White ink composition and recording method

Abstract

To provide a white ink composition for inkjet printing that can form an image having excellent laminate strength and blocking resistance.SOLUTION: A white ink composition which is an aqueous inkjet ink, includes a white colorant and a fixing resin, and the fixing resin contains an acrylic-based resin having an acid value of 50.0 to 100.0 mgKOH / g and a glass transition temperature of 20.0°C to 50.0°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a white ink composition and a recording method. [Background technology]

[0002] An inkjet recording method is known in which minute ink droplets are ejected from a recording head of an inkjet recording apparatus to record an image on a recording medium. Technologies related to inkjet recording are being actively developed, and the use of inkjet recording methods in a wide range of fields is being considered.

[0003] For example, Patent Document 1 discloses an ink set that can record an image with excellent fixability and abrasion resistance on a recording medium even when a recording medium with low or no ink absorption is used. The document describes that an ink set containing two types of clear inks containing resins with different glass transition temperatures and an ink containing a coloring material can record an image with excellent abrasion resistance, adhesion, and solvent resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-183112 A Summary of the Invention [Problem to be solved by the invention]

[0005] Recorded matter is required to have a wide range of performance depending on the application. For example, in the field of printing in which recording is performed on a film, the printed matter is sometimes laminated for use. When a white ink composition is used, lamination strength is required. In addition, after printing, the recording medium may be wound into a roll, and when a white ink composition is used in particular, a show-through called blocking may occur.

[0006] With the ink set described in Patent Document 1, images with excellent abrasion resistance, adhesion, and solvent resistance can be expected to be formed, but when the colorant is white, it cannot necessarily be said that images with sufficient lamination strength and blocking resistance can be formed. [Means for solving the problem]

[0007] One embodiment of the white ink composition according to the present invention is 1. A white ink composition which is a water-based inkjet ink, comprising: Contains a white color material and a fixing resin, The fixing resin contains an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less and a glass transition temperature of 20.0° C. or more and 50.0° C. or less.

[0008] One aspect of the recording method according to the present invention is to The method further comprises a step of depositing the white ink composition onto a recording medium by an inkjet method. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a configuration of an inkjet recording apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The following describes an embodiment of the present invention. The embodiment described below is an example of the present invention. The present invention is not limited to the following embodiment, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0011] 1. White ink composition The white ink composition according to this embodiment is a water-based inkjet ink composition, and contains a white color material and a fixing resin.

[0012] 1.1.White color material Examples of the white coloring material contained in the white ink composition include metal compounds such as metal oxides, barium sulfate, and calcium carbonate. Typically, the white coloring material is an inorganic metal compound. Examples of the metal oxide include white pigments such as titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide. In addition, the white pigment may be a particle having a hollow structure, and known particles having a hollow structure may be used.

[0013] Among the above-listed white pigments, titanium dioxide is preferred from the viewpoint of good whiteness and abrasion resistance. The white pigment may be used alone or in combination of two or more kinds.

[0014] The volume-based average particle diameter (D50) of the white pigment (also referred to as "volume average particle diameter") is preferably 30.0 nm or more and 600.0 nm or less, more preferably 100.0 nm or more and 500.0 nm or less, and even more preferably 150.0 nm or more and 400.0 nm or less. If the volume average particle diameter of the white pigment is within the above range, the particles are less likely to settle, the dispersion stability can be improved, and when applied to an inkjet recording device, clogging of the nozzles can be prevented. Furthermore, if the volume average particle diameter of the white pigment is within the above range, the whiteness of the image and the background hiding property can be sufficiently expressed.

[0015] The volume average particle size of the white pigment can be measured by a particle size distribution measuring device that uses the laser diffraction scattering method as its measurement principle. Examples of the particle size distribution measuring device include a particle size distribution meter that uses the dynamic light scattering method as its measurement principle (e.g., "Microtrack UPA" manufactured by Nikkiso Co., Ltd.).

[0016] In this specification, the term "white" when referring to a white ink composition, a white coloring material, etc., does not only refer to a completely white color, but also includes chromatic or achromatic colors and glossy colors as long as they are visible as white. In addition, it includes inks and pigments that are called or sold with names that suggest that they are white inks or white pigments.

[0017] More quantitatively, "white" refers to the color of a recording that is, for example, in CIELAB, L * Not only colors with L = 100, * is between 60 and 100, and a * and b * Also included are colors whose deviations are within ±10.

[0018] More specifically, for example, when a white ink composition is used to record on a recording medium such as a transparent film, the surface of the recording medium is sufficiently covered with the ink, and the lightness (L * ) and chromaticity (a * , b * When the color of the toner is measured using a spectrophotometer conforming to CIELAB, the color is preferably within the above range. 2 More preferably, the amount of adhesion is 80≦L * ≦100, -4.5≦a * ≦2.0, -10.0≦b * ≦2.5. An example of a recording medium made of transparent film is LAG Jet E-1000ZC (manufactured by Lintec Corporation). An example of a spectrophotometer conforming to CIELAB is Spectrolino (trade name, manufactured by GretagMacbeth Co., Ltd.), and the measurement is performed under the following measurement conditions: D50 light source, observation field of view is 2°, density is DIN NB, white standard is Abs, filter is No, and measurement mode is Reflectance.

[0019] The content (solid content) of the white pigment in the white ink composition is preferably 0.5% by mass or more and 20.0% by mass or less, more preferably 1.0% by mass or more and 20.0% by mass or less, even more preferably 5.0% by mass or more and 15.0% by mass or less, and even more preferably 7.0% by mass or more and 15.0% by mass or less, based on the total mass of the white ink composition. If the content of the white pigment is within the above range, nozzle clogging of the inkjet recording device is unlikely to occur, and the color density of the white color can be fully satisfied.

[0020] The white pigment is preferably stable in water, and may be dispersed using a dispersant. The dispersant may be any of a surfactant, a resin dispersant, etc., and is selected from those that can improve the dispersion stability of the white pigment in the white ink composition. The white pigment may also be used as a self-dispersing pigment by modifying the surface of the pigment particles by oxidizing or sulfonating the pigment surface with, for example, ozone, hypochlorous acid, fuming sulfuric acid, etc.

[0021] The dispersant is used to disperse the pigment. Therefore, in the ink, the dispersant is present near the surface of the pigment, for example, adhered to the surface of the pigment. The resin dispersant is not a fixing resin, which will be described later.

[0022] Examples of the resin dispersant include (meth)acrylic resins and salts thereof, such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymer, (meth)acrylic acid-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid copolymer, and vinylnaphthalene-(meth)acrylic acid copolymer; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, styrene-α-methylstyrene-(meth)acrylic acid copolymer, and styrene-α-methylstyrene-(meth)acrylic acid copolymer. Examples of the water-soluble resins include styrene resins and salts thereof, such as styrene-based (meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, and styrene-maleic anhydride copolymers; urethane resins and salts thereof, which are polymeric compounds (resins) containing urethane bonds formed by the reaction of an isocyanate group and a hydroxyl group and may be linear and / or branched, and may have a crosslinked structure; polyvinyl alcohols; vinyl naphthalene-maleic acid copolymers and salts thereof; vinyl acetate-maleic acid ester copolymers and salts thereof; and vinyl acetate-crotonic acid copolymers and salts thereof. Among these, preferred are copolymers of a monomer having a hydrophobic functional group and a monomer having a hydrophilic functional group, and polymers made of a monomer having both a hydrophobic functional group and a hydrophilic functional group. The copolymers may be in the form of any of random copolymers, block copolymers, alternating copolymers, and graft copolymers.

[0023] Commercially available styrene-based resin dispersants include, for example, X-200, X-1, X-205, X-220, and X-228 (manufactured by Seiko PMC Corporation), Nopcosperse (registered trademark) 6100 and 6110 (manufactured by San Nopco Ltd.), Joncryl 67, 586, 611, 678, 680, 682, and 819 (manufactured by BASF), DISPERBYK-190 (manufactured by BYK Japan KK), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, and E-EN10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0024] Commercially available acrylic resin dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, and BYK-199 (manufactured by BYK-Chemie Co., Ltd.), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, and CL-2 (manufactured by Toagosei Co., Ltd.).

