JP2017008171A - Aqueous ink composition for inkjet - Google Patents

Abstract

To provide an aqueous ink composition for inkjet which is excellent in scratch resistance and tape peelability and excellent in ejection stability from an inkjet nozzle. An aqueous inkjet ink composition according to the present invention is an inkjet aqueous ink composition comprising at least one pigment and a wax, wherein the pigment is made of a polymer containing pigment particles therein. And the mass ratio of the pigment particles to the polymer ((mass of the pigment particles) / (mass of the polymer)) is 1.2 to 2.3, and the wax has a melting point of 120 ° C. to 140 ° C. It is a wax. [Selection figure] None

Description

  The present invention relates to a water-based ink composition for inkjet, and more specifically, to an inkjet recording medium having low absorbability with respect to water-based ink, such as general printing paper, coated paper, art paper, cardboard, and paper container paper. The present invention relates to a water-based ink composition for inkjet which is excellent in abrasion and tape peelability and excellent in ejection stability from an inkjet nozzle.

  The ink jet recording method is a method in which ink containing a color material or a functional material is separated into droplets, and the droplets are ejected toward a recording medium such as paper in accordance with an image signal, and are printed. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized by offset printing. Accordingly, an aqueous ink composition for ink jet (hereinafter referred to as “aqueous ink composition”) that can be used for a recording medium such as print-coated paper used in the field of offset printing has been developed. However, the conventionally proposed water-based ink composition cannot be said to have excellent scratch resistance of an image printed on a recording medium, and has a problem that the degree of color transfer is larger than that of an offset printed material.

  In this regard, for example, Patent Document 1 below provides a water-based ink composition for ink jet recording that has good dispersibility and dischargeability, excellent scratch resistance, scratch resistance, and high color developability and gloss. As a subject, a polyolefin wax and a water-dispersible urethane resin are disclosed. According to Patent Document 1, it has good scratch resistance and scratch resistance, and can achieve excellent color development and high gloss (for example, paragraph [0010]).

  Patent Document 2 listed below is coated with a water-insoluble resin for the purpose of providing an ink composition that is excellent in ink stability and maintainability and in which occurrence of press blocking of the obtained image is suppressed. An ink composition containing a pigment, water-insoluble polymer particles having a glass transition temperature of 100 ° C. or higher, a solid wetting agent, a water-soluble organic solvent, wax particles having a melting point of 40 ° C. or higher and lower than 100 ° C., and water is disclosed (for example, , Claim 1 etc.).

WO2011 / 093486 JP 2011-162692 A

  However, even if high-definition printing is performed by the ink jet recording method using the water-based ink composition described in each of the above patent documents, there is a problem that the scratch resistance and tape peelability of the printed image are not sufficient.

  The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an aqueous ink composition for inkjet which is excellent in scratch resistance and tape peelability and excellent in ejection stability from an inkjet nozzle. It is in.

  The inventors of the present application have studied the water-based ink composition for inkjet in order to solve the above-mentioned problems, and as a result, found that the above-mentioned problems can be solved by adopting the following configuration, and completed the present invention. It was.

  That is, an aqueous inkjet ink composition according to the present invention is an inkjet aqueous ink composition comprising at least one pigment and a wax in order to solve the above-described problems, and the pigment is a pigment particle. The mass ratio of the pigment particles to the polymer ((mass of the pigment particles) / (mass of the polymer)) is 1.2 to 2.3, and the wax has a melting point of 120. It is characterized by being a polyethylene wax at a temperature of from ℃ to 140 ℃.

  The water-based ink composition for inkjet according to the present invention (hereinafter referred to as “water-based ink composition”) uses a pigment composed of a polymer containing pigment particles therein. Then, by setting the mass ratio of the pigment particles to the polymer in the pigment ((mass of the pigment particles) / (mass of the polymer)) to be 1.2 or more, the viscosity of the aqueous ink composition becomes too large. Can be prevented. As a result, when the aqueous ink composition of the present invention is printed by attaching the aqueous ink composition to a recording medium such as paper by an inkjet recording method, the aqueous ink composition is stabilized from the inkjet nozzle. It is possible to prevent the decrease in flightability. Further, by setting the mass ratio of the pigment particles and the polymer in the pigment to 2.3 or less, it is possible to improve the fixability such as scratch resistance and tape peelability of the printed coating film (image). Moreover, since the said structure also contains polyethylene-type wax, slip property can be provided to the surface of a printed image, and abrasion resistance and tape peelability can be improved further. Furthermore, since polyethylene wax having a melting point in the range of 120 ° C. to 140 ° C. is used, it is possible to suppress thermal deformation or melting of the polyethylene wax due to frictional heat due to rubbing of the surface of the printed coating film, A decrease in scratch resistance can be prevented.

  In the said structure, it is preferable that content of the said polyethylene-type wax exists in the range of 0.25 mass%-5 mass% with respect to the total mass of the aqueous ink composition for inkjets. By setting the content of the polyethylene wax to 0.25% by mass or more, the slip property of the printed coating film surface can be improved, and the scratch resistance can be further improved. On the other hand, the occurrence of beading can be reduced by setting the content of the polyethylene wax to 5% by mass or less.

