Inkjet recording method and inkjet recording apparatus

Abstract

An inkjet recording method includes a step (a) in which a recording medium is not heated, and a step (b) in which the recording medium is heated by a heating means, the recording medium being an absorbent recording medium. Step [a]: an ink application step of applying an inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to a recording medium, and Step [b]: an irradiation step of irradiating the inkjet ink applied to the recording medium through at least step [a] with an active energy ray controlled by a unit different from the heating unit.

Description

Technical Field

[0001] This invention relates to inkjet recording methods and inkjet recording apparatus. Background Technology

[0002] Inkjet printing has the following characteristics: easy full-color printing, low noise, high-resolution images at low cost, high-speed printing, printing on curved surfaces as well as flat surfaces, and easy printing on large areas. Therefore, inkjet printing is not limited to personal use and has been rapidly gaining popularity in recent years for commercial inkjet printers used for signatures, window films, posters, car wraps, wallpaper, etc.

[0003] As an inkjet recording method, methods using solvent-free UV inks are known. However, while this method offers excellent coating strength and substrate versatility, it suffers from poor environmental / safety aspects. Due to its high viscosity, the ink thickness is increased, resulting in poor surface smoothness of the printed film.

[0004] In recent years, recording methods using UV-curable water-based inks have also been developed (e.g., Patent Document 1, Patent Document 2).

[0005] UV-curable water-based inks are water-based, thus offering excellent environmental and safety benefits. However, as the ink penetrates the recording medium, the curing components of UV-curable water-based inks also diffuse. Even when irradiated with active energy rays in this state, the curing components do not come into contact with each other and cure in a dispersed state. Therefore, there is a problem with the resulting printed film strength, particularly its wash fastness, being poor.

[0006] This problem is particularly pronounced when the recording medium is absorbent.

[0007] When ink is heated during ink application to prevent ink penetration, the printhead heats up, and the ink concentration increases due to the evaporation of the aqueous medium in the ink. Consequently, the ink viscosity increases, leading to nozzle clogging or ink solidification at the nozzle's ejection point, thus preventing the expectation of stable inkjet output.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2022-067314

[0011] Patent Document 2: Japanese Patent Application Publication No. 2011-218571 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The purpose of this invention is to provide an inkjet recording method and apparatus that, in inkjet recording using ultraviolet-curable aqueous inks, can obtain a printed coating with high wash fastness by suppressing the penetration of ultraviolet-curable aqueous inks into the recorded medium while maintaining stable inkjet ejection.

[0014] Solution for solving the problem

[0015] The inventors have discovered that the above-mentioned problem can be solved by not heating the recording medium during the ink application process of applying UV-curable aqueous ink to the recording medium, but heating the recording medium during the subsequent irradiation process with active energy rays.

[0016] The present invention is based on the following principles.

[0017] [1] An inkjet recording method comprising the following steps [a] and [b], wherein in step [a] no recording medium is heated, and in step [b] the recording medium is heated by a heating unit, wherein the recording medium is an absorbent recording medium.

[0018] Process [a]: Ink application process, which applies inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium.

[0019] Process [b]: Irradiation process, wherein the inkjet ink imparted to the recording medium by at least process [a] is irradiated with active energy rays controlled by a unit different from the heating unit.

[0020] [2] An inkjet recording method comprising the following steps [a] and [b], wherein in step [a] the recording medium is not heated, and in step [b] the recording medium is heated by a heating unit, wherein the polymeric compound in step [a] exists in the form of particles in the inkjet ink.

[0021] Process [a]: Ink application process, which applies inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium.

[0022] Process [b]: Irradiation process, wherein the inkjet ink imparted to the recording medium by at least process [a] is irradiated with active energy rays controlled by a unit different from the heating unit.

[0023] [3] According to the inkjet recording method described in [1] or [2], the light source of the active energy rays is a light-emitting diode having a peak emission wavelength in the range of 350 to 420 nm.

[0024] [4] According to the inkjet recording method of [1] or [3], wherein the absorbent recording medium is cloth.

[0025] [5] According to the inkjet recording method of [2] or [3], wherein the average particle size is greater than 10 nm and less than 200 nm.

[0026] [6] The inkjet recording method according to any one of [1] to [5], wherein the polymeric compound comprises a (meth)acrylate compound.

[0027] [7] The inkjet recording method according to any one of [1] to [6], wherein the heating temperature of the recording medium in step [b] is above 30°C and below 70°C.

[0028] [8] The inkjet recording method according to any one of [1] to [7], wherein a heating element is used as the heating unit.

[0029] [9] The inkjet recording method according to any one of [1] to [8], wherein the recording medium in the irradiation step [b] is heated from a surface opposite to the ink-spreading surface.

[0030]

[10] An inkjet recording apparatus for recording images onto an absorbent recording medium, the inkjet recording apparatus comprising:

[0031] The ink delivery unit [c] delivers inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the absorbent recording medium without heating it.

[0032] The irradiation unit [d] irradiates the inkjet ink imparted to the absorbent recording medium with active energy rays; and

[0033] The heating unit [e] heats the absorbent recording medium when irradiated with the active energy rays.

[0034] The irradiation unit [d] and the heating unit [e] can be controlled independently.

[0035]

[11] An inkjet recording apparatus for recording images onto a recording medium, the inkjet recording apparatus comprising:

[0036] The ink delivery unit [c] delivers inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the recording medium without heating it.

[0037] The irradiation unit [d] irradiates the inkjet ink applied to the recording medium with active energy rays; and

[0038] The heating unit [e] heats the recording medium when irradiated by the active energy rays.

[0039] The irradiation unit [d] and the heating unit [e] can be controlled independently.

[0040] The polymeric compound exists in the inkjet ink in the form of particles.

[0041]

[12] In the inkjet recording apparatus according to

[10] or

[11] , the light source of the active energy rays is a light-emitting diode having a peak wavelength in the range of 350 to 420 nm.

[0042]

[13] According to the inkjet recording apparatus of

[10] , the absorbent recording medium is cloth.

[0043]

[14] According to the inkjet recording apparatus of

[11] , the average particle size is 10 nm or more and 200 nm or less.

[0044]

[15] The inkjet recording apparatus according to any one of

[10] to

[14] , wherein the polymeric compound comprises a (meth)acrylate compound.

[0045]

[16] The inkjet recording apparatus according to any one of

[10] to

[15] , wherein a heating element is used as the heating unit [e].

[0046]

[17] The inkjet recording apparatus according to any one of

[10] to

[15] , wherein the heating unit [e] is located on the side of the absorbent recording medium or the recording medium opposite to the ink-spreading surface.

[0047] Invention Effects

[0048] According to the inkjet recording method and apparatus of the present invention, in inkjet recording using UV-curable aqueous inks with excellent environmental and safety features, the penetration of UV-curable aqueous inks into the recorded medium can be suppressed while maintaining stable inkjet ejection, thereby obtaining a printed coating with high wash fastness.

[0049] Therefore, according to the present invention, by improving the coating strength such as ink ejection stability and wash fastness in inkjet recording, high-quality printed images can be obtained efficiently. Detailed Implementation

[0050] Hereinafter, one embodiment of the present invention will be described. However, the present invention is not limited to this embodiment.

[0051] In this invention, when expressed as "X to Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the intention of "X or more and Y or less", and also includes the intention of "preferably greater than X" and "preferably less than Y".

[0052] In this invention, the expression "X or more" (where X is any number) or "Y or less" (where Y is any number) also includes the intention of "preferably greater than X" or "preferably less than Y".

[0053] Inkjet Recording Methods

[0054] An inkjet recording method according to one embodiment of the present invention (hereinafter, sometimes referred to as "inkjet recording method 1") is characterized by having the following steps [a] and [b], wherein in step [a] the recording medium is not heated, and in step [b] the recording medium is heated by a heating unit, wherein the recording medium is an absorbent recording medium.

[0055] Step [a]: The ink application step (hereinafter, sometimes referred to as "ink application step [a]") applies an inkjet ink (hereinafter, sometimes referred to as "the inkjet ink of the present invention") containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium.

[0056] Process [b]: Irradiation process (hereinafter, sometimes referred to as “irradiation process [b]”), which irradiates the inkjet ink imparted to the recording medium by at least process [a] with active energy rays controlled by a unit different from the heating unit.

[0057] Another embodiment of the inkjet recording method of the present invention (hereinafter, sometimes referred to as "inkjet recording method 2") is characterized by having the following steps [a] and [b], wherein the recording medium is not heated in step [a], and the recording medium is heated by a heating unit in step [b], wherein the polymeric compound in step [a] exists in the form of particles in the inkjet ink.

[0058] Step [a]: Ink application step (i.e., "ink application step [a]"), which applies an inkjet ink (i.e., "the inkjet ink of the present invention") containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium.

[0059] Process [b]: Irradiation process (i.e., "irradiation process [b]"), which irradiates the inkjet ink, which has been imparted to the recording medium by at least process [a], with active energy rays controlled by a unit different from the heating unit.

[0060] The inkjet recording method 1 and inkjet recording method 2 of the present invention (hereinafter, they are sometimes collectively referred to as "the inkjet recording method of the present invention") may further include other steps as needed.

[0061] For example, there may also be a process of heating the recorded medium after the irradiation process [b] (hereinafter, sometimes referred to as the "post-heating process").

