Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/10—Printing inks based on artificial resins
  • C09D11/101—Inks specially adapted for printing processes involving curing by wave energy or particle radiation, e.g. with UV-curing following the printing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/0011—Pre-treatment or treatment during printing of the recording material, e.g. heating, irradiating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
  • B41M7/0081—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock using electromagnetic radiation or waves, e.g. ultraviolet radiation, electron beams
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M7/00—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock
  • B41M7/009—After-treatment of prints, e.g. heating, irradiating, setting of the ink, protection of the printed stock using thermal means, e.g. infrared radiation, heat
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/10—Printing inks based on artificial resins
  • C09D11/106—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C09D11/107—Printing inks based on artificial resins containing macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from unsaturated acids or derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/32—Inkjet printing inks characterised by colouring agents
  • C09D11/322—Pigment inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/30—Inkjet printing inks
  • C09D11/40—Ink-sets specially adapted for multi-colour inkjet printing

Definitions

• the present invention relates to an inkjet recording method.
• Inkjet recording methods have the following characteristics: they are easy to produce in full color, they are quiet, they produce high-resolution images at low cost, they allow high-speed printing, they can print on curved surfaces as well as flat surfaces, and they can easily print over large areas. For this reason, inkjet recording methods are not limited to personal use, but in recent years they have been rapidly spreading as commercial inkjet printers for sign applications, window films, posters, car wrapping, wallpaper, etc.
• the object of the present invention is to provide an inkjet recording method that can increase the strength of the printed coating film and improve the image quality obtained in inkjet recording using ultraviolet-curable water-based ink, and can obtain good image quality even when two or more colors of ink are used for simultaneous printing.
• the inventors have found that the above-mentioned problems can be solved by carrying out a first step of applying an ultraviolet-curable water-based ink to a recording medium and irradiating active energy rays simultaneously with the application of the ink, and a second step of irradiating the ink applied to the recording medium with active energy rays, and making the amount of light and maximum illuminance of the active energy rays irradiated per pass in the second step greater than the amount of light and maximum illuminance of the active energy rays irradiated per pass in the first step, or making the maximum illuminance of the active energy rays irradiated per pass in the first step smaller than a specific value.
• the present invention has been achieved based on these findings, and has the following gist.
• An inkjet recording method comprising a first step of applying an inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to a recording medium, and irradiating the recording medium with active energy rays simultaneously with the application of the inkjet ink, and a second step of irradiating the inkjet ink applied to the recording medium with active energy rays, wherein the amount of light and maximum illuminance of the active energy rays irradiated per pass in the second step are greater than the amount of light and maximum illuminance of the active energy rays irradiated per pass in the first step.
• An inkjet recording method comprising: a first step of applying an inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water to a recording medium, and irradiating the recording medium with active energy rays simultaneously with the application of the inkjet ink; and a second step of irradiating the inkjet ink applied to the recording medium with active energy rays, wherein the maximum illuminance of the active energy rays irradiated per pass in the first step is less than 1.0 W/ cm2 .
• a printed coating film having sufficient strength and good image quality can be formed in inkjet recording using an ultraviolet-curable water-based ink that is excellent in environmental friendliness and safety. Due to this improvement in image quality, good image quality can be obtained even when printing a mixed color image using inks of two or more colors simultaneously. Therefore, the coating strength and image quality in ink-jet recording are improved, and high-quality printed images can be obtained efficiently with good yield.
• the inkjet recording method of the present invention is an inkjet recording method including: a first step of applying an inkjet ink containing at least a polymerizable compound, a polymerization initiator, and water (hereinafter, may be referred to as "the inkjet ink of the present invention") to a recording medium, and irradiating the recording medium with active energy rays simultaneously with the application of the inkjet ink; and a second step of irradiating the inkjet ink applied to the recording medium with active energy rays.
• the amount of light (hereinafter, sometimes simply referred to as the "second step light amount”) and maximum illuminance (hereinafter, sometimes simply referred to as the “second step maximum illuminance”) of the active energy ray irradiated per pass in the second step are greater than the amount of light (hereinafter, sometimes simply referred to as the "first step light amount”) and maximum illuminance (hereinafter, sometimes simply referred to as the “first step maximum illuminance”) of the active energy ray irradiated per pass in the first step.
• the maximum irradiance of the active energy rays irradiated per pass in the first step is less than 1.0 W/ cm2 .
• the inkjet recording method of the present invention may further include other steps as necessary. For example, it may further include a drying step of drying and removing the solvent in the inkjet ink applied onto the recording medium. Furthermore, a pretreatment agent application step of applying a pretreatment agent to the recording medium may be included prior to the first step. However, it is preferable that the inkjet recording method of the present invention does not include a pretreatment agent application step of applying a pretreatment agent to the recording medium. In other words, in the present invention, a printing coating film having sufficient strength can be formed without carrying out a pretreatment agent application step prior to the first step. Therefore, one of the features of the present invention is that the pretreatment agent application step can be omitted.
• inkjet ink is applied to a recording medium and then irradiated with active energy rays
• the curing components in the ink (polymerizable compound and polymerization initiator) separate before exposure to active energy rays, and the curing reaction does not proceed sufficiently even when exposed to active energy rays.
• the printed coating that is formed does not have sufficient strength.
• the strength of the printed coating film can be increased by irradiating the ink with active energy rays at the same time as applying the ink, thereby immediately progressing the ink curing reaction, making it easier for the ink solvent to volatilize due to the heat of the curing reaction, and suppressing separation of the curing components in the ink.
• the ink is cured while a large amount of solvent remains in the ink, which can make it difficult to achieve both image quality and coating strength.
• weak irradiation is performed in the first step, in which ink is applied and active energy radiation is applied simultaneously, thereby thickening the ink on the recording medium as an incomplete cure and improving image quality.
• strong irradiation is performed in the second step, in which active energy radiation is irradiated in a state in which the solvent has been reduced, thereby improving the strength of the coating film and image quality.
• the inkjet ink of the present invention contained in the ink set is applied to a recording medium from, for example, an inkjet head of an inkjet printer, and at the same time, the recording medium is irradiated with active energy rays.
• the actinic radiation irradiation at the same time as the application of ink may be referred to as "simultaneous irradiation”.
• simultaneous irradiation means starting irradiation of active energy rays at the same time as the start of the inkjet ink application process, or starting irradiation of active energy rays within 10 seconds after the start of the inkjet ink application process.
• “Simultaneously with the start of the inkjet ink application process” more specifically means that the inkjet ink ejection operation and the active energy ray irradiation operation are performed simultaneously.
• the carriage is equipped with an inkjet head and an active energy ray irradiation unit, and the carriage is scanned while ejecting the inkjet ink and irradiating the active energy ray simultaneously corresponds to simultaneous irradiation in the present invention.
• the method for applying the ink-jet ink of the present invention is not particularly limited as long as it is a method that can apply the ink-jet ink in a desired image pattern.
• the ink-jet method employed in the present invention is a preferable method from the viewpoints of compactness of the recording apparatus and high-speed recording.