[0025] Further, commercially available urethane resin dispersants include BYK-182, BYK-183, BYK-184, BYK-185 (manufactured by BYK-Chemie Co., Ltd.), TEGO Disperse710 (manufactured by Evonic Tego Chemi), Borchi (registered trademark) Gen1350 (manufactured by OMG Borschers), and the like.

[0026] The dispersant may be used alone or in combination of two or more. The total content of the dispersant is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 25 parts by mass, even more preferably 1 to 20 parts by mass, and even more preferably 1.5 to 15 parts by mass, relative to 50 parts by mass of the white pigment. By making the content of the dispersant 0.1 parts by mass or more relative to 50 parts by mass of the white pigment, the dispersion stability of the white pigment can be further improved. In addition, if the content of the dispersant is 30 parts by mass or less relative to 50 parts by mass of the white pigment, the viscosity of the obtained dispersion can be kept low.

[0027] Among the above-listed dispersants, it is more preferable to use a resin dispersant, particularly at least one selected from an acrylic resin dispersant, a styrene resin dispersant, and a urethane resin dispersant. In this case, it is more preferable that the weight-average molecular weight of the dispersant is 500 or more. By using such a resin dispersant as a dispersant, odor can be suppressed and the dispersion stability of the white pigment can be further improved.

[0028] Furthermore, when a resin dispersant is used, the content of the resin dispersant can be selected appropriately depending on the type of white pigment, but is preferably 5 parts by mass or more and 200 parts by mass or less, and more preferably 20 parts by mass or more and 120 parts by mass or less, relative to 100 parts by mass of the white pigment content in the white ink composition.

[0029] 1.2. Fixing resin The white ink composition of this embodiment contains a fixing resin. The fixing resin is a resin for fixing the ink components, such as the pigment, to a recording medium, and is uniformly dispersed or dissolved in the ink solvent component.

[0030] The fixing resin includes an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less, and a glass transition temperature (Tg) of 20.0° C. or more and 50.0° C. or less. First, an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less, and a glass transition temperature (Tg) of 20.0° C. or more and 50.0° C. or less (hereinafter also referred to as a specific acrylic resin) will be described.

[0031] 1.2.1. Specific acrylic resin In this specification, the specific acrylic resin refers to an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less and a glass transition temperature (Tg) of 20.0°C or more and 50.0°C or less.

[0032] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or (meth)acrylic acid ester as one component, and examples thereof include resins obtained from acrylic monomers and copolymers of acrylic monomers and other monomers. Examples of acrylic resins include (meth)acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers such as styrene. In addition, (meth)acrylamide and (meth)acrylonitrile are also acrylic monomers, and polymers using these as monomers are also considered to be acrylic resins.

[0033] In this specification, the term "(meth)acrylic" means at least one of acrylic and methacrylic.

[0034] Styrene-acrylic resins are copolymers obtained from styrene monomers and acrylic monomers, and examples thereof include styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylate copolymers, styrene-α-methylstyrene-acrylic acid copolymers, and styrene-α-methylstyrene-acrylic acid-acrylate copolymers.

[0035] The specific acrylic resin is selected from the above-mentioned acrylic resins having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less.

[0036] The acid value of the specific acrylic resin is more preferably 55.0 mgKOH / g or more and 90.0 mgKOH / g or less, and even more preferably 60.0 mgKOH / g or more and 85.0 mgKOH / g or less. When the acid value of the specific acrylic resin is in such a range, the laminate strength of the recorded matter can be further improved.

[0037] It is presumed that when the acid value is equal to or higher than the lower limit of the above range, the laminate strength is excellent due to the acidic groups of the resin, and when the acid value is equal to or lower than the upper limit of the above range, the amount of moisture remaining in the recorded matter can be reduced, and the recorded matter can be prevented from absorbing moisture in the environment, resulting in excellent laminate strength.

[0038] Furthermore, when the acid value is equal to or higher than the lower limit of the above range, the glass transition point of the resin may become high due to the acidic groups contained in the resin, which tends to result in better blocking resistance, and is therefore preferred.

[0039] The acid value can be measured in accordance with JIS K 0070. As a titration device, for example, "AT610" manufactured by Kyoto Electronics Manufacturing Co., Ltd. can be used.

[0040] The glass transition temperature of the specific acrylic resin is from 20.0° C. to 50.0° C. The glass transition temperature is more preferably from 23.0° C. to 47.0° C., and even more preferably from 25.0° C. to 45.0° C. If the glass transition temperature of the specific acrylic resin is within this range, it is easy to impart appropriate flexibility as a fixing resin, thereby ensuring sufficient lamination strength, and preventing an excessive decrease in flexibility as a fixing resin, thereby improving the blocking resistance of the recorded matter.

[0041] The glass transition temperature (Tg) of the specific acrylic resin is measured, for example, using a differential scanning calorimeter "DSC7000" manufactured by Hitachi High-Tech Science Corporation in accordance with JIS K7121 (measurement method for glass transition temperature of plastics).

[0042] The glass transition temperature of the specific acrylic resin can be adjusted by adjusting the type and composition ratio of the monomers while paying attention to the individual Tg of each monomer used as a raw material when polymerizing the resin. This allows the range of Tg of the entire resin to be adjusted. In addition, the acid value of the resin can be adjusted within the above range by adjusting the type and composition ratio of the monomers while taking into consideration that the Tg does not deviate from the above range. In particular, the acid value can be adjusted by adjusting the composition ratio of the monomer having an acidic group.

[0043] The specific acrylic resin is preferably set to have a ratio of the vinyl monomer-derived structural unit to the entire structural units of the specific acrylic resin of 35.0% by mass or less, more preferably 30.0% by mass or less, even more preferably 25.0% by mass or less, and particularly preferably 20.0% by mass or less. In this case, the acid value and glass transition point of the resin are easily adjusted to the above range. In this way, the lamination strength and blocking resistance of the image formed on the low-absorption recording medium or non-absorption recording medium are easily improved. On the other hand, the lower limit of the ratio of the vinyl monomer-derived structural unit to the entire structural units of the specific acrylic resin is preferably 0.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 20.0% by mass or more. It is preferable that the ratio of the vinyl monomer-derived structural unit to the entire structural units of the specific acrylic resin is 10.0% by mass or more, as this makes it easier to obtain the above-mentioned effect.

[0044] The vinyl monomer is not particularly limited as long as it is a compound having a vinyl group, and examples thereof include styrene-based monomers, amine-based vinyl monomers, vinyl monomers having an anionic group (carboxyl group, sulfonic acid group, phosphoric acid group), etc. Specific examples of the vinyl monomer include styrene, 2-methylstyrene, vinyltoluene, ethylvinylbenzene, vinylnaphthalene, chlorostyrene, vinylpyridine, 2-methyl-5-vinylpyridine, 2-ethyl-5-vinylpyridine, N,N-dimethylaminostyrene, N,N-dimethylaminomethylstyrene, styrenesulfonic acid, vinylphosphonic acid, vinylphosphate, etc.

[0045] In addition, the specific acrylic resin is preferably 40.0% by mass or less of the constituent units derived from aromatic (meth)acrylate or alicyclic (meth)acrylate, more preferably 35.0% by mass or less, even more preferably 30.0% by mass or less, particularly preferably 20.0% by mass or less, and more particularly preferably 10% by mass or less, based on the total constituent units of the specific acrylic resin. In this way, the lamination strength and blocking resistance of the image formed on the low-absorption recording medium or non-absorption recording medium can be improved. On the other hand, the lower limit of the ratio of the constituent units derived from aromatic (meth)acrylate or alicyclic (meth)acrylate to the total constituent units of the specific acrylic resin is preferably 0.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 20.0% by mass or more. The ratio of the constituent units derived from aromatic (meth)acrylate or alicyclic (meth)acrylate to the total constituent units of the specific acrylic resin is preferably within the above range, which makes it easier to obtain the above effects, and is therefore preferred. Furthermore, when the proportion of structural units derived from an aromatic (meth)acrylate or an alicyclic (meth)acrylate is within the above range, the acid value and glass transition point of the resin can be easily adjusted to fall within the above range, which is preferable.

