Water-based white inkjet ink and method for producing printed materials

Abstract

To provide aqueous white inkjet ink which is excellent in properties when being left open.SOLUTION: Aqueous white inkjet ink contains a white pigment, a water dispersible urethane resin, an amine compound having a molecular weight of 110-150, and water, wherein the amine compound having the molecular weight of 110-150 is 0.2-1.3 mass% with respect to the total amount of ink, and a mass ratio (mass of amine compound having molecular weight of 110-150) / (mass of water dispersible urethane resin) of the amine compound having the molecular weight of 110-150 to the water dispersible urethane resin satisfies 0.02 to 0.08.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based white inkjet ink and a method for producing a textile print. [Background technology]

[0002] Inkjet recording systems are printing systems that spray highly fluid liquid ink from minute nozzles and deposit it onto a substrate. These systems have recently become increasingly popular due to their ability to print high-resolution, high-quality images at high speed and with low noise using relatively inexpensive equipment. Water-based inks are becoming increasingly popular because they can produce high-quality prints at low cost. Water-based inks contain water, which improves drying properties and also has the advantage of being environmentally friendly.

[0003] For aqueous inkjet inks, technologies have been developed to disperse pigments in the ink while reducing the viscosity of the ink, from the perspective of ejection performance from inkjet nozzles. However, pigments with high specific gravity, such as white pigments, tend to settle in the ink and are difficult to redisperse after settling. Furthermore, the addition of a resin component to aqueous inkjet inks can improve the fixation of ink images to the substrate and further increase the coating strength of the ink images. Water-dispersible urethane resins are excellent resin components, particularly in terms of the coating strength of ink images. However, adding a large amount of resin to increase coating strength tends to further deteriorate the open-standing performance. Deterioration of open-standing performance is one factor that contributes to poor ejection performance.

[0004] Patent Document 1 (JP 2015-124271 A) proposes an ink containing titanium dioxide pigment with a hydrophobic surface treatment, resin particles, and water, which is an ink in which the inorganic pigment is resistant to settling and can be redispersed even after settling. Patent Document 2 (JP 2012-149184 A) proposes an inkjet recording method that has good ejection stability and produces printed matter with high whiteness, in which a white ink composition containing a fluorene-based resin, a styrene-acrylic resin, a white pigment, and water is ejected onto a swelling-type non-recording medium. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-124271 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-149184 Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques disclosed in Patent Documents 1 and 2 are intended for forming white images on OHP sheets and the like, and therefore do not fully address the issue of improving coating strength. Furthermore, in conventional aqueous inkjet inks, amine compounds are used as pH adjusters or water-soluble organic solvents, as disclosed in Patent Documents 1 and 2. When used as a pH adjuster, the content of the amine compound is reduced, taking into consideration the ink formulation and the basicity of the amine compound, etc. Furthermore, when an amine compound is used as a water-soluble organic solvent, the content of the amine compound may be adjusted within a range that allows the amine compound to function as a solvent. As described above, with conventional techniques, it is difficult to obtain good open-standing stability while increasing the coating strength of an ink image by combining a water-dispersible urethane resin capable of improving coating strength with a white pigment, and this problem has not been resolved. Furthermore, in aqueous inkjet inks, amine compounds are generally blended in small amounts as pH adjusters, and the function of the amine compounds themselves has not been fully elucidated.

[0007] If the white pigment settles due to a decrease in its dispersibility in the ink, and if it becomes difficult to redisperse after settling, the ink will dry out and become more likely to solidify when exposed to the atmosphere. Furthermore, if a water-dispersible urethane resin is added to the ink to increase the coating strength, the reduced water content will make the ink more likely to solidify. If solidification occurs when the ink is filled into the inkjet nozzle, that is, when the ink is exposed to the atmosphere, it will be one of the causes of reduced on-machine stability.

[0008] An object of the present invention is to provide a water-based white inkjet ink that has excellent open storage stability. [Means for solving the problem]

[0009] One aspect of the present invention is an aqueous white inkjet ink comprising a white pigment, a water-dispersible urethane resin, an amine compound having a molecular weight of 110 to 150, and water, wherein the amine compound having a molecular weight of 110 to 150 accounts for 0.2 to 1.3 mass% of the total amount of the ink, and the mass ratio of the amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin satisfies (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the water-dispersible urethane resin) = 0.02 to 0.08.

[0010] Another aspect of the present invention is a method for producing a printed textile, comprising applying the above-mentioned water-based white inkjet ink to a fabric by an inkjet system, and applying a color ink to the fabric to which the water-based white inkjet ink has been applied, to form an image. [Effects of the Invention]

[0011] According to one embodiment of the present invention, it is possible to provide a water-based white inkjet ink that exhibits excellent stability when left open. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below using one embodiment. The present invention is not limited to the examples in the following embodiment. The terms and expressions in the following description are not limited to the specific examples in the following examples.

[0013] <Water-based white inkjet ink> An aqueous white inkjet ink according to one embodiment comprises a white pigment, a water-dispersible urethane resin, an amine compound having a molecular weight of 110 to 150, and water, wherein the amine compound having a molecular weight of 110 to 150 accounts for 0.2 to 1.3 mass% of the total amount of the ink, and the mass ratio of the amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin satisfies (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the water-dispersible urethane resin) = 0.02 to 0.08. This makes it possible to provide a water-based white inkjet ink that has excellent properties when left open. In the following description, the water-based white inkjet ink may be simply referred to as white ink or ink.

[0014] In water-based white inks, the white pigment used is a pigment with a high specific gravity, such as titanium oxide pigment, and therefore the white pigment tends to settle when the white ink is left standing. When the white pigment settles in the white ink, the white pigment and the organic components in the ink tend to adhere to each other, making it difficult to redisperse. It is thought that organic components in the ink, such as resin particles, water-soluble organic solvents, and surfactants, interact with the white pigment to cause the adhesion. When the white pigment settles or adheres to the ink, the ink becomes more likely to solidify when exposed to the atmosphere, which can reduce the ink's ability to stand in the open air.

[0015] In aqueous inkjet inks, water-dispersible urethane resins can improve the fixation of ink images and the strength of coatings on substrates, but they tend to adhere to the white pigment. When the white pigment settles in the ink, the adhesion between the white pigment and the water-dispersible urethane resin tends to reduce the redispersibility of the white pigment.

[0016] Amine compounds with a molecular weight of 110 to 150 aid in the dispersion stability of the white pigment and water-dispersible urethane resin, inhibit adhesion between the white pigment and the water-dispersible urethane resin even when the white pigment has settled, and improve redispersibility. Furthermore, because amine compounds with a molecular weight of 110 to 150 are less likely to volatilize from the ink, volatilization from the supernatant can be inhibited even when the white pigment has settled. This improves the ink's stability when left unattended. On the other hand, because amine compounds with a molecular weight of 110 to 150 are basic, their inclusion in inks in amounts exceeding the specified amount may reduce the ink's dispersion stability.

[0017] In the white ink, the amine compound having a molecular weight of 110 to 150 is preferably present in an amount of 0.2 to 1.3% by mass relative to the total amount of ink. When the amine compound having a molecular weight of 110 to 150 is present in an amount of 0.2% by mass or more relative to the total amount of ink, the effect of aiding the dispersion stability of the white pigment and water-dispersible urethane resin can be obtained. When the amine compound having a molecular weight of 110 to 150 is present in an amount of 1.3% by mass or less relative to the total amount of ink, the influence of basicity can be reduced and a decrease in the dispersion stability of the ink can be prevented. When the white ink contains two or more amine compounds having molecular weights of 110 to 150, it is preferable that the total content of the two or more amine compounds having molecular weights of 110 to 150 satisfy this range.