• inkjet ink is ejected onto a recording medium by applying energy, thereby forming a colored image.
• the amount of ink used in image formation is usually about 30 g/ m2 or less.
• the amount of ink ejected per pass is 1/8 of the ink amount, that is, about 3.75 g/m2 or less.
• the inkjet method is not particularly limited, and may be any of the well-known methods, such as a charge control method that uses electrostatic attraction to eject ink, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezoelectric element, and an acoustic inkjet method that converts an electrical signal into an acoustic beam, irradiates the ink, and ejects the ink using radiation pressure.
• the inkjet head used in the inkjet method may be of an on-demand type or a continuous type.
• the ink nozzles and the like used when recording by the inkjet method can be appropriately selected depending on the purpose.
• inkjet methods include a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality by using multiple inks of substantially the same hue but different densities, and a method of using colorless and transparent ink.
• Inkjet methods include a shuttle method that uses a short serial head and records by scanning the head in the width direction of the recording medium, and a line method that uses a line head in which recording elements are arranged to cover the entire area of one side of the recording medium.
• an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction perpendicular to the arrangement direction of the recording elements, eliminating the need for a transport system such as a carriage that scans a short head.
• a transport system such as a carriage that scans a short head.
• an ink set of two or more colors as the ink-jet inks, and to simultaneously apply all the inks of the colors to the recording medium in the first step. That is, in the present invention, by preventing deterioration of image quality in a specific first step and improving the strength of the coating film in the second step, a printed coating film with good image quality can be formed even when all colors are simultaneously applied to a recording medium using an ink set of two or more colors. From this viewpoint, the ink set may be three or more colors, or even four or more colors.
• the ink set is four or more colors. Therefore, in the present invention, it is more preferable to use an ink set of four or more colors as the inkjet ink and apply all colors of ink to a recording medium simultaneously in the first step.
• the recording medium to which the ink-jet ink has been applied is irradiated with active energy rays at the same time as the application of the ink described above.
• the polymerizable compound contained in the inkjet ink of the present invention is polymerized by the action of the polymerization initiator to form a cured film of the inkjet ink, which more effectively improves the abrasion resistance and blocking resistance of the image.
• the inkjet ink of the present invention undergoes a curing reaction when irradiated with active energy rays.
• the polymerization initiator contained in the inkjet ink of the present invention decomposes when irradiated with active energy rays, generating radicals, which initiate and accelerate the polymerization reaction of the polymerizable compound, thereby curing the inkjet ink.
• the inkjet ink When treated with a pretreatment agent containing an acidic compound, the inkjet ink is further coagulated (fixed) by the acid supplied from the acidic compound during irradiation with active energy rays, resulting in improved image quality (abrasion resistance, blocking resistance, etc.).
• treatment with a pretreatment agent can be omitted.
• the second step of the inkjet recording method of the present invention is a step of irradiating the inkjet ink on the recording medium with active energy rays after the first step, i.e., after the application of the inkjet ink to the recording medium to be irradiated simultaneously.
• the active energy ray irradiation in the second step is preferably performed consecutively after the active energy ray irradiation in the first step, with the light amount and illuminance changed as described below.
• the ink-jet ink on the recording medium after the first step is further irradiated with active energy rays.
• active energy rays By irradiating with active energy rays, the polymerization of the polymerizable compound contained in the ink-jet ink of the present invention can be further promoted, and a cured film with high image quality and higher strength can be formed. Details of the active energy rays irradiated in the second step are as follows.
• the active energy rays used in the first step and the active energy rays used in the second step may be the same, or may have different light sources or emission peak wavelengths. In order to simplify the configuration of the recording device used, it is preferable that the active energy rays used in the first step and the second step are the same, and that the light amount and maximum illuminance of the active energy rays are adjusted as follows.
• the active energy rays used in the first and second steps may be ⁇ -rays, ⁇ -rays, electron beams, X-rays, ultraviolet light, visible light, infrared light, etc.
• the polymerization initiator preferably used in the ink-jet ink of the present invention has high absorption, particularly for light in the ultraviolet region, and from this viewpoint, the emission peak wavelength of the active energy ray source for irradiation 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.
• the main sources of actinic radiation are mercury lamps, gas/solid-state lasers, etc.
• Mercury lamps, halogen lamps, and metal halide lamps are widely known as light sources used to cure UV-curable water-based inks.
• mercury lamps, halogen lamps, and metal halide lamps are widely known as light sources used to cure UV-curable water-based inks.
• LEDs and laser diodes (LDs) are small, have a long life, are highly efficient, and are low cost, and are expected to be used as light sources for photocurable inkjet printers.
• LEDs and LDs can be used as active energy ray sources.
• UV-LEDs and UV-LDs can be used as ultraviolet light sources.
• Nichia Chemical Co., Ltd. has launched a purple LED with a main emission spectrum having wavelengths between 365 nm and 420 nm.
• a particularly preferred active energy ray source is a UV-LED, and a particularly preferred UV-LED has an emission peak wavelength of 350 to 420 nm.
• a light emitting diode having an emission peak wavelength in the range of 350 to 420 nm.
• the amount of light of the active energy rays per pass irradiated in the second step is greater than the amount of light of the active energy rays per pass irradiated in the first step (first step light amount). It is preferable that the light amount in the second step is greater than the light amount in the first step, because the curing of the polymerizable compound is partially completed in the first step, thereby thickening the ink and allowing the unreacted polymerizable compound to be sufficiently cured in the second step.
• the first step light amount is preferably 0.05 J/cm2 or more , more preferably 0.1 J/cm2 or more , while 0.6 J/cm2 or less , more preferably 0.5 J/cm2 or less .
• the second step light amount is preferably 0.6 J/cm2 or more , while 4.0 J/cm2 or less, more preferably 2.0 J/cm2 or less .
• the second step light amount is preferably 2 times or more, more preferably 3 times or more, while 50 times or less, more preferably 15 times or less, even more preferably 10 times or less, and particularly preferably 9 times or less, of the first step light amount.
• the integrated light amount corresponding to the sum of the light amount of the active energy ray irradiated in the first step and the light amount of the active energy ray irradiated in the second step (hereinafter, may be simply referred to as "integrated light amount”) is preferably 0.5 J/cm2 or more , particularly preferably 1.0 J/cm2 or more . If the integrated light amount is equal to or more than the above lower limit, the amount of unreacted polymerizable compound is reduced and excellent coating film strength can be obtained, which is preferable.
• the maximum irradiance of the active energy ray per pass irradiated in the second step is greater than the maximum irradiance of the active energy ray per pass irradiated in the first step (maximum irradiance in the first step).
• the maximum irradiance in the first step is preferably 0.05 W/ cm2 or more, more preferably 0.2 W/ cm2 or more, while being preferably less than 1.0 W/ cm2 , more preferably 0.8 W/cm2 or less , and even more preferably 0.6 W/ cm2 or less.
• it is an essential requirement that the maximum illuminance in the first step is less than 1.0 W/cm 2.