[0046] Examples of the aromatic (meth)acrylate include aryl (meth)acrylate esters such as phenyl (meth)acrylate, o-tolyl (meth)acrylate, m-tolyl (meth)acrylate, p-tolyl (meth)acrylate, 2,3-xylyl (meth)acrylate, 2,4-xylyl (meth)acrylate, 2,5-xylyl (meth)acrylate, 2,6-xylyl (meth)acrylate, 3,4-xylyl (meth)acrylate, 3,5-xylyl (meth)acrylate, 1-naphthyl (meth)acrylate, 2-naphthyl (meth)acrylate, binaphthyl (meth)acrylate, and anthryl (meth)acrylate; aralkyl (meth)acrylate esters such as benzyl (meth)acrylate; and phenoxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate.

[0047] Examples of alicyclic (meth)acrylates include cycloalkyl (meth)acrylates such as cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate; and (meth)acrylates having a bicyclo ring such as isobornyl (meth)acrylate.

[0048] Furthermore, the specific acrylic resin preferably has a ratio of the long-chain aliphatic (meth)acrylate-derived structural unit to the entire structural unit of the specific acrylic resin of 30.0% by mass or more, more preferably 35.0% by mass or more, and even more preferably 40.0% by mass or more. In this way, the laminate strength of the image formed on the low-absorption recording medium or non-absorption recording medium is easily improved. On the other hand, the upper limit of the ratio of the long-chain aliphatic (meth)acrylate-derived structural unit to the entire structural unit of the specific acrylic resin is preferably 50.0% by mass or less, more preferably 45.0% by mass or less, and even more preferably 40.0% by mass or less. The ratio of the long-chain aliphatic (meth)acrylate-derived structural unit to the entire structural unit of the specific acrylic resin is 50.0% by mass or less, which is preferable because it is easy to obtain the above-mentioned effect.

[0049] Furthermore, when the proportion of the structural units derived from long-chain aliphatic (meth)acrylate is within the above range, the acid value and glass transition point of the resin can be easily adjusted to fall within the above range, which is preferable.

[0050] Here, the long-chain aliphatic (meth)acrylate is a (meth)acrylate having a linear or branched chain hydrocarbon group, and the chain hydrocarbon group has 5 or more carbon atoms. The number of carbon atoms is preferably 6 or more, and more preferably 7 or more. There is no upper limit, but it is preferably 30 or less, more preferably 25 or less, and more preferably 20 or less.

[0051] For example, among (meth)acrylic acid alkyl esters, those in which the alkyl group has 5 or more carbon atoms can be mentioned. More specifically, examples of long-chain aliphatic (meth)acrylates include (meth)acrylic acid n-pentyl ester, (meth)acrylic acid isopentyl ester, (meth)acrylic acid n-hexyl ester, (meth)acrylic acid isohexyl ester, (meth)acrylic acid n-heptyl ester, (meth)acrylic acid isoheptyl ester, (meth)acrylic acid n-octyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid decyl ester, (meth)acrylic acid dodecyl ester, (meth)acrylic acid pentadecyl ester, (meth)acrylic acid hexadecyl ester, (meth)acrylic acid heptadecyl ester, (meth)acrylic acid octadecyl ester, and the like.

[0052] The specific acrylic resin may be dissolved in the white ink composition, or may be dispersed in the form of resin particles. When the specific acrylic resin is dispersed in the form of resin particles, the volume average particle diameter of the resin particles is preferably 20 nm or more. Also, it is preferably 300 nm or less. It is further preferably 50 nm or more and 300 nm or less, more preferably 100 nm or more and 200 nm or less, and even more preferably 100 nm or more and 150 nm or less.

[0053] The content of the specific acrylic resin in the white ink composition is preferably 1.0% by mass or more and 15.0% by mass or less, more preferably 5.0% by mass or more and 15.0% by mass or less, and even more preferably 8.0% by mass or more and 12.0% by mass or less, based on the total amount of the composition. When the content of the specific acrylic resin is within such a range, a recorded matter including a white image having better lamination strength and blocking resistance can be formed by the white ink composition.

[0054] 1.2.2. Other acrylic resins The white ink composition of this embodiment may contain, as a fixing resin, an acrylic resin other than the specific acrylic resin. That is, the white ink composition may contain, as a fixing resin, an acrylic resin having an acid value of less than 50.0 mgKOH / g or more than 100.0 mgKOH / g, or a glass transition temperature (Tg) of less than 20.0° C. or more than 50.0° C. Hereinafter, such an acrylic resin will be referred to as "other acrylic resin."

[0055] Other acrylic resins include, for example, Joncryl 62J, 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631 , 790, 780, 7610 (trade names, manufactured by BASF), 952B, 718A, Mowinyl 966A, 975N (trade names, manufactured by Japan Coating Resins), Vinyblan 2586 (manufactured by Nissin Chemical Industry Co., Ltd.), FK-854 (trade name, manufactured by Japan Coating Resins), Nipol LX852, LX874 (trade names, manufactured by Zeon Corporation), and the like.

[0056] 1.2.3.Other fixing resins The white ink composition may contain other resins as fixing resins in addition to the above-mentioned acrylic resin.

[0057] Examples of resins that can be used as the fixing resin include water-soluble resins such as polyvinyl alcohol, carboxymethyl cellulose, and water-soluble polyesters, which are soluble in the white ink composition.

[0058] Furthermore, examples of resins that can be used as fixing resins include resins that disperse as resin particles in the white ink composition, such as resin particles made of urethane-based resins, fluorene-based resins, polyolefin-based resins, rosin-modified resins, terpene-based resins, polyester-based resins, polyamide-based resins, epoxy-based resins, vinyl chloride-based resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate-based resins, etc. These resin particles are often handled in the form of an emulsion, but may also be in the form of a powder.

[0059] When a resin other than the specific acrylic resin is contained as a fixing resin in the white ink composition, the content is 0.1% by mass to 10.0% by mass, preferably 0.5% by mass to 5.0% by mass, and more preferably 1.0% by mass to 3.0% by mass, in terms of solid content, relative to the total mass of the white ink composition. The content of the resin other than the specific acrylic resin is designed within a range that does not inhibit the function of the specific acrylic resin.

[0060] The resin other than the specific acrylic resin that can be contained in the white ink composition can be used alone or in combination of two or more. Furthermore, the resin other than the specific acrylic resin may be used in combination of one that disperses as resin particles in the white ink composition and one that dissolves.

[0061] 1.3.Other Ingredients The white ink composition may contain organic solvents, water, a surface tension adjuster, wax, a pH adjuster, a mildew inhibitor, a preservative, and other additives.

[0062] Organic Solvents The white ink composition may contain an organic solvent. One of the functions of the organic solvent is to improve the wettability of the white ink composition to the recording medium and to increase the moisture retention of the white ink composition. When the organic solvent is contained, the ink can have moisture retention and excellent clogging resistance, and the ink can have excellent drying properties, so that the organic solvent remaining in the recorded matter can be reduced and the recorded matter can have excellent fastness. In addition, the surface tension of the ink can be reduced, so that when the ink is discharged from the inkjet recording head, the ink can be easily separated from the nozzle and flown as droplets, and the wettability on the recording medium can be improved to provide excellent spreading of the ink droplets.

[0063] Examples of the organic solvent include esters, alkylene glycol ethers, cyclic esters, nitrogen-containing solvents, polyhydric alcohols, and alcohol-based solvents. Examples of the nitrogen-containing solvent include cyclic amides and non-cyclic amides. Examples of the non-cyclic amides include alkoxyalkylamides.