The present invention has the following effects by the means described above.
That is, according to the aqueous inkjet ink composition of the present invention, the pigment is composed of a polymer containing pigment particles therein, and the mass ratio of the pigment particles to the polymer is in the range of 1.2 to 2.3. Use things. In addition, the aqueous inkjet ink composition of the present invention contains a polyethylene wax having a melting point in the range of 120 ° C to 140 ° C. Therefore, according to the present invention, an aqueous inkjet ink composition that enables stable ejection from an inkjet nozzle, suppresses a decrease in flightability, and has excellent fixing properties such as scratch resistance and tape peelability of a printed image. Things can be provided.

  The ink-jet aqueous ink composition of the present embodiment (hereinafter referred to as “water-based ink composition”) is an aqueous ink containing at least one pigment and a polyethylene wax and having a main solvent of water. Moreover, the water-based ink composition of the present embodiment is suitably used for inkjet recording. Since the pigment is used as the coloring material, the aqueous ink composition of the present embodiment is inherently superior in terms of color developability, weather resistance, water resistance, and the like as compared with the ink composition using the dye. .

  The pigment is an encapsulated pigment composed of pigment particles and a polymer containing the pigment particles therein.

  The pigment particles are not particularly limited, and any of organic pigment particles and inorganic pigment particles can be used. Examples of the organic pigment particles include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, thioindigo pigments, triphenylmethane lake pigments, and oxazine lake pigments. More specifically, examples of those having a yellow color tone include C.I. I. Pigment yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 16, 17, 65, 74, 83, 97, 138, 150, 151, 155. Examples of those having a red color tone include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 21, 22, 23, 31, 32, 37, 38, 41, 48, 49, 50, 51, 52, 57, 58, 60, 64, 83, 88, 89, 90, 112, 114, 122, 123, 166, 188, 202, C.I. I. Pigment Violet 19, 23. Examples of those having a blue color tone include C.I. I. Pigment blue 1, 2, 15, 15: 3, 15: 4, 16, 25, 75. Examples of those having a green color tone include C.I. I. Pigment Green 7, 36. Examples of those having a black color tone include C.I. I. And CI pigment blacks 1 and 7. Commercially available coloring pigments include, for example, Pigment Red 122, Pigment Violet 19 (Lansco Colors, Montvale, NJ, or BASF Color, Charlotte, NC, or Clariant Colors, Charlotte, NC, or Sun Chemical, Cincinn Pigment Blue 15: 1 (available from Fanwood Chemical, Fanwood, NJ), Pigment Blue 15: 3, Pigment 15: 4, Pigment Yellow 74, Pigment Yellow 97 (available from OH) BASF Color, Charlotte, NC, or Clariant Colors, Charlotte, NC, or Sun C and those sold by Chemical, Cincinnati, OH).

  Examples of the inorganic pigment particles include carbon black. The carbon black is not particularly limited, and examples thereof include acidic carbon black, neutral carbon black, and alkaline carbon black, and more specifically, channel black, gas black, lamp black, thermal black, acetylene black, and furnace black. It is done. Of these carbon blacks, channel black is preferred in the present embodiment. It should be noted that the quality of the carbon black may affect important properties of the dispersion such as average particle size, opacity, hue, and stability.

  Moreover, you may use a commercial item as said carbon black. Commercially available products include, for example, Elftex 8, Black Pearls (registered trademark, hereinafter the same) 490, Black Pearls 120, Monarch (registered trademark, the same applies hereinafter) 120, Monarch 700, Monarch 880, Monarch 1000, Monarch 1100. , Monarch 1300, Monarch 1400, Mogul (registered trademark) L, Regal (registered trademark, the same applies hereinafter) 99R, Regal 250R, Regal 300R, Regal 330R, Regal 400R, Regal 500R, Regal 660R (all manufactured by Cabot) Etc. Also, NIPex (registered trademark, hereinafter the same) 150IQ, NIPex 150, Printex (registered trademark, the same applies hereinafter) 55, Printex 80, Printex 90, Printex A, Printex G, Printex U, Printex V, Printex 140U, Printex 140U, Printex 140V, Purex (registered trademark) LS35, Colax (registered trademark) HP160, Thermal Black N990, NIPex (registered trademark) 160 IQ, NIPex (registered trademark) 90, Special black 4, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A Special black 100, Special black 250, Color black k FW1, Color black FW2, Color black FW2V, Color black FW18, Color black FW200, Color black S150, Color black S160, or Color black S170 (all manufactured by Deguss, etc.) In addition, Raven (registered trademark, the same applies hereinafter) 780, Raven 5000UII, Raven 1255, Raven 2500U, Raven 3600U, Raven 3500, Raven 7000, Raven 1220, Raven 1220, and Raven 1225 (all manufactured by Columbia), etc. Also, MA8, MA11, MA77, MA100, MA220, MA230, MA600, MCF88, # 10B, # 20B, # 30, # 33, # 40, # 44, # 45, # 45L, # 50, # 55, # 95 , # 260, # 900, 970 #, # 1000, # 2200B, # 2300, # 2350, # 2400B, # 2650, # 2700, # 4000B, or CF9 (all manufactured by Mitsubishi Chemical Corporation).