[0018] Furthermore, in the white ink, the mass ratio of the amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin preferably satisfies (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the water-dispersible urethane resin) = 0.02 to 0.08. A mass ratio of 0.02 or greater can enhance the dispersion stability of the white pigment and the water-dispersible urethane resin. A mass ratio of 0.08 or less can reduce the effects of basicity and prevent a decrease in the dispersion stability of the ink. When the white ink contains two or more amine compounds having a molecular weight of 110 to 150 or two or more water-dispersible urethane resins, the total amount of the two or more amine compounds having a molecular weight of 110 to 150 or the total content of the two or more water-dispersible urethane resins preferably satisfies this range.

[0019] In other words, by specifying the content of the amine compound having a molecular weight of 110 to 150 relative to the total amount of ink, as well as the mass ratio of the amine compound having a molecular weight of 110 to 150 relative to the water-dispersible urethane resin, it is possible to appropriately control the content of the amine compound having a molecular weight of 110 to 150 in the ink, thereby improving the ink's ability to stand when left unattended.

[0020] The amine compounds having a molecular weight of 110 to 150 will be described below. By ensuring that the molecular weight of the amine compound is 110 or greater, the volatility of the amine compound when left open to the atmosphere is reduced, the amount of amine compound in the ink is maintained at an appropriate level, and the effect of supporting the dispersion stability of the white pigment and water-dispersible urethane resin can be obtained. When the molecular weight of the amine compound is 150 or less, the solubility in aqueous solvents is increased, and the effect of assisting the dispersion stability of the white pigment and the water-dispersible urethane resin can be obtained. The amine compound is preferably a water-soluble compound, and is preferably a compound that dissolves in 100 g of water at 25° C. in an amount of, for example, 0.1 g or more, 1 g or more, or 5 g or more.

[0021] The amine compound having a molecular weight of 110 to 150 may be either an aliphatic amine or an aromatic amine, or a combination of these may be used, but is preferably an aliphatic amine. The aliphatic amine may be a compound having an amino group and a saturated or unsaturated, linear or branched hydrocarbon group. Preferably, it is an alkylamine.

[0022] The amine compound having a molecular weight of 110 to 150 may be an amine compound having a hydroxy group. For example, amino alcohols may be mentioned, and alkanolamines are preferred. In the amine compound having a hydroxy group, the number of hydroxy groups relative to the molecular weight is preferably 0.015 or more, more preferably 0.016 or more, and even more preferably 0.020 or more, from the viewpoint of water solubility. For example, in an amine compound having a hydroxy group, the number of hydroxy groups relative to the molecular weight is preferably from 0.015 to 0.045, more preferably from 0.016 to 0.035, and even more preferably from 0.020 to 0.030. In the amine compound having a hydroxy group, the number of hydroxy groups is preferably 1 to 5, more preferably 1 to 4, and even more preferably 1 to 3.

[0023] The amine compound having a molecular weight of 110 to 150 may be a monoamine or a polyamine such as a diamine or triamine, or a combination of these may be used. From the viewpoint of adjusting basicity, the amine compound having a molecular weight of 110 to 150 is preferably a monoamine, and among them, alkyl monoamines and monoamino alcohols are more preferred, monoamino alcohols are even more preferred, and alkanol monoamines are still more preferred. From the viewpoint of adjusting solubility and basicity, the amine compound having a molecular weight of 110 to 150 is preferably a compound that does not contain heteroatoms except for nitrogen atoms and oxygen atoms contained in hydroxy groups.

[0024] The amine compound having a molecular weight of 110 to 150 may be any of a primary amine compound, a secondary amine compound, and a tertiary amine compound, and these may be used in combination.

[0025] When the white ink contains a primary amine compound as an amine compound having a molecular weight of 110 to 150, the content of this primary amine compound is preferably 0.2 to 1.3% by mass of the total ink. From the viewpoint of preventing the ink from drying and improving its stability when left unattended, the content is more preferably 0.2 to 0.4% by mass, and even more preferably 0.25 to 0.30% by mass. The primary amine compound may have one or more -NH2 groups per molecule, and is preferably a primary monoamine compound having one -NH2 group per molecule. Here, the single functional group bonded to the nitrogen atom may be any monovalent group, such as a saturated or unsaturated, linear or branched aliphatic hydrocarbon group, or a group in which the hydrogen atom of such a functional group is substituted with a hydroxy group. Examples of primary amine compounds include 2-amino-2-ethyl-1,3-propanediol and tris(hydroxymethyl)aminomethane.

[0026] The mass ratio of the primary amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin (mass of the primary amine compound having a molecular weight of 110 to 150) / (water-dispersible urethane resin) is preferably 0.02 to 0.08, and more preferably 0.02 or more but less than 0.03, from the viewpoint of suppressing drying of the ink and further improving the ability to leave it in the open.

[0027] When the white ink contains a tertiary amine compound as an amine compound having a molecular weight of 110 to 150, the content of this tertiary amine compound is preferably 0.2 to 1.3 mass% of the total ink. From the viewpoint of suppressing drying of the ink and further improving its ability to be left unattended, the content of this tertiary amine compound is preferably 1.1 to 1.3 mass%, and more preferably 1.20 to 1.25 mass%. The tertiary amine compound may have one or more -NRR' groups per molecule, and is preferably a tertiary monoamine compound having one -NRR' group per molecule. Here, the single functional group bonded to the nitrogen atom, R and R', are each independently any monovalent group, such as a saturated or unsaturated, linear or branched aliphatic hydrocarbon group, or a group in which the hydrogen atom of such a functional group is substituted with a hydroxy group. Examples of tertiary amine compounds include triethanolamine.

[0028] The mass ratio of the tertiary amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin (mass of the tertiary amine compound having a molecular weight of 110 to 150) / (water-dispersible urethane resin) is preferably 0.02 to 0.08, and from the viewpoint of suppressing drying of the ink and further improving the ability to leave the ink in the open, it is more preferably more than 0.06 and 0.08 or less, and even more preferably 0.07 or more and 0.08 or less.

[0029] When the white ink contains a secondary amine compound as an amine compound having a molecular weight of 110 to 150, the amount of this secondary amine compound is preferably 0.2 to 1.3 mass% of the total amount of ink. The secondary amine compound may have one or more -NH- groups per molecule, and preferably has one -NH- group per molecule. Here, the two functional groups bonded to the nitrogen atom are each independently any monovalent group, such as a saturated or unsaturated, linear or branched aliphatic hydrocarbon group, or a group in which the hydrogen atom of such a functional group is substituted with a hydroxy group. Examples of secondary amine compounds include dipropanolamine.

[0030] The mass ratio of the secondary amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin (mass of the secondary amine compound having a molecular weight of 110 to 150) / (water-dispersible urethane resin) is preferably 0.02 to 0.08.

[0031] In the white ink, the mass ratio of the amine compound having a molecular weight of 110 to 150 to the white pigment (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the titanium oxide pigment) is preferably 0.02 to 0.13, and more preferably 0.02 to 0.125. Within these ranges, drying of the ink is suppressed, and the ink can be left unattended for a longer period of time.

[0032] When the white ink contains a primary amine compound as the amine compound having a molecular weight of 110 to 150, the mass ratio of the primary amine compound having a molecular weight of 110 to 150 to the white pigment (mass of the primary amine compound having a molecular weight of 110 to 150) / (mass of the titanium oxide pigment) is preferably 0.02 to 0.13, and more preferably 0.03 to 0.04 from the viewpoint of further suppressing drying of the ink. When the white ink contains a tertiary amine compound as the amine compound having a molecular weight of 110 to 150, the mass ratio of the tertiary amine compound having a molecular weight of 110 to 150 to the white pigment (mass of the tertiary amine compound having a molecular weight of 110 to 150) / (mass of the titanium oxide pigment) is preferably 0.02 to 0.13, and more preferably 0.12 to 0.13 from the viewpoint of further suppressing drying of the ink. When the white ink contains a secondary amine compound as the amine compound having a molecular weight of 110 to 150, the mass ratio of the secondary amine compound having a molecular weight of 110 to 150 to the white pigment (mass of the secondary amine compound having a molecular weight of 110 to 150) / (mass of the titanium oxide pigment) is preferably 0.02 to 0.13.

