WO2021172008A1 - Encre pour impression jet d'encre et procédé de formation d'image - Google Patents

Encre pour impression jet d'encre et procédé de formation d'image Download PDF

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Publication number
WO2021172008A1
WO2021172008A1 PCT/JP2021/004862 JP2021004862W WO2021172008A1 WO 2021172008 A1 WO2021172008 A1 WO 2021172008A1 JP 2021004862 W JP2021004862 W JP 2021004862W WO 2021172008 A1 WO2021172008 A1 WO 2021172008A1
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Prior art keywords
ink
inkjet ink
temperature
inkjet
mass
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PCT/JP2021/004862
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English (en)
Japanese (ja)
Inventor
小俣　猛憲
晃央 前田
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コニカミノルタ株式会社
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Priority to JP2022503243A priority Critical patent/JPWO2021172008A1/ja
Publication of WO2021172008A1 publication Critical patent/WO2021172008A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
    • B41J2/01—Ink jet
    • B41J2/17—Ink jet characterised by ink handling
    • B41J2/18—Ink recirculation systems
    • 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
    • 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

Definitions

  • the present invention relates to an inkjet ink and an image forming method. More specifically, the present invention relates to an inkjet ink capable of maintaining good ejection properties and forming a high-quality image, and an image forming method by an inkjet method capable of forming a high-quality image with good workability. Regarding.
  • inkjet ink droplets of inkjet ink (hereinafter, also simply referred to as “ink”) are ejected from the inkjet head (hereinafter, also simply referred to as “head”) toward the base material and land on the base material. After that, the solvent is dried to form a coating film (image).
  • a coating film image
  • a non-absorbent base material made of PET (polyethylene terephthalate) or the like
  • an additive is added to the ink to give it thixotropy, and the ink circulates in the head to increase the share and reduce the viscosity. It is disclosed that the viscosity becomes high, the ink is hard to be absorbed by the absorbent base material, and the image is formed at a high density without heating the platen.
  • Patent Document 1 a water-based inkjet in which a water-soluble polymer compound is added to impart thixotropy to an ink so that the ink viscosity at low share becomes 1.5 times or more the viscosity at high share.
  • the ink is listed.
  • Patent Document 1 when this ink is circulated and discharged by a head, it has a high share and a low viscosity, but when it lands, it has a low share and a high viscosity, and the concentration is lowered by the absorbing base material. It is stated to prevent.
  • Patent Document 1 does not describe an attempt to control the thickening of the ink by combining the thixotropic property of the ink itself and the drying conditions. It is assumed that it is not possible to achieve both good ejection performance and high-quality image formation only by the method of controlling the thixotropic property of the ink itself as in Patent Document 1.
  • Patent Document 2 describes a water-based inkjet ink to which a water-soluble temperature-responsive polymer is added.
  • Patent Document 2 describes the effect of suppressing the penetration of ink into a paper substrate to increase the density.
  • the temperature-responsive polymer is added in an amount of about 5% by mass in the entire ink, and is added twice or more with respect to the coloring material. Then, it is described that the color material is fixed by shrinking the resin and covering the color material when heat is applied.
  • the thixotropic property is not controlled so as to change the viscosity of the ink in the head and at the time of landing. Therefore, it is assumed that the ink described in Patent Document 2 cannot achieve both good ejection performance and high-quality image formation.
  • the present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an inkjet ink that enables both maintenance of good ejection properties and high-quality image formation at the same time.
  • Another object of the present invention is to provide an image forming method capable of forming a high-quality image with good workability in image forming by an inkjet method.
  • the present inventor uses the viscosity at the time of high share at the time of circulation in the head of the inkjet ink and the viscosity at the time of low share at the time of landing as indexes.
  • the composition of the inkjet ink using the temperature-responsive polymer was examined.
  • the viscosity at the time of circulation in the head is low and slightly.
  • the present invention has been made by finding that an ink having a sufficiently high viscosity at the time of landing can be obtained by adjusting the temperature.
  • the ink is an inkjet ink capable of maintaining good ejection properties and forming a high-quality image at the same time. That is, the above problem according to the present invention is solved by the following means.
  • An inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, wherein the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the pigment is contained in the total amount of the inkjet ink.
  • the amount is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1% by mass.
  • Ink ink that is within range.
  • the viscosity of the inkjet ink at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less, and the shear rate at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C.
  • the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin.
  • Item 8 The inkjet ink according to Item 8, wherein the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
  • An image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink has a viscosity of 15 mPa ⁇ s or less in the inkjet head.
  • the droplets are circulated so as to be, and when they land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%, and the viscosity is 100 mPa ⁇ s or more.
  • the inkjet head communicates with a pressure chamber into which the inkjet ink is injected via an injection path, a pressure generating means for causing a pressure fluctuation in the pressure chamber, and the pressure chamber, and the pressure fluctuation in the pressure chamber causes the inkjet head to communicate with the pressure chamber.
  • a nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside, and two or more circulation paths that communicate with the pressure chamber to discharge the inkjet ink inside the nozzle and return it to the injection path.
  • the inkjet ink of the present invention contains an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water.
  • the content is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is in the range of 0.01 to 1% by mass. It is characterized by being.
  • the lower limit critical eutectic temperature of a temperature-responsive polymer refers to the lower limit critical eutectic temperature with respect to water.
  • the viscosity at the time of high share can be lowered, for example, the viscosity (25 ° C.) of the ink at a shear rate of 1000 (1 / s) can be set to 15 mPa ⁇ s or less.
  • the viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
  • the viscosity at the time of landing is increased, for example, the shear rate 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer.
  • the viscosity at the time can be 45 mPa ⁇ s or more.
  • the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. can be 45 mPa ⁇ s or more.
  • the ink of the present invention has a high viscosity required for good pinning within a range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature responsive polymer with water.
  • a large amount of water-based solvent can remain in the ink from the time of ejection to the time of impact, so that the sticking of the solid ink content around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
  • the temperature-responsive polymer and the fixing resin in combination, water resistance can be imparted to the ink coating film obtained by image formation. This is considered to be the effect obtained by the temperature-responsive polymer and the fixing resin being entangled in the process of image formation. Further, the entanglement improves the substrate fixability of the ink coating film obtained by image formation.
  • the image forming method of the present invention is an image forming method comprising a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing the ink jet ink on a substrate. It is circulated so that the viscosity is 15 mPa ⁇ s or less.
  • the viscosity is a viscosity at which ink can be smoothly circulated at the head and ejected from the head.
  • the mass reduction rate of the ink droplets when they land on the substrate or immediately after landing from the ink circulating in the head is within 20% and the viscosity.
  • the landing process is performed so that the value is 100 mPa ⁇ s or more.
  • FIG. 1 Schematic configuration of a main part showing an inkjet image forming apparatus including an example of an inkjet head that can be used in the image forming method of the present invention.
  • Top view of the nozzle plate of the inkjet head shown in FIG. The graph used when obtaining the crossover strain (%) of the ink of Example 1.
  • the inkjet ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water, and the total amount of the inkjet ink
  • the content of the pigment is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1. It is characterized in that it is within the range of mass%.
  • the viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • the viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. is 45 mPa ⁇ s or more.
  • the aqueous solvent is removed from the inkjet ink so as to have a mass of 80% of the initial mass from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • this state is also referred to as “ink drying rate 20%”
  • the viscosity at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical co-melting temperature ⁇ 10 ° C. is 100 mPa.
  • -It is preferable that the value is s or more.
  • the lower limit critical eutectic temperature of the temperature-responsive polymer with respect to water is within the range of 30 to 60 ° C. from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have. Moreover, it is preferable that the temperature-responsive polymer contains a water-soluble cellulose resin.
  • the content of the aqueous solvent is in the range of 50 to 90% by mass with respect to the total amount of the inkjet ink from the viewpoint of maintaining good ejection properties and forming a high-quality image. It is preferable to have.
  • the fixing resin contains at least one selected from the group consisting of a polyacrylic resin, a polyurethane resin, and a polyester resin from the viewpoint of exhibiting the effect of the present invention.
  • the inkjet ink further contains a thixotropic agent from the viewpoint of maintaining good ejection properties and forming a high-quality image.
  • the thixotropy-imparting agent contains cellulose nanofibers or smectite clay minerals.
  • the content of the thixotropy-imparting agent is preferably in the range of 0.01 to 1% by mass with respect to the total amount of the inkjet ink.
  • the image forming method of the present invention is an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate, wherein the inkjet ink is the inkjet head.
  • the droplets are circulated in the ink jet so as to have a viscosity of 15 mPa ⁇ s or less, and when the droplets land on the base material or immediately after landing, the mass reduction rate from the inkjet ink is within 20%.
  • the landing step is performed so that the viscosity becomes 100 mPa ⁇ s or more.
  • the viscosity of the droplet when landing on the substrate or immediately after landing is 150 mPa ⁇ s or more. ..
  • An embodiment of the image forming method of the present invention includes that the landing step heats the droplets on the substrate in the range of 30 to 60 ° C. from the viewpoint of further exhibiting the effects of the present invention. Is preferable. Further, it is preferable that the droplet is within 100 msec after landing on the base material immediately after the landing.
  • the base material is a non-absorbent base material because the effect of the present invention is more remarkable.
  • the inkjet head has a pressure chamber in which the inkjet ink is injected via an injection path and a pressure fluctuation in the pressure chamber.
  • a nozzle that communicates with the pressure chamber and serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to pressure fluctuations in the pressure chamber, and communicates with the pressure chamber. It is preferable to provide two or more circulation paths for discharging the inkjet ink inside the nozzle and returning the inkjet ink to the injection path.
  • the inkjet ink of the present invention As an embodiment of the image forming method of the present invention, it is preferable to use the inkjet ink of the present invention as the inkjet ink from the viewpoint of further exhibiting the effects of the present invention.
  • the ink of the present invention is an inkjet ink containing an aqueous solvent, a pigment, a fixing resin, and a temperature-responsive polymer, and the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to water with respect to the total amount of the inkjet ink.
  • the content of the pigment is in the range of 2 to 10% by mass
  • the content of the fixing resin is in the range of 1 to 10% by mass
  • the content of the temperature-responsive polymer is 0.01 to 1% by mass. It is characterized in that it is within the range of%.
  • the aqueous solvent means water or a solvent containing water and an aqueous solvent.
  • the aqueous solvent is a solvent that is compatible with water at room temperature.
  • the ink of the present invention can contain any component other than the aqueous solvent, the pigment, the fixing resin, and the temperature-responsive polymer, which does not impair the effect of the present invention.
  • the optional component include a thixotropic agent, a pigment dispersant, a surfactant and the like.