  The average particle diameter (volume average particle diameter) of the pigment particles is not particularly limited, and can be set as necessary. Usually, the thing within the range of 10 nm-1000 nm is preferable, and the thing within the range of 50 nm-200 nm is more preferable. The average particle diameter is a value measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.).

  Examples of the polymer include polyester, polyurethane, and vinyl polymer. From the viewpoint of the dispersion stability of the pigment, a vinyl polymer is preferable.

  The vinyl polymer is obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound), and (a) a salt-forming group-containing monomer (hereinafter sometimes referred to as “component (a)”); ) A macromer (hereinafter sometimes referred to as “component (b)”) and / or (c) a hydrophobic monomer (hereinafter sometimes referred to as “component (c)”) and a monomer mixture (hereinafter referred to as “monomer mixture”) A water-insoluble vinyl polymer obtained by copolymerization of In this example, the structural unit derived from the component (a) or the structural unit derived from the components (a) and (c) is a main chain, and the structural unit derived from the component (b) is a side chain. Water insoluble graft polymers are preferred.

  The (a) salt-forming group-containing monomer is used from the viewpoint of improving the dispersion stability of the resulting dispersion. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group. Examples of the salt-forming group-containing monomer include a cationic monomer and an anionic monomer.

  The cationic monomer is not particularly limited, and examples thereof include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers. Of these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferred.

  The anionic monomer is not particularly limited, and examples thereof include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer. Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. Examples of the unsaturated phosphoric acid monomer include vinyl phosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyl Examples include roxyethyl phosphate. Among these, from the viewpoints of dispersion stability and ejection stability, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable.

  The macromer (b) is used from the viewpoint of improving the dispersion stability of the pigment. (B) The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. In addition, the number average molecular weight of (b) macromer is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L of dodecyldimethylamine as a solvent.

  The (b) macromer is preferably a styrene macromer or an aromatic group-containing (meth) acrylate macromer having a polymerizable functional group at one end from the viewpoint of dispersion stability of the pigment. The (meth) acrylate macromer refers to an acrylate macromer and / or a methacrylic macromer, and (meth) is used in the same meaning in this specification.

  Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. More specifically, styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene and the like can be mentioned.

  Examples of the aromatic group-containing (meth) acrylate macromer include a homopolymer of an aromatic group-containing (meth) acrylate, or a copolymer of the aromatic group-containing (meth) acrylate and another monomer. The aromatic group-containing (meth) acrylate has a substituent containing a hetero atom; it has an arylalkyl group having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, and more preferably 7 to 12 carbon atoms. Those having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of the substituent containing a hetero atom include a halogen atom, an ester group, an ether group, and a hydroxy group. Moreover, as a hetero atom, a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom are mentioned, for example. Specific examples of the aromatic group-containing (meth) acrylate include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 2-methacryloyloxyethyl-2-hydroxypropyl. A phthalate etc. are mentioned, Among these, benzyl (meth) acrylate is especially preferable.

  The polymerizable functional group in the (b) macromer is preferably an acryloyloxy group or a methacryloyloxy group. Moreover, acrylonitrile etc. are mentioned as said other monomer copolymerized with aromatic group containing (meth) acrylate.

  The content of the styrenic monomer in the styrenic macromer is preferably 50% by mass or more, and more preferably 70% by mass or more from the viewpoint of increasing the affinity with the pigment particles. In addition, the content of the aromatic group-containing (meth) acrylate in the aromatic group-containing (meth) acrylate-based macromer is preferably 50% by mass or more, more preferably 70%, from the viewpoint of increasing the affinity with the pigment particles. It is at least mass%.

The (b) macromer may have a side chain composed of another structural unit such as an organopolysiloxane. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end represented by the following formula (1).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - (Si (CH 3) 2 O) t -Si (CH 3) 3 (1)
(In the formula, t represents a number of 8 to 40).

  Examples of commercially available styrenic macromers include trade names of Toa Gosei Co., Ltd., AS-6 (S), AN-6 (S), HS-6 (S), and the like.

  The (c) hydrophobic monomer is used from the viewpoint of improving the printing density, and examples thereof include alkyl (meth) acrylates and aromatic group-containing monomers.

  As said alkyl (meth) acrylate, what has a C1-C22, Preferably C6-C18 alkyl group is preferable, Specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (Iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) ) Acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, and the like. In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Represents.

  Examples of the aromatic group-containing monomer include a monomer having a substituent containing a hetero atom, and a monomer having an aromatic group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms. Can be mentioned. Examples of the monomer having a substituent containing a hetero atom include the styrene monomer (c-1) component, and styrene and 2-methylstyrene are particularly preferable from the viewpoint of improving printing density. When the monomer having a substituent containing a hetero atom is the styrene-based monomer (c-1) component, the content is preferably 10 to 100% by mass with respect to the total mass, from the viewpoint of improving the printing density. Preferably it is 20-80 mass%.

  Moreover, as a monomer which has the said aromatic group, an aromatic group containing (meth) acrylate (c-2) component is mentioned, for example. Furthermore, as the aromatic group-containing (meth) acrylate (c-2) component, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like are preferable. When the monomer having an aromatic group is an aromatic group-containing (meth) acrylate (c-2) component, the content thereof is preferably 10 to 10% from the viewpoint of improving printing density and gloss. 100% by weight, more preferably 20-80% by weight. It is also preferable to use the component (c-1) and the component (c-2) in combination.