• the maximum illuminance in the first step is less than 1.0 W/cm 2 , as described above, the image quality can be improved by incomplete curing.
• the maximum illuminance in the first step is less than 1.0 W/cm 2 , preferably 0.8 W/cm 2 or less, more preferably 0.6 W/cm 2 or less, while preferably 0.05 W/cm 2 or more, more preferably 0.2 W/cm 2 or more.
• the maximum illuminance in the second step is preferably 0.5 W/cm 2 or more, more preferably 0.8 W/cm 2 or more, while it is preferably 5.0 W/cm 2 or less, more preferably 3.0 W/cm 2 or less.
• the maximum illuminance of the second step is preferably at least twice the maximum illuminance of the first step, and more preferably at least three times, while it is preferably not more than 40 times, more preferably not more than 10 times, and even more preferably not more than 9 times.
• the inkjet recording method of the present invention may, if necessary, include a drying step of drying and removing the solvent (e.g., water, an aqueous medium, etc.) in the ink applied onto the recording medium.
• the drying step is not particularly limited as long as it can remove at least a part of the ink solvent, and a commonly used method can be applied.
• the heating temperature is preferably 120°C or lower, and more preferably 100°C or lower.
• the heating temperature refers to the surface temperature of the recording surface of the recording medium.
• the heating means is not particularly limited, but for example, a hot air heater or an infrared heater can be used. More specifically, examples of the heating means include a ceramic heater, a halogen heater, and a quartz tube heater. A hot plate can also be used as the heating means, which is preferable because it can keep the recording medium at a uniform temperature.
• the heating of the recording medium by the heating means is preferably performed from the side opposite the recording surface of the recording medium, since this has little effect on the recording surface of the recording medium.
• the timing of heating may be before the first step, during the first step, during the second step, or after the second step. It is more preferable to continue heating throughout the entire process, before the first step, during the first step, during the second step, and after the second step.
• the recording medium used in the inkjet recording method of the present invention is not particularly limited, and may be an absorbent recording medium or a non-absorbent recording medium.
• the recording medium By increasing the viscosity of the droplets by irradiation in the first step, the droplets are prevented from penetrating and spreading in an absorbent medium, and are prevented from coalescing with each other in a non-absorbent medium, so that the effects of the present invention can be enjoyed whether the recording medium is absorbent or non-absorbent.
• an absorbent recording medium refers to a recording medium having a surface that is highly absorbent of ink. More quantitatively, a recording medium having a water absorption of 0.3 g/m2 or more from the start of contact to 30 msec1 /2 in the Bristow method is considered to be an absorbent recording medium. On the other hand, a recording medium having a water absorption of less than 0.3 g/ m2 is considered to be a non-absorbent recording medium.
• Absorbent recording media include paper, fabric, leather, wood, and composites of these. Of these, paper and fabric are preferred, and fabric is more preferred. There are no particular limitations on the material that makes up the fabric, and examples include natural fibers such as cotton, linen, wool, and silk, synthetic fibers such as polypropylene, polyester, acetate, triacetate, polyamide, and polyurethane, and biodegradable fibers such as polylactic acid. The material that makes up the fabric may also be a blend of these fibers.
• Non-absorbent recording media include plastic materials such as polyesters such as polyethylene terephthalate (PET), polyolefins such as polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP), glass, ceramics, metals, and composites of these.
• PET polyethylene terephthalate
• PVC polyvinyl chloride
• PE polyethylene
• PP polypropylene
• glass ceramics, metals, and composites of these.
• polyesters are preferred, and polyethylene terephthalate (PET) is more preferred.
• the inkjet recording apparatus for carrying out the inkjet recording method of the present invention may be any of various recording apparatuses using an inkjet recording system.
• the inkjet recording method of the present invention can be suitably used in printers, facsimile machines, copying machines, printer/fax/copier combination machines, three-dimensional modeling apparatuses, etc.
• a recording device is a device capable of ejecting ink, various treatment liquids, and the like onto a recording medium.
• This recording device may include not only a head portion that ejects ink, but also means related to feeding, transporting, and discharging the recording medium, and other devices called pre-processing devices and post-processing devices.
• the recording device may have a heating means or drying means for heating the absorbent recording medium, and an irradiation means for irradiating the medium with active energy rays.
• the heating means and drying means include, for example, means for heating and drying the printing surface and back surface of the recording medium.
• examples of the irradiation means for irradiating the active energy rays include means using a light source such as a halogen lamp, a metal halide lamp, an LED lamp, etc.
• the light source for curing the ink irradiates the ink with active energy rays from the side of the head to cure the ink, thereby forming a print image. It is preferable that the irradiation means used in the first step and the irradiation means used in the second step are of the same type.
• Recording devices are not limited to those that use ink to visualize meaningful images such as letters and figures. For example, they also include those that form patterns such as geometric shapes and those that create three-dimensional images.
• Recording devices include not only desktop types, but also wide-format recording devices that can print on A0-sized recording media, and continuous-feed printers that can use continuous paper wound into a roll as the recording medium.
• the recording method of the recording device or the irradiation method of active energy rays includes both a shuttle method in which recording or irradiation is performed while moving a serial head, and a line method in which recording is performed using a line head.
• shuttle-type recording devices see, for example, JP-A-2022-181182 and JP-A-2010-280828.
• the recording method or the active energy ray irradiation method of the recording apparatus is preferably a shuttle method, since it is possible to obtain the remarkable effects of the present invention. More specifically, it is preferable that the carriage is provided with an inkjet head and an active energy ray irradiation unit.
• the same carriage that was used for applying the inkjet ink and irradiating the active energy ray in the first step is used to irradiate the active energy ray in the second step.
• the ink-jet ink of the present invention contains at least a polymerizable compound, a polymerization initiator, and water. That is, in the ink-jet recording method of the present invention, an ultraviolet-curable water-based ink can be used.
• the polymerizable compound contained in the inkjet ink of the present invention is not particularly limited as long as it is a compound having polymerizability, and known polymerizable monomers, polymerizable resins, polymerizable oligomers, etc. can be used. Among the above, polymerizable oligomers are preferred, and ultraviolet-curable oligomers are more preferred.
• the polymerizable compound examples include (meth)acrylamide compounds, (meth)acrylate compounds, vinyl compounds, maleimide compounds, vinyl sulfone compounds, N-vinyl amide compounds, and derivatives thereof. These compounds are more preferably bifunctional or higher.
• the polymerizable compound is more preferably a (meth)acrylamide compound, a (meth)acrylate compound, or a vinyl compound, and particularly preferably a bifunctional or higher (meth)acrylamide compound.
• “(meth)acrylate” means acrylate or methacrylate. The same applies to "(meth)acryloyl" and "(meth)acrylic".
• polymerizable compounds may be used alone or in combination of two or more.
• the above polymerizable compound may have a poly(ethyleneoxy) chain, a poly(propyleneoxy) chain, an ionic group (e.g., a carboxyl group, a sulfo group, etc.), a hydroxyl group, etc., in the molecule in order to improve water solubility.
• an ionic group e.g., a carboxyl group, a sulfo group, etc.