  • the temperature-responsive polymer contained in the ink of the present invention is a polymer having a low critical solution temperature (hereinafter, also referred to as “LCST”) with respect to water.
  • LCST critical solution temperature
  • the temperature-responsive polymer has the property of being soluble in water below LCST and insoluble in water above LCST, for example, gelling.
  • the aqueous solution of the temperature-responsive polymer has the property of undergoing a phase change with the LCST as a critical point. The property is reversible.
  • the ink of the present invention can adjust the viscosity of the ink in the head and at the time of landing on the base material within an appropriate range, thereby maintaining good ejection properties. It is possible to achieve both high-quality image formation.
  • the LCST of the temperature-responsive polymer in water can be measured, for example, by measuring the phase transition temperature of the aqueous temperature-responsive polymer solution using a differential scanning calorimeter (DSC). Alternatively, it can be carried out by measuring the change in the light transmittance of the aqueous solution while gradually raising (lowering) the temperature of the aqueous solution of the temperature-responsive polymer.
  • DSC differential scanning calorimeter
  • the temperature-responsive polymer preferably has an LCST in the range of 30 to 60 ° C, more preferably in the range of 40 to 50 ° C.
  • the LCST of the temperature-responsive polymer is 30 ° C. or higher, the ink does not normally increase its viscosity extremely in the temperature range circulating in the head. Further, if the LCST of the temperature-responsive polymer is 60 ° C. or lower, it is possible to increase the viscosity of the ink droplets to a desired level without removing the aqueous solvent without raising the temperature to a high temperature at the time of landing. Become.
  • the aqueous solvent contained in the ink may consist of water as described later, but optionally contains an aqueous solvent in addition to water.
  • the LCST of the temperature-responsive polymer for the aqueous solvent may differ from the LCST of the temperature-responsive polymer for water. The difference between the two is preferably within about 10 ° C. That is, the LCST of the temperature-responsive polymer with respect to the aqueous solvent is preferably within the range of LCST ⁇ 10 ° C. with respect to water of the temperature-responsive polymer.
  • the temperature-responsive polymer examples include water-soluble cellulose resins, poly (N-substituted (meth) acrylamide), poly (N-vinyl acylamide), poly ((meth) acrylic acid alkyl ester), and other temperature-responsive polymers. Examples include polymers. Among these, a water-soluble cellulose resin is preferable as the temperature-responsive polymer used in the ink of the present invention.
  • (meth) acrylamide is a general term of acrylamide and methacrylamide.
  • (meth) acrylic acid is a general term for acrylic acid and methacrylic acid.
  • the water-soluble cellulose resin is a resin to which water solubility is imparted by substituting a part of hydrogen atoms of OH groups possessed by cellulose to eliminate hydrogen bonds.
  • substituent that replaces the hydrogen atom of the OH group include an alkyl group, a hydroxyalkyl group, and a carboxy group.
  • substituent a methyl group, a hydroxypropyl group and a hydroxyethyl group are preferable.
  • one type may be used alone, or two or more types may be used in combination.
  • water-soluble cellulose resin examples include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose and the like.
  • an alkyl group which may have an ether bond (-O-) between carbon atoms is preferable.
  • the alkyl group may be cyclic, straight chain or branched chain, and may be a combination thereof.
  • the nitrogen atom has one or two substituents, and when there are two substituents, these may be bonded to form a ring.
  • the number of carbon atoms in the alkyl group is preferably 1 to 10.
  • poly (N-substituted (meth) acrylamide) examples include poly (N-ethylacrylamide), poly (Nn-propyl (meth) acrylamide), poly (N-isopropyl (meth) acrylamide), and poly.
  • N-cyclopropyl (meth) acrylamide), poly (N, N-diethyl (meth) acrylamide) and the like can be mentioned.
  • poly (N-substituted (meth) acrylamide) does not have to be composed of a single monomer. That is, poly (N-substituted (meth) acrylamide) may be a copolymer of N-substituted (meth) acrylamide having different substituents. Further, the copolymerization of N-substituted (meth) acrylamide with at least one selected from the following polymers, for example, monomers constituting poly (N-vinylacylamide) and poly ((meth) acrylic acid alkyl ester). It may be coalesced.
  • poly (N-vinylacylamide) examples include poly (N-vinylacetamide), poly (N-vinylpropionic acid amide), poly (N-vinylbutyric acid amide), poly (N-vinylisobutyric acid amide) and the like. ..
  • poly ((meth) acrylic acid alkyl ester) examples include poly (n-butyl methacrylate), poly (dodecyl methacrylate), poly (n-hexyl methacrylate), poly (methyl methacrylate), and poly (n-octyl methacrylate). Can be mentioned.
  • temperature-responsive polymers include poly (N, N-acrylic pyrrolidone), poly (N-acrylic piperidine), and copolymers thereof, alternating copolymers of polyvinyl isobutyl vinyl ether and maleic anhydride, and poly (2-).
  • Methyl-5-vinylpyridine poly (vinyl alcohol), poly (N-vinylpyrrolidone), poly (N-vinylsuccinic acid), poly (vinyl sulfonic acid), poly (oxyethylene), poly (tetrahydrofuran), amylopectin, Examples thereof include amylose, poly (vinyl acetate), poly (propylene glycol), polyvinyl methyl ether (PVME), polyvinyl methyl oxazolidinone and the like.
  • thermoresponsive polymer one of these may be used alone, or two or more thereof may be used in combination.
  • the weight average molecular weight of the temperature-responsive polymer is not particularly limited, but is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 80,000 or less.
  • the weight average molecular weight of the temperature-responsive polymer is 10,000 or more, the polymer is easily entangled with the fixing resin to impart water resistance to the ink coating film (image). Further, when the weight average molecular weight is 100,000 or less, there is little possibility that the viscosity of the ink becomes too high and the ejection property deteriorates.
  • the weight average molecular weight of the temperature-responsive polymer is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).
  • the temperature responsive polymer As the temperature responsive polymer, a commercially available product may be used. Commercially available products include, for example, water-soluble cellulose resins under the trade names manufactured by Shin-Etsu Chemical Co., Ltd., Metrose SM-04 (methyl cellulose resin, LCST; 55 ° C.), Metrose 60SH-03 (hydroxypropyl methylcellulose resin, LCST). ; 75 ° C.) and the like.
  • poly (N-substituted (meth) acrylamide) examples include poly (as N-isopropylacrylamide, Sigma-Aldrich, for example, poly (N-isopropylacrylamide (LCST; 35 ° C., weight average molecular weight; 30,000)) and the like. Can be mentioned.
  • the content of the temperature-responsive polymer in the ink of the present invention is in the range of 0.01 to 1% by mass with respect to the total amount of the ink.
  • the effect of the present invention can be obtained by blending the temperature-responsive polymer.
  • the content of the temperature responsive polymer is preferably in the range of 0.05 to 0.8% by mass.
  • the ink of the present invention contains a fixing resin.
  • a fixing resin By containing a fixing resin in addition to the temperature-responsive polymer, the ink of the present invention can appropriately adjust the viscosity of the ink when it lands on the head and the base material, and can be used as an ink coating film obtained by image formation. Water resistance can be imparted.
  • the fixing resin further functions as a binder for a pigment which is a colorant, improves the adhesiveness of the coating film to a base material, particularly a non-absorbent base material, and scratch resistance of the coating film obtained by using an ink. It has a function to improve the sex.
  • the fixing resin is preferably a water-insoluble resin.
  • the water-insoluble resin as the fixing resin is preferably used in the form of fine particles dispersed in an aqueous solvent.
  • the fine particles of the water-insoluble resin have a form in which the originally water-insoluble resin is dispersed as microscopic fine particles in an aqueous solvent.
  • the fine particles may be in the form of, for example, forcibly emulsifying a water-insoluble resin using an emulsifier or the like and dispersing them as fine particles in an aqueous solvent.
  • a hydrophilic functional group is introduced into the molecule of the water-insoluble resin to form stable fine particles by itself in an aqueous solvent without using an emulsifier or a dispersion stabilizer, that is, self-emulsified. It may be a thing.
  • the aqueous solvent in which the fine particles of the water-insoluble resin are dispersed the same aqueous solvent as described above can be used, and usually water or a water / alcohol mixed solvent is used.
  • the fine particles of the water-insoluble resin dispersed in the aqueous solvent are also referred to as an aqueous dispersion.
  • the term "water-insoluble resin” means that when the resin is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the amount of the resin dissolved is 10 g or less, preferably 5 g or less. More preferably, it refers to a resin having a weight of 1 g or less. However, when the resin has a salt-forming group, the dissolved amount is the dissolved amount when the salt-forming group of the resin is 100% neutralized with acetic acid or sodium hydroxide, depending on the type.
  • water-insoluble resins such as polyester resin, polyurethane resin and polyacrylic resin are preferable.
  • the fixing resin one of these may be used alone, or two or more thereof may be used in combination.
  • the fixing resin is contained in the range of 1 to 10% by mass with respect to the total mass (100% by mass) of the ink.
  • the content of the fixing resin is preferably in the range of 2 to 8% by mass, more preferably in the range of 3 to 6% by mass.
  • the ratio (percentage) of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is in the range of 0.1 to 20% by mass. It is preferable that the relationship is as follows. The ratio is more preferably 0.5 to 10% by mass. When the ratio of the content of the temperature-responsive polymer to the total content of the temperature-responsive polymer and the fixing resin is within the above range, it is easy to achieve both the water resistance of the coating film (image) obtained from the ink and the good pinning characteristics.
  • the polyester resin used as the fixing resin can be obtained by using a polyhydric alcohol component and a polyvalent carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester.
  • the polyhydric alcohol component includes a dihydric alcohol (diol), specifically, an alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1) in the range of 2 to 36 carbon atoms. , 4-butylene glycol, 1,6-hexanediol, etc.), alkylene ether glycol in the range of 4 to 36 carbon atoms (diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.), An alicyclic diol having 6 to 36 carbon atoms (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.) and an alkylene oxide having 2 to 4 carbon atoms of the alicyclic diol (ethylene oxide (hereinafter referred to as ethylene oxide)).
  • dihydric alcohol diol
  • alkylene glycol ethylene glycol, 1,2-propylene glycol, 1,3
  • EO abbreviated as EO
  • PO propylene oxide
  • BO butylene oxide
  • the polyvalent carboxylic acid component includes a divalent carboxylic acid (dicarboxylic acid), specifically, an alkandicarboxylic acid (succinic acid, apidic acid, sebacic acid, etc.) in the range of 4 to 36 carbon atoms, and an alkenyl succinic acid.