[0064] Examples of esters include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, Examples of the glycol diesters include glycol monoacetates such as propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and methoxybutyl acetate; and glycol diesters such as ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, diethylene glycol acetate butyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, dipropylene glycol acetate butyrate, and dipropylene glycol acetate propionate.

[0065] Examples of the cyclic esters include cyclic esters (lactones) such as β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, β-butyrolactone, β-valerolactone, γ-valerolactone, β-hexanolactone, γ-hexanolactone, δ-hexanolactone, β-heptanolactone, γ-heptanolactone, δ-heptanolactone, ε-heptanolactone, γ-octanolactone, δ-octanolactone, ε-octanolactone, δ-nonalactone, ε-nonalactone, and ε-decanolactone, as well as compounds in which the hydrogen of the methylene group adjacent to the carbonyl group is substituted with an alkyl group having 1 to 4 carbon atoms.

[0066] Examples of the nitrogen-containing solvent include non-cyclic amides, cyclic amides, etc. Examples of the non-cyclic amides include alkoxyalkyl amides.

[0067] Examples of the alkoxyalkylamides include 3-methoxy-N,N-dimethylpropionamide, 3-methoxy-N,N-diethylpropionamide, 3-methoxy-N,N-methylethylpropionamide, 3-ethoxy-N,N-dimethylpropionamide, 3-ethoxy-N,N-diethylpropionamide, 3-ethoxy-N,N-methylethylpropionamide, 3-n-butoxy-N,N-dimethylpropionamide, 3-n-butoxy-N,N-diethylpropionamide, 3-n-butoxy-N,N-methylethylpropionamide, 3-n-propoxy-N, Examples of the propionamide include N-dimethylpropionamide, 3-n-propoxy-N,N-diethylpropionamide, 3-n-propoxy-N,N-methylethylpropionamide, 3-iso-propoxy-N,N-dimethylpropionamide, 3-iso-propoxy-N,N-diethylpropionamide, 3-iso-propoxy-N,N-methylethylpropionamide, 3-tert-butoxy-N,N-dimethylpropionamide, 3-tert-butoxy-N,N-diethylpropionamide, and 3-tert-butoxy-N,N-methylethylpropionamide.

[0068] As the non-cyclic amides, it is also preferable to use alkoxyalkylamides, which are compounds represented by the following general formula (1).

[0069] R 1 -O-CH 2 CH 2 -(C=O)-NR 2 R 3 (1)

[0070] In the above formula (1), R 1 represents an alkyl group having 1 to 4 carbon atoms, and R 2 and R 3each independently represents a methyl group or an ethyl group. The "alkyl group having 1 to 4 carbon atoms" can be a linear or branched alkyl group, for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, or a tert-butyl group. The compound represented by the above formula (1) may be used alone or in combination of two or more kinds.

[0071] Examples of the cyclic amides include lactams, such as pyrrolidones such as 2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, and 1-(2-hydroxyethyl)-2-pyrrolidone. These are preferred in terms of promoting the formation of a film on the polymer particles described below, and 1-(2-hydroxyethyl)-2-pyrrolidone is particularly preferred.

[0072] The alkylene glycol ethers may be monoethers or diethers of alkylene glycol, and alkyl ethers are preferred. Specific examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, and propylene glycol monomethyl ether. and alkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol methyl butyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and tripropylene glycol dimethyl ether.

[0073] When a glycol ether is used, the number of carbon atoms is preferably 12 or less, more preferably 8 or less, and even more preferably 6 or less. The lower limit is preferably 2 or more, more preferably 3 or more, and even more preferably 5 or more. The number of carbon atoms is the number of carbon atoms in the molecule.

[0074] When such glycol ether is used, a recorded matter including a white image having better blocking resistance is easily formed. The glycol portion of the glycol ether may be an alkylene glycol in which hydroxyl groups are condensed between molecules. The number of condensations of the alkylene glycol is preferably 2 to 4, more preferably 2 to 3. The ether portion of the glycol ether is preferably an alkyl ether, more preferably an alkyl having 1 to 4 carbon atoms, more preferably an alkyl having 2 to 4 carbon atoms.

[0075] Alkylene glycol ethers are preferred because they have excellent permeability and excellent wettability of the ink on a recording medium, resulting in excellent image quality. In this respect, monoethers are particularly preferred.

[0076] When the ink contains a nitrogen-containing solvent and / or glycol ethers having 8 or less carbon atoms, the ink has excellent resin film formation, and is more preferable in terms of excellent adhesion, lamination strength, blocking resistance, etc. The content of the nitrogen-containing solvent and / or glycol ethers having 8 or less carbon atoms in the ink is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. Also, it is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. It is also preferable that the content of the nitrogen-containing solvent in the ink is within the above range. It is also preferable that the content of the glycol ethers having 8 or less carbon atoms in the ink is within the above range.

[0077] Examples of polyhydric alcohols include 1,2-alkanediols (e.g., alkanediols such as ethylene glycol, propylene glycol (also known as propane-1,2-diol), 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol), and polyhydric alcohols (polyols) other than 1,2-alkanediols (e.g., diethylene glycol, dipropylene glycol, 1,3-propanediol, and 1,3-butanediol (also known as 1,3-butylene glycol). , 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, trimethylolpropane, glycerin, etc.

[0078] Polyhydric alcohols can be divided into alkanediols and polyols.

[0079] The alkanediols are diols of an alkane having 5 or more carbon atoms. The number of carbon atoms of the alkane is preferably 5 or more and 15 or less, more preferably 6 or more and 10 or less, and even more preferably 6 or more and 8 or less. 1,2-alkanediol is particularly preferred.

[0080] The polyols are polyols of alkanes having 4 or less carbon atoms, or intermolecular condensation products of hydroxyl groups of polyols of alkanes having 4 or less carbon atoms. The number of carbon atoms of the alkane is preferably 2 to 3. The number of hydroxyl groups in the molecule of the polyols is 2 or more, preferably 5 or less, and more preferably 3 or less. When the polyols are the intermolecular condensation products, the number of intermolecular condensations is 2 or more, preferably 4 or less, and more preferably 3 or less. The polyhydric alcohols can be used alone or in combination of two or more.

[0081] Alkanediols and polyols can function primarily as penetrating solvents and / or moisturizing solvents, but alkanediols tend to have stronger penetrating solvent properties, while polyols tend to have stronger moisturizing solvent properties.

[0082] Alkanediols are preferred because they have strong penetrating solvent properties and excellent wettability of the ink on the recording medium, leading to excellent ink spread and excellent image quality.

[0083] Polyols are particularly hydrophilic, can particularly enhance moisture retention, and are particularly excellent in clogging resistance. In particular, by using polyols having a normal boiling point of 280.0° C. or less, drying is also good and the fastness of the recorded matter is easily improved.

[0084] Examples of alcohol-based solvents include methanol, ethanol, isopropanol, 1-propanol, 1-butanol, 2-butanol, 3-pentanol, 2-methyl-1-butanol, 2-methyl-2-butanol, isoamyl alcohol, 3-methyl-2-butanol, 3-methoxy-3-methyl-1-butanol, 4-methyl-2-pentanol, allyl alcohol, 1-hexanol, 1-heptanol, 2-heptanol, and 3-heptanol.

[0085] The white ink composition may use one of the organic solvents exemplified above alone or in combination of two or more. When two or more organic solvents are used, the content of the organic solvents is the total content of the organic solvents.

[0086] When the white ink composition contains an organic solvent, the total content is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total amount of the ink. It is preferably 13.0% by mass or less, more preferably 10.0% by mass or less, even more preferably 7.0% by mass or less, particularly preferably 6.0% by mass or less, and more particularly preferably 5.0% by mass or less. In this case, it is preferable in that the fastness of the recorded matter is more excellent. On the other hand, the lower limit is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 5.0% by mass or more, and particularly more preferably 6.0% by mass or more. Furthermore, it is preferably 10% by mass or more, and more preferably 20% by mass or more. This is preferable in that clogging resistance and image quality are superior.