• a hydroxyl group etc.
• the (meth)acrylate compound either a monofunctional (meth)acrylate compound (a compound having one (meth)acryloyl group) or a polyfunctional (meth)acrylate compound can be used, with polyfunctional (meth)acrylate compounds being preferred.
• the UV-curable oligomer may be nonionic or ionic (anionic, cationic, or amphoteric) without any particular limitation as to whether it is ionic or not.
• nonionic means, for example, that the hydrophilic group of the UV-curable oligomer is composed of an ether bond or a hydroxyl group that does not ionize in water.
• Ionic anionic, cationic, or amphoteric means, for example, that the UV-curable oligomer has a carboxyl group or an amino group that can ionize in water.
• any of the following ⁇ 1> to ⁇ 3> is preferred.
• X is an alkylene group
• Y is a (meth)acryloyl group, an allyl group, an acyl group, or a hydrogen atom
• n is an integer of 2 or more.
• the ultraviolet-curable oligomer of ⁇ 3> is usually produced by reacting a polyisocyanate compound (A), a compound (B'), and a compound (C').
• Compound (B') A compound containing two or more polymerizable unsaturated bonds and capable of bonding with the polyisocyanate compound (A).
• Compound (C') A water-soluble compound capable of bonding with the polyisocyanate compound (A).
• ultraviolet-curable oligomer those containing structural units derived from (meth)acrylates, particularly those containing structural units derived from polyfunctional (meth)acrylates, are preferred. Furthermore, those containing structural units derived from polyfunctional (meth)acrylates and structural units derived from polyalkylene glycols are preferred. That is, from the viewpoint of reactivity, it is preferred that compound (B') is a hydroxyl-containing polyfunctional (meth)acrylate (B). From the viewpoint of water dispersibility, it is preferred that compound (C') is a polyalkylene glycol (C).
• Such ultraviolet-curable oligomers are usually produced by reacting a polyisocyanate compound (A), a hydroxyl-containing polyfunctional (meth)acrylate (B), and a polyalkylene glycol (C).
• structural unit derived from X refers to a structural unit that is incorporated into the molecular structure of an ultraviolet-curable oligomer by using compound X as a raw material and reacting compound X with another compound.
• structural unit derived from X is not necessarily limited to using compound X as a raw material. In other words, even if it is formed from a raw material other than X, it is considered to be a "structural unit derived from X" as long as the chemical structure is the same.
• a preferred embodiment of compound (B') is a hydroxyl group-containing polyfunctional (meth)acrylate (B).
• a preferred embodiment of compound (B') may be "a compound (B") that contains a hydroxyl group and two or more polymerizable unsaturated bonds.”
• the "compound capable of bonding with polyisocyanate compound (A)" in compound (B') may be a compound in which the hydroxyl group of compound (B") has been replaced with a carboxy group, an amino group, or the like.
• Examples of the polymerizable unsaturated bond include a carbon-carbon double bond and a carbon-carbon triple bond, and among these, a carbon-carbon double bond is preferred. More specifically, examples of the polymerizable unsaturated bond include carbon-carbon double bonds derived from a vinyl group, a (meth)acryloyl group, or the like.
• the water-soluble compound in the compound (C') includes water-soluble polymers, specifically, polyglycerin, polyhydroxy (meth) acrylate, polyamine, quaternary aminated polystyrene, sulfonated polystyrene, polyether, polyalkylene glycol, etc.
• nonionic water-soluble compounds such as polyglycerin, polyhydroxy (meth) acrylate, and polyalkylene glycol are preferred, and polyalkylene glycol is particularly preferred.
• Each of these water-soluble compounds may be a copolymer.
• Compound (C') has the structure of such a water-soluble compound and the structure of a "compound capable of bonding to polyisocyanate compound (A)".
• the structure of the "compound capable of bonding to polyisocyanate compound (A)" can be selected from the same structures as those exemplified as compound (B') above.
• the structural units derived from the polyisocyanate compound (A) form urethane bonds by bonding with the structural units derived from the hydroxyl group-containing polyfunctional (meth)acrylate (B) and the structural units derived from the polyalkylene glycol (C). These urethane bonds may each be substituted with a urea bond or an amide bond.
• the preferred or specific aspects in that case can be similarly applied to the aspects or specific aspects that are preferred when using the hydroxyl group-containing polyfunctional (meth)acrylate (B) or polyalkylene glycol (C) described below.
• oligomer is not limited to a specific molecular weight range, etc., and it is sufficient if it has the structure shown below.
• the inkjet ink may contain only one type of ultraviolet-curable oligomer, or may contain two or more types.
• the polyisocyanate compound (A) is a compound having a total of two or more isocyanate groups in one molecule.
• the type of polyisocyanate compound (A) is not particularly limited, and examples include linear aliphatic polyisocyanates, aromatic polyisocyanates, and alicyclic polyisocyanates. Among these, it is preferable that the polyisocyanate compound (A) contains a polyisocyanate trimer compound from the viewpoints of weather resistance and hardness.
• a chain aliphatic polyisocyanate is a compound having a chain aliphatic structure and two or more isocyanate groups. Chain aliphatic polyisocyanates are preferred from the viewpoints of weather resistance and stretchability.
• the chain aliphatic structure in the chain aliphatic polyisocyanate is not particularly limited, but is preferably a straight-chain or branched alkylene group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms.
• chain aliphatic polyisocyanates examples include aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate, or trimer compounds of these polyisocyanates.
• Aromatic polyisocyanates are compounds that have an aromatic structure and two or more isocyanate groups. Aromatic polyisocyanates are preferred from the viewpoint of coating film strength.
• the aromatic structure in aromatic polyisocyanates is not particularly limited, but aromatic structures having 6 to 13 carbon atoms are preferred. Examples of aromatic polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, and naphthalene diisocyanate, as well as trimer compounds of these polyisocyanates.
• Alicyclic polyisocyanates are compounds that have an alicyclic structure and two or more isocyanate groups.
• the alicyclic structure in alicyclic polyisocyanates is not particularly limited, but the number of carbon atoms is usually 5 or more, preferably 6 or more, and usually 15 or less, preferably 14 or less, and more preferably 13 or less.
• the alicyclic structure is particularly preferably a cycloalkylene group.
• alicyclic polyisocyanates include diisocyanates having an alicyclic structure such as bis(isocyanatemethyl)cyclohexane, cyclohexane diisocyanate, bis(isocyanatecyclohexyl)methane, and isophorone diisocyanate, as well as trimer compounds of these polyisocyanates.
• the ultraviolet-curable oligomer may contain only one of these polyisocyanate compounds (A) or two or more of them in combination.
• the polyisocyanate compound (A) a polyisocyanate having two or more structures selected from a chain aliphatic structure, an aromatic structure, and an alicyclic structure may also be used.
• polyisocyanate compound (A) those having 3 or more and 6 or less isocyanate groups are preferred, particularly from the viewpoint of adhesion to a substrate.
• a trimer obtained by trimerization reaction of hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenylene diisocyanate, etc. is preferred, and a trimer of hexamethylene diisocyanate is particularly preferred.