[0033] The white ink may contain one or more amine compounds having a molecular weight of 110 to 150. For example, the white ink may contain a combination of two or more amine compounds having a molecular weight of 110 to 150 selected from primary amine compounds, secondary amine compounds, and tertiary amine compounds.

[0034] A water-dispersible urethane resin is a resin that contains a urethane structure and is water-dispersible. Examples include homopolymers or copolymers having urethane bonds in the main chain, and copolymers having side chains with urethane bonds. The water-dispersible urethane resin forms a resin coating on a substrate, which can improve the fixation of ink images and the strength of the coating. Furthermore, because the water-dispersible urethane resin is a relatively soft resin with high film elongation, it can suppress a decrease in ink fluidity when exposed to the atmosphere, thereby further improving the open-standing performance of the ink.

[0035] The water-dispersible urethane resin is preferably a resin particle that can be dispersed in an aqueous solvent, and can be incorporated into the ink as an oil-in-water resin emulsion, for example. The water-dispersible urethane resin may be a self-emulsifying resin in which hydrophilic groups and / or hydrophilic segments are introduced to stably disperse it in water, or it may be a resin that becomes water-dispersible by the use of an external emulsifier. The water-dispersible urethane resin is preferably a resin that forms a transparent coating film so as not to affect the color of the white pigment.

[0036] The water-dispersible urethane resin may be any of anionic resin, cationic resin, amphoteric resin, and nonionic resin. In consideration of the stability of the colorant in the aqueous ink, anionic resin, amphoteric resin, nonionic resin, or a combination thereof can be preferably used, and anionic resin is more preferred. As the water-dispersible urethane resin, anionic urethane resin having an anionic functional group such as a carboxy group, a sulfo group, or a phosphate group is preferred.

[0037] The water-dispersible urethane resin is preferably a polyether-type urethane resin containing an ether bond in the main chain in addition to the urethane skeleton, a polyester-type urethane resin containing an ester bond in the main chain, a polyester-ether-type urethane resin containing an ester bond and an ether bond in the main chain, or a polycarbonate-type urethane resin containing a carbonate bond in the main chain.

[0038] The water-dispersible urethane resin may be either an aliphatic urethane resin or an aromatic urethane resin, but from the viewpoint of the transparency of the coating film, an aliphatic urethane resin is preferred. The aliphatic urethane resin can be a reaction product of an aliphatic polyisocyanate and a polyol, such as polyether polyol, polyester polyol, polyester-ether polyol, or polycarbonate polyol.

[0039] As the aliphatic polyisocyanate, an aliphatic polyisocyanate compound having two or more isocyanate groups in one molecule can be used, and an aliphatic diisocyanate is preferred. In the water-dispersible urethane resin, when the urethane skeleton portion is an aliphatic urethane skeleton, more preferably when the urethane skeleton portion is derived from an aliphatic diisocyanate and is chain-like, the strength of the ink image can be further increased and flexibility of the ink image can be obtained. Furthermore, when a water-dispersible urethane resin synthesized from an aliphatic polyisocyanate is used, yellowing of the urethane resin itself can be prevented, the resin coating film becomes more transparent, and the whiteness of the white ink can be further improved.

[0040] Specific examples of aliphatic polyisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl)fumarate, bis(2-isocyanatoethyl)carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. Among these, from the viewpoint of improving the flexibility of the ink image, pentamethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, or a combination thereof is preferred. These may be used alone or in combination of two or more.

[0041] As the polyether polyol, a polyether compound having two or more hydroxyl groups in one molecule can be used, preferably a chain polyether compound having two or more hydroxyl groups, and more preferably a polyether diol. As the polyester polyol, a polyester compound having two or more hydroxyl groups in one molecule can be used, preferably a chain polyester compound having two or more hydroxyl groups, and more preferably a polyester diol. As the polycarbonate polyol, a polycarbonate compound having two or more hydroxyl groups in one molecule can be used, preferably a chain polycarbonate compound having two or more hydroxyl groups, and more preferably a polycarbonate diol.

[0042] In the water-dispersible urethane resin, when the ether bond, ester bond, or carbonate bond is a chain bond, more preferably when the chain bond is derived from a polyether diol, polyester diol, or polycarbonate diol, the strength of the ink image can be further increased. Furthermore, when a water-dispersible urethane resin synthesized from a polyether polyol is used, the ether moiety is not affected by hydrolysis, so yellowing of the ink image can be further reduced and the water resistance of the ink image can be further improved. Furthermore, the use of a polycarbonate polyol allows the formation of an ink image with higher coating strength.

[0043] Specific examples of polyether polyols include polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; low molecular weight polyols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol; and polyether polyols obtained by addition polymerization of ethylene oxide, propylene oxide, tetramethylene oxide, or the like, with the above-mentioned low molecular weight polyols.

[0044] Specific examples of polyester polyols include polyester polyols obtained by polycondensing the above-mentioned low molecular weight polyols with polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, and maleic acid.

[0045] Specific examples of polycarbonate polyols include 1,6-hexanediol polycarbonate diol, 3-methyl-1,5-pentanediol polycarbonate diol, 1,10-decanediol polycarbonate diol, polypropylene carbonate diol, polytetramethylene carbonate diol, polyhexamethylene carbonate diol, polycyclohexanedimethanol carbonate diol, and polycyclohexanedimethanol carbonate diol. The above polyols may be used alone or in combination of two or more.

[0046] The water-dispersible urethane resin may be a copolymer of a urethane resin and another resin. For example, a urethane-modified acrylic resin in which a urethane side chain is introduced into an acrylic main chain may be mentioned. The water-dispersible urethane resin may also be a composite resin of a urethane resin and another resin. For example, urethane acrylic resin particles having a core-shell structure may be mentioned. From the viewpoint of ink image fixation and coating film strength, the water-dispersible urethane resin is preferably a urethane resin homopolymer. Furthermore, the water-dispersible urethane resin preferably exists in the ink as resin particles composed of a urethane resin homopolymer.

[0047] The water-dispersible urethane resin preferably exists in the ink as urethane resin particles. From the viewpoint of inkjet ejection properties, the average particle diameter of the urethane resin particles is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. For example, the average particle diameter of the urethane resin particles may be in the range of 10 nm to 300 nm. Furthermore, it is preferable that the average particle diameter of the urethane resin particles in the urethane resin emulsion added to the ink satisfies these ranges. Here, the average particle size of the resin is a volume-based average particle size, and is a value measured by dynamic light scattering.

[0048] Commercially available resin emulsions of polyether-type aliphatic urethane resins include, for example, "NeoRezR-650," "NeoRezR-966," and "NeoRezR-967" manufactured by DSM Coating Resins, "Superflex 130" and "Superflex E-4800" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "DAOTAN TW6491 / 33WA" manufactured by Daicel-Allnex Corporation, and "ADEKA BONTITAR HUX-350" and "ADEKA BONTITAR HUX-550" manufactured by ADEKA Corporation (all trade names).

[0049] Commercially available resin emulsions of polyester-type aliphatic urethane resins include, for example, "DAOTAN TW6490 / 35WA," "DAOTAN TW6492 / 35WA," and "DAOTAN TW7225 / 40WA" manufactured by Daicel-Allnex Corporation, "NeoRezR-972" and "NeoRezR-9637" manufactured by DSM Coating Resins, and "Superflex 210" and "Superflex 500M" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (all trade names).

[0050] Commercially available resin emulsions of polycarbonate-type aliphatic urethane resins include, for example, "NeoRezR-986" and "NeoRezR-4000" manufactured by DSM Coating Resins, "Superflex 460" and "Superflex 420" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and "DAOTAN TW7000 / 40WA" and "DAOTAN TW6450 / 30WA" manufactured by Daicel-Allnex Corporation (all trade names).