  • divalent carboxylic acid divalent carboxylic acid
  • alkandicarboxylic acid succinic acid, apidic acid, sebacic acid, etc.
  • the number average molecular weight of the polyester resin is preferably in the range of 1000 to 50,000, and more preferably in the range of 2000 to 20000.
  • polyester resin a commercially available product
  • a commercially available product for example, a dispersion liquid in which the polyester resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • examples of commercially available products of the dispersion liquid include the following. In the example, the number average molecular weight of the polyester resin contained in the product (dispersion liquid) is shown in parentheses. These may be used alone or in combination of two or more.
  • polyurethane resin As the polyurethane resin used as the fixing resin, one having a hydrophilic group can be used.
  • the hydrophilic group include a carboxyl group (-COOH) and salts thereof, sulfonic acid group (-SO 3 H) and a salt.
  • the salt include alkali metal salts such as sodium salt and potassium salt, amine salts and the like.
  • a carboxy group or a salt thereof is preferable.
  • the above-mentioned polyurethane resin is forcibly emulsified under a strong mechanical shearing force by using an aqueous dispersion in which a self-emulsifying polyurethane having a water-soluble functional group in its molecule is dispersed in an aqueous solvent or a surfactant in combination.
  • the type polyurethane is preferably an aqueous dispersion dispersed in an aqueous solvent.
  • the polyurethane resin in the aqueous dispersion can be obtained by reacting a polyol with an organic polyisocyanate and a hydrophilic group-containing compound.
  • polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, Low molecular weight polyols such as hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol; succinic acid, glutaric acid, adipine Includes condensates with polyvalent carboxylic acids such as acids, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, tetrahydrofuran acid, endomethine tetrahydrofuran acid, and hexahydrophthalic acid.
  • polyvalent carboxylic acids such as acids, sebacic acid,
  • polyether polyols examples include polyethylene glycol, polypropylene glycol, polyethylene polytetramethylene glycol, polypropylene polytetremethylene glycol, polytetramethylene glycol and the like.
  • polycarbonate polyols include compounds obtained by reacting carbonic acid derivatives such as diphenyl carbonate, dimethyl carbonate or phosgene with diols.
  • diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propylene glycol, neopentyl glycol, 1,3- and 1,4-butanediol, 3-methylpentanediol, etc.
  • Hexamethylene glycol, 1,8-octanediol, 2-methyl-1,3-propanediol, bisphenol A, hydrogenated bisphenol A, trimethylolpropane, cyclohexanedimethanol and the like are included.
  • organic polyisocyanates that can be used to prepare aqueous dispersions of polyurethane resins include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polypeptide MDI, xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate.
  • Aromatic isocyanates such as (TMXDI); aliphatic isocyanates such as hexamethylene diisocyanate (HMDI); alicyclic isocyanates such as isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI, H12MDI). Is Only one type of these may be used alone, or two or more types may be used in combination.
  • hydrophilic group-containing compounds that can be used to prepare aqueous dispersions of polyurethane resins include 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2, 2-Carboxylic acid-containing compounds such as valeric acid and glycine, and derivatives thereof such as sodium salts, potassium salts and amine salts; sulfonic acid-containing compounds such as taurine (ie, aminoethyl sulfonic acid) and ethoxypolyethylene glycol sulfonic acid. And derivatives such as sodium salt, potassium salt, amine salt and the like.
  • Polyurethane resin can be obtained by a known method.
  • a polyurethane resin can be obtained by mixing the above-mentioned polyol, organic polyisocyanate, and a hydrophilic group-containing compound and reacting them at 30 to 130 ° C. for 30 minutes to 50 hours.
  • the polyurethane resin becomes a polyurethane resin having a hydrophilic group by being elongated with a chain extender and polymerized.
  • the chain extender is preferably a water and / or amine compound. By using water or an amine compound as the chain extender, the isocyanate-terminated prepolymer can be efficiently extended by reacting with free isocyanate in a short time.
  • amine compounds as chain extenders include aliphatic polyamines such as ethylenediamine and triethylenediamine; aromatic polyamines such as m-xylylenediamine and toluylenediamine; and polyhydradino compounds such as hydrazine and dihydrazide adipic acid.
  • the amine compound may contain, together with the polyamine, a monovalent amine such as dibutylamine, methyl ethyl ketooxime, or the like as a reaction terminator to the extent that it does not significantly inhibit polymerization.
  • a solvent that is inactive with isocyanate and can dissolve the urethane prepolymer may be used.
  • these solvents include dioxane, methyl ethyl ketone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, propylene glycol monomethyl ether acetate and the like. It is preferable that these hydrophilic organic solvents used in the reaction step are finally removed.
  • an amine catalyst for example, triethylamine, N-ethylmorpholin, triethyldiamine, etc.
  • a tin catalyst for example, dibutyltin dilaurate, dioctyltin dilaurate, tin octylate
  • catalysts such as titanium-based catalysts (eg, tetrabutyl titanate, etc.) may be added.
  • the number average molecular weight of the polyurethane resin is preferably as large as possible by introducing a branched structure or an internal crosslinked structure, and the number average molecular weight is preferably 50,000 to 10,000,000.
  • the number average molecular weight is a value measured by gel permeation chromatography (GPC).
  • the number average molecular weight (Mn) is, for example, "RID-6A” manufactured by Shimadzu Corporation (column: “TSK-GEL” manufactured by Tosoh Corporation, solvent: tetrahydrofuran (THF), column temperature: 40 ° C.). It can be obtained from the calibration curve prepared with a polystyrene standard sample.
  • polyurethane resin a commercially available product may be used.
  • a dispersion liquid in which the polyurethane resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • Examples of commercially available polyurethane resin dispersions include WBR-016U (manufactured by Taisei Fine Chemicals Co., Ltd.), Superflex 620, Superflex 650, Superflex 500M, and Superflex E-2000 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).
  • the polyacrylic resin used as the fixing resin includes a (co) polymer of the (meth) acrylic acid ester component, or a polymerizable component other than the (meth) acrylic acid ester component such as the (meth) acrylic acid ester component and the styrene component. Copolymer of.
  • (meth) acrylic acid ester components include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and -2-hydroxyethyl (meth) acrylate.
  • styrene components include styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetoxystyrene, 4-acetylstyrene, styrenesulfonic acid and the like. Only one of these components may be used alone, or two or more of these components may be used in combination.
  • the number average molecular weight (Mn) of the polyacrylic resin is preferably 1000 to 50,000, and more preferably 2000 to 20000.
  • Mn number average molecular weight of the polyacrylic resin
  • the cohesive force of the coating film becomes strong and the adhesion is improved, and when it is 50,000 or less, the solubility in an organic solvent is good and the emulsified dispersion is obtained. This is because the miniaturization of the particle size of is promoted.
  • the polyacrylic resin a commercially available product may be used.
  • a dispersion liquid in which the polyacrylic resin is dispersed in an aqueous solvent as an aqueous dispersion may be used.
  • Examples of commercially available polyacrylic resin dispersions include Delpet 60N, 80N (manufactured by Asahi Kasei Corporation, “Delpet” is a registered trademark of the same company), Dianar BR52, BR80, BR83, BR85, BR88 (Mitsubishi). Chemical Co., Ltd., "Dianar” is a registered trademark of the company), KT75 (Denka Co., Ltd.), or Viniblanc 2680, 2682, 2864, 2685 (Nissin Chemical Industry Co., Ltd., "Viniblanc” is a registered trademark of the company) ), Movinyl 6800D (manufactured by Japan Coating Resin Co., Ltd.) and the like are included.
  • the fixing resin preferably contains an acid structure. If it contains an acid structure, it can be dispersed in an aqueous solvent without the addition of a surfactant, that is, it can be self-emulsified, and the water resistance of the coating film is improved. Such a self-emulsifying resin can be dispersed and stabilized in an aqueous solvent only by the ionicity of the molecule.
  • acids structure carboxy group (-COOH), a contained such an acid group such as a sulfonic acid group (-SO 3 H) is.
  • the acid structure may be present in the side chain or at the end of the resin.
  • the acid structure is neutralized.
  • the neutralizing agent for neutralizing the acid structure organic amines
  • organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine and triethanolamine are preferably used.
  • azo pigments such as azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, phthalocyanine pigment, perylene and perylene pigment, anthraquinone pigment, quinacridone pigment, dioxandine pigment, thioindigo pigment, isoindolinone pigment, quinophthaloni pigment and the like.
  • cyclic pigments dye lakes such as basic dye type lakes and acidic dye type lakes
  • organic pigments such as nitro pigments, nitroso pigments, aniline blacks and daylight fluorescent pigments
  • inorganic pigments such as carbon black.
  • Specific organic pigments that can be preferably used include the following pigments.
  • pigments for magenta or red examples include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53: 1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I.
  • Pigment Red 166 C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 202, C.I. I. Pigment Red 222, C.I. I. Pigment Violet 19 and the like.
  • pigments for orange or yellow examples include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 15: 3, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 155 and the like. Especially in the balance between color tone and light resistance, C.I. I. Pigment Yellow 155 is preferred.
  • pigments for green or cyan examples include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.
  • pigment for black for example, C.I. I. Pigment Black 1, C.I. I. Pigment Black 6, C.I. I. Pigment Black 7 and the like.
  • the content of the pigment in the ink of the present invention is in the range of 2 to 10% by mass.
  • the content of the pigment is within the above range, it functions as an inkjet ink, and high-quality image formation is possible while maintaining good ejection properties.
  • the pigment content is preferably in the range of 3-7% by mass.
  • the ink of the present invention optionally contains a pigment dispersant to disperse the pigment.
  • the pigment dispersant is not particularly limited, but a polymer dispersant having an anionic group is preferable, and those having a number average molecular weight in the range of 5000 to 200,000 can be preferably used.
  • pigment dispersant for example, two kinds selected from styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid, and fumaric acid derivative.
  • examples thereof include block copolymers having a structure derived from the above monomers, random copolymers and salts thereof, polyoxyalkylenes, polyoxyalkylene alkyl ethers and the like.
  • the pigment dispersant preferably has an acryloyl group and an acidic group.
  • the acidic group is preferably added after being neutralized with a neutralizing base.
  • the neutralizing base is not particularly limited, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, and morpholine.
  • the amount of the pigment dispersant added is preferably in the range of 10 to 100% by mass, more preferably in the range of 10 to 40% by mass with respect to the pigment.
  • the pigment has the form of a so-called capsule pigment in which the pigment is coated with the above pigment dispersant.
  • a method of coating the pigment with a pigment dispersant various known methods can be used. For example, a phase inversion emulsification method, an acid analysis method, or a method of dispersing a pigment with a polymerizable surfactant is used therein.