  The monomer mixture may further contain (d) a hydroxyl group-containing monomer (hereinafter sometimes referred to as “component (d)”). By containing the component (d), the dispersion stability can be improved.

  As said (d) component, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethyleneglycol (n = 2-30, n shows the average addition mole number of an oxyalkylene group, for example. The same shall apply hereinafter.) (Meth) acrylate, polypropylene glycol (n = 2 to 30) (meth) acrylate, poly (ethylene glycol (n = 1 to 15) / propylene glycol (n = 1 to 15)) (meth) acrylate, etc. Is mentioned. Of these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferred.

The monomer mixture may further contain (e) a monomer represented by the following formula (2) (hereinafter sometimes referred to as “component (e)”). Thereby, the discharge property from an inkjet nozzle can be improved.
CH ₂ = C (R ¹ ) COO (R ² O) _q R ³ (2)
(In the formula, q represents an average added mole number of 1 to 60, preferably 1 to 30.)

R ¹ in the formula (2) represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms. Specific examples include a methyl group, an ethyl group, and an (iso) propyl group. R ² represents a C 1-30 divalent hydrocarbon group which may have a hetero atom. Specifically, oxyethylene group, oxytrimethylene group, oxypropane-1,2-diyl group, oxytetramethylene group, oxyheptamethylene group, oxyhexamethylene group, carbon number composed of a combination of two or more of these Examples thereof include 2 to 7 oxyalkanediyl groups (oxyalkylene groups). R ³ is a monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, or a phenyl group which may have an alkyl group having 1 to 9, preferably 1 to 8 carbon atoms. Represents. As the monovalent hydrocarbon group having 1 to 30 carbon atoms, specifically, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, aromatic. Examples thereof include an alkyl group having 7 to 30 carbon atoms having a ring and an alkyl group having 4 to 30 carbon atoms having a heterocyclic ring. The hetero atom is any one of a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.

  Specific examples of the component (e) include methoxypolyethylene glycol (q = 1-30) (meth) acrylate, methoxypolytetramethylene glycol (q = 1-30) (meth) acrylate, ethoxypolyethylene glycol (q = 1-30) (meth) acrylate, octoxy polyethylene glycol (q = 1-30) (meth) acrylate, polyethylene glycol (q = 1-30) (meth) acrylate 2-ethylhexyl ether, (iso) propoxy polyethylene glycol (Q = 1-30) (meth) acrylate, butoxypolyethylene glycol (q = 1-30) (meth) acrylate, methoxypolypropylene glycol (q = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol) Copolymerization) (q = 1 to 30, among which the number of ethylene glycol: q = 1 to 29) (meth) acrylate. Of these, octoxypolyethylene glycol (q = 1-30) (meth) acrylate and polyethylene glycol (q = 1-30) (meth) acrylate 2-ethylhexyl ether are preferred.

  Examples of the commercially available component (d) and component (e) include, for example, polyfunctional acrylate monomer (NK ester (registered trademark)) M-40G, 90G, and the same manufactured by Shin-Nakamura Chemical Co., Ltd. 230G, Nippon Oil & Fat Co., Ltd. Blemmer Series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400 550, 800, 50 PEP-300, 50POEP-800B, 43PAPE600B, and the like.

At the time of vinyl polymer production, the content of the components (a) to (e) in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or the components (a) to (e) The content of the structural unit is as follows.
The content of the component (a) is preferably 2 to 40% by mass, more preferably 2 to 30% by mass, and particularly preferably 3 to 20% by mass with respect to the total mass from the viewpoint of dispersion stability of the resulting dispersion. %.
The content of the component (b) is preferably 1 to 25% by mass, more preferably 5 to 20% by mass with respect to the total mass, particularly from the viewpoint of enhancing the interaction with the pigment particles.
The content of the component (c) is preferably 5 to 98% by mass and more preferably 10 to 60% by mass with respect to the total mass from the viewpoint of improving the printing density.
The content of the component (d) is preferably 5 to 40% by mass and more preferably 7 to 20% by mass with respect to the total mass from the viewpoint of dispersion stability.
The content of the component (e) is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, based on the total mass, from the viewpoint of improving dischargeability.

  The total content of [(a) component + (d) component] in the monomer mixture is preferably 6 to 60% by mass, more preferably 10%, based on the total mass, from the viewpoint of dispersion stability of the resulting dispersion. -50 mass%. The total content of [component (a) + component (e)] is preferably 6 to 75% by mass, more preferably 13 to 50% by mass, from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. . In addition, the total content of [(a) component + (d) component + (e) component] is preferably 6 to 60 mass with respect to the total mass from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. %, More preferably 7 to 50% by mass. The mass ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 to 1, more preferably from the viewpoint of dispersion stability and print density of the resulting dispersion. Is 0.02 to 0.67, more preferably 0.03 to 0.50.