[0087] The content of polyols having a normal boiling point of more than 280° C. in the ink preferably does not exceed 2.0% by mass, more preferably does not exceed 1.0% by mass, and even more preferably does not exceed 0.5% by mass. The lower limit is 0.0% by mass.

[0088] It is also preferable to set the content of the organic solvent in the ink having a normal boiling point of more than 280° C. within the above range. In this case, adhesion, lamination strength, blocking resistance, etc. are more excellent, which is preferable.

[0089] 1.3.2.Water The white ink composition may contain water. When the white ink composition is an aqueous composition, it contains water as one of the main solvent components. In this case, water is contained as the main solvent component and is a component that evaporates and scatters when dried. The water is preferably pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, etc., from which ionic impurities have been removed as much as possible. In addition, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., since it can suppress the generation of mold and bacteria when the white ink composition is stored for a long period of time. When water is contained in the white ink composition to form an aqueous composition, the content of water is preferably 50% by mass or more, more preferably 70.0% by mass or more, particularly 75.0% by mass or more, more preferably 80.0% by mass or more and 98% by mass or less, and even more preferably 85.0% by mass or more and 95.0% by mass or less, based on the total amount of the white ink composition.

[0090] 1.3.3.Surface tension modifier The white ink composition may contain a surface tension modifier. The surface tension modifier has a function of reducing the surface tension of the white ink composition and improving wettability with a recording medium or a base. Among surface tension modifiers, acetylene glycol-based surface tension modifiers, silicone-based surface tension modifiers, and fluorine-based surface tension modifiers can be preferably used.

[0091] The acetylene glycol-based surface tension adjuster is not particularly limited, but examples thereof include Surfynol 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, and DF110D (all trade names, manufactured by Air Products & Chemicals, Inc.). ), Olfin B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, EXP.4001, EXP.4036, EXP.4051, AF-103, AF-104, AK-02, SK-14, AE-3 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.), Acetylenol E00, E00P, E40, E100 (all trade names, manufactured by Kawaken Fine Chemical Co., Ltd.).

[0092] The silicone surface tension regulator is not particularly limited, but preferably includes a polysiloxane compound, and the polysiloxane compound is not particularly limited, but for example, includes a polyether-modified organosiloxane. Commercially available polyether-modified organosiloxanes include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, and BYK-348 (all trade names, manufactured by BYK Japan), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0093] As the fluorine-based surface tension adjuster, it is preferable to use a fluorine-modified polymer, and specific examples include BYK-3440 (manufactured by BYK Japan), Surflon S-241, S-242, S-243 (all trade names, manufactured by AGC Seimi Chemical Co., Ltd.), and Futergent 215M (manufactured by NEOS Co., Ltd.).

[0094] When the white ink composition contains a surface tension modifier, multiple types may be contained. When the white ink composition contains a surface tension modifier, the content of the surface tension modifier is preferably 0.1% by mass or more and 2.0% by mass or less, more preferably 0.2% by mass or more and 1.5% by mass or less, and even more preferably 0.3% by mass or more and 1.0% by mass or less, based on the total mass.

[0095] The compounds exemplified here as surface tension modifiers are not considered to be the above-mentioned organic solvents.

[0096] Wax The white ink composition may contain a wax. The wax has a function of imparting lubricity to an image formed by the white ink composition, and therefore can reduce peeling of the image formed by the white ink composition.

[0097] Examples of components constituting the wax include vegetable and animal waxes such as carnauba wax, candelilla wax, beeswax, rice wax, and lanolin; petroleum waxes such as paraffin wax, microcrystalline wax, polyethylene wax, oxidized polyethylene wax, and petrolatum; mineral waxes such as montan wax and ozokerite; synthetic waxes such as carbon wax, Hoechst wax, polyolefin wax, and stearic acid amide; natural and synthetic wax emulsions and blended waxes such as α-olefin-maleic anhydride copolymers, etc., which can be used alone or in combination. Among these, polyolefin waxes (particularly polyethylene wax and polypropylene wax) and paraffin wax are preferred from the viewpoint of their excellent effect of increasing the fixation to the soft packaging film described below.

[0098] As the wax, commercially available products can be used as they are, and examples thereof include Nopcoat PEM-17 (product name, manufactured by San Nopco Ltd.), Chemipearl W4005 (product name, manufactured by Mitsui Chemicals Inc.), BYK AQUACER 515, 539, and 593 (all product names, manufactured by BYK Japan KK).

[0099] The melting point of the wax is preferably 50.0°C or higher and 200.0°C or lower, more preferably 70.0°C or higher and 180.0°C or lower, and even more preferably 90.0°C or higher and 150.0°C or lower.

[0100] The wax may be supplied in the form of an emulsion or suspension. When using wax, the content is 0.1% by mass or more and 10.0% by mass or less, more preferably 0.5% by mass or more and 5.0% by mass or less, and even more preferably 0.5% by mass or more and 2.0% by mass or less, calculated as solid content, based on the total mass of the white ink composition. When the wax content is within the above range, it is easy to impart lubricity to an image, for example.

[0101] 1.3.5. pH Adjusters The white ink composition of the present embodiment may contain a pH adjuster. By containing a pH adjuster, for example, it is possible to suppress or promote the elution of impurities from the members forming the ink flow path of the recording device, and to adjust the cleaning properties of the white ink composition. Examples of pH adjusters include ureas, amines, morpholines, piperazines, and amino alcohols such as triethanolamine. Examples of ureas include urea, ethylene urea, tetramethyl urea, thiourea, 1,3-dimethyl-2-imidazolidinone, and betaines (trimethylglycine, triethylglycine, tripropylglycine, triisopropylglycine, N,N,N-trimethylalanine, N,N,N-triethylalanine, N,N,N-triisopropylalanine, N,N,N-trimethylmethylalanine, carnitine, acetylcarnitine, and the like). Examples of amines include diethanolamine, triethanolamine, and triisopropanolamine.

[0102] The compounds exemplified here as pH adjusters are not considered to be the above-mentioned organic solvents. For example, triethanolamine is a liquid at room temperature with a normal boiling point of about 208°C, but is not considered to be the above-mentioned organic solvent.

[0103] 1.3.6. Antifungal agents and preservatives The white ink composition of this embodiment may contain a preservative. By containing a preservative, the growth of mold and bacteria can be inhibited, and the storage stability of the ink composition is improved. This makes it easier to use the white ink composition as a maintenance liquid when maintaining a recording device without using it for a long period of time. Preferred examples of the preservative include Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel IB, and Proxel TN (manufactured by Lonza Japan Co., Ltd.).

[0104] 1.3.7. Other Additives The white ink composition may contain various additives, such as a chelating agent, an antirust agent, an antifungal agent, an antioxidant, an antireducing agent, and an evaporation promoter, as necessary.

[0105] Examples of the chelating agent include ethylenediaminetetraacetate (EDTA), ethylenediamine nitrilotriacetate, hexametaphosphate, pyrophosphate, and metaphosphate.

[0106] 1.4. Method for producing white ink composition The method for producing the white ink composition of this embodiment is not particularly limited, but the ink composition can be produced, for example, by mixing the ink components described above in any order and removing impurities by filtration, etc., as necessary. As a method for mixing the components, a method in which the materials are added sequentially to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and then stirred and mixed is preferably used.

[0107] 1.5. Physical properties of white ink composition From the viewpoint of the balance between image quality and reliability as an ink for inkjet recording, the white ink composition according to this embodiment preferably has a surface tension of 20 mN / m to 40 mN / m, and more preferably 20 mN / m to 35 mN / m, at 20° C. The surface tension can be measured, for example, by using an automatic surface tensiometer CBVP-Z (product name, manufactured by Kyowa Interface Science Co., Ltd.) to confirm the surface tension when a platinum plate is wetted with the ink in an environment of 20° C.