[0062] In addition, there may be a pretreatment process that applies a pretreatment agent to the recording medium before the ink application process.

[0063] 〔mechanism〕

[0064] In the inkjet recording method of the present invention, the recording medium is not heated in the ink application step [a], and is heated by a heating unit in the irradiation step [b].

[0065] When the recording medium is heated, the aqueous medium in the ink applied to the recording medium evaporates.

[0066] Heating is performed during the irradiation process [b], causing some of the aqueous medium to evaporate and increasing the ink concentration, without completely evaporating the aqueous medium to the point of becoming a solid. As a result, the ink viscosity increases. This increased ink viscosity on the recording medium inhibits ink penetration even in absorbent recording media, allowing the ink to remain near the surface of the recording medium when irradiated with active energy rays. Consequently, the curing components in the ink solidify in a concentrated state, improving the wash fastness of the printed coating.

[0067] In particular, when the recorded medium is an absorbent recording medium, the ink cures while being entrained in the fibers of the absorbent recording medium. Therefore, wash fastness is further improved (inkjet recording method 1).

[0068] Furthermore, if the polymeric compound exists in the inkjet ink in the form of particles, the ink will not excessively penetrate the recording medium even if the recording medium is absorbent, and will easily remain near the surface. As a result, the reduction in image density can be suppressed, and a coating with excellent wash fastness can be formed (inkjet recording method 2).

[0069] In order to evaporate the aqueous medium in the ink, heating is performed between the ink application process [a] and the irradiation process [b] with active energy rays. If heating is not performed in the irradiation process [b], the device requires space for each of the three processes, which results in a large-scale device, which is not preferred.

[0070] Furthermore, if heating is continuously performed from the ink application process [a] to the irradiation process of the active energy rays [b], as mentioned above, the printhead will be heated, thereby compromising the stability of ink ejection.

[0071] In contrast, in this invention, heating is not performed in the ink application process [a], but in the irradiation process [b], thus solving the problem described above.

[0072] In this invention, heating can be performed in the irradiation process [b] but not in the ink application process [a], or heating time can exist before and after the irradiation process [b].

[0073] [Ink application process[a]]

[0074] In the ink application step [a] of the inkjet recording method of the present invention, the inkjet ink of the present invention contained in the ink group is applied from, for example, the printhead of the inkjet printer to the recording medium.

[0075] As for the method of applying inkjet ink in this invention, any method that can apply inkjet ink to the desired image pattern is acceptable, and there are no particular limitations.

[0076] From the viewpoint of compact recording devices and high-speed recording, the inkjet method used in this invention is the preferred method.

[0077] That is, as the ink supply unit [c] in the inkjet recording apparatus of the present invention described later, an inkjet printer is preferred. The preferred embodiments of the inkjet method described below correspond to the preferred embodiments of the ink supply unit [c] in the inkjet recording apparatus of the present invention.

[0078] In inkjet-based image formation, ink is ejected onto the recording medium by supplying energy to form a colored image.

[0079] There are no particular restrictions on the inkjet method. It can be any of the well-known methods, such as charge control method that uses electrostatic attraction to eject ink, drop-on-demand method (pressure pulse method) that uses the vibration pressure of piezoelectric elements, and acoustic inkjet method that converts electrical signals into sound beams to irradiate ink and ejects ink using radiation pressure.

[0080] The inkjet printhead used in inkjet printing can be either on-demand or continuous. Furthermore, there are no particular restrictions on the ink nozzles or other components used for recording via inkjet printing; the appropriate type can be selected based on the purpose.

[0081] The inkjet methods of the present invention include: ejecting a large volume of low-concentration ink called photo ink in a small volume; using multiple inks with substantially the same hue but different concentrations to improve image quality; and using colorless and transparent ink.

[0082] As inkjet printing methods, there are reciprocating methods that use a short serial head to scan and record along the width of the recording medium, and line methods that use a line head to arrange recording elements corresponding to the entire area of ​​one side of the recording medium. In the line method, by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, images can be recorded on the entire surface of the recording medium, eliminating the need for a transport system such as a carriage for scanning with the short head. Furthermore, in the line method, there is no need for carriage movement and complex scanning control of the recording medium; only the recording medium is moved, thus achieving a much higher recording speed compared to the reciprocating method.

[0083] [Irradiation process]

[0084] The irradiation step [b] in the inkjet recording method of the present invention is performed after the ink application step [a] described above. The irradiation step [b] is a step of irradiating the recording medium, which has been coated with inkjet ink, with active energy rays. In the present invention, the recording medium is heated in this irradiation step [b].

[0085] The preferred active energy ray source of this irradiation process [b] is equivalent to the preferred embodiment of the irradiation unit [d] of the inkjet recording apparatus of the present invention, which will be described later.

[0086] In the irradiation step [b], the polymerizable compounds contained in the inkjet ink of the present invention are polymerized under the action of a polymerization initiator by irradiation with active energy rays, forming a cured film of the inkjet ink. Furthermore, by heating in this irradiation step [b], as described above, the penetration of the ink into the recorded medium is suppressed, and the wash fastness of the formed printed image is effectively improved.

[0087] As described above, the inkjet ink of the present invention undergoes a curing reaction by irradiation with active energy rays. This reaction is as follows: the polymerization initiator contained in the inkjet ink of the present invention decomposes upon irradiation with active energy rays, generating free radicals, thereby initiating / promoting the polymerization reaction of polymerizable compounds, and thus curing the inkjet ink.

[0088] When the recording medium is pretreated with a pretreatment agent containing an acidic compound, the inkjet ink is further coagulated (immobilized) by the acid supplied by the acidic compound when irradiated with the active energy ray, resulting in improved image quality (abrasion resistance / tack resistance, etc.).

[0089] As active energy rays, alpha rays, gamma rays, electron beams, X-rays, ultraviolet light, visible light, infrared light, etc., can be used. As described later, the polymerization initiator preferably used in the inkjet ink of the present invention has particularly high absorption of light in the ultraviolet region. From this point of view, the emission peak wavelength of the irradiated active energy ray source is preferably in the range of 200 to 600 nm, more preferably in the range of 300 to 450 nm, and even more preferably in the range of 350 to 420 nm.

[0090] The emission peak wavelength can exist in one or more wavelengths within the above-mentioned wavelength range.

[0091] The irradiation energy of the active energy rays is preferably 0.1 J / cm. 2 The above, for example, is particularly preferred to be 0.5 to 10 J / cm. 2 If the irradiation energy is above the lower limit mentioned above, the polymerization reaction of the polymerizable compound can proceed smoothly, resulting in a better improvement in coating strength.

[0092] As active energy radiation sources, mercury lamps and gas / solid-state lasers are mainly used. Mercury lamps, halogen lamps, and metal halide lamps are widely known as light sources for curing UV-curable water-based inks. However, from an environmental protection perspective, there is a strong desire for mercury-free solutions. Therefore, replacing them with GaN-based semiconductor UV light-emitting devices is highly valuable both industrially and environmentally.

[0093] In this context, LEDs (Light-Emitting Diodes) and laser diodes (LDs) are expected to serve as active energy ray sources, especially for photopolymer inkjet printers, due to their small size, long lifespan, high efficiency, and low cost.

[0094] In addition, compared with lamps that generate heat, such as mercury lamps, halogen lamps, and metal halide lamps, LEDs and laser diodes (LDs) have a longer lifespan and a more gradual change in illuminance over time, making them a preferred choice from the perspective of easily obtaining stable printing quality.

[0095] From this perspective, LEDs and LDs are preferably used as active energy ray sources in this invention. In particular, UV-LEDs (Ultraviolet Light-Emitting Diodes) and UV-LDs (Ultraviolet Laser Diodes) can be used as ultraviolet sources. For example, Nichia Chemicals Co., Ltd. has commercially available purple LEDs with a main emission spectrum having wavelengths between 365 nm and 420 nm.

[0096] The active energy radiation source particularly preferred in this invention is a UV-LED, and more particularly preferred is a UV-LED with a peak emission wavelength of 350 to 420 nm.

[0097] That is, in this invention, from the viewpoint of cost and curability, it is preferable to use a light-emitting diode having a peak emission wavelength in the range of 350 to 420 nm.

[0098] In this invention, for reasons explained later, the active energy ray source is controlled by a control unit that is different from the heating unit.

[0099] As described above, in the irradiation process [b], the recording medium is heated by a heating unit. This heating unit corresponds to the heating unit (e) in the inkjet recording apparatus of the present invention, which will be described later.

[0100] Here, "heating" refers to providing heat to the recorded medium through a heating unit. More specifically, for example, when a heating element such as a heating plate is used as a heating unit for heating, "heating" refers to using a power density of 0.05 W / cm². 2 The above heating elements provide heat to the recorded medium.

[0101] Furthermore, the heating unit does not include the aforementioned active energy radiation source. That is, active energy radiation sources may include heat-generating devices such as mercury lamps, but these do not correspond to the heating unit.

[0102] The reasons are as follows.

[0103] When an active energy X-ray source with heat generation is used as a heating unit, such a heating unit usually lacks a mechanism to adjust the heating conditions of the active energy X-ray source, making it difficult to precisely control the heat supplied to the recording medium. As a result, the quality stability of the resulting ink coating may be reduced.