• the number of polymerizable unsaturated bonds is preferably 1 or more, more preferably 2 or more, even more preferably 4 or more, and is preferably 8 or less, more preferably 6 or less.
• the compound containing a polymerizable unsaturated bond is preferably a compound capable of bonding with the polyisocyanate compound (A).
• the compound (B') is a compound which contains two or more polymerizable unsaturated bonds and can bond with the polyisocyanate compound (A).
• the compound (B') may be a compound having any one of a hydroxyl group, an amino group, and a carboxyl group.
• the compound (B') may be a polyfunctional vinyl monomer, a polyfunctional allyl monomer, or a polyfunctional (meth)acrylate. Among them, the compound (B') is preferably a hydroxyl group-containing polyfunctional (meth)acrylate (B).
• the hydroxyl group-containing polyfunctional (meth)acrylate (B) has one or more hydroxyl groups and two or more (meth)acryloyl groups. Specifically, it may be a (meth)acrylic acid partial ester of a polyhydric alcohol.
• the polyfunctional (meth)acrylate having a hydroxyl group forms a good crosslinked structure due to the involvement of multiple (meth)acryloyl groups in the curing reaction, and can provide good physical properties such as stain resistance and abrasion resistance.
• the number of hydroxyl groups in the hydroxyl group-containing polyfunctional (meth)acrylate (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 group-containing polyfunctional (meth)acrylate (B) is preferably 8 or less, and more preferably 6 or less.
• Examples of the hydroxyl group-containing polyfunctional (meth)acrylate (B) include pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, 2-hydroxy-1,3-dimethacryloxypropane, 2-hydroxy-3-acryloyloxypropyl methacrylate, etc.
• these hydroxyl group-containing polyfunctional (meth)acrylates (B) may be used alone or in combination of two or more.
• hydroxyl group-containing polyfunctional (meth)acrylate (B) those having one hydroxyl group and 3 to 5 (meth)acryloyl groups are preferred, particularly from the viewpoint of the coating film strength of the resulting cured film.
• dipentaerythritol penta(meth)acrylate and pentaerythritol tri(meth)acrylate are preferred.
• Dipentaerythritol penta(meth)acrylate is particularly preferred, as it forms a good crosslinked structure and increases the mechanical strength of the cured film.
• the compound (C') is a water-soluble compound capable of bonding with the polyisocyanate compound (A).
• the compound (C') is preferably a compound containing one terminal hydroxyl group, since this provides good water dispersibility.
• examples of the compound (C') include water-soluble polymers, and among these, polyalkylene glycol (C) is particularly preferred.
• the polyalkylene glycol (C) is preferably, but not limited to, a mono-substituted structure. That is, one of the hydroxyl groups of the glycol is preferably substituted.
• the substituted structure is preferably a structure that does not bond with an isocyanate.
• the polyalkylene glycol (C) may be a mixture of a compound having a mono-substituted structure and a compound not having a mono-substituted structure.
• the mono-substituted structure is not limited, but from the viewpoint of making the ultraviolet-curable oligomer nonionic, polyalkylene glycol mono-substituted ether is preferred, polyethylene glycol mono-substituted ether, polytrimethylene glycol mono-substituted ether or polypropylene glycol mono-substituted ether is more preferred, and polyethylene glycol mono-substituted ether is even more preferred.
• the molecular weight of the polyalkylene glycol (C) (if not single, this means the number average molecular weight) is not limited, but is usually 100 or more, preferably 200 or more, and usually 5000 or less, preferably 2000 or less.
• polyalkylene glycol mono-substituted ethers that do not contain ionic substituents in the ether portion are more preferred.
• those represented by the following formula (1) are even more preferred.
• X is an alkylene group
• Y is an alkyl group, a (meth)acryloyl group, an allyl group, an acyl group, or a hydrogen atom.
• n is an integer of 2 or more.
• polyalkylene glycol mono-substituted ether represented by the above formula (1) include the following. Those where Y is an alkyl group: polyethylene glycol monomethyl ether, polyethylene glycol lauryl ether, polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol tridecyl ether, polyethylene glycol oleyl ether, polyethylene glycol octylphenyl ether, polyoxyethylene oleyl cetyl ether, polypropylene glycol monomethyl ether, etc.
• Y is an alkyl group: polyethylene glycol monomethyl ether, polyethylene glycol lauryl ether, polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol tridecyl ether, polyethylene glycol oleyl ether, polyethylene glycol octylphenyl ether, polyoxyethylene oleyl cetyl ether, polypropylene glycol monomethyl
• Y is a (meth)acryloyl group: polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, poly(ethylene glycol-propylene glycol) mono(meth)acrylate, poly(ethylene glycol-tetramethylene glycol) mono(meth)acrylate, poly(propylene glycol-tetramethylene glycol) mono(meth)acrylate, etc.
• Y is an allyl group: polyethylene glycol monoallyl ether, polypropylene glycol monoallyl ether, poly(ethylene glycol-propylene glycol) monoallyl ether, etc.
• Y is an acyl group: polyethylene glycol monolaurate, polypropylene glycol monolaurate, poly(ethylene glycol-propylene glycol) monolaurate, polyethylene glycol monostearate, polyethylene glycol monooleate, etc.
• X in formula (1) is preferably an alkylene group having 1 to 3 carbon atoms, more preferably an ethylene group, a trimethylene group, or a propylene group. From the viewpoint of pigment dispersion stability or storage stability at high temperatures, X is still more preferably an ethylene group. From the viewpoint of coating film strength, Y is preferably a (meth)acryloyl group, an allyl group or an acyl group, and more preferably an allyl group.
• n is usually 2 or more, preferably 5 or more, more preferably 6 or more, from the viewpoint of the coating strength of the resulting cured film, and is usually 500 or less, preferably 100 or less, more preferably 50 or less.
• the polyalkylene glycol (C) may be a mixture of compounds with different molecular weights (compounds with different n in formula (1)).
• the polymerizable compound is preferably present as particles, more preferably as particles having an average particle size of 10 nm to 200 nm, and even more preferably as particles having an average particle size of 20 nm to 150 nm.
• the average particle size of the polymerizable compound is within the above range, the dispersion stability is good.
• the average particle size of the polymerizable compound is, for example, the volume average particle size (D 50 ) measured by a particle size measuring device using a dynamic light scattering method.
• the average particle size of the polymerizable compound particles in the aqueous dispersion of the polymerizable compound is measured.
• the average particle size of the polymerizable compound particles in this aqueous dispersion is approximately equal to the average particle size of the polymerizable compound particles in the ink.
• the polymerizable compound exists as particles, it is included in the above-mentioned state of "existing as particles” even if there is aggregation or other substances are contained within the particles.
• the average particle size of the polymerizable compound refers to the particle size (primary particle size) of the polymerizable compound particles.
• the ink-jet ink used in the ink-jet recording method of the present invention may contain a colorant.