[0108] From the same viewpoint, the viscosity of the white ink composition according to this embodiment at 20° C. is preferably from 1.0 mPa·s to 20.0 mPa·s, and more preferably from 3.0 mPa·s to 15.0 mPa·s. The viscosity can be measured at 20° C. using, for example, a viscoelasticity tester MCR-300 (product name, manufactured by Pysica).

[0109] 1.6. Uses of the White Ink Composition The white ink composition of the present embodiment can form a white image when applied to a recording medium. The recording medium to which the white ink composition is applied is not particularly limited, but includes an absorbent recording medium, and a low-absorbent or non-absorbent recording medium, and a low-absorbent or non-absorbent recording medium is preferred. Examples of the absorbent recording medium include absorbent paper and cloth.

[0110] A low-absorbency or non-absorbency recording medium refers to a recording medium that does not absorb ink at all or absorbs very little ink. Quantitatively, a low-absorbency recording medium is one that is "capable of absorbing ink for 30 msec from the start of contact in the Bristow method." 1 / 2 Water absorption up to 10mL / m 2This refers to a recording medium that is "any of the following types:" The Bristow method is the most widely used method for measuring the amount of liquid absorbed in a short period of time, and is also adopted by the Japan Pulp and Paper Technical Association (JAPAN TAPPI). Details of the test method are described in Standard No. 51 "Paper and paperboard - Liquid absorbency test method - Bristow method" of the "JAPAN TAPPI Paper and Pulp Testing Methods 2000 Edition." Recording media with this type of low absorbency property include recording media that do not have an ink receiving layer on the recording surface, and recording media that have a coating layer with low ink absorbency on the recording surface.

[0111] The white ink composition of the present embodiment is effective for low-absorbency recording media. Examples of low-absorbency recording media include, but are not limited to, coated paper having a coating layer on the surface for receiving oil-based ink. Examples of coated paper include, but are not limited to, printing paper such as art paper, coated paper, and matte paper.

[0112] In addition, the non-absorbent recording medium is not particularly limited, but examples thereof include a plastic film having no ink receiving layer, a substrate such as paper coated with plastic, or a substrate having a plastic film adhered thereto. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyolefin, nylon, etc. Examples of polyolefins include polyethylene and polypropylene. Polyolefins are preferable because they provide excellent film flexibility, but on the other hand, they are difficult to fix to ink. However, the white ink composition of this embodiment provides good fastness.

[0113] In particular, when the recording medium is made of any of polyethylene terephthalate, polyolefin, and nylon, blocking resistance and lamination strength are particularly required, and this embodiment is useful.

[0114] By using the white ink composition of this embodiment, it is possible to form a predetermined image with good fixability and good abrasion resistance at high speed even on such a non-ink-absorbing or low-ink-absorbing recording medium. In addition, such recording media tend to be difficult to absorb the solvent component of the ink, and the organic solvent remaining on the recording medium tends to pose problems in terms of robustness, such as abrasion resistance and fixability, of the recorded matter. However, by using the white ink composition of this embodiment, excellent robustness can be obtained, which is preferable.

[0115] The recording medium may be in the form of a bag or a sheet. In the inkjet recording method according to the present embodiment, it is more preferable that the recording medium to which the ink is to be attached is mainly composed of polyolefin (polyethylene, polypropylene, etc.). Such a recording medium is generally difficult to adhere to, and since an image with good fixability and abrasion resistance can be formed on the recording medium, the effect of good fixability and abrasion resistance is even more remarkable. The recording medium may be subjected to a surface treatment such as a corona treatment or a primer treatment in advance, and such a surface treatment may improve the releasability of the ink from the recording medium.

[0116] Furthermore, when the white ink composition of this embodiment is applied to a recording medium to form a recorded matter, at least the recorded surface of the recorded matter may be subjected to a lamination treatment before use. When a recorded matter recorded using the white ink composition of this embodiment is subjected to a lamination treatment on at least the recorded surface, the laminate strength can be improved.

[0117] The white ink composition of this embodiment can form a recorded matter including a white image having good lamination strength and blocking resistance. That is, the white ink composition contains a fixing resin having an acid value in a specific range, thereby providing good lamination strength, and contains a fixing resin having a glass transition temperature in a specific range, thereby providing a recorded matter having good blocking resistance.

[0118] 1.7.Ink set In this embodiment, an ink set may be provided that includes a white ink composition and a non-white ink composition. In an ink set, the inks included in the ink set are used as a set for recording. In other words, two or more inks used as a set for recording are called an ink set.

[0119] The inks in the ink set may each be contained in an individual ink container. Examples of the ink container include a pack, a bottle, a vial, etc. The inks may also be in the form of a cartridge that can be installed in a printer.

[0120] 2. Recording method The recording method according to this embodiment includes a step of depositing the above-described white ink composition onto a recording medium by an inkjet method.

[0121] In the process of applying the white ink composition to a recording medium by the inkjet method, ink droplets (liquid droplets) of the white ink composition are applied to the recording medium from the inkjet head of a printer. At this time, the ink droplets are intermittently ejected at a predetermined timing and with a predetermined mass to apply the ink droplets to the recording medium, thereby forming (recording) a desired image, character, pattern, color, or other design. This makes it possible to obtain a recorded matter containing a white image with good lamination strength and blocking resistance.

[0122] The white ink composition can be applied by the inkjet method using either a serial type recording device equipped with a serial type inkjet head or a line type recording device equipped with a line type inkjet head.

[0123] The recording method of the present embodiment may include a non-white ink applying step of ejecting a non-white ink composition containing a non-white coloring material from an inkjet head and applying the ink onto a recording medium. In addition, for example, a treatment liquid application step of ejecting a treatment liquid composition from an inkjet head and adhering it to a recording medium, or a clear ink application step of ejecting a clear ink composition that does not contain a coloring material from an inkjet head and adhering it to a recording medium may be provided.

[0124] In addition, the method may include a primary drying process in which ink is applied to a heated recording medium, a secondary drying process in which the recording medium is heated after the ink is applied, a lamination process described below, etc., and these processes may be performed multiple times.

[0125] In addition, in the recording method of this embodiment, when a transparent plastic film is used as the recording medium, a non-white ink composition may be applied on the white image after the white ink composition is applied to the recording medium, so that the white image functions as a base layer (background concealing layer) when viewed from the recording surface side of the recording medium. Furthermore, in the recording method of this embodiment, when a transparent plastic film is used as the recording medium, a non-white ink composition may be applied on the non-white image after the non-white ink composition is applied to the recording medium, so that the white image functions as a base layer (background concealing layer) when viewed from the opposite side to the recording surface of the recording medium.

[0126] The lamination process can be carried out by laminating a protective film on the recording surface of the recording medium to which at least the white ink composition is attached, for example by laminating the film. In addition, although not particularly limited, a known adhesive may be attached to the recording surface of the recording material, and a film may be laminated thereon, or a film to which an adhesive is attached may be laminated to the recording surface of the recording material. Furthermore, the lamination process can be carried out by using a molten resin obtained by melting the film to extrude the molten resin onto the recording surface of the recording material, and forming it into a film on the recording surface of the recording material.

[0127] As a material for the film used for lamination, for example, a resin film can be used. Note that in this embodiment, the recording medium to which the white ink composition is attached may be used as a recorded matter as it is without being laminated after recording.

[0128] 3. Recording device FIG. 1 is a schematic cross-sectional view showing the configuration of an example of an inkjet recording apparatus that can be used in the recording method of the present invention. As shown in FIG. 1, the inkjet recording apparatus 1 includes an inkjet head 2, an IR heater 3, a platen and a platen heater 4, a heating heater 5, a cooling fan 6, a preheater 7, and a blower fan 8. The overall operation of the inkjet recording apparatus 1 is controlled by a control unit CONT (not shown). The example of the recording apparatus in FIG. 1 is an example of a line printer, and recording is performed by discharging ink from the inkjet head 2 while the recording medium 10 is conveyed in the conveyance direction X. Primary drying is performed by the platen heater 4, the preheater 7, the blower fan 8, the IR heater 3, etc., and secondary drying is performed by the heating heater 5.