[0104] Furthermore, when using a regenerative energy X-ray source with heat generation as a heating unit, the amount of heat generated depends on the irradiation conditions of the regenerative energy X-ray. Therefore, under the specified irradiation conditions of the regenerative energy X-ray, the amount of heat supplied to the recording medium may be excessive or insufficient.

[0105] For example, if the heating is insufficient, the evaporation of the aqueous medium in the ink becomes inadequate.

[0106] Conversely, excessive heating not only results in significant energy loss and low productivity but may also cause thermal degradation such as deformation and discoloration of the recorded medium. Furthermore, the curing and drying of the outermost surface of the ink coating can hinder the evaporation of the aqueous medium deeper within the coating, potentially leading to poor drying and curing.

[0107] Especially when the recording medium is an absorbent recording medium, leakage is likely to occur due to poor drying and poor curing. Therefore, temperature control and illuminance control become particularly important in the irradiation process [b].

[0108] Therefore, it is necessary to control the irradiation conditions and heating conditions of the active energy rays separately.

[0109] In the irradiation process [b], the heating temperature of the recording medium using the heating unit, which is performed simultaneously with the irradiation by the active energy rays, is not particularly limited as long as it is a temperature at which the aqueous medium contained in the inkjet ink of the present invention can evaporate smoothly. Preferably, it is 30°C or higher, more preferably 35°C or higher, further preferably 40°C or higher, and particularly preferably 60°C or higher. On the other hand, this heating temperature is preferably 120°C or lower, more preferably 100°C or lower, further preferably 80°C or lower, and particularly preferably 70°C or lower.

[0110] If the heating temperature is above the lower limit mentioned above, volatile components such as water in the ink can be efficiently evaporated and removed, and there is a tendency to further improve curability. If the heating temperature is below the upper limit mentioned above, thermal degradation of the recorded medium can be prevented, and shortening of lifespan caused by heating from the active energy ray source can be prevented.

[0111] Furthermore, if the heating temperature is too high, not only will the recording medium reach a high temperature, but the area near the nozzle will also reach a high temperature, which may result in compromised ejection stability. If the heating temperature of the heating unit is below the aforementioned upper limit, ejection defects caused by the heating of the nozzle can be suppressed.

[0112] Considering the recent trend towards miniaturization and lightweighting of various devices and machines, there is a desire for more compact recording devices. However, in this case, the distance between the ink delivery unit and the active energy ray irradiation unit becomes closer. As a result, the ink delivery unit is more susceptible to temperature fluctuations caused by heating. Therefore, as mentioned above, the effect of suppressing ejection defects by controlling the heating temperature becomes more significant.

[0113] Here, the heating temperature is the surface temperature of the recording surface of the recording medium.

[0114] As a heating unit, when heating is performed using a heating element such as a heating plate, the temperature of the heating element can be regarded as the surface temperature.

[0115] From the viewpoint of obtaining a high-resolution printed image, heating of the recording medium is preferably performed from the end face of the recording medium irradiated with active energy rays or from the side opposite to the ink-spreading surface, wherein heating is preferably performed from the side opposite to the ink-spreading surface.

[0116] Heating of the recorded medium can also be achieved by combining heating units from multiple directions.

[0117] The heating unit, namely the heating unit [e] described later, is not particularly limited and can be either warm air heating or radiant heating. From the perspective of excellent drying efficiency, warm air heating units such as warm air heaters are preferred.

[0118] On the other hand, if it is radiant heating, it is preferred in that there is no concern that the ink nozzles will dry out due to the warm air, and the printed image before fixing will not be directly exposed to the warm air, so that a high-resolution printed image can be easily obtained.

[0119] As a radiant heating unit, heating elements such as heating plates and infrared heaters can be used. More specifically, examples include ceramic heaters, halogen heaters, and quartz tube heaters.

[0120] Among them, considering the ability to set precise temperatures and the minimization of temperature unevenness, heating elements such as heating plates are preferred.

[0121] When using a heating element such as a heating plate for heating, heating can be achieved by making the heating element directly contact the recording medium, or by placing a heat-conducting element such as a metal plate between the heating element and the recording medium.

[0122] The heating timing can be simultaneous with the irradiation of active energy rays, or there can be a heating time of up to 20 seconds before or after the irradiation of active energy rays.

[0123] In addition, as mentioned above, a post-heating process can also be performed.

[0124] In the case of a post-heating process, the post-heating process may use the same heating temperature, heating unit and heating method as the heating performed in the irradiation process [b].

[0125] [Recorded medium]

[0126] As a recording medium, there are absorbent recording media and non-absorbent recording media. As mentioned above, the problem of reduced wash fastness due to ink penetration is significant in absorbent recording media. Therefore, the inkjet recording method of the present invention is particularly effective when using absorbent recording media as the recording medium.

[0127] Absorbent recording media refer to recording media with surfaces that are highly absorbent of ink. More quantitatively, this will be measured in the Bristow process from the start of contact to 30 msec. 1 / 2 The water absorption rate up to this point is 0.3 g / m³. 2The recording medium described above is set as an absorbent recording medium. On the other hand, the water absorption rate is less than 0.3 g / m³. 2 The recording medium is set to a non-absorbent recording medium.

[0128] Examples of absorbent recording media include paper, cloth, nonwoven fabric, leather, wood, or composite materials thereof. Among absorbent recording media, cloth is preferred from the perspective of obtaining the significant effects achieved by heating upon irradiation with active energy rays according to the present invention.

[0129] There are no particular restrictions on the raw materials used to make fabrics. Examples include natural fibers such as cotton, linen, wool, and silk; synthetic fibers such as polypropylene, polyester, acetate, triacetate, polyamide, and polyurethane; biodegradable fibers such as polylactic acid; and blends of these fibers.

[0130] Among them, cotton and polyester are preferred, with cotton being even better.

[0131] On the other hand, non-absorbent recording media include: polyesters such as polyethylene terephthalate (PET), plastic materials such as polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP), glass, ceramics, metals, or composites thereof.

[0132] [Inkjet ink]

[0133] The inkjet ink of the present invention contains at least a polymerizable compound, a polymerization initiator, and water. That is, in the inkjet recording method of the present invention, an ultraviolet-curable water-based ink can be used.

[0134] [Polymerizing compounds]

[0135] As for the polymerizable compound contained in the inkjet ink of the present invention, any polymerizable compound is acceptable and there are no particular limitations; known polymerizable monomers, polymerizable resins, polymerizable oligomers, etc., can be used. Among these, polymerizable oligomers are preferred, and ultraviolet-curable oligomers are more preferred.

[0136] Examples of polymerizable compounds include (meth)acrylamide compounds, (meth)acrylate compounds, vinyl compounds, maleimide compounds, vinyl sulfone compounds, N-vinylamide compounds, and their derivatives. These polymerizable compounds are more preferably difunctional or more. Further preferred polymerizable compounds are (meth)acrylamide compounds, (meth)acrylate compounds, and vinyl compounds; particularly preferred are (meth)acrylamide compounds or (meth)acrylate compounds with difunctionality or more.

[0137] In this invention, "(meth)acrylate" refers to acrylate or methacrylate. The same applies to "(meth)acryloyl" and "(meth)acrylate".

[0138] These polymerizable compounds can be used alone or in combination of two or more. When two or more are used in combination, it is preferable to use two or more selected from (meth)acrylamide compounds, (meth)acrylate compounds, vinyl compounds, maleimide compounds, vinyl sulfone compounds and N-vinylamide compounds, and more preferably at least one of them is a (meth)acrylamide compound or a (meth)acrylate compound.

[0139] From the perspective of improving water solubility, the aforementioned polymeric compounds can possess hydrophilic functional groups such as (poly)ethylene oxide chains, (poly)propylene oxide chains, ionic groups (e.g., carboxyl groups, sulfonyl groups, etc.), and hydroxyl groups within their molecules. By including hydrophilic functional groups in the polymeric compounds, dispersibility in aqueous media can be improved. Here, "(poly)ethylene oxide chains" refers to either ethylene oxide chains or polyethylene oxide chains. The same applies to "(poly)propylene oxide chains."

[0140] As (meth)acrylate compounds, either monofunctional (meth)acrylate compounds (compounds having one (meth)acryloyl group) or polyfunctional (meth)acrylate compounds can be used. Polyfunctional (meth)acrylate compounds are preferred.

[0141] As a UV-curable oligomer, there are no particular restrictions on whether it is ionic or not; it can be nonionic or ionic (anionic, cationic, or amphoteric).

[0142] Here, nonionicity means, for example, that the hydrophilic groups of the UV-curable oligomer are composed of ether bonds and hydroxyl groups that do not undergo ionic dissociation in water.

[0143] Ionicity (anionic, cationic, or amphoteric) refers to, for example, the UV-curable oligomers described above having carboxyl or amino groups that can be ionically dissociated in water.

[0144] As a UV-curable oligomer, the following are preferred examples. <1> ~ <3> Any one of these UV-curable oligomers.

[0145] <1> UV-curable oligomers having structural units derived from compounds represented by the following formula (1).

[0146] [Chemical Formula 1]

[0147]

[0148] (In formula (1), X is an alkylene group. Y is any one of (meth)acryloyl, allyl, acyl, or hydrogen atom. n is an integer greater than or equal to 2.)