[0051] The water-dispersible urethane resins may be used alone or in combination of two or more. From the viewpoints of ink image fixability and coating film strength, the water-dispersible urethane resin is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more of the total amount of ink. From the viewpoint of further improving fixability and coating film strength, the water-dispersible urethane resin is preferably 15% by mass or more, more preferably 20% by mass or more of the total amount of ink. From the viewpoints of preventing ink image stickiness and improving ejection performance from inkjet ink, the amount of water-dispersible urethane resin is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, of the total amount of ink. That is, if the amount of water-dispersible urethane resin applied to the substrate is large, the resin content of the ink image increases, which may cause stickiness. Furthermore, if the content of water-dispersible urethane resin in the ink is large, the ink may become highly viscous, which may result in poor ejection performance from inkjet nozzles. For example, the content of the water-dispersible urethane resin is preferably 1 to 50 mass %, more preferably 10 to 30 mass %, and even more preferably 20 to 24 mass %, relative to the total amount of the ink.

[0052] From the viewpoint of improving the fixability and coating strength of the ink image, and from the viewpoint of preventing the ink image from becoming sticky and improving the ejection properties, the amount of the water-dispersible urethane resin is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1.5 to 3 parts by mass, per 1 part by mass of the white pigment.

[0053] The white ink may contain other resins in addition to the water-dispersible urethane resin. Examples of such resins include fixing resins. While the water-dispersible urethane resin can function as a binder resin, other resins may also be used as long as the effects of the present invention are not impaired.

[0054] The other resin may be either a water-soluble resin or a water-dispersible resin, but a water-dispersible resin is preferred from the viewpoint of obtaining ejection properties and storage stability suitable for an inkjet ink. The water-dispersible resin is preferably blended into the white ink in the form of a water-in-oil emulsion and is preferably dispersible in the white ink in the form of resin particles. Examples of water-dispersible resins that can be used in combination with the water-dispersible urethane resin include conjugated diene resins such as styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, and vinyl chloride-vinyl acetate copolymer; acrylic resins such as polymers of acrylic acid esters and methacrylic acid esters or copolymers of these with styrene; vinyl resins such as ethylene-vinyl acetate copolymer, or functional group-modified resins of these resins with monomers containing functional groups such as carboxyl groups; melamine resin, urea resin, polyester resin, polyolefin resin, silicone resin, polyvinyl butyral resin, and alkyd resin. Resin emulsions of these resins alone or hybrid resin emulsions may be used. Other resins may be used alone or in combination of two or more.

[0055] The amount of the other resins is preferably 1 to 20% by mass of the total amount of the ink. When the ink contains other resins, the total amount of the water-dispersible urethane resins relative to the total amount of all resins contained in the ink is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The total content of the water-dispersible resin and the water-soluble resin relative to the total amount of the white ink is preferably 1 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 20 to 30% by mass, where the total content of the water-dispersible resin and the water-soluble resin includes the water-dispersible urethane resin and any other water-dispersible resins and water-soluble resins other than the water-dispersible urethane resin that are optionally contained.

[0056] The white ink may contain a white pigment. By containing the white pigment, the white ink can be used to form an image that exhibits white color. The white pigment may be either an inorganic pigment or an organic pigment, or a combination of these may be used. Since the white ink of one embodiment is difficult to dry, a decrease in dispersion stability can be prevented even when an inorganic pigment with a high specific gravity is used. Examples of white pigments include white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. Furthermore, white organic pigments such as hollow resin microparticles and solid resin microparticles can also be used. Among these, titanium oxide pigments are preferred from the viewpoint of opacity. The average particle diameter of the white pigment is preferably 50 nm or more, 100 nm or more, or 200 nm or more from the viewpoint of opacity, and preferably 500 nm or less, 400 nm or less, or 300 nm or less from the viewpoint of ejection stability. The average particle diameter of titanium oxide pigments is more preferably 200 to 300 nm from the viewpoints of opacity and ejection stability. When using titanium oxide pigments, it is preferable to use those that have been surface-treated with alumina, silica, or the like to suppress photocatalytic activity. The amount of surface treatment is preferably 5 to 20 mass% of the pigment.

[0057] A self-dispersing pigment may be used as the white pigment. A self-dispersing pigment is a pigment in which a hydrophilic functional group has been introduced onto its surface by chemical or physical treatment. The hydrophilic functional group introduced into the self-dispersing pigment is preferably ionic, and by charging the pigment surface anionically or cationic, the pigment particles can be stably dispersed in water due to electrostatic repulsion. Preferred anionic functional groups include carboxyl groups, sulfo groups, and phosphate groups. Preferred cationic functional groups include quaternary ammonium groups and quaternary phosphonium groups. These hydrophilic functional groups may be bonded directly to the pigment surface or via other atomic groups. Examples of such other atomic groups include, but are not limited to, alkylene groups, phenylene groups, and naphthylene groups. Examples of methods for treating the pigment surface include diazotization, sulfonation, hypochlorous acid treatment, humic acid treatment, and vacuum plasma treatment.

[0058] The white pigment may be a pigment dispersion in which the pigment is dispersed in advance with a pigment dispersant, or a microencapsulated pigment in which the pigment is coated with a resin.

[0059] The white pigment may be used alone or in combination of two or more kinds. From the viewpoint of hiding power and the like, the content of the white pigment is preferably 5 to 30% by mass, more preferably 8 to 20% by mass, and even more preferably 10 to 12% by mass, based on the total amount of the white ink.

[0060] In order to stably disperse the white pigment in the white ink, a pigment dispersant such as a polymer dispersant or a surfactant-type dispersant can be used. Examples of commercially available polymer dispersants include the TEGO Disperse series manufactured by EVONIK, such as "TEGO Disperse 740W," "TEGO Disperse 750W," "TEGO Disperse 755W," "TEGO Disperse 757W," and "TEGO Disperse 760W," and the Solsperse series manufactured by Lubrizol Japan, such as "Solsperse 20000," "Solsperse 27000," "Solsperse 41000," "Solsperse 41090," "Solsperse 43000," "Solsperse 44000," and "Solsperse 46000." Examples include the JONCRYL series manufactured by BASF Japan Ltd., such as "JONCRYL 57," "JONCRYL 60," "JONCRYL 62," "JONCRYL 63," "JONCRYL 71," and "JONCRYL 501," and the like; manufactured by BYK Japan Co., Ltd., "DISPERBYK-102," "DISPERBYK-185," "DISPERBYK-190," "DISPERBYK-193," and "DISPERBYK-199," and the like; and manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "Polyvinylpyrrolidone K-30" and "Polyvinylpyrrolidone K-90" (all trade names). Examples of surfactant-type dispersants include anionic surfactants such as the Demol series manufactured by Kao Corporation, including "Demol P," "Demol EP," "Demol N," "Demol RN," "Demol NL," "Demol RNL," and "Demol T-45," and nonionic surfactants such as the Emulgen series manufactured by Kao Corporation, including "Emulgen A-60," "Emulgen A-90," "Emulgen A-500," "Emulgen B-40," "Emulgen L-40," and "Emulgen 420" (all trade names).

[0061] The pigment dispersants may be used alone or in combination of two or more. When a pigment dispersant is used, its content in the ink varies depending on the type and is not particularly limited, but in general, the mass ratio of the active ingredient to the white pigment is preferably 0.005 to 0.5.

[0062] The white ink preferably contains water, and the main solvent may be water. The water is not particularly limited, but it is preferable that it contains as few ionic components as possible. In particular, from the viewpoint of the storage stability of the white ink, it is preferable that the content of polyvalent metal ions such as calcium is low. As the water, for example, ion-exchanged water, distilled water, ultrapure water, etc. may be used.

[0063] From the viewpoint of adjusting the ink viscosity, the water content is preferably 30 to 90% by mass, more preferably 40 to 85% by mass, and even more preferably 50 to 80% by mass, of the total amount of the white ink.