[0129] 4. Examples and Comparative Examples Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" are based on mass unless otherwise specified. The evaluation was performed under an environment of a temperature of 25.0°C and a relative humidity of 40.0% unless otherwise specified.

[0130] 4.1. Preparation of Fixing Resin The fixing resin examples (R1 to R35) shown in Tables 1 to 3 were prepared as follows. Tables 1 to 3 describe the monomer species and their amounts used in each example.

[0131] <Preparation of R1> After purging the reaction vessel equipped with a stirring motor, stirring blades, a temperature sensor, and a reflux cooling pipe with nitrogen, 500 g of methyl ethyl ketone (hereinafter also referred to as "MEK") was charged, and the internal temperature was raised to 77 °C while stirring. A total of 500 g of monomers were added in the mass ratios shown in the table. That is, 60 g of methacrylic acid (hereinafter also referred to as "MA"), 315 g of 2-ethylhexyl methacrylate (hereinafter also referred to as "2-EHMA"), and 125 g of styrene (hereinafter also referred to as "St"). Further, 8 g of ditertiary butyl peroxide (hereinafter also referred to as "per-D") was added. These were added dropwise over 4 hours. After completion of the dropwise addition, the mixture was kept at an internal temperature of 77 °C for 1 hour, the reflux cooling pipe was replaced with a distillation pipe, and the residual monomers and solvent in the system were removed under normal pressure and appropriately reduced pressure until the internal temperature reached 100 °C. Thereafter, it was cooled to room temperature to obtain resin R1.

[0132] The acid value of resin R1 was measured based on JIS standards and was 78 mgKOH / g. The weight average molecular weight was 17,000, and the glass transition temperature was 30 °C. These values are shown in the table.

[0133] <Preparation of R2 to R34> In the example of R1 above, resins R2 to R34 were adjusted in the same manner except that the total amount of the monomers was fixed at 500 g and the mass ratios of the respective monomers were made the ratios in the table. In all cases, the molecular weights were almost the same as that of R1. The acid values and glass transition temperatures are shown in the table.

[0134] The resins obtained as R1 to R34 were mixed with water at room temperature, neutralized with a base such as sodium hydroxide, potassium hydroxide, or ammonia to adjust the pH, and stirred to obtain a resin dispersion in which the resin was dispersed in water. For R35, the resin was prepared in the same manner as R1, and in the step of dispersing in water, the average particle diameter was adjusted by stirring while heating or increasing the stirring time.

[0135] Also, Tables 1 to 3 show the volume average particle diameter of the resin particles, and the amounts of styrene, aromatic and alicyclic acrylates, and long-chain aliphatic acrylates in the monomer composition.

[0136] [Table 1]

[0137] [Table 2]

[0138] [Table 3]

[0139] 4.2. Preparation of Ink Composition Each component was placed in a container so as to obtain the composition shown in Tables 4 to 6, and mixed and stirred with a magnetic stirrer for 2 hours, and then filtered using a 5.0 μm PTFE membrane filter to obtain each of the white ink compositions (W1 to W48) and non-white ink compositions (C1, C2). The values ​​in Tables 4 to 6 indicate mass %. Ultrapure water was used, and was added so that the mass of each ink composition was 100 mass %.

[0140] [Table 4]

[0141] [Table 5]

[0142] [Table 6]

[0143] The components other than those listed by compound name in Tables 4 to 6 are as follows. · White pigment dispersion: Metal oxide dispersion CI Pigment White 6 (metal oxide content: 20 mass%, anionic dispersion resin content: 2 mass%) The contents in the table are listed as solids concentration. · PB15:3: Organic pigment dispersion CI Pigment Blue 15:3, (pigment content: 15 mass%, anionic dispersion resin content: 3.75 mass%) The contents in the table are listed as solids concentration. Fixing resin dispersion: Resin dispersions shown in Tables 1 to 3. The contents in the tables are shown as solid content concentrations. BYK AQUACER515: Wax (manufactured by BYK Japan Co., Ltd.) BYK-348: Silicone surface tension modifier (manufactured by BYK Japan Co., Ltd.) Proxel XL2: Antifungal and preservative (manufactured by Lonza Japan Co., Ltd.)

[0144] Evaluation method 4.3.1. Recording test A Seiko Epson L-4355A (inkjet printer) was modified to become a line printer. In each of the examples shown in Tables 7 to 9, recording was carried out as follows using the compositions shown in the same tables.

[0145] The recording head was fixed in position during recording, and a mechanism for one-pass printing was used to continuously transport the recording medium. During recording, the platen heater was operated, and the surface temperature of the recording medium on the recording side at a position opposite the recording head (maximum temperature during recording) was set to 45°C. A line head was formed by staggering multiple recording heads in the width direction of the recording medium. The recording medium was dried at a temperature of 80°C (maximum temperature) by a secondary drying mechanism downstream of the recording head. One recording head (nozzle row) had 360 nozzles, and the nozzle density was 360 dpi. The recording pattern was a rectangular pattern of 20 cm x 20 cm, and the adhesion amount of the composition was the value shown in Tables 7 to 9. The following recording media were used. OPP: Toyobo Pylen P2102, made of polypropylene PET: Espet E5100 manufactured by Toyobo Co., Ltd. Nylon: Harden N1100 manufactured by Toyobo Co., Ltd.

[0146] 4.3.2. Evaluation of adhesion A cross-cut peel test was carried out on the solid parts of the printed image using a cloth adhesive tape (123LW-50, manufactured by Nichiban Co., Ltd.), and the results were evaluated according to the following criteria. A: No peeling is observed in any of the 100 squares. B: 1 to 10 of the 100 squares are peeled off C: 11 to 30 of the 100 squares are peeled off D: 31 or more of the 100 squares are peeled off

[0147] 4.3.3. Evaluation of laminate strength A dry lamination adhesive (base agent TM-329 / hardener CAT-8B, manufactured by Toyo-Morton Co., Ltd.) was applied to the solid image area on the OPP using a bar coater, and a non-oriented polypropylene film (CPP) film (product name: Pylen P1128, manufactured by Toyobo Co., Ltd.) was laminated, and then aged at 40°C for 48 hours. The laminate was cut to a width of 15 mm and strength was measured using a T-type peel test (testing machine: A&D Tensilon universal testing machine RTG-1250A), and the "lamination strength" was evaluated based on the following evaluation criteria. The results are shown in Tables 7 to 9. A: Achieve a strength of 5N / 15mm or more B: A strength of 3N / 15mm or more and less than 5N / 15mm is obtained. C: A strength of 1N / 15mm or more and less than 3N / 15mm is obtained. D: Only a strength of less than 1N / 15mm can be achieved

[0148] A dry lamination adhesive (main agent TM-569 / hardener CAT-10L, manufactured by Toyo-Morton Co., Ltd.) was applied to the solid image area on the PET using a bar coater, and a polyethylene film (LLDPE) film (product name: Rix L6102, manufactured by Toyobo Co., Ltd.) was laminated, and then aged at 40°C for 48 hours. The laminate was cut to a width of 15 mm and strength was measured using a T-type peel test (testing machine: A&D Tensilon universal testing machine RTG-1250A), and the "lamination strength" was evaluated based on the following evaluation criteria. The results are shown in Tables 7 to 9. A: Achieve a strength of 7N / 15mm or more B: A strength of 5N / 15mm or more and less than 7N / 15mm is obtained. C: A strength of 3N / 15mm or more and less than 5N / 15mm is obtained. D: Only a strength of less than 3N / 15mm can be achieved