  • a method of supplying a monomer and coating it while polymerizing can be preferably exemplified.
  • the pigment dispersant is dissolved in an organic solvent such as methyl ethyl ketone, the acidic groups in the resin are partially or completely neutralized with a base, and then the pigment and ion-exchanged water are added and dispersed. After that, a method of removing the organic solvent and adding water as needed can be mentioned.
  • the average particle size of the pigment in the dispersed state in the ink is preferably 50 nm or more and less than 200 nm.
  • the particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoresis method, etc., but the measurement by the dynamic light scattering method is simple and the particle size region can be measured. It can be measured accurately.
  • the pigment can be dispersed and used by a disperser together with a pigment dispersant and other additives necessary for various desired purposes.
  • the disperser a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Above all, it is preferable to disperse the pigment with a sand mill because the particle size distribution becomes sharp.
  • the material of the beads used for the sand mill dispersion is not particularly limited, but is preferably zirconia or zircon from the viewpoint of preventing the formation of bead fragments and the contamination of ionic components. Further, the bead diameter is preferably in the range of 0.3 to 3 mm.
  • the ink of the present invention contains an aqueous solvent.
  • the aqueous solvent contains water as an essential solvent, and preferably contains an arbitrarily known aqueous solvent for viscosity adjustment and the like.
  • the aqueous solvent contains an aqueous solvent, it is preferable to adjust the type and amount of the aqueous solvent to be combined with water so that the temperature-responsive polymer has a lower limit critical eutectic temperature with respect to the aqueous solvent.
  • the water contained in the ink according to the present invention is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.
  • an aqueous solvent that does not significantly change the LCST of the temperature-responsive polymer with respect to the water-based solvent from the LCST of the temperature-responsive polymer with respect to water when used in combination with water is preferable.
  • the difference between the LCST of the temperature-responsive polymer with respect to the aqueous solvent and the LCST of the temperature-responsive polymer with respect to water is approximately 10 ° C. or less.
  • aqueous solvent examples include alcohols, polyhydric alcohols, amines, amides, glycol ethers, 1,2-alkanediols having 4 or more carbon atoms, and the like.
  • alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol, 3-methoxy-1-butanol, 3-methoxy.
  • examples thereof include -3-methylbutanol, 1-octanol, 2-octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol and benzyl alcohol.
  • polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and the number of polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and propylene oxide groups having 5 or more ethylene oxide groups.
  • examples thereof include polypropylene glycol having 4 or more, butylene glycol, hexanediol, pentandiol, glycerin, hexanetriol, thiodiglycol and the like.
  • amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, and the like. Examples thereof include pentamethyldiethylenetriamine and tetramethylpropylenediamine.
  • amides include formamide, N, N-dimethylformamide, N, N-dimethylacetamide and the like.
  • glycol ethers examples include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether.
  • examples include ether.
  • 1,2-alkanediols having 4 or more carbon atoms examples include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol and the like. ..
  • a particularly preferably used aqueous solvent is a polyhydric alcohol, which can suitably suppress bleeding during high-speed printing.
  • ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol are preferable.
  • the ink can be contained in one type or a combination of two or more types selected from these aqueous solvents.
  • the water content in the ink of the present invention is preferably in the range of 20 to 80% by mass, and more preferably in the range of 40 to 70% by mass with respect to the total mass of the ink.
  • the content of the aqueous solvent in the ink is preferably in the range of 10 to 60% by mass with respect to the total mass of the ink.
  • the content ratio of water and the aqueous solvent in the ink is preferably adjusted so that the LCST of the temperature-responsive polymer with respect to the aqueous solvent is within the range of LCST of ⁇ 10 ° C. with respect to water of the temperature-responsive polymer.
  • the ink of the present invention contains substantially only an aqueous solvent as a solvent, that is, does not contain a non-aqueous solvent.
  • the content of the aqueous solvent in the ink is preferably in the range of 50 to 95% by mass, preferably in the range of 50 to 90% by mass, as the total content of water and the aqueous solvent. Is more preferable.
  • the ink of the present invention can optionally contain a thixotropic agent.
  • the thixotropic agent imparts thixotropy to the ink, which is low viscosity at the time of high share and high viscosity at the time of low share, thereby maintaining good ejection property and high quality image in the ink of the present invention. It is used for the purpose of enhancing the effect of achieving both formation.
  • the thixotropic agent can be used without particular limitation as long as it is a material that can impart thixotropic property to the ink.
  • the thixotropy-imparting agent preferably has a particle shape (however, the particle shape includes a fiber shape), and more preferably has an aspect ratio of 20 or more.
  • the shape is preferably elliptical, scaly, plate-shaped, needle-shaped, fiber or the like.
  • the aspect ratio indicating the ratio of the major axis to the minor axis of the thixotropic agent is preferably 20 or more. When the aspect ratio is 20 or more, the thixotropic property is easily imparted by the ink.
  • the major axis of the thixotropic agent is preferably 2 ⁇ m or less. If the major axis of the thixotropic agent exceeds 2 ⁇ m, the inkjet ejection property may be affected.
  • the measurement cross section of the aspect ratio of the thixo-imparting agent is a cross section parallel to the length direction of the particles and cut in the thickness direction.
  • the aspect ratio is a value obtained from the average particle major axis and the average particle minor axis of each of the 50 particles obtained from the cross section.
  • the minor axis is the thickness of the particle
  • the major axis is the length of the long side of the aspect ratio measurement cross section of the particle, or the long side when the particle is viewed in a plan view. Length or maximum diameter.
  • the major axis is the length of the particle
  • the minor axis is the major axis of the cross section orthogonal to the length direction of the particle, or the maximum width when the particle is viewed in a plan view.
  • Examples of the material of the thixotropy-imparting agent include polysaccharides and inorganic particles.
  • specific examples of the polysaccharide include cellulose, chitin, chitosan, xanthan gum, welan gum, succinoglycan, guar gum, locust bean gum and derivatives thereof, glycomannan, agar, carrageenan and the like.
  • polysaccharide a natural polysaccharide having a weight average molecular weight of about several million is preferable. Specifically, xanthan gum, guar gum, carrageenan and the like are preferable.
  • a tixo-imparting agent as a tixo-imparting agent, conventional methods such as oxidation treatment using a catalyst, mechanical treatment using a grinder, etc., for an aggregate of polysaccharides such as shells of crustaceans such as trees, crabs, and shrimp.
  • Nanofibers which are polysaccharides obtained by finely breaking the fibers by a known method, are preferably used.
  • the polysaccharide in the polysaccharide nanofiber is preferably at least one of cellulose, chitin and chitosan, with cellulose being more preferred.
  • nanofibers have a width of about 1 to 100 nm and an aspect ratio of 100 or more.
  • the length and width of the nanofibers can be measured, for example, using an electron microscope.
  • the width of the nanofiber may be measured, for example, the width in a plan view, or the diameter of a cross section orthogonal to the length direction of the nanofiber may be measured as the width.
  • the average of the maximum widths of each nanofiber is defined as the "width" of the nanofibers.
  • the "length" of nanofibers is the average length of 50 nanofibers.
  • the aspect ratio of the nanofiber is obtained as a value obtained by dividing the length by the width.
  • the width of the nanofibers is preferably 1 to 50 nm, more preferably 1 to 5 nm.
  • the length of the nanofibers is preferably 0.5 to 2 ⁇ m, more preferably 1 to 5 ⁇ m, but is not limited thereto.
  • the aspect ratio of the nanofibers is more preferably in the range of 100 to 400, and even more preferably in the range of 100 to 300.
  • polysaccharides such as cellulose, chitin, and chitosan exist in a state where structural units called microfibrils are bound to each other. These microfibrils have a width of 3 to 4 nm and a length of several ⁇ m (for example, 2 to 5 ⁇ m), but it is difficult to make one by one.
  • microfibrils have a width of 3 to 4 nm and a length of several ⁇ m (for example, 2 to 5 ⁇ m), but it is difficult to make one by one.
  • nanofibers having a width of about 20 to 50 nm.
  • such nanofibers may be used as the polysaccharide nanofibers, but it is more preferable to use TEMPO-oxidized nanofibers which are more finely dissolved by TEMPO oxidation, for example, in microfibril units.
  • TEMPO oxidation is an oxidation reaction catalyzed by 2,2,6,6-tetramethyl-1-piperidine-oxy radical (TEMPO). Oxidation of the polysaccharide aggregate in the presence of TEMPO gives very fine nanofibers equivalent to microfibrils, eg, 3-4 nm wide and several ⁇ m long (eg 2-5 ⁇ m). ..
  • Cellulose nanofibers used as thixotropy-imparting agents are nanofibers of cellulose.
  • Examples of the nano-ferverized cellulose form include powdered cellulose, microcrystalline cellulose and the like.
  • Cellulose nanofibers include Leocrysta (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd., TEMPO oxidized cellulose nanofiber manufactured by Nippon Paper Industries, Serempia TC-01A, Serempia TC-02X (“Serenpia” is a registered trademark), and Sugino Machine Limited.
  • IMa-10002, BMa-12002, WMa-12002, AMa-12002, FMa-12002, ELEX- ⁇ , ELEX-S manufactured by Daio Paper Industries, Auro Visco manufactured by Oji Paper Co., Ltd. and the like can be preferably used. ..
  • the inorganic particles particles of various natural or synthetic clay minerals are preferable.
  • the clay mineral smectite clay mineral is preferable.
  • Smectite clay minerals are classified as layered silicate minerals or bentonite stone group minerals.
  • Smectite clay minerals are classified into montmorillonite subgroup and saponite subgroup according to their laminated structure.
  • the montmorillonite subgroup includes montmorillonite, nontronite or byderite.
  • the saponite subgroup includes hectorite, saponite or saponite.
  • the smectite clay mineral may be a natural product or a synthetic product.
  • the smectite clay mineral is a layered substance in which plate-like bodies are laminated, and when used as a thixotropy-imparting agent, it is usually used as delaminated plate-like particles.
  • the smectite clay mineral is a synthetic product, it has a smaller aspect ratio and a lower impurity content than the natural product.
  • the plate-like particles of smectite clay mineral are preferably in the range of 0.2 to 3.0 nm in thickness and preferably in the range of 10 to 150 nm in length.
  • the plate-like particles have a thickness in the range of 0.2 to 2.0 nm, and more preferably a length in the range of 10 to 125 nm.
  • the aspect ratio is a value obtained by dividing the length of the plate-like particles by the thickness, and is preferably 20 or more. The aspect ratio is more preferably in the range of 20 to 200.