[0064] The white ink may contain a water-soluble organic solvent. As the water-soluble organic solvent, an organic compound that is liquid at room temperature (25°C) and dissolves in water can be used, and it is preferable to use a water-soluble organic solvent that is uniformly miscible with the same volume of water at 20°C under 1 atmosphere. For example, lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycol; Glycerols such as glycerin, diglycerin, triglycerin, and polyglycerin; acetins such as monoacetin and diacetin; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether; Examples of usable solvents include β-thiodiglycol and sulfolane. The boiling point of the water-soluble organic solvent is preferably 100°C or higher, and more preferably 150°C or higher.

[0065] Among these, glycols, glycerins, or combinations thereof are preferred from the viewpoints of adjusting ink viscosity and moisturizing properties. Preferred glycols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol. Preferred glycerins are glycerin.

[0066] These water-soluble organic solvents may be used alone, or two or more may be used in combination as long as they form a single phase with water. When two or more water-soluble organic solvents are used, the total content of the water-soluble organic solvents is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and even more preferably 15 to 30% by mass, of the total amount of the white ink.

[0067] The white ink may further contain a surfactant. The surfactant may be an anionic surfactant, a cationic surfactant, an amphoteric surfactant, or a nonionic surfactant, with nonionic surfactants being more preferred. Furthermore, either a low-molecular-weight surfactant or a high-molecular-weight surfactant may be used.

[0068] The HLB value of the surfactant is preferably 5-20, and more preferably 10-18.

[0069] Examples of nonionic surfactants include ester surfactants such as glycerin fatty acid esters and fatty acid sorbitan esters; ether surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers and polyoxypropylene alkyl ethers; ether ester surfactants such as polyoxyethylene sorbitan fatty acid esters; acetylene surfactants; silicone surfactants; fluorine surfactants; etc. Among these, acetylene surfactants such as acetylene glycol surfactants are preferably used.

[0070] Examples of the acetylene surfactant include an acetylene glycol surfactant, an acetylene alcohol surfactant, and a surfactant having an acetylene group. The acetylene glycol surfactant is a glycol having an acetylene group, preferably a glycol having a symmetrical structure with the acetylene group located in the center, and may have a structure in which ethylene oxide is added to acetylene glycol. Commercially available acetylene surfactants include, for example, the Surfynol series manufactured by Evonik Industries, such as "Surfynol 104E," "Surfynol 104H," "Surfynol 420," "Surfynol 440," "Surfynol 465," and "Surfynol 485," and the Olfin series manufactured by Nissin Chemical Industry Co., Ltd., such as "Olfin E1004," "Olfin E1010," and "Olfin E1020" (all trade names).

[0071] Examples of silicone surfactants include polyether-modified silicone surfactants, alkyl-aralkyl-co-modified silicone surfactants, and acrylic silicone surfactants. Examples of commercially available silicone surfactants include "Silface SAG002" and "Silface 503A" manufactured by Nissin Chemical Industry Co., Ltd. (both are trade names).

[0072] Other nonionic surfactants include polyoxyethylene alkyl ether surfactants such as those in the Emulgen series manufactured by Kao Corporation, including "Emulgen 102KG," "Emulgen 103," "Emulgen 104P," "Emulgen 105," "Emulgen 106," "Emulgen 108," "Emulgen 120," "Emulgen 147," "Emulgen 150," "Emulgen 220," "Emulgen 350," "Emulgen 404," "Emulgen 420," "Emulgen 705," "Emulgen 707," "Emulgen 709," "Emulgen 1108," "Emulgen 4085," and "Emulgen 2025G" (all trade names).

[0073] Examples of anionic surfactants include the Emeral series, manufactured by Kao Corporation, such as "Emeral 0," "Emeral 10," "Emeral 2F," "Emeral 40," and "Emeral 20C," the Neopelex series, such as "Neopelex GS," "Neopelex G-15," "Neopelex G-25," and "Neopelex G-65," the Pelex series, such as "Pelex OT-P," "Pelex TR," "Pelex CS," "Pelex TA," "Pelex SS-L," and "Pelex SS-H," and the Demol series, such as "Demol N," "Demol NL," "Demol RN," and "Demol MS" (all of which are trade names).

[0074] Examples of cationic surfactants include the Acetamine series (manufactured by Kao Corporation) such as "Acetamine 24" and "Acetamine 86," the Cortamine series (manufactured by Kao Corporation) such as "Cortamine 24P," "Cortamine 86P," "Cortamine 60W," and "Cortamine 86W," and the Sanisol series (manufactured by Kao Corporation) such as "Sanisol C" and "Sanisol B-50" (all trade names).

[0075] Examples of amphoteric surfactants include the Amphitol series manufactured by Kao Corporation, such as Amphitol 20BS, Amphitol 24B, Amphitol 86B, Amphitol 20YB, and Amphitol 20N (all trade names).

[0076] The surfactant may be used alone or in combination of two or more. The content of the surfactant is preferably 0.1 to 5% by mass, and more preferably 0.2 to 2% by mass, based on the total amount of the white ink.

[0077] The white ink may further contain other components such as a pH adjuster, a preservative, a rust inhibitor, and an antifoaming agent.

[0078] The method for producing the white ink is not particularly limited, and the ink can be produced by any known method. For example, all of the components are added to a stirrer such as a Three-One Motor or the like all at once or in portions, and dispersed, and if desired, the mixture is passed through a filter such as a membrane filter to obtain an ink.

[0079] From the viewpoint of storage stability of the ink, the pH of the white ink is preferably 7.0 to 10.0, and more preferably 7.5 to 9.0. The viscosity of the white ink can be adjusted as appropriate, but from the standpoint of jetting properties, for example, the viscosity at 23° C. is preferably 1 to 30 mPa·s.

[0080] The water-based white inkjet ink according to one embodiment can be applied to both porous and non-porous substrates. An impermeable substrate is a substrate into which liquid does not penetrate, specifically a substrate in which most of the liquid in the treatment liquid or ink remains on the surface of the substrate. Examples of impermeable substrates include metal substrates such as metal plates made of aluminum, iron, copper, titanium, tin, chromium, cadmium, alloys (e.g., stainless steel, steel, etc.), glass substrates such as plate glass made of borosilicate glass, quartz glass, soda-lime glass, etc., resin substrates such as resin sheets made of PET film, PP film, OHT sheet, polyester sheet, polypropylene sheet, etc., acrylic plate, polyvinyl chloride plate, etc., and ceramic substrates such as molded bodies made of alumina, zirconia, steatite, silicon nitride, etc. These substrates may have a plating layer, metal oxide layer, resin layer, etc. formed thereon, or may have been surface-treated using corona treatment, etc.

[0081] Examples of permeable substrates include printing paper such as plain paper, coated paper, and specialty paper; fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics; porous building materials for humidity control, sound absorption, and heat insulation; wood, concrete, and porous materials. Plain paper is ordinary paper on which no ink-receiving layer or film layer is formed. Examples of plain paper include fine paper, medium-quality paper, PPC paper, wood chipping paper, and recycled paper. Preferred examples of coated paper include inkjet coated paper such as matte paper, glossy paper, and semi-glossy paper, as well as so-called coated printing paper. Coated printing paper is printing paper that has traditionally been used in letterpress printing, offset printing, gravure printing, and the like, and is formed by providing a coating layer on the surface of fine or medium-quality paper using a paint containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch. Coated printing paper is classified into lightly coated paper, high-quality lightweight coated paper, medium-quality lightweight coated paper, high-quality coated paper, medium-quality coated paper, art paper, cast-coated paper, etc. depending on the amount of paint applied and the coating method.

[0082] Examples of fibers that make up the fabric include at least one type selected from various fibers such as inorganic fibers such as metal fibers, glass fibers, rock fibers, and mineral fibers; regenerated fibers such as cellulose-based and protein-based fibers; semi-synthetic fibers such as cellulose-based fibers; synthetic fibers such as polyamide, polyester, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl alcohol, polyurethane, polyethylene, polypropylene, polystyrene, and polyethylene fluoride; and natural fibers such as cotton, hemp, silk, and wool. The aqueous white inkjet ink contains a water-dispersible urethane resin, making it suitable for printing on fabrics and suitable for use as an aqueous white inkjet ink for textile printing. The resulting printed textile exhibits excellent ink image fixation and coating strength, as well as improved abrasion fastness and washing fastness.