[0149] <2> UV-curable oligomers having structural units derived from a polyisocyanate compound (A), wherein the compound (A) is a compound having three or more isocyanate groups in one molecule.

[0150] <3> UV-curable oligomers having structural units derived from polyisocyanate compound (A), structural units derived from compound (B') shown below, and structural units derived from compound (C') shown below.

[0151] The <3> Such UV-curable oligomers are typically manufactured by reacting polyisocyanate compound (A), compound (B'), and compound (C').

[0152] Compound (B'): A compound containing two or more polymerizable unsaturated bonds that can bond with polyisocyanate compound (A).

[0153] Compound (C'): A water-soluble compound that can bond with polyisocyanate compound (A).

[0154] As a UV-curable oligomer, a UV-curable oligomer comprising structural units derived from (meth)acrylates is preferred, and a UV-curable oligomer comprising structural units derived from polyfunctional (meth)acrylates is particularly preferred. A UV-curable oligomer comprising structural units derived from both polyfunctional (meth)acrylates and polyalkylene glycols is even more preferred. That is, from a reactivity point of view, compound (B') is preferably a hydroxyl-containing polyfunctional (meth)acrylate (B). Furthermore, from a water dispersibility point of view, compound (C') is preferably a polyalkylene glycol (C). Such UV-curable oligomers are typically manufactured by reacting a polyisocyanate compound (A), a hydroxyl-containing polyfunctional (meth)acrylate (B), and a polyalkylene glycol (C).

[0155] In this invention, a "structural unit derived from X" refers to a structural unit that is incorporated into the molecular structure of a UV-curable oligomer by reacting compound X with other compounds using compound X as a raw material. The term "structural unit derived from X" is not necessarily limited to using compound X as a raw material. That is, even if formed from raw materials other than X, as long as the chemical structure is the same, it is equivalent to a "structural unit derived from X".

[0156] As described above, a preferred embodiment of compound (B') is a polyfunctional (meth)acrylate (B) containing hydroxyl groups, and a preferred embodiment of compound (B') may also be "a compound (B) containing hydroxyl groups and having two or more polymerizable unsaturated bonds"".

[0157] The "compound that can bond with polyisocyanate compound (A)" in compound (B') can also be a compound formed by replacing the hydroxyl group of compound (B) with a carboxyl group, amino group, etc. Examples of polymerizable unsaturated bonds include carbon-carbon double bonds and carbon-carbon triple bonds, with carbon-carbon double bonds being preferred. More specifically, examples of polymerizable unsaturated bonds include carbon-carbon double bonds derived from vinyl groups, (meth)acryloyl groups, etc.

[0158] The water-soluble compound in compound (C') includes a water-soluble polymer. Specifically, examples of water-soluble compounds in compound (C') include: polyglycerol, poly(meth)acrylates, polyamines, quaternized polystyrene, sulfonated polystyrene, polyethers, and polyalkylene glycols. Among these, polyglycerol, poly(meth)acrylates, and polyalkylene glycols, which are nonionic water-soluble compounds, are preferred, and polyalkylene glycols are particularly preferred. These water-soluble compounds may also be copolymers.

[0159] Compound (C') has the structure of a water-soluble compound and the structure of a "compound that can bond with polyisocyanate compound (A)". Here, the structure of the "compound that can bond with polyisocyanate compound (A)" can be selected from the same structure as that exemplified as compound (B').

[0160] The structural unit derived from the polyisocyanate compound (A) forms a urethane bond by bonding with structural units derived from the hydroxyl-containing polyfunctional (meth)acrylate (B) and structural units derived from the polyalkylene glycol (C). This urethane bond can also be replaced by a urea bond or an amide bond, respectively.

[0161] In this invention, when the hydroxyl-containing polyfunctional (meth)acrylate (B) is the above-described compound (B') or compound (B"), or when the polyalkylene glycol (C) is the above-described compound (C'), the preferred or specific embodiments in which the hydroxyl-containing polyfunctional (meth)acrylate (B) or polyalkylene glycol (C) described later can also be applied.

[0162] The following describes the components of the above. <1> , <2> , <3> The compounds of the UV-curable oligomers shown will be described. In this invention, "oligomer" is not a term limited to a specific molecular weight range, etc., as long as it has the structure shown below.

[0163] It should be noted that the inkjet ink of the present invention may contain only one type of UV-curable oligomer, or it may contain two or more types.

[0164] <Polyisocyanate compound (A)>

[0165] A polyisocyanate compound (A) is a compound having a total of two or more isocyanate groups in one molecule.

[0166] There are no particular limitations on the types of polyisocyanate compound (A), including: chain aliphatic polyisocyanates, aromatic polyisocyanates, alicyclic polyisocyanates, etc. Among them, from the viewpoint of weather resistance and hardness, polyisocyanate compound (A) is preferably a trimer compound containing polyisocyanate.

[0167] UV-curable oligomers may use only one of these polyisocyanate compounds (A), or they may use two or more in combination. In addition, as polyisocyanate compound (A), polyisocyanates having two or more structures among chain aliphatic structure, aromatic structure, and alicyclic structure may also be used.

[0168] From the viewpoint of adhesion to the substrate, polyisocyanate compound (A) is preferably a polyisocyanate compound having three or more isocyanate groups, and more preferably a polyisocyanate compound having six or fewer isocyanate groups. Polyisocyanate compound (A) is preferably a trimer obtained by a trimerization reaction of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenylene diisocyanate, etc., and particularly preferably a trimer of hexamethylene diisocyanate.

[0169] <Compounds containing polymeric unsaturated bonds>

[0170] In compounds containing polymerizable unsaturated bonds, the number of polymerizable unsaturated bonds is preferably 1 or more, more preferably 2 or more, even more preferably 4 or more, and on the other hand, preferably 8 or less, more preferably 6 or less.

[0171] The compound containing polymerizable unsaturated bonds is preferably a compound that can bond with the polyisocyanate compound (A).

[0172] (Compound (B'))

[0173] Compound (B') is a compound containing two or more polymerizable unsaturated bonds that can bond with polyisocyanate compound (A).

[0174] Compound (B') can be any compound having one of a hydroxyl, an amino, or a carboxyl group. Furthermore, compounds (B') can include: polyfunctional vinyl monomers, polyfunctional allyl monomers, and polyfunctional (meth)acrylates. Among these, polyfunctional (meth)acrylates (B) containing a hydroxyl group are preferred as compound (B').

[0175] <Hydroxy-containing polyfunctional (meth)acrylates (B)>

[0176] Hydroxyl-containing polyfunctional (meth)acrylates (B) have one or more hydroxyl groups and two or more (meth)acryloyl groups. Specifically, (meth)acrylate fractions of polyols can be cited as examples of hydroxyl-containing polyfunctional (meth)acrylates (B). Through the participation of multiple (meth)acryloyl groups in the curing reaction, hydroxyl-containing polyfunctional (meth)acrylates can form a good cross-linking structure, resulting in good physical properties such as stain resistance and abrasion resistance.

[0177] The number of hydroxyl-containing polyfunctional (meth)acrylates (B) is preferably 3 or less, more preferably 2 or less, and even more preferably 1. The number of (meth)acryloyl groups in the hydroxyl-containing polyfunctional (meth)acrylates (B) is preferably 8 or less, more preferably 6 or less.

[0178] In the manufacture of UV-curable oligomers, only one of these hydroxyl-containing polyfunctional (meth)acrylates (B) may be used, or two or more may be used together.

[0179] From the viewpoint of the coating strength of the cured film, the hydroxyl-containing polyfunctional (meth)acrylate (B) is preferably one with one hydroxyl group and three or more but less than five (meth)acryloyl groups, such as pentaerythritol pentamethacrylate or pentaerythritol trimethacrylate. From the viewpoint of improving the mechanical strength of the cured film by forming a good crosslinking structure, the hydroxyl-containing polyfunctional (meth)acrylate (B) is preferably pentaerythritol pentamethacrylate.

[0180] <Water-soluble compounds>

[0181] (Compound (C'))

[0182] Compound (C') is a water-soluble compound that can bond with polyisocyanate compound (A).

[0183] To ensure good water dispersibility, compound (C') is preferably a compound containing a hydroxyl terminus.

[0184] As the compound (C'), water-soluble polymers can be listed as described above, among which polyalkylene glycols (C) are particularly preferred.

[0185] As a polyalkylene glycol (C), there is no limitation, but a monosubstituted structure is preferred. That is, it is preferable that one hydroxyl group of the glycol is substituted. As a substituted structure, a structure that is not bonded to isocyanate is preferred.

[0186] Polyalkylene glycols (C) can also be a mixture of monosubstituted and non-monosubstituted compounds.

[0187] The structure of the monosubstituted product is not limited. From the viewpoint of making the UV-curable oligomer nonionic, polyalkylene glycol monosubstituted ether is preferred, more preferably polyethylene glycol monosubstituted ether, polytrimethylene glycol monosubstituted ether or polypropylene glycol monosubstituted ether, and even more preferably polyethylene glycol monosubstituted ether.