  The mass ratio of the pigment particles to the polymer in the pigment ((mass of the pigment particles) / (mass of the polymer)) is 1.2 to 2.3, preferably 1.2 to 1.5. is there. By setting the mass ratio to 1.2 or more, it is possible to prevent the viscosity from becoming too large. As a result, it can be stably ejected from the inkjet nozzle, and a decrease in flight performance can be suppressed. On the other hand, by setting the mass ratio to 2.3 or less, it is possible to prevent a sufficient fixability from being secured on the recording medium due to a decrease in the polymer amount.

  The content of the pigment in the aqueous ink composition directly affects the image density, and also affects the storage stability, viscosity, pH, and the like of the aqueous ink composition. Therefore, the content of the pigment may be appropriately set in consideration of these points. Usually, the range of 1% by mass to 20% by mass in terms of solid content is preferable with respect to the total mass of the water-based ink composition, and the range of 5% by mass to 15% by mass is more preferable. By setting the pigment content to 1% by mass or more, a decrease in image density can be suppressed. On the other hand, by setting the pigment content to 20% by mass or less, it is possible to prevent a decrease in gloss, nozzle clogging, and a decrease in ejection stability.

  The polyethylene wax is preferably contained in a fine particle state (that is, an emulsion state or a suspension state) in the aqueous ink composition. By containing the polyethylene wax in a fine particle state, the viscosity of the aqueous ink composition can be easily adjusted to an appropriate range in the ink jet recording system. In addition, good storage stability and ejection stability can be maintained. As the polyethylene wax, one emulsified in water by a conventional method is used.

  Examples of the polyethylene wax include polyethylene wax, copolymer wax composed of a monomer having ethylene and a carboxylic acid group such as methacrylic acid or acrylic acid, and oxidized polyethylene wax. Moreover, as a commercial item, for example, JONCRYL (registered trademark) WAX 26J (manufactured by BASF Japan Co., Ltd.), AQUACER (registered trademark) 513 (manufactured by Big Chemie Japan Co., Ltd.), Chemipearl (registered trademark) W900, Chemipearl WF4KX12 (All manufactured by Mitsui Chemicals, Inc.), HYTEC E-6500, HYTEC E-9015, HYTEC E-1000, HYTEC E-4A (all manufactured by Toho Chemical Co., Ltd.) and the like. These can be used alone or in admixture of two or more.

  In the present embodiment, mixing other waxes such as natural waxes (for example, petroleum waxes, plant waxes, animal and plant waxes, etc.) into the water-based ink composition may be beading or the like. It may not be preferable from the viewpoint of occurrence.

  The melting point of the polyethylene wax is in the range of 120 ° C to 140 ° C, and preferably in the range of 130 ° C to 140 ° C. By using a polyethylene wax having a melting point of 120 ° C. or higher, it is possible to prevent the polyethylene wax from being thermally deformed or melted due to frictional heat generated by rubbing the surface of the printed coating film, thereby reducing the abrasion resistance. it can.

  It does not specifically limit as an average particle diameter (D50) of the said polyethylene-type wax, It can set suitably as needed. Usually, it is in the range of 30 nm to 150 nm.

  The content of the polyethylene wax is preferably in the range of 0.25% by mass to 5% by mass in terms of solid content with respect to the total mass of the water-based ink composition, and more preferably in the range of 0.25% by mass to 3% by mass. preferable. By setting the content of the polyethylene wax to 0.25% by mass or more, the slip property of the printed coating film surface can be improved, and the friction resistance can be further improved. On the other hand, the occurrence of beading can be suppressed by setting the content of the polyethylene wax to 5% by mass or less.

  The water-based ink composition of the present embodiment contains a water-soluble organic solvent as a wetting agent (anti-drying agent) from the viewpoints of promoting drying, improving ejection stability of the inkjet head, imparting moisture retention, and the like. It is preferable. As the water-soluble organic solvent, for example, a C2-C10 alkane or alkene diol, or a triol can be used. Of these water-soluble organic solvents, propylene glycol and 1,3-butanediol are preferable from the viewpoint of achieving both dryness and wettability. Moreover, these water-soluble organic solvents can be used individually or in mixture of 2 or more types.

  However, it is preferable that the water-based ink composition of the present embodiment does not substantially contain glycerin. Thereby, it can prevent that the drying property of printed matter falls. As a result, it is possible to suppress a decrease in image fixability on various recording media, particularly ink non-absorbing or low-absorbing recording media.

  It does not specifically limit as content of the said water-soluble organic solvent, It can set suitably as needed. Usually, the range of 6% by mass to 40% by mass is preferable with respect to the total mass of the aqueous ink composition, more preferably within the range of 8% by mass to 35% by mass, and particularly preferably within the range of 10% by mass to 35% by mass. preferable.

  The aqueous ink composition of the present embodiment may contain glycol ethers. Thereby, the solubility with respect to the water-based ink composition of another component can be improved. In addition, the permeability to the recording medium can be improved without causing an excessive decrease in surface tension as compared with a surfactant described later. Thereby, it is possible to record a high-definition image with little shading unevenness even on a non-absorbing or low-absorbing recording medium.