• a colorant used in the inkjet ink
• various dyes or pigments known as colorants used in inks can be used. From the viewpoints of irradiation with active energy rays and long-term storage durability of printed images, it is preferable to use a pigment.
• the dyes that can be used in the present invention are not particularly limited, and examples thereof include water-soluble dyes such as acid dyes, direct dyes, and reactive dyes, disperse dyes, etc. Among these, anionic dyes are preferred.
• Water-soluble dyes examples include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane dyes.
• azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, and chelate azo pigment, polycyclic pigments such as phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxandine pigment, thioindigo pigment, isoindolinone pigment, and quinophthaloni pigment, dye lakes such as basic dye lake and acid dye lake, organic pigments such as nitro pigment, nitroso pigment, aniline black, and daylight fluorescent pigment, and inorganic pigments such as carbon black, titanium oxide, and iron oxide pigment.
• anionic pigments are preferred.
• These dyes or pigments may be used alone or in combination of two or more.
• the ink-jet ink of the present invention is an aqueous ink.
• aqueous ink refers to an ink that contains an aqueous medium.
• the aqueous medium is water and/or a water-soluble organic solvent.
• the aqueous medium used in the present invention is preferably water or a mixture of water and a water-soluble organic solvent.
• Water-soluble organic solvents are classified into two types: those that function as moisturizing solvents to increase the moisturizing and wettability of the ink, and those that are used as aqueous media to adjust the viscosity of the ink and improve its handling and ejection properties. There is no clear distinction between the two, and water-soluble organic solvents used as moisturizing solvents also function as aqueous media.
• a water-soluble organic solvent refers to a compound that is soluble in water.
• a compound that can dissolve in water at any ratio is preferred.
• a compound that is difficult to have the properties of a solvent on its own for example, a compound that is solid or has a high viscosity at room temperature
• water-soluble organic solvents include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.
• water-soluble organic solvent examples include the following: 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 polyhydric alcohols such as 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexa
• an organic solvent with a boiling point of 250°C or less, as this not only functions as a moisturizing solvent but also provides good drying properties.
• polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used.
• polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
• glycol ether compound examples include polyhydric alcohol alkyl ethers such as 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, and propylene glycol monoethyl ether; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
• polyhydric alcohol alkyl ethers such as 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, and propylene glycol monoethyl
• These water-soluble organic solvents may be used alone or in combination of two or more.
• the ink-jet ink of the present invention contains a polymerization initiator.
• the polymerization initiator is a photoradical polymerization initiator that generates radicals, which are active species, by the energy of light (ultraviolet rays) received by irradiation with active energy rays, and initiates photopolymerization of a polymerizable compound, thereby curing the ink present on the surface of a recording medium to form an image.
• the polymerization initiator may be contained in the ink in a state where it is not encapsulated in the polymerizable compound, or may be contained in the ink in a state where it is encapsulated in particles of the polymerizable compound. Furthermore, the polymerization initiator may be contained in both of these states.
• the polymerization initiator may be a fat-soluble polymerization initiator (hereinafter, may be referred to as a "fat-soluble initiator”) or a water-soluble polymerization initiator (hereinafter, may be referred to as a "water-soluble initiator”).
• fat-soluble initiator refers to a polymerization initiator that is compatible with a polymerizable compound such as an ultraviolet-curable oligomer or that dissolves in an organic solvent.
• water-soluble initiator refers to an initiator that dissolves in water at a concentration of 1% by mass or more. The same applies to the "fat-soluble sensitizer” and “water-soluble sensitizer” described below.
• Polymerization initiators used in the present invention include, but are not limited to, aromatic ketones, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thio compounds (thioxanthone compounds, thiophenyl group-containing compounds), ⁇ -aminoalkylphenone compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds.
• the polymerization initiator contains at least one of an acylphosphine oxide compound and a thioxanthone compound.
• fat-soluble polymerization initiators include, but are not limited to, acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, p,p'-bisdiethylaminobenzophenone, Michler's ketone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, benzil methyl ketal, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1- ⁇ 4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl ⁇ 2-methylpropan-1-
• Water-soluble polymerization initiators include, but are not limited to, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, sodium phenyl(2,4,6-trimethylbenzoyl)phosphinate, 2-(3-dimethylamino-2-hydroxypropoxy)-3,4-dimethyl-9H-thioxanthone-9-one methchloride, etc.
• polymerization initiators include, for example, GENOPOL TX-2 manufactured by RAHN, and Irgacure (registered trademark) 369, Irgacure (registered trademark) 500, and Irgacure (registered trademark) 2959 manufactured by BASF Japan.
• the polymerization initiator may be used alone or in combination of two or more.
• a fat-soluble initiator and a water-soluble initiator may be used in combination, with the fat-soluble initiator being encapsulated in particles of a polymerizable compound such as an ultraviolet-curable oligomer, and the water-soluble initiator being dissolved in an aqueous medium.
• a thermal radical polymerization initiator in addition to the above-mentioned photoradical polymerization initiator, a thermal radical polymerization initiator may be used in combination.
• the ink-jet ink of the present invention preferably contains a surfactant in order to improve the flatness of the coating film formed and the wettability with the substrate.
• surfactants any of the following can be used: silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants.
• silicone surfactants there are no particular limitations on the silicone surfactants, and they can be selected appropriately depending on the purpose. Among them, those that do not decompose even at high pH are preferred, and examples thereof include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane. Those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferred, as they exhibit good properties as aqueous surfactants. Polyether modified silicone surfactants can also be used as silicone surfactants. Examples of polyether modified silicone surfactants include compounds in which a polyalkylene oxide structure is introduced into the Si side chain of dimethylsiloxane.
• fluorine-based surfactant a compound having 2 or more and 16 or less fluorine-substituted carbon atoms is preferable, and a compound having 4 or more and 16 or less fluorine-substituted carbon atoms is more preferable.
• fluorine-based surfactant for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl alkylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains are preferred because of their low foaming properties.
• Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate salts.
• Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylates.
• Examples of the perfluoroalkyl phosphate compound include perfluoroalkyl phosphate and perfluoroalkyl phosphate salts.
• Examples of perfluoroalkyl alkylene oxide adducts include perfluoroalkyl ethylene oxide adducts.
• polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group on the side chain include sulfate salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain, and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain.
• counter ions of the salts in these fluorosurfactants include Li, Na, K , NH4 , NH3CH2CH2OH , NH2 ( CH2CH2OH ) 2 , and NH( CH2CH2OH ) 3 .
• polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are more preferred because they have particularly low foaming properties, and fluorine-based surfactants represented by the following formulas (3A) and (3B) are particularly preferred.
• s is preferably an integer of 0 or more and 10 or less
• t is preferably an integer of 0 or more and 40 or less, in order to impart water solubility.
• Z is H, C d F 2d+1 (d is an integer of 1 or more and 6 or less), or CH 2 CH(OH)CH 2 -C e F 2e+1 (e is an integer of 4 or more and 6 or less).
• (f is an integer of 1 to 19)
• C f H 2f+1 f is an integer of 1 to 19.