  • the length and thickness of the plate-shaped particles can be measured using, for example, an electron microscope.
  • the thickness of the plate-shaped particles is, for example, an average value of 50 pieces of the thickness of the plate-shaped particles measured in a predetermined cross section.
  • the "length" of the plate-shaped particles is an average value of 50 lengths measured as the maximum diameter when the plate-shaped particles are viewed in a plan view.
  • the aspect ratio of the plate-shaped particles is obtained as a value obtained by dividing the length by the thickness.
  • smectite clay mineral for example, laponite (manufactured by Big Chemie), which is a synthetic layered silicate, can be used.
  • Laponite is a synthetic low-charge clay whose structure and chemical composition are close to those of Hectorite, a natural smectite clay mineral.
  • the main particles of raponite are in the form of discs with a maximum diameter of 30 nm and a thickness of 1 nm.
  • a commercially available product may be used as the smectite clay mineral.
  • Examples of commercially available products include Laponite RD (manufactured by Big Chemie), Kunipia F, which is a refined bentonite manufactured by Kunimie Industries, Ltd., and Kunipia G.
  • alumina nanofibers manufactured by Kawaken Fine Chemical Co., Ltd. (minor axis: 4 nm and major axis: 1400 nm), which are nanofibers, may be used.
  • the content of the thiox property-imparting agent in the ink of the present invention shall be in the range of 0.01 to 1% by mass with respect to the total amount of the ink from the viewpoint of imparting texo property to the ink and further enhancing the effect of the present invention. Is preferable, and more preferably in the range of 0.08 to 0.5% by mass.
  • the thixotropy-imparting agent is preferably made of two or more kinds of materials. Further, one of the two or more materials is preferably a smectite clay mineral.
  • Preferred combinations of thixotropy-imparting agents include a combination of cellulose nanofibers and smectite clay minerals, and a combination of xanthan gum and smectite clay minerals. In particular, a combination of cellulose nanofibers and smectite clay minerals is preferable.
  • Cellulose nanofibers and smectite clay minerals even when used alone, impart elastic properties to the ink by forming a specific gel structure, for example, with an ink drying rate of 20%. It is thought that it can be done. As a result, the ink containing cellulose nanofibers or smectite clay mineral can easily achieve the properties (1-4) and (1-5) described later. Further, it is preferable to use a combination of cellulose nanofibers and smectite clay minerals because the above elastic properties are further enhanced.
  • the ratio of smectite clay mineral to other thixotropy can be selected according to the ink viscosity and thixotropy, but the ratio of smectite clay mineral: other thixotropy is 10: 1 to 1: 1 by mass ratio. It can be adjusted in the range of 10. By combining them, the thixotropy of the ink is greatly improved and the image quality is improved as compared with adding each of them alone. The reason for the improvement in thixotropy is presumed, but it is considered that smectite clay minerals have an electric charge, and smectite clay minerals and other thixotropy-imparting agents electrically associate to form a structure.
  • the ink can optionally contain a surfactant. As a result, it is possible to improve the ejection stability of the ink and control the spread (dot diameter) of the droplets that have landed on the base material.
  • the surfactant can be used without particular limitation as long as the effect of the present invention is not impaired.
  • the ionicity of the surfactant is preferably anionic, nonionic or betaine type.
  • a fluorine-based or silicone-based surfactant having a high ability to reduce static surface tension or an anionic surfactant such as dioctyl sulfosuccinate having a high ability to reduce dynamic surface tension, relatively low.
  • Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, acetylene glycols, pluronic (registered trademark) type surfactants, and sorbitan derivatives having a molecular weight are preferably used. It is also preferable to use a fluorine-based or silicone-based surfactant in combination with a surfactant having a high ability to reduce dynamic surface tension.
  • ink is mixed with a base material made of various hydrophobic resins such as vinyl chloride sheet and a base material with slow absorption such as printing paper. Can be further suppressed, and a high-quality printed image can be obtained.
  • the silicone-based surfactant is preferably a polyether-modified polysiloxane compound, and examples thereof include KF-351A and KF-642 manufactured by Shin-Etsu Chemical Co., Ltd. and BYK345, BYK347 and BYK348 manufactured by Big Chemie.
  • the above-mentioned fluorine-based surfactant means one in which a part or all of the hydrogen bonded to the carbon of the hydrophobic group of the ordinary surfactant is replaced with fluorine. Of these, those having a perfluoroalkyl group in the molecule are preferable.
  • fluorine-based surfactants some of them are under the trade name of Megafac F from Dainippon Ink and Chemicals Co., Ltd. and the trade name of Surflon from Asahi Glass Co., Ltd. -Manufacturing Company under the trade name of Flurad FC, Imperial Chemical Industry under the trade name of Monflor, and EI Dupont Nemeras & Company under the trade name of Zonyls. It is commercially available under the trade name of Licowet VPF from Parkberke Hext.
  • the content of the surfactant in the ink is not particularly limited, but is preferably in the range of 0.1 to 5.0% by mass.
  • the ink of the present invention includes emission stability, print head and ink cartridge compatibility, storage stability, image storage property, and the like, as necessary, as long as the effects of the present invention are not impaired.
  • Various known additives such as viscosity modifiers, specific resistance modifiers, film-forming agents, UV absorbers, antioxidants, anti-fading agents, anti-corrosion agents, and anti-corrosion agents, depending on the purpose of improving various performances. Etc. can be appropriately selected and used.
  • liquid paraffin dioctylphthalate, tricresyl phosphate, oil droplet fine particles such as silicone oil
  • JP-A-57-74193 JP-A-57-87988, JP-A-62-261476 and the like.
  • UV absorbers JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc.
  • the ink is prepared by mixing each of the above components so as to have the above content.
  • the pigment is mixed with other components as a dispersion liquid dispersed in a part of the aqueous solvent by the pigment dispersant.
  • the fixing resin is contained, it is preferable that the fixing resin is mixed with other components as a dispersion liquid dispersed in a part of an aqueous solvent by using a surfactant added as needed.
  • the inkjet ink of the present invention preferably satisfies the following conditions (1-1) and (1-2) with respect to viscosity characteristics. Further, in addition to these, it is more preferable to satisfy the condition (1-3).
  • the viscosity at a shear rate of 1000 (1 / s) at 25 ° C. is 15 mPa ⁇ s or less.
  • (1-2) Temperature response The viscosity of the polymer at a shear rate of 1 (1 / s) at any temperature within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. with water is 45 mPa ⁇ s or more. That is, the maximum viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) within the range of the lower limit critical eutectic temperature of ⁇ 10 ° C. is 45 mPa ⁇ s or more.
  • the viscosity in (1-1) to (1-3) above can be measured with a rotary viscometer.
  • the rotary viscometer include MCR-102 manufactured by Anton Pearl Co., Ltd.
  • the viscosity indicates the viscosity measured at 25 ° C.
  • the ink drying rate of 20% represents a state in which the aqueous solvent is removed from the inkjet ink so that the mass is 80% of the initial mass.
  • the ink drying rate can be calculated by the following formula (A) from the mass before and after drying when the ink is dried under the temperature condition of 60 ° C.
  • Ink drying rate [%] (W BEFORE- W AFTER ) / W BEFORE x 100
  • W BEFORE represents the mass (initial mass) of the ink before drying.
  • W AFTER represents the mass of the ink after drying. Specifically, about 100 mL of ink is dropped on a glass substrate, weighed to determine the mass of the ink before drying, and then heated to 60 ° C. on a hot plate capable of measuring the mass. Do it with.
  • the ink of the present invention has a viscosity of 10 mPa ⁇ s or less at a shear rate of 1000 (1 / s).
  • the lower limit of the viscosity at a shear rate of 1000 (1 / s) is not particularly limited, but is preferably about 5 mPa ⁇ s from the viewpoint of inkjet ejection property.
  • the ink of the present invention has a viscosity at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer with water. It is more preferably 70 mPa ⁇ s or more, and more preferably 100 mPa ⁇ s or more.
  • the upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa ⁇ s from the viewpoint of ease of head maintenance.
  • the ink of the present invention has a shear rate of 1 (1) at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. of the temperature-responsive polymer at an ink drying rate of 20% with water.
  • the viscosity at / s) is preferably 100 mPa ⁇ s or more, and more preferably 150 mPa ⁇ s or more.
  • the upper limit of the viscosity in this case is not particularly limited, but it is preferably about 1000 mPa ⁇ s from the viewpoint of ease of head maintenance.
  • the viscosity of the temperature-responsive polymer at a shear rate of 1 (1 / s) at any temperature in the range of the lower limit critical coexistence temperature ⁇ 10 ° C. with respect to water is at least 45 mPa ⁇ s.
  • the viscosity of the ink increases as the ink drying rate increases.
  • the temperature-responsive polymer can be at any temperature within the lower limit critical eutectic temperature of ⁇ 10 ° C. with water.
  • a viscosity of 100 mPa ⁇ s can be achieved at a shear rate of 1 (1 / s).
  • the inkjet ink of the present invention further preferably satisfies at least one of the following conditions (1-4) and (1-5), and more preferably both.
  • the loss tangent (tan ⁇ ) in (1-4) and the storage elastic modulus and loss elastic modulus in (1-5) can be measured by a rheometer (viscoelasticity measuring device).
  • a rheometer viscoelasticity measuring device
  • the loss tangent may be simply referred to as “tan ⁇ ”.
  • the tan ⁇ , the storage modulus and the loss modulus are determined by using a rheometer, specifically, using MCR-102 manufactured by Anton Pearl Co., Ltd., in an oscillation mode, with respect to water of the temperature-responsive polymer. It can be measured at any temperature in the range of the lower limit critical eutectic temperature ⁇ 10 ° C. under the measurement conditions of an angular frequency ⁇ 10 rad / s and a swing angle ⁇ 1 to 1000%.
  • the swing angle ⁇ of the cone plate of the rheometer is changed to distort the measurement sample.
  • the measurement sample is distorted following the swing angle ⁇ , the swing angle ⁇ of the cone plate and the distortion of the measurement sample have the same value.
  • tan ⁇ when the strain is 1% is used as an index. If the tan ⁇ is less than 1 when the strain is 1% under the measurement conditions, the ink has more elastic properties, and when compared with similar viscosities, the pinning property is improved and the image quality is further improved. .. In (1-4), the tan ⁇ at 1% strain is more preferably 0.8 or less, and further preferably 0.6 or less.
  • the crossover strain of the storage elastic modulus and the loss elastic modulus when the strain is changed is used as an index.
  • the crossover strain is a graph in which the vertical axis is the storage elastic modulus (Pa) and the horizontal axis is the strain (%) in logarithms, the vertical axis is the loss modulus (Pa), and the horizontal axis is the horizontal axis.