  Specific examples of the glycol ethers include, for example, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoisohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, diethylene glycol monoisohexyl ether, triethylene glycol Ethylene glycol monoisohexyl ether, ethylene glycol monoisoheptyl ether, diethylene glycol monoisoheptyl ether, triethylene glycol monoisoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monoisooctyl ether, diethylene glycol monoisooctyl ether, triethylene glycol Monoisooctyl A Ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, triethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylpentyl ether, ethylene glycol mono-2-ethylpentyl ether, ethylene glycol Mono-2-methylpentyl ether, diethylene glycol mono-2-methylpentyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol A monomethyl ether etc. are mentioned. These can be used alone or in admixture of two or more.

  The content of the glycol ethers is such that the solubility of other components in the aqueous ink composition, the wettability with respect to the recording medium, the effect of improving the penetrability to reduce density unevenness, the storage stability of the aqueous ink composition and the ejection. It can be appropriately set from the viewpoint of ensuring stability. Usually, it is preferably in the range of 0.1% by mass to 40% by mass with respect to the total mass of the aqueous ink composition. By setting the content to 0.1% by mass or more, it is possible to prevent the wettability, the permeability, and the drying property of the aqueous ink composition from being lowered, and a high-definition printed image can be obtained. In addition, the printing density (coloring property) can be ensured. On the other hand, by setting it to 40% by mass or less, the viscosity of the water-based ink composition can be prevented from becoming too high, and the occurrence of clogging of the head nozzle can be suppressed. Moreover, the solubility in a water-based ink composition can be prevented from decreasing, and storage stability can be ensured.

  Further, the water-based ink composition of the present embodiment may contain a surfactant. The image quality of the printed image and the ink drying time depend on the wettability and penetrability of the ink on the surface of the recording medium. By adding a surfactant to the aqueous ink composition, the interfacial tension at the interface between the droplet of the aqueous ink composition and the recording medium is reduced, so that the wettability and permeability of the droplet can be improved. . As a result, a high-definition image with little shading unevenness can be printed. The surfactant is not particularly limited, and examples thereof include acetylene glycol surfactants and silicone surfactants.

  The acetylene glycol-based surfactant has, for example, a property that it has excellent ability to keep the surface tension and the interfacial tension properly, and has almost no foaming property, as compared with, for example, a nonionic surfactant. Therefore, by blending the acetylene glycol surfactant into the aqueous ink composition, the surface tension and the interfacial tension with the printer member in contact with the ink such as the head nozzle surface can be properly maintained. As a result, it is possible to improve the ejection stability of droplets at the head nozzle. In addition, since the acetylene glycol surfactant exhibits good wettability with respect to the recording medium and also acts as a penetrating agent, it is possible to obtain a high-definition printed image by reducing the occurrence of uneven density and bleeding. Can do.

  The acetylene glycol surfactant is not particularly limited. For example, Surfynol (registered trademark) 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (trade names, all manufactured by Air Products and Chemicals, Inc.) and the like. These can be used alone or in admixture of two or more.

  The content of the acetylene glycol surfactant is preferably in the range of 0.2% by mass to 3% by mass, and 0.5% by mass to 2% by mass with respect to the total mass of the aqueous ink composition. It is more preferable to be within the range.

  Moreover, as said silicone type surfactant, a polysiloxane type compound etc. are used preferably, and polyether modified organosiloxane etc. are mentioned. More specifically, examples include BYK-306, 307, 333, 341, 345, 346, 348 (trade names, all manufactured by Big Chemie Japan Co., Ltd.). These can be used alone or in admixture of two or more.

  The content of the silicone surfactant is preferably in the range of 0.2% by mass to 3% by mass with respect to the total mass of the aqueous ink composition, and is 0.5% by mass to 2% by mass. More preferably within the range.

  The water-based ink composition according to this embodiment contains water (water as a main solvent). As the water, it is preferable to use water from which ionic impurities such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water have been removed. In particular, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide or the like is preferable because generation of mold and bacteria can be prevented over a long period of time. Moreover, it does not specifically limit as content of water, It can set suitably as needed.

  The water-based ink composition according to the present embodiment can omit the inclusion of a binder resin (for example, a water-dispersed urethane resin) for fixing the pigment to the surface of the recording medium. Even if it does not contain a binder resin, the water-based ink composition of this embodiment is excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance to a recording medium. As a result, the addition of an organic solvent for dissolving the binder resin in the aqueous ink composition can be omitted.

  Furthermore, the water-based ink composition of the present embodiment may further contain a pH adjuster, antiseptic / fungal agent, chelating agent, and the like as other additives. The content of these additives can be appropriately set as necessary.

  The pH adjuster is not particularly limited. For example, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, carbonic acid Potassium, sodium carbonate, sodium hydrogen carbonate, etc. are mentioned.

  The antiseptic and antifungal agent is not particularly limited, and examples thereof include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline- 3-one etc. are mentioned. By adding an antiseptic and fungicidal agent, generation of microorganisms can be suppressed and nozzle clogging can be prevented.

  The chelating agent is not particularly limited, and examples thereof include ethylenediaminetetraacetic acid and salts thereof (e.g., ethylenediaminetetraacetic acid dihydrogen disodium salt). Generation | occurrence | production of nozzle clogging etc. can be prevented by addition of a chelating agent.

