition of 10 back-and-forth movements with a load of 500g. This friction test constituted one cycle, and the friction cloth was replaced after each cycle, resulting in 10 cycles of friction testing. The solid image after 10 cycles of friction testing was examined visually and with an optical microscope (manufactured by Olympus), and the abrasion resistance was evaluated according to the evaluation criteria shown below. A: No abrasion marks were observed in the solid image by either visual observation or optical microscope observation. B: No abrasion marks were observed in the solid image under visual inspection, but abrasion marks were observed under optical microscope observation. C: There were abrasion marks on the solid image that could be seen by visual inspection.

[0128] TIFF2023087653000006.tif255162

[0129] TIFF2023087653000007.tif255161

[0130] Furthermore, the disclosure of this embodiment includes the following methods and configurations. (Method 1) A recording step of ejecting aqueous ink from an inkjet recording head and applying it to a recording medium, and the recording medium to which the aqueous ink has been applied is heated to a temperature T H An inkjet recording method comprising a heating step of heating at (°C), The aqueous ink contains first resin particles and second resin particles, The first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes, and also contain cyano group-containing units. The second resin particles do not contain colorants, The temperature T H An inkjet recording method characterized in that (°C) is lower than the glass transition temperature Tg1 (°C) of the first resin particle and higher than the glass transition temperature Tg2 (°C) of the second resin particle. (Method 2) The temperature T H The inkjet recording method according to Method 1, wherein (°C) is 10°C or more higher than the glass transition temperature Tg2(°C) of the second resin particle. (Method 3) The temperature T H The inkjet recording method according to method 1 or 2, wherein the temperature (°C) is 10°C or more lower than the glass transition temperature Tg1 (°C) of the first resin particle. (Method 4) The temperature T of the aqueous ink applied to the recording medium I An inkjet recording method according to any one of methods 1 to 3, wherein (°C) is lower than the glass transition temperature Tg2(°C) of the second resin particle. (Method 5) The inkjet recording method according to any one of Methods 1 to 4, wherein the second resin particles comprise at least one of a cyano group-containing unit and a unit derived from a (meth)acrylic acid ester. (Method 6) Specific gravity of the second resin particles (g / cm³) 3 ) is the specific gravity (g / cm³) of the first resin particles. 3 An inkjet recording method described in any one of methods 1 to 5, which is lower than ). (Method 7) Specific gravity of the first resin particles (g / cm³) 3) is 1.20 g / cm³ 3 The inkjet recording method according to any one of the following methods 1 to 6. (Method 8) An inkjet recording method according to any one of Methods 1 to 7, wherein the cumulative 50% particle size of the volume-based particle size distribution of the second resin particles is smaller than the cumulative 50% particle size of the volume-based particle size distribution of the first resin particles. (Method 9) The inkjet recording method according to any one of Methods 1 to 8, wherein the content (mass%) of the second resin particles in the aqueous ink is 0.3 times or more and 3.0 times or less by mass ratio to the content (mass%) of the first resin particles. (Method 10) The inkjet recording method according to any one of Methods 1 to 9, wherein the proportion (mass%) of the cyano group-containing units in the first resin particles is 15.0% by mass or more. (Method 11) The inkjet recording method according to any one of Methods 1 to 10, wherein the proportion (mass%) of the fluorescent dye in the first resin particles is 1.0% by mass or more and 8.0% by mass or less. (Configuration 1) an aqueous ink, an inkjet recording head that ejects the aqueous ink and applies it to a recording medium, and the recording medium to which the aqueous ink has been applied is heated to temperature T H An inkjet recording apparatus comprising a heating means for heating at (°C), The aqueous ink contains first resin particles and second resin particles, The first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes, and also contain cyano group-containing units. The second resin particles do not contain colorants, The temperature T H An inkjet recording apparatus characterized in that the temperature (°C) is lower than the glass transition temperature Tg1 (°C) of the first resin particle and higher than the glass transition temperature Tg2 (°C) of the second resin particle.