  • the value (%) of the strain at the intersection of the graphs in which the strain (%) is logarithmically shown is shown.
  • the crossover strain is more preferably 30% or more, and even more preferably 40% or more.
  • the loss tangent (tan ⁇ ) at a strain of 1% when the same measurement is performed for the ink of the present invention that is, the ink drying rate of 0%, not the state of the ink drying rate of 20%.
  • the crossover strain is 20% or more when the same measurement is performed for the ink of the present invention, that is, the ink drying rate is 0%, not the state where the ink drying rate is 20%. It is preferably 30% or more, more preferably 40% or more.
  • the tan ⁇ and the crossover strain are almost the same between the state where the ink drying rate is 0% and the state where the ink drying rate is 20%. That is, even when the ink drying rate is 0%, the ink has an elastic behavior within the range of the lower limit critical eutectic temperature ⁇ 10 ° C. with respect to water of the temperature-responsive polymer, and it is easy to pinn and a high-quality image can be formed.
  • the image forming method of the present invention has the following features in an image forming method having a landing step of ejecting droplets of inkjet ink from an inkjet head provided with an ink circulation mechanism and landing them on a substrate.
  • the inkjet ink contains an aqueous solvent, a pigment and a thixotropic agent, and is circulated in the inkjet head so that the viscosity is 15 mPa ⁇ s or less.
  • (2-2) Perform the landing step so that the mass reduction rate from the inkjet ink is within 20% and the viscosity of the droplets when they land on the substrate or immediately after landing is 100 mPa ⁇ s or more. conduct.
  • the image forming method of the present invention usually includes a drying step of removing the aqueous solvent from the ink droplets on the substrate after the landing step. By going through the drying step, a desired image is formed on the base material. Further, the image forming method of the present invention may include a step of forming a primer layer on the surface of the base material (hereinafter, also referred to as a "primer layer forming step") before forming a coating film with the ink. good. In this case, the ink droplets are landed on the primer layer in the landing step.
  • the primer layer can be formed by applying a primer ink containing a resin and a solvent onto a substrate and drying the primer layer. Alternatively, it may be formed by applying a primer ink containing an active energy polymerization type compound and a polymerization initiator and irradiating the coating film with active energy.
  • the method of applying the primer ink is not particularly limited, and any method such as a roll coating method, a spin coating method, a spray coating method, a dipping method, a screen printing method, an inkjet method, a gravure printing method, and an offset printing method may be used. .. Among these, when the surface roughness of the base material is finely controlled, the screen printing method or the inkjet method is preferable, and the inkjet method is particularly preferable.
  • the method of curing or drying the coating film after applying the primer ink is appropriately selected according to the type of the primer ink, and can be, for example, a method of heating or irradiating with active energy.
  • the ink in the head is 15 mPa ⁇ s or less, the ink can be smoothly circulated in the head and discharged from the head.
  • the viscosity of the ink in the head is preferably circulated so as to be 10 mPa ⁇ s or less.
  • the mass reduction rate from the inkjet ink (hereinafter, also simply referred to as “mass reduction rate”) can be defined in the same manner as the ink drying rate described above. If the mass reduction rate and the viscosity of the ink droplets when landing on the substrate or immediately after landing are within the above ranges, good pinning is possible and the obtained image can be of high quality. Further, the sticking of solid ink around the head is suppressed, ejection defects are less likely to occur, and maintenance is easy.
  • the term "immediately after landing” means, for example, within 100 msec after the ink droplets land on the base material. If the mass reduction rate of the ink droplets within 100 msec after landing on the substrate is within 20% and the viscosity is 100 mPa ⁇ s or more, the above effect is sufficiently exhibited.
  • the time when the base material is landed or immediately after the landing is also referred to as "the time when the base material is landed”.
  • the viscosity of the ink droplet at the time of landing on the substrate is preferably 150 mPa ⁇ s or more, more preferably 200 mPa ⁇ s or more, and even more preferably 300 mPa ⁇ s or more.
  • the transport speed of the base material is high (100 m / min), it is within 30 msec, and when it is 50 m / min, etc., it is within 100 msec.
  • an ink or an apparatus is appropriately selected in order to satisfy the above conditions (2-1) and (2-2).
  • the conditions (2-1) and (2-2) can be achieved without particularly changing the apparatus. That is, in the image forming method of the present invention, it is preferable to use the ink of the present invention.
  • the condition (2-2) can be achieved within the range of LCST ⁇ 10 ° C. of the temperature-responsive polymer.
  • the ink droplets are heated on the substrate within the range of LCST ⁇ 10 ° C. of the temperature-responsive polymer in the landing step. Is preferable.
  • the image forming method of the present invention in order to satisfy the condition (2-2), it is preferable to heat the ink droplets on the substrate in the range of 30 to 60 ° C. in the landing step. That is, in the image forming method of the present invention, in order to ensure that the state of the ink droplets at the time of landing on the base material has a mass reduction rate of 20% or less and a viscosity of 100 mPa ⁇ s or more, if necessary. It may have a step of heating the ink droplets at 30-60 ° C. The temperature is sufficiently low, and there is almost no concern that ink will stick around the head and cause ejection failure.
  • Heating may be performed using a non-contact heating type device such as a constant temperature furnace or a hot air blower, or may be performed using a contact heating type device such as a hot plate or a heat roller. ..
  • the heating temperature is (a) an atmospheric temperature such as a furnace temperature or a hot air temperature, and (b) a hot plate, a hot roller, etc.
  • a contact heating type device such as the above is used, it can be obtained by measuring either the temperature of the contact heating part or (c) the surface temperature of the ink droplets, and the measurement location. (C) It is more preferable to measure the surface temperature of the ink droplets.
  • drying process components other than solid components such as an aqueous solvent (hereinafter, also referred to as “volatile components”) are removed from the ink droplets after the landing step, and a primer is used on the substrate or when a primer layer is provided.
  • a primer is used on the substrate or when a primer layer is provided.
  • the mass reduction rate of the ink droplets after the landing step is within 20%. Since the inkjet ink contains, for example, about 50 to 95% by mass of an aqueous solvent, the remaining volatile components including the aqueous solvent are removed by a drying step.
  • the drying step it is preferable to perform drying under conditions where the fixing resin is not completely fused when the ink contains a fixing resin while removing volatile components.
  • the drying temperature is preferably in the range of, for example, 60 to 110 ° C.
  • the drying time is preferably in the range of, for example, 5 to 60 seconds.
  • the drying in the drying step can be performed by, for example, the same method as the heating in the landing step.
  • the base material that can be used in the present invention is not particularly limited, but is preferably a non-absorbent base material. By using a non-absorbent base material, the effect of the image forming method of the present invention is more remarkable.
  • the non-absorbable means non-absorbable to water.
  • non-water-absorbent base material a known plastic film can be used.
  • plastic films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films.
  • polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, and biodegradable films such as polylactic acid films.
  • a film coated with polyvinylidene chloride on one side or both sides of the film, or a film on which a metal oxide is vapor-deposited can also be preferably used.
  • the non-water-absorbent film can be preferably used as an unstretched film or a stretched film.
  • a base material made of an inorganic compound such as a metal or glass can be mentioned.
  • the packaging material for retort pouch foods can also be suitably used as a packaging material for retort foods in which a thermosetting resin is provided as a coating layer on a metal base material.
  • the packaging material for retort pouch foods blocks air, moisture, and light and seals the food inside. Therefore, for example, polypropylene on the food side and polyester on the outside block air, moisture, and light, and inside. It is composed of a film in which a thermoplastic resin layer and an aluminum foil layer for sealing foods are laminated (laminated).
  • the thickness of the base material is preferably in the range of 10 to 120 ⁇ m, more preferably 12 to 60 ⁇ m.
  • the image forming method of the present invention is applied to image forming using an inkjet head provided with an ink circulation mechanism.
  • the inkjet head is not particularly limited as long as it has an ink circulation mechanism, and may be either an on-demand type or a continuous type inkjet head.
  • on-demand inkjet heads include electro-mechanical conversion methods including single cavity type, double cavity type, bender type, piston type, shared mode type and shared wall type, and thermal inkjet type and bubble jet ( "Bubble jet” includes an electric-heat conversion method including a registered trademark of Canon Inc.).
  • the inkjet head uses a piezoelectric element as the electric-mechanical conversion element used in the electric-mechanical conversion method (also referred to as “piezo-type inkjet head").
  • the inkjet head may be either a scan type or a line type inkjet head, but a line type is preferable.
  • a line-type inkjet head is an inkjet head that has a length greater than or equal to the width of the printing range.
  • the line-type inkjet head one head may be used that is equal to or larger than the width of the print range, or a plurality of heads may be combined so as to be equal to or larger than the width of the print range.
  • a plurality of heads may be arranged side by side so that the nozzles of each head are arranged in a staggered manner to increase the resolution of these heads as a whole.
  • the inkjet head used in the image forming method of the present invention communicates with a pressure chamber in which inkjet ink is injected via an injection path, a pressure generating means for causing pressure fluctuation in the pressure chamber, and the pressure chamber.
  • a nozzle that serves as a flow path for the inkjet ink discharged from the pressure chamber to the outside due to a pressure fluctuation in the chamber communicates with the pressure chamber, and the inkjet ink inside the nozzle is discharged and returned to the injection path. It is preferable to provide two or more circulation paths.
  • Such an inkjet head will be described below with reference to the drawings.
  • FIG. 1 is a schematic configuration diagram of a main part showing an inkjet image forming apparatus 100 including an example of an inkjet head that can be used in the image forming method of the present invention, and shows the inkjet head 1 in a partial cross section.
  • the inkjet head and the like shown in FIG. 1 are examples, and the inkjet head and the like to which the image forming method of the present invention can be applied are not limited thereto.
  • the inkjet image forming apparatus 100 ejects ink droplets from the inkjet head 1 and lands them on a base material 109 conveyed in a certain direction (sub-scanning direction) by the conveying means 108, and dries the droplets. Form an image.
  • the inkjet head 1 is fixedly arranged, and in the process of transporting the base material 109, ink droplets are ejected from the nozzle 22 toward the base material 109 and landed on the base material. Form an image.
  • the inkjet head 1 is mounted on the carriage mechanism 107, and in the process of being reciprocated in the main scanning direction by the carriage mechanism 107, ink is ink from the nozzle 22 toward the base material 109. Droplets are ejected and landed on a substrate to form an image.
  • the transport means 108 and the carriage mechanism 107 are driven and controlled by the control unit 104.