(Method for producing inkjet water-based ink composition)
The water-based ink composition of the present embodiment can be produced by dispersing and mixing the above-described components by an appropriate method. That is, for example, a separately prepared polyethylene wax is added to a uniform pigment dispersion and further diluted with water, a water-soluble organic solvent, or the like. Thereafter, the mixture is sufficiently stirred, and if necessary, filtration is performed to remove coarse particles and foreign matters that cause clogging. Thereby, the water-based ink composition which concerns on this Embodiment can be obtained.

  The mixing method of each material is not particularly limited. For example, the materials are sequentially added to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and stirring and mixing are performed. Moreover, it does not specifically limit as a filtration method, For example, centrifugal filtration, filter filtration, etc. are employable.

(Inkjet recording method)
Next, the ink jet recording method of the present embodiment will be described.
The ink jet recording method of the present embodiment can be performed by discharging the aqueous ink composition as droplets onto an arbitrary recording medium from fine nozzles and attaching the droplets to the recording medium. The discharge method is not particularly limited, and for example, a known method such as continuous injection type (charge control type, spray type, etc.), on-demand type (piezo type, thermal type, electrostatic suction type, etc.) can be adopted. it can.

  The recording medium is not particularly limited, and a conventionally known recording medium can be used. The water-based ink composition of this embodiment is excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance, even on non-absorbing or low-absorbing recording media, and prints high-definition images. Because it is possible. Specific examples include general printing paper, coated paper, art paper, cardboard, paper container paper, and the like.

  After the droplets of the water-based inkjet ink composition are ejected and adhered to the recording medium, the deposited droplets are heated at a temperature lower than the melting point of the polyethylene wax contained in the water-based ink composition for inkjet. It is preferable to dry. Thereby, it can be made to exist in a printing coating film in the state which maintained the shape of particle | grains, without heat-melting or melt | dissolving a polyethylene-type wax. As a result, it is possible to print on the recording medium a print image having excellent scratch resistance, tape peeling, and scratch resistance. The heating temperature at this time means the temperature of the surface of the recording medium. The lower limit of the heating temperature can be appropriately set according to the solvent in the water-based ink composition, the type of the recording medium, the drying time, and the like. The drying time is not particularly limited, and can be appropriately set according to the solvent in the aqueous ink composition, the type of the recording medium, the printing speed, and the like.

  The method of heat drying is not particularly limited as long as it promotes evaporation of the solvent in the aqueous ink composition. For example, a method of spraying hot air on a recording medium to which droplets of the aqueous ink composition are attached, a method of bringing the recording medium into contact with a heating drum set to an appropriate temperature, and the like, are exemplified. Specifically, hot air treatment such as forced air heating, radiant heating, conduction heating, high-frequency drying, microwave drying, or heating by a heater is possible.

  In the following, preferred embodiments of the present invention will be described in detail by way of example. However, materials, contents, and the like described in the following examples are not intended to limit the scope of the present invention only to those unless otherwise specified. In the following, “%” and “part” are based on mass.

(Preparation of encapsulated pigment A)
First, a solution was prepared by dissolving 0.85 g of dimethyl 2,2′-azobisisobutyrate, 60 g of benzyl methacrylate, 10 g of methacrylic acid, and 30 g of methyl methacrylate in 50 g of methyl ethyl ketone.

  Next, 88 g of methyl ethyl ketone was added to a 1000 ml three-necked flask equipped with a stirrer and a condenser and heated to 72 ° C. in a nitrogen atmosphere, and the solution was added dropwise thereto over 3 hours. After completion of the dropwise addition, the mixture was further reacted for 1 hour, a solution of 0.42 g of dimethyl 2,2'-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess of hexane, the precipitated resin was dried, and 96 g of a polymer dispersant (benzyl methacrylate / methacrylic acid / methyl methacrylate = 60/10/30 [mass ratio]) was obtained. Obtained.

  Subsequently, C.I. I. 12 parts of Pigment Red 122, 42 parts of the polymer dispersant, 42 parts of methyl ethyl ketone, 6.3 parts of 1 mol / L NaOH aqueous solution, and 83.7 parts of ion-exchanged water were mixed and 0.1 mmφ zirconia beads were used with a bead mill. Dispersed for 2-6 hours. From the resulting dispersion, methyl ethyl ketone was removed at 55 ° C. under reduced pressure, and a part of water was further removed, whereby a dispersion of encapsulated pigment coated with a magenta pigment with the polymer dispersant (pigment concentration 12% )

(Preparation of encapsulated pigment B)
In the encapsulated pigment B, C.I. I. Preparation was performed in the same manner as for the encapsulated pigment A, except that CI Pigment Blue 15: 3 was used.

(Preparation of encapsulated pigment C)
In the encapsulated pigment C, C.I. I. Preparation was performed in the same manner as for the encapsulated pigment A, except that CI Pigment Yellow 155 was used.

(Examples 1-3)
In this example, aqueous ink compositions of Examples 1 to 3 were respectively prepared with the composition shown in Table 1 below. However, each of Examples 1 to 3 is different in that pigments and waxes of the types shown in Table 2 below are used.