[0083] The aqueous white inkjet ink can be applied to a substrate by an inkjet method to form a white ink image. The aqueous white inkjet ink may be applied to the substrate as an underlayer. When the aqueous white inkjet ink is used as an underlayer, an ink image can be formed by applying a non-white color ink to the substrate on which the underlayer has been formed. In addition, the substrate may be subjected to a pretreatment before the aqueous white inkjet ink is applied to the substrate. The color ink and the pretreatment liquid will be described below.

[0084] <Color ink> The color ink is preferably an aqueous color ink containing a non-white pigment and water, and more preferably an aqueous inkjet ink. Examples of the color ink include magenta ink, cyan ink, yellow ink, and black ink.

[0085] The color ink may contain, as a colorant, a pigment, a dye, or a combination thereof, and preferably contains a pigment.

[0086] Examples of non-white pigments that can be used include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments, as well as inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. These pigments may be used alone or in combination.

[0087] From the viewpoints of ejection stability and storage stability, the average particle size of the pigment particles in the ink is preferably 300 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less, as the volume-based average value in the particle size distribution measured by dynamic light scattering.

[0088] The non-white pigment may be a self-dispersing pigment, the details of which are as described above for the white pigment. Preferred examples of self-dispersing pigments that can be used include the CAB-O-JET series manufactured by Cabot Corporation, such as "CAB-O-JET200," "CAB-O-JET300," "CAB-O-JET250C," "CAB-O-JET260M," "CAB-O-JET270," and "CAB-O-JET450C," and products manufactured by Orient Chemical Industries Co., Ltd., such as "BONJET BLACK CW-1," "BONJET BLACK CW-2," "BONJET BLACK CW-3," and "BONJET BLACK CW-4" (all trade names). As the pigment, a microencapsulated pigment in which the pigment is coated with a resin may be used.

[0089] A pigment dispersion in which the pigment is previously dispersed with a pigment dispersant may be used. Commercially available pigment dispersions in which the pigment is dispersed with a pigment dispersant include, for example, the HOSTAJET series manufactured by Clariant and the FUJI SP series manufactured by Fuji Pigment Co., Ltd.

[0090] As the dye, water-soluble dyes and water-soluble dyes made water-soluble by reduction or the like can be preferably used from among basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes, mordant dyes, reactive dyes, vat dyes, sulfur dyes, etc. Also preferably used are disperse dyes such as azo-based, anthraquinone-based, azomethine-based, and nitro-based dyes. These may be used alone or in combination.

[0091] The coloring materials may be used alone or in combination of two or more. From the viewpoint of print density and ink viscosity, the content of the color material is preferably 0.1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 2 to 7% by mass, based on the total amount of color ink.

[0092] When a pigment is used as a coloring material in a color ink, a pigment dispersant, such as a polymer dispersant or a surfactant-type dispersant, can be used to stably disperse the pigment in the color ink. The pigment dispersant can be selected from those described above for the white ink, for example. When a pigment dispersant is used, the content in the color ink varies depending on the type and is not particularly limited, but in general, the mass ratio of the active ingredient to the pigment is preferably 0.005 to 0.5.

[0093] The color ink preferably contains water. The color ink may contain a water-soluble organic solvent in addition to or instead of water. Details of water and the water-soluble organic solvent are as described above for the white ink. The water-soluble organic solvent may be selected from those described above for the white ink, for example. From the viewpoint of adjusting the ink viscosity, the water content is preferably 20% by mass to 80% by mass, and more preferably 30% by mass to 70% by mass, based on the total amount of the color ink. The amount of the water-soluble organic solvent is preferably 5 to 50% by mass, and more preferably 10 to 30% by mass, based on the total amount of the color ink.

[0094] The color ink may further contain a surfactant. The surfactant may be selected from those described above for the white ink. Among them, nonionic surfactants are preferred, and acetylene-based surfactants such as acetylene glycol-based surfactants are more preferred. The amount of the surfactant in terms of active ingredients is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, based on the total amount of the color ink.

[0095] The color ink may further contain a resin such as a water-dispersible resin or a water-soluble resin. For example, by including a fixing resin in the color ink, the fixation of the ink image to the substrate and the coating strength of the ink image can be further improved. From the viewpoint of obtaining ejection properties and storage stability suitable for inkjet inks, the color ink preferably contains a water-dispersible resin. The water-dispersible resin is preferably blended into the color ink in the form of a water-in-oil emulsion and is preferably dispersible in the color ink in the form of resin particles. The water-dispersible resin can be selected from those described above for the white ink, and may be a water-dispersible urethane resin, other water-dispersible resins, or a combination thereof. The content of the water-dispersible resin is preferably 1 to 30% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, based on the total amount of the color ink.

[0096] The color ink may further contain a crosslinking agent. When the color ink contains a crosslinking agent, the coating strength of the ink image can be further increased. For example, when the color ink is used as an aqueous inkjet ink for textile printing, the coating strength of the printed material is increased, thereby further suppressing cracking of the ink image even after washing. Examples of crosslinking agents include carbodiimide compounds, isocyanate compounds, and oxazoline compounds. The content of the crosslinking agent is preferably 0.1 to 5% by mass, and more preferably 0.2 to 2% by mass, based on the total amount of the color ink.

[0097] The color ink may further contain other components such as a pH adjuster, a preservative, a rust inhibitor, and an antifoaming agent. The method for producing the color ink is not particularly limited, and the ink can be produced by any known method. For example, all the components are added to a stirrer such as a Three-One Motor all at once or in portions, and dispersed, and if desired, the mixture is passed through a filter such as a membrane filter to obtain an ink. The pH of the color ink is preferably 7.0 to 10.0, more preferably 7.5 to 9.0, from the viewpoint of storage stability of the ink. The viscosity of the color ink can be adjusted as appropriate, but from the viewpoint of ejection properties, for example, the viscosity at 23° C. is preferably 1 to 30 mPa·s.

[0098] <Pretreatment liquid> In one embodiment, the substrate to which the white ink is applied may be pretreated or untreated. Using a pretreated substrate can further improve the image quality of the ink image and the fixability of the ink image to the substrate. The pretreated substrate can be obtained by applying a pretreatment liquid to the substrate.

[0099] As the pretreatment liquid, a pretreatment liquid containing a flocculant and water can be preferably used. The flocculant may be a component that has the effect of flocculating the coloring material in the ink on the substrate. When the ink is further applied to the substrate to which the pretreatment liquid has been applied, the coloring material in the ink aggregates on the substrate, thereby increasing the image density and preventing image bleeding. Specific examples of the flocculant include metal salts, cationic polymers, organic acids, and the like, or combinations thereof. The total amount of the flocculant, in terms of the amount of active ingredients, is preferably 1 to 30 mass %, more preferably 3 to 30 mass %, and even more preferably 5 to 15 mass %, relative to the total amount of the pretreatment liquid.

[0100] As the metal salt, a polyvalent metal salt can be preferably used. Polyvalent metal salts are composed of divalent or higher polyvalent metal ions and anions. Examples of divalent or higher polyvalent metal ions include Ca. 2+ , Mg 2+ , Cu 2+ , Ni 2+ , Zn 2+ , Ba 2+ Examples of anions include Cl - , NO3 - , CH3COO - , I - , Br - , ClO3 - Specific examples of polyvalent metal salts include calcium chloride, calcium nitrate, magnesium nitrate, copper nitrate, calcium acetate, and magnesium acetate.

[0101] As the cationic polymer, a cationic water-soluble resin can be preferably used. Examples of cationic water-soluble resins include polyethyleneimine (PEI), polyvinylamine, polyallylamine and its salts, polyvinylpyridine, cationic acrylamide copolymers, etc. More specifically, for example, polydiallyldimethylammonium chloride can be used.