[0188] Among polyalkylene glycol monosubstituted ethers, polyalkylene glycol monosubstituted ethers without ionic substituents in the ether portion are more preferably those. As a polyalkylene glycol monosubstituted ether, for example, a polyalkylene glycol monosubstituted ether represented by the following formula (1) is further preferred.

[0189] [Chemical Formula 2]

[0190]

[0191] (In formula (1), X is an alkylene group. Y is any one of alkyl, (meth)acryloyl, allyl, acyl, or hydrogen atom. n is an integer greater than 2.)

[0192] In formula (1), X is preferably an alkylene group with 1 or more but less than 3 carbon atoms, and more preferably ethylene, trimethylene, or propylene. From the viewpoint of pigment dispersion stability or storage stability at high temperatures, X in formula (1) is further preferably ethylene.

[0193] From the viewpoint of coating strength, Y is preferably (meth)acryloyl, allyl or acyl, more preferably allyl.

[0194] From the viewpoint of the coating strength of the obtained cured film, n in formula (1) is generally 2 or more, preferably 5 or more, more preferably 6 or more, and generally 500 or less, preferably 100 or less, more preferably 50 or less.

[0195] In the manufacture of UV-curable oligomers, only one of these polyalkylene glycols (C) may be used, or two or more may be used together.

[0196] Polyalkylene glycols (C) can be mixtures of different molecular weights (n in formula (1) are different compounds).

[0197] <Average Particle Size>

[0198] In the inkjet ink of the present invention, the polymeric compound preferably exists in the form of particles.

[0199] If the polymeric compound exists in the form of particles in the inkjet ink, the ink will not excessively penetrate the recording medium, even if the recording medium is absorbent, and will tend to remain near the surface. As a result, the reduction in image density can be suppressed, and a coating with excellent wash fastness can be formed.

[0200] In particular, the polymerizable compound is more preferably present in the inkjet ink in the form of particles with an average particle size of 10 nm or more and 200 nm or less, and even more preferably in the form of particles with an average particle size of 20 nm or more and 150 nm or less.

[0201] If the average particle size of the polymerizable compound is within the above range, the dispersion stability is good.

[0202] The average particle size of polymeric compounds is, for example, the volume average particle size (D) measured by a particle size analyzer based on dynamic light scattering. 50 ).

[0203] In the embodiments described later, the average particle size of the polymeric compound particles in the aqueous dispersion of the polymeric compound was measured, and the average particle size of the polymeric compound particles in the aqueous dispersion was approximately equal to the average particle size of the polymeric compound particles in the ink.

[0204] In this invention, as long as the polymeric compound exists in the form of particles, even if there is aggregation, even if other substances are contained within the particles, it is still included in the aforementioned state of "existing in the form of particles".

[0205] The average particle size of the polymeric compound mentioned above refers to the particle size (primary particle size) of the polymeric compound particles.

[0206] From the viewpoint of improving the water resistance of the cured product, the inkjet ink of the present invention preferably contains a water-insoluble polymeric compound. Here, "water-insoluble" means that the solubility of the polymeric compound in water at 25°C is less than 0.01 g / mL. The solubility in water can be adjusted by the type and content of hydrophilic functional groups possessed by the polymeric compound.

[0207] Non-water-soluble polymeric compounds can exist as particles in aqueous media. However, aqueous inks containing these polymeric compound particles are prone to nozzle clogging and may degrade ink ejection stability. This is because the polymeric compounds are only dispersed in the aqueous media, not dissolved, and therefore easily precipitate at the nozzle tip of the inkjet head. Furthermore, if they solidify at the ejection point of the nozzle, they are difficult to rinse with water.

[0208] Therefore, when polymeric compounds exist in the form of particles in inkjet ink, it is particularly important to suppress the evaporation of the aqueous medium in the ink application process [a] so that the effects of the present invention can be enjoyed more effectively.

[0209] The components contained in the inkjet ink of the present invention, excluding polymeric compounds, will be described below.

[0210] [Coloring agent]

[0211] The inkjet ink used in the inkjet recording method of the present invention may also contain a colorant.

[0212] As a colorant for inkjet ink, various dyes or pigments known as colorants for ink can be used. From the viewpoint of the long-term preservation durability of printed images after exposure to active energy rays, the inkjet ink of the present invention preferably contains pigments as colorants.

[0213] <Dye>

[0214] There are no particular limitations on the dyes that can be used in this invention, and examples include: water-soluble dyes such as acid dyes, direct dyes, and reactive dyes, as well as disperse dyes. Among them, anionic dyes are preferred.

[0215] (Water-soluble dyes)

[0216] Examples of water-soluble dyes include: azo dyes, methylene dyes, azomethyl alkali dyes, xanthan dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, etc.

[0217] Pigments

[0218] As pigments, conventionally known organic and inorganic pigments can be used. Examples include: azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelated azo pigments; phthalocyanine pigments, perylene and perylene pigments; anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindole pigments, isoindolineone pigments, and quinophthalone pigments; dye lakes such as basic dye lakes and acid dye lakes; organic pigments such as nitro pigments, nitroso pigments, aniline black, and solar fluorescent pigments; and inorganic pigments such as carbon black, titanium dioxide, and iron oxide pigments. Anionic pigments are preferred as pigments.

[0219] These dyes and pigments can be used in single or multiple ways.

[0220] [Aqueous medium]

[0221] The inkjet ink of this invention is an aqueous ink. "Aqueous ink" refers to ink containing an aqueous medium. An aqueous medium refers to water and / or water-soluble organic solvents.

[0222] The aqueous medium used in this invention is preferably water, or a mixture of water and a water-soluble organic solvent.

[0223] Water-soluble organic solvents can be categorized into two types: those that function as moisturizing solvents to improve the humidification and wetting properties of inks, and those that function as water-based media to adjust the viscosity, improve operability, and sprayability of inks. There is no clear distinction between the two; water-soluble organic solvents used as moisturizing solvents also function as water-based media.

[0224] In this invention, a water-soluble organic solvent refers to a compound that is soluble in water. The solubility of a water-soluble organic solvent in water is not limited, but compounds that can dissolve in water in any proportion are preferred. Furthermore, even compounds that are difficult to use as solvents on their own (e.g., compounds that are solid at room temperature or have high viscosity) are included in the category of water-soluble organic solvents, as long as they can be used as solvents by uniformly mixing with water.

[0225] Examples of water-soluble organic solvents include: polyols; polyol alkyl ethers, polyol aryl ethers, and other ethers; nitrogen-containing heterocyclic compounds; amides; amines; and sulfur-containing compounds.

[0226] Specific examples of water-soluble organic solvents include: ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3... Polyols including hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-1,3,5-pentanetriol (petriol), etc.; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, etc. Alkyl ethers of polyols such as monomethyl ethers of alcohol, monoethyl ethers of diethylene glycol, monobutyl ethers of diethylene glycol, ethylmethyl ethers of diethylene glycol, monomethyl ethers of tetraethylene glycol, monomethyl ethers of propylene glycol, and monoethyl ethers of propylene glycol; aryl ethers of polyols such as monophenyl ethers of ethylene glycol and monobenzyl ethers of ethylene glycol; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanolamine; and propylene carbonate and ethylene carbonate.

[0227] Among them, propylene glycol and diethylene glycol ethyl methyl ether are preferred.

[0228] Considering that it not only functions as a moisturizing solvent but also provides good drying properties, it is preferable to use an organic solvent with a boiling point below 250°C as a water-soluble organic solvent.

[0229] As a water-soluble organic solvent, polyol compounds and glycol ether compounds with 8 or more carbon atoms can also be preferred.

[0230] Specific examples of polyols with 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

[0231] Specific examples of glycol ether compounds include: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, and other polyol alkyl ethers; ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and other polyol aryl ethers.

[0232] These water-soluble organic solvents can be used alone or in combination of two or more.

[0233] [Polymerization initiator]

[0234] The inkjet ink of the present invention contains a polymerization initiator.

[0235] A polymerization initiator is a photoradical polymerization initiator that generates free radicals as active species by utilizing the energy of light (ultraviolet light) received from irradiation with active energy rays, thus initiating the photopolymerization of polymerizable compounds. As a result, ink present on the surface of the recording medium can be solidified to form an image.

[0236] The polymerization initiator can be contained in the ink in a state where it is not encapsulated within the polymerizable compound, or in a state where it is encapsulated within particles of the polymerizable compound. Furthermore, it can be contained in the ink in both of these states.

[0237] As a polymerization initiator, it can be a fat-soluble polymerization initiator (hereinafter, sometimes referred to as "fat-soluble initiator") or a water-soluble polymerization initiator (hereinafter, sometimes referred to as "water-soluble initiator").

[0238] Here, "lipid-soluble initiator" refers to a polymerization initiator that is miscible with polymeric compounds such as UV-curable oligomers or soluble in organic solvents. "Water-soluble initiator" refers to an initiator that dissolves in water at a concentration of 1% or more by mass. The same applies to "lipid-soluble sensitizer" and "water-soluble sensitizer" as described later.

[0239] The polymerization initiators used in this invention are not limited to the following, but may include, for example: aromatic ketones, acylphosphine oxide compounds, aromatic ononium salt compounds, organic peroxides, thiolated compounds (thioxanthone compounds, sulfur-containing phenyl compounds), α-aminoalkylphenyl ketone compounds, hexaaryl biimidazole compounds, ketoxime ester compounds, borate compounds, azadinium compounds, metallocene compounds, active ester compounds, compounds having carbon-halogen bonds, and alkylamine compounds.