[0149] A dry lamination adhesive (main agent TM-569 / hardener CAT-10L, manufactured by Toyo-Morton Co., Ltd.) was applied to the solid image area on the nylon using a bar coater, and a polyethylene film (LLDPE) film (product name: Rix L6102, manufactured by Toyobo Co., Ltd.) was laminated, and then aged at 40°C for 72 hours. The laminate was cut to a width of 15 mm and strength was measured using a T-type peel test (testing machine: A&D Tensilon universal testing machine RTG-1250A), and the "lamination strength" was evaluated based on the following evaluation criteria. The results are shown in Tables 7 to 9. A: Achieves a strength of 7N / 15mm or more B: A strength of 5N / 15mm or more and less than 7N / 15mm is obtained. C: A strength of 3N / 15mm or more and less than 5N / 15mm is obtained. D: Only a strength of less than 3N / 15mm can be achieved

[0150] 4.3.4. Evaluation of blocking and show-through The solid image area on one film was placed on the non-printed side (non-corona treated side) of the other film, and the film was subjected to a blocking test with a pressure of 5 kgf / cm using a blocking tester (Tester Sangyo Co., Ltd. CO-201 permanent deformation tester). 2 A load was applied to each film and the film was left at 40° C. for 24 hours. When the film was not peeled off, the degree of image transfer was considered and the "blocking property" was evaluated according to the following evaluation criteria. The results are shown in Tables 7 to 9. A: The image is not transferred. B: There is some tackiness, but it does not affect the image. C: Part of the image is transferred D: 50 percent or more of the image area is transferred

[0151] A PET film (Espet E5100 manufactured by Toyobo Co., Ltd.) and a nylon film (Harden N1100 manufactured by Toyobo Co., Ltd.) were also evaluated in the same manner.

[0152] [Table 7]

[0153] [Table 8]

[0154] [Table 9]

[0155] 4.4.Evaluation Results In each of the Examples using a white ink composition containing an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less and a glass transition temperature of 20.0°C or more and 50.0°C or less, the lamination strength and blocking resistance were excellent.

[0156] On the other hand, the comparative examples that did not have this characteristic were all inferior in either the laminate strength or the blocking resistance. Although not shown in the table, in Example 1, after the white ink was applied, a non-white ink was applied on top of the white ink layer in the same manner as in Reference Example 1, and the results were evaluated in the same manner. The results showed that the adhesion, lamination strength, and blocking resistance were excellent.

[0157] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments.

[0158] The following can be derived from the above-described embodiment and modified examples.

[0159] One embodiment of the white ink composition is 1. A white ink composition which is a water-based inkjet ink, comprising: Contains a white color material and a fixing resin, The fixing resin contains an acrylic resin having an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less and a glass transition temperature of 20.0° C. or more and 50.0° C. or less.

[0160] This white ink composition can form a recorded matter including a white image having good lamination strength and blocking resistance. That is, the white ink composition contains a fixing resin having an acid value in the above range, thereby providing good lamination strength, and contains a fixing resin having a glass transition temperature in the above range, thereby providing a recorded matter having good blocking resistance.

[0161] In the white ink composition, The acrylic resin may be in the form of particles, and the particles may have a volume average particle size of 100.0 nm or more and 150.0 nm or less.

[0162] This white ink composition makes it possible to form a recorded matter including a white image having a better balance between lamination strength and blocking resistance.

[0163] In the white ink composition, The content of the acrylic resin may be 1.0% by mass or more and 15.0% by mass or less with respect to the total amount of the composition.

[0164] This white ink composition makes it possible to form a recorded matter including a white image having better lamination strength and blocking resistance.

[0165] In the white ink composition, The proportion of constituent units derived from vinyl monomers relative to all constituent units of the acrylic resin may be 35.0% by mass or less.

[0166] This white ink composition makes it possible to form a recorded matter including a white image having better lamination strength and blocking resistance.

[0167] In the white ink composition, The proportion of structural units derived from an aromatic (meth)acrylate or an alicyclic (meth)acrylate with respect to all structural units of the acrylic resin may be 40.0% by mass or less.

[0168] This white ink composition makes it possible to form a recorded matter including a white image having better lamination strength and blocking resistance.

[0169] In the white ink composition, The proportion of the structural units derived from long-chain aliphatic (meth)acrylate with respect to all structural units of the acrylic resin may be 30.0% by mass or more.

[0170] This white ink composition makes it possible to form a recorded matter including a white image having better lamination strength.

[0171] In the white ink composition, The content of the white color material may be 5.0% by mass or more and 20.0% by mass or less with respect to the total amount of the composition.

[0172] This white ink composition makes it possible to form a recorded matter including a white image having better color development and background hiding properties.

[0173] In the white ink composition, It may contain a nitrogen-containing solvent or a glycol ether solvent having 8 or less carbon atoms.

[0174] This white ink composition makes it possible to form a recorded matter including a white image having better blocking resistance.

[0175] In the white ink composition, The recorded matter obtained by using the white ink composition may be used after a lamination treatment is applied to the recorded surface.

[0176] This white ink composition makes it possible to form a recorded matter including a white image having excellent lamination strength.

[0177] In the white ink composition, It may be used for recording on low absorbent or non-absorbent recording media.

[0178] This white ink composition makes it possible to form a recorded matter using a low-absorbency recording medium or a non-absorbency recording medium, including a white image having better lamination strength and blocking resistance.

[0179] The recording method includes a step of depositing any one of the above white ink compositions onto a recording medium by an inkjet method.

[0180] According to this recording method, a recorded matter including a white image having better lamination strength and blocking resistance can be formed. [Explanation of symbols]

[0181] 1... inkjet recording device, 2... inkjet head, 3... IR heater, 4... platen and platen heater, 5... heater, 6... cooling fan, 7... pre-heater, 8... blower fan, 10... recording medium, X... conveyance direction

Claims

1. 1. A white ink composition which is a water-based inkjet ink, comprising: Contains a white color material and a fixing resin, The fixing resin has an acid value of 50.0 mgKOH / g or more and 100.0 mgKOH / g or less. The glass transition temperature of the acrylic resin is 35.0° C. or more and 50.0° C. or less. The acrylic resin is in the form of particles, and the volume average particle diameter of the particles is 100.0 n m or more, The acrylic resin is a copolymer of vinyl monomers other than acrylic monomers with respect to the entire structural units. The proportion of structural units derived from mer is 13.0% by mass or less, It is used for recording on a recording medium that is a low-absorbency recording medium or a non-absorbency recording medium. the law of nature, The recording medium may be polyethylene terephthalate, polyolefin, or nylon. A white ink used for recording on two or more types of recording media containing polyolefin. composition.

2. In claim 1, The acrylic resin is in the form of particles, and the volume average particle diameter of the particles is 100.0 nm. or more and 150.0 nm or less.

3. In claim 1 or 2, The content of the acrylic resin is 1.0 mass% or more and 15.0 mass% or less based on the total amount of the composition. % or less.

4. In any one of claims 1 to 3, The fixing resin has an acid value of 50.0 mgKOH / g or more and 98 mgKOH / g or less. White ink composition.

5. In any one of claims 1 to 4, The aromatic (meth)acrylate or alicyclic (meth)acrylate based on the total structural units of the acrylic resin A white ink having a ratio of structural units derived from (meth)acrylate of 40.0% by mass or less. composition.

6. In any one of claims 1 to 5, The ratio of the long-chain aliphatic (meth)acrylate-derived units to the total structural units of the acrylic resin is The white ink composition according to claim 1, wherein the proportion of a structural unit represented by the formula (I) is 30.0% by mass or more.

7. In any one of claims 1 to 6, The content of the white coloring material is 5.0% by mass or more and 20.0% by mass or less based on the total amount of the composition. The white ink composition.

8. In any one of claims 1 to 6, A white ink composition containing a nitrogen-containing solvent or a glycol ether solvent having 8 or less carbon atoms. 。

9. In any one of claims 1 to 8, The recorded matter obtained by using the white ink composition is used after laminating the recorded surface. A white ink composition.

10. In any one of claims 1 to 9, The white ink composition, wherein the recording medium is a non-absorbent recording medium.

11. The white ink composition according to any one of claims 1 to 10 is ink-jet printed. The method includes a step of attaching the recording medium, which is a low-absorbency recording medium or a non-absorbency recording medium, by a method. A recording method that allows you to

Images