• r is an integer of 1 or more and 6 or less
• c is an integer of 4 or more and 14 or less.
• fluorine-based surfactants can be used.
• examples of commercially available products include Surflon (registered trademark) S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F-1405, and F-474 (all manufactured by DIC Corporation); and Zonyl TBS, FSP, FSA, FSN-100, FSN, and FSO-10.
• amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
• 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, acetylene alcohol derivatives, and acetylene glycol derivatives.
• anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.
• silicone surfactant there are no particular limitations on the silicone surfactant, and it can be selected appropriately depending on the purpose.
• Polyether-modified silicone surfactants that have a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.
• Such surfactants may be synthesized appropriately or commercially available products may be used.
• Commercially available products are available from, for example, BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., etc.
• polyether-modified silicone surfactant there are no particular limitations on the polyether-modified silicone surfactant, and it can be selected appropriately depending on the purpose.
• it can be one in which a polyalkylene oxide structure is introduced into the Si side chain of dimethylpolysiloxane, as shown in the following formula (2).
• polyether-modified silicone surfactants can be used.
• examples of commercially available products include KF-618, KF-642, and KF-643 (Shin-Etsu Chemical Co., Ltd.), SAG001, SAG002, SAG003, SAG005, SAG503, and SAG008 (Nissin Chemical Co., Ltd.), EMALEX-SS-5602 and SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, and FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33 and BYK-387 (BYK-Chemie Co., Ltd.), and TSF4440, TSF4452, and TSF4453 (Toshiba Silicon Co., Ltd.).
• the ink-jet ink of the present invention may contain a sensitizer.
• a sensitizer When a sensitizer is present in the ink together with the polymerization initiator, the sensitizer in the system absorbs active energy rays and becomes excited, and upon contact with the polymerization initiator, promotes decomposition of the polymerization initiator, thereby enabling a curing reaction with higher sensitivity.
• the sensitizer may be fat-soluble, like the polymerization initiator, or may be water-soluble. If the sensitizer is fat-soluble, it can be encapsulated in particles of a polymerizable compound such as an ultraviolet-curable oligomer.
• Sensitizers that can be used include aliphatic amines, amines having aromatic groups, or cyclic amine compounds such as 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-aminobenzonitrile, phosphorus compounds such as tri-n-butylphosphine or sodium diethyldithiophosphate, Michler's ketone, N-nitrosohydroxylamine derivatives, oxazolidine compounds, tetrahydro-1,3-oxazine compounds, and nitrogen compounds such as condensates of formaldehyde or acetaldehyde with diamines.
• sensitizers may be used alone or in combination of two or more.
• the inkjet ink of the present invention may contain any oligomer component other than the polymerizable compound, any resin component, or any monomer component (collectively referred to as "other resin components").
• the other resin components may be encapsulated in the particles of the polymerizable compound or dissolved in the aqueous medium.
• the other resin components may be dispersed alone in the ink or may be in a composite state with other components.
• the ink-jet ink of the present invention may contain other additives, if necessary.
• additives include known additives such as anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, antifungal agents, rust inhibitors, pH adjusters, viscosity adjusters, dispersants, dispersion stabilizers, defoamers, solid wetting agents, chelating agents, etc. These various additives may be added directly after the ink is prepared, or may be added during the preparation of the ink.
• the water content in the inkjet ink of the present invention is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of the drying property and ejection reliability of the ink, the water content in the inkjet ink of the present invention is usually 10% by mass or more, preferably 20% by mass or more, more preferably 40% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less.
• 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 also as a moisturizing solvent and the water-soluble organic solvent used as an aqueous medium) is not particularly limited and can be appropriately selected depending on the type of water-soluble organic solvent used and the purpose.
• the content of the water-soluble organic solvent is usually 10% by mass or more and usually 50% by mass or less, preferably 40% by mass or less.
• the content of volatile components in the total amount of the inkjet ink of the present invention is preferably 70% by mass or more, more preferably 75% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less. If the content of the volatile component is equal to or higher than the above lower limit, the ejection reliability is high, whereas if the content is equal to or lower than the above upper limit, the coating strength can be increased.
• the volatile components in the inkjet ink of the present invention refer to components that are reduced by 90% or more after 1 g of the inkjet ink is placed on an aluminum dish having a diameter of 10 cm and dried at 80° C. for 4 hours compared to before drying.
• the inkjet ink of the present invention is prepared so that the total solids concentration, which is the concentration of components other than the aqueous medium, which is water and/or a water-soluble organic solvent, is usually 5% by mass or more, preferably 7% by mass or more, more preferably 9% by mass or more, and usually 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.
• the ratio of water to water-soluble organic solvent (the total of the water-soluble organic solvent used as the aqueous medium and the water-soluble organic solvent used as the moisturizing solvent) is usually 1:0.05 to 1:1.5 (by mass), preferably 1:0.1 to 1:1.2 (by mass), and more preferably 1:0.15 to 1:1.1 (by mass), from the viewpoint of improving drying properties and ejection properties.
• the content of the polymerizable compound in the inkjet ink of the present invention is usually 3% by mass or more, preferably 5% by mass or more, and more preferably 7% by mass or more, from the viewpoint of the performance of the obtained printed coating film and the active energy ray curability.
• the content of the polymerizable compound in the inkjet ink of the present invention is usually 20% by mass or less, preferably 15% by mass or less, and more preferably 12% by mass or less.
• the content of the polymerizable compound in the total solid content of the inkjet ink of the present invention is usually 30% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass or more, and is usually 90% by mass or less, preferably 85% by mass or less, and more preferably 80% by mass or less.
• the content of the colorant in the inkjet ink of the present invention is usually 0.1% by mass or more, and preferably 1% by mass or more, from the viewpoints of improving image density, good fixability, and ejection stability, and is usually 8% by mass or less, and preferably 6% by mass or less. From the same viewpoint, the content of the colorant in the total solid content of the ink-jet ink of the present invention is usually 1% by mass or more, preferably 5% by mass or more, and usually 40% by mass or less, preferably 30% by mass or less.
• the content of the polymerization initiator in the inkjet ink of the present invention is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, and is usually 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.
• the content of the polymerization initiator in the total solid content of the ink-jet ink of the present invention is usually 0.5% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, and is usually 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.
• the inkjet ink of the present invention contains a surfactant
• its content is not particularly limited and can be appropriately selected depending on the purpose.
• the content of the 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.
• the content of the surfactant in the total solid content of the inkjet ink of the present invention is usually 0.01 mass % or more, preferably 0.1 mass % or more, and more preferably 0.2 mass % or more, and is usually 10 mass % or less, preferably 5 mass % or less, and more preferably 3 mass % or less.
• the content thereof is usually 0.01% by mass or more, preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and usually 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.
• the content of the sensitizer is within the above range, the effect of the sensitizer can be sufficiently obtained.
• the content of the sensitizer in the total solid content of the inkjet ink of the present invention is usually 0.05% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, and is usually 8% by mass or less, preferably 6% by mass or less, and more preferably 5% by mass or less.
• 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.