[0240] Among these, the polymerization initiator preferably includes at least one of an acylphosphine oxide compound and a thioxanthone compound. Using such a polymerization initiator tends to result in superior ink curability.

[0241] As a lipid-soluble polymerization initiator, it is not limited to the following, but may include, for example: acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p'-bis(diethylamino)benzophenone, Mischel ketone, benzoin, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzyl methyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}2-methylpropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1, 2-Dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butane-1-one, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]2-morpholinopropane-1-one, thioxanone, 2-chlorothioxanone, 2-methylthioxanone, 2-isopropylthioxanone, 4-isopropylthioxanone, 2-hydroxy-2-methyl-1-phenyl-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, methyl benzoylformate, azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide, etc.

[0242] As a water-soluble polymerization initiator, it is not limited to the following, but examples include: 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, sodium phenyl(2,4,6-trimethylbenzoyl)phosphonate, 2-(3-dimethylamino-2-hydroxypropoxy)-3,4-dimethyl-9H-thioxanthone-9-one methyl chloride, etc.

[0243] Commercially available polymerization initiators include, for example, GENOPOL TX-2 manufactured by RAHN Corporation, and Irgacure (registered trademark) 369, Irgacure (registered trademark) 500, and Irgacure (registered trademark) 2959 manufactured by BASF Japan Corporation.

[0244] Polymerization initiators can be used alone or in combination with two or more. For example, lipid-soluble initiators and water-soluble initiators can be used together, with the lipid-soluble initiator encapsulated within particles of polymeric compounds such as UV-curable oligomers, and the water-soluble initiator dissolved in an aqueous medium.

[0245] In addition to the photoradical polymerization initiator described above, the thermal radical polymerization initiator can also be used as a polymerization initiator.

[0246] [surfactants]

[0247] To ensure the flatness of the resulting coating and its wettability with the substrate, the inkjet ink of the present invention preferably contains a surfactant.

[0248] As a surfactant, any one of the following can be used: organosilicon surfactant, fluorinated surfactant, amphoteric surfactant, nonionic surfactant, or anionic surfactant.

[0249] There are no particular limitations on silicone-based surfactants; they can be selected appropriately depending on the purpose. Among them, silicone-based surfactants that do not decompose at high pH are preferred, such as side-chain modified polydimethylsiloxanes, bi-terminated polydimethylsiloxanes, mono-terminated polydimethylsiloxanes, and bi-terminated side-chain polydimethylsiloxanes. Silicone-based surfactants with polyoxyethylene or polyoxyethylene polyoxypropylene groups as modifying groups exhibit excellent properties as aqueous surfactants and are therefore particularly preferred.

[0250] Polyether-modified silicone surfactants can also be used as silicone surfactants. Examples of polyether-modified silicone surfactants include compounds formed by introducing a polyepoxide structure into the Si side chain of a dimethylsiloxane.

[0251] As a fluorinated surfactant, it is preferred to be a compound with 2 or more and 16 or less carbon atoms that have been fluorinated, and more preferably a compound with 4 or more and 16 or less carbon atoms that have been fluorinated.

[0252] As fluorinated surfactants, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl epoxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain have low foaming properties and are therefore preferred.

[0253] Examples of perfluoroalkyl sulfonic acid compounds include: perfluoroalkyl sulfonic acids, perfluoroalkyl sulfonates, etc.

[0254] Examples of perfluoroalkyl carboxylic acid compounds include: perfluoroalkyl carboxylic acids, perfluoroalkyl carboxylate salts, etc.

[0255] Examples of perfluoroalkyl phosphate compounds include: perfluoroalkyl phosphates, perfluoroalkyl phosphate salts, etc.

[0256] Examples of perfluoroalkyl epoxide adducts include perfluoroalkyl ethylene oxide adducts.

[0257] Examples of polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain include: sulfate salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain, and salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain.

[0258] The balancing ions of the salts in these fluorinated surfactants can be listed as: Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, etc.

[0259] Among them, polyoxyalkylene ether polymer compounds with perfluoroalkyl ether groups on the side chains have particularly low foaming properties, and are therefore more preferred, especially preferred, to be fluorinated surfactants represented by the following formulas (3A) and (3B).

[0260] CF3CF2(CF2CF2) s -CH2CH2O(CH2CH2O) t H……(3A)

[0261] In the compound represented by formula (3A), in order to impart water solubility, s is preferably an integer of 0 or more and 10 or less, and t is preferably an integer of 0 or more and 40 or less.

[0262] C r F 2r+1 -CH2CH(OH)CH2-O-(CH2CH2O) c -Z……(3B)

[0263] In the compound represented by formula (3B), Z is H or C. d F 2d+1 CH2CH(OH)CH2-C e F 2e+1 Or C f H 2f+1 C d F 2d+1 In this context, d is an integer greater than 1 and less than 6. CH2CH(OH)CH2-C e F 2e+1 In C, 'e' is an integer greater than 4 and less than 6. f H 2f+1 In this context, f is an integer greater than 1 and less than 19. r is an integer greater than 1 and less than 6. c is an integer greater than 4 and less than 14.

[0264] Commercially available products can be used as fluorinated surfactants. Examples of commercially available products include: Surflon (registered trademark) S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.); Fluorad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Co., Ltd.); MEGAFACE F-470, F-1405, F-474 (all manufactured by DIC Corporation); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by NEOS Corporation); Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA); NOIGEN FN-1287 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.); UNIDYNE DSN-403N (manufactured by DAIKIN Industrial Co., Ltd.), LE-604, LE-605, LE-606, LE-607 (Kyoeisha Chemical Co., Ltd.), etc.

[0265] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

[0266] Examples of nonionic surfactants include: polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, ethynyl alcohol derivatives, and ethynyl diol derivatives.

[0267] Examples of anionic surfactants include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, and polyoxyethylene alkyl ether sulfate.

[0268] They can be used individually or in combination with two or more.

[0269] As mentioned above, there are no particular limitations on silicone surfactants, and they can be appropriately selected according to the purpose. Polyether-modified silicone surfactants with polyoxyethylene, polyoxyethylene and polyoxypropylene groups as modifying groups exhibit good properties as aqueous surfactants and are therefore listed as particularly preferred silicone surfactants.

[0270] As such surfactants, appropriately synthesized surfactants or commercially available products can be used. Commercially available products, for example, can be obtained from BYK JAPAN Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nihon Emulsion Co., Ltd., and Kyoei Chemical Co., Ltd.

[0271] There are no particular limitations on the type of polyether-modified organosilicon surfactant, and it can be selected appropriately according to the purpose. For example, compounds formed by introducing a polyepoxide structure into the Si side chain of dimethylpolysiloxane, represented by the following formula (2), can be listed.

[0272] [Chemical Formula 3]

[0273]

[0274] (In equation (2), p, q, a, and b represent integers. R and R' represent hydrocarbon groups.)

[0275] As a polyether-modified silicone surfactant, commercially available products can be used. Commercially available products include, for example: KF-618, KF-642, KF-643 (Shin-Etsu Chemical Industry Co., Ltd.), SAG001, SAG002, SAG003, SAG005, SAG503, SAG008 (Nihon Chemical Industry Co., Ltd.), EMLEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-347, BYK-348, BYK-349 (BYK JAPAN Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba). Silicon Co., Ltd.), etc.

[0276] [Sensitizer]

[0277] The inkjet ink of this invention may also contain sensitizers.

[0278] If the sensitizer and polymerization initiator coexist in the ink, the sensitizer in the system will absorb active energy rays and be in an excited state. By contacting the polymerization initiator, it will promote the decomposition of the polymerization initiator and enable a more sensitive curing reaction.

[0279] Like polymerization initiators, sensitizers can be either lipid-soluble or water-soluble. If the sensitizer is lipid-soluble, it can be encapsulated within particles of polymeric compounds such as UV-curable oligomers.

[0280] As sensitizers, the following can be used: aliphatic amines, cyclic amine compounds such as amines with aromatic groups or piperidine, thioxanthone compounds, alkoxyanthracene compounds, urea compounds such as o-tolylthiourea, sulfur compounds such as sodium diethylthiophosphate or soluble salts of aromatic sulfinic acids, nitrile compounds such as N,N'-disubstituted p-aminobenzyl nitrile, phosphorus compounds such as tri-n-butylphosphine or sodium diethyldithiophosphate, mistrone, N-nitrosohydroxyamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds, nitrogen compounds such as formaldehyde or acetaldehyde condensates with diamines, etc.

[0281] These sensitizers can be used alone or in combination with two or more.

[0282] [Other resin components]

[0283] In addition to the components described above, the inkjet ink of the present invention may also contain, as needed, any oligomer components other than polymeric compounds, any resin components, and any monomer components (collectively referred to as "other resin components"). Other resin components may be encapsulated within the particles of polymeric compounds, dissolved in an aqueous medium, or dispersed alone or compounded with other components in the ink.

[0284] [Other additives]

[0285] In addition to the above-mentioned components, the inkjet ink of the present invention may also contain other additives as needed.