  The water-based ink composition of each example was prepared by the following operation. That is, each material shown in Table 1 was put in a container and mixed, and stirred with a magnetic stirrer at room temperature for 1 hour. Thereafter, the mixed solution was filtered to remove coarse particles and foreign matters. A membrane filter having a filtration accuracy of 1 μm was used as a filter for filtration. Thereby, the water-based ink compositions of Examples 1 to 3 were obtained. The numerical values in Table 1 are all expressed in mass%. Water was added so that the total amount of the water-based ink composition was 100% by mass.

(Comparative Example 1)
In this comparative example, as shown in Tables 1 and 2, a self-dispersing pigment (trade name; Sensijet Ultra Magenta PR122, manufactured by Sensient) was used as a pigment, and no wax was blended. Otherwise, the aqueous ink composition of Comparative Example 1 was prepared in the same manner as in Example 1.

(Abrasion resistance)
Measurement and evaluation regarding scratch resistance were performed according to JIS-K5701-1. That is, using a Gakushin type friction fastness tester (manufactured by Yasuda Seiki Co., Ltd.), put the friction paper (trade name: OK Top Coat, manufactured by Oji Paper Co., Ltd.) on the coated surface of the coated paper, and apply a load of 500 g. The printed surface was rubbed 10 times. Thereafter, in order to evaluate the degree of color transfer on the friction paper, the friction surface was captured as an image with a scanner (EPSON GT-X820, manufactured by Seiko Epson Corporation). The scan conditions were 48-bit color, resolution 600 dpi, and no image correction. Furthermore, the averaging process of the image was performed using Photoshop (trademark). The averaging range was 15 mm × 15 mm.

Thereafter, in order to quantify the degree of color transfer to the friction paper, the R, G, B values of each color of cyan, magenta, and yellow on the friction paper were measured from 256 levels from 0 to 255 (hereinafter, referred to as “color”). for example, R value of color transfer portions of cyan represents a like C _R.). In addition, R, G, and B values of cyan, magenta, and yellow colors were measured for friction paper that did not rub against the printed surface of the coated paper (hereinafter, R value is, for example, Ref. _R) . .)

The method for calculating the degree of color transfer of a printed material using an ink composition containing a cyan pigment was as follows. That is, cyan can be represented by (R, G, B) = (0, 255, 255), and it can be considered that the cyan color transfer to the friction paper becomes darker as the R value approaches zero. For this reason, the degree of cyan color transfer was calculated by the following equation and digitized.
(Cyan color migration degree) = Ref. _R -C _R

Similarly, regarding the degree of color transfer of a printed material using an ink composition containing a magenta pigment, magenta can be represented by (R, G, B) = (255, 0, 255), and the G value approaches 0. Since magenta color transfer to the friction paper is considered to be deeper, the following formula was used.
(Magenta color transfer degree) = Ref. _G -M _G

Further, regarding the degree of color transfer of a printed material using an ink composition containing a yellow pigment, yellow can be represented by (R, G, B) = (255, 255, 0), and the closer the B value is to 0, Since the yellow color transfer to the friction paper is considered to be deep, it was calculated by the following formula.
(Yellow color transfer degree) = Ref. _B- Y _B

  Based on the obtained value of the color transfer degree, the scratch resistance was evaluated according to the following evaluation criteria. The results are shown in Table 2. Note that the following evaluation criteria are the same as those in the case of performing offset printing. In addition, since the sensitivity of the scratch resistance varies from color to color, the evaluation criteria for cyan pigments were changed as follows.

○: The value of the color transfer degree is 30 or less (40 or less when a cyan pigment is used)
Δ: Color transfer degree value exceeding 30 and 50 or less (when cyan pigment is used, exceeding 40 and 55 or less)
X: The value of the color transfer degree is larger than 50 (when a cyan pigment is used, it is larger than 55).

(Tape peelability)
For tape peelability, solid printing was performed on coated paper (OK ball, manufactured by Oji Paper Co., Ltd.) under the same conditions as in the evaluation of scratch resistance. Next, stick the adhesive tape (trade name: Cellotape (registered trademark) No. 405, Nichiban Co., Ltd.) to the printing surface, and then check the peeling of the printing surface and the transfer state to the tape when the adhesive tape is peeled off As a result, the tape peelability was evaluated. The evaluation criteria were as follows. The results are shown in Table 2.

○: No peeling of the recording surface / adhesion to the adhesive tape Δ: No peeling of the recording surface, but slight adhesion to the adhesive tape was observed ×: Separation occurred on the recording surface

(result)
As can be seen from Table 2, each of the water-based ink compositions according to Examples 1 to 3 has a small color transfer degree value and is excellent in scratch resistance. Moreover, peeling of the printing surface by an adhesive tape was not confirmed, but the tape peelability was also favorable.

Claims (2)

An aqueous inkjet ink composition comprising at least one pigment and a wax,
The pigment is made of a polymer containing pigment particles inside,
The mass ratio of the pigment particles to the polymer ((mass of the pigment particles) / (mass of the polymer)) is 1.2 to 2.3,
An aqueous inkjet ink composition, wherein the wax is a polyethylene wax having a melting point of 120 ° C to 140 ° C. 2. The aqueous inkjet ink composition according to claim 1, wherein the content of the polyethylene wax is in the range of 0.25 mass% to 5 mass% with respect to the total mass of the aqueous inkjet ink composition.