• the viscosity of the inkjet ink can be measured using a digital viscometer DV-I+ manufactured by BROOKFIELD.
• the inkjet ink of the present invention used in the inkjet recording method of the present invention is water-based, and therefore has excellent environmental and safety properties.
• a printed coating film with excellent coating properties can be formed using the water-based ink with excellent environmental and safety properties. Therefore, the inkjet recording method of the present invention can be suitably used for various applications such as posters, road signs, signboards, billboards, various outdoor and indoor display boards, building materials (surface materials for exteriors, interiors, walls, floors, ceilings, windows, etc.), exteriors of vehicles, etc. (automobiles, trains, aircraft, etc.), surface materials for furniture and office automation equipment, paper prints, cloth for clothing such as T-shirts, textiles, home furnishings, etc.
• Non-absorbent recording medium > (Illumination)
• PET A non-absorbent illumination transparent film made of surface-treated polyethylene terephthalate
• polyester de chine
• a fat-soluble initiator (GENOPOL TX-2 manufactured by RAHN Corporation) was added, and the mixture was kept at 60° C. and stirred. Ion-exchanged water that had been preheated to 60° C.
• the average particle size (D 50 ) of the ultraviolet-curable oligomer particles in this aqueous dispersion was 29 nm when measured using a particle size distribution meter, MICROTRAC WAVEII-EX150 (manufactured by Microtrac Bell Co., Ltd.).
• Ion-exchanged water the polymerizable compound aqueous dispersion (solid content concentration: 20% by mass), 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 manufactured by BYK Japan KK as surfactant 1, and EMACOL SF CYAN AE2034F manufactured by Sanyo Pigment Co., Ltd. (shown as "Cy” in Table 1) as pigment dispersion were added and mixed to obtain the composition ratio shown in Table 1, to obtain ink 1.
• the viscosity of ink 1 at 25° C. was 6.4 mPa ⁇ s.
• the water content and the volatile component content in ink 1 were 66% by mass and 86% by mass, respectively.
• Inks 2 to 8 were obtained in the same manner as Ink 1, except that the types and blending ratios of the pigment dispersions, and the blending ratios of the water-soluble sensitizer and surfactant were changed as shown in Table 1 below using the following pigment dispersions.
• the percentage of each component in Table 1 indicates the content of that component in the aqueous dispersion or solution, if that component is in the form of an aqueous dispersion or solution.
• Example 1 In a commercially available shuttle-type UV inkjet printer, the ink 1 was set as the inkjet ink and (illuminated) PET was set as the recording medium. At this time, a hot plate was installed on the flatbed, and the recording medium was set on the hot plate.
• the printing settings were as follows, and the inkjet ink was applied to the recording medium from the inkjet head, and a first step of irradiating the inkjet ink with active energy rays at the same time as the application of the inkjet ink and a second step of irradiating the inkjet ink applied to the recording medium with active energy rays were performed, to obtain a printed coating film.
• Print Settings Resolution: 600 x 720 dpi Number of passes: 16 passes Image: 5 x 16.5 cm solid image
• An LED with a peak emission wavelength of 385 nm was used as the active energy ray source, and the light amount, maximum illuminance, cumulative light amount, and heater temperature of the active energy ray in the first and second steps were as shown in Table 2.
• An ultraviolet integrating light meter (Hamamatsu Photonics "H12684") was used to measure the illuminance and cumulative light amount.
• Examples 2 to 8, Comparative Examples 1 to 12 A printed coating film was obtained in the same manner as in Example 1, except that the type of ink, the amount of active energy rays in the first and second steps, the maximum illuminance and integrated amount of light, the timing of irradiation with active energy rays, and the heater temperature were changed as shown in Tables 2 and 3.
• the heater temperature corresponds to the surface temperature of the recording surface of the recording medium.
• Comparative Examples 1 to 4 only the first step of irradiating active energy rays simultaneously with application of the ink-jet ink was carried out, and the second step was not carried out thereafter.
• Example 9 The inks 1 to 4 were set as inkjet inks and polyester decene was set as a recording medium in a commercially available shuttle-type UV inkjet printer. A hot plate was installed on the flatbed, and the recording medium was set on the hot plate.
• the printing settings were as follows, and the inkjet inks were applied from the inkjet head to the recording medium, and a first step of applying the inkjet inks 1 to 4 and irradiating active energy rays simultaneously, and a second step of irradiating the inkjet ink applied to the recording medium with active energy rays were performed, to obtain a printed coating film.
• Print Settings Resolution: 600 x 720 dpi Number of passes: 16 passes
• Image 13 x 19.5 cm mixed color photo image
• An LED with a peak emission wavelength of 385 nm was used as the source of active energy rays, and the light intensity, maximum illuminance, cumulative light intensity, and heater temperature in the first and second steps were as shown in Table 4.
• An ultraviolet integrating light meter (Hamamatsu Photonics "H12684”) was used to measure the illuminance and cumulative light intensity.
• Examples 10 and 11, Comparative Examples 13 to 15 A printed coating film was obtained in the same manner as in Example 9, except that the type of ink, the type of recording medium, the amount of active energy radiation in the first and second steps, the maximum illuminance and integrated amount of light, the timing of irradiation with active energy radiation, and the heater temperature were changed as shown in Table 4.
• Inks 9 to 12 were obtained in the same manner as ink 1, except that the types of pigment dispersion and surfactant were changed and the blending ratios were altered as shown in Table 5.
• Pigment "Cy1” Cyan pigment dispersion Pigment “Ma1”: Magenta pigment dispersion Pigment “Ye1”: Yellow pigment dispersion Pigment “Bk1”: Black pigment dispersion Surfactant 2: BYK349 manufactured by BYK Japan Surfactant 3: Olfin E1010 manufactured by Nissin Chemical Industry Co., Ltd.
• Example 12 Comparative Example 16
• the inks 9 to 12 were set in a shuttle-type UV inkjet printer different from the UV inkjet printer used in Example 1, and cotton fabric was set as a recording medium. At this time, the recording medium was set on a hot plate.
• the printing settings were 8 passes for both the first and second steps in Example 12, 2 passes for the first step and 8 passes for the second step in Comparative Example 16, and the rest were as follows.
• the inkjet ink was applied from the inkjet head to the recording medium, and a first step of irradiating active energy rays simultaneously with the application of the inkjet ink, and a second step of irradiating active energy rays to the inkjet ink applied to the recording medium were performed, to obtain a printed coating film.
• Print Settings 600 x 600 dpi Image: 29.7 x 37 cm mixed color photo image
• the ink jet recording method of the present invention can form printed images having good image quality and excellent coating strength.
• Comparative Example 16 in which the amount of light of the active energy rays irradiated per pass in the second step is greater than the amount of light of the active energy rays irradiated per pass in the first step, while the maximum illuminance of the active energy rays irradiated per pass in the second step is the same as the maximum illuminance of the active energy rays irradiated per pass in the first step, the coating strength is good but the image quality is poor. This is presumably because the irradiation intensity is low relative to the amount of ink discharged per unit time.

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