[0286] Other additives include, for example, anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, mildew inhibitors, rust inhibitors, pH adjusters, viscosity adjusters, dispersants, dispersion stabilizers, defoamers, solid wetting agents, chelating agents, and other well-known additives. These various additives can be added directly after ink preparation or during ink preparation.

[0287] For other additives, please refer to paragraphs 0088 to 0096 of Japanese Patent Application Publication No. 2010-65205 and paragraphs 0083 to 0090 of Japanese Patent Application Publication No. 2010-70669.

[0288] [Content of each component]

[0289] The water content in the inkjet ink of the present invention is not particularly limited and can be appropriately selected according to the purpose. Considering the drying properties and ejection reliability of the ink, the water content in the inkjet ink of the present invention is generally 10% by mass or more, preferably 20% by mass or more, more preferably 40% by mass or more, and generally 90% by mass or less, preferably 80% by mass or less.

[0290] When the inkjet ink of the present invention contains a water-soluble organic solvent, its content (the total content of the water-soluble organic solvent used as a moisturizing solvent and the water-soluble organic solvent used as an aqueous medium) is not particularly limited, and can be appropriately selected according to the type of water-soluble organic solvent used and the purpose. Considering factors such as drying performance, ejection reliability, and wettability with the substrate, the content of water-soluble organic solvent in the inkjet ink of the present invention is generally 10% by mass or more, and generally 50% by mass or less, preferably 40% by mass or less.

[0291] The content of volatile components relative to the total amount of inkjet ink of the present invention is preferably 70% by mass or more, more preferably 75% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less.

[0292] If the content of volatile components is above the lower limit mentioned above, the spraying reliability is high. If the content of volatile components is below the upper limit mentioned above, the coating strength can be enhanced.

[0293] The volatile components in the inkjet ink of the present invention refer to the components that are reduced by more than 90% when 1g of inkjet ink is placed on an aluminum disk with a diameter of 10cm and dried at 80°C for 4 hours, compared with those before drying.

[0294] From the viewpoint of drying performance and ejection reliability, the inkjet ink of the present invention is prepared such that the concentration of all solid components other than water and / or water-soluble organic solvents (i.e., aqueous media) is typically 5% by mass or more, preferably 7% by mass or more, more preferably 9% by mass or more, and typically 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less.

[0295] From the viewpoint of improving drying performance and ejection performance, when using a mixture of water and a water-soluble organic solvent as the aqueous medium of the inkjet ink of the present invention, the ratio of water to water-soluble organic solvent (the total of the water-soluble organic solvent used as a moisturizing solvent and the water-soluble organic solvent used as an aqueous medium) is preferably 1:0.05 to 1:1.5 (mass ratio), preferably 1:0.1 to 1:1.2 (mass ratio), and more preferably 1:0.15 to 1:1.1 (mass ratio).

[0296] From the viewpoint of the resulting printing coating performance and the curing properties of active energy rays, the content of polymeric compounds in the inkjet ink of the present invention is generally 3% by mass or more, preferably 5% by mass or more, and more preferably 7% by mass or more. On the other hand, from the viewpoint of ejection stability, the content of polymeric compounds in the inkjet ink of the present invention is generally 20% by mass or less, preferably 15% by mass or less, and more preferably 12% by mass or less.

[0297] From the same point of view, the content of polymeric compounds in all solid components of the inkjet ink of the present invention is generally 30% by mass or more, preferably 50% by mass or more, and generally 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less.

[0298] Considering the improvement of image density, good fixing properties, and ejection stability, the content of colorant in the inkjet ink of the present invention is usually 0.1% by mass or more, preferably 1% by mass or more, and usually 8% by mass or less, preferably 6% by mass or less.

[0299] From the same point of view, the content of colorant in all solid components of the inkjet ink of the present invention is generally 1% by mass or more, preferably 5% by mass or more, and generally 40% by mass or less, preferably 30% by mass or less.

[0300] The content of polymerization initiator in the inkjet ink of the present invention is typically 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and typically 8% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. By using a polymerization initiator content within this range, the curing speed can be sufficiently improved, and undissolved residues of the polymerization initiator and coloring originating from the polymerization initiator can be avoided.

[0301] From the same point of view, the content of polymerization initiator in all solid components of the inkjet ink of the present invention is generally 0.5% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and generally 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less.

[0302] When the inkjet ink of the present invention contains a surfactant, its content is not particularly limited and can be appropriately selected according to the purpose. Considering the aspects of excellent wettability, ejection stability and improved image quality, the content of surfactant in the ink is usually 0.001% by mass or more, preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less.

[0303] From the same point of view, the content of surfactant in all solid components of the inkjet ink of the present invention is generally 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and generally 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

[0304] When the inkjet ink of the present invention contains a sensitizer, its content is generally 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and generally 4% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.7% by mass or less. If the content of the sensitizer is within the above range, the effect brought by the sensitizer can be fully obtained.

[0305] From the same point of view, the content of sensitizer in all solid components of the inkjet ink of the present invention is generally 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and generally 8% by mass or less, preferably 6% by mass or less, more preferably 5% by mass or less.

[0306] [Viscosity of inkjet ink]

[0307] The viscosity of the inkjet ink of the present invention at 25°C is preferably 25 mPa·sec or less, more preferably 20 mPa·sec or less, and even more preferably 10 mPa·sec or less. The lower limit of the viscosity of the inkjet ink of the present invention at 25°C is not particularly limited, but is preferably 1 mPa·sec or more, more preferably 2 mPa·sec or more, and even more preferably 5 mPa·sec or more.

[0308] The viscosity of the inkjet ink can be measured using a digital viscometer DV-I+ manufactured by Brookfield.

[0309] Inkjet Recording Device

[0310] The inkjet recording device of the present invention can be preferably used in various recording devices that utilize inkjet recording, such as printers, fax machines, copiers, printer / fax / copier all-in-one machines, 3D modeling devices, etc.

[0311] In this invention, the recording device refers to a device capable of ejecting ink, various processing liquids, etc., onto the medium being recorded.

[0312] The recording device may include not only the ink ejection head, but also units related to the supply, transport, and paper discharge of the recorded medium, as well as devices referred to as pre-processing devices and post-processing devices.

[0313] An inkjet recording apparatus (hereinafter sometimes referred to as "inkjet recording apparatus 1") according to one embodiment of the present invention is characterized in that it is used to record images onto an absorbent recording medium and comprises: an ink application unit [c] for applying inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the absorbent recording medium without heating the absorbent recording medium; an irradiation unit [d] for irradiating the inkjet ink applied to the absorbent recording medium with active energy rays; and a heating unit [e] for heating the absorbent recording medium while irradiating the active energy rays, wherein the irradiation unit [d] and the heating unit [e] can be controlled independently.

[0314] Another embodiment of the inkjet recording apparatus of the present invention (hereinafter, sometimes referred to as "inkjet recording apparatus 2") is characterized in that it is used to record images onto a recording medium and comprises: an ink application unit [c] for applying inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the recording medium without heating the recording medium; an irradiation unit [d] for irradiating the inkjet ink applied to the recording medium with active energy rays; and a heating unit [e] for heating the recording medium while irradiating the active energy rays, wherein the irradiation unit [d] and the heating unit [e] can be controlled independently, and the polymerizable compound exists in the inkjet ink in the form of particles.

[0315] Alternatively, the inkjet recording apparatus 1 and inkjet recording apparatus 2 of the present invention (hereinafter, they are sometimes collectively referred to as "the inkjet recording apparatus of the present invention") may further include a drying unit without heating to promote the evaporation of the aqueous medium contained in the ink. The drying unit may include, for example, a unit for drying the printing surface and the back surface of the recorded medium.

[0316] As described above, the irradiation unit [d] in the inkjet recording apparatus of the present invention that irradiates active energy rays can be a unit using a light source such as a halogen lamp, a metal halide lamp, an LED, or an LD. Among these, a light-emitting diode having a peak emission wavelength in the range of 350 to 420 nm is preferred.

[0317] The preferred configurations of the recording medium, ink supply unit [c], heating unit [e], and inkjet ink are the same as those described in the aforementioned inkjet recording method.

[0318] The inkjet recording apparatus of the present invention is not limited to inkjet recording apparatuses that visualize meaningful images such as text and graphics using ink. For example, it also includes inkjet recording apparatuses that form geometric patterns or other designs, and inkjet recording apparatuses that shape three-dimensional images.

[0319] In addition, the recording apparatus includes not only desktop recording devices, but also wide-format recording devices capable of printing on A0-sized recording media, such as continuous printers that can use continuous paper wound into rolls as recording media.

[0320] Furthermore, the recording method or the irradiation method of the active energy ray, unless otherwise specified, includes either the reciprocating method, in which recording is performed while moving the serial head, or the line method, in which recording is performed using a line head. For example, Japanese Patent Application Publication No. 2022-181182 and Japanese Patent Application Publication No. 2010-280828 may be referred to as recording devices using the reciprocating method.

[0321] "use"

[0322] The inkjet ink used in the inkjet recording method and inkjet recording device of the present invention is water-based, thus providing excellent environmental and safety features.

[0323] According to the inkjet recording method and apparatus of the present invention, it is possible to use water-based inks with excellent environmental and safety properties to form printed coatings with excellent film properties, especially high wash fastness.