Claims

1. a recording step of ejecting water-based ink from an inkjet recording head onto a recording medium; and Ｈ and a heating step of heating at (°C), the water-based ink contains first resin particles and second resin particles, the first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes, and contain a cyano group-containing unit; the second resin particles do not encapsulate a colorant, The temperature T Ｈ (°C) is the glass transition temperature Tg of the first resin particles １ (°C) lower than the glass transition temperature Tg ２ (°C) or higher.

2. The temperature T Ｈ (°C) is the glass transition temperature Tg of the second resin particles ２ 2. The ink jet recording method according to claim 1, wherein the temperature is 10° C. or more higher than the reference temperature.

3. The temperature T Ｈ (°C) is the glass transition temperature Tg of the first resin particles １ 2. The ink jet recording method according to claim 1, wherein the temperature is 10° C. or more lower than the reference temperature.

4. The temperature T of the water-based ink applied to the recording medium Ｉ (°C) is the glass transition temperature Tg of the second resin particles ２ The ink jet recording method according to claim 1, wherein the temperature is lower than 100°C.

5. The inkjet recording method according to claim 1 , wherein the second resin particles contain at least one of a cyano group-containing unit and a unit derived from a (meth)acrylic acid ester.

6. The specific gravity (g / cm ３ ) is the specific gravity (g / cm ) of the first resin particles ３ 2. The ink jet recording method according to claim 1, wherein the viscosity is lower than 1000 ppm.

7. The specific gravity (g / cm ３ ) is 1.20 g / cm ３ 2. The ink jet recording method according to claim 1, wherein:

8. The inkjet recording method according to claim 7, wherein the specific gravity (g / cm 3 ) of the first resin particles is 1.00 g / cm 3 or more.

9. 2. The inkjet recording method according to claim 1, wherein a particle diameter at 50% cumulative volume of the particle size distribution of the second resin particles is smaller than a particle diameter at 50% cumulative volume of the particle size distribution of the first resin particles.

10. 2. The inkjet recording method according to claim 1, wherein the content (mass %) of the second resin particles in the aqueous ink is 0.3 times or more and 3.0 times or less the content (mass %) of the first resin particles.

11. The inkjet recording method according to claim 1 , wherein the proportion (% by mass) of the cyano group-containing unit in the first resin particles is 15.0% by mass or more.

12. An inkjet recording method as described in Claim 11, wherein the proportion (mass %) of the cyano group-containing units in the first resin particles is 60.0 mass % or less.

13. The inkjet recording method according to claim 1, wherein the glass transition temperature Tg 1 (°C) of the first resin particles is 50°C or higher and 160°C or lower.

14. The inkjet recording method according to claim 1, wherein the glass transition temperature Tg 1 (°C) of the first resin particles is 90°C or higher and 160°C or lower.

15. The inkjet recording method according to claim 1, wherein the second resin particles have a glass transition temperature Tg 2 (°C) of 30°C or higher and 110°C or lower.

16. The inkjet recording method according to claim 1, wherein the specific gravity (g / cm 3 ) of the second resin particles is 1.00 g / cm 3 or more and 1.20 g / cm 3 or less.

17. The inkjet recording method according to claim 1, wherein the temperature T H (°C) is 40°C or higher and 120°C or lower.

18. The inkjet recording method according to claim 1, wherein the temperature T H (°C) is 70°C or higher and 120°C or lower.

19. 19. The inkjet recording method according to claim 1, wherein a proportion (% by mass) of the fluorescent dye in the first resin particles is 1.0% by mass or more and 8.0% by mass or less.

20. a water-based ink, an ink-jet recording head that ejects the water-based ink onto a recording medium, and a recording medium that is heated to a temperature T Ｈ and a heating unit for heating the ink jet recording medium at a temperature of (°C), the water-based ink contains first resin particles and second resin particles, the first resin particles are dyed with at least one fluorescent dye selected from the group consisting of basic dyes, disperse dyes, and oil-soluble dyes, and contain a cyano group-containing unit; the second resin particles do not encapsulate a colorant, The temperature T Ｈ (°C) is the glass transition temperature Tg of the first resin particles １ (°C) lower than the glass transition temperature Tg ２ (°C) or higher.

Images