[0102] Examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, tricarballylic acid, glycolic acid, thioglycolic acid, lactic acid, malic acid, tartaric acid, citric acid, isocitric acid, gluconic acid, pyruvic acid, oxalic acid, diglycolic acid, benzoic acid, phthalic acid, mandelic acid, and salicylic acid.

[0103] The pretreatment liquid preferably contains water. The pretreatment liquid may contain a water-soluble organic solvent in addition to or instead of water. Details of the water and the water-soluble organic solvent are as described above for the white ink. The water-soluble organic solvent may be selected from those described above for the white ink. The amount of water is preferably 30 to 90 mass %, more preferably 40 to 85 mass %, and even more preferably 50 to 80 mass %, based on the total amount of the pretreatment liquid. The amount of the water-soluble organic solvent is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass, based on the total amount of the pretreatment liquid.

[0104] The pretreatment liquid may further contain a surfactant. The surfactant may be selected from those described above for the white ink. Among them, nonionic surfactants are preferred, and acetylene-based surfactants such as acetylene glycol-based surfactants are more preferred. The amount of the surfactant, in terms of the active ingredient, is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, based on the total amount of the pretreatment liquid.

[0105] The pretreatment liquid may further contain other components, such as a pH adjuster, a preservative, a rust inhibitor, and an antifoaming agent.

[0106] The method for producing the pretreatment liquid is not particularly limited, and the pretreatment liquid can be produced by any known method, for example, by adding all the components to a stirrer such as a Three-One Motor all at once or in portions, dispersing the components, and optionally passing the mixture through a filter such as a membrane filter.

[0107] <Manufacturing method for printed matter> A method for producing a printed matter using a water-based white inkjet ink according to an embodiment will now be described. In one example, a printed material can be produced by applying the aqueous white inkjet ink to a substrate by an inkjet method. In another example, a printed material can be produced by applying the aqueous white inkjet ink to a substrate by an inkjet method, and then applying a color ink to the substrate to which the aqueous white inkjet ink has been applied. A pretreatment liquid may be applied to the substrate before the white ink is applied to the substrate. A preferred example of a method for producing a printed item can include applying a pretreatment liquid to a fabric, applying a white ink to the substrate to which the pretreatment liquid has been applied by an inkjet method, and applying a color ink to the substrate to which the white ink has been applied. In this example, it is preferred that the pretreatment liquid, the white ink, and the color ink are each applied to the substrate by an inkjet method.

[0108] The inkjet method is a printing method that allows for easy and flexible image formation on demand without contacting a substrate. There are no particular limitations on the inkjet method, and it may be any of a piezoelectric method, an electrostatic method, a thermal method, etc. When an inkjet printing device is used, it is preferable that droplets of the pretreatment liquid or ink are ejected from an inkjet head based on a digital signal and the ejected droplets are attached to the fabric. The inkjet printing device may be a serial head type or a line head type.

[0109] The step of applying the pretreatment liquid to the substrate will be described below. The area to which the pretreatment liquid is applied may be an area having the same shape as the white ink image, a wider area including the shape of the white ink image, or the entire surface of the substrate. It is preferable that the area to which the pretreatment liquid is applied, the area to which the white ink is applied, and the area to which the color inks are applied at least partially overlap each other. As a method for applying the pretreatment liquid to the substrate, for example, the pretreatment liquid may be applied uniformly to the surface of the substrate using a brush, a roller, a bar coater, an air knife coater, a spray, or the like, or the pretreatment liquid may be printed in the image region by a printing method such as inkjet printing, gravure printing, or flexographic printing. The amount of pretreatment liquid applied to the substrate is 5 to 200 g / m 2 is preferable, and 10 to 100 g / m 2 is preferable, and 15 to 80 g / m 2 is more preferred.

[0110] Next, a process of applying white ink by an inkjet method to the substrate to which the pretreatment liquid has been applied will be described. The area to which the white ink is applied may be an area having the same shape as the image formed by the color inks, a wider area including the shape of the image formed by the color inks, or the entire surface of the base material. It is preferable that the area to which the white ink is applied at least partially overlaps the area to which the pretreatment liquid is applied. The amount of white ink applied to the substrate is not particularly limited, but is, for example, 80 to 400 g / m 2 is preferable, and 120 to 250 g / m 2 is more preferred.

[0111] Next, the process of applying color inks to the substrate to which the white ink has been applied will be described. Preferably, the area where the color ink is applied at least partially overlaps the area where the white ink is applied. The method for applying the color ink to the substrate may be, for example, any of inkjet printing, offset printing, screen printing, gravure printing, and flexographic printing. The amount of color ink applied to the substrate is not particularly limited, but may be, for example, 1 to 100 g / m 2 is preferable, and 5 to 50 g / m 2 is more preferred. It should be noted that one type of color ink may be applied, or two or more types of color ink may be applied.

[0112] After applying the pretreatment liquid to the substrate, the white ink may be applied to the substrate by a wet-on-wet method, or the white ink may be applied to the substrate after drying the substrate. In the wet-on-wet method, the white ink is preferably applied in a state in which moisture is not completely removed from the substrate to which the pretreatment liquid has been applied. Preferably, the white ink is applied in a state in which the substrate to which the pretreatment liquid has been applied remains wet. For example, it is preferable to apply the white ink to the substrate without performing a drying step such as heat drying after applying the pretreatment liquid to the substrate. Similarly, after applying the white ink to the substrate, color inks may be applied to the substrate by a wet-on-wet method, or the color inks may be applied to the substrate after drying the substrate.

[0113] After the application of the white ink or color ink, a step of heat treating the substrate may be further carried out, which allows the ink image to be more firmly fixed. The heat treatment temperature can be appropriately selected depending on the material of the substrate, etc. The heat treatment temperature is, for example, preferably 100° C. or higher, more preferably 150° C. or higher. From the viewpoint of reducing damage to the substrate, the heat treatment temperature is preferably 200° C. or lower. The heating device is not particularly limited, but for example, a heat press, a roll heater, a hot air device, an infrared lamp heater, or the like can be used. The heat treatment time may be appropriately set depending on the heating method, etc., and is, for example, preferably 1 second to 10 minutes, and may be 5 seconds to 5 minutes.

[0114] The step of applying a pretreatment liquid, the step of applying a white ink, and the step of applying a color ink may be performed by separate printing apparatuses, or may be performed by using a single printing apparatus. For example, two printing apparatuses may be used, with the step of applying a pretreatment liquid being performed by one of the printing apparatuses and the step of applying a white ink and the step of applying a color ink being performed by the other one.

[0115] An overcoat layer may be formed on the substrate after the white ink has been applied, or on the substrate after the white ink and the color inks have been applied. The overcoat layer can be formed by applying a post-treatment liquid to the substrate after the inks have been applied. As the post-treatment liquid, for example, a post-treatment liquid containing a resin capable of forming a coating film and an aqueous medium or an oil-based medium can be used. After the white ink or the color inks have been applied, a step of heating the substrate may be provided, and then the post-treatment liquid may be applied. After the color inks have been applied, the post-treatment liquid may be applied by a wet-on-wet method. Furthermore, a step of heating the substrate may be provided after the post-treatment liquid has been applied.

[0116] A printed textile can be produced by using a fabric as the substrate in the above-described method for producing a printed material. Specifically, one example of a method for producing a printed textile can include applying an aqueous white inkjet ink to a fabric by inkjet printing, and applying color inks to the fabric substrate to which the aqueous white inkjet ink has been applied to form an image. The color inks can be single colors such as magenta ink, cyan ink, yellow ink, and black ink, or multicolors that combine these colors. Furthermore, the method for producing a printed textile can include applying a pretreatment liquid to the fabric before applying the aqueous white inkjet ink to the fabric by inkjet printing. The color inks and the pretreatment liquid can be applied independently to the substrate by inkjet printing, but they may also be applied by other methods. Details of the water-based white inkjet ink, color inks, and pretreatment liquid are as described above.