[0324] Therefore, the inkjet recording method and inkjet recording apparatus of the present invention can be preferably used for various applications such as fabrics for clothing such as T-shirts, textiles that may be wetted, wallpaper for interior decoration, and home décor.

[0325] Example

[0326] The following describes one embodiment of the present invention. However, the present invention is not limited to this embodiment.

[0327] [Ink Preparation]

[0328] <Preparation of Aqueous Dispersions of Polymerizing Compounds>

[0329] A non-water-soluble polymeric compound (UV-curable oligomer) is produced by reacting 0.4 mol of hexamethylene diisocyanate trimer, 0.8 mol of pentaerythritol pentaacrylate, and 0.4 mol of polyethylene glycol monoallyl ether (n=30~40 in the formula (1)).

[0330] The polymerizable compound was mixed with a lipid-soluble initiator (GENOPOL TX-2 manufactured by RAHN) at the ratios shown in Table 1 at 60°C. Ion-exchanged water preheated to 60°C was added dropwise while stirring until the concentration of the solid component reached 20% by mass, thus obtaining an aqueous dispersion.

[0331] The average particle size (D) of the UV-curable oligomer particles in the aqueous dispersion 50 The particle size distribution was measured using a MICROTRAC WAVEII-EX150 particle size analyzer (manufactured by Microtrac BEL Co., Ltd.), and the result was 29 nm.

[0332] <Preparation of Ink 1>

[0333] The ink 1 is obtained by adding and mixing ion-exchanged water, the aqueous dispersion of the polymeric compound, propylene glycol (PG) and diethylene glycol ethyl methyl ether (EM) as water-soluble organic solvents, water-soluble initiator 1, water-soluble sensitizer 1, BYK-347 and BYK-349 (both manufactured by BYK JAPAN) as surfactants, and a CI pigment blue 15:3 dispersion (referred to as "Cy" in Table 1) as pigment dispersion, in the composition ratios shown in Table 1.

[0334] The viscosity of ink 1 at 25°C is 8 mPa·s.

[0335] <Preparation of Ink 2 to Ink 4>

[0336] By changing the type and proportion of the pigment dispersion, the proportion of the water-soluble sensitizer, and the type and proportion of the surfactant as shown in Table 1 below, inks 2 to 4 are obtained in the same manner as ink 1.

[0337] [Pigment Dispersion]

[0338] CI Pigment Red 122 Dispersion (Ma in Table 1).

[0339] CI Pigment Yellow 155 Dispersion (Ye in Table 1).

[0340] CI Pigment Black 7 Dispersion (Bk in Table 1).

[0341] The viscosities of inks 2 to 4 at 25°C are as follows.

[0342] Ink 2: Viscosity = 10 mPa·s.

[0343] Ink liquid 3: viscosity = 7 mPa·s.

[0344] Ink liquid 4: viscosity = 7 mPa·s.

[0345] The percentage of each component in Table 1 indicates the percentage of that component contained in an aqueous dispersion or solution when the component is prepared as such.

[0346] [Table 1]

[0347]

[0348] [Examples 1-6, Comparative Examples 1-3]

[0349] In a UV inkjet printer, ink 1 to ink 4, which serve as inkjet ink, and cotton fabric, which serves as the recording medium, are installed.

[0350] Process [a]: Perform the ink application process with the following settings.

[0351] (Setting of the ink application process (ink application unit [c]))

[0352] Resolution: 600×600dpi.

[0353] Number of passes: 8.

[0354] Image: A 5×8cm field image.

[0355] Then, as step [b] (i.e., the irradiation step), the fabric after the ink application step is completed is placed at a current density of 2 W / cm² at the temperature shown in Table 2. 2 After 10 seconds of heating, the LED (irradiation unit [d]) with a peak emission wavelength of 385 nm was used as the active energy ray source, and the illuminance was adjusted to the level shown in Table 2, irradiating with 7 J / cm². 2 Ultraviolet radiation that provides energy.

[0356] However, in Comparative Examples 1 to 3, heating using a heating plate was not performed. Without heating, the temperature of the fabric irradiated with active energy rays was room temperature (23°C).

[0357] [Evaluation of wash fastness]

[0358] The wash fastness of the printed coating obtained through the above process is evaluated using the following method.

[0359] For the fabrics with printed coatings obtained in Examples 1 to 6 and Comparative Examples 1 to 3, they were washed in a washing machine for 50 minutes. The change in image density (ΔE) before and after washing was determined using a spectrophotometer (X-Rite, X-rite eXact advance) and evaluated as follows. ΔE was calculated using the following formula.

[0360] [Formula 1]

[0361]

[0362] ◎: ΔE for each color is below 2.0, which is excellent in practical applications.

[0363] ○: The ΔE for each color is below 3.0, which poses no problem in practical applications.

[0364] ×: Colors with ΔE greater than 3.0 have problems in practical applications.

[0365] The evaluation results are shown in Table 2.

[0366] The printed coating portion in Examples 1 to 6 and Comparative Examples 1 to 3 had no hardness or stiffness and had the same texture as the unprinted fabric.

[0367] [Table 2]

[0368]

[0369] As shown in Table 2, the inkjet recording method and inkjet recording apparatus of the present invention can form printed images with high wash fastness and excellent coating strength while maintaining stable inkjet output.

[0370] It should be noted that in the above embodiments, inks 1 to 4, which are common to polymerizable compounds and polymerization initiators, were used. However, considering the mechanism of maintaining stable inkjet ejection through process [a] and the mechanism of suppressing the penetration of inkjet ink into the recorded medium through process [b], which results in improved wash fastness, the same effect can be expected even with other inkjet inks.

[0371] The present invention has been described in detail using specific methods, but it will be apparent to those skilled in the art that various modifications can be made without departing from the intent and scope of the invention.

[0372] This application is based on Japanese Patent Application No. 2023-193822, filed on November 14, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An inkjet recording method comprising the steps [a] and [b], wherein in step [a] the recording medium is not heated, and in step [b] the recording medium is heated by a heating unit, wherein the recording medium is an absorbent recording medium. Process [a]: Ink application process, which applies inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium. Process [b]: Irradiation process, wherein the inkjet ink imparted to the recording medium by at least process [a] is irradiated with active energy rays controlled by a unit different from the heating unit.

2. An inkjet recording method comprising the following steps [a] and [b], wherein in step [a] the recording medium is not heated, and in step [b] the recording medium is heated by a heating unit, wherein the polymeric compound in step [a] exists in the form of particles in the inkjet ink. Process [a]: Ink application process, which applies inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to the recording medium. Process [b]: Irradiation process, wherein the inkjet ink imparted to the recording medium by at least process [a] is irradiated with active energy rays controlled by a unit different from the heating unit.

3. The inkjet recording method according to claim 1 or 2, wherein, The light source for the active energy rays is a light-emitting diode with a peak emission wavelength in the range of 350 to 420 nm.

4. The inkjet recording method according to claim 1, wherein, The absorbent recording medium is cloth.

5. The inkjet recording method according to claim 2, wherein, The average particle size is greater than 10 nm and less than 200 nm.

6. The inkjet recording method according to claim 1 or 2, wherein, The polymeric compound contains (meth)acrylate compounds.

7. The inkjet recording method according to claim 1 or 2, wherein, The heating temperature of the recorded medium in step [b] is above 30°C and below 70°C.

8. The inkjet recording method according to claim 1 or 2, wherein, The heating element is used as the heating unit.

9. The inkjet recording method according to claim 1 or 2, wherein, Heating of the recorded medium in the irradiation process [b] from the side opposite to the ink-spraying surface.

10. An inkjet recording apparatus for recording images onto an absorbent recording medium, the inkjet recording apparatus comprising: The ink delivery unit [c] delivers inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the absorbent recording medium without heating it. The irradiation unit [d] irradiates the inkjet ink imparted to the absorbent recording medium with active energy rays; and The heating unit [e] heats the absorbent recording medium when irradiated with the active energy rays. The irradiation unit [d] and the heating unit [e] can be controlled independently.

11. An inkjet recording apparatus for recording images onto a recording medium, the inkjet recording apparatus comprising: The ink delivery unit [c] delivers inkjet ink containing a polymerizable compound, a polymerization initiator, and water to the recording medium without heating it. The irradiation unit [d] irradiates the inkjet ink applied to the recording medium with active energy rays; and The heating unit [e] heats the recording medium when irradiated by the active energy rays. The irradiation unit [d] and the heating unit [e] can be controlled independently. The polymeric compound exists in the inkjet ink in the form of particles.

12. The inkjet recording apparatus according to claim 10 or 11, wherein, The light source for the active energy rays is a light-emitting diode with a peak emission wavelength in the range of 350 to 420 nm.

13. The inkjet recording apparatus according to claim 10, wherein, The absorbent recording medium is cloth.

14. The inkjet recording apparatus according to claim 11, wherein, The average particle size is greater than 10 nm and less than 200 nm.

15. The inkjet recording apparatus according to claim 10 or 11, wherein, The polymeric compound contains (meth)acrylate compounds.

16. The inkjet recording apparatus according to claim 10 or 11, wherein, The heating element is used as the heating unit [e].

17. The inkjet recording apparatus according to claim 10 or 11, wherein, The heating unit [e] is located on the absorbent recording medium or on the side of the recording medium opposite to the ink-applying surface.

Images