  • the inkjet image forming apparatus 100 has a non-contact heating type or contact heating type heater that adjusts the temperature of ink droplets at the time of landing.
  • the heater can also be used when performing the drying step.
  • the inkjet image forming apparatus 100 is used for inks of various colors such as yellow (Y), magenta (M), cyan (C), and black (K).
  • a plurality of inkjet heads 1 are mounted.
  • the ink tank 101 for storing ink and the common ink chamber 41 of the inkjet head 1 are communicated with each other by an ink transfer tube 102 as a transfer path and an ink return tube 103 as a recovery path.
  • a transfer pump 105a which is driven and controlled by the control unit 104 of the inkjet image forming apparatus 100, is provided in the middle of the ink transfer tube 102. By driving the transfer pump 105a, the ink in the ink tank 101 is transferred to the inkjet head 1 via the ink transfer tube 102.
  • a transfer side sub tank 111a is provided in the middle of the ink transfer tube 102.
  • the transfer-side sub-tank 111a is configured as a buffer space in which ink transferred to the inkjet head 1 is temporarily stored.
  • the pressure of the ink in the ink transfer tube 102 can be controlled by the transfer pressure control pump 110a constituting the pressure control means via the transfer side sub tank 111a.
  • the transfer pressure control pump 110a is controlled by the control unit 104a in the inkjet head 1.
  • a return pump 105b which is driven and controlled by the control unit 104, is provided in the middle of the ink return pipe 103. By driving the return pump 105b, the ink in the inkjet head 1 is returned to the ink tank 101 via the ink return tube 103.
  • a return side sub tank 111b is provided in the middle of the ink return pipe 103.
  • the return-side sub-tank 111b is configured as a buffer space in which the ink returned from the inkjet head 1 is temporarily stored.
  • the pressure of the ink in the ink return pipe 103 can be controlled by the return pressure control pump 110b constituting the pressure control means via the return side sub tank 111b.
  • the return pressure control pump 110b is controlled by the control unit 104a in the inkjet head 1.
  • the pressure control means is not limited to the one composed of the transfer pressure control pump 110a and the return pressure control pump 110b, and may be composed of any of these.
  • the return pressure control pump 110b serves as the first pressure control means
  • the transfer pressure control pump 110a serves as the second pressure control means.
  • the ink tank 101 is not particularly limited, but it is preferable that the ink tank 101 is divided into an ink transfer chamber 101b and an ink return chamber 101c by a partition plate 101a that does not reach the bottom surface of the tank.
  • one end of the ink transfer tube 102 is arranged in the ink transfer chamber 101b, and one end of the ink return tube 103 is arranged in the ink return chamber 101c.
  • the partition plate 101a is provided to sufficiently degas the ink so that the bubbles contained in the ink returned to the ink return chamber 101c do not flow into the ink transfer tube 102 again. Since the bubbles themselves have high buoyancy, it is possible to prevent the bubbles from passing under the partition plate 101a and flowing into the ink transfer chamber 101b.
  • Such an embodiment is a preferred embodiment when the ink is used in a circulating manner.
  • the inkjet head 1 includes an ink manifold 4 constituting a common ink chamber 41, a wiring board 3 bonded to the ink manifold 4, a head chip 2 bonded to a lower surface portion of the wiring board 3, and a lower surface of the head chip 2. It is configured to have a nozzle plate 21 adhered to the portion.
  • the ink manifold 4 is formed of a synthetic resin material or the like in a horizontally long box shape having an opening 4a on the lower surface. In the ink manifold 4, the opening 4a is closed by a wiring board 3 adhered to a lower surface portion.
  • the internal space of the ink manifold 4 serves as a common ink chamber 41 in which the ink transferred from the ink tank 101 is stored.
  • the wiring board 3 is, for example, a glass substrate.
  • the wiring board 3 is formed with a wiring pattern (not shown) connected to a power supply circuit (not shown) via an FPC board.
  • an ink supply pipe 5a serving as a flow path for supplying ink into the common ink chamber 41 is continuously provided.
  • the ink supply pipe 5a communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3.
  • a connecting portion 7a is provided on the upper end side of the ink supply tube 5a.
  • the connection portion 7a is detachably connected to the connection portion 106a on the inkjet image forming apparatus 100 side.
  • the connection portion 106a on the inkjet image forming apparatus 100 side communicates with the ink transfer tube 102.
  • an ink recovery tube 5b that serves as a flow path for collecting ink from the common ink chamber 41 is continuously provided.
  • the ink recovery tube 5b communicates with the common ink chamber 41 on the side (upper side) far from the wiring board 3.
  • a connecting portion 7b is provided on the upper end side of the ink recovery tube 5b.
  • the connecting portion 7b is detachably connected to the connecting portion 106b on the inkjet image forming apparatus 100 side.
  • the connection portion 106b on the inkjet image forming apparatus 100 side communicates with the ink return tube 103.
  • the inkjet head 1 can collect the ink from the common ink chamber 41 and return the ink to the ink tank 101.
  • the flow path from the ink supply tube 5a to the buffer space 6 in the middle of the ink recovery tube 5b is the main flow path F1.
  • FIG. 2 is an enlarged cross-sectional view of the head chip 2 of the inkjet head 1.
  • FIG. 3 is a plan view of the nozzle plate 21 of the inkjet head 1.
  • a plurality of ink channels (pressure chambers) 23 and a plurality of dummy channels (pseudo pressure chambers) 25 are formed on the head chip 2.
  • Each ink channel 23 and each dummy channel 25 are through holes formed from the upper surface portion to the lower surface portion of the head chip 2.
  • the upper end of each ink channel 23 communicates with the common ink chamber 41 via an injection hole 31a provided in the wiring board 3.
  • Each ink channel 23 is filled with ink flowing in from the injection hole 31a by the potential energy of the ink in the ink tank 101 and the pressure controlled by the transfer pressure control pump 110a due to the transfer pump 105a.
  • each ink channel 23 communicates outward (downward) via the nozzle 22.
  • the inside of the nozzle 22 is inside the ink channel 23.
  • the inside of the nozzle 22 is inside the communication passage.
  • the upper end of each dummy channel 25 is closed by the wiring board 3, and the lower end is closed by the nozzle plate 21 to form a closed air chamber.
  • Each ink channel 23 and each dummy channel 25 are arranged in one direction (in the direction of arrow X in FIG. 2) to form a channel sequence.
  • Both wall portions (partition wall between the ink channel 23 and the dummy channel 25) of each ink channel 23 are composed of a pair of piezoelectric elements (driving walls) 24 and 24 that serve as pressure generating means.
  • the piezoelectric elements 24, 24 are sheared and deformed by applying a voltage from a power supply circuit (not shown) through the wiring patterns of the FPC substrate and the wiring substrate 3.
  • the piezoelectric elements 24, 24 forming both walls of the ink channel 23 are sheared and deformed, so that the pressure of the ink channel 23 fluctuates (decompression due to expansion or pressure increase due to contraction). Due to the pressure fluctuation (depressurization or pressure increase) of the ink channel 23, pressure is applied to the ink inside the nozzle 22, that is, in the ink channel 23, and this ink is ejected through the nozzle 22.
  • each ink channel 23 Two piezoelectric elements 24 and 24 are provided for each ink channel 23, forming both wall portions of each ink channel 23. There is a gap between the piezoelectric element 24 forming the wall portion of one ink channel 23 and the piezoelectric element 24 forming the wall portion of the adjacent ink channel 23, and this gap is the dummy channel 25. Therefore, each ink channel 23 can be driven (decompressed or increased in pressure) independently.
  • An introduction path 425 is formed in the head tip 2.
  • the introduction path 425 is provided so as to be located outside the channel row on one end side of the channel row formed by each ink channel 23 and each dummy channel 25.
  • the introduction path 425 is a through hole formed from the upper surface portion to the lower surface portion of the head chip 2, and the cross-sectional opening area is larger than the cross-sectional opening area of one ink channel 23.
  • the introduction path 425 communicates with the common ink chamber 41 through an introduction hole 31c whose upper end is provided in the wiring board 3, and the transfer pressure is controlled due to the potential energy of the ink in the ink tank 101 and the transfer pump 105a. Ink flows in through the introduction hole 31c by the pressure controlled by the pump 110a.
  • a plurality of nozzles 22 corresponding to each ink channel 23 are bored in the flat plate-shaped nozzle plate 21 adhered to the lower surface of the head chip 2.
  • the nozzle 22 is a through hole that allows the ink channel 23 to communicate with the outside.
  • the ink in each ink channel 23 is subjected to ejection pressure by the action of the piezoelectric element 24, and is ejected toward the external (lower) base material through the nozzle 22. That is, the nozzle 22 serves as a flow path for ink discharged from the inside of each ink channel 23 to the outside (downward).
  • the lower surface of the nozzle plate 21 is the ink ejection surface 1S.
  • the inkjet head 1 is provided with a nozzle circulation mechanism that discharges the ink injected into the ink channel 23 from the vicinity of the nozzle 22 and returns it to the injection path to the ink channel 23.
  • Two individual ink circulation paths 26a and 26a are communicated with each ink channel 23, respectively.
  • the individual ink circulation paths 26a and 26a communicate with the ink channel 23 at both ends in the longitudinal direction of the cross section of the ink channel 23. Since air bubbles often remain in the vicinity of both ends of the ink channel 23, it is preferable to provide the individual ink circulation paths 26a and 26a at both ends of the ink channel 23 in the longitudinal direction of the cross section.
  • the individual ink circulation paths 26a and 26a may communicate with the ink channel 23 at any position of the ink channel 23.
  • the number of individual ink circulation paths 26a for one ink channel 23 may be increased or decreased, but it is preferably two or more.
  • Thixotropy occurs in inks to which a temperature-responsive polymer or fixing resin is added, but if there are two or more circulation paths as described above, ink retention is unlikely to occur even if such inks are used, and nozzles It has the effect of easily removing nearby bubbles.
  • the individual ink circulation paths 26a and 26a are formed by closing a flow path forming groove 28 formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the nozzle 22 by the lower surface of the head tip 2. Has been done.
  • Two introduction grooves 425a and 425a are communicated with the introduction path 425.
  • the introduction grooves 425a and 425a communicate with the introduction path 425 at both sides of the introduction path 425.
  • the introduction grooves 425a and 425a may communicate with the introduction path 425 at any position on the introduction path 425. Further, the number of introduction grooves 425a and 425a for one introduction path 425 may be increased or decreased.
  • the introduction grooves 425a and 425a are formed on the upper surface of the nozzle plate 21 with a start end in the vicinity of the introduction path 425, and are closed by the lower surface of the head tip 2 to form a flow path.