[0117] <Ink set> According to one embodiment, an ink set including an aqueous white inkjet ink and color inks can be provided. According to another embodiment, an ink set including a pretreatment liquid, an aqueous white inkjet ink, and color inks can be provided. These ink sets may further include a post-treatment liquid. When using fabric as the substrate, these ink sets can be provided as textile printing ink sets. The aqueous white inkjet ink contains a water-dispersible urethane resin, which can improve the fixation of ink images and the coating strength. Furthermore, since the content of the amine compound in the aqueous white inkjet ink is appropriately controlled, sedimentation and adhesion of the white pigment are suppressed, resulting in excellent open-standing stability. Details of the aqueous white inkjet ink, color inks, and pretreatment liquid are as described above. [Example]

[0118] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples. In the following description, "%" means "% by mass" unless otherwise specified.

[0119] "Preparation of white pigment dispersion" 400 g of titanium dioxide "R-21N" (manufactured by Sakai Chemical Industry Co., Ltd.) as a white pigment and 20 g (5 g of active ingredient) of "Demol EP" (manufactured by Kao Corporation) as a pigment dispersant were mixed with 580 g of ion-exchanged water, and the mixture was dispersed with 0.5 mm diameter zirconia beads using a bead mill ("DYNO-MILL KDL A-type" manufactured by Shinmaru Enterprises Co., Ltd.) at a filling rate of 80 volume % and a residence time of 5 minutes, to obtain a white pigment dispersion (pigment content 40 mass %).

[0120] "Preparation of white ink" Tables 1 to 3 show the ink formulations. The raw materials were mixed according to the formulations shown in the tables and stirred at 100 rpm for 20 minutes using a mix rotor to obtain white inks. The contents shown in the tables are the amounts of active ingredients such as solid content or resin content.

[0121] "Evaluation of ink fluidity after being left open" To evaluate the open storage performance, the fluidity of the ink after being left open was evaluated. 2 g of white ink was added to a 35.4 mm diameter petri dish. The dish was then left in a thermostatic chamber at 40°C for 1 hour. After leaving the dish, the fluidity of the ink in the dish was visually confirmed. The fluidity of the ink after being left open was evaluated according to the following criteria. A: There was almost no change in the fluidity of the ink after being left standing compared to before being left standing. B: The fluidity of the ink after being left standing is slightly inferior to that before being left standing. C: The ink solidified after being left standing.

[0122] The ingredients used are as follows: Urethane resin emulsion "DAOTAN TW6450 / 30WA" (product name): manufactured by Daicel Ornix Co., Ltd., resin content 30% by mass. Urethane resin emulsion "NeoRezR-967" (product name): manufactured by DSM, resin content 40% by mass. Acrylic resin emulsion "NeoCryl XK-12" (product name): manufactured by DSM, resin content 45% by mass. Surfactant "Olfine E1010" (product name): manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol-based surfactant, active ingredient content 100% by mass.

[0123] Details of the amine compounds used are as follows: 2-Amino-2-ethyl-1,3-propanediol: Primary amine, molecular weight is 119.16, number of hydroxy groups is 2, number of hydroxy groups relative to molecular weight is 0.017. Triethanolamine: Tertiary amine, molecular weight is 149.188, number of hydroxyl groups is 3, number of hydroxyl groups relative to molecular weight is 0.020. Diisopropanolamine: Secondary amine, molecular weight is 133.191, number of hydroxyl groups is 2, number of hydroxyl groups relative to molecular weight is 0.015. Diethylamine: Secondary amine, molecular weight 73.14, number of hydroxy groups 0. Tridodecylamine: Tertiary amine, molecular weight 522.00, number of hydroxy groups 0.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Table 3]

[0127] As shown in the table, the white ink of each example had excellent ink flowability, which indicates that the ink has excellent properties when left open when filled in an inkjet head.

[0128] No amine compound was used in Comparative Example 1, the content of the amine compound and the mass ratio of the amine compound to the water-dispersible resin were inappropriate in Comparative Examples 2 to 5, the molecular weight of the amine compound was inappropriate in Comparative Examples 6 and 7, and the type of water-dispersible resin was inappropriate in Comparative Example 8. In these Comparative Examples, the fluidity of the ink was reduced.

[0129] "Printing on fabric substrates" The white inks obtained in Examples 1 to 12 were printed onto a fabric substrate to produce printed textiles. The fabric substrate used was a black 100% cotton shirt "Printstar 085-cvt" (manufactured by TOM'S Co., Ltd.). A pretreatment liquid was prepared to pretreat the fabric substrate before printing the white ink onto it. Specifically, the raw materials were mixed according to the following recipe, and coarse particles were removed using a membrane filter with a pore size of 3 μm to prepare the pretreatment liquid. Flocculant: calcium chloride 20.0% by mass Water-soluble organic solvent: 1,4-butanediol 25.0% by mass Surfactant: "Olfine E1010" (trade name) 0.5% by mass Water: ion-exchanged water 54.5% by mass Total 100.0% by mass

[0130] First, two inkjet printers (Mastermind textile printer "MMP-8130") were prepared, and a pretreatment liquid was introduced into the first printer (hereinafter sometimes referred to as "printer 1"), and white ink was introduced into the second printer (hereinafter sometimes referred to as "printer 2"). Printed textiles were produced using the white inks of Examples 1 to 12 according to the following steps 1 to 3. Step 1: In step 1, the printer 1 into which the pretreatment liquid has been introduced is used to apply the treatment liquid onto the substrate in an amount of 50 g / m. 2 The treatment liquid was applied to the entire area of ​​100 mm x 200 mm so as to achieve the following. Step 2: In step 2, white ink was applied by a wet-on-wet method to the substrate to which the pretreatment liquid had been applied, using printer 2. In this step 2, the amount of white ink applied was 200 g / m 2 on the 100 mm x 200 mm area to which the pretreatment liquid had been applied. 2 A 100 mm x 200 mm white solid image was printed. Step 3: In step 3, the printed T-shirt was heat treated at 160° C. for 120 seconds using a Hotronix Fusion heat press (manufactured by Stahls Hotronix). Ink jet printing was possible without any problems using the white ink of each example, and the formation of white images on the resulting printed textile was also good.

Claims

1. The ink contains a white pigment, a water-dispersible urethane resin, an amine compound having a molecular weight of 110 to 150, and water, the amine compound having a molecular weight of 110 to 150 is contained in an amount of 0.2 to 1.3% by mass based on the total amount of the ink; The amine compound having a molecular weight of 110 to 150 includes a primary amine compound, the primary amine compound contains at least one amine compound selected from the group consisting of 2-amino-2-ethyl-1,3-propanediol and trishydroxymethylaminomethane in an amount of 0.2 to 0.4% by mass relative to the total amount of the ink; a mass ratio of the amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin satisfies (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the water-dispersible urethane resin) = 0.02 to 0.

08.

2. A composition comprising a white pigment, a water-dispersible urethane resin, an amine compound having a molecular weight of 110 to 150, and water, the amine compound having a molecular weight of 110 to 150 is contained in an amount of 1.1 to 1.3% by mass based on the total amount of the ink; The amine compound having a molecular weight of 110 to 150 includes a tertiary amine compound, the tertiary amine compound contains triethanolamine in an amount of 1.1 to 1.3% by mass relative to the total amount of the ink; a mass ratio of the amine compound having a molecular weight of 110 to 150 to the water-dispersible urethane resin satisfies (mass of the amine compound having a molecular weight of 110 to 150) / (mass of the water-dispersible urethane resin) = 0.02 to 0.

08.

3. applying the water-based white inkjet ink according to claim 1 or 2 to a fabric by an inkjet method; and a method for producing a printed textile, the method comprising: applying a color ink to the fabric to which the water-based white inkjet ink has been applied, thereby forming an image.

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