  • a common ink circulation path 421 is formed on the lower surface of the head chip 2.
  • the common ink circulation path 421 is formed by abutting a groove formed on the lower surface portion of the head chip 2 and a groove 422 formed on the upper surface portion of the nozzle plate 21.
  • the common ink circulation path 421 is composed of a plurality of flow paths formed in the direction of the channel row (X direction).
  • the individual ink circulation paths 26a and 26a communicating with the ink channels 23 are joined by communicating with the common ink circulation path 421. Due to the pressure difference between each ink channel 23 and the common ink circulation path 421, ink flows from each ink channel 23 to the common ink circulation path 421. Further, the introduction grooves 425a and 425a communicate with the common ink circulation path 421. Due to the pressure difference between the introduction path 425 and the common ink circulation path 421, ink flows from the introduction path 425 to the common ink circulation path 421. Then, these flows merge to generate ink flow in the common ink circulation path 421.
  • the other end side of the common ink circulation path 421 communicates with the lower end of the discharge channel 424 formed in the head chip 2.
  • the discharge channel 424 is provided so as to be located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. Since the ink flow rate in the discharge channel 424 is larger than the ink flow rate in the introduction path 425 by the amount of ink merging through each ink channel 23, the ink flow rate crosses the discharge channel 424 in order not to increase the flow path resistance. Increase the surface opening area.
  • the ink discharged from the individual ink circulation path 26a communicating with the ink channel 23, which is the pressure chamber, to the common ink circulation path 421 reaches the buffer space 6 via the discharge channel 424, the ink discharge chamber 412, and the ink discharge pipe 5c. Further, it is returned to the ink tank 101 by the above route. Then, it is introduced into the injection path to the ink channel 23 again.
  • an ink discharge chamber 412 is provided in the ink manifold 4 located above the discharge channel 424.
  • the ink discharge chamber 412 is provided adjacent to the common ink chamber 41 in the ink manifold 4.
  • the ink discharge chamber 412 is separated from the common ink chamber 41 by a partition wall 45.
  • the partition wall 45 can be integrally formed with the ink manifold 4.
  • An ink discharge pipe 5c forming a flow path for discharging ink from the inside of the ink discharge chamber 412 is connected to the ink discharge chamber 412 via a circulation path connecting portion 5d.
  • the circulation path connecting portion 5d is located above the discharge channel 424 and is located outside the channel row on the other end side of the channel row formed by each ink channel 23 and each dummy channel 25. ..
  • the upper end side of the ink discharge tube 5c joins the ink recovery tube 5b.
  • the ink recovery pipe 5b and the ink discharge pipe 5c are joined by being connected to the buffer space portion 6.
  • the introduction path 425 and the individual ink circulation paths 26a and 26a reach the buffer space 6 via the common ink circulation path 421, the discharge channel 424, the discharge hole 31b, the ink discharge chamber 412, and the ink discharge pipe 5c.
  • the flow path becomes the circulation path 423.
  • the circulation path 423 is a flow path that communicates with the introduction path 425 and the ink channel 23, discharges the ink in the introduction path 425 and the ink channel 23, and joins the ink recovery tube 5b in the buffer space 6.
  • the circulation path 423 discharges ink from the individual ink circulation paths 26a and 26a in the vicinity of the nozzle 22 and returns this ink to the injection path to the ink channel 23, it is necessary to limit the route in the middle. No. Then, through the introduction hole 31c and each injection hole 31a, up to the circulation path 423 becomes the sub-flow path F2.
  • the pigment dispersion liquid obtained above and each of the above components were mixed so as to have the composition shown in Table I or Table II, and the obtained mixed liquid was filtered through a 1 ⁇ m filter to obtain an inkjet ink.
  • the content (mass%) of each component indicates the content of the solid content contained in the component when a dispersion liquid or a solution is used as the component.
  • the content of the polyester resin itself excluding the amount of water as a dispersion medium is 5.0% by mass.
  • blanks in the composition column of Table I or Table II indicate that the component is not contained.
  • LCST + 5 ° C means LCST + 5 ° C with respect to water of the temperature-responsive polymer contained in each ink.
  • the measurement temperature was set to 60 ° C. instead of LCST + 5 ° C.
  • (A2) if the viscosity at a shear rate of 1 (1 / s) at LCST + 5 ° C. is 45 mPa ⁇ s or more, the above condition (1-2) is satisfied.
  • (A3) if the viscosity at a shear rate of 1 (1 / s) at an ink drying rate of 20% is 100 mPa ⁇ s or more, the above condition (1-3) is satisfied.
  • FIG. 4 shows the loss tangent (tan ⁇ ), storage elastic modulus G ′ (logarithm), loss elastic modulus G ′′ (logarithm) and strain (logarithm) measured under the above conditions with an ink drying rate of 20% for the ink of Example 1. ) Is shown. From the graph, the loss tangent (tan ⁇ ) at 1% strain of (A5) and the crossover strain of (A6) can be obtained.
  • the base material fixability of the ink coating film was evaluated by the following method.
  • the ink coating film was obtained by applying ink on a substrate with a wire bar # 7 and drying at 100 ° C. for 3 minutes. Cut the obtained ink coating film (100 mm x 100 mm, thickness 10 ⁇ m) with a cutter so that 25 squares of 5 vertical ⁇ 5 horizontal are formed, and attach Nichiban's cellophane tape (registered trademark).
  • the peeled state was evaluated according to the following evaluation criteria.
  • the ink ejection property from the head is good and a high quality printed image can be obtained.
  • the inkjet ink of the present invention it is possible to maintain good ejection performance and to form a high-quality image in the image formation by the inkjet method. Further, according to the image formation of the present invention, it is possible to form a high-quality image with good workability in the image formation by the inkjet method.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Ink Jet Recording Methods And Recording Media Thereof (AREA)
  • Inks, Pencil-Leads, Or Crayons (AREA)

Abstract

La présente invention concerne une encre pour impression jet d'encre (ci-après appelée « encre ») qui comprend un solvant aqueux, un pigment, une résine de fixation et un polymère sensible à la température, et est caractérisée en ce qu'elle comprend, par rapport à l'encre entière, une teneur en pigment dans la plage de 2 à 10 % en masse, une teneur en résine de fixation dans la plage de 2 à 10 % en masse et une teneur en le polymère sensible à la température dans la plage de 0,01 à 1 % en masse. Ledit procédé de formation d'une image comprend une étape de distribution d'encre dans laquelle des gouttelettes d'une encre sont éjectées d'une tête d'impression jet d'encre équipée d'un mécanisme de circulation d'encre et sont distribuées à une base, et est caractérisé en ce que l'encre est mise en circulation de sorte que l'encre à l'intérieur de la tête d'impression jet d'encre présente une viscosité de 15 mPa·s ou moins et l'étape de distribution d'encre est réalisée de sorte que les gouttelettes au moment de la distribution à la base ou immédiatement après la distribution présentent une perte de masse par rapport à l'encre de 20 % ou moins et présentent une viscosité de 100 mPa·s ou plus.
PCT/JP2021/004862 2020-02-28 2021-02-10 Encre pour impression jet d'encre et procédé de formation d'image WO2021172008A1 (fr)

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
JP7249476B1 (ja) * 2021-11-18 2023-03-30 関西ペイント株式会社 光輝性塗料組成物、及び複層塗膜形成方法
WO2023090130A1 (fr) * 2021-11-18 2023-05-25 関西ペイント株式会社 Composition de matériau de revêtement photoluminescent et méthode de formation de film de revêtement multicouche
EP4112311A4 (fr) * 2020-02-28 2023-08-16 Konica Minolta, Inc. Encre pour impression jet d'encre et procédé de formation d'image

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JPH05331395A (ja) * 1992-06-01 1993-12-14 Seiko Epson Corp 水性記録用インク
JPH07109431A (ja) * 1993-10-13 1995-04-25 Minolta Co Ltd インクジェット用記録液
JPH08176480A (ja) * 1994-12-27 1996-07-09 Seiko Epson Corp 画像形成用インク及びその製造方法
JP2006096857A (ja) * 2004-09-29 2006-04-13 Konica Minolta Holdings Inc インクジェットインク及びそれを用いた記録方法
JP2010248313A (ja) * 2009-04-13 2010-11-04 Kishu Giken Kogyo Kk インクジェットインキ、その製造方法およびその使用方法
JP2014159520A (ja) * 2013-02-20 2014-09-04 Kishu Giken Kogyo Kk インクジェットインキ、その製造方法、およびその使用方法
JP2016011328A (ja) * 2014-06-27 2016-01-21 Dic株式会社 水性顔料組成物、捺染剤及び布帛物
JP2021020394A (ja) * 2019-07-29 2021-02-18 株式会社リコー 液体組成物、インクセット、印刷方法、及び印刷装置
JP2021042273A (ja) * 2019-09-06 2021-03-18 株式会社リコー インクセット、セット、印刷方法、及び印刷装置

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05331395A (ja) * 1992-06-01 1993-12-14 Seiko Epson Corp 水性記録用インク
JPH07109431A (ja) * 1993-10-13 1995-04-25 Minolta Co Ltd インクジェット用記録液
JPH08176480A (ja) * 1994-12-27 1996-07-09 Seiko Epson Corp 画像形成用インク及びその製造方法
JP2006096857A (ja) * 2004-09-29 2006-04-13 Konica Minolta Holdings Inc インクジェットインク及びそれを用いた記録方法
JP2010248313A (ja) * 2009-04-13 2010-11-04 Kishu Giken Kogyo Kk インクジェットインキ、その製造方法およびその使用方法
JP2014159520A (ja) * 2013-02-20 2014-09-04 Kishu Giken Kogyo Kk インクジェットインキ、その製造方法、およびその使用方法
JP2016011328A (ja) * 2014-06-27 2016-01-21 Dic株式会社 水性顔料組成物、捺染剤及び布帛物
JP2021020394A (ja) * 2019-07-29 2021-02-18 株式会社リコー 液体組成物、インクセット、印刷方法、及び印刷装置
JP2021042273A (ja) * 2019-09-06 2021-03-18 株式会社リコー インクセット、セット、印刷方法、及び印刷装置

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4112311A4 (fr) * 2020-02-28 2023-08-16 Konica Minolta, Inc. Encre pour impression jet d'encre et procédé de formation d'image
JP7249476B1 (ja) * 2021-11-18 2023-03-30 関西ペイント株式会社 光輝性塗料組成物、及び複層塗膜形成方法
WO2023090130A1 (fr) * 2021-11-18 2023-05-25 関西ペイント株式会社 Composition de matériau de revêtement photoluminescent et méthode de formation de film de revêtement multicouche

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